SGSN Administration Guide, StarOS Release 20

SGSN Administration Guide, StarOS Release 20
SGSN Administration Guide, StarOS Release 20
First Published: March 31, 2016
Last Modified: August 08, 2016
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CONTENTS
Preface
About this Guide xxxiii
Conventions Used xxxiii
Supported Documents and Resources xxxiv
Related Common Documentation xxxiv
Related Product Documentation xxxv
Obtaining Documentation xxxv
Contacting Customer Support xxxv
CHAPTER 1
Serving GPRS Support Node (SGSN) Overview 1
Product Description 1
Qualified Platforms 2
Licenses 2
Network Deployments and Interfaces 3
SGSN and Dual Access SGSN Deployments 3
SGSN/GGSN Deployments 5
S4-SGSN Deployments 5
SGSN Logical Network Interfaces 7
SGSN Core Functionality 10
All-IP Network (AIPN) 10
SS7 Support 11
PDP Context Support 11
Mobility Management 12
GPRS Attach 12
GPRS Detach 12
Paging 13
Service Request 13
Authentication 13
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P-TMSI Reallocation 14
P-TMSI Signature Reallocation 14
Identity Request 14
Location Management 14
Session Management 15
PDP Context Activation 15
PDP Context Modification 16
PDP Context Deactivation 16
PDP Context Preservation 16
Charging 16
SGSN in GPRS/UMTS Network 16
Charging Data Records (CDRs) 17
SGSN Call Detail Records (S-CDRs) 17
Mobility Call Detail Records (M-CDRs) 17
Short Message Service CDRs 17
Location Request CDRs 17
SGSN in LTE/SAE Network 18
Serving Gateway Call Detail Records (S-GW-CDRs) 18
Features and Functionality 18
3G-2G Location Change Reporting 18
Accounting Path Framework, New for 14.0 18
AAA Changes To Support Location Services (LCS) Feature 19
APN Aliasing 19
Default APN 19
APN Redirection per APN with Lowest Context-ID 20
APN Resolution with SCHAR or RNC-ID 20
APN Restriction 20
Automatic Protection Switching (APS) 21
Authentications and Reallocations -- Selective 22
Avoiding PDP Context Deactivations 22
Backup and Recovery of Key KPI Statistics 22
Bulk Statistics Support 23
Bypassing APN Remap for Specific IMEI Ranges 24
CAMEL Service Phase 3, Ge Interface 24
CAMEL Service 24
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CAMEL Support 24
Ge Interface 25
CAMEL Configuration 25
Commandguard 26
Configurable RAB Asymmetry Indicator in RAB Assignment Request 26
Congestion Control 26
Different NRIs for Pooled and Non-pooled RNCs/BSCs 27
Direct Tunnel 27
Direct Tunnel Support on the S4-SGSN 27
Downlink Data Lockout Timer 28
DSCP Templates for Control and Data Packets - Iu or Gb over IP 28
Dual PDP Addresses for Gn/Gp 28
ECMP over ATM 28
EDR Enhancements 29
EIR Selection for Roaming Subscribers 29
Equivalent PLMN 29
First Vector Configurable Start for MS Authentication 30
Format Encoding of MNC and MCC in DNS Queries Enhanced 30
Gb Manager 30
GMM-SM Event Logging 31
Gn/Gp Delay Monitoring 31
GTP-C Path Failure Detection and Management 31
GTPv0 Fallback, Disabling to Reduce Signalling 32
Handling Multiple MS Attaches All with the Same Random TLLI 32
HSPA Fallback 32
Ignore Context-ID during 4G/3G Handovers 33
Interface Selection Based on UE Capability 33
Intra- or Inter-SGSN Serving Radio Network Subsystem (SRNS) Relocation (3G only) 33
Lawful Intercept 34
Lawful Interception Capacity Enhanced 34
Link Aggregation - Horizontal 34
Local DNS 34
Local Mapping of MBR 35
Local QoS Capping 35
Location Change Reporting on the S4-SGSN 35
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Location Services 36
Lock/Shutdown the BSC from the SGSN 36
Multiple PLMN Support 37
Network Sharing 37
Benefits of Network Sharing 37
GWCN Configuration 38
MOCN Configuration 39
Implementation 39
NRI-FQDN based DNS resolution for non-local RAIs (2G subscribers) 40
NRI Handling Enhancement 40
NRPCA - 3G 40
NRSPCA Support for S4-SGSN 40
Operator Policy 41
Some Features Managed by Operator Policies 41
Overcharging Protection 42
QoS Traffic Policing per Subscriber 42
QoS Classes 42
QoS Negotiation 42
DSCP Marking 42
Traffic Policing 43
VPC-DI platform support for SGSN 43
Reordering of SNDCP N-PDU Segments 44
RAN Information Management (RIM) 44
S4 Support on the SGSN 44
S3 and S4 Interface Support 45
S4-SGSN Support for "Higher Bit Rates than 16 Mbps"Flag 45
S6d and Gr Interface Support 46
Configurable Pacing of PDP Deactivations on the S4-SGSN 47
DNS SNAPTR Support 47
S4-SGSN Statistics Support 47
S13' Interface Support 48
Idle Mode Signaling Reduction 48
ISR with Circuit Switched Fallback 48
ISD / DSD Message Handling and HSS Initiated Bearer Modification 49
UMTS-GSM AKA Support on the S4-SGSN 50
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3G and 2G SGSN Routing Area Update 50
2G and 3G Intra RAU with and without S-GW Relocation 51
2G and 3G Inter-SGSN and Inter SGSN-MME RAU with and without S-GW Relocation
Across S16 and S3 Interfaces 51
Intra-SGSN Inter-RAT RAU with and without S-GW Relocation 51
IPv4 and IPv6 PDP Type Override 51
NAPTR-based Dynamic HSS Discovery 51
P-GW Initiated PDP Bearer Deactivation 52
S-GW and P-GW Tunnel and EPS Subscription Recovery 52
Local Configuration of S-GW and S4-SGSN per RAI 52
Configurable GUTI to RAI Conversion Mapping 53
S4-SGSN Support for Fallback to V1 Cause Code in GTPv2 Context Response 53
S4-SGSN Support for Mobility Management Procedures 53
QoS Mapping Support 54
MS Initiated Primary and Secondary Activation 54
Deactivation Procedure Support 54
MS, PGW and HSS Initiated PDP Modification Procedure Support 54
MS-Initiated PDP Context Modification 55
P-GW-Initiated PDP Context Modification 55
HSS Initiated PDP Context Modification 55
Fallback from the S4 Interface to the Gn Interface 56
Operator Policy Selection of S4 or Gn Interface 56
IDFT Support During Connected Mode Handovers 56
Disassociated DSR Support 57
SGSN Serving Radio Network Subsystem (SRNS) Relocation Support 57
Configuration and Maintenance 58
E-UTRAN Service Handover Support 58
Support for Gn Handoff from S4-SGSN to 2G/3G Gn SGSN 59
Suspend/Resume Support on the S4-SGSN 59
Flex Pooling (Iu / Gb over S16) Support on the S4-SGSN 59
LORC Subscriber Overcharging Protection on S4-SGSN 60
Summary of Functional Differences between an S4-SGSN and an SGSN (Gn/Gp) 60
Session Recovery 69
SGSN Pooling and Iu-Flex / Gb-Flex 70
Gb/Iu Flex Offloading 70
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SGSN Supports Enhanced IMSI Range 70
SGSN Support for RAI Based Query 71
SGSN Support For Sending Extended Bits Bi-directionally 71
SGSN support to Ignore PDP Data Inactivity 71
Short Message Service (SMS over Gd) 72
SMS Authentication Repetition Rate 72
SMSC Address Denial 72
Status Updates to RNC 72
Target Access Restricted for the Subscriber Cause Code 73
Topology-based Gateway (GW) Selection 73
Threshold Crossing Alerts (TCA) Support 74
Tracking Usage of GEA Encryption Algorithms 75
Validation of MCC/MNC Values in the Old RAI Field 75
VLR Pooling via the Gs Interface 75
Synchronization of Crash Events and Minicores between Management Cards 76
Zero Volume S-CDR Suppression 76
How the SGSN Works 77
First-Time GPRS Attach 77
PDP Context Activation Procedures 79
Network-Initiated PDP Context Activation Process 80
MS-Initiated Detach Procedure 81
Supported Standards 82
IETF Requests for Comments (RFCs) 82
3GPP Standards 83
ITU Standards 89
Object Management Group (OMG) Standards 89
CHAPTER 2
SGSN in a 2.5G GPRS Network 91
SGSN in a 2.5G GPRS Network 91
2.5G SGSN Configuration Components 92
The SGSN_Ctx 92
The Accounting_Ctx 94
How the 2.5G SGSN Works 94
For GPRS and/or IMSI Attach 95
For PDP Activation 96
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Information Required for the 2.5G SGSN 97
Global Configuration 97
SGSN Context Configuration 99
Accounting Context Configuration 100
CHAPTER 3
SGSN 3G UMTS Configuration 103
SGSN 3G UMTS Configuration 103
3G SGSN Configuration Components 104
For GPRS and/or IMSI Attach 105
Information Required for 3G Configuration 106
Global Configuration 106
SGSN Context Configuration 109
Accounting Context Configuration 111
CHAPTER 4
SGSN Service Configuration Procedures 113
SGSN Service Configuration Procedures 114
2.5G SGSN Service Configuration 114
3G SGSN Service Configuration 116
Dual Access SGSN Service Configuration 117
Configuring the S4-SGSN 118
Configuring an SS7 Routing Domain 120
Configuring an SS7 Routing Domain to Support Broadband SS7 Signaling 121
Example Configuration 121
Configuring an SS7 Routing Domain to Support IP Signaling for SIGTRAN 122
Example Configuration 122
Configuring GTT 123
Example Configuration 123
Configuring an SCCP Network 124
Example Configuration 124
Configuring a MAP Service 125
Example Configuration 125
Configuring an IuPS Service (3G only) 126
Example Configuration 126
Configuring an SGTP Service 126
Example Configuration 127
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Configuring a Gs Service 127
Example Configuration 128
Configuring an SGSN Service (3G only) 128
Example Configuration 129
Configuring a GPRS Service (2.5G only) 129
Example Configuration 130
Configuring a Network Service Entity 130
Configure a Network Service Entity for IP 130
Example Configuration for a Network Service Entity for IP 131
Configure a Network Service Entity for Frame Relay 131
Example Configuration for a Network Service Entity for IP 131
Configuring DNS Client 132
Example Configuration 132
Configuring GTPP Accounting Support 132
Creating GTPP Group 133
Configuring GTPP Group 133
Verifying GTPP Group Configuration 134
Configuring and Associating the EGTP Service (S4 Only) 135
Example Configuration 136
Configuring and Associating the GTPU Service (S4 Only) 136
Example Configuration 136
Configuring the DNS Client Context for APN and SGW Resolution (Optional) 137
Example Configuration 138
Configuring the S6d Diameter Interface (S4 Only) 138
Configuring the Diameter Endpoint for the S6d Interface 139
Example Configuration 139
Configuring the HSS Peer Service and Interface Association for the S6d Interface 140
Example Configuration 140
Associating the HSS Peer Service with the SGSN and GPRS Services for the S6d
Interface 141
Example Configuration 141
Configuring Operator Policy-Based S6d Interface Selection (Optional) 141
Example Configuration 142
Configuring the Subscription Interface Preference for the S6d Interface (Optional) 142
Example Configuration 142
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Configuring the S13' Interface (S4 Only, Optional) 143
Configuring a Diameter Endpoint for the S13' Interface 144
Example Configuration 144
Configuring the HSS Peer Service and Interface Association for the S13' Interface 145
Example Configuration 145
Associating the HSS Peer Service with the SGSN and GPRS Services for the S13' Interface 146
Example Configuration 146
Configuring S13' Interface Selection Based on an Operator Policy 146
Example Configuration 147
Configuring QoS Mapping for EPC-Capable UEs using the S4 Interface (S4 Only, Optional) 147
Example Configuration 148
Configuring the Peer SGSN Interface Type (S4 Only, Optional) 148
Example Configuration 149
Configuring Gn Interface Selection Based on an Operator Policy (S4 Only, Optional) 149
Example Configuration 149
Configuring a Custom MME Group ID (S4 Only, Optional) 150
Example Configuration 150
Configuring and Associating the Selection of an SGW for RAI (S4 Only, Optional) 151
Example Configuration 152
Configuring a Local PGW Address (S4 Only, Optional) 152
Example Configuration 152
Configuring the Peer MME Address (S4 Only, Optional) 153
Example Configuration 153
Configuring the ISR Feature (S4 Only, Optional) 154
Example Configuration 154
Configuring IDFT for Connected Mode Handover (S4 Only, Optional) 155
Example Configuration 156
Creating and Configuring ATM Interfaces and Ports (3G only) 156
Creating and Configuring Frame Relay Ports (2.5G only) 156
Configuring APS/MSP Redundancy 157
Example Configuration 157
CHAPTER 5
3G-2G Location Change Reporting 159
Feature Description 159
Relationships 159
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License 160
Standards Compliance 160
How it Works 160
Call Flows 161
Configuring Location Change Reporting 162
Verifying the Location Change Reporting Configuration 163
CHAPTER 6
APN-OI-Replacement for Gn-SGSN 165
Feature Description 165
How It Works 166
Monitoring and Troubleshooting 168
CHAPTER 7
APN Restriction 171
Feature Description 171
Relationships to Other Features 171
How it Works 172
Limitations 173
Standards Compliance 174
Configuring APN Restriction 174
Verifying the APN Restriction Configuration 174
Monitoring and Troubleshooting the APN Restriction 175
CHAPTER 8
Attach Rate Throttling 177
Feature Description 177
How it Works 178
Attach Rate Throttling Feature 178
Limitations 180
Configuring the Attach Rate Throttling Feature 180
Monitoring and Troubleshooting the Attach Rate Throttling Feature 180
Attach Rate Throttling Show Commands and Outputs 180
CHAPTER 9
Backup and Recovery of Key KPI Statistics 183
Feature Description 183
How It Works 183
Architecture 184
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Limitations 185
Configuring Backup Statistics Feature 186
Configuration 186
Verifying the Backup Statistics Feature Configuration 187
Managing Backed-up Statistics 187
CHAPTER 10
Cause Code #66 189
Feature Description 189
How It Works 190
Standards Compliance 190
Configuring PDP Activation Restriction and Cause Code Values 190
Configuring PDP Activation Restriction 191
Configuring SM Cause Code Mapping for SGSN 191
Configuring ESM Cause Code Mapping for ESM Procedures (for MME) 191
Configuring EMM and ESM Cause Code Mapping for EMM Procedures (for MME) 192
Configuring ESM Cause Code Mapping for ESM Procedures (MME Service Configuration
Mode) 193
Configuring EMM and ESM Cause Code Mapping for EMM Procedures (MME Service
Configuration Mode) 193
Verifying the Feature Configuration 194
Monitoring and Troubleshooting the Cause Code Configuration 195
Show Command(s) and/or Outputs 195
show gmm-sm statistics verbose 195
Bulk Statistics 196
CHAPTER 11
Cause Code Mapping 197
Cause Code Mapping 197
Feature Description 197
Configuring Cause Code Mapping 198
Configuring GMM Cause Codes to Replace MAP Cause Codes 198
Verifying Configuration to Replace MAP Cause Codes 199
Configuring GMM Cause Code for RAU Reject due to Context Transfer Failure 199
Verifying Configuration for Context Transfer Failures 199
Configuring SM Cause Codes 199
Verifying Configuration for SM Cause Codes 200
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CHAPTER 12
Direct Tunnel for 3G Networks 201
Direct Tunnel Feature Overview 201
Direct Tunnel Configuration 205
Configuring Direct Tunnel Support on the SGSN 205
Enabling Setup of GTP-U Direct Tunnels 206
Enabling Direct Tunnel per APN 207
Enabling Direct Tunnel per IMEI 207
Enabling Direct Tunnel to Specific RNCs 208
Restricting Direct Tunnels 208
Verifying the SGSN Direct Tunnel Configuration 209
Verifying the Operator Policy Configuration 209
Verifying the Call-Control Profile Configuration 209
Verifying the APN Profile Configuration 210
Verifying the IMEI Profile Configuration 210
Verifying the RNC Configuration 210
CHAPTER 13
Direct Tunnel for 4G (LTE) Networks 211
Direct Tunnel for 4G Networks - Feature Description 211
How It Works 214
DT Establishment Logic 215
Establishment of Direct Tunnel 216
Direct Tunnel Activation for Primary PDP Context 217
Direct Tunnel Activation for UE Initiated Secondary PDP Context 217
RAB Release with Direct Tunnel 218
Iu Release with Direct Tunnel 219
Service Request with Direct Tunnel 220
Downlink Data Notification with Direct Tunnel when UE in Connected State 221
Downlink Data Notification with Direct Tunnel when UE in Idle State 222
Intra SGSN Routing Area Update without SGW Change 224
Routing Area Update with S-GW Change 227
Intra SRNS with S-GW Change 230
Intra SRNS without S-GW Change 232
New SRNS with S-GW Change and Direct Data Transfer 233
New SRNS with S-GW Change and Indirect Data Transfer 235
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Old SRNS with Direct Data Transfer 237
Old SRNS with Indirect Data Transfer 238
Network Initiated Secondary PDP Context Activation 240
PGW Init Modification when UE is Idle 240
Limitations 241
Standards Compliance 242
Configuring Support for Direct Tunnel 242
Configuring Direct Tunnel on an S4-SGSN 242
Enabling Setup of GTP-U Direct Tunnel 242
Enabling Direct Tunnel to RNCs 243
Restricting Direct Tunnels 244
Verifying the Call-Control Profile Configuration 244
Verifying the RNC Configuration 244
Configuring S12 Direct Tunnel Support on the S-GW 245
Monitoring and Troubleshooting Direct Tunnel 245
show subscribers sgsn-only 245
show gmm-sm statistics sm-only 246
Direct Tunnel Bulk Statistics 246
CHAPTER 14
GMM-SM Event Logging 247
Feature Description 247
Feature Overview 247
Events to be Logged 248
Event Record Fields 248
EDR Storage 252
Architecture 252
Limitations 253
Configuration 253
CHAPTER 15
GTPU Error Indication Enhancement 255
Feature Description 255
CHAPTER 16
Identity Procedure on Authentication Failure 257
Feature Description 257
Authentication Failures 257
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Identity Procedure 258
How It Works 258
GSM Authentication Unacceptable 259
MAC Failure in 2G 259
Configuring Performance of Identity Procedure 259
Verifying the Configuration 260
Monitoring and Troubleshooting the Performance of Identity Procedure for Authentication
Failure 260
show gmm-sm statistics verbose 260
show gmm-sm statistics 260
CHAPTER 17
Idle Mode Signalling Reduction on the S4-SGSN 261
Feature Description 261
Relationships 262
How ISR Works 262
Limitations 264
Call Flows 264
2G ISR Activation by the S4-SGSN 264
2G ISR Activation by the MME 266
Standards Compliance 267
Configuring Idle-Mode-Signaling Reduction 268
Configuring 2G ISR 268
Verifying the 2G ISR Configuration 268
Configuring 3G ISR 269
Verifying the 3G ISR Configuration 269
Monitoring and Troubleshooting the ISR Feature 270
ISR Show Command(s) and Outputs 270
show subscribers gprs-only full 270
show subscribers sgsn-only full 270
show s4-sgsn statistics (2G ISR) 270
show s4-sgsn statistics (3G ISR) 271
show gmm statistics (2G ISR) 271
show gmm statistics (3G ISR) 271
CHAPTER 18
IMSI Manager Broadcast Control 273
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Feature Description 273
How It Works 274
Configuring IMSI Manager Broadcast Control 275
Monitoring and Troubleshooting IMSI Manager Broadcast Control 275
Show Command(s) and/or Outputs 275
show demuxmgr statistics imsimgr all 275
CHAPTER 19
IMSI Manager Overload Control 277
Feature Description 277
Monitoring and Troubleshooting IMSI Manager Overload Control 278
Show Command(s) and/or Outputs 278
show demuxmgr statistics imsimgr all 278
CHAPTER 20
ISR with Circuit Switched Fallback 279
ISR with CSFB - Feature Description 279
Call Flows 280
Relationships to Other Features 282
Relationships to Other Products 282
How it Works 283
ISR CSFB Procedures 284
Standards Compliance 287
Configuring ISR with Circuit Switched Fallback 288
Monitoring and trouble-shooting the CSFB feature 288
CHAPTER 21
Location Services 289
Location Services - Feature Description 289
How Location Services Works 289
Relationship to Other SGSN Functions 290
Architecture 290
Limitations 291
Flows 291
Flows 291
Standards Compliance 293
Configuring Location Services (LCS) on the SGSN 294
Enabling LCS 294
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Identifying the GMLC 295
Configuring Exclusion of GMLC Address from Update-GPRS-Location Messages 295
Creating the Location Service Configuration 296
Fine-tuning the Location Service Configuration 296
Associating the Location Service Config with the SGSN 297
Associating the Location Service Config with an Operator Policy 297
Verifying the LCS Configuration for the SGSN 298
Monitoring and Troubleshooting the LCS on the SGSN 298
CHAPTER 22
LORC Subscriber Overcharging Protection for S4-SGSN 299
Feature Description 299
LORC Subscriber Overcharge Protection on the S4-SGSN 299
Release Access Bearer Requests 300
Relationships 300
How It Works 300
3G Iu-Release Procedure and Overcharge Protection over S4 301
2G Ready-to-Standby State Transition and Overcharge Protection over S4 301
Standards Compliance 302
Configuring Subscriber Overcharging Protection 303
Enabling Release Access Bearer Request 303
Configuring the Causes to Include ARRL in Release Access Bearer Request 304
Enabling Subscriber Overcharging Protection on S4 306
CHAPTER 23
MOCN for 2G SGSN 307
Feature Description 307
Gate Core Network (GWCN) Configuration 308
Multi Operator Core Network (MOCN) Configuration 309
Relationships to Other Features 309
How It Works 309
Automatic PLMN Selection in Idle Mode 309
MOCN Configuration with Non-supporting MS 310
Architecture 311
Redirection in GERAN with MOCN Configuration 311
Standards Compliance 313
Configuring 2G MOCN 313
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GPRS MOCN Configuration 314
gprs-mocn 314
Verifying gprs-mocn Configuration 314
Common PLMN-Id and List of PLMN Ids Configuration 314
plmn id 314
Verifying plmn id Configuration 314
Network Sharing Configuration 315
network-sharing cs-ps-coordination 315
Verifying network-sharing Configuration 315
network-sharing failure-code 315
Verifying Failure Code Configuration 316
Monitoring and Troubleshooting 2G SGSN MOCN Support 316
show sgsn-mode 316
show gprs-service name 316
show gmm-sm statistics verbose 316
CHAPTER 24
MTC Congestion Control 319
Feature Description 319
Relationships 320
How It Works 320
SGSN Congestion Control 320
APN-level Congestion Control for MM 320
APN-level Congestion Control for SM 321
Support for the Extended T3312 Timer 322
Limitations 322
Flows for SGSN Congestion Control 323
Flows for APN-level Congestion Control for MM 325
Flows for APN-level Congestion Control for SM 326
Handling Value for Extended T3312 Timer 328
Standards Compliance 328
Configuring MTC Congestion Control 328
Enabling Global-level Congestion Control 329
Verifying the Global-level Congestion Control Configuration 329
Configuring System-detected Congestion Thresholds 330
Verifying System-detected Congestion Thresholds Configuration 330
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Configuring SGSN Congestion Control 331
Verifying the SGSN Congestion Control Configuration 332
Configuring APN-based Congestion Control 332
Verifying the APN-based Congestion Control Configuration 333
Configuring Extended T3312 Timer 333
Verifying the Extended T3312 Configurations 335
Configuring Backoff Timers 335
Verifying the T3346 Configurations 336
Configuring O&M Triggered Congestion 336
Monitoring MTC Congestion Control 337
show session disconnect-reasons 337
show congestion-control statistics imsimgr all full 337
CHAPTER 25
Network Requested Secondary PDP Context Activation 339
Feature Description 339
Benefits 339
Relationships to Other Features 340
How It Works 340
Gn/Gp SGSN 340
Successful Activation for Gn/Gp SGSN 341
Unsuccessful Activation for Gn/Gp SGSN 341
S4-SGSN 344
Successful Activation for S4-SGSN 344
Unsuccessful Activation for S4-SGSN 345
Limitations 347
Standards Compliance 347
Configuring NRSPCA 347
Sample NRSPCA Configuration 347
Verifying the NRSPCA Configuration 348
Monitoring and Troubleshooting the NRSPCA Feature 348
NRSPCA show Commands 349
show gmm-sm statistics sm-only 349
show sgtpc statistics 352
CHAPTER 26
Operator Policy 353
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What Operator Policy Can Do 353
A Look at Operator Policy on an SGSN 353
A Look at Operator Policy on an S-GW 354
The Operator Policy Feature in Detail 354
Call Control Profile 355
APN Profile 356
IMEI-Profile (SGSN only) 356
APN Remap Table 357
Operator Policies 357
IMSI Ranges 358
How It Works 358
Operator Policy Configuration 359
Call Control Profile Configuration 360
Configuring the Call Control Profile for an SGSN 360
Configuring the Call Control Profile for an MME or S-GW 361
APN Profile Configuration 361
IMEI Profile Configuration - SGSN only 362
APN Remap Table Configuration 362
Operator Policy Configuration 363
IMSI Range Configuration 363
Configuring IMSI Ranges on the MME or S-GW 363
Configuring IMSI Ranges on the SGSN 364
Associating Operator Policy Components on the MME 364
Configuring Accounting Mode for S-GW 364
Verifying the Feature Configuration 365
CHAPTER 27
Paging in Common Routing Area for 2G and 3G 367
Feature Description 367
How it Works 367
Paging in Common Routing Area for 2G subscriber 368
Paging in Common Routing Area for 3G subscriber 368
Standards Compliance 369
Configuring Paging in Common Routing Area for 2G and 3G 369
Verifying the Paging in Common Routing Area for 2G and 3G Configuration 369
show sgsn-mode 369
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Monitoring and Troubleshooting Paging in Common Routing Area for 2G and 3G feature 369
Paging in Common Routing Area for 2G and 3G Show Command(s) and/or Outputs 370
show gmm-sm statistics 370
Paging in Common Routing Area for 2G and 3G Bulk Statistics 371
CHAPTER 28
Page Throttling 373
Feature Description 373
Relationships to Other SGSN Features 373
How it Works 374
Page Throttling in a GPRS Scenario 374
Page Throttling in an UMTS Scenario 376
Limitations 377
Configuring Page Throttling 378
To map RNC Name to RNC Identifier 378
To associate a paging RLF template 379
Verifying the Page Throttling Configuration 379
Monitoring and Troubleshooting the Page Throttling feature 380
Page Throttling Show Command(s) and/or Outputs 380
show gmm-sm statistics verbose 380
CHAPTER 29
PGW Restart Notification in S4-SGSN 383
Feature Description 383
Overview 383
How it Works 384
Limitations 384
Standards Compliance 385
Configuring PGW Restart Notification in S4-SGSN 385
Configure Node IE For PRN Advertisement 385
Configure Default APN Restoration Priority 385
Verifying the PRN Configuration in S4-SGSN 386
Monitoring and Troubleshooting PRN support in S4-SGSN 386
PGW Restart Notification Show Command(s) and/or Outputs 386
show s4-sgsn statistics 386
show egtpc statistics 386
show session disconnect-reasons verbose 387
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CHAPTER 30
Quality of Service (QoS) Management for SGSN 389
Quality of Service Management 389
SGSN Quality of Service Management 389
Quality of Service Attributes 389
Quality of Service Attributes in Release 97/98 390
Quality of Service Attributes in Release 99 390
Quality of Service Management in SGSN 391
QoS Features 395
Traffic Policing 395
QoS Management When UE is Using S4-interface for PDP Contexts 400
QoS Handling Scenarios 405
QoS Handling During Primary PDP Activation 411
QoS Handling When EPS Subscription is Available 411
QoS Handling When Only GPRS Subscription is Available 411
QoS Handling During Secondary PDP Activation 412
QoS Handling When EPS Subscription is Available 412
QoS Handling When Only GPRS Subscription is Available 412
MS Initiated QoS Modification 412
HSS Initiated PDP Context Modification 414
PGW Initiated QoS Modification 415
ARP Handling 415
Difference between Gn SGSN and S4 SGSN 415
ARP values in Gn SGSN 415
ARP values in S4 SGSN 418
Handling of ARP Values in Various Scenarios 419
Mapping EPC ARP to RANAP ARP 420
ARP configured in CC Profile 421
ARP-RP Mapping for Radio Priority in Messages 422
CHAPTER 31
RIM Message Transfer from BSC or RNC to eNodeB 425
Feature Description 425
RAN Information Management (RIM) 425
Relationships to Other Feature or Products 426
How It Works 426
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RIM Addressing 426
Call Flows - Transmitter of GTP RIM Msg 427
Call Flows - Receiver of GTP RIM Msg 428
RIM Application 428
Standards Compliance 429
Configuring RIM Msg Transfer to or from eNodeB 429
Configuring RIM Functionality 429
Associating Previously Configured SGTP and IuPS Services 430
Configuring the peer-MME's address - Locally 430
Configuring the peer-MME's address - for DNS Query 430
Monitoring and Troubleshooting RIM Msg Transfer 430
show gmm-sm statistics verbose 431
show gmm-sm statistics verbose | grep RIM 431
show sgtpc statistics verbose 431
show bssgp statistics verbose 431
CHAPTER 32
RTLLI Management for 2G M2M Devices 433
Feature Description 433
How It Works 433
Configuring RTLLI Management 434
Monitoring and Troubleshooting 435
CHAPTER 33
S4 interface Support For Non-EPC Devices 437
Feature Description 437
Overview 437
How it Works 438
Architecture 438
Limitations 440
Configuring S4 Interface Support for Non-EPC Capable Devices 440
Configuring selection of the S4 interface 441
Monitoring and Troubleshooting S4 Interface Support for Non-EPC Capable devices 441
S4 Interface Support for Non-EPC devices Show Command(s) and/or Outputs 441
show call-control-profile full name < > 441
show subscribers sgsn-only full imsi < > 442
show subscribers gprs-only full imsi < > 442
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CHAPTER 34
S4-SGSN Suspend-Resume Feature 443
Feature Description 443
Suspension of GPRS Services 443
Relationships to Other Features 444
How it Works 444
S4-SGSN Suspend-Resume Feature 444
Limitations 444
Call Flows 445
Intra-SGSN Suspend Procedure with Resume as the Subsequent Procedure 445
Intra-SGSN Suspend with Resume Procedure with Intra-RAU as Subsequent
Procedure 446
Inter-SGSN Suspend and Resume Procedure with Peer S4-SGSN/MME 447
New Inter-SGSN Suspend and Resume Procedure from BSS to 2G Gn-SGSN 448
New SGSN Suspend and Resume Procedure with Peer Gn-SGSN as Old SGSN 449
Interface Selection Logic for Inter-SGSN Suspend (New SGSN) Procedure 451
Intra-SGSN Inter-System Suspend and Resume Procedure 452
Inter-SGSN Inter-System Suspend and Resume Procedure 453
Standards Compliance 455
Configuring the S4-SGSN Suspend/Resume Feature 455
Monitoring and Troubleshooting the S4-SGSN Suspend/Resume Feature 455
S4-SGSN Suspend and Resume Feature Show Commands 455
show subscriber gprs-only full all 455
show subscriber sgsn-only full all 456
show bssgp statistics verbose 456
show egtpc statistics 457
show egtpc statistics verbose 458
show sgtpc statistics verbose 462
S4-SGSN Suspend and Resume Feature Bulk Statistics 463
CHAPTER 35
SGSN-MME Combo Optimization 467
Feature Description 467
Overview 467
How It Works 468
Architecture 469
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Flows 470
Limitations 471
Configuring the Combo Optimization 471
Verifying Combo Optimization Configuration 472
show lte-policy sgsn-mme summary 472
Monitoring and Troubleshooting Combo Optimization 472
Monitoring Commands for the SGSN-MME Combo Node 472
show hss-peer-service statistics all 472
Monitoring Commands for the SGSN 473
show demux-mgr statistics imsimgr all sgsn 473
show subscribers sgsn-only summary 473
show subscribers gprs-only summary 473
show subscribers sgsn-only full all 473
show subscribers gprs-only full all 474
show session subsystem facility aaamgr instance 474
Monitoring Commands for the MME 475
show mme-service statistics handover 475
Bulk Statistics for Monitoring the MME in an SGSN-MME Combo Node 475
CHAPTER 36
SGSN Pooling 477
Feature Description 477
A Basic Pool Structure 478
Benefits of SGSN Pooling 479
Pooling Requirements 479
How it Works 479
P-TMSI - NRI and Coding 479
Non-Broadcast LAC and RAC 479
SGSN Address Resolution 480
Mobility Inside the Pool 480
Mobility Outside the Pool 481
MS Offloading 483
Iu/Gb Flex support over S16/S3 interface 484
Standards Compliance 485
Configuring the SGSN Pooling feature 486
2G-SGSN pool configuration 486
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3G-SGSN pool configuration 486
Monitoring and Troubleshooting the SGSN Pooling feature 488
SGSN Pooling Show Command(s) and/or Outputs 488
CHAPTER 37
SGSN Processes Uplink Data Status IE in Service Request 489
Feature Description 489
Standards Compliance 489
Configuring Processing of Uplink Data Status IE in Service Request 490
Verifying the Configuration 490
Monitoring and Troubleshooting the Feature 490
Show Command(s) and/or Outputs 490
show gmm-sm statistics 490
CHAPTER 38
SGSN Serving Radio Network Subsystem Relocation 491
Feature Description 491
Relationships to Other Features 491
How it Works 492
SRNS Relocation on the SGSN (Gn/Gp) 492
SGSN (Gn/Gp) SRNS Relocation Call Flow Diagrams 494
SRNS Relocation on the S4-SGSN 500
IDFT Support During Connected Mode Handovers 503
S4-SGSN SRNS Relocation Call Flow Diagrams 505
Standards Compliance 528
Configuring SRNS Relocation on the SGSN 528
Configuring the SRNS Relocation Feature 528
Enabling IDFT (Optional, S4-SGSN Only) 529
Verifying the SRNS Feature Configuration 529
Monitoring and Troubleshooting SRNS Relocation 530
SRNS Bulk Statistics 530
Show Command Output Supporting the SRNS Relocation Feature 531
CHAPTER 39
SGSN Support for IMSI Manager Scaling 535
Feature Description 535
How it Works 536
Detailed Description 536
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Relationships to Other Features 536
Configuring Support for Multiple IMSI Managers 537
Verifying the Configuration 537
Monitoring and Troubleshooting the Multiple IMSI Manager Support 537
Multiple IMSI Managers Show Command(s) and/or Outputs 538
show linkmgr all 538
show linkmgr instance parser statistics all 538
show gbmgr instance parser statistics all 538
show demuxmgr statistics imsimgr verbose 538
show demux-mgr statistics sgtpcmgr instance < id > 539
show session subsystem facility mmemgr instance < id > 539
show subscribers mme-only full all/ show mme-service session full all 539
show mme-service db record call-id <id> 539
CHAPTER 40
SGSN Support for Peer-Server Blocking 541
Feature Description 541
How it Works 542
Configuring Peer-Server Blocking 544
Verifying the Peer-Server Blocking Configuration 544
Monitoring and Troubleshooting the Peer-Server Blocking 544
CHAPTER 41
Support for EPC QoS Attributes on SGSN 547
Feature Description 547
Overview 547
How It Works 548
Standards Compliance 549
Configuring EPC QoS Support on SGSN 549
Configuring QoS Profile to Support EPS QoS Parameters in GTPv1 messages 549
Configure E-ARP values in the Quality of Service Profile 550
Configure Local Capping in the Quality of Service Profile 550
Configure Override of E-ARP Values Provided by GGSN 550
Verifying the Configuration 551
Monitoring and Troubleshooting EPC QoS Support on SGSN 551
Show Command(s) and/or Outputs 551
show subscriber sgsn-only full all 551
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Troubleshooting EPC QoS Support on SGSN 551
CHAPTER 42
Support For QoS Upgrade From GGSN or PCRF 553
Feature Description 553
How it Works 553
Configuring Support for QoS upgrade from GGSN/PCRF 555
Verifying the QoS Upgrade Support Configuration 556
CHAPTER 43
Support for SGSN QoS based on PLMN, RAT Type 557
Feature Description 557
How it Works 557
Configuring SGSN Support for RAT Type based QoS Selection 558
Configuring APN Profile and QoS Profile Association 558
Configuring the Quality of Service Profile 559
Monitoring and Troubleshooting RAT Type Based QoS Selection 559
Show Command(s) and/or Outputs 559
show apn-profile full [all | name] 559
show quality-of-service-profile [ all | full [ all | name ] | name ] 560
CHAPTER 44
Support for RAT/Frequency Selection Priority ID (RFSP-ID) 561
Feature Description 561
How it Works 562
Encoding and De-coding of RFSP Ids in different scenarios 562
Standards Compliance 564
Configuring Support for RAT/Frequency Selection Priority ID 565
Monitoring and Troubleshooting the the Support for RFSP-ID 565
Show Command(s) and/or Outputs 565
show call-control profile 565
show subscribers sgsn-only full all 566
show subscribers gprs-only full all 566
show iups-service name 566
show sgsn-mode 566
CHAPTER 45
Subscriber Overcharging Protection 567
Feature Overview 567
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Overcharging Protection - GGSN Configuration 568
GTP-C Private Extension Configuration 569
Verifying Your GGSN Configuration 569
Overcharging Protection - SGSN Configuration 570
Private Extension IE Configuration 571
RANAP Cause Trigger Configuration 571
Verifying the Feature Configuration 571
CHAPTER 46
Topology-based Gateway Selection 573
Feature Description 573
How It Works 574
First Primary Activation - Gn/Gp-SGSN 574
Primary Activation - S4-SGSN 575
Primary Activation for Subsequent PDN 575
Intra RAU, New SGSN RAU, Intra SRNS, New SRNS, IRAT 575
Limitations 575
Standards Compliance 576
Configuring Topology-based GW Selection 576
Configuring GW Selection 576
Verifying the GW Selection Configuration 577
Configuring DNS Queries for the Gn/Gp-SGSN 577
Verifying the DNS Queries Configuration for the Gn/Gp-SGSN 578
Configuring DNS Queries for the S4-SGSN 578
Verifying the DNS Queries Configuration for the S4-SGSN 578
Configuring the Canonical Node Name for the Gn/Gp-SGSN 578
Verifying the Canonical Node Name Configuration 579
Monitoring Topology-based GW Selection 579
show subscribers [ gprs-only | sgsn-only ] full 579
CHAPTER 47
UDPC2 Support for MME/SGSN 581
Feature Description 581
How It Works 582
Configuring MME/SGSN Support on UDPC2 583
Verifying the Configuration 587
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CHAPTER 48
Monitoring and Troubleshooting 589
Monitoring and Troubleshooting 589
Monitoring 590
Daily - Standard Health Check 590
Monthly System Maintenance 593
Every 6 Months 594
Troubleshooting 594
Problems and Issues 595
Troubleshooting More Serious Problems 595
Causes for Attach Reject 595
Single Attach and Single Activate Failures 596
Mass Attach and Activate Problems 597
Single PDP Context Activation without Data 598
Mass PDP Context Activation but No Data 599
APPENDIX A
Engineering Rules 601
Engineering Rules 601
Service Rules 601
SGSN Connection Rules 602
Operator Policy Rules 603
SS7 Rules 605
SS7 Routing 605
SIGTRAN 606
Broadband SS7 606
SCCP 606
GTT 607
SGSN Interface Rules 607
System-Level 607
3G Interface Limits 608
2G Interface Limits 608
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About this Guide
This preface describes the SGSN Administration Guide, its organization, document conventions, related
documents, and contact information for Cisco customer service.
The SGSN (Serving GPRS Support Node) is a StarOS application that runs on Cisco® ASR 5x00 and
virtualized platforms.
• Conventions Used, page xxxiii
• Supported Documents and Resources, page xxxiv
• Contacting Customer Support , page xxxv
Conventions Used
The following tables describe the conventions used throughout this documentation.
Notice Type
Description
Information Note
Provides information about important features or instructions.
Caution
Alerts you of potential damage to a program, device, or system.
Warning
Alerts you of potential personal injury or fatality. May also alert you
of potential electrical hazards.
Typeface Conventions
Description
Text represented as a screen
display
This typeface represents displays that appear on your terminal
screen, for example:
Login:
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About this Guide
Supported Documents and Resources
Typeface Conventions
Description
Text represented as commands
This typeface represents commands that you enter, for example:
show ip access-list
This document always gives the full form of a command in
lowercase letters. Commands are not case sensitive.
Text represented as a command variable This typeface represents a variable that is part of a command, for
example:
show card slot_number
slot_number is a variable representing the desired chassis slot
number.
Text represented as menu or sub-menu
names
This typeface represents menus and sub-menus that you access
within a software application, for example:
Click the File menu, then click New
Supported Documents and Resources
Related Common Documentation
The most up-to-date information for this product is available in the SGSN Release Notes provided with each
product release.
The following common documents are available:
• AAA Interface Administration and Reference
• Command Line Interface Reference
• GTPP Interface Administration and Reference
• Installation Guide (platform dependent)
• Release Change Reference
• SNMP MIB Reference
• Statistics and Counters Reference
• System Administration Guide (platform dependent)
• Thresholding Configuration Guide
• Cisco StarOS IP Security (IPSec) Reference
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About this Guide
Related Product Documentation
Related Product Documentation
The following documents are also available for products that work in conjunction with the SGSN:
• GGSN Administration Guide
• InTracer Installation and Administration Guide
• MME Administration Guide
• MURAL Software Installation Guide
• Web Element Manager Installation and Administration Guide
Obtaining Documentation
The most current Cisco documentation is available on the following website:
http://www.cisco.com/cisco/web/psa/default.html
Use the following path selections to access the SGSN documentation:
Products > Wireless > Mobile Internet> Network Functions > Cisco SGSN Serving GPRS Support Node
Contacting Customer Support
Use the information in this section to contact customer support.
Refer to the support area of http://www.cisco.com for up-to-date product documentation or to submit a service
request. A valid username and password are required to access this site. Please contact your Cisco sales or
service representative for additional information.
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Contacting Customer Support
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CHAPTER
1
Serving GPRS Support Node (SGSN) Overview
This section contains general overview information about the Serving GPRS Support Node (SGSN), including
sections for:
• Product Description, page 1
• Network Deployments and Interfaces, page 3
• SGSN Core Functionality , page 10
• Features and Functionality , page 18
• How the SGSN Works, page 77
• Supported Standards, page 82
Product Description
StarOS provides a highly flexible and efficient Serving GPRS Support Node (SGSN) service to the wireless
carriers. Functioning as an SGSN, the system readily handles wireless data services within 2.5G General
Packet Radio Service (GPRS) and 3G Universal Mobile Telecommunications System (UMTS) data networks.
The SGSN also can serve as an interface between GPRS and/or UMTS networks and the 4G Evolved Packet
Core (EPC) network.
Important
Throughout this section the designation for the subscriber equipment is referred to in various ways: UE
for user equipment (common to 3G/4G scenarios), MS or mobile station (common to 2G/2.5G scenarios),
and MN or mobile node (common to 2G/2.5G scenarios involving IP-level functions). Unless noted, these
terms are equivalent and the term used usually complies with usage in the relevant standards.
In a GPRS/UMTS network, the SGSN works in conjunction with radio access networks (RANs) and Gateway
GPRS Support Nodes (GGSNs) to:
• Communicate with home location registers (HLR) via a Gr interface and mobile visitor location registers
(VLRs) via a Gs interface to register a subscriber\'s user equipment (UE), or to authenticate, retrieve or
update subscriber profile information.
• Support Gd interface to provide short message service (SMS) and other text-based network services for
attached subscribers.
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Qualified Platforms
• Activate and manage IPv4, IPv6, or point-to-point protocol (PPP) -type packet data protocol (PDP)
contexts for a subscriber session.
• Setup and manage the data plane between the RAN and the GGSN providing high-speed data transfer
with configurable GEA0-3 ciphering.
• Provide mobility management, location management, and session management for the duration of a call
to ensure smooth handover.
• Provide various types of charging data records (CDRs) to attached accounting/billing storage mechanisms
such as our SMC-based hard drive or a GTPP Storage Server (GSS) or a charging gateway function
(CGF).
• Provide CALEA support for lawful intercepts.
The S4-SGSN is an SGSN configured with 2G and/or 3G services and then configured to interface with the
4G EPC network via the S4 interface. This enables the S4-SGSN to support handovers from UMTS/GPRS
networks to the EPC network. The S4-SGSN works in conjunction with EPC network elements and gateways
to:
• Interface with the EPC network S-GW (via the S4 interface) and MME (via the S3 interface) to enable
handovers between 2G/3G networks and the EPC (4G) network.
• Interface with the Equipment Identity Registry via the S13\' interface to perform the ME identity check.
• Interface with the HSS via the S6d interface to obtain subscription-related information.
• Communicate with S4-SGSNs via the S16 interface.
• Provide Idle Mode Signaling support for EPC-capable UEs.
This section catalogs many of the SGSN key components and features for data services within the GPRS/UMTS
environment. Also, a range of SGSN operational and compliance information is summarized with pointers to
other information sources.
Qualified Platforms
SGSN is a StarOS application that runs on Cisco® ASR 5x00 and virtualized platforms. For additional platform
information, refer to the appropriate System Administration Guide and/or contact your Cisco account
representative.
Licenses
The SGSN is a licensed Cisco product and requires the purchase and installation of the SGSN Software
License. Separate feature licenses may be required. Contact your Cisco account representative for detailed
information on specific licensing requirements.
For information on installing and verifying licenses, refer to the Managing License Keys section of the Software
Management Operations section in the System Administration Guide.
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Network Deployments and Interfaces
Network Deployments and Interfaces
The following logical connection maps illustrate the SGSN\'s ability to connect to various radio access network
types, core network types, and network components:
• GSM edge radio access network (GERAN) provides access to the 2.5G general packet radio service
(GPRS) network
• UMTS terrestrial radio access network (UTRAN) provides access to the 3G universal mobile
telecommunications system (UMTS) network
• Evolved UTRAN (E-UTRAN) provides access to the 4G mobile evolved packet core (EPC) of the long
term evolution/system architecture evolution (LTE/SAE) network
• Another SGSN
• Standalone gateway GPRS support node (GGSN)
• Co-located P-GW/GGSN
• Mobile Service Center (MSC)
• Visitor Location Register (VLR)
• Home Location Register (HLR)
• Charging Gateway (CF - sometimes referred to as a charging gateway function (CGF))
• GTPP Storage Server (GSS)
• Equipment Identity Registry (EIR)
• Home Subscriber Server (HSS)
• Mobility Management Entity (MME)
• Serving Gateway (S-GW)
• CAMEL service\'s GSM service control function (gsmSCF)
• Short Message Service server Center (SMS-C)
• Network devices in another PLMN
SGSN and Dual Access SGSN Deployments
SGSNs and GGSNs work in conjunction within the GPRS/UMTS network. As indicated earlier in the section
on System Configuration Options, the flexible architecture of StarOS enables a single chassis to reduce
hardware requirements by supporting integrated co-location of a variety of the SGSN services.
A chassis can be devoted solely to SGSN services or the SGSN system can include any co-location combination,
such as multiple instances of 2.5G SGSNs (configured as GPRS services); or multiple instances of 3G SGSNs
(configured as SGSN services); or a combination of 2.5G and 3G SGSN to comprise a dual access SGSN.
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SGSN and Dual Access SGSN Deployments
Important
The following illustrates the GPRS/UMTS Dual Access architecture with a display of all the interfaces
supported as of Release 14.0. The SGSN Logical Network Interfaces section below lists the interfaces
available for the release applicable to the version of this manual.
Figure 1: 2.5G and 3G Dual Access Architecture
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SGSN/GGSN Deployments
SGSN/GGSN Deployments
The co-location of the SGSN and the GGSN in the same chassis facilitates handover. A variety of GSN combos
is possible, 2.5G or 3G SGSN with the GGSN.
Figure 2: GSN Combo Architecture
S4-SGSN Deployments
An S4-SGSN is an SGSN that is configured for S4 interface support to enable the soft handover of 2G and
3G subscribers to the EPC S-GW via the EPC S4 interface. Comprehensive S4-SGSN support includes
interfaces to the following network elements and gateways:
• EPC serving gateway (S-GW) via the S4 interface
• Equipment identity registry (EIR) via the S13\' interface
• Home subscriber server (HSS) via the S6d interface
• EPC mobility management entity (MME) via the S3 interface
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S4-SGSN Deployments
• Peer S4-SGSN via the S16 interface
The S4, S13\' and S6d interfaces are license-enabled features. Support for the S16 and S3 interfaces are
included as part of the S4 license.
Figure 3: S4-SGSN Network Architecture
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SGSN Logical Network Interfaces
SGSN Logical Network Interfaces
The SGSN provides IP-based transport on all RAN and core network interfaces, in addition to the standard
IP-based interfaces (Ga, Gn, Gp, Iu-PS). This means enhanced performance, future-proof scaling and reduction
of inter-connectivity complexity. The all-IP functionality is key to facilitating evolution to the next generation
technology requirements.
The SGSN provides the following functions over the logical network interfaces illustrated above:
• Ga: The SGSN uses the Ga interface with GPRS Transport Protocol Prime (GTPP) to communicate
with the charging gateway (CG, also known as CGF) and/or the GTPP storage server (GSS). The interface
transport layer is typically UDP over IP but can be configured as TCP over IP for:
◦One or more Ga interfaces per system context, and
◦An interface over Ethernet 10/100 or Ethernet 1000 interfaces
The charging gateway handles buffering and pre-processing of billing records and the GSS provides
storage for Charging Data Records (CDRs). For additional information regarding SGSN charging, refer
to the Charging section.
• IuPS: The SGSN provides an IP over ATM (IP over AAL5 over ATM) interface between the SGSN
and the RNCs in the 3G UMTS radio access network (UTRAN). RANAP is the control protocol that
sets up the data plane (GTP-U) between these nodes. SIGTRAN (M3UA/SCTP) or QSAAL
(MTP3B/QSAAL) handle IuPS-C (control) for the RNCs.
Some of the procedures supported across this interface are:
◦Control plane based on M3UA/SCTP
◦Up to 128 Peer RNCs per virtual SGSN. Up to 256 peers per physical chassis
◦SCTP Multi-Homing supported to facilitate network resiliency
◦M3UA operates in and IPSP client/server and single/double-ended modes
◦Multiple load shared M3UA instances for high-performance and redundancy
◦Works over Ethernet and ATM (IPoA) interfaces
◦Facilitates SGSN Pooling
◦RAB (Radio Access Bearer) Assignment Request
◦RAB Release Request
◦Iu Release Procedure
◦SGSN-initiated Paging
◦Common ID
◦Security Mode Procedures
◦Initial MN Message
◦Direct Transfer
◦Reset Procedure
◦Error Indication
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SGSN Logical Network Interfaces
◦SRNS relocation
• Gb: This is the SGSN\'s interface to the base station system (BSS) in a 2G radio access network (RAN).
It connects the SGSN via UDP/IP via an Ethernet interface or Frame Relay via a Channelized SDH or
SONET interface (only available on an ASR 5000 chassis). Gb-IP is the preferred interface as it improves
control plane scaling as well as facilitates the deployment of SGSN Pools.
Some of the procedures supported across this interface are:
◦BSS GSM at 900/1800/1900 MHz
◦BSS Edge
◦Frame Relay congestion handling
◦Traffic management per Frame Relay VC
◦NS load sharing
◦NS control procedures
◦BVC management procedures
◦Paging for circuit-switched services
◦Suspend/Resume
◦Flow control
◦Unacknowledged mode
◦Acknowledged mode
• Gn/Gp: The Gn/Gp interfaces, comprised of GTP/UDP/IP-based protocol stacks, connect the SGSNs
and GGSNs to other SGSNs and GGSNs within the same public land mobile network (PLMN) - the Gn
- or to GGSNs in other PLMNs - the Gp.
This implementation supports:
◦GTPv0 and GTPv1, with the capability to auto-negotiate the version to be used with any particular
peer
◦GTP-C (control plane) and GTP-U (user plane)
◦Transport over ATM/STM-1Optical (only available with an ASR 5000 chassis), Fast Ethernet,
and Ethernet 1000 line cards/QGLCs)
◦One or more Gn/Gp interfaces configured per system context
As well, the SGSN can support the following IEs from later version standards:
◦IMEI-SV
◦RAT TYPE
◦User Location Information
◦Extended PDP Type (Release 9)
◦Extended RNC ID (Release 9)
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SGSN Logical Network Interfaces
• Ge: This is the interface between the SGSN and the SCP that supports the CAMEL service. It supports
both SS7 and SIGTRAN and uses the CAP protocol.
• Gr: This is the interface to the HLR. It supports SIGTRAN (M3UA/SCTP/IP) over Ethernet.
Some of the procedures supported by the SGSN on this interface are:
◦Send Authentication Info
◦Update Location
◦Insert Subscriber Data
◦Delete Subscriber Data
◦Cancel Location
◦Purge
◦Reset
◦Ready for SM Notification
◦SIGTRAN based interfaces M3UA/SCTP
◦Peer connectivity can be through an intermediate SGP or directly depending on whether the peer
(HLR, EIR, SMSC, GMLC) is SIGTRAN enabled or not
◦SCTP Multi-Homing supported to facilitate network resiliency
◦M3UA operates in IPSP client/server and single/double-ended modes
◦Multiple load shared M3UA instances for high-performance and redundancy
◦Works over Ethernet (IPoA) interface
• Gs: This is the interface used by the SGSN to communicate with the visitor location register (VLR) or
mobile switching center (MSC) to support circuit switching (CS) paging initiated by the MSC. This
interface uses Signaling Connection Control Part (SCCP) connectionless service and BSSAP+ application
protocols.
• Gd: This is the interface between the SGSN and the SMS Gateway (SMS-GMSC / SMS-IWMSC) for
both 2G and 3G technologies through multiple interface mediums. Implementation of the Gd interface
requires purchase of an additional license.
• Gf: Interface is used by the SGSN to communicate with the equipment identity register (EIR) which
keeps a listing of UE (specifically mobile phones) being monitored. The SGSN\'s Gf interface
implementation supports functions such as:
◦International Mobile Equipment Identifier-Software Version (IMEI-SV) retrieval
◦IMEI-SV status confirmation
• Lg: This is a Mobile Application Part (MAP) interface, between the SGSN and the gateway mobile
location center (GMLC), supports 3GPP standards-compliant LoCation Services (LCS) for both 2G and
3G technologies. Implementation of the Lg interface requires purchase of an additional license.
• S3:On the S4-SGSN, this interface provides a GTPv2-C signaling path connection between the EPC
mobility management entity (MME) and the SGSN. This functionality is part of the S4 interface feature
license.
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SGSN Core Functionality
• S4: On the S4-SGSN, this interface provides a data and signaling interface between the EPC S-GW and
the S4-SGSN for bearer plane transport (GTPv1-U). The S4-SGSN communicates with the P-GW via
the S-GW. A separate feature license is required for S4 interface support.
• S6d: On the SGSN, this is the S6d interface between the SGSN and the HSS. This enables the SGSN
to get subscription details of a user from the HSS when a user tries to register with the SGSN. A separate
feature license is required for S6d Diameter interface support.
• S13\': The SGSN supports the S13\' interface between the SGSN and the EIR. This enables the SGSN
to communicate with an Equipment Identity Registry (EIR) via the Diameter protocol to perform the
Mobile Equipment (ME) identity check procedure between the SGSN and EIR. Performing this procedure
enables the SGSN to verify the equipment status of the Mobile Equipment. A separate feature license
is required for S13\' interface support.
• S16:On the S4-SGSN, this interface provides a GTPv2 path to a peer S4-SGSN. Support for this interface
is provided as part of the S4 interface license.
SGSN Core Functionality
The SGSN core functionality is comprised of:
• All-IP Network (AIPN), on page 10
• SS7 Support
• PDP Context Support
• Mobility Management
• Location Management
• Session Management
• Charging
All-IP Network (AIPN)
AIPN provides enhanced performance, future-proof scaling and reduction of inter-connectivity complexity.
In accordance with 3GPP, the SGSN provides IP-based transport on all RAN and core network interfaces, in
addition to the standard IP-based interfaces (Ga, Gn, Gp, Iu-Data). The all-IP functionality is key to facilitating
Iu and Gb Flex (SGSN pooling) functionality as well as evolution to the next generation technology
requirements.
The following IP-based protocols are supported on the SGSN:
• SCTP
• M3UA over SCTP
• GTPv0 over UDP
• GTPv1 over UDP
• GTPv2 over UDP (S4-SGSN only)
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SS7 Support
• GTP-U over UDP
• Diameter over TCP and SCTP (S4-SGSN only)
SS7 Support
StarOS SGSN implements SS7 functionality to communicate with the various SS7 network elements, such
as HLRs and VLRs.
The SGSN employs standard Signaling System 7 (SS7) addressing (point codes) and global title translation.
SS7 feature support includes:
• Transport layer support includes:
◦Broadband SS7 (MTP3B/SSCF/SSCOP/AAL5)
◦Narrowband SS7 (high speed and low speed) (only available on an ASR 5000 chassis)
◦SIGTRAN (M3UA/SCTP/IP)
• SS7 variants supported:
◦ITU-T (International Telecommunication Union - Telecommunications - Europe)
◦ANSI (American National Standards Institute - U.S.)
◦B-ICI (B-ISDN Inter-Carrier Interface)
◦China
◦TTC (Telecommunication Technology Committee - Japan)
◦NTT (Japan)
• SS7 protocol stack components supported:
◦MTP2 (Message Transfer Part, Level 2)
◦MTP3 (Message Transfer Part, Level 3)
◦SCCP (Signaling Connection Control Part ) with BSSAP+ (Base Station System Application Part
Plus) and RANAP (Radio Access Network Application Part)
◦ISUP (ISDN User Part
◦TCAP (Transaction Capabilities Applications Part) and MAP (Mobile Application Part)
PDP Context Support
Support for subscriber primary and secondary Packet Data Protocol (PDP) contexts in compliance with 3GPP
standards ensure complete end-to-end GPRS connectivity.
The SGSN supports a total of 11 PDP contexts per subscriber. Of the 11 PDP context, all can be primaries,
or 1 primary and 10 secondaries or any combination of primary and secondary. Note that there must be at
least one primary PDP context in order for secondaries to establish.
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Mobility Management
PDP context processing supports the following types and functions:
• Types: IPv4, IPv6, IPv4v6 (dual stack) and/or PPP
• GTPP accounting support
• PDP context timers
• Quality of Service (QoS)
Mobility Management
The SGSN supports mobility management (MM) in compliance with applicable 3GPP standards and procedures
to deliver the full range of services to the mobile device. Some of the procedures are highlighted below:
GPRS Attach
The SGSN is designed to accommodate a very high rate of simultaneous attaches. The actual attach rate
depends on the latencies introduced by the network and scaling of peers. In order to optimize the entire
signaling chain, the SGSN eliminates or minimizes bottlenecks caused by large scale control signaling. For
this purpose, the SGSN implements features such as an in-memory data-VLR and SuperCharger. Both IMSI
and P-TMSI based attaches are supported.
The SGSN provides the following mechanisms to control MN attaches:
• Attached Idle Timeout - When enabled, if an MN has not attempted to setup a PDP context since
attaching, this timer forces the MN to detach with a cause indicating that the MN need not re-attach.
This timer is particularly useful for reducing the number of attached subscribers, especially those that
automatically attach at power-on.
• Detach Prohibit - When enabled, this mechanism disables the Attached Idle Timeout functionality for
selected MNs which aggressively re-attach when detached by the network.
• Prohibit Reattach Timer - When enabled, this timer mechanism prevents MNs, that were detached
due to inactivity, from re-attaching for a configured period of time. Such MNs are remembered by the
in-memory data-VLR until the record needs to be purged.
• Attach Rate Throttle - It is unlikely that the SGSN would become a bottleneck because of the SGSN\'s
high signaling rates. However, other nodes in the network may not scale commensurately. To provide
network overload protection, the SGSN provides a mechanism to control the number of attaches occurring
through it on a per second basis.
Beside configuring the rate, it is possible to configure the action to be taken when the overload limit is reached.
See the network-overload-protection command in the "Global Configuration Mode" section in the Command
Line Interface Reference. Note, this is a soft control and the actual attach rate may not match exactly the
configured value depending on the load conditions.
GPRS Detach
The SGSN is designed to accommodate a very high rate of simultaneous detaches. However, the actual detach
rate is dependent on the latencies introduced by the network and scaling of peers. A GPRS detach results in
the deactivation of all established PDP contexts.
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Mobility Management
There are a variety of detaches defined in the standards and the SGSN supports the following detaches:
• MN Initiated Detach - The MN requests to be detached.
• SGSN Initiated Detach - The SGSN requests the MN to detach due to expiry of a timer or due to
administrative action.
• HLR Initiated Detach - The detach initiated by the receipt of a cancel location from the HLR.
Mass detaches triggered by administrative commands are paced in order to avoid flooding the network and
peer nodes with control traffic.
Paging
CS-Paging is initiated by a peer node - such as the MSC - when there is data to be sent to an idle or unavailable
UE. CS-paging requires the Gs interface. This type of paging is intended to trigger a service request from the
UE. If necessary, the SGSN can use PS-Paging to notify the UE to switch channels. Once the UE reaches the
connected state, the data is forwarded to it.
Paging frequency can be controlled by configuring a paging-timer.
Service Request
The Service Request procedure is used by the MN in the PMM Idle state to establish a secure connection to
the SGSN as well as request resource reservation for active contexts.
The SGSN allows configuration of the following restrictions:
• Prohibition of services
• Enforce identity check
• PLMN restriction
• Roaming restrictions
Authentication
The SGSN authenticates the subscriber via the authentication procedure. This procedure is invoked on attaches,
PDP activations, inter-SGSN routing Area Updates (RAUs), and optionally by configuration for periodic
RAUs. The procedure requires the SGSN to retrieve authentication quintets/triplets from the HLR (AuC) and
issuing an authentication and ciphering request to the MN. The SGSN implements an in-memory data-VLR
functionality to pre-fetch and store authentication vectors from the HLR. This decreases latency of the control
procedures.
Additional configuration at the SGSN allows for the following:
• Enforcing ciphering
• Retrieval of the IMEI-SV
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Location Management
P-TMSI Reallocation
The SGSN supports standard Packet-Temporary Mobile Identity (P-TMSI) Reallocation procedures to provide
identity confidentiality for the subscriber.
The SGSN can be configured to allow or prohibit P-TMSI reallocation on the following events:
• Routing Area Updates
• Attaches
• Detaches
• Service Requests
The SGSN reallocates P-TMSI only when necessary.
P-TMSI Signature Reallocation
The SGSN supports operator definition of frequency and interval for Packet Temporary Mobile Subscriber
Identity (P-TMSI) signature reallocation for all types of routing area update (RAU) events.
Identity Request
This procedure is used to retrieve IMSI and IMEI-SV from the MN. The SGSN executes this procedure only
when the MN does not provide the IMSI and the MM context for the subscriber is not present in the SGSN\'s
data-VLR.
Location Management
The SGSN\'s 3GPP compliance for location management ensures efficient call handling for mobile users.
The SGSN supports routing area updates (RAU) for location management. The SGSN implements standards
based support for:
• Periodic RAUs
• Intra-SGSN RAUs
• Inter-SGSN RAUs.
The design of the SGSN allows for very high scalability of RAUs. In addition, the high capacity of the SGSN
and Flex functionality provides a great opportunity to convert high impact Inter-SGSN RAUs to lower impact
Intra-SGSN RAUs. The SGSN provides functionality to enforce the following RAU restrictions:
• Prohibition of GPRS services
• Enforce identity request
• Enforce IMEI check
• PLMN restriction
• Roaming restrictions
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Session Management
The SGSN also provides functionality to optionally supply the following information to the MN:
• P-TMSI Signature and Allocated P-TMSI
• List of received N-PDU numbers for loss less relocation
• Negotiated READY timer value
• Equivalent PLMNs
• PDP context status
• Network features supported
Session Management
Session management ensures proper PDP context setup and handling.
For session management, the SGSN supports four 3GPP-compliant procedures for processing PDP contexts:
• Activation
• Modification
• Deactivation
• Preservation
PDP Context Activation
The PDP context activation procedure establishes a PDP context with the required QoS from the MN to the
GGSN. These can be either primary or secondary contexts. The SGSN supports a minimum of 1 PDP primary
context per attached subscriber, and up to a maximum of 11 PDP contexts per attached subscriber.
The PDP context types supported are:
• PDP type IPv4
• PDP type IPv6
• PDP type IPv4v6
• PDP type PPP
Both dynamic and static addresses for the PDP contexts are supported.
The SGSN provides configuration to control the duration of active and inactive PDP contexts.
When activating a PDP context the SGSN can establish the GTP-U data plane from the RNC through the
SGSN to the GGSN or directly between the RNC and the GGSN (one tunnel).
The SGSN is capable of interrogating the DNS infrastructure to resolve the specified APN to the appropriate
GGSN. The SGSN also provides default and override configuration of QoS and APN.
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Charging
PDP Context Modification
This procedure is used to update the MN and the GGSN. The SGSN is capable of initiating the context
modification or negotiating a PDP context modification initiated by either the MN or the GGSN.
PDP Context Deactivation
This procedure is used to deactivate PDP contexts. The procedure can be initiated by the MN or the SGSN.
The SGSN provides configurable timers to initiate PDP deactivation of idle contexts as well as active contexts.
PDP Context Preservation
The SGSN provides this functionality to facilitate efficient radio resource utilization. This functionality comes
into play on the following triggers:
• RAB (Radio Access Bearer) Release Request
This is issued by the RAN to request the release of RABs associated with specific PDP contexts. The
SGSN responds with a RAB assignment request, waits for the RAB assignment response and marks the
RAB as having been released. The retention of the PDP contexts is controlled by configuration at the
SGSN. If the PDP contexts are retained the SGSN is capable of receiving downlink packets on them.
• Iu Release Request
The RAN issues an Iu release request to release all RABs of an MN and the Iu connection. The retention
of the PDP contexts is controlled by configuration at the SGSN. When PDP contexts are retained the
SGSN is capable of receiving downlink packets on them.
When PDP contexts are preserved, the RABs can be restored on a service request from the MN without
having to go through the PDP context establishment process again. The service request is issued by the
MN either when it has some data to send or in response to a paging request, on downlink data, from the
SGSN.
Charging
Charging functionality for the SGSN varies depending upon the type of network in which it is deployed.
SGSN in GPRS/UMTS Network
The SGSN provides an efficient and accurate billing system for all calls and SMSs passing through the SGSN.
The charging-specific interfaces and 3GPP standards supported by the SGSN deployments are listed below:
• Allows the configuration of multiple CGFs and a single GSS in a single GTPP group along with their
relative priorities.
• Implements the standardized Ga interface.
• Fully supports the GPRS Tunneling Protocol Prime (GTPP) over UDP/TCP.
• Supports the relevant charging information as defined in:
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Charging
◦3GPP TS 29.060 v7.9.0 (2008-09): Technical Specification; 3rd Generation Partnership Project;
Technical Specification Group Core Network; General Packet Radio Service (GPRS); GPRS
Tunnelling Protocol (GTP) across the Gn and Gp interface (Release 6)
◦3GPP TS 32.215 v5.9.0 (2005-06): 3rd Generation Partnership Project; Technical Specification
Group Services and System Aspects; Telecommunication management; Charging management;
Charging data description for the Packet Switched (PS) domain (Release 4)
◦3GPP TS.32.251 V8.8.0 (2009-12): 3rd Generation Partnership Project; Technical Specification
Group Services and System Aspects; Telecommunication management; Charging management;
Packet Switched (PS) domain charging (Release 8)
◦3GPP TS 32.298 V8.7.0 (2009-12): 3rd Generation Partnership Project; Technical Specification
Group Service and System Aspects; Telecommunication management; Charging management;
Charging Data Record (CDR) parameter description (Release 8)
Charging Data Records (CDRs)
The SGSN generates CDRs with the charging information. The following sections outline the types of CDRs
generated by the SGSN.
For full dictionary, CDR and field information, refer to the GTPP Accounting Overview, the SGSN and Mobility
Management Charging Detail Record Field Reference Tables, and the S-CDR Field Descriptions sections in
the AAA and GTPP Interface Administration and Reference
SGSN Call Detail Records (S-CDRs)
These charging records are generated for PDP contexts established by the SGSN. They contain attributes as
defined in TS 32.251 v7.2.0.
Mobility Call Detail Records (M-CDRs)
These charging records are generated by the SGSN\'s mobility management (MM) component and correspond
to the mobility states. They contain attributes as defined in 3GPP TS 32.251 v7.2.0.
Short Message Service CDRs
SGSN supports following CDRs for SMS related charging:
• SMS-Mobile Originated CDRs (SMS-MO-CDRs)
• SMS Mobile Terminated CDRs (SMS-MT-CDRs)
These charging records are generated by the SGSN\'s Short Message Service component. They contain
attributes as defined in 3GPP TS 32.215 v5.9.0.
Location Request CDRs
SGSN supports the following Location Request CDRs:
• Mobile terminated location request CDRs (LCS-MT-CDRs)
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Features and Functionality
• Mobile originated location request CDRs (LCS-MO-CDRs)
SGSN in LTE/SAE Network
Beginning in release 14.0, an SGSN can function in an LTE/SAE network using enhancements to support
various other interfaces including an S4 interface. In these cases, the SGSN is referred to as an S4-SGSN.
Serving Gateway Call Detail Records (S-GW-CDRs)
The S4-SGSN does not support S-CDRs because the S4 interface is used, per PDP (or EPS bearer) and charging
records are generated by the S-GW using the S-GW-CDR. The S-GW collects the charging information per
user per IP-CAN bearer. The collected information is called as S-GW-CDR and sent to the Charging Gateway
over the Gz interface.
Features and Functionality
It is impossible to list all of the features supported by the Gn/Gp SGSN (2.5G and 3G) or the S4-SGSN.
Those features listed below are only a few of the features that enable the operator to control the SGSN and
their network. All of these features are either proprietary or comply with relevant 3GPP specifications.
Some of the proprietary features may require a separate license. Contact your Cisco account representative
for detailed information on specific licensing requirements. For information on installing and verifying licenses,
refer to the Managing License Keys section of the Software Management Operations section in the System
Administration Guide.
3G-2G Location Change Reporting
With Location Change Reporting enabled, the SGSN facilitates location-based charging on the GGSN by
providing the UE\'s geographical location information when the UE is in connected mode.
Location-based charging is a values-added function that ensures subscribers pay a premium for location-based
services, such as service in a congested areas. With the required feature license installed, the operator uses
the CLI to enable the reporting independently for each network access type: GPRS (2G) or UMTS (3G).
For more information about how the feature works and how to configure it, refer to the 3G-2G Location
Change Reporting feature section.
Important
The "Location reporting in connected mode" license is required to enable this functionality.
Accounting Path Framework, New for 14.0
As of Release 14.0, the SGSN uses a new accounting path framework to support PSC3 numbers of 8 million
attached subs and 16 million PDP contexts. In the old accounting path framework, there was one AAA session
per sub-session in the Session manager and one archive session per sub-session in AAA manager. As part of
the new accounting path framework there is only one AAA session per call in the Session manager and one
archive session per call in the AAA manager. Also, there is an additional accounting session in the Session
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AAA Changes To Support Location Services (LCS) Feature
manager and the AAA manager per sub-session. The new accounting path framework improves memory and
CPU utilization and prevents tariff or time limit delay. There are no changes in the CLI syntax to support the
new accounting path and the existing accounting behavior of SGSN is not modified.
AAA Changes To Support Location Services (LCS) Feature
The Location Services (LCS) feature in SGSN provides the mechanism to support mobile location services
for operators, subscribers and third party service providers. AAA changes have been made to support the LCS
feature. A new CDR type Mobile Originated Location Request CDRs (LCS-MO-CDR) is introduced.
LCS-MO-CDRs support the standard dictionaries.
For detailed information on LCS-MO-CDRs, refer to the GTPP Interface Administration and Reference.
APN Aliasing
In many situations, the APN provided in the Activation Request is unacceptable perhaps it does not match
with any of the subscribed APNs or it is misspelled and would result in the SGSN rejecting the Activation
Request. The APN Aliasing feature enables the operator to override an incoming APN specified by a subscriber
or provided during the APN selection procedure (TS 23.060) or replace a missing APN with an
operator-preferred APN.
The APN Aliasing feature provides a set of override functions: Default APN, Blank APN, APN Remapping,
and Wildcard APN to facilitate such actions as:
• overriding a mismatched APN with a default APN.
• overriding a missing APN (blank APN) with a default or preferred APN.
• overriding an APN on the basis of charging characteristics.
• overriding an APN by replacing part or all of the network or operator identifier with information defined
by the operator, for example, MNC123.MCC456.GPRS could be replaced by MNC222.MCC333.GPRS.
• overriding an APN for specific subscribers (based on IMSI) or for specific devices (based on IMEI).
Default APN
Operators can configure a "default APN" for subscribers not provisioned in the HLR. The default APN feature
will be used in error situations when the SGSN cannot select a valid APN via the normal APN selection
process. Within an APN remap table, a default APN can be configured for the SGSN to:
• override a requested APN when the HLR does not have the requested APN in the subscription profile.
• provide a viable APN if APN selection fails because there was no "requested APN" and wildcard
subscription was not an option.
In either of these instances, the SGSN can provide the default APN as an alternate behavior to ensure that
PDP context activation is successful.
Recently, the SGSN\'s default APN functionality was enhanced so that if a required subscription APN is not
present in the subscriber profile, then the SGSN will now continue the activation with another configured
'dummy' APN. The call will be redirected, via the GGSN, to a webpage informing the user of the error and
prompting to subscribe for services.
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APN Redirection per APN with Lowest Context-ID
Refer to the APN Remap Table Configuration Mode in the Command Line Interface Reference for the command
to configure this feature.
APN Redirection per APN with Lowest Context-ID
The APN Redirection per APN with Lowest Context-ID feature adds the flexibility to select the subscription
APN with the least context ID when the APN is not found in the subscription. SGSN already provides
sophisticated APN replacement with support for first-in-subscription, default APN, blank APN, and wildcard
APN. This latest feature works along similar lines providing further flexibility to the operator in allowing
activations when the MS requested APN is incorrect, misspelled, or not present in the subscription.
The SGSN's APN selection procedure is based on 3GPP 23.060 Annex A, which this feature extends based
on CLI controls under the APN Remap Table configuration mode.
APN Resolution with SCHAR or RNC-ID
It is now possible to append charging characteristic information to the DNS string. The SGSN includes the
profile index value portion of the CC as binary/decimal/hexadecimal digits (type based on the configuration)
after the APN network identification. The charging characteristic value is taken from the subscription record
selected for the subscriber during APN selection. This enables the SGSN to select a GGSN based on the
charging characteristics information.
After appending the charging characteristic the DNS string will take the following form:
<apn_network_id>.<profile_index>.<apn_operator_id >. The profile index in the following example has a
value 10: quicknet.com.uk.1010.mnc234.mcc027.gprs.
If the RNC_ID information is configured to be a part of the APN name, and if inclusion of the profile index
of the charging characteristics information is enabled before the DNS query is sent, then the profile index is
included after the included RNC_ID and the DNS APN name will appear in the following form:
<apn_network_id>.<rnc_id>.<profile_index>.<apn_operator_id>. In the following example, the DNS query
for a subscriber using RNC 0321 with the profile index of value 8 would appear as:
quicknet.com.uk.0321.1000.mnc234.mcc027.gprs.
APN Restriction
The reception, storage, and transfer of APN Restriction values is used to determine whether a UE is allowed
to establish PDP Context or EPS bearers with other APNs. This feature is supported by both the Gn/Gp-SGSN
and the S4-SGSN.
During default bearer activation, the SGSN sends the current maximum APN restriction value for the UE to
the GGSN/P-GW in a Create Session Request (CSR). The GGSN/P-GW retains an APN restriction value for
each APN. The UE\'s APN Restriction value determines the type of application data the subscriber is allowed
to send. If the maximum APN restriction of the UE (received in the CSR) and the APN Restriction value of
the APN (for which activation is being request) do not concur, then the GGSN/P-GW rejects activation. The
maximum APN restriction for a UE is the most restrictive based on all already active default EPS bearers.
This feature provides the operator with increased control to restrict certain APNs to UEs based on the type of
APN. This feature requires no special license.
APN Restriction for SGSN is enabled/disabled in the call-control-profile configuration mode using the
apn-restriction command. Refer to the Command Line Interface Reference for usage details.
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Automatic Protection Switching (APS)
Automatic Protection Switching (APS)
Automatic protection switching (APS is now available on an inter-card basis for SONET configured CLC2
(Frame Relay) and OLC2 (ATM) optical line cards. Multiple switching protection (MSP) version of is also
available for SDH configured for the CLC2 and OLC2 (ATM) line cards.
APS/MSP offers superior redundancy for SONET/SDH equipment and supports recovery from card failures
and fiber cuts. APS allows an operator to configure a pair of SONET/SDH lines for line redundancy. In the
event of a line problem, the active line switches automatically to the standby line within 60 milliseconds (10
millisecond initiation and 50 millisecond switchover).
At this time, the Gn/Gp-SGSN supports the following APS/MSP parameters:
• 1+1 - Each redundant line pair consists of a working line and a protection line.
• uni-directional - Protection on one end of the connection.
• non-revertive - Upon restoration of service, this parameter prevents the network from automatically
reverting to the original working line.
The protection mechanism used for the APS/MSP uses a linear 1+1 architecture, as described in the ITU-T
G.841 standard and the Bellcore publication GR-253-CORE, SONET Transport Systems; Common Generic
Criteria, Section 5.3. The connection is unidirectional.
With APS/MSP 1+1, each redundant line pair consists of a working line and a protection line. Once a signal
fail condition or a signal degrade condition is detected, the hardware switches from the working line to the
protection line.
With the non-revertive option, if a signal fail condition is detected, the hardware switches to the protection
line and does not automatically revert back to the working line.
Since traffic is carried simultaneously by the working and protection lines, the receiver that terminates the
APS/MSP 1+1 must select cells from either line and continue to forward one consistent traffic stream. The
receiving ends can switch from working to protection line without coordinating at the transmit end since both
lines transmit the same information.
Figure 4: SONET APS 1+1
Refer to the section on Configuring APS/MSP Redundancy in the SGSN Service Configuration Procedures
section for configuration details.
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Authentications and Reallocations -- Selective
Authentications and Reallocations -- Selective
Subscriber event authentication, P-TMSI reallocation, and P-TMSI signature reallocation are now selective
rather than enabled by default.
The operator can enable and configure them to occur according to network requirements:
• every instance or every nth instance;
• on the basis of UMTS, GPRS or both;
• on the basis of elapsed time intervals between events.
There are situations in which authentication will be performed unconditionally:
• IMSI Attach all IMSI attaches will be authenticated
• When the subscriber has not been authenticated before and the SGSN does not have a vector
• When there is a P-TMSI signature mismatch
• When there is a CKSN mismatch
There are situation in which P-TMSI will be reallocated unconditionally:
• Inter SGSN Attach/RAU
• Inter-RAT Attach/RAU in 2G
• IMSI Attach
Avoiding PDP Context Deactivations
The SGSN can be configured to avoid increased network traffic resulting from bursts of service
deactivations/activations resulting from erroneous restart counter change values in received messages (Create
PDP Context Response or Update PDP Context Response or Update PDP Context Request). Be default, the
SGSN has the responsibility to verify possible GTP-C path failure by issuing an Echo Request/Echo Response
to the GGSN. Path failure will only be confirmed if the Echo Response contains a new restart counter value.
Only after this confirmation of the path failure does the SGSN begin deactivation of PDP contexts.
Backup and Recovery of Key KPI Statistics
This feature allows the backup of a small set of KPI counters for recovery of the counter values after a session
manager crash.
Using the feature-specific CLI statistics-backup sgsn backup-interval command, in the Global configuration
mode, the operator can enable the feature and define the frequency of the backup; range 1-60 minutes.
In support of this functionality, four schemas (gprs-bk, iups-bk, map-bk, sgtp-bk) have been defined with
stats, derived from the SGSN and SGTP schemas, that will be backed up for recovery of their counter values.
For more information about the schema, refer to the Statistics and Counters Reference. For more information
about this functionality and configuration for this feature, refer to the Backup and Recovery of Key KPI
Statistics feature chapter in this Guide.
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Bulk Statistics Support
Bulk Statistics Support
System support for bulk statistics allows operators to choose which statistics to view and to configure the
format in which the statistics are presented. This simplifies the post-processing of statistical data since it can
be formatted to be parsed by external, back-end processors.
When used in conjunction with the Web Element Manager, the data can be parsed, archived, and graphed.
The system can be configured to collect bulk statistics (performance data) and send them to a collection server
(called a receiver). Bulk statistics are statistics that are collected in a group. The individual statistics are
grouped by schema. The following is the list of schemas supported for use by the SGSN:
• System: Provides system-level statistics
• Card: Provides card-level statistics
• Port: Provides port-level statistics
• DLCI-Util: Provides statistics specific to DLCIs utilization for CLC-type line cards
• EGTPC: Provides statistics specific to the configured ETPC service on the S4-SGSN
• GPRS: Provides statistics for LLC, BSSGP, SNDCP, and NS layers
• SCCP: Provides SCCP network layer statistics
• SGTP: Provides SGSN-specific GPRS Tunneling Protocol (GTP) statistics
• SGSN: Provides statistics for: mobility management (MM) and session management (SM) procedures;
as well, MAP, TCAP, and SMS counters are captured in this schema. SGSN Schema statistic availability
is per service (one of: SGSN, GPRS, MAP) and per routing area (RA)
• SS7Link: Provides SS7 link and linkset statistics
• SS7RD: Provides statistics specific to the proprietary SS7 routing domains
The following four schema are used by the SGSN for backed up / recovered counters (for details, see the
Backup and Recovery of Key KPI Statistics section in this guide) :
• iups-bk
• gprs-bk
• map-bk
• sgtp-bk
The system supports the configuration of up to 4 sets (primary/secondary) of receivers. Each set can be
configured with to collect specific sets of statistics from the various schemas. Statistics can be pulled manually
from the chassis or sent at configured intervals. The bulk statistics are stored on the receiver(s) in files.
The format of the bulk statistic data files can be configured by the user. Users can specify the format of the
file name, file headers, and/or footers to include information such as the date, chassis host name, chassis
uptime, the IP address of the system generating the statistics (available for only for headers and footers),
and/or the time that the file was generated.
When the Web Element Manager is used as the receiver, it is capable of further processing the statistics data
through XML parsing, archiving, and graphing.
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Bypassing APN Remap for Specific IMEI Ranges
The Bulk Statistics Server component of the Web Element Manager parses collected statistics and stores the
information in the PostgreSQL database. If XML file generation and transfer is required, this element generates
the XML output and can send it to a Northbound NMS or an alternate bulk statistics server for further
processing.
Additionally, if archiving of the collected statistics is desired, the Bulk Statistics server writes the files to an
alternative directory on the server. A specific directory can be configured by the administrative user or the
default directory can be used. Regardless, the directory can be on a local file system or on an NFS-mounted
file system on the Web Element Manager server.
Bypassing APN Remap for Specific IMEI Ranges
Prior to Release 16, if a local default APN configured in an IMEI profile could not be used, then any default
APN configured under an operator policy was used. Also, only the apn-selection-default CLI option, under
the APN Remap Table configuration associated with an IMEI profile, was valid. Other CLI options such as
apn-remap and blank-apn were not applicable when a remap table was associated with an IMEI profile.
With Release 16, an APN Remap Table associated with an IMEI profile overrides a remap table associated
with an operator policy. This means activation will be rejected if a local default APN configured, in an APN
Remap Table associated with an IMEI profile, cannot be used. This will occur even if a valid local default
APN is available in an APN Remap Table associated with an operator policy.
To achieve the previous default behavior, customers already using an APN Remap Table that is associated
with an IMEI profile will have to change the existing configuration to achieve the previous behavior. For
details and sample configurations, see the Release 16 specific information for apn-selection-default in
the APN Remap Table Configuration Mode Commands section of the Command Line Interface Reference
for a Release 16 or higher.
Important
CAMEL Service Phase 3, Ge Interface
The SGSN provides PDP session support as defined by Customized Applications for Mobile network Enhanced
Logic (CAMEL) phase 3.
CAMEL Service
CAMEL service enables operators of 2.5G/3G networks to provide operator-specific services (such as prepaid
GPRS service and prepaid SMS service) to subscribers, even when the subscribers are roaming outside their
HPLMN.
CAMEL Support
SGSN support for CAMEL phase 3 services expands with each SGSN application release. Current support
enables operators of 2.5G/3G networks to provide operator-specific services (such as prepaid GPRS service
and prepaid SMS service) to subscribers, even when the subscribers are roaming outside their HPLMN.
For this release the SGSN has expanded its support for CAMEL Scenario 1 adding:
• Implementation of Scenario1 triggers (TDP-Attach, TDP-Attach-ChangeofPosition)
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CAMEL Service Phase 3, Ge Interface
• Implementation of Scenario1 Dynamic triggers (DP-Detach, DP-ChangeofPosition)
• Expanded conformance to 3GPP spec 23.078 (Release 4)
The SGSN supports the following GPRS-related functionality in CAMEL phase 3:
• Control of GPRS PDP contexts
Functional support for CAMEL interaction includes:
• PDP Context procedures per 3GPP TS 29.002
◦GPRS TDP (trigger detection point) functions
◦Default handling codes, if no response received from SCP
◦GPRS EDP (event detection points) associated with SCP
◦Charging Procedures: Handle Apply Charging GPRS & Handle Apply Charging Report GPRS
• "GPRS Dialogue scenario 2" for CAMEL control with SCP
• CAMEL-related data items in an S-CDR:
◦SCF Address
◦Service Key
◦Default Transaction Handling
◦Level of CAMEL service (phase 3)
• Session Recovery for all calls have an ESTABLISHED CAMEL association.
Ge Interface
The SGSN\'s implementation of CAMEL uses standard CAP protocol over a Ge interface between the SGSN
and the SCP. This interface can be deployed over SS7 or SIGTAN.
The SGSN's Ge support includes use of the gprsSSF CAMEL component with the SGSN and the gsmSCF
component with the SCP.
CAMEL Configuration
To provide the CAMEL interface on the SGSN, a new service configuration mode, called "CAMEL Service",
has been introduced on the SGSN.
1 An SCCP Network configuration must be created or exist already.
2 A CAMEL Service instance must be created.
3 The CAMEL Service instance must be associated with either the SGSN Service configuration or the GPRS
Service configuration in order to enable use of the CAMEL interface.
4 The CAMEL Service must be associated with the SCCP Network configuration.
Until a CAMEL Service is properly configured, the SGSN will not process any TDP for pdp-context or
mo-sms.
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Commandguard
For configuration details, refer to the Serving GPRS Support Node Administration Guide and the Command
Line Interface Reference.
Commandguard
Operators can accidentally enter configuration mode via CLI or file replay. To protect against this, SGSN
supports commandguard CLI command. Commandguard, which is disabled by default, can only be enabled
or disabled from the Global Configuration mode. When Commandguard is enabled it affects the configure
and autoconfirm CLI commands by causing them to prompt (Y/N) for confirmation. When autoconfirm is
enabled Commandguard has no affect. The commandguard state is preserved in the SCT and, when enabled,
is output by the various variants of the show config CLI.
Configurable RAB Asymmetry Indicator in RAB Assignment Request
The SGSN sets the value for the RAB Asymmetry Indicator that is included in the RAB Assignment Request.
In releases prior to R12.0, the SGSN set the RAB asymmetry indicator to "Symmetric-Bidirectional" when
downlink and uplink bit rates were equal. Now, the SGSN selects the value based on the symmetry of negotiated
maximum bit rates as follows:
• If the uplink and downlink bit rates are equal then it is set to "Symmetric-Bidirectional",
• If uplink bit rate is set to 0 kbps, then it is set to "Asymmetric-Unidirectional-Downlink",
• If downlink bit rate is set to 0 kbps, then it is set to "Asymmetric-Unidirectional-Uplink",
• If the uplink and downlink bit rates are non-zero and different, then it is set to "Asymmetric-Bidirectional".
A change in CLI configuration allows the SGSN to override the above functionality and set the RAB Asymmetry
Indicator to "Asymmetric-Bidirectional" when uplink and downlink bit rates are equal. As a result, two sets
of bit rates - one for downlink and one for uplink - will be included in the RAB Assignment Requests as
mandated in 3GPP TS 25.413.
Congestion Control
With Release 17, the SGSN supports several of the 3GPP TS23.060 R10 machine type communications (MTC)
overload control mechanisms to be used in the handling of signaling bursts from machine-to-machine (M2M)
devices:
• General congestion control applicable only for Mobility Management messages.
• APN-based congestion control for Mobility Management
• APN-based congestion control for Session Management
• Extended T3312 timer support
• MM (Mobility Management) T3346 - MM Back-off Timer and SM (Session Management) T3396 - SM
Back-off Timer
For more information about the congestion control functionality and configuration, refer to the MTC Congestion
Control section in this Guide.
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Different NRIs for Pooled and Non-pooled RNCs/BSCs
Different NRIs for Pooled and Non-pooled RNCs/BSCs
The SGSN adds support for configuring different NRIs for pooled and non-pooled areas in order to load-balance
subscribers coming from non-pooled RNCs to pooled RNCs.
Consider a scenario when two SGSNs support pooling and a RNC/BSC controlled by a SGSN is in pool but
not the other, and both RNCs/BSCs are given same NRI(s), this leads to imbalance in subscriber distribution
between the SGSNs. With this enhancement if an NRI is configured for both pooled and non-pooled, then
the SGSN reuses the same NRI when moving from pooled to non-pooled areas and vice versa.
A new keyword non-pooled-nri-value is introduced in the NRI configuration for GPRS and SGSN services
to configure set of NRI which should be used for non-pooled RNCs/BSCs. The NRIs configured under the
existing keyword nri-value will be used for pooled RNCs/BSCs. If the new keyword non-pooled-nri-value
is not configured, then NRIs configured under the keyword nri-value will be used for both pooled and
non-pooled RNCs/BSCs.
If the new keyword non-pooled-nri-value is configured without pooling enabled at SGSN(null-nri-value is
not configured), then SGSN will use NRIs under non-pooled-nri-value irrespective of BSC/RNCs being
pooled or non-pooled, till pooling is enabled at SGSN. After pooling is enabled, NRIs under keyword nri-value
will be for pooled RNC/BSCs and non-pooled-nri-value will be for non-pooled RNC/BSCs. This is applicable
for both SGSN and GPRS service.
Direct Tunnel
In accordance with standards, one tunnel functionality enables the SGSN to establish a direct tunnel at the
user plane level - a GTP-U tunnel, directly between the RAN and the GGSN. Feature details and configuration
procedures are provided in the Direct Tunnel feature section in this guide.
Direct Tunnel Support on the S4-SGSN
Direct tunnelling of user plane data between the RNC and the S-GW can be employed to scale UMTS system
architecture to support higher traffic rates. The direct tunnel (DT) approach optimizes core architecture without
impact to UEs and can be deployed independently of the LTE/SAE architecture.
Now, DT support is added to the S4-SGSN to enable the establishment of a direct tunnel over the S12 interface
between an RNC and an S-GW in a PS domain under a range of scenarios, such as (but not limited to):
• Primary PDP activation
• Secondary PDP activation
• Service Request Procedure
• Intra SGSN Routing Area Update without SGW change
• Intra SGSN Routing Area Update with SGW change
• Intra SGSN SRNS relocation without SGW change
• Intra SGSN SRNS relocation with SGW change
• New SGSN SRNS relocation with SGW change
• New SGSN SRNS relocation without SGW relocation
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Downlink Data Lockout Timer
• E-UTRAN to UTRAN Iu mode IRAT handover - with application of S12U FTEID for Indirect Data
Forwarding Tunnels as well
• UTRAN to E-UTRAN Iu mode IRAT handover - with application of S12U FTEID for Indirect Data
Forwarding Tunnels as well
• Network-Initiated PDP Activation
The Direct Tunnel Support on the S4-SGSN feature is license controlled. Contact your Cisco Account or
Support representative for information on how to obtain a license.
For a complete description of this feature and its configuration requirements, refer to the S4-SGSN Direct
Tunnel Solution session in the Serving GPRS Support Node Administration Guide.
Downlink Data Lockout Timer
The Downlink Data Lockout Timer is a new, configurable timer added for both GPRS and SGSN services to
reduce the frequency of mobile-initiated keep alive messages. If enabled, this timer starts whenever the paging
procedure fails after the maximum number of retransmissions and the Page Proceed Flag (PPF) is cleared. If
there is any downlink activity when the lockout timer is running, the packets are dropped and the drop cause
is set as Page Failed. When the lockout timer expires, the PPF is set to true and further downlink packets are
queued and paging is re-initiated. In order to avoid endless paging activity when there is no page response or
uplink activity from the UE, an optional configurable repeat count value is used. If the repeat value is configured
as 'y' then the lockout timer is started 'y' number of times after page failure. The implementation of the lockout
timer is different for 2G/3G subscribers, but the behavior is the same.
DSCP Templates for Control and Data Packets - Iu or Gb over IP
The SGSN supports a mechanism for differentiated services code point (DSCP) marking of control packets
and signaling messages for the SGSN\'s M3UA level on the Iu interface and for LLC messages for the Gb
interface.
This DSCP marking feature enables the SGSN to perform classifying and managing of network traffic and
to determine quality of service (QoS) for the interfaces to an IP network.
Implementation of this feature requires the use of several CLIs commands to create one or more reusable
templates. These templates set DSCP parameter configuration for downlink control packets and data packets
that can be associated with one or more configurations for at the GPRS service level, the peer-NSEI level,
the IuPS service level, and the PSP instance level.
Dual PDP Addresses for Gn/Gp
In accordance with 3GPP Release 9.0 specifications, it is now possible to configure SGSN support for dual
stack PDP type addressing (IPv4v6) for PDP context association with one IPv4 address and one IPv6
address/prefix when requested by the MS/UE.
ECMP over ATM
Iu Redundancy is the ASR 5000's implementation of equal-cost multi-path routing (ECMP) over ATM.
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EDR Enhancements
Iu Redundancy is based on the standard ECMP multi-path principle of providing multiple next-hop-routes of
equal cost to a single destination for packet transmission. ECMP works with most routing protocols and can
provide increased bandwidth when traffic load-balancing is implemented over multiple paths.
ECMP over ATM will create an ATM ECMP group when multiple routes with different destination ATM
interfaces are defined for the same destination IP address. When transmitting a packet with ECMP, the NPU
performs a hash on the packet header being transmitted and uses the result of the hash to index into a table of
next hops. The NPU looks up the ARP index in the ARP table (the ARP table contains the next-hop and egress
interfaces) to determine the next-hop and interface for sending packets.
EDR Enhancements
A new event-logging handle has been introduced. In earlier releases the EDR module was used for event
logging purpose, from this release onwards CDR_MODULE_EVENT_RECORD is used instead of
CDR_MODULE_EDR. In Release 12.0, for generating event logs the SGSN re-used the existing \'EDR"
module which is primarily used for charging records. But from Release 15.0 onwards, the session-event
module will be used by SGSN for event logging. The CLI options present under the EDR Module are also
present under the Session Event Module.
EIR Selection for Roaming Subscribers
EIR selelction for roaming subscribers functionality makes it possible for the SGSN to select an EIR based
on the PLMN into which the subscriber has roamed and reduce signalling back to home PLMNs for roamers.
The Equipment Identity Register (EIR), used for authentication and authorization during an Attach, is the
carrier's IMEI(SV) database of the unique numbers allocated to each subscriber\'s mobile station equipment
(IMEI) and the manufacturer\'s software version (SV). An IMEI(SV) can be in one of three lists in the EIR:
• white list - the subscriber equipment is permitted access
• black list - the subscriber equipment is not permitted access
• grey list - the subscriber equipment is being tracked for evaluation or other purposes
As part of this function, the operator can create and use an EIR profile to define the parameters to:
• use a single EIR address for multiple EIRs,
• achieve the Check-IMEI-Request, and
• associate the EIR profile with a call control profile.
Equivalent PLMN
This feature is useful when an operator deploys both GPRS and UMTS access in the same radio area and each
radio system broadcasts different PLMN codes. It is also useful when operators have different PLMN codes
in different geographical areas, and the operators\' networks in the various geographical areas need to be
treated as a single HPLMN.
This feature allows the operator to consider multiple PLMN codes for a single subscriber belonging to a single
home PLMN (HPLMN). This feature also allows operators to share infrastructure and it enables a UE with a
subscription with one operator to access the network of another operator.
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First Vector Configurable Start for MS Authentication
First Vector Configurable Start for MS Authentication
Previously, the SGSN would begin authentication towards the MS only after the SGSN received all requested
vectors. This could result in a radio network traffic problem when the end devices timed out and needed to
re-send attach requests.
Now, the SGSN can be configured to start MS authentication as soon as it receives the first vector from the
AuC/HLR while the SAI continues in parallel. After an initial attach request, some end devices restart
themselves after waiting for the PDP to be established. In such cases, the SGSN restarts and a large number
of end devices repeat their attempts to attach. The attach requests flood the radio network, and if the devices
timeout before the PDP is established then they continue to retry, thus even more traffic is generated. This
feature reduces the time needed to retrieve vectors over the GR interface to avoid the high traffic levels during
PDP establishment and to facilitate increased attach rates.
Format Encoding of MNC and MCC in DNS Queries Enhanced
In order to provide effective control on DNS queries for particular type of procedures, existing CLI commands
in GPRS and SGSN services have been deprecated and replaced with new enhanced commands. The command
dns israu-mcc-mnc-encoding [hexadecimal | decimal] has been deprecated and a new CLI command dns
mcc-mnc-encoding { rai-fqdn | apn-fqdn | rnc-fqdn| mmec-fqdn| tai-fqdn}* {a-query | snaptr-query }*
{ decimal | hexadecimal }. New keyword options snaptr-query and a-Query are provided to control different
types of queries.
To ensure backward compatibility:
1 If the command dns israu-mcc-mnc-encoding decimal is executed, it will be auto converted to dns
mcc-mnc-encoding rai-fqdn a-query snaptr-query decimal.
2 If the command dns israu-mcc-mnc-encoding hexadecimal is executed, it will be auto converted to dns
mcc-mnc-encoding rai-fqdn a-query snaptr-query hexadecimal
For more information see, Command Line Interface Reference.
Gb Manager
A new SGSN proclet has been developed. Now, all the link level procedures related to Gb • protocol (GPRS-NS and BSSGP) hosting, handling, administration, message distribution,
• keeping the other managers informed about the link/remote-node status,
• handling functionality of the Gb interface (all 2G signaling)
are removed from the Link Manager and moved to the SGSN's new Gb Manager proclet.
The new Gb Manager provides increased flexibility in handling link level procedures for each access type
independently and ensures scalability. The consequence of relieving the Link Manager, of a large amount of
message handling, is to decrease delays in sending sscop STAT messages resulting in the detection of link
failure at the remote end. Use of this separate new proclet to handle 2G signaling messages means there will
not be any MTP link fluctuation towards the RNS, which is seen during the BSC restart or extension activity
in the network. As well, this improves the fluctuation towards the 3G connectivity.
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GMM-SM Event Logging
GMM-SM Event Logging
To facilitate troubleshooting, the SGSN will capture procedure-level information per 2G or 3G subscriber
(IMSI-based) in CSV formatted event data records (EDRs) that are stored on an external server.
This feature logs the following events:
• Attaches
• Activation of PDP Context
• RAU
• ISRAU
• Deactivation of PDP Context
• Detaches
• Authentications
• PDP Modifications
The new SGSN event logging feature is enabled/disabled per service via CLI commands. For more information
on this feature, refer to the section GMM/SM Event Logging in this guide.
Gn/Gp Delay Monitoring
The SGSN measures the control plane packet delay for GTP-C signaling messages on the SGSN\'s Gn/Gp
interface towards the GGSN.
If the delay crosses a configurable threshold, an alarm will be generated to prompt the operator.
A delay trap is generated when the GGSN response to an ECHO message request is delayed more than a
configured amount of time and for a configured number of consecutive responses. When this occurs, the
GGSN will be flagged as experiencing delay.
A clear delay trap is generated when successive ECHO Response (number of successive responses to detect
a delay clearance is configurable), are received from a GGSN previously flagged as experiencing delay.
This functionality can assist with network maintenance, troubleshooting, and early fault discovery.
GTP-C Path Failure Detection and Management
The SGSN now provides the ability to manage GTP-C path failures detected as a result of spurious restart
counter change messages received from the GGSN.
Previous Behavior: The old default behavior was to have the Session Manager (SessMgr) detect GTP-C path
failure based upon receiving restart counter changes in messages (Create PDP Context Response or Update
PDP Context Response or Update PDP Context Request) from the GGSN and immediately inform the SGTPC
Manager (SGTPCMgr) to pass the path failure detection to all other SessMgrs so that PDP deactivation would
begin.
New Behavior: The new default behavior has the SessMgr inform the SGTPCMgr of the changed restart
counter value. The SGTPCMgr now has the responsibility to verify a possible GTP-C path failure by issuing
an Echo Request/Echo Response to the GGSN. Path failure will only be confirmed if the Echo Response
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GTPv0 Fallback, Disabling to Reduce Signalling
contains a new restart counter value. Only after this confirmation of the path failure does the SGTPCMgr
inform all SessMgrs so that deactivation of PDP contexts begins.
GTPv0 Fallback, Disabling to Reduce Signalling
GTPv0 fallback can cause unnecessary signaling on the Gn/Gp interface in networks where all the GGSNs
support GTPv1.
By default, the SGSN supports GTPv0 fallback and uses either GTPv1 or GTPv0. After exhausting all
configured retry attempts for GTPv1, the SGSN retries the GTP-C Request using GTPv0. This fallback is
conditional and is done only when the GTP version of a GGSN is unknown during the first attempt at activating
a PDP context with the GGSN.
It is possible for the operator to disable the GTPv0 fallback for requests to GGSNs of specific APNs. Disabling
the fallback function is configured under the APN profile and is applicable for GGSNs corresponding to that
APN. If GTPv1 only is enabled in the APN profile, then the SGSN does not attempt fallback to GTPv0
(towards GGSNs corresponding to that APN) after all GTPv1 retries have been attempted. If more than one
GGSN address is returned by the DNS server during activation, then the SGSN attempts activation with the
next GGSN after exhausting all the GTPv1 retry attempts. If only one GGSN address is returned, then the
SGSN rejects the activation after exhausting all the configured GTPv1 retries.
This change enables the operator to prevent unnecessary signaling on the Gn/Gp interface in networks where
all the GGSNs support GTPv1. For example, if all the home GGSNs in an operator\'s network support GTPv1,
then the unnecessary GTPv0 fallabck can be avoided by enabling this feature for the APNs associated with
home GGSNs.
Handling Multiple MS Attaches All with the Same Random TLLI
Some machine-to-machine (M2M) devices from the same manufacturer will all attempt PS Attaches using
the same fixed random Temporary Logical Link Identifier (TLLI).
The SGSN cannot distinguish between multiple M2M devices trying to attach simultaneously using the same
random TLLI and routing area ID (RAI). As a result, during the attach process of an M2M device, if a second
device tries to attach with the same random TLLI, the SGSN interprets that as an indication that the original
subscriber moved during the Attach process and the SGSN starts communicating with the second device and
drops the first device.
The SGSN can be configured to allow only one subscriber at a time to attach using a fixed random TLLI.
While an Attach procedure with a fixed random TLLI is ongoing (that is, until a new P-TMSI is accepted by
the MS), all other attaches sent to the SGSN with the same random TLLI using a different IMSI will be
dropped by the SGSN\'s Linkmgr.
To limit the wait-time functionality to only the fixed random TLLI subscribers, the TLLI list can be configured
to control which subscribers will be provided this functionality.
HSPA Fallback
Besides enabling configurable support for either 3GPP Release 6 (HSPA) and 3GPP Release 7 (HSPA+) to
match whatever the RNCs support, this feature enables configurable control of data rates on a per RNC basis.
This means that operators can allow subscribers to roam in and out of coverages areas with different QoS
levels.
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Ignore Context-ID during 4G/3G Handovers
The SGSN can now limit data rates (via QoS) on a per-RNC basis. Some RNCs support HSPA rates (up to
16 Mbps in the downlink and 8 Mbps in the uplink) and cannot support higher data rates - such as those
enabled by HSPA+ (theoretically, up to 256 Mbps both downlink and uplink). Being able to specify the QoS
individually for each RNC makes it possible for operators to allow their subscribers to move in-and-out of
coverage areas with different QoS levels, such as those based on 3GPP Release 6 (HSPA) and 3GPP Release
7 (HSPA+).
For example, when a PDP context established from an RNC with 21 Mbps is handed off to an RNC supporting
only 16 Mbps, the end-to-end QoS will be re-negotiated to 16 Mbps. Note that an MS/UE may choose to drop
the PDP context during the QoS renegotiation to a lower value.
This data rate management per RNC functionality is enabled, in the radio network controller (RNC)
configuration mode, by specifying the type of 3GPP release specific compliance, either release 7 for HSPA+
rates or pre-release 7 for HSPA rates. For configuration details, refer to the RNC Configuration Mode section
in the Command Line Interface Reference.
Ignore Context-ID during 4G/3G Handovers
HSS and HLR, when operating as separate network nodes, are required to use the same context-ID for a given
APN-configuration of a subscriber. During inter-RAT cell reselections and handovers between 2G/3G and
4G, if the SGSN does not find a matching APN-configuration for the given context-ID learnt from the peer
node, then the PDP does not get established. This could result in SRNS relocation failures when none of the
PDP's learnt from the SGSN has a matching context-ID in the HLR.
New commands have been added to enable the operator to configure the SGSN to ignore the context-ID
provided by the peer and to use the PDP- type and address information to search through HLR subscription
and to update the context-ID information within the PDP. For details, refer to the description for the rau-inter
command under the Call-Control Profile Configuration Mode Commands section of the Command Line
Interface Reference.
Interface Selection Based on UE Capability
The SGSN selects S6d/Gr interface based on whether hss-peer-service or map service is associated with the
SGSN or GPRS service. If both the services are associated, then the selection is made based on configuration
of the CLI command prefer subscription-interface under the Call Control Profile mode. With this feature
enhancement, the SGSN now allows selection of S6d/ Gr interface only if the UE is EPC capable. A new CLI
option epc-ue is added to the command prefer subscription-interface under the Call Control Profile mode
for this enhancement. If this keyword is configured the S6d/Gr interface is selected only if UE is EPC capable.
If this keyword is not configured the SGSN selects the S6d/Gr interface based on whether hss-peer-service
or map service is associated with the SGSN or GPRS service (this is also the default behavior). The interface
selection based on UE capability is done only at the time of Attach / new SGSN RAU / SRNS. Interface
selected during Attach / new SGSN RAU / SRNS may change while doing inter PLMN RAU (intra SGSN)
procedures.
Intra- or Inter-SGSN Serving Radio Network Subsystem (SRNS) Relocation
(3G only)
Implemented according to 3GPP standard, the SGSN supports both inter- and intra-SGSN RNS relocation
(SRNS) to enable handover of an MS from one RNC to another RNC.
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Lawful Intercept
The relocation feature is triggered by subscribers (MS/UE) moving from one RNS to another. If the originating
RNS and destination RNS are connected to the same SGSN but are in different routing areas, the behavior
triggers an intra-SGSN Routing Area Update (RAU). If the RNS are connected to different SGSNs, the
relocation is followed by an inter-SGSN RAU. This feature is configured through the Call-Control Profile
Configuration Mode which is part of the feature set.
Lawful Intercept
The Cisco Lawful Intercept feature is supported on the SGSN. Lawful Intercept is a license-enabled,
standards-based feature that provides telecommunications service providers with a mechanism to assist law
enforcement agencies in monitoring suspicious individuals for potential illegal activity. SGSN supports use
of IP Security (a separate license-enabled, standards-based feature) for the LI interface; for additional
information on IPSec, refer to the Cisco StarOS IP Security (IPSec) Reference. For additional information
and documentation on the Lawful Intercept feature, contact your Cisco account representative.
Lawful Interception Capacity Enhanced
In a full ASR5K chassis with PSC2 cards the maximum number of attached users is about "4" million. In
previous releases, it was possible to configure and intercept 20000 camp-on users on the chassis. With this
feature enhancement the lawful interception capacity of has been increased to 4 of the maximum number of
attached users, that is 160,000 camp-on users (4 of 4 million subscribers). It is now possible to configure and
intercept 160000 camp-on users on the chassis.
Link Aggregation - Horizontal
The SGSN supports enhanced link aggregation (LAG) within ports on different XGLCs. Ports can be from
multiple XGLCs. LAG works by exchanging control packets (Link Aggregation Control Marker Protocol)
over configured physical ports with peers to reach agreement on an aggregation of links. LAG sends and
receives the control packets directly on physical ports attached to different XGLCs. The link aggregation
feature provides higher aggregated bandwidth, auto-negotiation, and recovery when a member port link goes
down.
Local DNS
Previously, the SGSN supported GGSN selection for an APN only through operator policy, and supported a
single pool of up to 16 GGSN addresses which were selected in round robin fashion.
The SGSN now supports configuration of multiple pools of GGSNs; a primary pool and a secondary. As part
of DNS resolution, the operator can use operator policies to prioritize local GGSNs versus remote ones. This
function is built upon existing load balancing algorithms in which weight and priority are configured per
GGSN, with the primary GGSN pool used first and the secondary used if no primary GGSNs are available.
The SGSN first selects a primary pool and then GGSNs within that primary pool; employing a round robin
mechanism for selection. If none of the GGSNs in a pool are available for activation, then the SGSN proceeds
with activation selecting a GGSN from a secondary pool on the basis of assigned weight. A GGSN is considered
unavailable when it does not respond to GTP Requests after a configurable number of retries over a configurable
time period. Path failure is detected via GTP-echo.
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Local Mapping of MBR
Local Mapping of MBR
The SGSN provides the ability to map a maximum bit rate (MBR) value (provided by the HLR) to an HSPA
MBR value.
The mapped value is selected based on the matching MBR value obtained from the HLR subscription. QoS
negotiation then occurs based on the converted value.
This feature is available within the operator policy framework. MBR mapping is configured via new keywords
added to the qos class command in the APN Profile configuration mode. A maximum of four values can be
mapped per QoS per APN.
Important
To enable this feature the qos prefer-as-cap, also a command in the APN Profile configuration mode,
must be set to either both-hlr-and-local or to hlr subscription.
Local QoS Capping
The operator can configure a cap or limit for the QoS bit rate.
The SGSN can now be configured to cap the QoS bit rate parameter when the subscribed QoS provided by
the HLR is lower than the locally configured value.
Depending upon the keywords included in the command, the SGSN can:
• take the QoS parameter configuration from the HLR configuration.
• take the QoS parameter configuration from the local settings for use in the APN profile.
• during session establishment, apply the lower of either the HLR subscription or the locally configured
values.
Refer to the APN Profile Configuration Mode section of the Command Line Interface Reference for the qos
command.
Location Change Reporting on the S4-SGSN
3G/2G Location Change Reporting on the SGSN facilitates location-based charging on the P-GW by providing
the UE\'s location information when the UE is in connected mode.
The Gn-SGSN supports 2G and 3G location change reporting via user location information (ULI) reporting
to the GGSN. For details, see the feature section 3G-2G Location Change Reporting.
With Release 16.0, the S4-SGSN also supports 2G and 3G location change reporting per 3GPP 29.274 release
11.b, if the P-GW requests it. With this feature enhancement configured, the S4-SGSN is ready to perform
ULI reporting per PDN connection via GTPv2. Reporting only begins after the S4-SGSN receives a reporting
request from the P-GW. The P-GW generates a request based on charging enforcement and policy enforcement
from the policy and charging rules function PCRF. Location Change Reporting is configured and
enabled/disabled per APN.
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Location Services
The S4-SGSN\'s version of Location Change Reporting has been further enhanced with a network sharing
option. If the network sharing license is installed and if the network sharing feature is enabled, then the operator
can configure which PLMN information the SGSN sends to the P-GW in the ULI or Serving Network IEs.
Important
The S3/S4 license is required to enable S4 functionality. The new "Location-reporting in connected-mode"
license is required to enable Location Change Reporting functionality for the S4-SGSN. This new license
is now required for Location Change Reporting on the Gn-SGSN.
Location Services
Location Services (LCS) on the SGSN is a 3GPP standards-compliant feature that enables the SGSN to collect
and use or share location (geographical position) information for connected UEs in support of a variety of
location services, such as location-based charging and positioning services.
The SGSN uses the Lg interface to the gateway mobile location center (GMLC), which provides the mechanisms
to support specialized mobile location services for operators, subscribers, and third party service providers.
Use of this feature and the Lg interface is license controlled. This functionality is supported on the 2G and
3G SGSN.
For details about basic location services and its configuration, refer to the Location Services section of the
SGSN Administration Guide.
With Release 15.0, supported functionality has expanded to include:
• Mobile terminating deferred location requests are now supported
• Mobile originating requests are now supported, both immediate and deferred
• Differences between 2G and 3G LCS call flows are eliminated
Important
With this release, expanded functionality for this feature is qualified for lab and field trials only.
Lock/Shutdown the BSC from the SGSN
When the SGSN returns to Active state, after scenarios such as rebooting or reloading, all the BSCs that had
been connected to the SGSN would attempt to re-establish connections. This could result in two serious
problems for operators:
1 High CPU usage in the SGSN where too many BSC/RNCs were connected.
2 Network overload when other network nodes cannot match the SGSN's capacity.
The SGSN now supports a Lock/Shutdown feature that provides a two prong solution. CPU Usage Solution:
Staggering the BSC auto-learning procedures when the SGSN re-loads will help to reduce the high CPU
usage. This can be achieved by the operator locking the NSE/BSCs from the SGSN before reboot/reload and
then unlocking them one-by-one to avoid high CPU usage.
Network Overload Solution: A new timer, SNS-GUARD, has been added to clean-up resources if the SNS
procedure does not complete properly, whether or not the BSC is administratively locked. Now the SGSN
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Multiple PLMN Support
starts this timer after sending SNS-SIZE-ACK and the BSC information will be removed, if the auto-learning
clean-up procedure does not complete before the timer expires.
A series of new commands and keywords has been added to enable the operator to configure this new
administrative Lock/Shutdown the BSC functionality as part of 'interface management' configuration. For
details, refer to the SGSN Global Interface Management section of the Command Line Interface Reference.
Multiple PLMN Support
With this feature, the 2.5G and 3G SGSNs now support more than one PLMN ID per SGSN. Multiple PLMN
support facilitates MS handover from one PLMN to another PLMN.
Multiple PLMN support also means an operator can 'hire out' their infrastructure to other operators who may
wish to use their own PLMN IDs. As well, multiple PLMN support enables an operator to assign more than
one PLMN ID to a cell-site or an operator can assign each cell-site a single PLMN ID in a multi-cell network
(typically, there are no more than 3 or 4 PLMN IDs in a single network).
This feature is enabled by configuring, within a single context, multiple instances of either an IuPS service
for a single 3G SGSN service or multiple GPRS services for a 2.G SGSN. Each IuPS service or GPRS service
is configured with a unique PLMN ID. Each of the SGSN and/or GPRS services must use the same MAP,
SGTPU and GS services so these only need to be defined one-time per context.
Network Sharing
In accordance with 3GPP TS 23.251, the 2G and 3G SGSN provides an operator the ability to share the RAN
and/or the core network with other operators. Depending upon the resources to be shared, there are 2 network
sharing modes of operation: the Gateway Core Network (GWCN) and the Multi-Operator Core Network
(MOCN).
Benefits of Network Sharing
Network sharing provides operators with a range of logistical and operational benefits:
• Enables two or more network operators to share expensive common network infrastructure.
• A single operator with multiple MCC-MNC Ids can utilize a single physical access infrastructure and
provide a single HPLMN view to the UEs.
• Facilitates implementation of MVNOs.
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Network Sharing
GWCN Configuration
For the 3G SGSN with a gateway core network configuration, the complete radio access network and part of
the core network are shared (for example, MSC/SGSN) among different operators, while each operator
maintains its own separate network nodes (for example, GGSN/HLR).
Figure 5: GWCN-type Network Sharing
With the GWCN configuration, the SGSN supports two scenarios:
• GWCN with non-supporting UE
• GWCN with supporting UE
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Network Sharing
MOCN Configuration
In the multi-operator core network configuration, the complete radio network is shared among different
operators, while each operators maintains its own separate core network. This functionality is available for
both 2G and 3G SGSN.
Figure 6: MOCN-type Network Sharing
With the MOCN configuration, the SGSN supports the following scenarios:
• MOCN with non-supporting UE
• MOCN with supporting UE
The MOCN network sharing functionality now requires a separate feature license for both 2G and 3G
scenarios. Contact your Cisco representative for licensing information.
Important
Implementation
To facilitate network sharing, the SGSN implements the following key features:
• Multiple virtual SGSN services in a single physical node.
• Sharing operators can implement independent policies, such as roaming agreements.
• Equivalent PLMN configuration.
• RNC identity configuration allows RNC-ID + MCC-MNC instead of just RNC-ID.
Configuration for network sharing is accomplished by defining:
• NRI in the SGSN service configuration mode
• PLMN IDs and RNC IDs in the IuPS configuration mode
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NRI-FQDN based DNS resolution for non-local RAIs (2G subscribers)
• Equivalent PLMN IDs and configured in the Call-Control Profile configuration mode.
• IMSI ranges are defined in the SGSN-Global configuration mode
• The Call-Control Profile and IMSI ranges are associated in the configuration mode.
For commands and information, refer to the 2G SGSN Multi-Operator Core Network section in the Serving
GPRS Support Node Administration Guide and the command details in the Command Line Interface Reference.
NRI-FQDN based DNS resolution for non-local RAIs (2G subscribers)
The SGSN now supports use of NRI-RAI based address resolution which includes both local lookup as well
as DNS Query for non-local RAIs when selection of the call control profile is based on the old-RAI and the
PLMN Id of the BSC where the subscriber originally attached. This feature was formerly supported only for
3G subscribers and is now extended to 2G subscribers. The command enables the SGSN to perform address
resolution for peer SGSN with an NRI when an unknown PTMSI (Attach or RAU) comes from an SGSN
outside the pool. The SGSN uses NRI-RAI based address resolution for the non-local RAIs for 2G subscribers
in place of RAI based address resolution.
This functionality is applicable in situations for either inter- or intra-PLMN when the SGSN has not chosen
a local NRI value (configured with SGSN Service commands) other than local-pool-rai or nb-rai. This means
the RAI (outside pool but intra-PLMN) NRI length configured here will be applicable even for intra-PLMN
with differently configured NRI lengths (different from the local pool). This functionality is not applicable
to call control profiles with an associated MSIN range as ccprofile selection is not IMSI-based.
NRI Handling Enhancement
The SGSN's DNS lookup for SGSN pooling is supported in the call control profile. Previously, the SGSN's
complete Gn DNS database had to be configured in the call control profile. If there was more than one SGSN
in the local pool, then there would be multiple instances for every SGSN in the pool.
By using just the NRI value, this enhancement facilitates lookup for a peer SGSN in the local pool.
NRPCA - 3G
The SGSN supports the Network Requested Primary PDP Context Activation (NRPCA) procedure for 3G
attachments.
There are no interface changes to support this feature. Support is configured with existing CLI commands
(network-initiated-pdp-activation, location-area-list) in the call control profile configuration mode and timers
(T3385-timeout and max-actv-retransmission) are set in the SGSN service configuration mode. For command
details, see the Command Line Interface Reference
NRSPCA Support for S4-SGSN
The SGSN supports Secondary PDP context activation by the network. 3GPP TS 23.060 specifies two
procedures for GGSN-initiated PDP Context Activation:
• Network Requested PDP Context Activation (NRPCA) - the SGSN already supports this but only for
3G access, and
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Operator Policy
• Network Requested Secondary PDP Context Activation (NRSPCA) Procedure.
NRSPCA allows the network to initiate Secondary PDP context activation if the network determines that the
service requested by the user requires activation of an additional secondary PDP context. Network requested
bearer control makes use of the NRSPCA procedure.
Network requested bearer control functionality is mandatory in EPC networks, requiring use of NRSPCA.
The P-GW supports only the NRSPCA procedure. With this release, now the S4-SGSN supports network
requested bearer control.
For a complete description of this feature and its configuration requirements, refer to the Network Requested
Secondary PDP Context Activation chapter in the Serving GPRS Support Node Administration Guide
Operator Policy
This non-standard feature is unique to the StarOS. This feature empowers the carrier with unusual and flexible
control to manage functions that are not typically used in all applications and to determine the granularity of
the implementation of any: to groups of incoming calls or to simply one single incoming call. For details
about the feature, its components, and how to configure it, refer to the Operator Policy section in this guide.
Important
SGSN configurations created prior to Release 11.0 are not forward compatible. All configurations
for SGSNs, with -related configurations that were generated with software releases prior to Release 11.0,
must be converted to enable them to operate with an SGSN running Release 11.0 or higher. Your Cisco
Representative can accomplish this conversion for you.
Some Features Managed by Operator Policies
The following is a list of some of the features and functions that can be controlled via configuration of Operator
Policies:
• APN Aliasing
• Authentication
• Direct Tunnel - for feature description and configuration details, refer to the Direct Tunnel section in
this guide
• Equivalent PLMN
• IMEI Override
• Intra- or Inter-SGSN Serving Radio Network Subsystem (SRNS) Relocation (3G only)
• Network Sharing
• QoS Traffic Policing per Subscriber
• SGSN Pooling - Gb/Iu Flex
• SuperCharger
• Subscriber Overcharging Protection - for feature description and configuration details for Gn-SGSN,
refer to the Subscriber Overcharging Protection section in this guide.
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Overcharging Protection
Overcharging Protection
Overcharging Protection enables the Gn-SGSN to avoid overcharging the subscriber if/when a loss of radio
coverage (LORC) occurs in a UMTS network. For details and configuration information, refer to the Subscriber
Overcharging Protection section in this book.
QoS Traffic Policing per Subscriber
Traffic policing enables the operator to configure and enforce bandwidth limitations on individual PDP contexts
for a particular traffic class.
Traffic policing typically deals with eliminating bursts of traffic and managing traffic flows in order to comply
with a traffic contract.
The SGSN conforms to the DiffServ model for QoS by handling the 3GPP defined classes of traffic, QoS
negotiation, DSCP marking, traffic policing, and support for HSDPA/HSUPA.
QoS Classes
The 3GPP QoS classes supported by the SGSN are:
• Conversational
• Streaming
• Interactive
• Background
The SGSN is capable of translating between R99 and R97/98 QoS attributes.
QoS Negotiation
On PDP context activation, the SGSN calculates the QoS allowed, based upon:
• Subscribed QoS - This is a per-APN configuration, obtained from the HLR on an Attach. It specifies
the highest QoS allowed to the subscriber for that APN.
• Configured QoS - The SGSN can be configured with default and highest QoS profiles in the
configuration.
• MS requested QoS - The QoS requested by the UE on pdp-context activation.
DSCP Marking
The SGSN performs diffserv code point (DSCP) marking of the GTP-U packets according to allowed-QoS
to PHB mapping. The default mapping matches that of the UMTS to IP QoS mapping defined in 3GPP TS
29.208.
The SGSN also supports DSCP marking of the GTP control plane messages on the Gn/Gp interface. This
allows QoS to be set on GTP-C messages, and is useful if Gn/Gp is on a less than ideal link. DSCP marking
is configurable via the CLI, with default = Best Effort Forwarding.
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VPC-DI platform support for SGSN
Traffic Policing
The SGSN can police uplink and downlink traffic according to predefined QoS negotiated limits fixed on the
basis of individual contexts - either primary or secondary. The SGSN employs the Two Rate Three Color
Marker (RFC2698) algorithm for traffic policing. The algorithm meters an IP packet stream and marks its
packets either green, yellow, or red depending upon the following variables:
• PIR - Peak Information Rate (measured in bytes/second)
• CIR - Committed Information Rate (measured in bytes/second)
• PBS - Peak Burst Size (measured in bytes)
• CBS - Committed Burst Size (measured in bytes)
The following figure depicts the working of the TCM algorithm:
Figure 7: TCM Algorithm Logic for Traffic Policing
For commands and more information on traffic policing configuration, refer to the Command Line Interface
Reference.
VPC-DI platform support for SGSN
The traditional proprietary hardware platforms like ASR5K and ASR5500 provide carrier class hardware
redundancy and have limited scalability. The VPC-SI model separates the StarOS from the proprietary
hardware. It consists of the StarOS software running within a single VM. This provides the end user with low
entry cost (software licenses and commodity hardware), simplified setup, and well-defined interfaces. The
VPC-SI is ideally suited for small carriers, remote locations, lab testing, trials, demos, and other models where
full functionality is needed. The Cisco VPC-Distributed Instance (VPC-DI) platform allows multiple VMs to
act as a single StarOS instance with shared interfaces, shared service addresses, load balancing, redundancy,
and a single point of management. The VPC-DI offers enhanced hardware capabilities, the SGSN is enhanced
to support the VPC-DI platform.
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Reordering of SNDCP N-PDU Segments
Important
For more information on the VPC-DI platform see, VPC-DI System Administration Guide.
Reordering of SNDCP N-PDU Segments
The SGSN fully supports reordering of out-of-order segments coming from the same SNDCP N-PDU. The
SGSN waits the configured amount of time for all segments of the N-PDU to arrive. If all the segments are
not received before the timer expiries, then all queued segments are dropped.
RAN Information Management (RIM)
RAN information is transferred from a source RAN node to a destination RAN node in a RIM container. This
is a mechanism for the exchange of information between applications belonging to RAN nodes, for example
two BSCs. The RIM container is transparent to the SGSN.
Support for RIM procedures is optional for both the SGSN and other RAN nodes (e.g., RNC). When the
SGSN supports RIM procedures, the SGSN provides addressing, routing and relay functions. All RIM messages
are routed independently by the SGSN. The SGSN performs relaying of RIM messages between BSSGP,
RANAP, and GTP in accordance with 3GPP TS 48.018, TS25.413, and TS29.060 respectively.
On the Gb (BSSGP) interface, RIM procedures are negotiated at the start/restart of a Gb link as part of the
signaling BVC reset procedure. On the Iu (RANAP) interface, there is no negotiation for using RIM procedures.
Support for RIM procedures enhances the subscriber\'s user experience by minimizing the service outage
during cell re-selection.
S4 Support on the SGSN
The SGSN can provide an interface between UMTS (3G) and/or GPRS (2.5G) networks and the evolved
packet core (EPC) network. This functionality requires a special S4 feature license. Throughout the
documentation the SGSN with this additional functionality is referred to as an S4-SGSN.
To facilitate communication with GPRS, UMTS, and EPC networks, the SGSN is configured with standard
2.5G SGSN, 3G SGSN or dual access SGSN services, and then configured with additional enhancements to
enable communication with the EPC network.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
The S4-SGSN communicates with other UMTS and GPRS core networks elements via the GTPv1 protocol,
and communicates with EPC network elements and peer S4-SGSNs via the GTPv2 protocol. The S4-SGSN
communicates with the UMTS (3G) / GPRS (2.5G) radio access network elements in the same manner as an
SGSN.
Depending on the configured SGSN service type, the S4-SGSN can interface with some or all of the following
UMTS/GPRS and EPC network elements:
• Serving Gateway (S-GW)
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S4 Support on the SGSN
• Mobility Management Entity (MME)
• Peer S4-SGSN (2.5G or 3G with S4 support)
• Peer dual access S4-SGSN
• Peer SGSN (2.5G or 3G)
• Peer dual access SGSN
• GGSN
S3 and S4 Interface Support
S3 and S4 interface support is a license-enabled feature that enables 2G and 3G networks to interface with
the 4G evolved packet core (EPC) network. The S3/S4 functionality ensures session continuity on handovers
between 2G/3G subscribers and 4G LTE subscribers. S3/S4 functionality simplifies core network operations
the following ways:
• Replaces the GGSN in the network with the P-GW
• Replaces the need for an HLR by providing connectivity to the HSS
• Optimized idle mode signaling during 3G/2G to 4G handovers (when the ISR feature is enabled)
The S3 and S4 interfaces provide control and bearer separation, and offload the backward compatibility
requirement from the mobility management entity (MME) and serving gateway (S-GW) EPC elements to the
UMTS core.
• S3 Interface: Provides a GTPv2-C signaling path connection between the MME and the SGSN (MPC).
The S4-SGSN to MME RAU/TAU context handovers are supported via the S3 interface.
• S4 Interface: Provides a data and signaling interface between the S-GW and the S4-SGSN (MPC) for
bearer plane transport (GTPv2-U). The S4-SGSN communicates with the P-GW via the S-GW.
With support for S3/S4 interface, soft-handoffs between 2G/3G and the EPC networks are possible for
multi-mode UEs. Without this functionality, the Gn/Gp SGSN can still inter-work with the EPC core using
GTPv1, but soft-handoffs cannot be achieved. Note that GTPv2 to GTPv1 conversions (for QoS and Context
IDs) are lossy data conversions, so a subscriber doesn\'t encounter a similar type of network behavior while
in 2G/3G and 4G networks.
S4-SGSN Support for "Higher Bit Rates than 16 Mbps"Flag
As per 3GPP R9 specifications, the SGSN can now be aware if the UE is capable of supporting extended R7
bit rates. The "higher bit rates than 16 Mbps" flag is used for this purpose. This flag is sent by the RNC in the
Initial UE message or Re-location Complete message or by Peer S4-SGSN / MME in Forward Relocation
Request / Context Response message. The SGSN also supports sending "higher Bit Rates than 16 Mbps flag"
as part of MM Context in Context response/Forward Relocation request/Identification request during Old
ISRAU/SRNS handover procedures.The SGSN stores the UE capability in the MM-context. During PDP
context activation, the per bearer bit rate or APN-AMBR is capped based on the flag's value. If the RNC is
not 3GPP R9 compliant, the SGSN does not receive this flag. A new CLI keyword sm
ue-3gpp-compliance-unknown restrict-16mbps is introduced under the sgsn-service to support this
functionality. When the CLI is configured, the SGSN caps the APN-AMBR for non-GBR bearers to "16"
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S4 Support on the SGSN
Mbps and rejects activation of GBR bearers with GBR higher than "16" Mbps. If not, APN-AMBR and GBR
higher than "16" Mbps are allowed.
Consider the scenarios where UE 3GPP compliance is not known and the CLI is configured to restrict bitrate
to 16 Mbps or it is known that UE is not capable of supporting bitrates higher than 16Mbps; the Session
Manager uses the flag to perform the following actions:
1 The APN-AMBR is restricted to "16" Mbps during PDP activation of non-GBR bearers, particularly the
default bearer.
2 If the PGW upgrades the APN-AMBR in Create Session Response during non-GBR bearer activation,
then the APN-AMBR is retained as "16" Mbps and same is indicated to the UE in an Activate Accept.
3 If the PGW upgrades APN-AMBR in Update Bearer Request for non-GBR bearer, then the APN-AMBR
is restricted to "16" Mbps and only if the APN-AMBR changes, the PGW init bearer modification procedure
is continued. In case APN-AMBR does not change, then Update Bearer Response is sent immediately.
4 For GBR bearers, Update Bearer Request with GBR/MBR higher than "16" Mbps is rejected with "No
resources available".
5 Activation of GBR bearers with MBR/GBR higher than "16" Mbps in Create Bearer Request is rejected
with cause "No resources available".
6 After S3 SRNS, Modify Bearer Command is initiated to modify the APN-AMBR to "16" Mbps for
Non-GBR bearers having bitrates higher than 16 Mbps.
7 After S3 SRNS, GBR bearers having bitrates higher than "16" Mbps are de-activated.
For more information on the CLI command see, Command Line Interface Reference.
S6d and Gr Interface Support
The S4-SGSN supports the Diameter based S6d interface to the HSS, in addition to the legacy Gr interface
to the HLR (used by an SGSN configured to use the Gn/Gp interfaces). This is a license-enabled feature.
The S6d / Gr interface enhancements allow operators to consolidate the HLR/HSS functions into a single
node, which improves operational efficiency and other overhead. With the deployment of the EPC core, many
operators may consolidate the HLR/HSS functions into a single node. Until then, the S4-SGSN still supports
the MAP-based Gr and the Diameter based S6d interfaces.
The SGSN selects the Gr interface / S6d interface based on the MAP or HSS service associated with the
configured SGSN and/or GPRS services. If both the services are associated, then SGSN will use the following
order of selection:
1 Select the appropriate interface based on any operator policy preference for S6d / Gr.
2 If no operator policy is present, then by use the Gr interface by default.
The S4-SGSN sets the following initiate UGL messages on a change of HSS service:
• Initial attach indicator bit in Update GPRS Location message, ISR information IE, if the UGL is sent
for an initial attach or for a inbound routing area update without ISR activation and the selected interface
is Gr.
• Initial attach indicator bit in Update Location Request message, ULR flags, if the ULR is sent for an
initial attach or for a inbound routing area update without ISR activation and the selected interface is
S6d.
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Configurable Pacing of PDP Deactivations on the S4-SGSN
The S4-SGSN now supports configurable pacing of PDP de-activations towards UEs due to path failures.
Previously in the S4-SGSN, the pacing of path failure delivery was started by the EGTP application and it
used the generic session manager pacing mechanism. The generic pacing mechanism performed 1000 path
failure initiated PDP de-activations per second per session manager. Since this may not be desirable for many
operators based on their RAN's capability, the S4-SGSN now supports the configurable pacing of PDP
deactivations via the SGSN application (the same mechanism used in the Gn/Gp SGSN).
The existing pdp-activation-rate command in SGSN Global Configuration Mode can be used to configure
the pacing of PDP de-activations for both the connected-ready state and the idle-standby state.
This feature is included with the SGSN S3/S4 license. No additional feature license is required.
DNS SNAPTR Support
By default, the S4-SGSN supports the initiation of a DNS query after APN selection using a S-NAPTR query.
The SGSN resolves a P-GW by sending an APN-FQDN query to the DNS client. Similarly, the SGSN resolves
the S-GW by sending a RAI-FQDN query to the DNS client. The DNS Client then sends a query to the DNS
server to retrieve NAPTR/SRV/A records and return the S-GW or P-GW IP address to the SGSN.
On the S4-SGSN, an additional configurable is available that identifies the context where DNS lookup for
EPC-capable UEs must occur. This is accomplished by creating a call control profile that directs the system\'s
DNS client to perform the lookup in the context where the SGSN\'s DNS client is configured.
If the CLI configurable is not used, or removed, the S4-SGSN chooses the DNS client from the context where
the EGTP service is configured for performing P-GW DNS resolution, if the EGTP service is associated for
a EPC capable UE.
If the EGTP service is not present and the UE is EPC-capable, and if apn-resolve-dns-query snaptr is
configured in an APN profile, then the S4-SGSN uses the DNS client in the context where the SGTP service
is present for resolving a co-located P-GW/GGSN and selects the Gn interface.
S4-SGSN Statistics Support
Statistics have been added to provide information on S4-SGSN functionality.
The statistics added track information related to:
• SGW Relocations
• ISR Deactivations
• Number of active PDPs using the S4 interface in 3G
• S3 Interface Selection Statistics
• Procedure Abort Statistics
• GTPU Statistics
• IDFT Statistics
In addition, support for EGTPC schema bulk statistics is implemented to provide information on communication
between the S4-SGSN and the EPC S-GW over the S4 interface.
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S13' Interface Support
In addition to the MAP-based Gf interface, the S4-SGSN supports the Diameter-based S13' (S13 prime)
interface towards the equipment identify registry. The S13' interface support enables operators to consolidate
the EIR functions into a single node, which increases operational efficiency. S13' interface support is a
license-enabled feature.
The S13' interface enables the S4-SGSN to perform the ME Identity Check procedure to validate the IMEI
with the EIR. The S4-SGSN selects Gf or S13' interface based on which interface is configured and the type
of service (MAP or HSS) is associated with the SGSN and/or the GPRS service. If both services are associated,
then the S4-SGSN will select the appropriate interface based on the following sequence:
1 An operator policy preference is configured for Gf or S13'
2 If no operator policy preference is set, then by default the S4-SGSN uses the Gf interface
By default, the IMSI is sent to the EIR as part of the IMEI Check procedure over the S13' interface.
Idle Mode Signaling Reduction
The Idle mode signaling reduction (ISR) feature on the S4-SGSN provides a mechanism to optimize and/or
reduce signaling load during inter-RAT cell-reselection in idle mode (that is, in the ECM-IDLE, PMM-IDLE,
and GPRS-STANDBY states). It is a mechanism that allows the UE to remain simultaneously registered in
a UTRAN/GERAN Routing Area (RA) and an E-UTRAN Tracking Area (TA) list. This allows the UE to
make cell reselections between E-UTRAN and UTRAN/GERAN without having to send any TAU or RAU
requests, as long as the UE remains within the registered RA and TA list.
ISR is a feature that reduces the mobility signalling and improves the battery life of UEs. Also reduces the
unnecessary signalling with the core network nodes and air interface. This is important especially in initial
deployments when E-UTRAN coverage will be limited and inter-RAT changes will be frequent.
The benefit of the ISR functionality comes at the cost of more complex paging procedures for UEs, which
must be paged on both the registered RA and all registered TAs. The HSS also must maintain two PS
registrations (one from the MME and another from the SGSN).
ISR support for 3G subscribers was introduced in release 14.0. ISR support for 2G subscribers is available in
15.0 and later releases.
ISR is not supported on the Gn/Gp SGSN.
For a detailed description of this feature, refer to the Idle Mode Signaling Reduction on the S4-SGSN chapter
in this guide.
Important
ISR is a license enabled feature. Contact your Cisco representative for details on licensing information.
ISR with Circuit Switched Fallback
Circuit-Switched Fallback (CSFB) is an alternative solution to using IMS and SRVCC to provide voice
services to users of LTE. The IMS is not part of the solution, and voice calls are never served over LTE.
Instead, the CSFB relies on a temporary inter-system that switches between LTE and a system where
circuit-switched voice calls can be served.
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The LTE terminals 'register' in the circuit switched domain when powered and attaching to LTE. This is
handled through an interaction between the MME and the MSC-Server in the circuit-switched network domain
over the SGs interface.
Consider the following scenarios:
• Voice calls initiated by the mobile user: If the user makes a voice call, the terminal switches from a LTE
system to a system with circuit-switched voice support. Depending on where the UE latches on after
completion of the voice call:
◦The packet-based services that are active on the end-user device at this time are handed over and
continue to run in a system with circuit-switched voice support but with lower data speeds.
OR
◦The packet-based services that are active on the end-user device at this time are suspended until
the voice call is terminated and the terminal switches back to LTE again and the packet services
are resumed.
• Voice calls received by the mobile user: If there is an incoming voice call to an end-user that is currently
attached to the LTE system, the MSC-Server requests a paging in the LTE system for the specific user.
This is done through the SGs interface between the MSC Server and the MME. The terminal receives
the page, and temporarily switches from the LTE system to the system with circuit-switched voice
support, where the voice call is received. Once the voice call is terminated, the terminal switches back
to the LTE system.
For a detailed feature description of this feature refer to the chapter "ISR with Circuit Switched Fallback"
in this document.
ISD / DSD Message Handling and HSS Initiated Bearer Modification
The Home Subscriber Server (HSS) / Home Location Register (HLR) maintains the subscriber database. Insert
Subscriber Data (ISD) and Delete Subscriber Data (DSD) messages are generated by the HSS/HLR. These
messages are used to communicate the subscribers current subscription data to the S4-SGSN. The subscription
data for a subscriber can include one of the following:
• GPRS subscription data.
• EPS subscription data.
• Both GPRS and EPS subscription data.
The PDP is either modified or deleted based on the subscription data received by the S4-SGSN.
The S4-SGSN deletes the PDP context if any form of barring is detected or if the APN-name or PDP-type of
the PDP address is changed. The S4-SGSN modifies the PDP if QoS is changed or APN-AMBR is changed
(in case of EPS subscription).
If a PDP modification is required based on the subscription data received but the associated UE is disconnected
or in an inactive state, such PDP contexts are deleted by the S4-SGSN.
Important
The S4-SGSN does not delete the PDP contexts if Idle Mode Signalling Reduction (ISR) is activated or
PDP is preserved. In such cases the S4-SGSN initiates a PDP modify only after UE activity is detected.
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If the UE is connected or in a ready state, the S4-SGSN sends an updated bearer command (with subscribed
QoS) to the S-SGW or P-GW and the P-GW initiates a PDP modify procedure.
HSS initiated bearer modification
The Modify bearer command is a notification sent to the S-GW/P-GW which notifies a change in the subscribed
QoS. The message is sent to S-GW/P-GW if the UE is in ready or connected state. Modify Bearer command
is not sent when the PDP is in preserved state and when ISR is active, in such cases the S4-SGSN initiated
modify request using Modify Bearer Request updates the QoS to the S-GW/P-GW after the PDP is active or
UE activity is detected on S4-SGSN respectively.
UMTS-GSM AKA Support on the S4-SGSN
The S4-SGSN provides support for the following UMTS/GSM Authentication and Key Agreement (AKA)
procedures:
• SRNS relocation
• Attach
• PTMSI attach (foreign/local)
• Service Request
• Inter SGSN RAU
• Timers Handling
• Re-use of Vectors
• Using the Peer SGSN/MME vectors (ISRAU/PTMSI attach) in the same or different PLMN
3G and 2G SGSN Routing Area Update
The S4-SGSN supports outbound Routing Area Update (RAU) procedures for a subscriber already attached
on that SGSN (that have PDP contexts anchored through S4 interface) and inbound RAU procedures for an
EPC capable UE. The RAU procedures are required to enable mobility across the UMTS and EPC core
network coverage areas using the S3 interface for context transfers.
The S4-SGSN determines if the old peer node is an MME or SGSN based on the most significant bit of the
LAC. If the most significant bit of the LAC is set then the old peer node is an MME (and the RAI is mapped
from GUTI). If the bit is not set then the old RAI represents an SGSN.
However, some operators have already used LAC values greater than 32768 (most significant bit set) for their
existing UMTS / GPRS networks. For such operators identification of a peer node through MSB bit of LAC
will not work. In these cases, operators can use the Configurable GUTI to RAI Conversion Mapping, on page
53 feature.
The following RAU procedures are supported for both 2G and 3G services:
• 2G and 3G Intra-SGSN RAU with and without S-GW relocation
• 2G and 3G Inter-SGSN/SGSN-MME RAU with and without S-GW relocation across S16 and S3
interfaces
• Intra-SGSN Inter-RAT RAU with and without S-GW relocation
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2G and 3G Intra RAU with and without S-GW Relocation
The S4-SGSN supports the intra-SGSN routing area update (ISRAU), which can occur in the following
scenarios:
• The MS changes its routing area
• The periodic RAU timer expires for the MS
• The MS changes its network capability
The S4-SGSN also supports intra SGSN, inter PLMN RAU requests. However, if the new PLMN\'s operator
policy is configured to use the Gn interface, the PDP contexts are not transferred from the S4 interface to the
Gn interface.
Important
The S4-SGSN currently does not support the association of a different EGTP service for each PLMN.
2G and 3G Inter-SGSN and Inter SGSN-MME RAU with and without S-GW Relocation Across S16 and S3 Interfaces
The S4-SGSN supports both Inter-SGSN RAU and SGSN-MME RAU, which will be triggered when a UE
sends Routing Area Update (RAU) request to a new SGSN in the following scenarios:
• The serving RAI changes from one SGSN coverage area to another SGSN coverage area
• During a handover from a E-UTRAN coverage area to a UMTS coverage area
Intra-SGSN Inter-RAT RAU with and without S-GW Relocation
The S4-SGSN supports intra-SGSN 3G to 2G routing area updates (RAU) and supports the handover of MM
and PDP contexts from the SGSN service to the GPRS service. Similarly, it supports intra-SGSN 2G to 3G
RAUs and supports the handover of MM and PDP contexts from the GPRS service to the SGSN service.
Important
Currently, the S4-SGSN expects that both the SGSN and GPRS services will be associated with the same
EGTP service for successful intra-SGSN inter-RAT handovers.
IPv4 and IPv6 PDP Type Override
The S4-SGSN supports the override of the IPv4/IPv6 PDP type by either IPv4 or IPv6 when the dual PDP
feature is enabled. This is controlled via a call control profile, and is configured independently for 2G GPRS
and 3G UMTS access.
Statistics are maintained to track successes and failures for IPv4 and IPv6 PDP activations with override.
NAPTR-based Dynamic HSS Discovery
In releases prior to R15.0, the SGSN could contact a HSS only through static configuration of the HSS peer
end point through the HSS service. From Release R15.0 onwards, dynamic peer discovery is supported. The
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HSS address will be resolved using NAPTR based DNS request-response method. The following commands
have to be enabled for dynamic peer discovery:
• In the Context Configuration Mode, the command diameter endpoint < endpoint_name > has to be
enabled.
• In the Diameter Endpoint Configuration Mode, the command dynamic-peer-discovery [ protocol {
sctp | tcp } ] has to be enabled.
• In the Diameter Endpoint Configuration Mode, the command dynamic-peer-realm < realm_name >
has to be enabled.
• In the Diameter Endpoint Configuration Mode, the command dynamic-peer-failure-retry-count <
no_of_retries > has to be enabled.
The "realm name" is used for dynamic peer discovery. The "dynamic-peer-failure-retry-count" is used to
configure the number of re-tries in peer discovery.
P-GW Initiated PDP Bearer Deactivation
The S4-SGSN supports the P-GW initiated PDP deactivation procedure in addition to the legacy MS initiated
deactivation procedure.
The S4-SGSN processes Delete Bearer Requests received from the S-GW (sent by the P-GW) and deactivates
the requested bearers (PDP contexts) by sending a Deactivate PDP Context Request to the UE and then
deactivates the PDP context. If the S4-SGSN receives a Delete Bearer Request from the S-GW and the
subscriber is in the PMM-IDLE / GPRS-STANDBY state, it pages the UE before deactivating the PDP context
request.
In the case of 3G, the S4-SGSN will initiate RAB release procedures for the deactivated bearers. For 2G there
is no RAB release procedure.
S-GW and P-GW Tunnel and EPS Subscription Recovery
The S4-SGSN supports session recovery procedures and recovers the S4 tunnel created for each subscriber
assigned PDP contexts through S4 interface. This functionality is part of session recovery procedures and
allows sessions to be reconstructed when the system recovers from a card-level software fault.
The SGSN side TEID and the S-GW side TEID for the S4 tunnel are check-pointed and recovered during
session recovery. The S4-SGSN also recovers every PDN connection and their corresponding P-GW-side
TEID.
The S4-SGSN session recovery procedures have been enhanced to support recovery of EPS subscription data
received from the HLR / HSS. The EPS subscription information may contain a maximum of 50 APN profiles
and each APN profile contains an APN name string and a PDN GW FQDN string, which is check-pointed
and recovered as part of the enhanced session recovery procedures.
Local Configuration of S-GW and S4-SGSN per RAI
The SGSN already supports selection of the S-GW using DNS SNAPTR queries for the RAI FQDN. The
S4-SGSN now provides the option to configure a local S-GW address for a RAI (LAC, RAC MCC and MNC).
This functionality enhances the S-GW selection logic to allow the call to continue even if DNS lookup fails
for any reason.
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The S4-SGSN will select this local S-GW address based on the configured local policy. The local policy also
can be configured to allow the selection of the locally configured S-GW address when the DNS lookup fails.
Local selection of the S-GW address applies in the following scenarios:
• First PDP context activation for a subscriber
• Intra SGSN routing area update
• New SGSN routing area update
• Intra SGSN inter RAT handover
Configurable GUTI to RAI Conversion Mapping
The S4-SGSN allows operators to configure mapping to an EPC MME for networks that already use LAC
ranges between 32768 and 65535.
LAC ranges between 32768 to 65535 are currently being used in some UMTS/GPRS deployments although
3GPP TS 23.003 indicates that a UMTS / GPRS network should not use LACs in that range. This range is
reserved for the MME group code.
In an LTE network, the MME group code is mapped to the LAC and therefore the LAC and MME group code
should be separate. The S4-SGSN provides a customized solution for this problem by identifying the valid
MME group codes, which it uses to identify whether the received LAC is a native LAC or a LAC mapped
from GUTI (i.e., an MME group code part of GUTI).
S4-SGSN Support for Fallback to V1 Cause Code in GTPv2 Context Response
As per revised 3GPP TS 29.274 v8.6.0, the Context Response message received from a peer SGSN can have
a cause code "Fallback to GTP-V1", if the peer SGSN had provided a Gn interface for a subscriber due to
local policy. When a new SGSN receives a Context Response with cause code as "Fallback to GTP-v1" it
performs a GTP-v1 SGSN Context Request, Context Response and Context Ack with the peer SGSN to obtain
the subscribers MM and PDP contexts.
S4-SGSN Support for Mobility Management Procedures
To support the S6d/Gr interface, the S4-SGSN supports the following mobility management procedures over
the those (HSS/HLR) interfaces:
• Attach
• Service request
• Detach
• Iu-Release procedures
• Operator policy override for the Gn/S4 interface for EPC subscribers
• Zone code
• ARD
• ADD
• Operator policy-based Mobility Management context handling
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QoS Mapping Support
The S4-SGSN supports the configuration of QoS parameters to ensure proper QoS parameter mapping between
the S4-SGSN and EPC S-GWs, P-GWs, and UEs.
The S4-SGSN communicates QoS parameters towards the S-GW and P-GW in EPC QoS. However, it sends
QoS towards the UE in the QoS format defined in the GMM/SM specification (TS 24.008). 3GPP defines a
mapping for EPS QoS to pre-release 8 QoS in TS 23.401, Annex E. On the S4-SGSN, operators can configure
the quality of service (QoS) parameters as call-control-profiles that will ensure proper QoS mapping between
the S4-SGSN and the EPC gateways (P-GW and S-GW) and UEs.
The configured call-control-profiles will be used if the S4 interface is chosen for PDP activation, but the
subscription does not have an EPS subscription. Therefore, GPRS subscription data (which uses QoS in
pre-release 8 format), will be mapped to EPS QoS behavior. The Allocation and Retention policy will be
mapped to EPS ARP using the configured call control profiles.
If the QoS mapping configuration is not used, the following default mappings are used:
• Default ARP high-priority value = 5
• Default ARP medium-priority value = 10
• Default pre-emption capability = shall-not-trigger-pre-emption
• Default pre-emption vulnerability = not pre-emptable
MS Initiated Primary and Secondary Activation
The S4-SGSN supports default and dedicated bearer activation for:
• Default and dedicated activation - secondary PDP procedure trigger from MS).
• Lawful Intercept for activation rejects and failures
• Dual stack PDP handling
• APN-selection as per annex A.2/Spec 23.060 rel-9
Deactivation Procedure Support
The S4-SGSN supports the following deactivation procedures:
• 3G / 2G MS initiated bundle deactivation
• 3G / 2G MS initiated dedicated bearer deactivation
• 3G / 2G P-GW initiated dedicated bearer deactivation
• 3G / 2G P-GW initiated PDN deactivation
MS, PGW and HSS Initiated PDP Modification Procedure Support
The S4-SGSN supports the following packet data protocol (PDP) modification procedures:
• 2G and 3G MS initiated PDP modification procedures
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• 2G and 3G P-GW Initiated PDP modification procedures
• 2G and 3G HSS initiated PDP modification procedures
The PDP context modification procedures are invoked by the network or by the MS to modify the parameters
that were negotiated under the following conditions:
• During the PDP context activation procedure
• During the secondary PDP context activation procedure
• At a previously performed PDP context modification procedure
Depending on the selected Bearer Control Mode, the MS or the network may also create and delete a traffic
flow template (TFT) in an active PDP context. The procedure can be initiated by the network or the MS at
any time when a PDP context is active. Only the network may modify or delete a TFT packet filter that the
network has created. Conversely, only the MS may modify or delete a TFT packet filter that the MS has
created.
MS-Initiated PDP Context Modification
The Mobile Station (MS) initiated PDP context modification procedure MS allows for a change in negotiated
QoS, the radio priority level, or the TFT negotiated during the PDP context activation procedure.
E-UTRAN capable MSs will not modify the QoS of the first PDP context that was established within the PDN
connection.
The MS initiates the Modification procedure by sending a MODIFY PDP CONTEXT REQUEST message
to the SGSN. The SGSN validates the received message and sends out a BEARER RESOURCE COMMAND
message to the S-GW with a valid PTI value which is then sent to the PGW. On accepting the modification,
the P-GW sends out an Update Bearer Request with the PTI copied from the received BEARER RESOURCE
COMMAND message. Upon successful completion of the modification, the SGSN replies with the MODIFY
PDP CONTEXT ACCEPT message.
P-GW-Initiated PDP Context Modification
The Packet Data Node Gateway (P-GW) initiated PDP context modification procedure is used in cases when:
• One or several of the EPS Bearer QoS parameters are to be modified
• To add/modify/delete the TFT related to the PDP Context or BCM-Mode change
• To modify the APN-AMBR
The P-GW can request the modification procedure by sending an UPDATE BEARER REQUEST message
without a PTI field to the S-GW, and the S-GW will forward the request to SGSN. The SGSN validates the
request and initiates a MODIFY PDP CONTEXT REQUEST message to the MS. On successful completion
of the procedure, the SGSN will send an UPDATE BEARER RESPONSE with an appropriate cause value.
HSS Initiated PDP Context Modification
The Home Subscriber Server (HSS) initiated PDP context modification procedure is used when the HSS
decides to modify the subscribed QoS, where typically QoS related parameters are changed. The parameters
that may be modified are UE-AMBR, APN-AMBR QCI and Allocation/Retention Policy.
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The HSS initiates the modification by sending an Insert Subscriber Data (IMSI, Subscription Data) message
to the SGSN. The Subscription Data includes EPS subscribed QoS (QCI, ARP) and the subscribed UE-AMBR
and APN AMBR.
The S4-SGSN then updates the stored Subscription Data and acknowledges the Insert Subscriber Data message
by returning an Insert Subscriber Data Ack (IMSI) message to the HSS and sends the Modify Bearer Command
(EPS Bearer Identity, EPS Bearer QoS, APN AMBR) message to the S-GW. The S-GW forwards the Modify
Bearer Command (EPS Bearer Identity, EPS Bearer QoS, APN AMBR) message to the P-GW. Note that the
EPS Bearer QoS sent in the Modify Bearer Command does not modify the per bearer bit-rate. It is sent to
carry only a change in the ARP / QCI received from subscription. Also, the Modify Bearer Command can be
sent only for the default bearer (primary PDP) in a PDN connection.
The P-GW modifies the default bearer of each PDN connection corresponding to the APN for which subscribed
QoS has been modified. If the subscribed ARP parameter has been changed, the P-GW shall also modify all
dedicated EPS bearers having the previously subscribed ARP value unless superseded by PCRF decision.
The P-GW then sends the Update Bearer Request (EPS Bearer Identity, EPS Bearer QoS [if QoS is changed],
TFT, APN AMBR) message to the S-GW.
The S-GW sends the Update Bearer Request (EPS Bearer Identity, EPS Bearer QoS [if QoS is changed]
APN-AMBR, TFT) message to the SGSN. On completion of modification S4-SGSN acknowledges the bearer
modification by sending the "Update Bearer Response (EPS Bearer Identity)" message to P-GW via S-GW.
If the bearer modification fails, the P-GW deletes the concerned EPS Bearer.
Fallback from the S4 Interface to the Gn Interface
The S4-SGSN supports fallback the S4 interface and selects the Gn interface for the 1st PDP context activation
if the APN DNS-SNAPTR resolution returns only a Gn address. This functionality allows the PDP context
request to be completed when DNS resolution returns a GGSN address instead of a P-GW address.
This mechanism is applicable in the following cases:
• The UE is EPC-capable
• The UE\'s subscription has a GPRS subscription only (and not an EPS subscription)
If the subscription has an EPS subscription for an APN, then it is assumed that the P-GW addresses are
configured in the DNS for that APN.
Operator Policy Selection of S4 or Gn Interface
The S4-SGSN supports Operator Policy selection of either the S4 or the Gn interface for PDP context operations.
This feature allows flexible operator control over interface selection for operational or administrative reasons.
This functionality overrides any other criteria for selection of the P-GW or the GGSN for PDP contexts. This
feature is applicable only for EPC-capable UEs.
IDFT Support During Connected Mode Handovers
The S4-SGSN supports the setup of indirect data forwarding tunnels (IDFT) between the eNodeB and the
RNC via the SGW during connected mode handovers. This allows the S4-SGSN to support connected mode
handovers between the UTRAN and E-UTRAN networks across the S3 interface.
Once enabled, IDFT is employed under the following conditions:
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• If the SGSN is the old node participating in the connected mode handover, then indirect data
forwarding tunnels is used if:
◦The target node to which the connected mode handover is initiated should be an eNodeB (i.e., the
SGSN performs the handover to the MME).
◦The enb-direct-data-forward CLI setting is not configured as the source RNC configuration (in
RNC Configuration Mode).
• If the SGSN is the new node participating in the connected mode handover, then indirect data
forwarding tunnels is employed if:
◦The source node from which connected mode handover is initiated is an eNodeB (i.e., the MME
is performing a handover to the SGSN).
◦The enb-direct-data-forward setting is not configured in the source RNC configuration (in RNC
Configuration Mode).
◦The source MME indicated that it does not support direct forwarding via a Forward Relocation
Request.
Important
If the target SGSN did not relocate to a new SGW, IDFT does not apply. The target SGSN sets up an
indirect data forwarding tunnel with SGW only if the SGW is relocated. If the SGW is not relocated, then
it is the source MME that sets up the indirect data forwarding tunnel between source the eNodeB and
target RNC through the SGW.
Disassociated DSR Support
The S4-SGSN supports the disassociation of the SGSN and EGTP applications for a Delete Session Request
in a certain scenario. In this scenario, the SGSN application instructs the EGTP facility to send the Delete
Session Request to the SGW and not respond back to the SGSN application to confirm the action. In effect,
the SGSN application disassociates itself from the EGTP facility. Since the SGSN application is no longer
waiting for a response from the EGTP facility, there will be reduced internal communication between the
SGSN and EGTP. The the EGTP facility will handle retransmissions of the DSR request, thereby eliminating
the possibility of hanging sessions at the SGSN.
The behavior of the disassociated DSR feature for each of the applicable scenarios follows:
1 The SGSN / MME wants to send a DSR with OI=0 and SI=1 to an old SGW during SGW relocation.
2 The SGSN application instructs the EGTP facility to inform the old SGW of the DSR and the SGSN
doesn't expect any response from EGTP.
3 The EGTP facility handles retransmissions of this DSR request.
SGSN Serving Radio Network Subsystem (SRNS) Relocation Support
SRNS relocation is the method defined in 3GPP TS 23.401 for connected mode inter-RAT handovers from
E-UTRAN to UTRAN or UTRAN to E-UTRAN networks. The SGSN already supports SRNS relocation
across the Gn interface. The SGSN now also supports SRNS relocation with the following cases across the
S3 (S4-SGSN to MME) and S16 (S4-SGSN to S4-SGSN) interfaces:
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• Intra-SGSN SRNS relocation
• Inter-SGSN SRNS relocation over the S16 interface
• UTRAN-to-E-UTRAN connected mode Inter-RAT handover over the S3 interface
• UTRAN-to-E-UTRAN connected mode Inter-RAT handover over the S3 interface
The relocation feature is triggered by subscribers (MS/UE) moving between an eNodeB and an RNC. If the
originating and destination nodes are connected to the same S4-SGSN but are in different routing areas, the
behavior triggers an intra-SGSN Routing Area Update (RAU). If the nodes are connected to different S4-SGSNs,
the relocation is followed by an inter-SGSN RAU.
As part of the SRNS relocation feature implementation on the S4-SGSN, the SGSN application also supports
the gtpv2 (egtp) protocol for:
• Inter-SGSN SRNS relocations over the S16 interface
• MME - SGSN SRNS relocations over the S3 interface
A command is available to enable the SGSN to support SRNS relocation when the source RNC is behaving
as the target RNC.
Configuration and Maintenance
The existing srns-inter and srns-intra commands in Call Control Profile Configuration Mode are used to
enable this feature.
In addition, the enb-direct-data forward command in RNC Configuration Mode can be used to enable the
S4-SGSN to apply direct forwarding tunnels or indirect data forwarding tunnels (IDFT) between a particular
eNodeB and RNC.
Statistics are also available with the show s4-sgsn statistics all command that enable operators to track SGW
relocations and SRNS procedure aborts.
E-UTRAN Service Handover Support
The SGSN supports configuration-based enabling of the E-UTRAN Service Handover Information Element,
which is optional in the following RANAP messages used during SRNS relocation:
• RAB Assignment Request
• Relocation Request
This feature is useful in the following scenarios:
1 A UE is E-UTRAN capable, the PLMN is E-UTRAN capable, but the UE has not subscribed to EPS
services (no 4G subscription available).
2 The VPLMN is E-UTRAN-capable, and the UE of an inbound roamer is E-UTRAN capable, but the UE
has only a UTRAN/GERAN roaming agreement in place.
The feature ensures that an SRNS relocation handover to E-UTRAN is not allowed for E-UTRAN capable
UEs that have only a UTRAN/GERAN roaming agreement. This results in an elimination of potential service
denial or disruption issues, and unnecessary signaling.
To implement this feature, CLI commands have been implemented so that the SGSN can be configured to:
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• Override the "eutran-not-allowed" flag received from the HLR/HSS in the ISD/ULA request for the
Access Restriction Data (ARD) parameter (for scenario 2 above).
• Enable the inclusion of the E-UTRAN Service Handover IE in RAB Assignment Request and Relocation
Request RANAP messages for scenarios 1 and 2 above).
Important
SRNS relocation must be configured via the srns-inter and/or srns-intra commands in Call Control
Profile Configuration Mode before configuring E-UTRAN Service Handover Support.
Support for Gn Handoff from S4-SGSN to 2G/3G Gn SGSN
The S4-SGSN supports handoffs from the S4-SGSN to a 2G/3G peer Gn/Gp SGSN as follows:
• An EPC capable UE is attached to an S4-SGSN and has PDP contexts towards the EPC core using the
S4 interface.
• When the UE hands off to a Gn/Gp SGSN, the S4-SGSN transfers the PDP contexts to the peer SGSN
using the GTPv1 protocol.
No CLI commands are require to implement this functionality.
Suspend/Resume Support on the S4-SGSN
The S4-SGSN Suspend/Resume feature provides support for suspend/resume procedures from the BSS and
a peer S4-SGSN.
When a UE is in a 2G coverage area wants to make a circuit switched voice call but the Class A mode of
operation is not supported by the network, then the packet switched data session (PDP contexts) must be
suspended before the voice call can be made. In this case, the BSS sends a Suspend Request to the SGSN. If
the UE is already attached at that SGSN then the suspend request is handled via an intra-SGSN suspend/resume
procedure. If the UE is not attached at the SGSN then the Suspend Request is forwarded to a peer SGSN/MME
through GTPv2 and an inter-SGSN/SGSN-MME suspend procedure occurs. Once the UE completes the voice
call, either the BSS sends a resume request to resume the suspended PDPs or the UE directly sends a Routing
Area Update Request (RAU) in 2G which will be treated as an implicit resume.
The ability for a GPRS user to access circuit-switched services depends on the subscription held, the network
capabilities, and the MS capabilities.
For detailed information on this feature, refer to the S4-SGSN Suspend/Resume Feature chapter in this guide.
Flex Pooling (Iu / Gb over S16) Support on the S4-SGSN
This feature adds the SGSN Pooling functionality across S16 (peer S4-SGSN) interface, so that the default
SGSN can forward the received Context Requests from the non-Pooled SGSN to the right pooled SGSN,
based on the NRI in P-TMSI. Flex pooling provides better scalability and load balancing. A new CLI command
for pooling has been provided under eGTP Service Configuration to enable S4-SGSN pooling across the S16
interface. For more information on the command, refer to the Command Line Interface Reference Manual.
This feature requires the SGSN S3/S4 license and Flex feature license - no additional feature licenses are
required.
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LORC Subscriber Overcharging Protection on S4-SGSN
With Release 17.0, the S4-SGSN now supports Subscriber Overcharging Protection to prevent both 2G and
3G subscribers from being overcharged when a loss of radio coverage (LORC) occurs over the S4 interface.
As a part of this functionality, the operator must configure all cause codes on the SGSN. If the SGSN receives
a cause code via Iu/Gb interfaces that matches one of the cause codes configured on the SGSN, then the SGSN
includes the ARRL (Abnormal Release of Radio Link) bit in the Release Access Bearer Request.
This feature ensures more accurate billing by protecting the subscriber from overcharging in instances where
abnormal radio resource release occurs. For more information about this feature, refer to the feature chapter
LORC Subscriber Overcharging Protection on S4-SGSN in this Guide.
Summary of Functional Differences between an S4-SGSN and an SGSN (Gn/Gp)
Since the S4-SGSN is configured with 2G, 3G, and/or dual access SGSN services before being configured
with enhancements to enable communication with the EPC network, it shares similarities with a Gn/Gp SGSN.
But, the S4-SGSN also contains a number of functional differences. The following table summarizes these
differences.
Important
After creating or modifying any of the configuration for S4-SGSN node, you must save the configuration
and reboot the node for the change(s) to take effect. Rebooting after configuration changes is typically
not required for a Gn/Gp-SGSN.
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Table 1: Summary of Functional Differences between SGSN and S4-SGSN
Procedure
MS Initiated First Primary
PDP Context Activation
MS Initiated Secondary PDP
Context Activation
Gn/Gp SGSN
S4-SGSN
1 The requested QoS is negotiated
1 The requested QoS is ignored
with the subscribed QoS. The
if UE has EPS subscription. If
negotiated QoS is sent in the Create
EPS subscription is available
PDP Context Request.
SGSN always uses the
subscribed EPS QoS to send in
the Create Session Request. If
there is no EPS subscription but
the UE is still granted access to
the S4 interface, then the system
negotiates the requested QoS
with the subscribed GPRS QoS.
The S4-SGSN maps the
negotiated QoS to EPS QoS as
per as per the mapping table
given in TS 23.203 Table 6.1.7
and TS 23.401 Annex E. and
sends the Create Session
Request. If the requested traffic
class is conversational /
streaming, then the system maps
it to the interactive class as a
primary PDP context. In
S4-SGSN if QoS is downgraded
by RNC during RAB
establishment, then by default
the PDP activation is rejected.
This is as per section 9.2.2.1A
of 23.060 step A below figure
64b. But S4-SGSN provides a
CLI to locally accept the RAB
negotiated QoS to override this
spec defined behavior.
2 Two primary PDP contexts are
for the same APN must be
selected for the same P-GW.
1 Secondary PDP context\'s requested 1 ARP is not sent in the Bearer
QoS will be capped to the
Resource command. But it is
subscribed QoS.
sent by the P-GW in the Create
Bearer Request.
2 Since the Create PDP Context is the
message also used for creating the
Secondary PDP context, ARP also
is sent for secondary PDP context.
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Procedure
MS Initiated PDP Context
Deactivation
GGSN/P-GW Initiated PDP
Context Deactivation
Gn/Gp SGSN
S4-SGSN
1 Both single and bundle deactivation 1 If a primary PDP context must
is allowed.
be deactivated, only bundle
deactivation is allowed.
1 The GGSN can deactivate the
1 If the P-GW deactivates the
primary PDP context alone without
primary PDP context (default
initiating a bundle deactivation.
bearer), it is treated as a bundle
deactivation.
PDP Context Preservation for
1 The SGSN sends the Update PDP
conversational/streaming class.
Context Request to the GGSN with
0kbps as the Maximum Bit Rate
value.
PDP Context Preservation for
1 The SGSN preserves the PDP
interactive/background class.
context as it is.
RNC Initiated QoS
Modification
Intra-SGSN Routing Area
Update in PMM-Idle Mode
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1 The SGSN initiates the PDP
Context Modification procedure.
1 The S4-SGSN preserves the
PDP context as it is.
2 If a direct tunnel was
established, or if ISR is active,
then the S4-SGSN sends a
Release Access Bearer Request
to the S-GW.
1 The S4-SGSN ignores the RAB
Modify Request received from
the RNC.
1 The SGSN sends the Update PDP 1 An intra-SGSN RAU may
Context Request to the GGSN if the
involve a change of S-GW.
PLMN changes.
2 An S4-SGSN sends a Modify
Bearer Request to the
S-GW/P-GW if the RAU
involves a change of PLMN and
if the S-GW doesn\'t change.
Serving GPRS Support Node (SGSN) Overview
S4 Support on the SGSN
Procedure
Intra SGSN RAU in
PMM-CONNECTED Mode
Gn/Gp SGSN
S4-SGSN
1 The SGSN sends the Update PDP 1 An intra-SGSN RAU may
Context Request to the GGSN if the
involve a change of the S-GW.
PLMN changes or if QoS changed
In 16.0 if QoS is changed
due to an RNC release change.
during inter RNC handover (due
to new RNC supporting a lower
QoS range), then S4-SGSN
internally caps the QoS towards
RNC for non GBR bearers
alone (interactive / background
class). The changed QoS is not
signalled to SGW / PGW. If
there are GBR bearers
(conversational / streaming
class) that have a higher
guaranteed bit rate than that can
be supported by the target RNC,
then such GBR bearers are
deactivated.
2 However, in an S4-SGSN, the
SGSN initiated modification
procedure is defined only for
changing of APN-AMBR. A
change of RNC release will
initiate a per bearer QoS
change. There is no way to
communicate this to the S-GW
/ P-GW.
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Procedure
Gn/Gp SGSN
S4-SGSN
Old - Inter-SGSN RAU with
no change in interface type
across SGSNs.
Where both "old" and "new" refer to
SGSNs (Gn/Gp):
Where both "old" and "new" refer
to S4-SGSNs.
1 The old SGSN orders the PDP
1 If the new S4-SGSN indicated
contexts as per priority in the SGSN
that the S-GW has changed in
Context Response message. If the
the Context Ack message, then
UE is PMM-CONNECTED in the
the old S4-SGSN has to initiate
old SGSN, then the old SGSN
a Delete Session Request to the
initiates an SRNS Context Transfer
old S-GW with Scope
before sending the SGSN context
Indication bit set. This Delete
response. In addition, the old SGSN
Session Request is locally
initiates an SRNS Data Forward
consumed at old SGW and will
Command to the SRNS to transfer
not be forwarded to PGW.
the unsent data from the old SRNS 2 The S4-SGSN does not support
to the old SGSN.
lossless PDCP for inter-SGSN
handovers. If the UE was
PMM-CONNECTED in the old
S4-SGSN, then it will not
initiate an SRNS Context
Transfer before sending the
Context Response. The
assumption is that the SRNS
relocation procedure had
occurred prior to the
inter-SGSN RAU for
CONNECTED subscribers.
3 For inter S4-SGSN context
transfers the Context Ack
message doesn\'t carry any data
TEID. That is, the GTPv2
protocol doesn\'t define any
inter-SGSN data tunnel.
Therefore, during connected
mode, a RAU between two
S4-SGSN without an SRNS
relocation will result in packet
losses. It is assumed that SRNS
relocation is enabled in the
UTRAN.
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Procedure
Gn/Gp SGSN
S4-SGSN
Old - Inter SGSN RAU with
change in interface across
SGSN
Where "old" is SGSN (Gn/Gp) and
"new" is S4-SGSN:
Where "old" is S4-SGSN and
"new" is SGSN (Gn/Gp):
1 The old SGSN sends a SGSN
1 The old S4-SGSN receives a
context response with PDP contexts
GTPv1 SGSN Context Request
in prioritized order.
and it converts the EPS bearer
information to PDP contexts
2 If the MS is in
and responds with a SGSN
PMM-CONNECTED state in the
Context Response towards the
old SGSN, it will initiate an SRNS
new SGSN.
Context Transfer towards the old
SRNS and will initiate SRNS Data 2 The old S4-SGSN prioritizes
Forward Command to transfer
the PDP contexts as per ARP.
unsent packets from old SRNS back
PDP prioritization for EPS
to old SGSN. In the new SGSN, the
bearers is not supported.
PDPs will continue to use Gn
interface. Promotion of PDPs to S4
post handover from a Gn SGSN is
not yet supported.
New Inter SGSN RAU for a
1 Uses the PDP context prioritized
PMM-IDLE subscriber
order in the SGSN Context
without a change of interface
Response to select high priority
PDP contexts in the case of
resource limitations at the new
SGSN.
2 The SGSN ends the UPCQ to
GGSN.
1 Performs the S-GW selection
procedure.
2 Uses ARP to prioritize EPS
bearers. In GTPv1 the PDP
contexts sent in SGSN context
response will be in prioritized
order. But such an order is not
defined for sending EPS bearers
in Context Response. The idea
is to use to ARP for
prioritization. PDP prioritization
for EPS bearers is not
supported.
3 The new S4-SGSN alerts of any
change in S-GW through the
Context Ack to the old
S4-SGSN. The PMM module
will wait until the S-GW
selection procedure is complete
at the new S4-SGSN to alert of
the context ack.
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Procedure
Gn/Gp SGSN
New Inter SGSN RAU for a
PMM-CONNECTED
subscriber
Where "old" is S4-SGSN and "new" is Where "new" is S4-SGSN and
SGSN (Gn/Gp):
"old" is SGSN (Gn/Gp):
New SGSN
PMM-CONNECTED /
PMM-IDLE subscriber
handover with interface
change
Where "old" is S4-SGSN and "new" is Where "old" is SGSN (Gn/Gp) and
SGSN (Gn/Gp):
"new" is S4-SGSN:
APN Selection Logic
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S4-SGSN
1 The new SGSN receives PDP
1 The new S4-SGSN receives
contexts in the SGSN Context
PDP contexts in the Context
Response in prioritized order.
Response. There is no
prioritized order. ARP is used
2 RABs will be established at the new
to prioritize. PDP prioritization
SGSN based on the ASI bit value
for EPS bearers is not
for each PDP.
supported.
2 New S4-SGSN performs S-GW
selection.
3 The new S4-SGSN cannot
establish RAB as there is no
ASI bit in the GTPv2 Context
Response. The assumption is
that the Context Req / Response
is used only for IDLE mode
handover, and that for
connected mode handover, the
SRNS relocation procedure
should be used.
1 The new S4-SGSN sends a GTPv1 1 The new S4-SGSN sends a
SGSN Context Request and
GTPv1 SGSN context request,
receives the PDP contexts mapped
after learning that the old SGSN
from EPS bearers in the SGSN
is an SGSN (Gn/Gp) based on
context response.
a DNS S-NAPTR response.
2 The old SGSN will establish an
2 The new S4-SGSN will
inter-SGSN tunnel for transferring
continue to use the Gn interface
queued packets.
for the PDPs. Conversion of
PDPs to S4-SGSN is not
supported at this time.
1 No concept of subscribed default
APN.
1 One among the subscribed APN
will be indicated as a default
APN by the HSS. That APN
will be used under the following
cases: 1) No requested APN, 2)
The requested APN is not in the
subscription but the requested
PDP type matches with default
APN\'s PDP type.
Serving GPRS Support Node (SGSN) Overview
S4 Support on the SGSN
Procedure
DNS Queries
Path Failure Detection
Charging
Gn/Gp SGSN
S4-SGSN
1 APN FQDN, RAI FQDN and
1 APN FQDN, RAI FQDN,
RNC-ID FQDN are formed with a
RNC-ID FQDN are formed
.gprs extension.
with a .3gppnetwork.org
extension.
2 DNS A/AAAA records are queried.
2 DNS S-NAPTR records are
3 Optionally, also uses S-NAPTR
queried
queries for EPC-capable UEs to
select a co-located P-GW/GGSN 3 If DNS SNAPTR response
returns only Gn address,
S4-SGSN will use Gn interface
for selecting a PGW/GGSN.
1 Can be echo-based or
non-echo-based.
1 Echo-based only.
1 Applicable.
1 Charging for PDP contexts
applicable only if CAMEL is
used. However, the S4-SGSN
will continue to generate
M-CDRs. Also CAMEL is not
supported in S4-SGSN now.
Hence S4-SGSN only generates
M-CDRs. PDP related CDRs
are generated by SGW.
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Procedure
Gn/Gp SGSN
S4-SGSN
Intra-SGSN Inter System
1 For 2G to 3G handovers, the RABs 1 For 2G to 3G handovers, the
Handover (2G to 3G or 3G to
are not established in 3G after
RABs are not established in 3G
2G Inter RAT handovers)
handover. It is the function of the
after the handover. The
UE to initiate Service Request
S4-SGSN preserves the PDP
procedure to setup RAB.
without deactivation. For 3G to
2G handover, the QoS is not
2 For 3G to 2G handovers, the QoS
capped to 472 Kbps in 2G. The
is capped to 472 Kbps in 2G and
reason is that in GTPv2 the
the Update PDP Context Request
Modify Bearer Request initiated
initiated from 2G will carry the
from S4-SGSN upon 3G to 2G
capped QoS to GGSN.
RAU is defined only for
informing S-GW / P-GW of a
switch in tunnel IDs and change
in RAT type. This message
doesn\'t carry QoS. The
S4-SGSN relies on the P-GW
+ PCRF to decide the best QoS
for the informed RAT type and
lets the P-GW initiate a separate
modification procedure to set
the right QoS. In 16.0, during
3G to 2G handover, SGSN
internally caps the APN-AMBR
to 472 kbps and post handover,
it initiates a Modify Bearer
Command message to
SGW/PGW. If there are any
GBR bearers (conversational /
streaming class) with bit rate
greater than 472 kbps then those
GBR bearer PDPs will be
deactivated.
Direct Tunnel (DT) Activation Configuration enabling DT is
accomplished at various levels - the
Call Control Profile level, the RNC
level, and at the APN Profile level for
DT per APN/GGSN.
For a given UE, it is possible that one
PDN connection to an APN to a GGSN
uses DT while another PDN connection
to a different APN to a different GGSN
does not use DT. It all depends upon
whether or not the target GGSN
supports DT.
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Configuration for DT is only
available at Call Control Profile and
RNC levels as the S4-SGSN\'s DT
is between an SGW and an RNC.
In an S4-SGSN, either all PDPs of
a given UE use DT or none of them
use DT. So, combinations of some
PDPs using DT and some PDPs not
using DT is not possible.
Serving GPRS Support Node (SGSN) Overview
Session Recovery
Procedure
Gn/Gp SGSN
S4-SGSN
Handling Suspend from BSS
/ peer SGSN
PDPs are suspended at SGSN. Any
downlink data received at this point
will be queued by the SGSN.
PDPs are suspended at SGSN.
Downlink data buffering happens
at the PGW and not the SGSN
because the PDP suspension is
carried via a GTPv2 Suspend
Notification message from the
SGSN to the SGW to the PGW.
Session Recovery
Session recovery provides a seamless failover and reconstruction of subscriber session information in the
event of a hardware or software fault that prevents a fully attached user session from having the PDP contexts
removed or the attachments torn down.
Session recovery is performed by mirroring key software processes (e.g., session manager and AAA manager)
within the system. These mirrored processes remain in an idle state (in standby-mode) until they may be
needed in the case of a software failure (e.g., a session manager task aborts). The system spawns new instances
of "standby mode" session and AAA managers for each active control processor (CP) being used.
As well, other key system-level software tasks, such as VPN manager, are performed on a physically separate
packet processing card to ensure that a double software fault (e.g., session manager and VPN manager fail at
the same time on the same card) cannot occur. The packet processing card used to host the VPN manager
process is in active mode and is reserved by the operating system for this sole use when session recovery is
enabled.
The additional hardware resources required for session recovery include a standby System Management Card
and a standby packet processing card.
There are two modes for Session Recovery.
• Task recovery mode: One or more session manager failures occur and are recovered without the need
to use resources on a standby packet processor card. In this mode, recovery is performed by using the
mirrored "standby-mode" session manager task(s) running on active packet processor cards. The
"standby-mode" task is renamed, made active, and is then populated using information from other tasks
such as AAA manager.
• Full packet processing card recovery mode: Used when a packet processing card hardware failure
occurs, or when a packet processor card migration failure happens. In this mode, the standby packet
processor card is made active and the "standby-mode" session manager and AAA manager tasks on the
newly activated packet processor card perform session recovery.
Session/Call state information is saved in the peer AAA manager task because each AAA manager and session
manager task is paired together. These pairs are started on physically different packet processor cards to ensure
task recovery.
When session recovery occurs, the system reconstructs the following subscriber information:
• Data and control state information required to maintain correct call behavior
• Subscriber data statistics that are required to ensure that accounting information is maintained
• A best-effort attempt to recover various timer values such as call duration, absolute time, and others
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SGSN Pooling and Iu-Flex / Gb-Flex
For more information on session recovery use and session recovery configuration, refer to the Session Recovery
section in the System Administration Guide.
SGSN Pooling and Iu-Flex / Gb-Flex
This implementation allows carriers to load balance sessions among pooled SGSNs, to improve reliability
and efficiency of call handling, and to use Iu-Flex / Gb-Flex to provide carriers with deterministic failure
recovery.
The SGSN, with its high capacity, signaling performance, and peering capabilities, combined with its level
of fault tolerance, delivers many of the benefits of Flex functionality even without deploying SGSN pooling.
As defined by 3GPP TS 23.236, the SGSN implements Iu-Flex and Gb-Flex functionality to facilitate network
sharing and to ensure SGSN pooling for 2.5G and 3G accesses as both separate pools and as dual-access pools.
SGSN pooling enables the following:
• Eliminates the single point of failure between an RNC and an SGSN or between a BSS and an SGSN.
• Ensures geographical redundancy, as a pool can be distributed across sites.
• Minimizes subscriber impact during service, maintenance, or node additions or replacements.
• Increases overall capacity via load sharing across the SGSNs in a pool.
• Reduces the need/frequency for inter-SGSN RAUs. This substantially reduces signaling load and data
transfer delays.
• Supports load redistribution with the SGSN offloading procedure.
The SGSN Pooling and Iu-Flex / Gb-Flex feature is license controlled. Contact your Cisco Account or Support
representative for information on how to obtain a license.
Gb/Iu Flex Offloading
The SGSN supports Gb/Iu Flex subscriber offloading from one SGSN to another specific SGSN in a 2G/3G
pool.
In addition, the operator can configure the offloading Target NRI in P-TMSI, and the quantity to offload to
the Target. This can be used to provide load balancing, or to offload a single node in pool, take it out of service
for whatever reason (e.g., maintenance).
SGSN Supports Enhanced IMSI Range
From release 19.0 onwards, the IMSI range supported has been enhanced to "2500" from "1000". The IMSI
ranges configured must be unique; the SGSN selects the appropriate operator policy based on the IMSI range
of the UE. The operator can verify the configured IMSI ranges and the associated operator policy by issuing
the command "show config". The length of the description field in the imsi-range command under the SGSN
Global Configuration mode has been reduced from a maximum of "100" alphanumeric characters to "50"
alphanumeric characters. Reduction of the supported string size results in improvement of the boot up time.
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SGSN Support for RAI Based Query
SGSN Support for RAI Based Query
The SGSN now supports a RAI based query when NRI based query fails. A new CLI option rai-fqdn-fallback
is provided in the peer-nri-length CLI under the Call Control Profile Configuration, which allows the operator
to configure the SGSN's support to fallback on RAI based query when NRI based query fails.
This feature is not supported in the following scenarios:
• 2G Context Request and Identification Request messages are not supported.
• S4 support of this extensions for all applicable scenarios is not supported.
SGSN Support For Sending Extended Bits Bi-directionally
The SGSN now supports sending extended bitrates in both uplink and downlink directions. Extended bitrates
are included in both uplink and downlink direction when the negotiated birate indicates that extended birates
should be included in one direction. A new CLI ranap bidirectional-always ext-mbr-ie is added under the
RNC Configuration mode to enable sending extended bitrates bi-directionally.
SGSN support to Ignore PDP Data Inactivity
The SGSN supports options to configure PDP Data Inactivity detection duration and actions to be performed
on timeout under the APN-Profile. The following configurable actions are supported under APN-Profile in
case of PDP Data Inactivity detection in the PDP context:
1 De-activate all PDPs of the subscriber
2 De-activate all PDPs of the bundle (all linked PDPs)
3 Detach the subscriber. This action is triggered when:
• Data in-activity is detected for all PDPs
• Data in-activity is detected for any of the PDPs
On the Detection of the PDP Data Inactivity, depending on the configuration option the SGSN either de-activates
the PDP or detaches the subscriber.
A new CLI ignore-pdp-data-inactivity is added to provide an option under the IMEI-Profile to ignore PDP
Data Inactivity configuration for one or more IMEIs. On configuring this CLI, the SGSN ignores the application
of in-activity configuration (configured in the APN-Profile) for a specified set of IMEI's.
Important
The IMEI range or set of IMEI's are mapped to specific IMEI-Profile using the CLI configuration option
under Operator-policy.
For more information on the command see. Command Line Interface Reference.
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Short Message Service (SMS over Gd)
Short Message Service (SMS over Gd)
The SGSN implements a configurable Short Message Service (SMS) to support sending and receiving text
messages up to 140 octets in length. The SGSN handles multiple, simultaneous messages of both types: those
sent from the MS/UE (SMS-MO: mobile originating) and those sent to the MS/UE (SMS-MT: mobile
terminating). Short Message Service is disabled by default.
After verifying a subscription for the PLMN\'s SMS service, the SGSN connects with the SMSC (short message
service center), via a Gd interface, to relay received messages (from a mobile) using
MAP-MO-FORWARD-REQUESTs for store-and-forward.
In the reverse, the SGSN awaits messages from the SMSC via MAP-MT-FORWARD-REQUESTs and checks
the subscriber state before relaying them to the target MS/UE.
The SGSN will employ both the Page procedure and MNRG (mobile not reachable for GPRS) flags in an
attempt to deliver messages to subscribers that are absent.
The SGSN supports
• charging for SMS messages, and
• lawful intercept of SMS messages
For information on configuring and managing the SMS, refer to the SMS Service Configuration Mode section
in the Command Line Interface Reference.
SMS Authentication Repetition Rate
The SGSN provides an authentication procedures for standard GMM events like Attach, Detach, RAU, and
Service-Request, and SMS events such as Activate, all with support for 1-in-N Authenticate functionality.
The SGSN did not provide the capability to authenticate MO/MT SMS events.
Now, the authentication functionality has been expanded to the Gs interface where the SGSN now supports
configuration of the authentication repetition rate for SMS-MO and SMS-MT, for every nth event. This
functionality is built on existing SMS CLI, with configurable MO and/or MT. The default is not to authenticate.
SMSC Address Denial
Previously, the SGSN supported restricting MO-SMS and MT-SMS only through SGSN operator policy
configuration.
Now, the SGSN can restrict forwarding of SMS messages to specific SMSC addresses, in order to allow
operators to block SMS traffic that cannot be charged for. This functionality supports multiple SMSCs and
is configurable per SMSC address with a maximum of 10 addresses. It is also configurable for MO-SMS
and/or MT-SMS messages.
Status Updates to RNC
During MMGR recovery due to memory overload or demux migration leads to missing status updates for
RNC.As the result RNC status remains unavailable even when links towards RNC are up. The Session
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Target Access Restricted for the Subscriber Cause Code
Controller allows the Standby Session Managers along with Active Session Managers to fetch the status
updates.
Target Access Restricted for the Subscriber Cause Code
This enhancement is a 3GPP TS (29.274 and 29.060) release compliance enhancement. As per 3GPP TS
29.274 and TS 29.060,the source-serving node (MME/SGSN) is allowed to reject SGSN Context Request
(GTPv1) and Context Request (GTPv2) mobility management messages with "Target Access Restricted for
the subscriber" cause if target access is restricted for the subscriber based on the Access-Restriction-Data in
the subscription profile. The target node (MME/SGSN) is allowed to reject RAU/TAU with anyone one of
the following NAS Causes:
• 15 "No suitable cells in tracking area", or
• 13 "Roaming not allowed in this tracking area", or
• 12 "Tracking area not allowed"
New statistics have been introduced under "show egtpc statistics verbose" and "show sgtpc statistics verbose"
to reflect the context response sent and received with the new reject cause "Target Access Restricted for the
subscriber".
Rejecting RAU/TAU much early in call cycle results in reduced signaling.
Important
No new CLI is provided for GTP cause code mapping to EMM/NAS cause. RAU Reject will always be
sent with NAS cause "No suitable cells in location area" and TAU Reject will always be sent with EMM
cause "No suitable cells in Tracking Area".
Important
The MME and SGSN revert to the old behavior as per earlier releases if the peer node is not capable of
sending the RAT-TYPE IE in CONTEXT-REQ message.
For more information refer to the 3GPP TS 29.274 (section 7.3.6), TS 29.060 (section 7.5.4), TS 29.060 Annex
B (Table B.5: Mapping from Gn/Gp to NAS Cause values Rejection indication from SGSN) and TS 29.274
Annex C ( Table C.5: Mapping from S3/S16 to NAS Cause values Rejection indication from MME/S4-SGSN)
Topology-based Gateway (GW) Selection
Topology-based gateway selection is a mechanism defined by 3GPP to choose a gateway based on the
geographical (topological) proximity of the GGSN to the SGSN or the P-GW to the S-GW. The two being
co-located would have the highest priority. Topology-based selection is not allowed for roamers connected
to HPLMN access points (Home Routed Scenario).
DNS S-NAPTR returns a candidate list of GW nodes for each of the DNS queries. 3GPP TS 29.303 provides
an algorithm to feed these candidate lists and choose the topologically closer nodes among them. S-NAPTR
DNS query is supported by default on the S4-SGSN and, with Release 16, can be enabled for the Gn/Gp-SGSN.
The SGSN\'s Topology-based GW Selection feature supports two levels of sorting, first level is degree and
second level is order/priority, where order is for NAPTR records and priority is for SRV Records. Degree has
the highest preference.
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Threshold Crossing Alerts (TCA) Support
For details on the use and configuration of this feature, refer to the Topology-based Gateway Selection section
in the SGSN Administration Guide.
Threshold Crossing Alerts (TCA) Support
Thresholding on the system is used to monitor the system for conditions that could potentially cause errors
or outage. Typically, these conditions are temporary (i.e high CPU utilization, or packet collisions on a
network) and are quickly resolved. However, continuous or large numbers of these error conditions within a
specific time interval may be indicative of larger, more severe issues. The purpose of thresholding is to help
identify potentially severe conditions so that immediate action can be taken to minimize and/or avoid system
downtime.
The system supports Threshold Crossing Alerts for certain key resources such as CPU, memory, number of
sessions etc. With this capability, the operator can configure threshold on these resources whereby, should
the resource depletion cross the configured threshold, a SNMP Trap would be sent.
The following thresholding models are supported by the system:
• Alert: A value is monitored and an alert condition occurs when the value reaches or exceeds the configured
high threshold within the specified polling interval. The alert is generated then generated and/or sent at
the end of the polling interval.
• Alarm: Both high and low threshold are defined for a value. An alarm condition occurs when the value
reaches or exceeds the configured high threshold within the specified polling interval. The alert is
generated then generated and/or sent at the end of the polling interval.
Thresholding reports conditions using one of the following mechanisms:
• SNMP traps: SNMP traps have been created that indicate the condition (high threshold crossing and/or
clear) of each of the monitored values.
Generation of specific traps can be enabled or disabled on the chassis. Ensuring that only important faults get
displayed. SNMP traps are supported in both Alert and Alarm modes.
• Logs: The system provides a facility called threshold for which active and event logs can be generated.
As with other system facilities, logs are generated Log messages pertaining to the condition of a monitored
value are generated with a severity level of WARNING.
Logs are supported in both the Alert and the Alarm models.
• Alarm System: High threshold alarms generated within the specified polling interval are considered
"outstanding" until a the condition no longer exists or a condition clear alarm is generated. "Outstanding"
alarms are reported to the system's alarm subsystem and are viewable through the Alarm Management
menu in the Web Element Manager.
The Alarm System is used only in conjunction with the Alarm model.
Important
For more information on threshold crossing alert configuration, refer to the Thresholding Configuration
Guide.
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Tracking Usage of GEA Encryption Algorithms
Tracking Usage of GEA Encryption Algorithms
GPRS encryption algorithm (GEA) significantly affects the SGSN processing capacity based on the GEAx
level used - GEA1, GEA2, or GEA3.
Operators would like to be able to identify the percentages of their customer base that are using the various
GEA encryption algorithms. The same tool can also track the migration trend from GEA2 to GEA3 and allow
an operator to forecast the need for additional SGSN capacity.
New fields and counters have been added to the output generated by the show subscribers gprs-only|sgsn-only
summary command. This new information enables the operator to track the number of subscribers capable
of GEA0-GEO3 and to easily see the number of subscribers with negotiated GEAx levels.
Validation of MCC/MNC Values in the Old RAI Field
This feature is developed to comply with 3GPP TS 24.008. As per 3GPP TS 24.008, in some abnormal
instances the MCC stored in the Mobile Station (MS) contains elements which do not belong to the set {0, 1
... 9}. In such cases the Mobile Station should transmit the stored values using full hexadecimal encoding.
When receiving such an MCC, the network should treat the RAI as deleted. In some instances it is possible
that the MNC stored in the Mobile Station has the following:
• Digit 1 or 2 not in the set {0, 1 ... 9}
• Digit 3 not in the set {0, 1 ... 9, F} hex
In such cases the MS should transmit the stored values using full hexadecimal encoding. When receiving such
an MNC, the network should treat the RAI as deleted. The same handling is applicable for a network where
a 3-digit MNC is sent by the mobile station to a network using only a 2-digit MNC.
A validation check has been introduced to verify the MCC and MNC fields received in the old RAI IE in
Attach/RAU requests. When the MCC and MNC fields received in the RAU request (inter-SGSN) and are
invalid, the RAU request is rejected by SGSN. When the MCC and MNC fields received in the Attach Request
and are invalid, the identity of the MS is retrieved directly from the MS instead of sending identity request to
the peer node where peer SGSN identity is derived from the old-RAI.
Important
These feature is applicable for both 2G and 3G networks.
A new CLI command [no] rai-skip-validation has been introduced under both IuPS service and GPRS service
configuration modes. This new command enables/disables rejection of RAU requests with invalid MCC/MNC
values in the old RAI field. By default the old RAI MCC/MNC fields are validated. This command also
impacts the PTMSI attaches where the old RAI field is invalid. If the OLD RAI field is invalid and if the
validation is enabled through the new CLI command, the identity of the MS is requested directly from the
MS instead of the peer SGSN.
VLR Pooling via the Gs Interface
VLR Pooling, also known as Gs Pooling, helps to reduce call delays and call dropping, when the MS/UE is
in motion, by routing a service request to a core network (CN) node with available resources.
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Synchronization of Crash Events and Minicores between Management Cards
VLR pools are configured in the Gs Service, which supports the Gs interface configuration for communication
with VLRs and MSCs.
A pool area is a geographical area within which an MS/UE can roam without the need to change the serving
CN node. A pool area is served by one or more CN nodes in parallel. All the cells, controlled by an RNC or
a BSC belong to the same one (or more) pool area(s).
VLR hash is used when a pool of VLRs is serving a particular LAC (or list of LACs). The selection of VLR
from this pool is based on the IMSI digits. From the IMSI, the SGSN derives a hash value (V) using the
algorithm: [(IMSI div 10) modulo 1000]. Every hash value (V) from the range 0 to 999 corresponds to a single
MSC/VLR node. Typically many values of (V) may point to the same MSC/VLR node.
For commands to configure the VLR and pooling, refer to the "Gs Service Configuration Mode" section in
the Command Line Interface Reference.
Synchronization of Crash Events and Minicores between Management Cards
The crashlog is unique to each of the management cards, so if a crash occurs when card the "8" is active it
will be logged on card "8". A subsequent switchover would no longer display the crash in the log. To retrieve
this crash, a switch back over to card "8" has to be done. The crash event log and dumps are unique to active
and standby management cards, so if a crash occurs on an active card then the crash event log and related
dumps will be stored on an active card only. This crash information is not available on the standby card.
Whenever the cards switchover due to a crash in the active card, and crash information is no longer displayed
on the card which takes over. Crash information can be retrieved only from the current active card. To retrieve
the crash list of the other card a switchover is required again. To avoid this switchover and to obtain the crash
information from the standby card, synchronization between two management cards and maintaining latest
crash information is required.
The arriving crash event will be sent over to the standby SMC/MMIO and saved in the standby\'s crashlog
file in the similar manner. Minicore, NPU or kernel dumps on flash of active SMC/MMIO needs to be
synchronized to standby SMC/MMIO using the \'rsync\' command. When a crashlog entry or the whole list
is deleted through the CLI command, it should be erased on both active and standby SMCs/MMIOs. There
is no impact on memory. All the crash related synchronization activity will be done by the evlogd of standby
SMC/MIO card, as the standby evlogd is less loaded and the standby card has enough room for synchronization
activity. Therefore the performance of the system will not be affected.
Zero Volume S-CDR Suppression
This feature is developed to suppress the CDRs with zero byte data count, so that the OCG node is not
overloaded with a flood of CDRs. The CDRs can be categorized as follows:
• Final-cdrs: These CDRs are generated at the end of a context.
• Internal-trigger-cdrs: These CDRs are generated due to internal triggers such as volume limit, time limit,
tariff change or user generated interims through the CLI commands.
• External-trigger-cdrs: These CDRs are generated due to external triggers such as QoS Change, RAT
change and so on. All triggers which are not considered as final-cdrs or internal-trigger-cdrs are considered
as external-trigger-cdrs.
The customers can select the CDRs they want to suppress. A new CLI command [no] [default] gtpp
suppress-cdrs zero-volume { external-trigger-cdr | final-cdr | internal-trigger-cdr }is developed to enable
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How the SGSN Works
this feature. This feature is disabled by default to ensure backward compatibility. For more information see,
Command Line Interface Reference and Statistics and Counters Reference.
Important
This is a license controlled feature.
How the SGSN Works
This section illustrates some of the GPRS mobility management (GMM) and session management (SM)
procedures the SGSN implements as part of the call handling process. All SGSN call flows are compliant
with those defined by 3GPP TS 23.060.
First-Time GPRS Attach
The following outlines the setup procedure for a UE that is making an initial attach.
Figure 8: Simple First-Time GPRS Attach
This simple attach procedure can connect an MS via a BSS through the Gb interface (2.5G setup) or it can
connect a UE via a UTRAN through the Iu interface in a 3G network with the following process:
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First-Time GPRS Attach
Table 2: First-Time GPRS Attach Procedure
Step
Description
1
The MS/UE sends an Attach Request message to the SGSN. Included in the message is
information, such as:
• Routing area and location area information
• Mobile network identity
• Attach type
2
Authentication is mandatory if no MM context exists for the MS/UE:
• The SGSN gets a random value (RAND) from the HLR to use as a challenge to the MS/UE.
• The SGSN sends a Authentication Request message to the UE containing the random
RAND.
• The MS/UE contains a SIM that contains a secret key (Ki) shared between it and the HLR
called a Individual Subscriber Key. The UE uses an algorithm to process the RAND and
Ki to get the session key (Kc) and the signed response (SRES).
• The MS/UE sends a Authentication Response to the SGSN containing the SRES.
3
The SGSN updates location information for the MS/UE:
a) The SGSN sends an Update Location message, to the HLR, containing the SGSN number,
SGSN address, and IMSI.
b) The HLR sends an Insert Subscriber Data message to the "new" SGSN. It contains subscriber
information such as IMSI and GPRS subscription data.
c) The "New" SGSN validates the MS/UE in new routing area:
If invalid: The SGSN rejects the Attach Request with the appropriate cause code.
If valid: The SGSN creates a new MM context for the MS/UE and sends a Insert Subscriber Data
Ack back to the HLR.
d) The HLR sends a Update Location Ack to the SGSN after it successfully clears the old MM
context and creates new one
4
The SGSN sends an Attach Accept message to the MS/UE containing the P-TMSI (included if
it is new), VLR TMSI, P-TMSI Signature, and Radio Priority SMS.
At this point the GPRS Attach is complete and the SGSN begins generating M-CDRs.
If the MS/UE initiates a second call, the procedure is more complex and involves information exchanges and
validations between "old" and "new" SGSNs and "old" and "new" MSC/VLRs. The details of this combined
GPRS/IMSI attach procedure can be found in 3GPP TS23.060.
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PDP Context Activation Procedures
PDP Context Activation Procedures
The following figure provides a high-level view of the PDP Context Activation procedure performed by the
SGSN to establish PDP contexts for the MS with a BSS-Gb interface connection or a UE with a UTRAN-Iu
interface connection.
Figure 9: Call Flow for PDP Context Activation
The following table provides detailed explanations for each step indicated in the figure above.
Table 3: PDP Context Activation Procedure
Step
Description
1
The MS/UE sends a PDP Activation Request message to the SGSN containing an Access Point
Name (APN).
2
The SGSN sends a DNS query to resolve the APN provided by the MS/UE to a GGSN address.
The DNS server provides a response containing the IP address of a GGSN.
3
The SGSN sends a Create PDP Context Request message to the GGSN containing the information
needed to authenticate the subscriber and establish a PDP context.
4
If required, the GGSN performs authentication of the subscriber.
5
If the MS/UE requires an IP address, the GGSN may allocate one dynamically via DHCP.
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Network-Initiated PDP Context Activation Process
Step
Description
6
The GGSN sends a Create PDP Context Response message back to the SGSN containing the IP
Address assigned to the MS/UE.
7
The SGSN sends a Activate PDP Context Accept message to the MS/UE along with the IP
Address.
Upon PDP Context Activation, the SGSN begins generating S-CDRs. The S-CDRs are updated
periodically based on Charging Characteristics and trigger conditions.
A GTP-U tunnel is now established and the MS/UE can send and receive data.
Network-Initiated PDP Context Activation Process
In some cases, the GGSN receives information that requires it to request the MS/UE to activate a PDP context.
The network, or the GGSN in this case, is not actually initiating the PDP context activation -- it is requesting
the MS/UE to activate the PDP context in the following procedure:
Figure 10: Network-Initiated PDP Context Activation
The table below provides details describing the steps indicated in the graphic above.
Table 4: Network Invites MS/UE to Activate PDP Context
Step
Description
1
The GGSN receives a PDU with a static PDP address that the GGSN \'knows\' is for an MS/UE
in its PLMN.
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MS-Initiated Detach Procedure
Step
Description
2
The GGSN uses the IMSI in place of the PDP address and sends an SRI (send routing information
for GPRS) to the HLR.
The HLR sends an SRI response back to the GGSN. The response may include the access of the
target SGSN and it may also indicate it the MS/UE is not reachable, in which case it will include
the reason in the response message.
3
The GGSN sends a PDU Notification Request to the SGSN (if the address was received). If the
address was not received or if the MS/UE continues to be unreachable, the GGSN sets a flag
marking that the MS/UE was unreachable.
The notified SGSN sends a PDU Notification Response to the GGSN.
4
The SGSN determines the MS/UE\'s location and sets up a NAS connection with the MS/UE.
The SGSN then sends a Request PDP Context Activation message to the MS/UE.
5
If the MS/UE accepts the invitation to setup a PDP context, the MS/UE then begins the PDP
context activation process indicated in the preceding procedure.
MS-Initiated Detach Procedure
This process is initiated by the MS/UE for a range of reasons and results in the MS/UE becoming inactive as
far as the network is concerned.
Figure 11: MS-Initiated Combined GPRS/IMSI Detach
The following table provides details for the activity involved in each step noted in the diagram above.
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Supported Standards
Table 5: MS-Initiated Combined GPRS/IMSI Detach Procedure
Step
Description
1
The UE sends a Detach Request message to the SGSN containing the Detach Type, P-TMSI,
P-TMSI Signature, and Switch off indicator (i.e. if UE is detaching because of a power off).
2
The SGSN sends Delete PDP Context Request message to the GGSN containing the TEID.
The GGSN sends a Delete PDP Context Response back to the SGSN.
The SGSN stops generating S-CDR info at the end of the PDP context.
3
The SGSN sends a IMSI Detach Indication message to the MSC/VLR.
4
The SGSN sends a GPRS Detach Indication message to the MSC/VLR.
The SGSN stops generating M-CDR upon GPRS Detach.
5
If the detach is not due to a UE switch off, the SGSN sends a Detach Accept message to the UE.
6
Since the UE GPRS Detached, the SGSN releases the Packet Switched Signaling Connection.
Supported Standards
The SGSN services comply with the following standards for GPRS/UMTS and EPC wireless data services.
IETF Requests for Comments (RFCs)
• RFC-1034, Domain Names - Concepts and Facilities, November 1987; 3GPP TS 24.008 v7.8.0 (2007-06)
• RFC-1035, Domain Names - Implementation and Specification, November 1987; 3GPP TS 23.003
v7.4.0 (2007-06)
• RFC-2960, Stream Control Transmission Protocol (SCTP), October 2000; 3GPP TS 29.202 v6.0.0
(2004-12)
• RFC-3332, MTP3 User Adaptation Layer (M3UA), September 2002; 3GPP TS 29.202 v6.0.0 (2004-12)
• RFC-4187, Extensible Authentication Protocol Method for 3rd Generation Authentication and Key
Agreement (EAP-AKA), January 2006
• RFC-4666, Signaling System 7 (SS7) Message Transfer Part 3 (MTP3) - User Adaptation Layer (M3UA),
September 2006; 3GPP TS 29.202 v6.0.0 (2004-12)
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3GPP Standards
3GPP Standards
Table 6: 3GPP Standards Supported
3GPP Standard
R19.0
R20.0
R21.0
3GPP TS 9.60, 3rd Generation Partnership
v7.10.0 (2002-12) v7.10.0 (2002-12) v7.10.0 (2002-12)
Project; Technical Specification Group Core
Network; General Packet Radio Service (GPRS);
GPRS Tunnelling Protocol (GTP) across the Gn
and Gp Interface (R98).
3GPP TS 22.041, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group Services
and System Aspects; Operator Determined
Barring (ODB)
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 22.042, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group Services
and System Aspects; Network Identity and
Timezone (NITZ); Service description, Stage 1
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 23.003, 3rd Generation Partnership v10.5.0 (2012-03) v10.5.0 (2012-03) v10.5.0 (2012-03)
Project; Technical Specification Group Core
Network and Terminals; Numbering, addressing
and identification
3GPP TS 23.007, 3rd Generation Partnership
Project; Technical Specification Group Core
Network; Restoration procedures
v11.8.0 (2014-03) v11.8.0 (2014-03) v11.8.0 (2014-03)
3GPP TS 23.015, 3rd Generation Partnership
Project; Technical Specification Group Core
Network; Technical realization of Operator
Determined Barring (ODB)
v9.0.0 (2009-12)
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 23.016, 3rd Generation Partnership v9.1.0 (2010-03)
Project; Technical Specification Group Core
Network; Subscriber data management; Stage 2
v9.1.0 (2010-03)
v9.1.0 (2010-03)
3GPP TS 23.040, 3rd Generation Partnership
Project; Technical Specification Group Core
Network and Terminals; Technical realization
of the Short Message Service (SMS)
v9.3.0 (2010-09)
v9.3.0 (2010-09)
v9.3.0 (2010-09)
3GPP TS 23.060, 3rd Generation Partnership v11.9.0 (2014-03) v11.9.0 (2014-03) v11.9.0 (2014-03)
Project; Technical Specification Group Services
and System Aspects; General Packet Radio
Service (GPRS); Service description; Stage 2
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3GPP Standards
3GPP Standard
R19.0
R20.0
R21.0
3GPP TS 23.078, 3rd Generation Partnership v4.11.1 (2004-04) v4.11.1 (2004-04) v4.11.1 (2004-04)
Project; Technical Specification Group Core
Network; Customized Applications for Mobile
network Enhanced Logic (CAMEL) Phase 3 Stage 2 (Release 4)
3GPP TS 23.107, 3rd Generation Partnership v9.3.0 (2011-12)
Project; Technical Specification Group Services
and System Aspects; Quality of Service (QoS)
concept and architecture
v9.3.0 (2011-12)
v9.3.0 (2011-12)
3GPP TS 23.236, 3rd Generation Partnership v11.0.0(2012-09) v11.0.0(2012-09) v11.0.0(2012-09)
Project; Technical Specification Group Services
and System Aspects; Intra-domain connection
of Radio Access Network (RAN) nodes to
multiple Core Network (CN) nodes
3GPP TS 23.251, 3rd Generation Partnership v10.5.0 (2012-12) v10.5.0 (2012-12) v10.5.0 (2012-12)
Project; Technical Specification Group Services
and System Aspects; Network Sharing;
Architecture and functional description
3GPP TS 23.271, 3rd Generation Partnership v9.6.0 (2011-03)
Project; Technical Specification Group Services
and System Aspects; Functional stage 2
description of Location Services (LCS) (Release
9)
v9.6.0 (2011-03)
v9.6.0 (2011-03)
3GPP TS 23.401, 3rd Generation Partnership v11.9.0
Project; Technical Specification Group Services (2014-03-10)
and System Aspects; General Packet Radio
Service (GPRS) enhancements for Evolved
Universal Terrestrial Radio Access Network
(E-UTRAN) access (Release 9)
v11.9.0
(2014-03-10)
v11.9.0
(2014-03-10)
3GPP TS 24.007, 3rd Generation Partnership v10.0.0 (2011-03) v10.0.0 (2011-03) v10.0.0 (2011-03)
Project; Technical Specification Group Core
Network; Mobile radio interface signalling layer
3; General aspects
3GPP TS 24.008, 3rd Generation Partnership v11.8.0 (2013-09) v11.8.0 (2013-09) v11.8.0 (2013-09)
Project; Technical Specification Group Core
Network and Terminals; Mobile radio interface
Layer 3 specification; Core network protocols;
Stage 3
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3GPP Standards
3GPP Standard
R19.0
3GPP TS 24.011, 3rd Generation Partnership v7.1.0
(2009-2006)
Project; Technical Specification Group Core
Network and Terminals; Point-to-Point (PP)
Short Message Service (SMS) support on mobile
radio interface (Release 7)
R20.0
R21.0
v7.1.0
(2009-2006)
v7.1.0
(2009-2006)
3GPP TS 24.030, 3rd Generation Partnership v10.0.0 (2011-04) v10.0.0 (2011-04) v10.0.0 (2011-04)
Project; Technical Specification Group Services
and System Aspects; General Packet Radio
Service (GPRS) enhancements for Evolved
Universal Terrestrial Radio Access Network
(E-UTRAN) access (Release 9)
3GPP TS 24.080, 3rd Generation Partnership v9.2.0 (2010-06)
Project; Technical Specification Group Core
Network and Terminals; Mobile radio interface
layer 3 supplementary services specification;
Formats and coding (Release 9)
v9.2.0 (2010-06)
v9.2.0 (2010-06)
3GPP TS 25.410, 3rd Generation Partnership v9.0.1 (2011-03)
Project; Technical Specification Group Radio
Access Network; UTRAN Iu Interface: general
aspects and principles
v9.0.1 (2011-03)
v9.0.1 (2011-03)
3GPP TS 25.411, 3rd Generation Partnership
Project; Technical Specification Group Radio
Access Network; UTRAN Iu interface layer 1
v9.0.1 (2011-03)
v9.0.1 (2011-03)
v9.0.1 (2011-03)
3GPP TS 25.412, 3rd Generation Partnership v9.0.1 (2011-03)
Project; Technical Specification Group Radio
Access Network; UTRAN Iu interface signaling
transport
v9.0.1 (2011-03)
v9.0.1 (2011-03)
3GPP TS 25.413, 3rd Generation Partnership 12.0.0 (2013-12)
Project; Technical Specification Group Radio
Access Network; UTRAN Iu interface RANAP
signalling (Release 9)
12.0.0 (2013-12)
12.0.0 (2013-12)
3GPP TS 25.414, 3rd Generation Partnership
Project; Technical Specification Group Radio
Access Network; UTRAN Iu interface data
transport and transport signaling
v9.0.1 (2011-03)
v9.0.1 (2011-03)
v9.0.1 (2011-03)
3GPP TS 25.415, 3rd Generation Partnership v9.0.1 (2011-03)
Project; Technical Specification Group Radio
Access Network; UTRAN Iu interface user plane
protocols
v9.0.1 (2011-03)
v9.0.1 (2011-03)
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3GPP Standards
3GPP Standard
R19.0
3GPP TS 29.002, 3rd Generation Partnership
Project; Technical Specification Group Core
Network and Terminals; Mobile Application
Part (MAP) specification
v12.0.0 (2013-03) v12.0.0 (2013-03) v12.0.0 (2013-03)
3GPP TS 29.016, 3rd Generation Partnership v8.0.0 (2008-12)
Project; Technical Specification Group Core
Network; General Packet Radio Service (GPRS);
Serving GPRS Support Node (SGSN) - Visitors
Location Register (VLR); Gs interface network
service specification
R20.0
v8.0.0 (2008-12)
R21.0
v8.0.0 (2008-12)
3GPP TS 29.018, 3rd Generation Partnership v10.7.0 (2012-09) v10.7.0 (2012-09) v10.7.0 (2012-09)
Project; Technical Specification Group Core
Network and Terminals; General Packet Radio
Service (GPRS); Serving GPRS Support Node
(SGSN) - Visitors Location Register (VLR) Gs
interface layer 3 specification
3GPP TS 29.060,3rd Generation Partnership
v12.0.0 (2013-03) v12.0.0 (2013-03) v12.0.0 (2013-03)
Project; Technical Specification Group Core
Network and Terminals; General Packet Radio
Service (GPRS); GPRS Tunnelling Protocol
(GTP) across the Gn and Gp interface
3GPP TS 29.078, 3rd Generation Partnership v4.9.0
(2009-2009)
Project; Technical Specification Group Core
Network; Customized Applications for Mobile
network Enhanced Logic (CAMEL) Phase 3;
CAMEL Application Part (CAP) specification
(Release 4)
v4.9.0
(2009-2009)
v4.9.0
(2009-2009)
3GPP TS 29.202, 3rd Generation Partnership
Project; Technical Specification Group Core
Network and Terminals; SS7 Signalling
Transport in Core Network; Stage 3
v8.0.0 (2007-06)
v8.0.0 (2007-06)
v8.0.0 (2007-06)
3GPP TS 29.272, 3rd Generation Partnership v12.0.0 (2013-03) v12.0.0 (2013-03) v12.0.0 (2013-03)
Project; Technical Specification Group Core
Network and Terminals; Evolved Packet System
(EPS); Mobility Management Entity (MME) and
Serving GPRS Support Node (SGSN) related
interfaces based on Diameter protocol (Release
9)
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3GPP Standards
3GPP Standard
R19.0
R20.0
R21.0
3GPP TS 29.274, 3rd Generation Partnership v11.9.0 (2013-12) v11.9.0 (2013-12) v11.9.0 (2013-12)
Project; Technical Specification Group Core
Network and Terminals; 3GPP Evolved Packet
System (EPS); Evolved General Packet Radio
Service (GPRS) Tunnelling Protocol for Control
plane (GTPv2-C); Stage 3 (Release 9)
3GPP TS 29.303, 3rd Generation Partnership v10.4.0 (2012-09) v10.4.0 (2012-09) v10.4.0 (2012-09)
Project; Technical Specification Group Core
Network and Terminals; Domain Name System
Procedures; Stage 3 (Release 9)
3GPP TS 32.215, 3rd Generation Partnership v5.9.0 (2007-10)
Project; Technical Specification Group Services
and System Aspects; Telecommunication
management; Charging management; Charging
data description for the Packet Switched (PS)
domain
v5.9.0 (2007-10)
v5.9.0 (2007-10)
3GPP TS 32.251, 3rd Generation Partnership v9.8.0
Project; Technical Specification Group Services
and System Aspects; Telecommunication
management; Charging management; Packet
Switched (PS) domain charging
v9.8.0
v9.8.0
3GPP TS 32.298, 3rd Generation Partnership
Project; Technical Specification Group Service
and System Aspects; Telecommunication
management; Charging management; Charging
Data Record (CDR) parameter description
v8.7.0
(2009-2012)Fully compliant
v8.7.0
(2009-2012)Fully compliant
v8.7.0
(2009-2012)Fully compliant
v9.6.0 (
2010-2012) Partially
complaint (IMSI
unAuth and CSG
Information not
supported)
v9.6.0 (
2010-2012) Partially
complaint (IMSI
unAuth and CSG
Information not
supported)
v9.6.0 (
2010-2012) Partially
complaint (IMSI
unAuth and CSG
Information not
supported)
3GPP TS 32.406, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group Services
and System Aspects; Telecommunication
management; Performance Management (PM);
Performance measurements Core Network (CN)
Packet Switched (PS) domain
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 32.410, 3rd Generation Partnership v9.0.0 (2009-09)
Project; Technical Specification Group Services
and System Aspects; Telecommunication
management; Key Performance Indicators (KPI)
for UMTS and GSM
v9.0.0 (2009-09)
v9.0.0 (2009-09)
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3GPP Standards
3GPP Standard
R20.0
R21.0
3GPP TS 33.102, 3rd Generation Partnership v9.4.0 (2010-12)
Project; Technical Specification Group Services
and System Aspects; 3G Security; Security
architecture
v9.4.0 (2010-12)
v9.4.0 (2010-12)
3GPP TS 33.106, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group Services
and System Aspects; 3G security; Lawful
Interception requirements
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 33.107, 3rd Generation Partnership v9.4.0 (2011-03)
Project; Technical Specification Group Services
and System Aspects; 3G security; Lawful
interception architecture and functions
v9.4.0 (2011-03)
v9.4.0 (2011-03)
3GPP TS 33.108, 3rd Generation Partnership v7.10.0
Project; Technical Specification Group Services (2010-2012)
and System Aspects; 3G security; Handover
interface for Lawful Interception (LI) (Release
7)
v7.10.0
(2010-2012)
v7.10.0
(2010-2012)
3GPP TS 44.064, 3rd Generation Partnership v9.1.0 (2011-12)
Project; Technical Specification Group Core
Network and Terminals; Mobile Station Serving GPRS Support Node (MS-SGSN);
Logical Link Control (LLC) layer specification
v9.1.0 (2011-12)
v9.1.0 (2011-12)
3GPP TS 44.065, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group Core
Network and Terminals; Mobile Station (MS) Serving GPRS Support Node (SGSN);
Subnetwork Dependent Convergence Protocol
(SNDCP)
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 48.014, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group GSM
EDGE Radio Access Network; General Packet
Radio Service (GPRS); Base Station System
(BSS) - Serving GPRS Support Node (SGSN)
interface; Gb interface Layer 1
v9.0.0 (2009-12)
v9.0.0 (2009-12)
3GPP TS 48.016, 3rd Generation Partnership v9.0.0 (2009-12)
Project; Technical Specification Group GSM
EDGE Radio Access Network; General Packet
Radio Service (GPRS); Base Station System
(BSS) - Serving GPRS Support Node (SGSN)
interface; Network Service
v9.0.0 (2009-12)
v9.0.0 (2009-12)
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R19.0
Serving GPRS Support Node (SGSN) Overview
ITU Standards
3GPP Standard
R19.0
R20.0
R21.0
3GPP TS 48.018, 3rd Generation Partnership v11.5.0 (2013-11) v11.5.0 (2013-11) v13.1.0 (2016-04)
Project; Technical Specification Group
GSM/EDGE Radio Access Network; General
Packet Radio Service (GPRS); Base Station
System (BSS) - Serving GPRS Support Node
(SGSN); BSS GPRS Protocol (BSSGP) (Release
7)
ITU Standards
• Q711; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q712; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q713; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q714; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q715; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q716; 3GPP TS 29.002 v7.15.0 (2006-2010), 3GPP TS 29.016 v7.0.0 (2007-08), and 3GPP TS 25.410
v7.0.0 (2006-03)
• Q771; 3GPP TS 29.002 v7.15.0 (2006-2010)
• Q772; 3GPP TS 29.002 v7.15.0 (2006-2010)
• Q773; 3GPP TS 29.002 v7.15.0 (2006-2010)
• Q774; 3GPP TS 29.002 v7.15.0 (2006-2010)
• Q775; 3GPP TS 29.002 v7.15.0 (2006-2010)
Object Management Group (OMG) Standards
• CORBA 2.6 Specification 01-09-35, Object Management Group
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CHAPTER
2
SGSN in a 2.5G GPRS Network
• SGSN in a 2.5G GPRS Network, page 91
• 2.5G SGSN Configuration Components, page 92
• How the 2.5G SGSN Works , page 94
• Information Required for the 2.5G SGSN, page 97
SGSN in a 2.5G GPRS Network
This chapter outlines the basic configuration and operation of the Serving GPRS Support Node (SGSN) in
2.5G GPRS wireless data networks.
The simplest configuration that can be implemented on the system to support SGSN functionality in a 2.5G
network requires one context but we recommend a minimum of two: one for the SGSN service (required) and
another for the charging context.
The service context organizes the following:
• GPRS service configuration
• MAP (Mobile Application Part) configuration
• DNS (Domain Naming System) configuration for resolution of APN (Access Point Name) domain names
• SGTP (SGSN GPRS Tunneling Protocol) configuration
The charging context facilitates the following:
• Configuration of connectivity to the CGF (Charging Gateway Function)
The following functionality is configured at the global or system level in the local management context:
• NSEI (Network Service Entity Identity) configuration
• SCCP (Signalling Connection Control Part) network configuration
• SS7 (Signaling System 7) connectivity configuration
• GTT (Global Title Translation) configuration
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2.5G SGSN Configuration Components
To simplify configuration management, more contexts can be created to categorize the service configuration.
Each context can be named as needed. The contexts listed above can be configured as illustrated in the figure
on the next page.
2.5G SGSN Configuration Components
In order to support 2.5G SGSN functionality, the system must be configured with at least one context for the
GPRS service (2.5G SGSN service). In the example below, the required context has been named "SGSN_Ctx".
Figure 12: Sample 2.5G SGSN Configuration
The SGSN_Ctx
As indicated, there must be at least one context to contain the service and routing configurations.
Although multiple context can be created, our example configuration uses only one context, named
"SGSN_Ctx", to contain all of the following configurations:
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The SGSN_Ctx
• SS7 Routing Domain - SS7 routing is facilitated through the configuration and use of SS7 routing
domains. SS7 routing domains group SS7-related configuration parameters. Depending on the SS7
signalling method, an SS7 routing domain may be configured with one of the following:
◦Linksets - Used for broadband SS7 signalling, linksets are comprised of link ids that specify point
codes for SCCP endpoints. It is important to note that SCCP endpoints are further defined through
the configuration of SCCP Networks which are associated with the SS7 routing domain in which
the linkset is configured.
◦Application Server Processes (ASPs) / Peer Server Processes (PSPs) - Used for IP (SIGTRAN),
M3UA ASPs and PSPs dictate the IP address and port information used to facilitate communication
between network endpoints. ASPs refer to the local endpoints.
• GTT - Global Title Translation (GTT) configuration consists of defining GTT associations, defining
GTT address maps, and referring to these in an SCCP network configuration.The GTT Associations
define GTT rules. The GTT Address Maps define a GTT database. These are configured in the Global
Configuration mode and are available to all SCCP networks configured in the system.
• SCCP Network - SCCP (Signalling Connection Control Part) networks are a concept specific to this
platform. SCCP networks apply only to SS7 applications using SCCP. The purpose of an SCCP network
is to isolate the higher protocol layers above SCCP and the application itself from SS7 connectivity
issues, as well as, to provide a place for global SCCP configuration specific to SGSN services. Use the
following example configuration to specify a global SCCP configuration specific to SGSN services.
• MAP Service - The Mobile Application Part (MAP) is an SS7 protocol which provides an application
layer for the various nodes in GSM and UMTS mobile core networks and GPRS core networks to
communicate with each other in order to provide services to mobile phone users. MAP is the
application-layer protocol used to access the Home Location Register (HLR), Visitor Location Register
(VLR), Mobile Switching Center (MSC), Equipment Identity Register (EIR), Authentication Center
(AUC), Short Message Service Center (SMSC) and Serving GPRS Support Node (SGSN).
The primary facilities provided by MAP are:
◦Mobility Services: location management (when subscribers move within or between networks),
authentication, managing service subscription information, fault recovery.
◦Operation and Maintenance: subscriber tracing, retrieving a subscriber's IMSI.
◦Call Handling: routing, managing calls while roaming, checking that a subscriber is available to
receive calls.
◦Supplementary Services.
◦SMS
◦Packet Data Protocol (PDP) services for GPRS: providing routing information for GPRS
connections.
◦Location Service Management Services: obtaining the location of subscribers.
• SGTP Service- The SGSN GPRS Tunneling Protocol (GTP) service specifies the GTP settings for the
SGSN. At a bare minimum, an address to use for GTP-C (Control signaling) and an address for GTP-U
(User data) must be configured.
• GPRS Service- All of the parameters needed for the system to perform as a an SGSN in a GPRS network
are configured in the GPRS service. The GPRS service uses other configurations such as SGTP and
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The Accounting_Ctx
MAP to communicate with other network entities and setup communications between the BSS and the
GGSN.
• NSEI (Network Service Entity Instance)- This identifies the NSEI to use and associates it with a Network
Service Virtual Connection Identifier.
• DNS- DNS Client configurations provide DNS configuration in a context to resolve APN domain names.
The Accounting_Ctx
If no context is defined for GTPP configuration, the SGSN automatically generates an accounting context
with default GTPP configurations. The context, from our example, contains the following configuration:
• GTPP Configuration - This configuration specifies how to connect to the GTPP charging servers.
• Ga Interface - This is an IP interface.
How the 2.5G SGSN Works
In compliance with 3GPP specifications, the 2.5G SGSN supports standard operational procedures such as:
attach, detach, PDP activation.
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For GPRS and/or IMSI Attach
For GPRS and/or IMSI Attach
The following illustrates the step-by-step call flow indicating how the 2.5G SGSN handles a GPRS/IMSI
attach procedure.
Figure 13: GPRS/IMSI Attach Procedure
1 An Attach Request message is sent from the UE to the SGSN by the BSS over the Gb interface. This is
Typically a Frame Relay connection.
2 The SGSN identifies UE and determines IMSI. Depending on whether or not the UE is already attached,
this could be a simple database lookup or it could require the SGSN to communicate with an SGSN that
may have been previously handling the call.
3 The SGSN communicates with the HLR to authenticate the UE.
4 Once the UE has been authenticated, the SGSN communicates with the EIR to verify that the equipment
is not stolen.
5 Once equipment check is complete, the SGSN communicates with the HLR to update UE location
information.
6 The SGSN then sends an Attach Complete message to UE.
7 SGSN begins sending M-CDR data to the CG.
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For PDP Activation
For PDP Activation
The following provides a step-by-step illustration indicating how the 2.5G SGSN handles a PDP activation
procedure.
Figure 14: PDP Activation Procedure
1 A PDP Activation Request message is sent from the UE to the SGSN by the BSS over the Gb interface.
This request includes the Access Point Name (APN) the UE is attempting to connect to. This is typically
a Frame relay connection.
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Information Required for the 2.5G SGSN
2 The SGSN queries the DNS server to resolve the APN to the IP address of the GGSN to use to establish
the PDP context.
3 The SGSN sends a Create PDP Context Request message to the GGSN. This message identifies the APN
the UE is attempting to connect to and other information about the subscriber.
4 The GGSN performs its processes for establishing the PDP context. This may include subscriber
authentication, service provisioning, etc. The GGSN eventually sends an affirmative create PDP context
response to the SGSN containing the IP address assigned to the UE.
5 The SGSN sends an Activate PDP Context Accept message back to the UE. The subscriber can now begin
sending/receiving data.
6 The SGSN begins generating S-CDR data that will be sent to the CG.
Information Required for the 2.5G SGSN
This section describes the minimum amount of information required to configure the SGSN to be operational
in a 2.5G GPRS network. To make the process more efficient, we recommend that this information be collected
and available prior to configuring the system.
There are additional configuration parameters that deal with fine-tuning the operation of the SGSN in the
network. Information on these parameters is not provided here but can be found in the appropriate configuration
command chapters in the Command Line Interface Reference.
Global Configuration
Table 7: Required Information for Global Configuration
Required Information
Description
NSEI (Network Service Entity)
NSVL Instance ID
A unique ID number to identify the NSVL instance
Peer Network Service Entity
The name or NSEI index number of a peer NSE.
SS7 Routing Domain For Broadband SS7 Signaling
SS7 Routing Domain ID
A unique ID number from 1 through 12 to identify the SS7 Routing
Domain.
SS7 Routing Domain Variant
The network variant for the SS7 Routing Domain.
Sub Service Field
The Sub Service Field selector that this SS7 Routing Domain should
use.
Linkset ID
A unique ID number from 1 through 49 to identify the linkset.
Linkset Self Point Code
A point code for the specified network variant that will identify the
system when using this linkset.
Adjacent Point Code
The pointcode of the entity that the system will use to communicate
for SS7 signaling when this linkset is used.
Link ID
A unique ID number from 1 through 16 that identitfies the MTP3 link.
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Global Configuration
Required Information
Description
Priority
An MTP3 priority number from 0 through 15 for the link.
Signaling Link Code
A number from 0 through 15 that is unique from all other SLCs in the
linkset.
Arbitration
Whether the link will use passive or active arbitration.
SS7 Routing Domain to Support IP SS7 Signaling for SIGTRAN
SS7 Routing Domain ID
A unique ID number from 1 through 12 to identify the SS7 Routing
Domain.
SS7 Routing Domain Variant
The network variant for the SS7 Routing Domain.
Sub Service Field
The Sub Service Field selector that this SS7 Routing Domain should
use.
ASP Instance ID
A unique ID number from 1 through 4 to use for the M3UA ASP
instance.
ASP Instance Endpoint
The IP address and Port if needed of an interface that will be used as
this ASP instance end point. If the interface was created in a context
other than the current context, that context name is also needed.
Peer Server ID
A unique ID number from 1 through 49 to use for the M3UA peer
server configuration.
Peer Server Name
A name for the Peer Server configuration. Usually this is the name of
the SS7 network entity that this instance is configured to communicate
with. HLR, VLR, or EIR for example.
Routing Context ID
The ID of the M3UA routing context used to reach this peer server.
Peer Server Process ID
A unique number from 1 through 4 used to identify each PSP process
for the current peer server.
Peer server self-point-code
The point code to identify the peer server process being configured.
PSP Mode
Specify whether this peer server process will be used to communicate
with the peer server in client or server mode.
Exchange Mode
Specify whether this peer server process will use double or single-ended
mode for exchanges with the peer server.
SCTP End Point Address
A local SCTP end point address configured in an ASP instance that
this peer server process will use.
ASP Association
The ID of a configured ASP instance that this peer server process will
be associated with.
GTT
GTT Association
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There are many different ways to configure a GTT Association and
the needs of every network are different. Please refer to the Global
Title Translation Association Configuration Mode chapter in the
Command Line Interface Reference for the commands available.
SGSN in a 2.5G GPRS Network
SGSN Context Configuration
Required Information
Description
GTT Address Map
There are many different ways to configure a GTT Address Map and
the needs of every network are different. Please refer to the Global
Title Translation Address Map Configuration Mode chapter in the
Command Line Interface Reference for the commands available.
SCCP Network
SCCP Network ID
A unique number from 1 through 12 with which to identify the SCCP
configuration.
SCCP Variant
The network variant for the SCCP network configuration.
Self Point Code
The point code that the system will use to identify itself when using
this SCCP configuration.
SS7 Routing Domain Association
The ID number of the SS7 routing Domain with which to associate
this SCCP network configuration.
GTT Association
The ID number of the GTT Association to use with this SCCP network
configuration.
GTT Address Map
The ID number of the GTT Address Map to use with this SCCP
network configuration.
SCCP Destination
The point code, version, and susbsystem number of the SCCP entity
with which to communicate.
SGSN Context Configuration
Table 8: Required Information for SGSN Context Configuration
Required Information
Description
SGSN context name
An identification string from 1 to 79 characters (alpha and/or numeric)
by which the SGSN context will be recognized by the system.
MAP service Configuration
MAP Service name
A unique name with which to identify an individual MAP service.
SCCP Network ID
The ID of the SCCP network configuration to use for SS7 connectivity
for SCCP applications.
EIR Address
The ISDN or point code of the EIR.
HLR Mapping
The IMSI prefixes and associated HLR point codes and the point code
for the default HLR.
SGTP Service
SGTP Service Name
A unique alpha and /or numeric name for the SGTP service
configuration.
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Accounting Context Configuration
Required Information
Description
GTPC Address
An IP address that is associated with an interface in the current context.
This is used for GTP-C.
GTPU Address
An IP address that is associated with an interface in the current context.
This is used for GTP-U.
GPRS Service
GPRS Service Name
a unique name to identify this GPRS service.
PLMN ID
The MCC and MNC for the SGSN service to use to identify itself in
the PLMN.
Core Network ID
The core Network ID for this SGSN service to use to identify itself on
the core network.
SGSN Number
The E.164 number to use to identify this SGSN.
MAP Service Name
The name of a MAP service that this SGSN service will use for MAP.
If the MAP service is not in the same context, the context name of the
MAP service must also be specified.
Network Service Entity Identifier
The ID of a configured Network Service Entity Identifier (NSEI) and
the RAC and LAC that this SGSN should use.
DNS Client
Name Server Addresses
The IP addressees of Domain Naming Servers i n the network.
DNS CLient Name
A unique name for the DNS client.
DNS Client Address
The IP address of an Interface in the current context that the DNS is
bound to.
Accounting Context Configuration
Table 9: Required Information for Accounting Context Configuration
Required Information
Description
Context name
An identification string from 1 to 79 alphanumeric characters by which
the SGSN context will be recognized by the system. Our example uses
the name Accounting_Ctx.
GTPP Charging
GTTP Group Name
If you are going to configure GTTP accounting server groups, you
will need to name them.
Charging Agent Address
The IP address of an interface in the current context that to use for the
Ga interface to communicate with the CGFs.
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Accounting Context Configuration
Required Information
Description
GTTP Server
The IP address and priority to use to contact the GTTP server.
GTTP Dictionary Name
The name of the GTTP dictionary to use.
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Accounting Context Configuration
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CHAPTER
3
SGSN 3G UMTS Configuration
• SGSN 3G UMTS Configuration , page 103
• 3G SGSN Configuration Components, page 104
• Information Required for 3G Configuration, page 106
SGSN 3G UMTS Configuration
This chapter outlines the basic deployment, configuration, and operation of the system to function as a Serving
GPRS Support Node (SGSN) in 3G UMTS wireless data networks.
The simplest configuration that can be implemented on the system to support SGSN functionality in a 3G
network requires one context but we recommend a minimum of two: one for the SGSN service (required) and
another for the charging context.
The SGSN context facilitates the following:
• SGSN service configuration
• Mobile Application Part (MAP) configuration
• IuPS (Iu Packet Switched) interface configuration for communication with the RAN (Radio Access
Network)
• DNS (Domain Naming System) Client configuration for resolution of APN domain names
• SGTP (SGSN GPRS Tunneling Protocol) configuration
The charging context facilitates the following:
• Configuration of connectivity to the CGF (Charging Gateway Function)
The following functionality is configured at the global system level:
• SCCP (Signalling Connection Control Part) network configuration
• SS7 (Signaling System 7) connectivity configuration
• GTT (Global Title Translation) configuration
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3G SGSN Configuration Components
To simply configuration management, more contexts can be created and used and all context can be named
as needed. The contexts listed above can be configured as illustrated in the figure on the next page.
Note
With the SGSN, all configuration and created contexts, reside within the "local" or management context
which is described in the System Administration Guide.
3G SGSN Configuration Components
In order to support 3G SGSN functionality, the system must be configured with at least one context for the
SGSN (UMTS) service . In the example below, the required context has been named "SGSN_Ctx".
Figure 15: Sample 3G Network Configuration
This configuration uses two contexts:
• SGSN Context containing:
◦Contains SGSN and related services
◦DNS Configuration
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For GPRS and/or IMSI Attach
• Accounting Context containing:
◦GTPP configuration
For GPRS and/or IMSI Attach
Figure 16: GPRS/IMSI Attach Procedure
1 An Attach Request message is sent from the UE to the SGSN by the RNC over the IuPS interface.
2 The SGSN identifies UE and determines IMSI. Depending on whether or not the UE is already attached,
this could be a simple database lookup or it could require the SGSN to communicate with an SGSN that
may have been previously handling the call.
3 The SGSN communicates with the HLR to authenticate the UE.
4 Once the UE has been authenticated, the SGSN communicates with the EIR to verify that the equipment
is not stolen.
5 Once equipment check is complete, the SGSN communicates with the HLR to update UE location
information.
6 The SGSN then sends an Attach Complete message to UE.
7 SGSN begins sending M-CDR data to the CG.
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Information Required for 3G Configuration
Information Required for 3G Configuration
The following sections describe the minimum amount of information required to configure and make the
SGSN operational on the network. To make the process more efficient, it is recommended that this information
be available prior to configuring the system.
There are additional configuration parameters that are not described in this section. These parameters deal
mostly with fine-tuning the operation of the SGSN in the network. Information on these parameters can be
found in the appropriate sections of the Command Line Interface Reference.
Global Configuration
Table 10: Required Information for Global Configuration
Required Information
Description
SS7 Routing Domain to Support IP SS7 Signaling for SIGTRAN for the IuPS Interface
SS7 Routing Domain ID
A unique ID number from 1 through 12 to identify the SS7 Routing
Domain.
SS7 Routing Domain Variant
The network variant for the SS7 Routing Domain.
Sub Service Field
The Sub Service Field selector that this SS7 Routing Domain should
use.
ASP Instance ID
A unique ID number from 1 through 4 to use for the M3UA ASP
instance.
ASP Instance Endpoint
The IP address and port (if needed) of an interface that will be used
as this ASP instance end point.
ASP Instance Endpoint Context
The name of the context in which the interface associated with this
routing domain is configured
Peer Server ID
A unique ID number from 1 through 49 to use for the M3UA peer
server configuration.
Peer Server Name
A name for the Peer Server configuration. Usually this is the name of
the SS7 network entity that this instance is configured to communicate
with. HLR, VLR, or EIR for example.
Peer Server Mode
The mode of operation for the peer server.
Routing Context ID
The ID of the M3UA routing context used to reach this peer server.
Self Point Code
The point code that the peer server will be routed to for its destination.
Peer Server Process (PSP) ID
A unique number from 1 through 4 used to identify each PSP process
for the current peer server.
PSP Mode
Specify whether this peer server process will be used to communicate
with the peer server in client or server mode.
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Global Configuration
Required Information
Description
Exchange Mode
Specify whether this peer server process will use double or
single-ended mode for exchanges with the peer server.
SCTP End Point Address
A local SCTP end point address configured in an ASP instance that
this peer server process will use. For the IuPS service, this is the
address of the RNC.
ASP Association
The ID of a configured ASP instance that this peer server process will
be associated with.
SS7 Routing Domain to Support IP SS7 Signaling for SIGTRAN for the Gr Interface
SS7 Routing Domain ID
A unique ID number from 1 through 12 to identify the SS7 Routing
Domain.
SS7 Routing Domain Variant
The network variant for the SS7 Routing Domain.
Sub Service Field
The Sub Service Field selector that this SS7 Routing Domain should
use.
ASP Instance ID
A unique ID number from 1 through 4 to use for the M3UA ASP
instance.
ASP Instance Endpoint
The IP address and Port (if needed) of an interface that will be used
as this ASP instance end point.
ASP Instance Endpoint Context
The name of the context in which the interface associated with this
routing domain is configured
Peer Server ID
A unique ID number from 1 through 49 to use for the M3UA peer
server configuration.
Peer Server Name
A name for the Peer Server configuration. Usually this is the name of
the SS7 network entity that this instance is configured to communicate
with. HLR, VLR, or EIR for example.
Peer Server Mode
The mode of operation for the peer server.
Routing Context ID
The ID of the M3UA routing context used to reach this peer server.
Self Point Code
The point code that the peer server will be routed to for its destination.
Peer Server Process ID
A unique number from 1 through 4 used to identify each PSP process
for the current peer server.
PSP Mode
Specify whether this peer server process will be used to communicate
with the peer server in client or server mode.
Exchange Mode
Specify whether this peer server process will use double or
single-ended mode for exchanges with the peer server.
SCTP End Point Address
A local SCTP end point address configured in an ASP instance that
this peer server process will use. For the IuPS service, this is the
address of the HLR.
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Global Configuration
Required Information
Description
ASP Association
The ID of a configured ASP instance that this peer server process will
be associated with.
SCCP Network for the IuPS Interface
SCCP Network ID
A unique number from 1 through 12 with which to identify the SCCP
configuration.
SCCP Variant
The network variant for the SCCP network configuration.
Self Point Code
The point code that the system will use to identify itself when using
this SCCP configuration.
SS7 Routing Domain Association
The ID number of the SS7 routing Domain with which to associate
this SCCP network configuration.
SCCP Destination Point Code
The point code for the SCCP destination entity. For the IuPS interface,
this is the RNC\'s point code
SCCP Destination Name
The name by which the SCCP destination will be known by the system
SCCP Destination Version
The SCCP variant.
SCCP Destination Subsystem
Number
The subsystem number (SSN) of the SCCP destination.
SCCP Network for the Gr Interface
SCCP Network ID
A unique number from 1 through 12 with which to identify the SCCP
configuration.
SCCP Variant
The network variant for the SCCP network configuration.
Self Point Code
The point code that the system will use to identify itself when using
this SCCP configuration.
SS7 Routing Domain Association
The ID number of the SS7 routing Domain with which to associate
this SCCP network configuration.
SCCP Destination Point Code
The point code for the SCCP destination entity. For the IuPS interface,
this is the RNC\'s point code
SCCP Destination Name
The name by which the SCCP destination will be known by the system
SCCP Destination Version
The SCCP variant.
SCCP Destination Subsystem
Number
The subsystem number (SSN) of the SCCP destination.
Port Configuration
Bind-to Interface Name
The name of the logical interface to bind the port to.
Bind-to Interface Context Name
The name of the context in which the logical interface is configured.
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SGSN Context Configuration
SGSN Context Configuration
Table 11: Required Information for SGSN Context Configuration
Required Information
Description
SGSN context name
An identification string from 1 to 79 characters (alpha and/or numeric)
by which the SGSN context will be recognized by the system.
Logical Interface Name
The name by which the logical interface will be known by the system.
Logical Interface Addresses
IP addresses and subnets are assigned to the logical interface(s) which
are then associated with physical ports.
MAP service Configuration
MAP Service name
A unique name with which to identify an individual MAP service.
SCCP Network ID
The ID of the SCCP network configuration to use for SS7 connectivity
for SCCP applications.
HLR IMSI Mapping
The IMSI prefixes for the HLR associated with this service.
HLR Point Code
The point code of the HLR to map to the IMSIs
Iu-PS Service
IuPS Service Name
A unique name to identify the IuPS service.
SCCP Network ID
The ID of the SCCP network configuration to use for SS7 connectivity
for SCCP applications.
GTPU Address
The address of an IP interface defined in the current context to use for
GTPU connections to the RNC.
RNC ID
A unique ID number from 0 through 4095 for this RNC configuration
and the MCC and MNC associated with the RNC.
RNC MCC
The mobile country code (MCC) associated with the RNC.
RNC MNC
The mobile network code (MNC) associated with RNC.
RNC Point Code
The SS7 point code for the specified RNC.
LAC ID
The location area code (LAC) ID associated with the RNC.
RAC ID
The routing area code (RAC) ID associated with the RNC.
SGTP Service
SGTP Service Name
A unique alpha and /or numeric name for the SGTP service
configuration.
GTP-C Address
An IP address that is associated with an interface in the current context.
This is used for GTP-C over the Gn and/or Gp interface.
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SGSN Context Configuration
Required Information
Description
GTP-U Address
An IP address that is associated with an interface in the current context.
This is used for GTP-U over the Gn and/or Gp interface.
SGSN Service
SGSN Service Name
a unique name to identify this SGSN service.
Core Network ID
The core Network ID for this SGSN service to use to identify itself
on the core network.
SGSN Number
The E.164 number to use to identify this SGSN.
MAP Service Name
The name of a MAP service that this SGSN service will use for MAP.
MAP Service Context
The context in which the MAP service is configured.
Maximum PDP Contexts
The maximum number of contexts each UE can establish at one time.
IuPS Service Name
The name of a configured IuPS service to use with the SGSN
configuration. If the IuPS service is not in the same context, the context
name of the IuPS service must also be specified.
IuPS Service Context
The context in which the IuPS service is configured.
SGTP Service Name
The name of the SGTP service that this SGSN service will use to for
GTP.
SGTP Service Context
The context in which the SGTP service is configured.
Accounting Context Name
By default, the SGSN service looks for the GTPP accounting
configuration in the same context as the SGSN service. If GTPP
accounting is configured in a different context the context name must
be specified.
DNS Client Configuration
Name Server Addresses
The IP addresses of Domain Name Service (DNS) servers in the
network.
DNS CLient Name
A unique name for the DNS client configured on the system.
DNS Client Address
The IP address of an Interface in the current context that the DNS is
bound to.
DNS Client Port
The UDP port to use for DNS communications.
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Accounting Context Configuration
Accounting Context Configuration
Table 12: Required Information for Accounting Context Configuration
Required Information
Description
Accounting Context Name
An identification string from 1 to 79 characters (alpha and/or numeric)
by which the context will be recognized by the system.
Ga Interface Name
The name by which the logical interface used as the Ga interface will
be known by the system.
Ga Interface Address
The IP address and subnet for the Ga interface.
GTPP Charging
GTTP Group Name
If you are going to configure GTTP accounting Server groups, you
will need to name them.
Charging Agent Address
The IP address of an interface in the current context that to use for the
Ga interface to communicate with the CGFs.
GTTP Server
The IP address and priority to use to contact the GTTP server.
GTTP Dictionary Name
The name of the GTTP dictionary to use.
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Accounting Context Configuration
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CHAPTER
4
SGSN Service Configuration Procedures
• SGSN Service Configuration Procedures, page 114
• 2.5G SGSN Service Configuration, page 114
• 3G SGSN Service Configuration, page 116
• Dual Access SGSN Service Configuration , page 117
• Configuring the S4-SGSN, page 118
• Configuring an SS7 Routing Domain, page 120
• Configuring GTT, page 123
• Configuring an SCCP Network, page 124
• Configuring a MAP Service, page 125
• Configuring an IuPS Service (3G only), page 126
• Configuring an SGTP Service, page 126
• Configuring a Gs Service, page 127
• Configuring an SGSN Service (3G only), page 128
• Configuring a GPRS Service (2.5G only), page 129
• Configuring a Network Service Entity, page 130
• Configuring DNS Client, page 132
• Configuring GTPP Accounting Support, page 132
• Configuring and Associating the EGTP Service (S4 Only), page 135
• Configuring and Associating the GTPU Service (S4 Only), page 136
• Configuring the DNS Client Context for APN and SGW Resolution (Optional), page 137
• Configuring the S6d Diameter Interface (S4 Only), page 138
• Configuring the S13' Interface (S4 Only, Optional), page 143
• Configuring QoS Mapping for EPC-Capable UEs using the S4 Interface (S4 Only, Optional), page 147
• Configuring the Peer SGSN Interface Type (S4 Only, Optional), page 148
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SGSN Service Configuration Procedures
• Configuring Gn Interface Selection Based on an Operator Policy (S4 Only, Optional), page 149
• Configuring a Custom MME Group ID (S4 Only, Optional), page 150
• Configuring and Associating the Selection of an SGW for RAI (S4 Only, Optional), page 151
• Configuring a Local PGW Address (S4 Only, Optional), page 152
• Configuring the Peer MME Address (S4 Only, Optional), page 153
• Configuring the ISR Feature (S4 Only, Optional), page 154
• Configuring IDFT for Connected Mode Handover (S4 Only, Optional), page 155
• Creating and Configuring ATM Interfaces and Ports (3G only), page 156
• Creating and Configuring Frame Relay Ports (2.5G only), page 156
• Configuring APS/MSP Redundancy, page 157
SGSN Service Configuration Procedures
This chapter provides configuration instructions to enable the SGSN to function in GPRS (2.5G), UMTS
(3G), or LTE (4G) networks. The System Administration Guide provides interface and system-level
configuration details and the Command Line Interface Reference provides additional command information.
Important
Please note that LTE (4G) support is only available in releases 14.0 an higher.
Important
At least one packet processing card must be activated prior to configuring the first service. Procedures for
configuring the packet processing card can be found in the System Administration Guide.
High level step-by-step service configuration procedures are provided for the following:
2.5G SGSN Service Configuration
The following configuration steps must be completed to allow the system to operate in a 2.5G GPRS network.
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2.5G SGSN Service Configuration
The service handling the GPRS or 2.5G functions in the SGSN is called the "gprs-service".
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
Step 13
Step 14
Create all the contexts you will use in your configuration. Refer to the "System Element Configuration Procedures"
chapter in the System Administration Guide.
Create and configure the Frame Relay interface(s) and Ethernet interface(s). Refer to the "System Element Configuration
Procedures" chapter in the System Administration Guide.
Configure SS7 routing domains. Use the procedure in Configuring an SS7 Routing Domain, on page 120. The concept
of an SS7 routing domain is not a standard SS7 concept. It is a concept specific to this platform which groups a set of
SS7 feature configuration together to facilitate the management of the SS7 connectivity resources for an SGSN service.
Configure GTT. The GTT configuration is used to set rules for GTT and define the GTT databases. Follow the procedure
in Configuring GTT, on page 123
Configure SCCP-Networks. The purpose of an SCCP network is to isolate the higher protocol layers above SCCP and
the application itself from SS7 connectivity issues, as well as, to provide a place for global SCCP configuration specific
to SGSN services. Use the procedure in Configuring an SCCP Network, on page 124
Configure MAP services. The MAP service configuration is used by the SGSN service to communicate with many of
the nodes on the narrow band-SS7 network part of the network such as HLR, EIR, GSM-SCF, GMLC and
SMS-GMSC/SMS-IWMSC. The purpose of having an isolated map configuration is to enable different application
services to use the map service to communicate with other map entities in the network. Use the procedure in Configuring
a MAP Service, on page 125
Configure SGTP. The SGTP service configures the parameters used for GTP Tunneling. At the minimum, interfaces for
GTP-C and GTP-U must be configured. Use the procedure in Configuring an SGTP Service, on page 126
Configure the SGSN service. All the parameters specific to the operation of an SGSN are configured in the SGSN service
configuration mode. SGSN services use other configurations like MAP and IuPS to communicate with other elements
in the network. The system can support multiple gprs-services.
Configure the GPRS service. All of the parameters needed for the system to perform as a an SGSN in a GPRS network
are configured in the GPRS service. The GPRS service uses other configurations such as SGTP and MAP to communicate
with other network entities and setup communications between the BSS and the GGSN. Use the procedure in Configuring
a GPRS Service (2.5G only), on page 129
Configure the Network Service Entity Instance. This identifies the NSEI to use and associates it with a Network Service
Virtual Connection Identifier. Use the procedure in Configure a Network Service Entity for IP, on page 130
Configure DNS. This configuration enables domain name resolution and specifies the DNSs to use for lookup. Use the
procedure in Configuring DNS Client, on page 132
Configure GTPP Accounting. This configures GTPP-based accounting for subscriber PDP contexts. Use the procedure
in Configuring GTPP Accounting Support, on page 132
Configure Frame Relay DLCI paths and bind them to NSEI links as needed. Refer to Creating and Configuring Frame
Relay Interfaces and Ports in the System Administration Guide.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide and the Command Line Interface Reference.
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3G SGSN Service Configuration
3G SGSN Service Configuration
The following configuration steps must be completed to allow the system to operate in a 3G network.
Step 1
Create the contexts needed. Refer to the System Element Configuration Procedures chapter in the System Administration
Guide.
Step 2
Create any interfaces needed in the appropriate context. Refer to the System Element Configuration Procedures chapter
in the System Administration Guide for IP (broadcast Ethernet) interfaces and for ATM interfaces.
Configure SS7 routing domains. The SS7 routing domain is proprietary concept to provide a combined configuration
for the SS7 links, linksets, and related parameters. SS7 routing domain configurations are common to both SIGTRAN
and MTP3-B networks. Use the procedure in Configuring an SS7 Routing Domain, on page 120
Configure global title translations (GTT). The GTT configuration is used to set rules for GTT and to define the GTT
databases. Follow the procedure in Configuring GTT, on page 123
Configure SCCP networks. The SCCP network (layer) provides services to protocol layers higher in the SS7 protocol
stack, for example RANAP and TCAP. The SCCP layer is also responsible for GTT. As well, all the SS7 routing domains
(created in step 3) will be associated with an SCCP network. Use the procedure in Configuring an SCCP Network, on
page 124
Configure MAP services. The MAP service configuration is used by the SGSN service to communicate with many of
the nodes in the SS7 network, such as the HLR, EIR, GSM-SCF, GMLC and SMS-GMSC/SMS-IWMSC. Having an
isolated MAP configuration enables different application services to use the MAP service to communicate with other
MAP entities in the network. Use the procedure in Configuring a MAP Service, on page 125
Configure IuPS services. A set of parameters define the communication path between the SGSN service and radio network
controllers (RNCs) in a UMTS IuPS service. Use the procedure in Configuring an IuPS Service (3G only), on page 126
Configure SGTP services. The SGTP service configures the parameters used for GTP Tunneling. At a minimum, interfaces
for GTP-C and GTP-U must be configured. Use the procedure in Configuring an SGTP Service, on page 126
Configure the SGSN service. All the parameters specific to the operation of an SGSN are configured in the SGSN service
configuration mode. SGSN services use other service configurations like MAP (map-service) and IuPS (iups-service)
to communicate with other elements in the network.
Configure DNS clients. This configuration enables domain name resolution and specifies the DNSs to use for lookup.
Use the procedure in Configuring DNS Client, on page 132
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
Step 13
Step 14
Optional: Configure operator policies. Operator policies are not required for SGSN operation, however, they provide
the operator with a powerful method for determining call handling. SGSN operator policies specify rules governing the
services, facilities and privileges available to a single subscriber or groups of subscribers. Use the procedure in Configuring
SGSN Operator Policies.
Configure GTPP Accounting. This configures GTPP-based accounting for subscriber PDP contexts. Use the procedure
in Configuring GTPP Accounting Support, on page 132
Configure ATM PVCs and bind them to interfaces or SS7 links as needed. Refer to Creating and Configuring ATM
Interfaces and Ports in the System Administration Guide.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide and the Command Line Interface Reference.
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Dual Access SGSN Service Configuration
The following configuration steps must be completed to allow the SGSN to operate in both GPRS (2.5G) and
UMTS (3G) networks. This type of co-location is referred to as dual access.
To configure dual access requires a combination of steps from both the 2.5G and 3G configuration procedures:
Step 1
Create the contexts needed. Refer to the System Element Configuration Procedures chapter in the System Administration
Guide.
Step 2
Create any interfaces needed in the appropriate context refer to the System Element Configuration Procedures chapter
in the System Administration Guide.
a) For IP (broadcast Ethernet) interfaces, refer to Creating and Configuring Ethernet Interfaces and Ports in the System
Administration Guide.
b) For ATM interfaces (3G) refer to Creating and Configuring ATM Interfaces and Ports in the System Administration
Guide.
c) For Frame Relay interfaces (2.5G) refer to Creating and Configuring Frame Relay Interfaces and Ports in the System
Administration Guide.
Step 3
Configure SS7 routing domains. The SS7 routing domain is a non-standard, proprietary SS7 concept specific to this
platform. SS7 routing domains provide a combined configuration for the SS7 links, linksets, and related parameters for
SS7 connectivity resources for an SGSN service. SS7 routing domain configurations are common to both SIGTRAN
and MTP3-B networks. Use the procedure in Configuring an SS7 Routing Domain, on page 120
Configure global title translations (GTT). The GTT configuration is used to set rules for GTT and to define the GTT
databases. Follow the procedure in Configuring GTT, on page 123
Configure SCCP networks. The SCCP network (layer) provides services to protocol layers higher in the SS7 protocol
stack, for example RANAP and TCAP. The SCCP layer is also responsible for GTT (step 4) and every SS7 routing
domain (step 3) will be associated with an SCCP network. Use the procedure in Configuring an SCCP Network, on
page 124
Configure MAP services. The MAP service configuration is used by the SGSN service to communicate with many of
the nodes in the SS7 network, such as the HLR, EIR, GSM-SCF, GMLC and SMS-GMSC/SMS-IWMSC. Having an
isolated MAP configuration enables different application services to use the MAP service to communicate with other
MAP entities in the network. Use the procedure in Configuring a MAP Service, on page 125
Configure IuPS services. A set of parameters define the communication path between the SGSN service and radio network
controllers (RNCs) in a UMTS IuPS service. Use the procedure in Configuring an IuPS Service (3G only), on page 126
Configure SGTP services. The SGTP service configures the parameters used for GTP Tunneling. At a minimum, interfaces
for GTP-C and GTP-U must be configured. Use the procedure in Configuring an SGTP Service, on page 126
Configure the GPRS service. All of the parameters needed for the system to perform as a an SGSN in a GPRS network
are configured in the GPRS service. The GPRS service uses other service configurations, such as SGTP (sgtp-service)
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
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Step 10
Step 11
Step 12
and MAP (map-service) to communicate with other network entities and setup communications between the BSS and
the GGSN. Use the procedure in Configuring a GPRS Service (2.5G only), on page 129
Configure the Network Service Entity Instance. This identifies the NSEI to use and associates it with a Network Service
Virtual Connection Identifier. Use the procedure in Configuring a Network Service Entity, on page 130
Configure DNS. This configuration enables domain name resolution and specifies the DNSs to use for lookup. Use the
procedure in Configuring DNS Client, on page 132
Configure GTPP Accounting. This configures GTPP-based accounting for subscriber PDP contexts. Use the procedure
in Configuring GTPP Accounting Support, on page 132
Step 13
Configure ATM PVCs and bind them to interfaces or SS7 links as needed. Refer to Creating and Configuring ATM
Interfaces and Ports in the System Administration Guide.
Step 14
Configure Frame Relay DLCI paths and bind them to NSEI links as needed. Refer to Creating and Configuring Frame
Relay Interfaces and Ports in the System Administration Guide.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide and the Command Line Interface Reference.
Step 15
Configuring the S4-SGSN
The following configuration steps comprise the required and optional tasks for configuring the S4-SGSN to
provide an interface between GPRS (2.5G) / UMTS (3G) networks and EPC (4G) networks via the EPC S4
interface. This is referred to as an S4-SGSN.
Important
The S4-SGSN cannot operate until after 2G, 3G, or dual access SGSN service is configured. Do not begin
S4-SGSN configuration until one of those services is configured and operational. Refer to the 2.5G SGSN
Service Configuration, on page 114, Configuring an SGSN Service (3G only), on page 128 , or Dual
Access SGSN Service Configuration , on page 117 sections in this chapter for details on configuring those
services.
Before you begin the configuration procedure, note the following:
• Configuration steps 1 through 5 are mandatory for the S4-SGSN to operate properly.
• Configuration steps 6 through 15 are optional. They can be used to configure or enable various optional
functionality and features, including:
◦Bypass DNS resolution for various network elements
◦Configure GUTI-to-RAI mapping
◦Configure operator-specific QoS mapping values
◦Configure the S13' interface for the Mobile Equipment Identity (MEI) check
◦Configure the license-enabled Idle Mode Signaling Reduction feature
◦Configure the Indirect Data Forwarding Tunnel feature
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Important
Step 1
Step 2
Step 3
Step 4
Step 5
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configure, 2G, 3G or Dual Access SGSN service support. Refer to the Configuring a GPRS Service (2.5G only), on
page 129, 3G SGSN Service Configuration, on page 116, or Dual Access SGSN Service Configuration , on page 117
sections in this chapter for the configuration
Configure and associate the EGTP service. The EGTP service is required to support communication between the SGSN
and the EPC SGW over the S4 interface using the GTPv2 protocol. Refer to the Configuring and Associating the EGTP
Service (S4 Only), on page 135 procedure.
Configure and associate the GTPU service. The GTPU service supports the configured EGTP service by enabling the
sending and receiving of GTP bearer packets from the EPC SGW over the S4 intereface. Refer to the Configuring and
Associating the GTPU Service (S4 Only), on page 136 procedure.
Configure DNS for APN resolution. Configurables must be set to enable the default DNS client on the SGSN to resolve
EPC PGW and SGW addresses. Refer to the Configuring the DNS Client Context for APN and SGW Resolution
(Optional), on page 137 procedure.
Configure the S6d Diameter Interface. The S6d interface is used by the SGSN to communicate with the HSS. The HSS
is a master user database that contains all subscription related information, Refer to the Configuring the S6d Diameter
Interface (S4 Only), on page 138 procedure.
Step 6
Optional. Configure the S13' (S13 prime) interface. This interface is used to perform Mobile Equipment (ME) identity
check procedure between the SGSN and Equipment Identity Registry. Refer to the Configuring the S13' Interface (S4
Only, Optional), on page 143 procedure.
Step 7
Optional. Configure operator-specific QoS mapping between EPC elements and the SGSN. The S4-SGSN communicates
QoS parameters towards the SGW/ PGW and EPC UEs in different formats. Operators must configure the SGSN quality
of service (QoS) parameters as a call-control-profile that will ensure proper QoS mapping between the S4-SGSN,
SGW/PGW and UEs. Refer to the Configuring QoS Mapping for EPC-Capable UEs using the S4 Interface (S4 Only,
Optional), on page 147 procedure.
Step 8
Optional. Configure the interface type used by the S4-SGSN to communicate with the peer SGSN. Refer to the Configuring
the Peer SGSN Interface Type (S4 Only, Optional), on page 148 procedure.
Step 9
Optional. Configure Gn interface selection for EPC-capable UEs based on an operator policy. When the EGTP service
is configured, the SGSN, by default, selects the S4 interface for 1) EPC capable UEs and 2) non-EPC capable UEs that
have an EPS subscription only. However, operators have the option to forcefully select the Gn interface for both types
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of UEs. Refer to the Configuring Gn Interface Selection Based on an Operator Policy (S4 Only, Optional), on page 149
procedure.
Step 10
Optional. Configure a custom MME group ID. For operators who are using LAC ranges between 32768 and 65535 in
UMTS/GPRS deployments, rather than for MMEs in LTE deployments, the SGSN provides a workaround to ensure
backward compatibility. Refer to the Configuring a Custom MME Group ID (S4 Only, Optional), on page 150 procedure.
Step 11
Optional. Configure the S-GW for a RAI. If operators wish to bypass DNS resolution for obtaining the EPC S-GW
address, the S4-SGSN can select a locally configured S-GW by performing a local look-up for the current RAI. Refer
to the Configuring and Associating the Selection of an SGW for RAI (S4 Only, Optional), on page 151 procedure.
Step 12
Optional. Configure a Local PGW Address. For operators who wish to bypass DNS resolving an EPC P-GW address,
the SGSN can be configured with a local P-GW address as part of an APN profile. Refer to the Configuring a Local
PGW Address (S4 Only, Optional), on page 152 procedure.
Step 13
Optional. Configure the peer MME address. If operators wish to bypass DNS to resolve the peer MME address, the
SGSN supports the local configuration of a peer MME address for a given MME group (LAC) and MME code (RAC).
Refer to Configuring the Peer MME Address (S4 Only, Optional), on page 153 procedure.
Step 14
Optional. Configure the Idle Mode Signaling Reduction (ISR) feature. The ISR is a license-enabled feature allows the
UE to roam between LTE and 2G/3G networks while reducing the frequency of TAU and RAU procedures due to the
UE selecting E-UTRAN or UTRAN networks. Refer to the Configuring the ISR Feature (S4 Only, Optional), on page
154 procedure.
Step 15
Optional. Enable the setup of indirect data forwarding tunnels (IDFT) between the eNodeB and the RNC via the SGW
during connected mode handovers. This allows for connected mode handovers between the UTRAN and E-UTRAN
networks across the S3 (S4-SGSN-to-MME) interface. Refer to Configuring IDFT for Connected Mode Handover (S4
Only, Optional), on page 155.
Configuring an SS7 Routing Domain
The SGSN supports both SS7- and IP-based routing. IP-based routing is provided through the use of contexts.
SS7 routing is facilitated through the configuration and use of SS7 routing domains. SS7 routing domains
group SS7-related configuration parameters. Depending on the SS7 signaling method, an SS7 routing domain
may be configured with one of the following:
• Linksets: Used for broadband SS7 signaling, linksets are comprised of link ids that specify point codes
for SCCP endpoints. It is important to note that SCCP endpoints are further defined through the
configuration of SCCP Networks (refer to Configuring an SCCP Network) which are associated with
the SS7 routing domain in which the linkset is configured.
• Application Server Processes (ASPs) / Peer Server Processes (PSPs): Used for IP (SIGTRAN), M3UA
ASPs and PSPs dictate the IP address and port information used to facilitate communication between
network endpoints. ASPs refer to the local endpoints.
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Configuring an SS7 Routing Domain to Support Broadband SS7 Signaling
Configuring an SS7 Routing Domain to Support Broadband SS7 Signaling
Step 1
In global configuration mode, create a new SS7 routing domain, give it a unique ID and specify the network variant that
SS7 communications through this routing domain use.
In SS7 routing domain configuration mode, configure the MTP-3 sub-service field (SSF).
Create an SS7 linkset with a unique ID.
In linkset configuration mode, specify the self point code - this is the point code of the SGSN.
Specify the adjacent point code to communicate with another SS7 node, e.g., an RNC.
Configure individual links, identified with link IDs.
In link configuration mode, specify the MTP3 link priority.
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Specify the Signaling Link Code (SLC) for this link. This must be unique to this link within the current linkset. Note
that SLCs must match, one-to-one, with those defined for the peer nodes.
Configure this link to use either passive or active arbitration.
In SS7 routing domain configuration mode, configure SS7 routes by specifying destination point codes and associated
linkset IDs.
Example Configuration
configure
ss7-routing-domain id variant variant
ssf subsvc
linkset id id
self-point-code #.#.#
adjacent-point-code #.#.#
link id id
priority pri
signaling-link-code code
arbitration arbitration
exit
exit
route destination-point-code dpc linkset-id id
end
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Configuring an SS7 Routing Domain to Support IP Signaling for SIGTRAN
Configuring an SS7 Routing Domain to Support IP Signaling for SIGTRAN
To configure IP, the SS7 routing domain must be configured in a specific way as described below:
Step 1
In Global configuration mode, create a new SS7 routing domain, give it a unique ID and specify the network variant that
SS7 communications through this routing domain use.
In SS7 Routing Domain configuration mode, configure the MTP-3 subservice field.
Create an ASP (Application Service Part) instance for M3UA ASP configuration and give it a unique ID.
Specify the local SCTP (Stream Control Transmission Protocol) end-point IP address and the name of the context where
the IP interface associated with the address is configured.
Important
At least one address needs to be configured before the end-point can be activated.
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
Step 12
Step 13
Step 14
Step 15
Step 16
Specify the end-point SCTP port address to be used. Default port address is 2905.
Bind the end-point to the application server process (ASP) instance to activate it.
In SS7 routing domain configuration mode, create a peer server configuration with a unique ID.
Name the peer server configuration. Usually this is the name of the SS7 network entity that this instance is configured
to communicate with, for example an HLR, an STP, or an RNC.
Specify the M3UA routing context ID.
Create a PSP instance and give it a unique ID.
In PSP configuration mode, specify the PSP mode in which this PSP instance should operate.
Specify the communication mode this PSP instance should use as client or server.
Configure the exchange mode this PSP instance should use. Generally this is not configured for IPSP-SG configuration,
e.g., SGSN and STP.
Configure the IP address of the peer node SCTP end-point for this PSP instance. At least one address needs to be
configured before the end-point can be activated. Up to two addresses can be configured.
Specify the ID of the ASP instance with which to associate this PSP instance.
Configure SS7 routes, in SS7 routing domain configuration mode, by specifying destination point codes and peer server
IDs. Routes are configured if the destination point code (DPC) is at least a hop away from the SGSN or when the DPC
is not the same as the peer server. For example, the route is configured between the SGSN and the HLR which
communicates through STPs or signaling gateways. In this case, the signaling gateways are configured as the peer server
on the SGSN.
Example Configuration
configure
ss7-routing-domain id variant variant
ssf subsvc
asp instance instance_id
end-point address address context ctxt_name
end-point bind
exit
peer-server id id
name name
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routing-context ctxt_id
psp instance id
psp-mode mode
exchange-mode mode
end-point address address
associate asp instance id
exit
exit
route destination-point-code dpc peer-server-id id
end
Configuring GTT
Global Title Translation (GTT) configuration consists of defining GTT associations, defining GTT address
maps, and referring to these in an SCCP network configuration. The GTT Associations define GTT rules
applicable to a specific GT format. The GTT Address Maps define a global title address to be routed to using
a specific routing indicator. These are configured in the global configuration mode and are available to all
SCCP networks configured in the system.
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
In global configuration mode, create a GTT association with a unique name.
In GTT association configuration mode, define the type of digit analysis to be used; "fixed" is the generally used digit
analysis and if specified, also define the length of the digits to be analyzed. This is represented using action IDs.
In GTT association configuration mode, define the GT format (1 to 4) for which the analysis needs to be applied.
In the GT format configuration mode, specify the numbering plan and the nature of address to be used. Note that a
separate GTT association needs to be created for a combination of numbering plan, nature of address, and GT format.
Important
There are many different ways to configure a GTT association and the needs of every network are different.
Please refer to the Global Title Translation Association Configuration Mode chapter in the Command Line
Interface Reference for the commands available.
In global configuration mode, create a GTT address map, with a unique name, for a specific global title address.
In GTT address map configuration mode, associate a specific GTT association and the action ID.
In GTT address map configuration mode, define the routing indicator to be included in the Called-party Address in the
out-going SCCP message along with the destination of the message using the option out-address.
Important
There are many different ways to configure a GTT Address Map and the needs of every network are different.
Please refer to the GTT Address Map Configuration Mode chapter in the Command Line Interface Reference
for the commands available.
Example Configuration
configure
global-title-translation association instance <inst#>
action id <id> type <action_type> start-digit <num> end-digit <num>
gt-format <format_num>
exit
global-title-translation address-map instance <inst#>
associate gtt-association <assoc#> action id <id>
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gt-address <gt_addr_prefix>
out-address <name>
ssf <sub_svc_fld>
routing-indicator <route_ind>
ni-indicator <addr_ind>
ssn <sub_sys_num>
point-code <pt_code>
end
Configuring an SCCP Network
SCCP (Signaling Connection Control Part) networks are a concept specific to this platform. The SCCP network
provides services to protocol layers higher in the SS7 protocol stack, e.g., RANAP and TCAP. This layer is
also responsible for GTT. Every SS7 routing domain will be associated with an SCCP network. Use the
following example configuration to specify a global SCCP configuration specific to SGSN services.
Important
A total of 12 SCCP networks can be configured.
To configure an SCCP network:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
In global configuration mode, specify an identification number for this SCCP network configuration and the signaling
variant.
Specify the self point code of the SGSN.
Specify the SS7 routing domain with which to associate this SCCP network configuration.
If using GTT (Global Title Translation), specify the name of a GTT address map to use.
Configure a destination point code and give it a name.
Configure the destination point code version.
Configure the destination point code subsystem number.
Example Configuration
configure
sccp-network <id_number> variant <v_type>
self-pointcode <sp_code>
associate ss7-routing-domain <rd_id>
global-title-translation address-map <map_name>
destination dpc <dp_code> name <name>
destination dpc <dp_code> version <ver_type>
destination dpc <dp_code> ssn <ss_number>
end
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Configuring a MAP Service
Configuring a MAP Service
The Mobile Application Part (MAP) is an SS7 protocol which provides an application layer for the various
nodes in GSM and UMTS mobile core networks and GPRS core networks to communicate with each other
in order to provide services to mobile phone users. MAP is the application-layer protocol used to access the
Home Location Register (HLR), Visitor Location Register (VLR), Mobile Switching Center (MSC), Equipment
Identity Register (EIR), Authentication Center (AUC), Short Message Service Center (SMSC) and Serving
GPRS Support Node (SGSN).
The primary facilities provided by MAP are:
• Mobility Services: location management (when subscribers move within or between networks),
authentication, managing service subscription information, fault recovery.
• Operation and Maintenance: subscriber tracing, retrieving a subscriber's IMSI.
• Call Handling: routing, managing calls while roaming, checking that a subscriber is available to receive
calls.
• Supplementary Services.
• Short Message Service (SMS)
• Packet Data Protocol (PDP) services for GPRS: providing routing information for GPRS connections.
• Location Service Management Services: obtaining the location of subscribers.
Important
A maximum of 12 MAP services can be configured on the system.
To configure MAP services:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
In the context config mode, create a MAP service and give it a name.
In MAP Service configuration mode, configure the SCCP network that defines SS7 connectivity for SCCP applications.
Configure the parameters to contact the HLR.
In HLR configuration mode, specify the HLR pointcodes that should be associated with specific IMSI prefixes.
Configure the HLR pointcode to use as the default.
Step 7
Optional: Configure the SMS routing.
Optional: Enable the Short Message Service functionality.
Example Configuration
configure
context context_name
map-service map_name
access-protocol sccp-network sccp_network_id
equipment-identity-register point-code pnt_code
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hlr
imsi any point-code
default policy routing
exit
short-message-service
smsc-routing imsi-starts-with prefix point-code sms_pc
end
Configuring an IuPS Service (3G only)
A set of parameters, in the IuPS service configuration mode, define the communication path between the
SGSN service and the RNC. These configured parameters pertain to the RANAP layer of the protocol stack.
IuPS services must be configured in the same context as the SGSN service that will use them.
To configure an IuPS service:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
In context configuration mode for the SGSN service, create an IuPS service and give it a unique name.
In IuPS service configuration mode, specify the ID of the SCCP network to use for access protocol parameters.
Bind an address of an IP interface defined in the current context to use for GTPU connections to the RNC.
Specify an RNC to configure with a unique ID and the MCC and MNC associated with the RNC.
In RNC configuration mode, specify the RNCs point code.
Specify the LAC ID and RAC ID associated with the RNC.
Important
Appropriate interfaces (i.e., physical, loopback, secondary) must be defined prior to configuring the IuPS
service or the GTP-U IP address will decline to bind to the service.
Example Configuration
configure
context context_name
iups-service iups_name
access-protocol sccp-network sccp_network_id
gtpu bind address ip_address
rnc id rnc_id mcc mcc_num mnc mnc_num
pointcode rnc_pc
lac lac_id rac rac_id
end
Configuring an SGTP Service
This section provides instructions for configuring GPRS Tunneling Protocol (GTP) settings for the SGSN.
At a bare minimum, an address to use for GTP-C (Control signaling) and an address for GTP-U (User data)
must be configured.
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Example Configuration
To configure the SGTP service:
Step 1
Step 2
Step 3
Create an SGTP service and give it a unique name, in context configuration mode.
Specify the IP address of an interface in the current context to use for GTP-C.
Specify the IP address of an interface in the current context to use for GTP-U.
Important
Appropriate interfaces (i.e., physical, loopback, secondary) must be defined prior to configuring the SGTP
service or the GTP-U IP address will decline to bind to the service.
Example Configuration
configure
context name
sgtp-service name
gtpc bind address address
gtpu bind address address
end
Configuring a Gs Service
This section provides instructions for creating and configuring a Gs interface used by the SGSN to
communication with an MSC or VLR. The Gs interface is defined as a Gs service which handles the
configuration for the MSC/VLR.
The Gs interface parameters are configured within a Gs service in a context. Then the Gs service is referred
to in a GPRS service, an SGSN service, or an Call-Control Profile. The Gs service does not need to be in the
same context as the SGSN service, GPRS service, or a Call-Control Profile.
To configure the Gs service:
Step 1
Step 2
Step 3
Step 4
Step 5
In context configuration mode, create a Gs service and give it a unique name. Usually Gs service is defined in the same
context in which MAP service is defined because the MSC/VLR, HLR, EIR, and SMS-C are reachable via the STP or
SGW connected to the SGSN.
Specify the name of the SCCP network that identifies the SS7 access protocols.
Specify the target SS7 sub-system number (SSN), of the Base Station System Application Part (BSSAP), for
communication. Without this bit of configuration, the Gs service can not start.
Identify a location area code, in either a pooled or non-pooled configuration, relevant to the MSC/VLR. This step can
be repeated as needed.
Define the MSC/VLR by identifying its ISDN number, its SS7 point code, and the BSSAP SSN used to communicate
with it. Repeat this step to define multiple MSC/VLRs. (Note: SSN only needs to be defined if the routing defined is to
the MSC/VLR is PC+SSN.)
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Example Configuration
Example Configuration
configure
context name
gs-service name
associate-sccp-network id
bssap+ ssn ssn
non-pool-area id use-vlr vlr_id lac lac_id
vlr vlr_id isdn-number isdn_number bssap+ ssn ssn point-code vlr_pt_code
end
Configuring an SGSN Service (3G only)
All the parameters specific to the operation of an SGSN in a UMTS network are configured in an SGSN
service configuration. SGSN services use other service configurations like MAP (map-service) and IuPS
(iups-service) to communicate with other elements in the network.
To configure an SGSN service:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
Step 10
Step 11
In Context configuration mode, create an SGSN service and give it a unique name.
Specify the Core Network (CN) ID that will identify this SGSN service on the CN.
Specify the E.164 number to identify this SGSN service.
Configure the maximum number of PDP contexts that a UE can establish.
Specify the MAP service and the context in which it is configured that this SGSN service should use.
Specify the IuPS service name and the context in which it is configured for the SGSN service to use for RAN protocol
settings.
Important
If a direct tunnel is to be established, GTP-U direct tunneling must be enabled in both the IuPs service and
in the call-control-profile. For the IuPS service, the DT must be enabled per RNC; DT is enabled by default
on RNCs.
Specify the SGTP service and the context in which it is configured for this SGSN service to use for GTP configuration.
Specify the CDR types that the SGSN service should generate.
Specify the context in which GTPP accounting is configured. If the accounting context is not specified the current context
is assumed.
Configure the charging characteristics profile. (Number of buckets for the max change condition, volume limit, time
limit, and tariff time switch values should be defined individually according to requirements for each of the charging
characteristics profiles.
Optional: Specify the Gs service name and the context in which it is configured.
Important
Session Management (SM) and GPRS Mobility Management (GMM) settings can be configured as needed
using the SGSN configuration mode commands;sm <keyword> andgmm <keyword>. Refer to the SGSN
Service Configuration Mode chapter in the GPRS/UMTS Command Line Interface Reference.
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Example Configuration
Example Configuration
configure
context context_name
sgsn-service svc_name
core-network id cn_id
sgsn-number sgsn_number
max-pdp-contexts per-ms max_number
{ mobile-application-part-service | associate map-service } map_name context map_context
ran-protocol iups-service iups_svc_name context iups_context
{ sgtp-service | associate sgtp-service } svc_name context name
accounting cdr-types [ mcdr | scdr ]
accounting context acct_context
cc profile profile_number interval seconds
{ gs-service context | associate gs-service } ctxt service gs_service_name
end
Notes:
• For releases 12.2 and earlier, use mobile-application-part-service map_name context map_context
command. For releases 14.0 and later, use the associate map-service map_name context map_context
command.
• For releases 12.2 and earlier, use the sgtp-service svc_name context name command. For releases 14.0
and later, use associate sgtp-service svc_name context name command.
• For releases 12.2 and earlier, use the gs-service context ctxt service gs_service_name command. For
releases 14.0 and later, use the associate gs-service context ctxt service gs_service_name command.
Configuring a GPRS Service (2.5G only)
All the parameters specific to the operation of an SGSN in a GPRS network are configured in a GPRS service
configuration. GPRS services use other configurations like MAP and SGTP to communicate with other
elements in the network. The system can support multiple GPRS services.
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Example Configuration
To configure a GPRS service:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
In Context configuration mode, create a GPRS service instance and give it a unique name.
Specify the context in which the accounting parameters have been configured.
Create a PLMN definition for the GPRS service to include the identity of the mobile country code (MCC) and the mobile
network code (MNC).
Associate other services (such as a MAP or Gs or SGTP service) and their configurations with this GPRS service. This
command should be repeated to associate multiple service types and/or multiple instances.
Define the network service entity identifier (NSEI) of one or more remote SGSNs with their location area code (LAC)
and routing area code (RAC). This step can be repeated to associate multiple peer-NSEIs.
Specify the E.164 number to identify this SGSN.
Configure the charging characteristic(s).
Specify the types of CDRs to generate.
Example Configuration
configure
context context_name
gprs-service gprs_service_name
accounting ctxt
plmn id mcc mcc_num mnc mnc_num
{ service | associate service | }service_type service_name context service_ctxt
peer-nsei peer_nsei_id lac lac_id rac rac_id
sgsn-number sgsn_isdn_number
cc profile id buckets value
cc profile id interval value
accounting cdr-types cdr_type
end
Configuring a Network Service Entity
Configure a Network Service Entity for IP
Prior to implementing this configuration, the IP interfaces should have been defined in the same context as
the GPRS service.
Step 1
In Global configuration mode, create a network service entity (NSE) for IP. The resulting prompt will appear as:
[local]<hostname>(nse-ip-local)#
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Configure a Network Service Entity for Frame Relay
Step 2
In the Network Service Entity - IP local configuration mode, create up to four virtual links (NSVLs) for this entity - each
with a unique NSVL Id. The resulting prompt will appear as:
[local]<hostname>(nse-ip-local-nsvl-<id>)#
Step 3
Step 4
Configure the link access information: IP address, context name, and port number.
Configure the links signaling characteristics.
Example Configuration for a Network Service Entity for IP
config
network-service-entity ip-local -n
nsvl instance id
nsvl-address ip-address ip_addr context ctxt port num
signaling-weight num data-weight num
end
Configure a Network Service Entity for Frame Relay
Step 1
In Global configuration mode, create a network service entity (NSE) for Frame Relay. The resulting prompt will appear
as:
[local]<hostname>(nse-fr-peer-nsei-id)#
Step 2
In the Peer NSEI configuration mode, create a virtual connection instance for this entity. The resulting prompt will appear
as:
[local]<hostname>(nse-fr-peer-nsei-<id>-nsvci-<id>)#
Example Configuration for a Network Service Entity for IP
config
network-service-entity peer-nsei id frame-relay
ns-vc id id -n
end
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Configuring DNS Client
Configuring DNS Client
DNS client services can be configured for a context.
Step 1
Step 2
Step 3
Step 4
In context configuration mode, enable DNS lookup.
Specify the DNS to use for lookups; maximum of two DNS addresses can be used.
Create a DNS client with a unique name.
In DNS Client configuration mode, bind the DNS client to the IP address of an interface in the current context.
Example Configuration
configure
context context_name
ip domain-lookup
ip name-servers ip_address
dns-client name
bind address ip_address
end
Configuring GTPP Accounting Support
This section provides instructions for configuring GTPP-based accounting which allows the SGSN to send
M-CDR and/or S-CDR accounting data to the Charging Gateways (CGs) over the Ga interface.
The Ga interface and GTPP functionality are typically configured within a separate charging context.
The SGSN begins to generate M-CDR data upon GPRS/IMSI attach. S-CDR data generation begins upon
PDP context activation.
Accounting servers can be configured individually or as GTPP accounting server groups. GTPP accounting
server groups can each have completely different GTPP settings configured. Although a GTTP server can be
included in multiple GTPP groups.
Any GTPP accounting servers configured at the context level that are not specifically configured as part of a
GTPP group, are automatically assigned to be part of the GTPP server group called default that is part of
every context.
A maximum of 8 GTPP named server groups can be configured across all contexts. A maximum of 4 CGFs
can be configured in each GTPP server group. A total of total 32 CGFs can be configured across all server
groups, including the server group called default, in one context. Each GTPP group must have unique GTPP
charging agents (CGFs) configured.
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Creating GTPP Group
Important
The system supports the specification of the UDP port number for the charging agent function on the
system and for the CG. The default charging agent port is 49999. The default CG Server port is (3386).
If an SGSN service and a GGSN service are both configured on this system be sure that the UDP ports
are unique for each type of service. Refer to the Command Line Interface Reference for information on
changing the ports used.
To configure the GTPP accounting support for a SGSN service:
Step 1
Step 2
Step 3
Step 4
Create the GTPP group in accounting context by applying the example configuration in the Creating GTPP Group
section.
Configure the charging agent and GTPP server (CGF) related parameters for the GTPP accounting support by applying
the example configuration in the Configuring GTPP Group section.
Verify your GTPP group and accounting configuration by following the steps in the Verifying GTPP Group Configuration
section.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide and the Command Line Interface Reference.
Creating GTPP Group
Use the following example to create the GTPP group to support GTPP accounting:
configure
context <vpn_ctxt_name>
gtpp group <gtpp_group_name>
end
Notes:
-noconfirm
• In addition to one default GTPP group "default" a maximum of 8 GTPP groups can be configured with
this command in a context.
• In case no GTPP group is configured in this context, system creates a default GTPP group named "default"
and all the CGF servers and their parameters configured in this context are applicable to this "default"
GTPP group.
Configuring GTPP Group
Use the following example to configure the GTPP server parameters, GTPP dictionary, and optionally CGF
to support GTPP accounting:
configure
context <vpn_ctxt_name>
gtpp group <gtpp_group_name>
gtpp charging-agent address <ip_address> [ port <port> ]
gtpp server <ip_address> [ max <msgs >] [ priority <priority>]
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Verifying GTPP Group Configuration
gtpp dictionary <dictionaries>
gtpp max-cdrs <number_cdrs> [ wait-time <dur_sec>
gtpp transport-layer { tcp | udp }
end
Notes:
]
• In addition to one default GTPP group "default" a maximum of 8 GTPP groups can be configured with
this command in a context.
• In case no GTPP group is configured in this context, system creates a default GTPP group named "default"
and all the CGF servers and their parameters configured in this context are applicable to this "default"
GTPP group.
• Command for CGF gtpp charging-agent is optional and configuring gtpp charging-agent on port 3386
may interfere with ggsn-service configured with the same ip address. Multiple interfaces can be configured
within a single context if needed.
• For more information on GTPP dictionary encoding, if you are using StarOS 12.3 or an earlier release,
refer to the AAA and GTPP Interface Administration and Reference. If you are using StarOS 14.0 or a
later release, refer to the GTPP Interface Administration and Reference.
• For better performance, it is recommended to configure maximum number of CDRs as 255 with gtpp
max-cdrs command.
• You can select transport layer protocol as TCP or UDP for Ga interface with gtpp transport-layer
command. By default it is UDP.
• Multiple GTPP server can be configured using multiple instances of this command subject to following
limits:
◦Total 4 GTPP server in one GTPP group
◦Total 32 GTPP server in one context
◦Total 9 GTPP groups (1 default and 8 user defined GTPP groups) can be configured in one context.
Number of CGFs in 1 GTPP group is limited to 4 and a total of 32 CGF servers across all GTPP
groups in one context are configurable.
Verifying GTPP Group Configuration
Verify that your CGFs were configured properly by entering the following command in Exec Mode:
show gtpp accounting servers
This command produces an output similar to that displayed below:
context: source
Preference
IP
Group
-----------------------Primary
192.168.32.135
default
Primary
192.168.89.9
default
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Port
---3386
--------
3386
Priority
State
------1
Active
------
100
Active
SGSN Service Configuration Procedures
Configuring and Associating the EGTP Service (S4 Only)
Configuring and Associating the EGTP Service (S4 Only)
This section describes how to configure and associate the EGTP service to support S4-SGSN functionality.
The SGSN communicates with the EPC network SGW via the GTPv2 protocol over the S4 interface. GTPv2
is configured on the chassis as part of an EGTP service. Once configured, the EGTP service then must be
associated with the configured UMTS (3G) and/or GPRS (2G) service configured on the system to provide
access to the EPC network.
Once the EGTP service is associated with the UTRAN and/or GERAN service, then the S4-SGSN will be
chosen for PDP context activation in the following cases:
• If the last known capability of the UE indicates that it is EPC-capable.
• If the last known capability of the UE indicates it is non-EPC capable but has an EPS subscription only.
• If a PDP context is already activated for the UE, and the S4 interface is already selected for the UE.
Important
The S4 feature license must be enabled on the S4-SGSN to configure the EGTP service.
Important
S4 support for the SGSN requires the presence of an SGTP service, even though S4 support is being
configured for the SGSN to use the S4 interface. The SGTP service is required to interface with non-EPC
capable roaming partners via the Gn interface. SGTP is also required for subscribers using mobile phones
that are not EPC-capable in an EPC network.
Important
Currently, the S4-SGSN does not support the transfer of PDP contexts from the S4 interface to the Gn
interface within the same S4-SGSN.
Use the following procedure to configure and associate the EGTP service to for S4 functionality on the SGSN:
Step 1
Step 2
Step 3
Step 4
Access Context Configuration Mode.
Create and configure the EGTP service in the desired context.
Configure the interface type for the EGTP service.
Configure the validation mode for the EGTP service. The default and recommened setting is standard.
Step 5
Step 6
Associate the EGTP service with the configured 2.5G service (if configured).
Associate the EGTP service with the configured 3G service (if configured).
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Example Configuration
Example Configuration
config
context context_name
egtp-service service_name
gtpc bind ipv4-address ipv4_address
interface-type interface-sgsn
validation-mode standard
end
config
context context_name
gprs-service gprs_service_name
associate egtp-service egtp_service_name context context_name
end
config
context context_name
sgsn-service sgsn_service_name
associate egtp-service egtp_service_name context context_name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring and Associating the GTPU Service (S4 Only)
This section describes how to configure and associate the GTPU service on the S4-SGSN.
The GTPU service is required to support the EGTP service for the sending and receiving of GTP bearer packets
to and from the EPC SGW.
Use the following procedure to configure and associate the GTPU service:
Step 1
Step 2
Access Context Configuration Mode.
Create the GTPU service in the same context where the egtp-service is configured.
Step 3
Step 4
Bind the GTPU service to the IP address to be used for GTP-U (the S4-SGSN side IP address for GTP-U packets).
Associate the GTPU service with the configured egtp-service.
Example Configuration
config
context context_name
gtpu-service service_name
bind ipv4-address ipv4_address
end
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Configuring the DNS Client Context for APN and SGW Resolution (Optional)
config
context egtp-service_context_name
egtp-service egtp-service_name
associate gtpu-service egtp_service_name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the DNS Client Context for APN and SGW Resolution
(Optional)
This section describes how to configure the context from which DNS client has to be selected for performing
an APN FQDN query for resolving a PGW address (S4-SGSN) or a co-located PGW / GGSN address (Gn
SGSN), and the context from which DNS client has to be selected for performing an RAI FQDN query for
resolving an SGW address (S4-SGSN).
By default, the S4-SGSN supports the initiation of a DNS query after APN selection using a S-NAPTR query
for EPC-capable subscribers. The S4-SGSN resolves a PGW/GGSN by sending an APN-FQDN query to the
DNS client. Similarly, the S4-SGSN resolves the SGW by sending a RAI-FQDN query to the DNS client.
The DNS Client then sends a query to the DNS server to retrieve NAPTR/SRV/A records and return the SGW
or PGW IP address to the SGSN.
Important
For non-EPC capable subsribers, the S4-SGSN initiates only a DNS A query.
The Gn SGSN supports selecting a co-located PGW/GGSN node for EPC capable UEs by performing a DNS
SNAPTR lookup for APN FQDN for the service parameter"x-3gpp-pgw:x-gn" / "x-3gpp-pgw:x-gp". Note
that in addition to these parameters, the service parameters In addition to these interfaces "x-3gpp-ggsn:x-gn"
& "x-3gpp-ggsn:x-gp" are used for selecting standalone GGSNs.
For performing a DNS SNAPTR query, the SGSN requires an additional, optional, configuration that identifies
the context where DNS lookup for EPC-capable UEs must occur. This is accomplished by creating a
call-control-profile that specifies the context from which the DNS client should be used for resolving a
co-located PGW/GGSN address on a Gn SGSN as well.
Use the following procedure to configure and associate the configure DNS for APN resolution to support S4
functionality:
Step 1
Step 2
Step 3
Access Call Control Profile Configuration Mode and create a call control profile.
Configure the DNS client context to resolve PGW UEs via the context the DNS client is configured.
Configure the DNS client context to resolve SGW UEs via the context where the DNS client is configured.
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Example Configuration
Example Configuration
config
call-control-profile name
dns-pgw context dns_client_context_name
dns-sgw context dns_client_context_name
end
Notes:
• dns-pgw context is valid for selecting a PGW (in an S4-SGSN) as well as a co-located PGW/GGSN
(in a Gn/GP- SGSN). If the interface selected for a UE is S4 and if there is no dns-pgw context configured
under the Call Control Profile, then by default it will look for the DNS client in the context where the
EGTP service is defined. If the interface selected for a UE is Gn/Gp, and if there is no dns-pgw context
configured under the Call Control Profile, then by default the system will look for the DNS client in the
context where the SGTP service is configured for selecting co-located PGW/GGSNs if:
◦The UE is EPC capable and,
◦apn-resolve-dns-query snaptr is configured under an APN Profile.
• dns-sgw context specifies the name of the context where the DNS client is configured and that will be
used for DNS resolution of SGWs. If dns-sgw is not configured, the S4-SGSN uses the DNS client
configured in the context where EGTP service is configured to query the SGW DNS address.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the S6d Diameter Interface (S4 Only)
This section describes how to configure the S6d Diameter interface to support S4 functionality.
The S6d interface is a Diameter-based interface used to support S4 functionality by enabling the S4-SGSN
to communicate with the HSS. The HSS is a master user database that contains all subscription related
information, and performs the following functions:
• Authentication and authorization of the user
• Provides the subscribers location information
• Provides the subscribers IP information
To support the S6d interface, an HSS Peer Service must be configured and associated with a Diameter endpoint.
This HSS Peer Service is then associated with the configured SGSN and/or GPRS services to enable
communication with the HSS via the S6d interface. Optionally, operators can configure an operator policy-based
interface selection.
Configuring the S6d interface consists of the following procedures:
1 Configuring a Diameter Endpoint for the S6d interface
2 Configuring the HSS Peer Service and Interface Association for the S6d interface
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Configuring the Diameter Endpoint for the S6d Interface
3 Associating the HSS Peer Service with the SGSN and GPRS Services for the S6d interface.
4 Optional. Configuring operator policy-based interface selection for the S6d interface.
Configuring the Diameter Endpoint for the S6d Interface
Use the following procedure to configure the Diameter endpoint for the S6d interface:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Configure a port that will be bound to an interface (at step 3) to be used as the S6d interface.
Configure an Ethernet interface to be used as a diameter endpoint.
Configure a Diameter endpoint to be used as the S6d interface.
Specify the origin host address and the IP address of the Ethernet interface to be used as the S6d interface.
Specify the origin realm. The realm is the Diameter identity. The originator's realm is present in all Diameter messages
and is typically the company or service provider's name.
Specify the peer name, peer realm name, peer IP address and port number. The peer IP address and port number are the
IP address and port number of the HSS.
Specify the route entry peer. This parameter is optional. The route entry peer parameter is required if multiple HSS peers
are configured under a Diameter point and operators want to associate a routing weight to each HSS peer so that the
S4-SGSN contacts each HSS based on the weight distribution.
Optional. Enable or disable the watchdog-timeout parameter.
Step 7
Step 8
Step 9
The use-proxy keyword can be specified in the diameter-endpoint command to enable the proxy mode. The usage of
proxy mode depends on the operator's HSS capabilities.
Example Configuration
config
port ethernet slot number/port number
no shutdown
bind interface s6d_interface_name context_name
end
config
context context_name
interface s6d_interface_name
ip address s6d_interface_ip_address subnet_mask
exit
diameter endpoint endpoint_name
origin host host_name address s6d_interface_ip_address
origin realm realm_name
peer peer_name realm realm_name address hss_ip_address
route-entry peer route_entry_name
use-proxy
no watchdog-timeout
end
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Configuring the HSS Peer Service and Interface Association for the S6d Interface
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the HSS Peer Service and Interface Association for the S6d
Interface
Use the following procedure to configure the HSS Peer Service and interface association for the S6d interface:
Step 1
Step 2
Step 3
Configure a Diameter endpoint. If not already configured, refer to the Configuring the Diameter Endpoint for the S6d
Interface, on page 139 Then specify the IP address of the Ethernet interface configured in Step 1 as the Diameter endpoint
address.
Associate the Diameter endpoint with an HSS peer service.
Specify the Diameter dictionary to be used for the HSS Peer Service. The standard-r9 dictionary must be used for the
S6d interface.
Example Configuration
config
context sgsn_context_name
hss-peer-service hss_peer_service_name
diameter hss-endpoint hss_endpoint_name
diameter hss-dictionary standard_r9
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
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Associating the HSS Peer Service with the SGSN and GPRS Services for the S6d Interface
Associating the HSS Peer Service with the SGSN and GPRS Services for the
S6d Interface
Use this procedure to association the HSS Peer Service with the SGSN and GPRS Services:
Step 1
Step 2
Step 3
Access Context Configuration Mode and create an SGSN service.
Associate the HSS peer service name with the SGSN service.
Step 4
Access Context Configuration Mode and create a GPRS service.
Associate the HSS peer service name with the GPRS service.
Example Configuration
config
context context name
sgsn-service sgsn-service-name
associate hss-peer-service hss-peer-service-name
end
config
context context name
gprs-service gprs-service-name
associate hss-peer-service hss-peer-service-name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring Operator Policy-Based S6d Interface Selection (Optional)
It is mandatory for the SGSN and GPRS services to have either a MAP service association or an
HSS-Peer-Service association.
• If no MAP service is associated with the SGSN or GPRS services, and only the HSS service is associated
with the SGSN or GPRS services, then the S6d interface is selected.
• If both the MAP service and the HSS-Peer-Service are associated with the SGSN or GPRS service, by
default the Gr interface is selected. To override the default use of the Gr interface, configure the operator
policy to select the s6d-interface.
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Configuring the Subscription Interface Preference for the S6d Interface (Optional)
• Once the interface selection is configured, the call-control-profile is first checked to determine whether
to select the MAP-interface or HSS-interface. If neither the MAP nor HSS is configured under the call
control profile, then the system checks the configured SGSN or GPRS-services.
Step 1
Access Call Control Profile Configuration Mode and create a call-control-profile.
Associate the configured HSS peer service with the S6d interface. The s6d-interface option must be selected.
Step 2
Example Configuration
config
call-control-profile name
associate hss-peer-service name s6d-interface
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the Subscription Interface Preference for the S6d Interface
(Optional)
The S4-SGSN provides a mechanism to associate a MAP service with call-control-profile. In some situations,
it is possible that both the MAP service and the HSS peer service are associated with the Call Control Profile.
In these cases, operators can configure the preferred subscription interface.
Step 1
Step 2
Access Call Control Profile Configuration Mode and create a call-control-profile.
Specify the preference of the subscription-interface. Selecting the hlr option will cause the MAP protocol to be used to
exchange messages with the HLR. The hss option causes the Diameter-protocol to be used to exchange messages with
the HSS.
Example Configuration
config
call-control-profile name
prefer subscription-interface { hlr | hss }
end
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Configuring the S13' Interface (S4 Only, Optional)
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the S13' Interface (S4 Only, Optional)
The S13' (S13 prime) interface is a Diameter-based interface that is used to perform the Mobile Equipment
(ME) identity check procedure between the SGSN and EIR. Configuring the S13' interface is optional.
The SGSN performs ME identity check to verify the Mobile Equipment's identity status.
The S13'interface uses the Diameter protocol. An HSS Peer Service must be configured and associated with
a Diameter endpoint. It is not mandatory to configure the HSS Peer Service under the SGSN or the GPRS
service. By configuring the HSS Peer Service in Call Control Profile Configuration Mode, the S13'interface
can be used.
In the absence of an operator policy, the HSS Peer Service must be associated with the configured SGSN or
GPRS service to be able to utilize the S13'interface. In the presence of an operator policy, the operator policy
configured overrides the service configured in the SGSN or GPRS service.
Important
The S13' interface can only be configured after the S6d interface has been configured. Refer to Configuring
the S6d Diameter Interface (S4 Only), on page 138 procedure for information on configuring the S6d
interface.
Configuring the S13' interface consists of the following procedures;
Step 1
Step 2
Step 3
Step 4
Configure a Diameter Endpoint for the S13' interface.
Configure the HSS Peer Service and Interface association for the S13' interface.
Associate the HSS Peer Service with the SGSN and GPRS services for the S13' interface.
Optional. Configure an operator policy S13-based interface selection call control profile for the S13' interface.
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Configuring a Diameter Endpoint for the S13' Interface
Configuring a Diameter Endpoint for the S13' Interface
Use this procedure to configure a Diameter endpoint for the S13' interface:
Step 1
Access Context Configuration Mode and create a Diameter endpoint.
Specify the origin host address and the IP address of the S13'interface.
Specify the origin realm. The realm is the Diameter identity. The originator's realm is present in all Diameter messages
and is typically the company or service name.
Specify the peer name, peer realm name, peer IP address and port number. The peer IP address and port number are the
IP address and port number of the HSS.
Specify the route entry peer (optional). The route entry peer parameter is required if multiple HSS or EIR peers are
configured under a Diameter point and operators wish to associate a routing weight to each HSS or EIR peer so that
SGSN contacts each HSS or EIR based on the weight distribution.
The user can optionally enable or disable the parameter watchdog-timeout.
The use-proxy keyword can be specified in the diameter-endpoint command to enable the proxy mode. The usage of
proxy mode depends on the operator's EIR capabilities.
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Example Configuration
config
port ethernet s13'_interface_name
no shutdown
bind interface s13'_interface_name sgsn_context_name
end
config
context context_name
interface s13'_interface_ip subnet_mask
exit
diameter endpoint s13'_endpoint_name
origin host host_name address host_address
origin realm realm_address
peer peer_name realm realm_name address hss_ip_address
route-entry peer route_entry_name
use-proxy
no watchdog-timeout
exit
hss-peer-service hss_peer_service_name
diameter hss-endpoint s6d_endpoint_name eir-endpoint s13'_endpoint_name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
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Configuring the HSS Peer Service and Interface Association for the S13' Interface
Configuring the HSS Peer Service and Interface Association for the S13'
Interface
Use the following procedure to configure the HSS Peer Service and Interface association:
Step 1
Step 2
Step 3
Step 4
Configure an Ethernet interface to be used as a Diameter endpoint.
Configure a Diameter endpoint and specify the IP address of the Ethernet interface configured in Step 1 as the Diameter
endpoint address.
Configure an HSS peer service and associate it with the Diameter endpoint configured for the S6d and S13' interfaces.
Specify the Diameter dictionary to be used for the HSS-Peer-Service. The standard-r9 option must be selected for the
SGSN.
Example Configuration
config
port ethernet slot_number/port_number
no shutdown
bind interface s6d_interface_name sgsn_context_name
end
config
context sgsn_context_name
interface s6d_interface_name
ip address s6d_interface_ip_address subnetmask
exit
diameter endpoint s6d-endpoint_name
origin realm realm_name
origin host name address s6d_interface_address
peer peer_name realm realm_name address hss_ip_address
exit
diameter endpoint s13'_endpoint_name
origin realm realm_name
origin host name address s13'_interface_address
peer peer_name realm realm_name address eir_ip_address
exit
hss-peer-service hss_peer_service_name
diameter hss-endpoint hss_endpoint_name eir-endpoint eir_endpoint_name
diameter hss-dictionary standard-r9
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
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Associating the HSS Peer Service with the SGSN and GPRS Services for the S13' Interface
Associating the HSS Peer Service with the SGSN and GPRS Services for the
S13' Interface
Use this procedure to associate the HSS Peer Service with the SGSN and GPRS services.
Step 1
Step 2
In Context Configuration Mode create a SGSN service.
Associate the HSS peer service with SGSN service, if configured, and provide the HSS peer service name and context
name.
Associate the HSS peer service with GPRS service, if configured, and provide the HSS peer service name and context
name.
Step 3
Example Configuration
config
context context_name
sgsn-service sgsn_service_name
associate hss-peer-service hss-peer-service-name
end
config
context context_name
gprs-service gprs_service_name
associate hss-peer-service hss-peer-service-name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring S13' Interface Selection Based on an Operator Policy
It is mandatory for the SGSN and GPRS service to have either a MAP service association or an HSS Peer
Service association.
• In the absence of a MAP service association with SGSN or GPRS service, and if the HSS service is
associated with the SGSN or GPRS service then the S13' interface is selected.
• If both the MAP service and the HSS-Peer-Service are associated with the SGSN or GPRS service, by
default the Gf interface is selected. To override this default, operators can configure an operator policy
to configure behavior for the S13' interface selection.
• Once configured, the behavior is as follows:
◦First, the call control profile is checked to determine on whether a MAP or HSS interface is
configured.
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Configuring QoS Mapping for EPC-Capable UEs using the S4 Interface (S4 Only, Optional)
◦If neither A MAP or HSS is configured under the call control profile, then the system uses the
configuration in the SGSN or GPRS service.
Use this procedure to configure an operator policy used for S13' interface selection.
Step 1
Access Call Control Configuration Mode and configure a call-control-profile.
Associate the HSS Peer Service with the s13-prime-interface.
Step 2
Example Configuration
config
call-control-profile name
associate hss-peer-service name s13-prime-interface
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring QoS Mapping for EPC-Capable UEs using the S4
Interface (S4 Only, Optional)
An S4-SGSN communicates QoS parameters towards the SGW and PGW in EPC QoS. However, it sends
QoS towards the UE in the QoS format defined in the GMM/SM specification (TS 24.008). 3GPP defines a
mapping for EPS QoS to pre-release 8 QoS in TS 23.401, Annex E. On the S4-SGSN, operators can configure
the quality of service (QoS) parameters as Call Control Profiles that will ensure proper QoS mapping between
the S4-SGSN and the EPC gateways (PGW and SGW) and UEs. However, such configurations are optional.
If no mapping is configured, then the S4-SGSN uses the default mapping.
The configured Call Control Profiles also will be used if the S4 interface is chosen for PDP activation, but
the subscription does not have an EPS subscription. Therefore, GPRS subscription data (which uses QoS in
pre-release 8 format), will be mapped to EPS QoS behavior. The allocation and retention policy will be mapped
to EPS ARP using the configured Call Control Profiles. Specifically, the configuration provided in this section
enables the S4-SGSN to:
• Map EPC ARP (allocation and retention priority) parameters to pre-release 8 ARP (Gn/Gp ARP)
parameters during S4-SGSN to Gn SGSN call handovers.
• Map ARP parameters received in a GPRS subscription from the HLR to EPC ARP parameters if the S4
interface is selected for an EPC capable UE that has only a GPRS subscription (but no EPS subscription)
in the HLR / HSS.
If the QoS mapping configuration is not used, the following default mappings are used:
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Example Configuration
• Default ARP high-priority value = 5
• Default ARP medium-priority value = 10
• Default pre-emption capability = shall-not-trigger-pre-emption
• Default pre-emption vulnerability = pre-emptable
Use this procedure to configure QoS mapping for EPC Gateways and UEs:
Step 1
Step 2
Step 3
Step 4
Step 5
Access Call Control Profile Configuration Mode and create a call-control-profile.
Configure the QoS ARP settings.
Exit back to the Local prompt.
Access the call-control profile you just configured.
Configure the QoS pre-emption or vulnerability capabilities.
Example Configuration
config
call-control-profile cc_profile_name
qos gn-gp arp high-priority hi_prior_value medium-priority med_prior_value
end
config
call-control-profile cc-profile-name
qos gn-gp pre-emption { capability { may-trigger-pre-emption | shall-not-trigger-pre-emption
} | vulnerability { not-pre-emptable | pre-emptable } }
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the Peer SGSN Interface Type (S4 Only, Optional)
Operators can specify the type of interface the S4-SGSN will use to communicate with the peer SGSN in a
call control profile.
Use the following procedure to configure the peer SGSN interface type:
Step 1
Step 2
Access the Call Control Profile configuration for the peer SGSN.
Configure the interface type to be used for communication between the S4-SGSN and the peer SGSN. s16 must be
specified if the peer SGSN is an S4-SGSN.
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Example Configuration
Example Configuration
config
call-control-profile cc_profile_name
sgsn-address { rac rac value lac lac value | rnc_id rnc_id } prefer { local | fallback-for-dns }
address ipv4 ipv4 address interface { gn | s16 }
end
Notes:
• The rnc_id parameter can be used instead of the rac and lac values if operators wish to configure the
target RNC ID that maps to the address of the peer SGSN via the S16 interface. The RNC ID is used by
the S4-SGSN for inter-SGSN SRNS relocation. Configuration of the rnc_id is optional, and valid only
if SRNS relocation first has been configured in Call Control Profile Configuration Mode using the
srns-inter and/or srns-intra commands.
• The fallback-for-dns option is under development for future use, and is not currently supported on the
S4-SGSN.
• NRI-based validation is not supported on the S4-SGSN.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring Gn Interface Selection Based on an Operator Policy
(S4 Only, Optional)
The S4-SGSN uses the S4 interface to communicate with EPC-capable UEs. However, operators have the to
option to create a call-control-profile that enables the S4-SGSN to forcefully select the Gn interface for
EPC-capable UEs.
Use this procedure to forcefully select the Gn interface for EPC-capable UEs:
Step 1
Step 2
Step 3
Access Call Control Profile Configuration Mode.
Create a call-control-profile.
Configure the SGSN to forcefully select the Gn interface.
Example Configuration
config
call-control-profile cc_profile_name
sgsn-core-nw-interface { gn | s4 }
end
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Configuring a Custom MME Group ID (S4 Only, Optional)
Notes:
• sgsn-core-nw-interface specifies the interface that EPC-capable UEs will use to communicate with the
packet core gateways (GGSN/SGW). The default setting for EPC-capable UEs is s4.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring a Custom MME Group ID (S4 Only, Optional)
3GPP specifications define how a GUTI allocated by an MME is translated into an old P-TMSI and old RAI
when a UE hands over to an SGSN. 3GPP specifications state that when a GUTI is mapped to an old RAI,
the MME group ID portion of the GUTI will be mapped to a Location Area Code (LAC). MME group IDs
are 16-bit numbers which always have their most significant bit set. As a result, their range is 32768 - 65535.
However, some operators may have already configured their networks with LACs for UTRAN and GERAN
coverage in the 32768 - 65535 range. To provide backward compatibility for such deployments, a custom list
of MME group IDs must be configured for use by both the S4-SGSN and MME products for UTRAN/GERAN
and E-UTRAN handovers.
Once the custom MME Group IDs have been configured, operators then can configure the S4-SGSN to use
the available custom MME Group IDs configured for both GPRS (2G) and UTRAN (3G) network services.
Use the following procedure to configure the SGSN to use the custom MME Group IDs:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Access LTE Network Global MME ID Management Database Configuration Mode.
Specify the PLMN MCC and MNC values.
Configure the low and high end values of the LAC range to be used.
Access the context in which the SGSN (3G) service is configured.
Associate the 3G service (if configured), with the MME's Network Global MME ID Management Database that contains
the custom list of MME Group IDs.
Access the context in which the 2G GPRS service is configured.
Associate the 2G service, if configured, with the MME's Network Global MME ID Management Database that contains
the custom list of MME Group IDs.
Example Configuration
config
lte-policy
network-global-mme-id-mgmt-db
plmn mcc mcc_value mnc mnc_value mme-group-id-range first low_end_of_range last
high_end_of_range
exit
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Configuring and Associating the Selection of an SGW for RAI (S4 Only, Optional)
exit
context context_name
sgsn-service sgsn_service_name
associate network-global-mme-id-mgmt-db
end
config
context context_name
gprs-service gprs_service_name
associate network-global-mme-id-mgmt-db
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring and Associating the Selection of an SGW for RAI
(S4 Only, Optional)
If operators wish to bypass DNS resolution of RAI FQDN for obtaining the S-GW address, the SGSN can
select an S-GW by performing a local configuration look-up for the current Routing Area Instance (RAI).
This is accomplished by configuring the TAI Management Database (tai-mgmt-db) of the SGSN to select an
S-GW address and its associated RAI. In addition, the TAI Management Database must be associated with
the 2G and/or 3G services configured on the SGSN. The TAI Management Database can also be associated
with a call-control-profile for RAI-to-SGW address mapping.
Use the following procedure to configure the selection of an SGW for RAI:
Step 1
Access Global Configuration Mode.
Step 2
Access LTE Policy Configuration Mode.
Step 3
Create a TAI Management Database and enter TAI Management Database Configuration Mode.
Step 4
Create a TAI Management Object and enter TAI Management Object Configuration Mode.
Configure the RAI. Specify the RAI MCC, MNC, LAC and RAC values.
Configure the SGW address serving the RAI. Specify the IPv4 address, the S5-to-S8 protocol as GTP, and the load
balancing Weight for this SGW. On the S4-SGSN, only GTP is supported as the protocol option.
Step 5
Step 6
Step 7
Access SGSN Service Configuration Mode and associate the configured UTRAN (3G) service with the S-GW addresses
and their associated RAIs.
Step 8
Access GPRS Service Configuration Mode and associate the configured GERAN (2G) and service with the S-GW
addresses and their associated RAIs.
Step 9
Optional. Associate the SGW address-to-RAI mapping with a call-control-profile.
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Example Configuration
Example Configuration
config
lte-policy
tai-mgmt-db tai_mgmt_db_name
tai-mgmt-ojb obj_name
rai mcc mcc_value mnc mnc_value lac lac_value rac rac_value
sgw-address ipv4_addr | ipv6_addr s5-s8-protocol gtp weight number
end
config
context context_name
sgsn-service sgsn_service_name
associate tai-mgmt-db tai_mgmt_db_name
end
config
context context_name
gprs-service gprs_service_name
associate tai-mgmt-db tai_mgmt_db_name
end
config
call-control-profile cc_profile_name
associate tai-mgmt-db tai_mgmt_db_name
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring a Local PGW Address (S4 Only, Optional)
If operators wish to bypass DNS resolution of APN FQDN on the S4-SGSN for obtaining a PGW address,
the S4-SGSN can be configured to use a locally configured PGW IPv4 address in an APN profile.
Use the following procedure to configure the local PGW address:
Step 1
Step 2
Access APN Profile Configuration Mode and create an APN profile.
Specify the address resolution mode for the PGW as local.
Step 3
Step 4
Configure the P-GW address.
Configure the load balancing weight preference for the P-GW.
Example Configuration
config
apn-profile apn_profile_name
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Configuring the Peer MME Address (S4 Only, Optional)
address-resolution-mode local
pgw-address ipv4_address | ipv6_address weight weight_preference
end
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring the Peer MME Address (S4 Only, Optional)
For operators wishing to bypass DNS resolution to obtain the peer EPC MME address, the SGSN supports
the local configuration of a peer MME address for a given MME group (LAC) and MME code (RAC).
Use the following procedure to configure the peer MME address:
Step 1
Step 2
Step 3
Access Call Control Configuration Mode and create a call-control-profile.
Configure the peer MME Group ID LAC and RAC values or the TAC.
Specify a local preference for selection of the peer MME address.
Step 4
Step 5
Specify the local MME address to use for lookup instead of a DNS query.
Specify the interface type to use when communicating with the peer MME. The interface must be s3.
Example Configuration
config
call-control-profile cc-profile-name
peer-mme { mme-groupid lac_value mme-code rac_code | tac tac } prefer local address
ipv4_address | ipv6_address interface { gn [ s3 ] | s3 [ gn ] }
end
Notes:
• The tac keyword can be used instead of the mme-groupid and mme-code parameters to configure the
Tracking Area Code (TAC) of the target eNodeB that maps to the peer MME address. The TAC is used
by the S4-SGSN for UTRAN to E-UTRAN (SGSN to MME) SRNS relocation across the S3 interface.
Configuration of the tac is valid only if SRNS relocation first has been configured in Call Control Profile
Configuration Mode via the srns-inter and/or srns-intra commands.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
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Configuring the ISR Feature (S4 Only, Optional)
Configuring the ISR Feature (S4 Only, Optional)
Idle Mode Signaling Reduction (ISR) is a license-enabled feature that allows the UE to roam between LTE
and 2G/3G networks while reducing the frequency of TAU and RAU procedures due to the UE selecting
E-UTRAN or UTRAN networks. ISR reduces the signaling between the UE and the network, and also reduces
the signaling between the E-UTRAN and UTRAN networks.
Use the following procedure to configure the ISR feature:
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Access Call Control Configuration Mode.
Create a call-control-profile.
Enable the Idle Mode Signaling Reduction feature for 3G (UMTS) network access
Set the T3323 timeout value that the configured SGSN service will send to the UE in Attach Accept and RAU Accept
messages.
Enable the ISR feature for 2G network access
Configure the implicit detach timer for 2G subscribers.
Example Configuration
config
call-control-profile cc-profile-name
idle-mode-signaling-reduction access-type umts
end
config
context context_name
sgsn-service sgsn_service_name
gmm T3323-timeout dur_mins
end
config
call-control-profile name
idle-mode-signaling-reduction access-type gprs
end
config
context plmn_name
gprs-service gprs_service_name
gmm implicit-detach-timeout secs
end
Notes:
• idle-mode-signaling-reduction access-type umts enables ISR for 3G network access.
• gmm T3323-timeout dur_mins is the amount of time, in minutes, the UE should wait after the Periodic
RAU timer (T3312 timer) expiry before deactivating ISR for the 3G subscriber. Valid entries are from
1 to 186. The default is 54.
• idle-mode-signaling-reduction access-type umts enables ISR for 2G network access.
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Configuring IDFT for Connected Mode Handover (S4 Only, Optional)
• gmm implicit-detach-timeout secs specifies the implicit detach timeout value to use for 2G ISR. Valid
entries are from 240 to 86400 seconds. The default value is 3600 seconds.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring IDFT for Connected Mode Handover (S4 Only,
Optional)
The S4-SGSN supports the setup of indirect data forwarding tunnels (IDFT) between the eNodeB and the
RNC via the SGW during connected mode handovers. This allows the S4-SGSN to support connected mode
handovers between the UTRAN and E-UTRAN networks across the S3 interface.
Once enabled, IDFT is employed under the following conditions:
• If the SGSN is the old node participating in the connected mode handover:
◦The target node to which the connected mode handover is initiated should be an eNodeB (i.e., the
SGSN performs the handover to the MME.
◦The enb-direct-data-forward CLI setting is not configured in the target RNC configuration (in
RNC Configuration Mode).
• If the SGSN is the new node participating in the connected mode handover:
◦The source node from which connected mode handover is initiated is an eNodeB (i.e., the MME
is performing a handover to the SGSN).
◦The enb-direct-data-forward CLI setting is not configured in the target RNC configuration (in
RNC Configuration Mode).
◦The source MME indicated that it does not support direct forwarding via a Forward Relocation
Request.
Important
If the target SGSN did not relocate to a new SGW, then IDFT does not apply. The target SGSN sets up
an indirect data forwarding tunnel with the SGW only if the SGW is relocated. If the SGW is not relocated,
then the source MME sets up the indirect data forwarding tunnel between the source eNodeB and the
target RNC through the SGW.
Important
By default, indirect data forwarding is enabled, and direct forwarding is disabled.
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Example Configuration
To configure IDFT for connected mode inter RAT handovers:
Step 1
Step 2
Step 3
Step 4
Enter the context where the IuPS service is configured.
Enter IuPS Service Configuration Mode and enter the configured IuPS service.
Enter the RNC ID of the IuPS service for which you want to enable IDFT.
Disable direct data forwarding for connected mode inter RAT handovers.
Example Configuration
config
context context_name
iups-service iups_service_name
rnc id rnc_id
no enb-direct-data-forward
end
Where:
• no enb-direct-data-forward enables the setup of IDFT between the eNodeB and the RNC via the SGW
for connected mode inter RAT handovers. If IDFT is enabled, the SGSN/MME will send the IDFT
request towards the SGW. Once enabled, the SGSN/MME will send IDFT requests towards the SGW.
• To disable IDFT, enter the enb-direct-data-forward command.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Creating and Configuring ATM Interfaces and Ports (3G only)
ATM ports and their associated PVCs can be configured for use with point-to-point interfaces and defined in
a context or they can be bound to link IDs defined in SS7 routing domains.
Refer to the chapter titled System Element Configuration Procedures in the System Administration Guide for
information on configuring ATM interfaces.
Creating and Configuring Frame Relay Ports (2.5G only)
Frame Relay ports and their associated DLCIs can be configured for communication with 2G Base Station
subsystem (BSS) for an SGSN implementation.
Refer to the chapter titled System Element Configuration Procedures in the System Administration Guide for
information on configuring Frame Relay ports.
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Configuring APS/MSP Redundancy
Configuring APS/MSP Redundancy
ASP/MSP redundancy is only available for the OLC2 and CLC2 line cards. It is setup per linecard -- all ports
share the same setup.
APS is enabled with the redundancy command in the Card configuration mode.
Important
At this time the aps command in the Card Configuration Mode chapter is still in development and should
not be used. The parameters are all set by default and cannot be changed or disabled.
• Related configuration for signal degrade and signal failure bit error rate thresholds for high path, low
path, and transport overhead - use the commands in the Port Channelized configuration mode.
For command details, refer to the Card Configuration Mode Commands chapter and the Port Configuration
Mode Commands chapter in the Cisco UMTS Command Line Interface Reference.
Step 1
Step 2
Configure a line card for either SONET or SDH.
Configure APS for a SONET line card or MPS for an SDH line card.
Use the configuration example below:
Example Configuration
Use the following example (replacing specific values) to setup a CLC2 (Frame Relay) line card:
config
card 27
framing sdh e1
header-type 4-byte
initial-e1-framing standard
redundancy aps-mode
service-type frame-relay
no shutdown
end
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Example Configuration
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CHAPTER
5
3G-2G Location Change Reporting
3G/2G Location Change Reporting on the SGSN facilitates location-based charging on the GGSN by providing
the UE\'s location information when it is in connected mode.
The SGSN notifies the GGSN whenever one of the following changes:
• The serving Cell Global Identity (CGI), or
• The Service Area Identity (SAI), or
• The Routing Area Identity (RAI).
Important
With Release 16, the new "Location-reporting in connected-mode" license is required to enable Location
Change Reporting functionality. For details, contact your Cisco Account Representative.
• Feature Description, page 159
• How it Works, page 160
• Configuring Location Change Reporting, page 162
Feature Description
The 3G/2G Location Change Reporting feature enables the operator to charge the user for location-based
services. Location-based charging is a values-added function that ensures subscribers pay a premium for
operator-determined location-based services, such as service in a congested area.
This optional feature functions in accordance with 3GPP TS 23.060, Release 9, sections 12.7.5 and 15.1.3
and requires an additional license - the Location Reporting License. With the license, the operator uses the
CLI to enable the feature independently for each access type: GPRS (2G) or UMTS (3G).
Relationships
The SGSN works with the GGSN for this feature. The GGSN must send subscription information to the SGSN
for the 3G/2G Location Change Reporting feature to work.
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License
This feature is independent of user location information (ULI) configuration, which allows GTP-C messages
to be used for carrying user location information to the GGSN.
License
A feature-specific license is required. Please consult your Cisco Account Representative for information about
the specific license. For information on installing and verifying licenses, refer to the "Managing License Keys"
section of the Software Management Operations chapter in the System Administration Guide.
Standards Compliance
The SGSN 3G/2G Location Change Reporting feature complies with the following standards:
• 3GPP TS 23.060 Release 9
• 3GPP TS 29.060 Release 9.7.0
How it Works
When the Location Change Reporting feature is enabled, the SGSN advertizes support for location change
reporting to the GGSN by including an extension header - MS-Info-Change-Reporting indication - in the
Create-PDP-Context-Request (CPCQ) or the Update-PDP-Context-Request (UPCQ) GTP-C messages (as
specified in section 6.1.5 of TS 23.060, R9).
The SGSN initiates the process to report the UE location when subscription information is received from the
GGSN. The SGSN decodes the MS-Info-Change-Reporting-Action IE in the CPCR, the UPCQ, and the
UPCUPCR messages received from the GGSN that request the SGSN to check user locations.
The SGSN uses cell update procedures, location reporting procedures, and routing area update (RAU)
procedures to identify changes in the serving cell (2G), or in the service area (3G), or in the routing area
respectively to identify location changes. In a 2G network, the SGSN sends location information to the GGSN
when it receives a cell update from a BSC. In a 3G network, the SGSN sends information to the GGSN when
it receives location reports from the RNC. If the GGSN subscribes to the RAI changes and the UE performs
an RAU, then the SGSN informs the GGSN of the new RAI.
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Call Flows
Call Flows
The following call flows illustrate system behavior when the feature is enabled.
Figure 17: 2G Subscription
1 Subscription is created.
2 Determines if subscription is present.
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Configuring Location Change Reporting
3 Location is sent to all GGSNs to which the UE subscribes.
Figure 18: 3G Subscription
Figure 19: Delete Subscription
Configuring Location Change Reporting
By default, Location Change Reporting is disabled. Reporting to the GGSN is easily enabled in the Call
Control Profile configuration mode.
The following configuration enables this feature:
config
call-control-profile <cc_profile_name>
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Verifying the Location Change Reporting Configuration
location-reporting { gprs | umts }
exit
Notes:
• The command can be repeated to enable location change reporting for GPRS (2G) and UMTS (3G).
The following configuration disables this feature:
config
call-control-profile <cc_profile_name>
remove location-reporting { gprs | umts }
exit
Notes:
• Using the remove keyword with the command disables the feature.
Verifying the Location Change Reporting Configuration
This section explains how to display the configuration after saving it in the .cfg file as described in the System
Administration Guide.
Verification for the call control profile configuration is accomplished via the corresponding show command
in Exec Mode:
show call-control-profile
[local]S4SGSN_Sim show call-control-profile full name ccprof1
Call Control Profile Name = ccprof1
Accounting Mode (SGW)
GPRS Attach All
GPRS Attach All Failure Code
UMTS Attach All
UMTS Attach All Failure Code
. . .
. . .
Location Reporting for UMTS
Location Reporting for GPRS
EPS Attach Restrict
Voice Unsupported
IMSI Attach Fail
CSFB Restrictions
:
:
:
:
:
None
Allow
14
Allow
14
: Enabled
: Enabled
: FALSE
: FALSE
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CHAPTER
6
APN-OI-Replacement for Gn-SGSN
• Feature Description, page 165
• How It Works, page 166
• Monitoring and Troubleshooting, page 168
Feature Description
Overview
Beginning with release 19.4, in compliance with 3GPP TS 29-003, decoding of the APN-OI-Replacement IE
is supported by Cisco Gn-SGSNs using either a Gr MAP or an S6d Diameter interface.
The Gn-SGSN accepts the APN-OI-Replacement field included as part of the GPRS subscription. Typically,
the field value, stored at the HLR/HSS as part of the subscription data, is a domain name for a specific GGSN.
The value in the APN-OI-Replacement field is intended to replace the APN-OI (derived from the IMSI) during
the GGSN selection process. The replacement results in the construction of a fully qualified domain name
(FQDN) APN, for a preferred GGSN, to be used for DNS resolution.
Supported Functions
UE-Level
• The Gn-SGSN supports decoding of a UE-level APN-OI-Replacement IE from the HLR/HSS via either
MAP or Diameter interface.
• The Gn-SGSN stores the UE-level APN-OI-Replacement value as a subscription database record.
• The Gn-SGSN uses the APN-OI-Replacement only for DNS translation in selection of a Home GGSN.
• The APN sent to other entities (GGSN/SGSN, CGF) is not affected by APN-OI replacement.
APN-Level
• The Gn-SGSN supports decoding of a APN-level APN-OI-Replacement IE from the HLR/HSS via
either MAP or Diameter interface.
• The Gn-SGSN stores the APN-level APN-OI-Replacement value per APN as a subscription database
record.
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How It Works
• The Gn-SGSN uses the APN-level APN-OI-Replacement, even when a UE-level APN-OI-Replacement
is present, because the APN-level APN-OI-Replacement has higher priority.
• The Gn-SGSN uses the APN-OI-Replacement only for DNS translation while accessing Home GGSN.
• The APN sent to other entities (GGSN/SGSN, CGF) is not affected by APN-OI replacement.
Gn-SGSN
• The Gn-SGSN indicates APN-level and UE-level APN-OI replacements received in subscriptions as
part of the output generated by the show subscriber gprs-only | sgsn-only full all command.
• The Gn-SGSN applies APN-level APN-OI-Replacement when both APN-level and UE-level APN-OI
replacement are available for a PDP context.
Benefits
This feature makes it possible for the operator to use UE-level and/or APN-level APN-OI replacement to
substitute an APN-OI per UE or per APN and then redirects the PDP session to a different GGSN.
This fully-compliant 3GPP functionality enables operators to differentiate service or customer UE and/or
APN levels based on the HLR/HSS subscription.
Limitations
The Gn-SGSN does not handle EPS subscription. This means that even though the Gn-SGSN supports S6d,
the APN-OI-Replacement in an EPS subscription is not applicable.
Related Product Support
Decoding of this AVP is supported by both the Cisco S4-SGSN and MME for EPS subscriptions.
License Information
This feature is enabled by default and does not require a feature license.
Configuration
Because this feature is 3GPP compliant and does not require enabling or configuration, there are no CLI
commands or keywords specific to this feature.
How It Works
The Gn-SGSN supports decoding of the UE and/or APN level APN-OI-Replacement IE received in GPRS
subscriptions on either the Gr interface or the S6d interface.
In accord with 3GPP TS 23.060:
• UE-level APN-OI-Replacement field values are conditionally stored as permanent data in the HSS/HLR
and the SGSN.
• APN-level APN-OI-Replacement field values are conditionally stored as permanent data in the HSS
and the SGSN.
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How It Works
• APN-level APN-OI-Replacement has the same role as UE-level APN-OI-Replacement. If both the
APN-level APN-OI-Replacement and the UE-level APN-OI-Replacement are present, the APN-level
APN-OI-Replacement has a higher priority than UE-level APN-OI-Replacement.
The format of the domain name used in the APN-OI-Replacement field (as defined in 3GPP TS 23.060 and
3GPP TS 23.401) is the same as the default APN-OI except that it may be preceded by one or more labels,
each separated by a dot.
• Example 1: province1.mnc012.mcc345.gprs
• Example 2: ggsn-cluster-A.provinceB.mnc012.mcc345.gprs
The APN-OI-Replacement handling is case insensitive.
The APN constructed using the APN-OI-Replacement field is only used for DNS translation to locate the
Home GGSN. DNS translation for other entities is unaffected.
Flow
1 During a 2G/3G Attach procedure, the Gn-SGSN receives an Insert Subscriber Data (ISD) during UGL/ULR
from the HLR/HSS.
2 APN-OI-Replacement IE is present in the Subscription-Data AVP sent in an Insert-Subscriber-Data-Request
(IDR) if the UE-level APN-OI-Replacement has been added or modified in the HSS.
APN-OI-Replacement IE is present in the GPRS-Subscription-Data sent in an Insert-Subscriber-Data
(ISD) if the UE-level APN-OI-Replacement has been added or modified in the HLR.
3 APN-OI-Replacement IE is present in the PDP-Context AVP sent within an Insert-Subscriber-Data-Request
(IDR) if the APN-level APN-OI-Replacement has been added or modified in the HSS.
APN-OI-Replacement IE is present in the PDP-Context IE in the GPRS-Data-List sent within an
Insert-Subscriber-Data (ISD) if the APN-level APN-OI-Replacement has been added or modified in the
HLR.
4 After receiving an APN-OI-Replacement from an HLR/HSS,
• the Gn-SGSN decodes the IE,
• the Gn-SGSN replaces the stored information (if any) with the received APN-OI-Replacement under
the subscription dB record for the subscriber on the SGSN,
• during activation of the PDP context, the Gn-SGSN presents this replacement APN-OI to be used
for the DNS resolution to determine the GGSN.
5 The HLR (MAP) removes the UE-level APN-OI-Replacement by setting the "APN-OI-Replacement
withdraw" bit of the Delete-Subscriber-Data (DSD), sent over Gr.
The HSS removes the UE-level APN-OI-Replacement by setting the "APN-OI-Replacement" bit of the
Delete-Subscriber-Data-Request (DSR) flag field of S6d.
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Monitoring and Troubleshooting
Monitoring and Troubleshooting
Monitor Protocol
Monitor Protocol functionality is supported for this feature and can be used by enabling MAP (55), Diameter
(36), and DNS Client (70).
Caution
Protocol monitoring can be intrusive to subscriber sessions and could impact system performance. We
recommend that you contact your Cisco Support Representative prior to using it for troubleshooting.
Output of "show" Commands
The Gn-SGSN displays received UE-level APN-OI-Replacements under GPRS subscriptions and APN-level
APN-OI-Replacements under PDP subscription data of the output generated by the show subscriber [
gprs-only | sgsn-only ] full imsi imsi commands.
Quick Check
To quickly check for APN-OI-Replacement use the following grep command with either the gprs-only or
the sgsn-only keyword:
show subscribers gprs-only full imsi imsi | grep Repl
The following illustrates the type of output generated by the above command. The first line is for UE-level
replacement information and the second line illustrates APN-level replacement information:
APN OI Replacement : abc.ggg.mnc009.mcc262.gprs
APN OI Replacement: : ggg.mnc009.mcc262.gprs
Full Display
To generate the full output, use the same command without the grep option:
show subscribers gprs-only full imsi imsi
The following is a limited sample of the display that is generated. The entries for APN-OI-Replacement are
in bold:
[local]asr5000# show subscribers sgsn-only full all
Username: 491740460103
Access Type: sgsn
Network Type: IP
Access Tech: WCDMA UTRAN
callid: 01317b21
msid: 262090426000193
state: Connected
connect time: Sun Apr 24 12:20:44 2016 call duration: 00h00m11s
idle time: 00h00m00s
Imsimgr Instance: 1
Temporary Imsimgr instance: 0
Operator Policy Name: policy1
…
EPS Subscription:
None:
GPRS Subscription:
APN OI Replacement
PDP Subscription Data:
PDP Context Id: 1
APN: WAP98.TESTNETZ-VD2.DE
APN OI Replacement:
PDP Type: IPv4
PDP Address Type: Dynamic
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: op1.mnc009.mcc262.gprs
APN-OI-Replacement for Gn-SGSN
Monitoring and Troubleshooting
Charging Characteristics: Normal Billing
VPLMN Address Allowed : Not Allowed
…
…
The highlighted entry under the GPRS Subscription section lists the information for a UE-level
APN-OI-Replacement.
The highlighted entry under the PDP Subscription Data section lists the information for an APN-level
APN-OI-Replacement.
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CHAPTER
7
APN Restriction
This chapter describes the APN Restriction feature and provides detailed information on the following:
• Feature Description, page 171
• How it Works, page 172
• Configuring APN Restriction, page 174
• Monitoring and Troubleshooting the APN Restriction, page 175
Feature Description
The reception, storage, and transfer of APN Restriction values is used to determine whether a UE is allowed
to establish PDP Context or EPS bearers with other APNs. This feature is supported by both the Gn/Gp-SGSN
and the S4-SGSN.
During default bearer activation, the SGSN sends the current maximum APN restriction value for the UE to
the GGSN/P-GW in a Create PDP Context Request/ Create Session Request (CSR). The GGSN/P-GW will
have an APN restriction value for each APN. The UE\'s APN Restriction value determines the type of
application data the subscriber is allowed to send. If the maximum APN restriction of the UE (received in the
CSR) and the APN Restriction value of the APN (for which activation is being requested) do not concur, then
the GGSN/P-GW rejects activation. The maximum APN restriction for a UE is the most restrictive based on
all already active default EPS bearers. The purpose of enabling APN Restriction in S4-SGSN is to determine
whether the UE is allowed to establish EPS Bearers with other APNs based on the Maximum APN Restriction
value associated with that UE.
This feature provides the operator with increased control to restrict certain APNs to UEs based on the type of
APN. This feature requires no special license.
APN Restriction for SGSN is enabled/ disabled in the Call-control-profile configuration mode using the
apn-restriction command.
Relationships to Other Features
APN Restriction value corresponding to each APN is known by the GGSN/P-GW. The Gn/S4-SGSN sends
the Maximum APN Restriction of the UE to the GGSN/P-GW in a Create PDP Context Request/ Create
Session Request. The GGSN/P-GW accepts or rejects the activation based on the Maximum APN Restriction
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How it Works
of UE and APN Restriction value of that APN which is sent the Create PDP Context Request/ Create Session
Request
How it Works
During default bearer activation the Gn/S4-SGSN sends the current Maximum APN Restriction value for the
UE to the GGSN/ P-GW in the Create PDP Context Request/ Create Session Request (if it is the first activation
for that UE or if the APN Restriction is disabled, Maximum APN restriction will be "0" in the Create PDP
Context Request/ Create Session Request). The GGSN/P-GW has an APN restriction value for each APN. If
the Maximum APN Restriction for the subscriber is received in the Create PDP Context Request/ Create
Session Request and APN Restriction value of the APN to which activation is being requested do not concur
then the GGSN/P-GW rejects the activation by sending a Create PDP Context / Create Session Response
failure message to the G/S4-SGSN with EGTP cause "EGTP_CAUSE_INCOMPATIBLE_APN_REST_TYPE
(0x68)".
If the Maximum APN Restriction of the subscriber and APN Restriction of the APN to which activation is
ongoing agree as per APN Restriction rules, the GGSN/P-GW sends the APN Restriction value of the APN
in the Create PDP Context / Create Session Response as success during activation. The Gn/S4-SGSN updates
the APN restriction value of that PDN connection with the value received from GGSN/P-GW in the Create
PDP Context/ Create Session Response. The APN restriction value can be received by a new SGSN through
context response and forward re-location request messages.
The combination of APN Restriction values of all the PDN connections of a particular UE should be valid
and the maximum APN restriction value of the UE should be updated whenever the APN restriction value of
a PDN connection is updated.
Table below displays the valid combinations of APN restriction values:
Table 13: APN restriction values
Maximum APN
Restriction Value
Type of APN
Application Example
APN Restriction Value
allowed to be
established
0
No Existing Contexts or Restriction
All
1
Public-1
WAP or MMS
1, 2, 3
2
Public-2
Internet or PSPDN
1, 2
3
Private-1
Corporate (for example
MMS subscribers)
1
4
Private-2
Corporate (for example
non-MMS subscribers)
None
The valid combination of APN restriction values is achieved in the Gn/ S4-SGSN based on the APN restriction
value of the most restrictive PDN connection. If the bearer with the most restrictive APN restriction value
gets de-activated, the maximum APN restriction value is re-calculated from among the remaining active
default bearers.
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Limitations
In the Create PDP Context /Create Session Request during default bearer activation, the Gn/S4-SGSN sends
the Maximum APN Restriction Value for the UE. If no value is available (if this default bearer is the first
activation) then, the Maximum APN restriction value will be "0" in Create Session Request. A value of "0"
in the Create PDP Context / Create Session Request for Maximum APN restriction indicates there are no other
existing PDN connections for the UE or APN restriction is disabled.
If the APN restriction value received in the Create PDP Context / Create Session Response during activation
violates the current Maximum APN restriction, then the SGSN rejects the activation and also de-activates any
other PDN connection to the same APN. The SGSN considers the APN restriction received in latest Create
PDP Context / Create Session Response as the latest value of the APN restriction associated with that APN.
If there are any other PDN connections to this APN, the SGSN updates the APN restriction associated with
those PDN connections. If the APN restriction value is not violated then the SGSN updates the APN restriction
value for that PDN connection and any other PDN connection to the same APN with the value received in
the Create PDP Context / Create Session Response and re-calculates the Maximum APN restriction value for
MS.
If APN restriction is enabled, but the SGSN does not receive any APN restriction value in the Create PDP
Context / Create Session Response and if another PDN connection exists to the same APN, the value of APN
restriction is copied from that APN. If no value is available, the APN restriction value is assumed to be "0".
If the current Maximum APN restriction value for the UE is present and the SGSN receives a new default
bearer activation request to another APN, while the APN restriction feature is enabled, the activation is rejected
with the appropriate sm cause.
If the Gn/ S4-SGSN receives a Create PDP Context/Create Session Response as failure from the P-GW with
EGTP cause "EGTP_CAUSE_INCOMPATIBLE_APN_REST_TYPE (0x68)", then the Gn/ S4-SGSN sends
an activate reject to the MS with SM cause "(112) APN restriction value incompatible with active PDP context".
Any de-activate request sent to the MS due to APN Restriction violation also has the same SM cause.
For every new activation request, the SGSN re-calculates the Maximum APN Restriction from among other
currently active PDN connections (excluding those PDNs for which any de-activation is ongoing.)
The APN restriction values are recovered during session recovery. In old SGSN ISRAU, the APN restriction
associated with each PDN is sent to the peer in Context Response. In old SGSN SRNS re-location, the APN
restriction associated with each PDN connection is sent to the peer in Forward Re-location Request.
In IRAT procedures, the APN restriction for each PDN connection is transferred internally during IRAT and
these values are used for subsequent activations after IRAT.
In new SGSN ISRAU, the APN restriction values received in context response are used in the subsequent
activations after ISRAU.
In new SGSN SRNS, the APN restriction values received in the forward re-location are used in subsequent
activations after SRNS re-location.
Limitations
Consider the scenario where APN restriction is enabled, but no value for APN restriction is received in the
Create PDP Context / Create Session Response and no other PDN connections exists to the same APN. An
APN restriction value of "0" is assigned to that PDN connection to denote that APN restriction value is invalid
for that PDN. During subsequent activations for the subscriber, if the SGSN receives a valid APN Restriction
corresponding to the same APN, then the APN Restriction value will be updated for the existing PDNs as
well. If not, when a subsequent activation happens with an APN for which SGSN receives valid APN Restriction
value, the existing PDNs with invalid (that is "0") APN Restriction values will be de-activated. This behaviour
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Standards Compliance
is also observed when the subscriber changes from one PLMN to another PLMN, where the APN Restriction
is enabled in the new PLMN but disabled in the old PLMN.
The SGSN does not support APN Restriction if it is enabled during an ongoing call. For APN Restriction to
be applied correctly for a subscriber, all the PDP contexts of the subscriber should be created after the APN
Restriction is enabled.
Standards Compliance
The APN Restriction feature complies with the following standards:
• 3GPP TS 23.060 (version 10)
• 3GPP TS 29.274 (version 10)
Configuring APN Restriction
This section describes how to configure the APN Restriction feature. The following command is used to
configure the APN restriction feature:
config
call-control-profile profile_name
apn-restriction update-policy deactivate { least-restrictive | most-restrictive }
exit
Notes:
• The least or most restrictive values of the APN restriction are applicable only for the Gn SGSN, as the
APN restriction can be present in UPCQ/UPCR for Gn SGSN and this configuration is required to
determine the PDN to be de-activated when an APN restriction violation occurs during modification
procedures in the Gn SGSN. In the case of S4-SGSN, the APN restriction value is received by the
S4-SGSN only in Create Session Response during activation. During activation in S4-SGSN, a PDN
connection that violates the current Maximum APN restriction is always de-activated. Therefore in the
case of S4-SGSN, this CLI is used only for enabling or disabling APN restriction.
For more information on this CLI refer to the Command Line Interface Reference manual.
Verifying the APN Restriction Configuration
The show configuration command is used to verify the configuration of the APN Restriction feature. Listed
below is an example of the show configuration command where APN restriction is configured:
[local]asr5000 show configuration
config
call-control-profile test
apn-restriction update-policy deactivate least-restrictive
exit
end
[local]asr5000
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Monitoring and Troubleshooting the APN Restriction
Monitoring and Troubleshooting the APN Restriction
This section provides information on how to monitor APN restriction and to determine that it is working
correctly. The following show commands support the monitoring and trouble shooting of the APN restriction
feature:
• The show subscribers SGSN-only full and show subscribers gprs-only full commands display the
APN Restriction value of each PDP Context.
• The session-disconnect reason for APN Restriction is sgsn-apn-restrict-vio.
• The show gmm-sm statistics verbose command displays following counters related to the cause "APN
restriction value incompatible with active PDP context":
◦Deactivation Causes Tx
◦3G-APN Restr val Incomp With Ctx
◦2G-APN Restr val Incomp With Ctx
◦Activate Primary PDP Context Denied
◦3G-APN-Restriction Incompatible
◦2G-APN-Restriction Incompatible
For detailed parameter descriptions see the Statistics and Counters Reference.
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CHAPTER
8
Attach Rate Throttling
This chapter describes the Attach rate throttling feature and includes the following topics:
• Feature Description, page 177
• How it Works, page 178
• Configuring the Attach Rate Throttling Feature, page 180
• Monitoring and Troubleshooting the Attach Rate Throttling Feature, page 180
Feature Description
The SGSN is located at the core of the GPRS Network. It is connected to several nodes in the network like
the HLR, GGSN, MSC/VLR, and RNC/BSC so on.
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How it Works
The diagram below depicts the SGSN and its network connections in a GPRS Network.
Figure 20: SGSN in a GPRS Network.
How it Works
Attach Rate Throttling Feature
The Mobile Stations access the services of a GPRS Network by attaching themselves to the network through
SGSN nodes. The SGSN can process more than "5000" such attach requests per second. In a typical network
the SGSN can be connected to other network elements over a narrow band link and these network elements
may not able to process requests at high rates such as the SGSN. This may lead to an overload condition in
other network elements. To prevent such scenarios, the Attach Rate throttling feature is designed, this feature
limits the rate at which the SGSN processes requests.
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Attach Rate Throttling Feature
The diagram below depicts the high level software architecture in a SGSN node:
Figure 21: Software architecture in a SGSN node.
In a SGSN node the Link Manager/Gb Managers and the IMSI Manager perform the following tasks:
1 Link Manager/GbManager:Manages the links towards different network elements such as RNC, HLR
so on. The Attach requests and ISRAU requests received on the Link Manager/Gb Manager are sent to
the IMSI Manager.
2 IMSI Manager: The IMSI Manager assigns the new connection requests to the various Session Managers.
The assignment is done after verifying the load on the Session Managers. The Attach Rate Throttling
feature is implemented at the IMSI Manager.
The IMSI manager is responsible for identifying the Session Manager to handle the incoming requests. The
requests are then queued for the identified Session Manager. These queues are processed at the maximum
possible rate. With the introduction of Attach Rate Throttling feature, an intermediary queue is introduced
which buffers the incoming requests and processes these requests at the rate configured by the operator. The
requests from the intermediary queue are processed at the configured attach rate and then forwarded to the
identified Session Manager queue for normal processing. This allows the operator to cap the rate at which
new requests are accepted by the SGSN. An overload scenario can be prevented with the introduction of the
Attach Rate Throttling feature. The intermediary queues are operational only when the Attach Rate Throttling
feature is enabled. If the feature is disabled, attach requests are directly queued for processing at the identified
Session Manager.
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Limitations
Limitations
The operator must ensure that an optimal attach rate must be configured based on the network conditions:
1 If the incoming requests arrive at a very high rate and the attach rate configured to a very low rate, the
requests will be dropped from the intermediary queue once the queue is full. The IMSI Manager can send
a reject response with the appropriate reject cause codes for such all dropped requests or silently drop the
requests.
2 If the configured attach rate is very low, the requests waiting time in the queue increases. The "t3310"
timer at the MS expires and the MS will have to re-transmit the request. The IMSI Manager drops all
requests which have waited in the queue for more than the configured wait time.
The configured Attach rate must have an optimal processing rate and waiting time.
Configuring the Attach Rate Throttling Feature
The following command is used to configure the Attach Rate Throttling feature, this command configures an
attach rate throttle mechanism to control the number of new connections (attaches or inter-SGSN RAUs),
through the SGSN, on a per second basis:
config
network-overload-protection sgsn-new-connections-per-second _new_connections action { drop |
reject with cause { congestion | network failure } } [ queue-size queue_size ] [ wait-time wait_time ]
default network-overload-protection sgsn-new-connections-per-second
exit
Notes:
• The default mode of the command disables the Attach Rate Throttling feature.
• For detailed information on the command see, Cisco ASR 5x00 Command Line Interface Reference.
Monitoring and Troubleshooting the Attach Rate Throttling
Feature
Attach Rate Throttling Show Commands and Outputs
This section provides information regarding show commands and/or their outputs in support of the Attach
Rate Throttling feature.
The counters for this feature are available under the show command show gmm-sm statistics, as a part of
the Network Overload Protection counters.
• Network Overload Protection
•
◦Number of valid packets processed in the last sec.
◦Number of packets in Q in the last tick
◦Packets to be dequeued in the last tick
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Attach Rate Throttling Show Commands and Outputs
◦Number of new requests processed from the pacing queue in the last tick
◦Number of requests dropped from the pacing queue in the last tick
◦Average Number of requests processed per min (1 min)
◦Average Number of requests processed per min (5 min)
◦Average Number of requests processed per min (10 min)
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Attach Rate Throttling Show Commands and Outputs
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9
Backup and Recovery of Key KPI Statistics
This feature allows the backup of a small set of GGSN, P-GW, SAEGW, and/or S-GW key KPI counters
for recovery of the counter values after a session manager (SessMgr) crash.
This section includes the following information:
• Feature Description, page 183
• How It Works, page 183
• Configuring Backup Statistics Feature, page 186
• Managing Backed-up Statistics, page 187
Feature Description
Before the Backup and Recovery of Key KPI Statistics feature was implemented, statistics were not backed
up and could not be recovered after a SessMgr task restart. Due to this limitation, monitoring the KPI was a
problem as the SGSN would loose statistical information whenever task restarts occurred.
KPI calculation involves taking a delta between counter values from two time intervals and then determines
the percentage of successful processing of a particular procedure in that time interval. When a SessMgr crashes
and then recovers, the SGSN loses the counter values - they are reset to zero. So, the KPI calculation in the
next interval will result in negative values for that interval. This results in a dip in the graphs plotted using
the KPI values, making it difficult for operations team to get a consistent view of the network performance
to determine if there is a genuine issue or not.
This feature makes it possible to perform reliable KPI calculations even if a SessMgr crash occurs.
How It Works
A key set of counters, used in KPI computation will be backed up for recovery if a SessMgr task restarts. The
counters that will be backed up are determined by the KPIs typically used in several operator networks.
The backup of counters is enabled or disabled via configuration. The configuration specifies the product
(currently only supported by the SGSN) for which counters will be backed up and also a time interval for the
back up of the counters.
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Architecture
The backed up counters can be identified via CLI generated displays or via display of the four SGSN-specific
backup statistics schemas: iups-bk, gprs-bk, map-bk, and sgtp-bk. The operator can use these schemas to
compute the KPI as statistics will have the recovered counters. During the display and the backup processes,
both the normal counters and backed-up counters are cumulatively displayed or backed up.
• iups-bk schema - This schema is used for 3G GMM-SM counters which are backed up. The counters
in this schema are pegged per IuPS service. Each line of output is per IuPS service. Additionally, there
will be one set of consolidated counters for all IuPS services which is displayed with the SGSN service
name.
• gprs-bk schema - This schema is used for 2G GMM-SM counters which are backed up. The counters
in this schema are pegged per GPRS service. Each line of output is per GPRS service. Additionally,
there will be one set of consolidated counters for all GPRS services which is displayed with the SGSN
service name.
• map-bk schema - This schema is used for MAP and SMS counters which are backed up. The counters
in this schema are pegged per MAP service. Each line of output is per MAP service.
• sgtp-bk schema - This schema is used for GTPU counters which are backed up. The counters in this
schema are pegged per IuPS and SGTP service, one per line. Additionally, there will be one line of
output which represents the counters consolidated for all IuPS and SGTP services.
Architecture
When this feature is enabled (see Configuring Backup Statistics Feature below), the SGSN only backs up the
counters maintained at the SessMgr. Counters maintained by other managers, such as the LinkMgr or SGTPMgr,
are not backed up. The recovery function does not need to be configured or \'started\' as it occurs automatically
as needed when the feature is enabled.
The counters are backed up to the AAAMgr that is paired with the SessMgr. They are recovered from the
AAAMgr after a SessMgr task is killed. This feature makes use of the session recovery framework to backup
and retrieve the counters.
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Limitations
The following diagram depicts how backed-up statistics are maintained separately at the SessMgr and how
the cumulative values are backed up and recovered from the AAAMgr after SessMgr task recovery completes.
Figure 22: Back Up and Recovery of Statistics for SGSN
Limitations
• A backup interval must be specified and counters are backed up only at the specified interval. For
example, if the backup interval is specified as 5 minutes, then counters are backed up every 5 minutes.
Suppose backup happened at Nth minute and the configured backup interval is for every 5 minutes, then
if a task crash happens at N+4 minutes, the SGSN recovers only the values backed up at Nth minute and
the data for the past 4 minutes is lost.
• Only service level statistics are backed up and recovered. Any KPI that is monitored per other granularity,
such as per RA or per RNC, is not supported.
• Only statistics maintained at the SessMgr are backed up. Statistics at other managers, such as LinkMgr
and GbMgr are not backed up.
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Configuring Backup Statistics Feature
Configuring Backup Statistics Feature
For the Backup and Recovery of Key KPI Statistics feature to work, it must be enabled by configuring the
backup of statistics for the SGSN.
Configuration
The following CLI commands are used to manage the functionality for the backing up of the key KPI statistics
feature
Enabling
The following configures the backup of statistics for the SGSN and enables the Backup and Recovery of Key
KPI Statistics feature.
configure
statistics-backup sgsn
exit
Setting the Backup Interval
The following command configures the number of minutes (0 to 60) between each backup of the statistics.
When the backup interval is not specified a default value of 5 minutes is used as the backup interval
configure
statistics-backup-interval minutes
exit
Disabling
The following configures the SGSN to disable the backing up of statistics for the SGSN.
configure
no statistics-backup sgsn
exit
Notes:
• When the new keyword is used, only the recovered values will be displayed.
• If no session manager crash has occurred, the above commands output displays with the normal counter
values.
• If a session manager crash has happened, the above commands display the cumulative value so far
(including the backed up value).
• The display of the counters will be similar to the show sgsn-service statistics command output with
respect to naming and indentation. Only the subset of counters which are backed up will be displayed
with the recovered-values option.
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Verifying the Backup Statistics Feature Configuration
Verifying the Backup Statistics Feature Configuration
Use either the show configuration command or the show configuration verbose command to display the
feature configuration.
If the feature was enabled in the configuration, two lines similar to the following will appear in the output of
a show configuration [ verbose ] command:
statistics-backup mme
statistics-backup-interval 5
Notes:
• The interval displayed is 5 minutes. 5 is the default. If the statistics-backup-interval command is
included in the configuration, then the 5 would be replaced by the configured interval number of minutes.
• If the command to disable the feature is entered, then no statistics-backup line is displayed in the output
generated by a show configuration [ verbose ] command.
Managing Backed-up Statistics
A new keyword, recovered-values, is used with existing show and clear commands to either generate a display
of the backed-up statistics or to clear the backed-up statistics.
Displaying Backed-up Statistics
Use one of the following commands to generate a display of the backed up statistics:
• show gmm-sm statistics [ recovered-values ] [ verbose ]
• show gmm-sm statistics sgsn-service sgsn_service_name [ recovered-values ] [ verbose ]
• show gmm-sm statistics gprs-service gprs_service_name [ recovered-values ] [ verbose ]
• show gmm-sm statistics iups-service iups_service_name [ recovered-values ] [ verbose ]
• show map-statistics [ recovered-values ]
• show map statistics map-service map_service_name [ recovered-values ]
• show sms statistics [ recovered-values ]
• show sms statistics name map_service_name [ recovered-values ]
• show sms statistics [ gprs-only | sgsn-only ] [ recovered-values ]
• show sgtpu statistics [ recovered-values ]
• show sgtpu statistics iups-service iups_service_name [ recovered-values ]
• show sgtpu statistics sgtp-service sgtp_service_name [ recovered-values ]
Notes:
• When the recovered-values keyword is used, output includes both current + recovered backed-up
statistical values.
• If no SessMmgr crash has occurred, then the recovered values in the output of the above commands will
be 0 (zero).
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Managing Backed-up Statistics
Clearing Backed-up Statistics
Use one of the following commands to clear (delete) the backed-up statistics. Note that the order entry for the
service name identification varies in some of the commands. As well, the verbose keyword is not used with
the clear commands.
• clear gmm-sm statistics [ recovered-values ]
• clear gmm-sm statistics [ recovered-values ] sgsn-service sgsn_service_name
• clear gmm-sm statistics [ recovered-values ] gprs-service gprs_service_name
• clear gmm-sm statistics [ recovered-values ] iups-service iups_service_name
• clear map-statistics [ recovered-values ]
• clear map statistics name map_service_name [ recovered-values ]
• clear sms statistics [ recovered-values ]
• clear sms statistics name map_service_name [ recovered-values ]
• clear sms statistics [ gprs-only | sgsn-only ] [ recovered-values ]
• clear sgtpu statistics [ recovered-values ]
• clear sgtpu statistics iups-service iups_service_name [ recovered-values ]
• clear sgtpu statistics sgtp-service sgtp_service_name [ recovered-values ]
Notes:
• When the recovered-values keyword is used, only the recovered values will be cleared.
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CHAPTER
10
Cause Code #66
• Feature Description, page 189
• How It Works, page 190
• Configuring PDP Activation Restriction and Cause Code Values, page 190
• Monitoring and Troubleshooting the Cause Code Configuration, page 195
Feature Description
This feature is developed to achieve compliance with Release 11 3GPP Technical Specifications. The Release
11 3GPP Technical Specification introduced a new ESM/SM cause code "Requested APN not supported in
current RAT and PLMN combination (cause code 66). This ESM/SM cause is used by the network to indicate
that the procedure requested by the UE is rejected as the requested APN is not supported in the current RAT
and PLMN. A UE which receives this cause will stop accessing the APN in the current RAT, but as soon as
it enters another RAT type it will retry the APN.
In earlier releases only cause code 27 and cause code 33 were supported, these codes were not very effective
in restricting APN in a particular RAT. For example, UE which has received cause 27 (with timer = 24hrs)
will stop retrying a PDN connection in every RAT for 24 hrs. This is not the desired behavior in some cases
APN cannot be restricted in a particular RAT. If the SGSN sends cause code 33 to the UE for an IMS APN,
the UE/MS stops retrying the PDN connection for some time, but UE/MS will not automatically retry this
APN in 4G, even though the APN is available there. The introduction of cause code 66 resolves this issue as
the operator can block access to IMS APN in 2G/3G and can allow access in 4G.
Important
This feature is applicable for both SGSN and MME.
Important
This is a 3GPP Release 11 compliance feature, and will be applicable only to UEs capable of decoding
ESM/SM cause code 66.
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How It Works
How It Works
This feature is developed for both SGSN and MME. In the SGSN, activation restriction of PDP context on
the basis of access type can be configured using the restrict access-type command under the APN profile
configuration mode. This command is now extended to MME; a new keyword "eps" is introduced to configure
the APN profile to restrict the PDP context activation from EPS network access. If this CLI is enabled access
to APN's associated with this APN profile are not allowed on MME/SGSN. By default, any activation on
SGSN for this APN is rejected with cause code 'Requested APN not supported in current RAT and PLMN
combination66'. During mobility scenarios the PDPs related to this APN are deactivated on the SGSN and
the PDPs are also deactivated up to the GGSN/PGW.
On the MME attach is rejected if the default bearer related APN is not supported under the APN profile. By
default the EMM cause and the ESM cause in attach reject are 'ESM failure19' and 66 respectively.
If the first default bearer APN is allowed, after a successful attach if the subsequent second default bearer
APN is not supported, activation is rejected with cause 'Requested APN not supported in current RAT and
PLMN combination66'. This is default MME behavior.
During mobility procedures on MME, if APN is not supported for bundle, bearers will deactivated all the way
up to PGW and as well on MME for that particular bundle.
If the APN is not supported for all the bundles received from a peer node for a Tracking Area Update procedure
at a new MME, Tracking Area Update is rejected with EMM cause 'No Suitable Cells In tracking area 15'.
If the APN is not supported for all the bundles received from a peer node for SRNS relocation procedure at
the new MME, SRNS is rejected with GTPV2 cause 'Denied in RAT82' in Forward relocation response (if
the peer node is MME/S4 SGSN). SRNS is rejected with GTPV1 cause 'Relocation failure213' in Forward
relocation response if the peer node is a Gn Gp SGSN.
The operator can configure different cause values other than the default cause values mentioned in the scenarios
described above. For SGSN/MME cause code remapping is done by configuring various options of the
local-cause-code-mapping command under the Call Control Profile configuration mode (for both SGSN and
MME) and MME Service Configuration mode (for MME only).
Standards Compliance
This feature is developed to comply with the following standards:
• 3GPP TS 24.301, Release 11 (version 11.14.0)
• 3GPP TS 23.401,Release 11 (version 11.11.0)
• 3GPP TS 24.008,Release 11 (version 11.15.0)
• 3GPP TS 23.060,Release 11 (version 11.12.0)
Configuring PDP Activation Restriction and Cause Code Values
The following configuration procedures are used to configure this feature. The access type restriction, cause
code mapping for SGSN and MME can be configured using following procedures.
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Configuring PDP Activation Restriction
Configuring PDP Activation Restriction
The restrict access-type command under the APN profile configuration mode is used to configure PDP
activation restriction on the basis of access type, a new command option for EPS networks is introduced for
this feature. In earlier releases this command was supported only for GPRS and UMTS networks to perform
QoS related restrictions. Now this command is also used to configure the APN not supported in particular
RAT and PLMN combination. If this command is enabled, new PDP activations to an APN with which this
APN profile is associated are rejected. During handovers PDPs/PDNs are deactivated if the APN name matches
with this APN profile.
configure
apn-profile profile_name
[ no ] restrict access-type { eps | { { gprs | umts } [ qos-class { background | conversational |
interactive | streaming } ] } }
default restrict access-type { eps | gprs | umts }
end
Notes:
• This command is disabled by default.
• In earlier releases this command was applicable only for SGSN. It is now supported by MME also.
• If the operator does not include the optional qos-class keyword option, then complete APN restriction
is enabled and QoS related restrictions have no impact as QoS restriction is a subset of a complete APN
restriction.
Configuring SM Cause Code Mapping for SGSN
The following command is used remap the cause code 66 to an operator desired cause code. This cause code
is sent in activate rejection.
config
call-control-profile profile_name
[remove] local-cause-code-mapping apn-not-supported-in-plmn-rat sm-cause-code cause_number
exit
Notes:
• This mapping is not done by default.
• The keyword apn-not-supported-in-plmn-rat specifies the cause code for Requested APN not supported
in current RAT and PLMN combination.
• The keyword sm-cause-code specifies the SM cause code to be used towards the UE. The value can be
integer with range 1 up to 255.
Configuring ESM Cause Code Mapping for ESM Procedures (for MME)
The following command is used remap the ESM cause code sent in activate rejections (due to APN not
supported) to an operator desired ESM cause code.
config
call-control-profile profile_name
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Configuring EMM and ESM Cause Code Mapping for EMM Procedures (for MME)
[remove] local-cause-code-mapping apn-not-supported-in-plmn-rat esm-cause-code cause_number
esm-proc
exit
Notes:
• This mapping is not done by default.
• The keyword apn-not-supported-in-plmn-rat specifies the cause code for Requested APN not supported
in current RAT and PLMN combination.
• The keyword esm-cause-code specifies the ESM cause code to be used if a bearer management request
is rejected due to this configuration. The value can be integer with range 1 up to 255.
• The specified esm-cause-code is used if an ESM procedure is rejected under the error condition esm-proc.
This is specified as a keyword in the command.
Configuring EMM and ESM Cause Code Mapping for EMM Procedures (for
MME)
The following command under the Call Control Profile configuration mode is used remap the EMM and ESM
cause codes sent in activate rejections (due to APN not supported) to an operator desired ESM and EMM
cause codes.
config
call-control-profile profile_name
[remove] local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code cause_number
esm-cause-code cause_number [ attach [ tau ] | tau [attach ] ]
exit
Notes:
• This mapping is not done by default.
• The keyword apn-not-supported-in-plmn-rat specifies the cause code for Requested APN not supported
in the current RAT and PLMN combination.
• The keyword emm-cause-code specifies the EMM cause code to be used if a NAS request is rejected
due to this configuration. A valid EMM cause value is an integer from 2 through 111.
• The keyword esm-cause-code specifies the ESM cause code to be used if a NAS request is rejected due
to this configuration. A valid ESM cause value is an integer from 8 through 112.
• The keyword attach specifies the cause code to be used if an attach procedure is rejected under the
error conditions.
• The keyword tau specifies the cause code to be used if TAU procedure is rejected under the error
conditions.
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Configuring ESM Cause Code Mapping for ESM Procedures (MME Service Configuration Mode)
Configuring ESM Cause Code Mapping for ESM Procedures (MME Service
Configuration Mode)
The following command under the MME Service Configuration mode is used remap the ESM cause code
sent in activate rejections (due to APN not supported) to an operator desired ESM cause code.
config
context <context_name>
mme-service <service_name>
local-cause-code-mapping apn-not-supported-in-plmn-rat esm-cause-code <cause_number>
esm-proc
default local-cause-code-mapping apn-not-supported-in-plmn-rat esm-cause-code esm-proc
exit
Notes:
• The default cause code for esm-proc is 66.
• The keyword apn-not-supported-in-plmn-rat is used to specify the cause code for Requested APN
not supported in current RAT and PLMN combination.
• The keyword esm-cause-code is used to specify the ESM cause code to be used if a bearer management
request is rejected due to this configuration. The ESM cause value is an integer with range 8 up to 112.
• The specified esm-cause-code is used if an ESM procedure is rejected under the error condition esm-proc.
This is specified as a keyword in the command.
Configuring EMM and ESM Cause Code Mapping for EMM Procedures (MME
Service Configuration Mode)
The following command under the MME Service configuration mode is used remap the EMM and ESM cause
codes sent in activate rejections (due to APN not supported) to an operator desired ESM and EMM cause
codes.
config
context context_name
mme-service service_name
local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code cause_number
esm-cause-code cause_number [ attach [ tau ] | tau [ attach ] ]
default local-cause-code-mapping apn-not-supported-in-plmn-rat [ attach | tau ]
exit
Notes:
• The default cause code values for Attach procedure are emm-cause-code 19 and esm-cause-code 66.
The default cause code values for TAU procedure are emm-cause-code 15 and esm-cause-code 66.
• The keyword apn-not-supported-in-plmn-rat specifies the cause code for Requested APN not supported
in current RAT and PLMN combination.
• The keyword emm-cause-code specifies the EMM cause code to be used if a NAS request is rejected
due to this configuration. The EMM cause value is an integer with range 2 up to 111.
• The keyword esm-cause-code specifies the ESM cause code to be used if a NAS request is rejected due
to this configuration. The ESM cause value is an integer with range 8 up to 112.
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Verifying the Feature Configuration
• The keyword attach specifies the cause code to be used if an attach procedure is rejected under the error
conditions.
• The keyword tau specifies the cause code to be used if TAU procedure is rejected under the error
conditions.
Verifying the Feature Configuration
The configuration of this feature can be verified using the following show commands.
Execute the show configuration command to verify the configuration, the output displays the following
parameters based on the configuration:
• restrict access-type umts/gprs/eps
• local-cause-code-mapping apn-not-supported-in-plmn-rat sm-cause-code cause_number
• local-cause-code-mapping apn-not-supported-in-plmn-rat esm-cause-code cause_number esm-proc
• local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code 19 esm-cause-code 66 attach
• local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code 19 esm-cause-code 66 tau
• local-cause-code-mapping apn-not-supported-in-plmn-rat esm-cause-code 32 esm-proc
• local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code 15 esm-cause-code 66 attach
• local-cause-code-mapping apn-not-supported-in-plmn-rat emm-cause-code 19 esm-cause-code 66 tau
Execute the show apn-profile full profile_name command to verify the configuration, the output displays
the following parameters based on the configuration:
• Service Restriction for Access Type UMTS:
• Complete APN restricted : Enabled
• Service Restriction for Access Type GPRS:
• Complete APN restricted : Enabled
• Service Restriction for Access Type EPS:
• Complete APN restricted : Enabled
Execute the show call-control-profile full profile_name command to verify the configuration, the output
displays the following parameters based on the configuration:
• Mapped SM Cause For Req APN not sup in current RAT and PLMN combination: Not Configured
• Mapped SM Cause For Req APN not sup in current RAT and PLMN combination: Requested service
option not subscribed (33)
• Cause Code Mapping
• APN not supported PLMN-RAT esm-proc : Operator Determined Barring (esm-8)
• APN not supported PLMN-RAT Attach : ESM failure (emm-19), Requested APN not supported in
current RAT and PLMN combination (esm-66)
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Monitoring and Troubleshooting the Cause Code Configuration
• APN not supported PLMN-RAT TAU : ESM failure (emm-19), Requested APN not supported in current
RAT and PLMN combination (esm-66)
Execute the show mme-service name mme_service command to verify the configuration, the output displays
the following parameters based on the configuration:
• APN not supported PLMN-RAT esm-proc : Requested APN not supported in current RAT and PLMN
combination (esm-66)
• APN not supported PLMN-RAT Attach : ESM failure (emm-19), Requested APN not supported in
current RAT and PLMN combination (esm-66)
• APN not supported PLMN-RAT TAU : No Suitable Cells In tracking area (emm-15)
Monitoring and Troubleshooting the Cause Code Configuration
This section provides information on the show commands and bulk statistics available to support this feature.
Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs in support of this feature.
show gmm-sm statistics verbose
The following new parameters are added to this show command to display the statistics for this feature:
• 3G-Pri-Actv-APN-Not-Sup-Rej
• 2G-Pri-Actv-APN-Not-Sup-Rej
• 3G-APN-Not-Supported-in-PLMN-RAT
• 2G-APN-Not-Supported-in-PLMN-RAT
• APN Not Supported in PLMN RAT combination Statistics
• 3G-Pdp-Dropped-During-New-SGSN-RAU
• 2G-Pdp-Dropped-During-New-SGSN-RAU
• 3G-Pdp-Dropped-During-New-SGSN-SRNS
• Pdp-Dropped-During-3G-To-2G-IRAT
• 3G-Actv-NRPCA-Reject
• Pdp-Dropped-During-2G-To-3G-IRAT
The following statistics are MME specific:
• APN not sup PLMN-RAT
• Inbound Inter node SRNS failure
• APN not sup in PLMN/RAT
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Bulk Statistics
Bulk Statistics
The following statistics are included in the MME and SGSN Schemas in support of the feature.
MME Schema
• inter-node-srns-proc-fail-apn-not-supported
• inter-node-tau-proc-fail-apn-not-supported
• tai-esm-msgtx-pdncon-rej-apn-not-sup-in-plmn-rat
• tai-emm-msgtx-attach-rej-apn-not-sup-in-plmn-rat
• attach-proc-fail-apn-not-sup-in-plmn-rat
• esm-msgtx-pdncon-rej-apn-not-sup-in-plmn-rat
• emm-msgtx-attach-rej-apn-not-sup-in-plmn-rat
• emmdisc-apnnotsupinplmnrat
SGSN Schema
• 3G-actv-rej-apn-not-supported-in-plmn-rat
• 2G-actv-rej-apn-not-supported-in-plmn-rat
• 3G-actv-rej-apn-not-supported-in-plmn-rat-cum
• 2G-actv-rej-apn-not-supported-in-plmn-rat-cum
• 2G-3G-irat-pdp-drop-apn-not-supported-in-plmn-rat
• 2G-israu-pdp-drop-apn-not-supported-in-plmn-rat
• 3G-israu-pdp-drop-apn-not-supported-in-plmn-rat
• 3G-srns-pdp-drop-apn-not-supported-in-plmn-rat
• 3G-nrpca-pdp-drop-apn-not-supported-in-plmn-rat
• 3G-2G-irat-pdp-drop-apn-not-supported-in-plmn-rat
• 2G-inter-svc-rau-pdp-drop-apn-not-supported-in-plmn-rat
For descriptions of these variables, see the information for the SGSN and MME schema in the Statistics and
Counters Reference.
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11
Cause Code Mapping
Local Cause Code Mapping provides the operator with the flexibility to configure a preferred GMM cause
code to be sent to the UE in response to various failures, such a MAP failures. This section identifies the
various cause code mapping optionsand how they are configured.
• Cause Code Mapping, page 197
• Feature Description, page 197
• Configuring Cause Code Mapping, page 198
Cause Code Mapping
Local Cause Code Mapping provides the operator with the flexibility to configure a preferred GMM cause
code to be sent to the UE in response to various failures, such a MAP failures. This section identifies the
various cause code mapping optionsand how they are configured.
Feature Description
This feature enables the operator to configure (map) preferred failure code information to send to the UE in
reject messages.
Prior to release 16, the operator could map a preferred GMM reject cause code for the SGSN to send to a UE
in place of MAP cause \'roaming not allowed\' for MAP failures and to map a preferred GMM reject cause
code to be sent in a RAU Reject for inbound peer SGSN address resolution failures.
Beginning with release 16, additional local cause code mapping is possible:
• Mapping GSM-MAP cause code "unknown-subscriber" to GMM cause code "gprs-service-not-allowed"
if a response message comes without diagnostic information.
• Mapping GSM-MAP cause code unknown-subscriber with diagnostic information indicating
gprs-subscription-unknown to a preferred GMM cause code.
• Mapping GSM-MAP cause code unknown-subscriber with diagnostic information indicating
imsi-unknown to a preferred GMM cause code.
• Override the GMM cause sent to the MS in a RAU Reject during context transfer failure.
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Configuring Cause Code Mapping
• Override the cause sent in a Deactivate Request, to an MS, due to the GGSN becoming unreachable.
• Mapping an SM cause code for Deactivate PDP Requests during a path failure towards the GGSN.
Configuring Cause Code Mapping
Each mapping of a cause code is configured slightly differently. Each is illustrated below.
Configuring GMM Cause Codes to Replace MAP Cause Codes
The following configures the SGSN to include a preferred GMM cause code, in Reject messages to the UE,
in place of MAP failure cause 'unknown-subscriber' for MAP failures and inbound RAU context transfer
failures. Optionally, the Operator can map a specific GMM cause code if the SGSN receives additional MAP
failure diagnostic information.
configure
call-control-profile profile_name
local-cause-code-mapping map-cause-code { roaming-not-allowed gmm-cause-code gmm-cause |
unknown-subscriber { gmm-cause-code gmm-cause | map-diag-info { gprs-subscription-unknown
gmm-cause-code gmm_cause | imsi-unknown gmm-cause-code gmm_cause } } }
end
Notes:
• unknown-subscriber Instructs the SGSN to send a different GPRS mobility management (GMM) cause
code to a UE when the UE\'s access request is rejected due to map cause \'unknown-subscriber\'.
• gmm-cause-code gmm_cause identifies the replacement GMM cause code options include:
◦gprs-serv-and-non-gprs-serv-not-allowed
◦gprs-serv-not-allowed
◦gprs-serv-not-in-this-plmn
◦location-area-not-allowed
◦network-failure
◦no-suitable-cell-in-this-la
◦plmn-not-allowed
◦roaming-not-allowed-in-this-la
• map-diag-info gprs-subscription-unknown gmm-cause-code gmm_cause identifies a replacement
GMM cause code if additional \'gprs-subscription-unknown\' diagnostic MAP failure information is
received when the UE\'s access request is rejected due to map cause \'unknown-subscriber\'.
• map-diag-infoimsi-unknown gmm-cause-code gmm_cause identifies a replacement GMM cause code
if additional \'imsi-unknown\' diagnostic MAP failure information is received when the UE\'s access
request is rejected due to map cause \'unknown-subscriber\'.
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Verifying Configuration to Replace MAP Cause Codes
Verifying Configuration to Replace MAP Cause Codes
Mapping is performed in the call control profile.
Run the show call-control-profile full name profile_name command and review the output. Look for the
following lines to confirm the mapping configuration
Mapped Gmm Cause code for MAP cause Unknown Subscriber
: <gmm-cause-if-configured>
MAP cause Unknown Subscriber with Diag Info Gprs Subscription Unknown
:
<gmm-cause-if-configured>
MAP cause Unknown Subscriber with Diag Info Imsi Unknown
:
<gmm-cause-if-configured>
Configuring GMM Cause Code for RAU Reject due to Context Transfer Failure
This configuration uses the existing rau-inter command in the call control profile configuration mode. There
is a new keyword configures a GMM failure cause code to be sent in a RAU Reject to the UE due to context
transfer failures.
configure
call-control-profile profile_name
rau-inter ctxt-xfer-failure failure-code fail_code
end
Notes:
• fail_code enter value from 2 to 111 to identify the TS 124.008 GMM failure cause code for the
ctxt-xfer-failure keyword.
For more information about these commands, refer to the Command Line Interface Reference.
Verifying Configuration for Context Transfer Failures
Mapping is performed in the call control profile.
Run the show call-control-profile full name profile_name command and review the output. Look for the
following lines to confirm the mapping configuration
RAU Inter- Failure Code For Peer Sgsn Address Resolution
RAU Inter- Failure Code For Context Transfer
: <gmm-cause>
: <gmm-cause>
Configuring SM Cause Codes
The following procedures illustrates the commands used to configure SM cause codes to override the default
cause codes sent in Deactivate PDP Request due to GTPC path failure. It is up to the person entering the
configuration to determine which of the 4 cause codes should be the new cause code.
configure
call-control-profile profile_name
local-cause-code-mapping path-failure sm-cause-code { insufficient-resources | network-failure |
reactivation-requested | regular-deactivation }
end
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Verifying Configuration for SM Cause Codes
Verifying Configuration for SM Cause Codes
Mapping is performed in the call control profile.
Run the show call-control-profile full name profile_name command and review the output. Look for the
following lines to confirm the mapping configuration
Mapped SM Cause Code For Path Failure
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: <sm-cause>
CHAPTER
12
Direct Tunnel for 3G Networks
This chapter briefly describes the 3G UMTS direct tunnel (DT) feature, indicates how it is implemented on
various systems on a per call basis, and provides feature configuration procedures.
Products supporting direct tunnel include:
• 3G devices (per 3GPP TS 23.919 v8.0.0):
• the Serving GPRS Support Node (SGSN)
• the Gateway GPRS Support Node (GGSN)
Important
Direct tunnel is a licensed Cisco feature. A separate feature license is required for configuration. Contact
your Cisco account representative for detailed information on specific licensing requirements. For
information on installing and verifying licenses, refer to the Managing License Keys section of the Software
Management Operations chapter in the System Administration Guide.
The SGSN determines if setup of a direct tunnel is allowed or disallowed. Currently, the SGSN is the only
product that provide configuration commands for this feature. All other products that support direct tunnel
do so by default.
• Direct Tunnel Feature Overview, page 201
• Direct Tunnel Configuration, page 205
Direct Tunnel Feature Overview
The direct tunnel architecture allows the establishment of a direct user plane (GTP-U) tunnel between the
radio access network equipment (RNC) and a GGSN.
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Direct Tunnel Feature Overview
Once a direct tunnel is established, the SGSN continues to handle the control plane (RANAP/GTP-C) signaling
and retains the responsibility of making the decision to establish direct tunnel at PDP context activation.
Figure 23: GTP-U Direct Tunneling
A direct tunnel improves the user experience (for example, expedites web page delivery, reduces round trip
delay for conversational services) by eliminating switching latency from the user plane. An additional advantage,
direct tunnel functionality implements optimization to improve the usage of user plane resources (and hardware)
by removing the requirement from the SGSN to handle the user plane processing.
A direct tunnel is achieved upon PDP context activation in the following ways:
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Direct Tunnel Feature Overview
• Gn/Gp Interface towards GGSN: The SGSN establishes a user plane (GTP-U) tunnel directly between
the RNC and the GGSN, using an Updated PDP Context Request toward the GGSN or the GGSN service
of a collocated GGSN/P-GW.
Figure 24: Direct Tunneling - 3G Network
• Gn/Gp Interface towards P-GW When Gn/Gp interworking with pre-release 8 (3GPP) SGSNs is
enabled, the GGSN service on the P-GW supports direct tunnel functionality. The SGSN establishes a
user plane (GTP-U) tunnel directly between the RNC and the collocated PGW, using an Update PDP
Context Message toward the GGSN/P-GW.
A major consequence of deploying a direct tunnel is that it produces a significant increase in control plane
load on both the SGSN and GGSN components of the packet core. Hence, deployment requires highly scalable
GGSNs since the volume and frequency of Update PDP Context messages to the GGSN will increase
substantially. The SGSN platform capabilities ensure control plane capacity will not be a limiting factor with
direct tunnel deployment.
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Direct Tunnel Feature Overview
The following figure illustrates the logic used within the SGSN to determine if a direct tunnel will be setup.
Figure 25: Direct Tunneling - Establishment Logic
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Direct Tunnel Configuration
The following configurations are provided in this section:
• Configuring Direct Tunnel Support on the SGSN, on page 205
The SGSN direct tunnel functionality is enabled within an operator policy configuration. One aspect of an
operator policy is to allow or disallow the setup of direct GTP-U tunnels. If no operator policies are configured,
the system looks at the settings in the system operator policy named default.
By default, direct tunnel support is
• disallowed on the SGSN
• allowed on the GGSN/P-GW
Important
If direct tunnel is allowed in the default operator policy, then any incoming call that does not have an
applicable operator policy configured will have direct tunnel allowed.
For more information about operator policies and configuration details, refer to Operator Policy.
Configuring Direct Tunnel Support on the SGSN
The following is a high-level view of the steps, and the associated configuration examples, to configure the
SGSN to setup a direct tunnel.
Before beginning any of the following procedures, you must have completed (1) the basic service configuration
for the SGSN, as described in the Cisco ASR Serving GPRS Support Node Administration Guide, and (2) the
creation and configuration of a valid operator policy, as described in the Operator Policy chapter in this guide.
Step 1
Step 2
Step 3
Step 4
Step 5
Configure the SGSN to setup GTP-U direct tunnel between an RNC and an access gateway by applying the example
configuration presented in the Enabling Setup of GTP-U Direct Tunnels, on page 206.
Configure the SGSN to allow GTP-U direct tunnels to an access gateway, for a call filtered on the basis of the APN, by
applying the example configuration presented in the Enabling Direct Tunnel per APN , on page 207.
Important
It is only necessary to complete either step 2 or step 3 as a direct tunnel can not be setup on the basis of call
filtering matched with both an APN profile and an IMEI profile.
Configure the SGSN to allow GTP-U direct tunnels to a GGSN, for a call filtered on the basis of the IMEI, by applying
the example configuration presented in the Enabling Direct Tunnel per IMEI , on page 207.
Configure the SGSN to allow GTP-U direct tunnel setup from a specific RNC by applying the example configuration
presented in the Enabling Direct Tunnel to Specific RNCs, on page 208.
(Optional) Configure the SGSN to disallow direct tunnel setup to a single GGSN that has been configured to allow it in
the APN profile. This command allows the operator to restrict use of a GGSN for any reason, such as load balancing.
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Configuring Direct Tunnel Support on the SGSN
Step 6
Refer to the direct-tunnel-disabled-ggsn command in the SGTP Service Configuration Mode chapter of the Command
Line Interface Reference.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide and the Command Line Interface Reference.
Check that your configuration changes have been saved by using the sample configuration found in the Verifying the
SGSN Direct Tunnel Configuration, on page 209.
Step 7
Enabling Setup of GTP-U Direct Tunnels
The SGSN determines whether a direct tunnel can be setup and by default the SGSN doesn't support direct
tunnel.
Example Configuration
Enabling direct tunnel setup on an SGSN is done by configuring direct tunnel support in a call-control profile.
config
call-control-profile policy_name
direct-tunnel attempt-when-permitted [ to-ggsn | to-sgw ]
end
Notes:
• A call-control profile must have been previously created, configured, and associated with a previously
created, configured, and valid operator policy. For information about operator policy
creation/configuration, refer to the Operator Policy chapter in this guide.
• Beginning with Release 19.3.5, to-ggsn and to-sgw options have been added to the direct-tunnel
command to enable the operator to select the interface the SGSN will use for its direct tunnel. For a
collocated Gn/GP-SGSN and an S4-SGSN,
• Use the keyword attempt-when-permitted without a filter to enable both interface types: GTP-U
towards the GGSN and S12 towards the SGW.
• Use the keyword attempt-when-permitted with the to-ggsn keyword filter to enable only the
GTP-U interface between the RNC and the GGSN.
• Use the keyword attempt-when-permitted with the to-sgw keyword filter to enable only the S4's
S12 interface between the RNC and the SGW.
• To remove the direct tunnel settings from the configuration, use the following command: direct-tunnel
attempt-when-permitted [ to-ggsn | to-sgw ]
• Direct tunnel is allowed on the SGSN but will only setup if allowed on both the destination node and
the RNC.
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Configuring Direct Tunnel Support on the SGSN
Enabling Direct Tunnel per APN
In each operator policy, APN profiles are configured to connect to one or more GGSNs and to control the
direct tunnel access to that GGSN based on call filtering by APN. Multiple APN profiles can be configured
per operator policy.
By default, APN-based direct tunnel functionality is allowed so any existing direct tunnel configuration must
be removed to return to default and to ensure that the setup has not been restricted.
Example Configuration
The following is an example of the commands used to ensure that direct tunneling, to a GGSN(s) identified
in the APN profile, is enabled:
config
apn-profile profile_name
remove direct tunnel
end
Notes:
• An APN profile must have been previously created, configured, and associated with a previously created,
configured, and valid operator policy. For information about operator policy creation/configuration,
refer to the Operator Policy chapter in this guide.
• Direct tunnel is now allowed for the APN but will only setup if also allowed on the RNC.
Enabling Direct Tunnel per IMEI
Some operator policy filtering of calls is done on the basis of international mobile equipment identity (IMEI)
so the direct tunnel setup may rely upon the feature configuration in the IMEI profile.
The IMEI profile basis its permissions for direct tunnel on the RNC configuration associated with the IuPS
service.
By default, direct tunnel functionality is enabled for all RNCs.
Example Configuration
The following is an example of the commands used to enable direct tunneling in the IMEI profile:
config
imei-profile profile_name
direct-tunnel check-iups-service
end
Notes:
• An IMEI profile must have been previously created, configured, and associated with a previously created,
configured, and valid operator policy. For information about operator policy creation/configuration,
refer to the Operator Policy chapter in this guide.
• Direct tunnel is now allowed for calls within the IMEI range associated with the IMEI profile but a direct
tunnel will only setup if also allowed on the RNC.
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Configuring Direct Tunnel Support on the SGSN
Enabling Direct Tunnel to Specific RNCs
SGSN access to radio access controllers (RNCs) is configured in the IuPS service.
Each IuPS service can include multiple RNC configurations that determine communications and features
depending on the RNC.
By default, direct tunnel functionality is enabled for all RNCs.
Example Configuration
The following is an example of the commands used to ensure that restrictive configuration is removed and
direct tunnel for the RNC is enabled:
config
context ctx_name
iups-service service_name
rnc id rnc_id
default direct-tunnel
end
Notes:
• An IuPS service must have been previously created, and configured.
• An RNC configuration must have been previously created within an IuPS service configuration.
• Command details for configuration can be found in the Command Line Interface Reference.
Restricting Direct Tunnels
By default, GGSNs and RNCs are assumed to be capable of direct tunneling. The SGSN's direct tunnel
functionality can be fine tuned to:
Disable direct tunneling for a specified GGSN(s). GGSNs are identified by their IP address, either IPv4 or
IPv6. The command listed below can be repeated to disable direct tunneling for multiple GGSNs, thereby
creating a 'disabled GGSN' list. Checking for a GGSN that is direct-tunnel-disabled is actually the last step
in the PDP Activation procedure.
config
context context_name
sgtp-service service_name
direct-tunnel-disabled-ggsn ip_address
end
Restrict direct tunneling for an entire APN. The following configuration scenario prohibits direct tunneling
setup to a GGSN for an entire APN - the APN associated with the profile.
config
apn-profile profile_name
direct-tunnel not-permitted-by-ggsn
end
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Configuring Direct Tunnel Support on the SGSN
Restrict direct tunneling by a specific RNC. The following configuration scenario restricts the SGSN from
attempting to setup a direct tunnel when a call originates from a specific RNC.
config
context context_name
iups-service service_name
rnc id rnc_id
direct-tunnel not-permitted-by-rnc
end
Verifying the SGSN Direct Tunnel Configuration
Enabling the setup of a GTP-U direct tunnel on the SGSN is not a straight forward task. It is controlled by an
operator policy with related configuration in multiple components. Each of these component configurations
must be checked to ensure that the direct tunnel configuration has been completed. You need to begin with
the operator policy itself.
Verifying the Operator Policy Configuration
For the feature to be enabled, it must be allowed in the call-control profile, and the call-control profile must
be associated with an operator policy. As well, either an APN profile or an IMEI profile must have been
created/configured and associated with the same operator policy. Use the following command to display and
verify the operator policy and the association of the required profiles:
show operator-policy full name policy_name
The output of this command displays profiles associated with the operator policy. The output also includes
some values just as illustrative examples:
[local]asr5x00 show operator-policy full name oppolicy1
Operator Policy Name = oppolicy1
Call Control Profile Name
: ccprofile1
Validity
: Valid
IMEI Range 99999999999990 to 99999999999995
IMEI Profile Name
: imeiprofile1
Validity
: Invalid
APN NI homers1
APN Profile Name
: apnprofile1
Validity
: Valid
APN NI visitors2
APN Profile Name
: apnprofile2
Validity
: Invalid
Notes:
• Validity refers to the status of the profile. Valid indicates that profile has been created and associated
with the policy. Invalid means only the name of the profile has been associated with the policy.
• The operator policy itself will only be valid if one or more IMSI ranges have been associated with it refer to the Operator Policy chapter, in this guide, for details.
Verifying the Call-Control Profile Configuration
Use the following command to display and verify the direct tunnel configuration for the call-control profiles:
show call-control-profile full name profile_name
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Configuring Direct Tunnel Support on the SGSN
The output of this command displays all of the configuration, including direct tunnel for the specified
call-control profile.
Call Control Profile Name =
...
Re-Authentication
Direct Tunnel
GTPU Fast Path
...
ccprofile1
: Disabled
: Not Restricted
: Disabled
Verifying the APN Profile Configuration
Use the following command to display and verify the direct tunnel configuration in the APN profile:
show apn-profile full name <profile_name>
The output of this command displays all of the configuration, including direct tunnel for the specified APN
profile.
Call Control Profile Name = apnprofile1
...
IP Source Validation
Direct Tunnel
Service Restriction for Access Type > UMTS
...
: Disabled
: Not Restricted
: Disabled
Verifying the IMEI Profile Configuration
Use the following command to display and verify the direct tunnel configuration in the IMEI profile:
show imei-profile full name <profile_name>
The output of this command displays all of the configuration, including direct tunnel for the specified IMEI
profile.
IMEI Profile Name =
Black List
GGSN Selection
Direct Tunnel
imeiprofile1
: Disabled
: Disabled
: Enabled
Verifying the RNC Configuration
Use the following command to display and verify the direct tunnel configuration in the RNC configuration:
show iups-service name service_name
The output of this command displays all of the configuration, including direct tunnel for the specified IuPS
service.
IService name
...
Available RNC:
Rnc-Id
Direct Tunnel
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: iups1
: 1
: Not Restricted
CHAPTER
13
Direct Tunnel for 4G (LTE) Networks
This chapter briefly describes support for direct tunnel (DT) functionality over an S12 interface for a 4G
(LTE) network to optimize packet data traffic.
Cisco LTE devices (per 3GPP TS 23.401 v8.3.0) supporting direct tunnel include:
• Serving GPRS Support Node (S4-SGSN)
• Serving Gateway (S-GW)
• PDN Gateway (P-GW)
Important
Direct Tunnel is a licensed Cisco feature. A separate feature license is required for configuration. Contact
your Cisco account representative for detailed information on specific licensing requirements. For
information on installing and verifying licenses, refer to the Managing License Keys section of the Software
Management Operations chapter in the System Administration Guide.
The following sections are included in this chapter:
• Direct Tunnel for 4G Networks - Feature Description , page 211
• How It Works, page 214
• Configuring Support for Direct Tunnel, page 242
• Monitoring and Troubleshooting Direct Tunnel, page 245
Direct Tunnel for 4G Networks - Feature Description
The amount of user plane data will increase significantly during the next few years because of High Speed
Packet Access (HSPA) and IP Multimedia Subsystem technologies. Direct tunneling of user plane data between
the RNC and the S-GW can be employed to scale UMTS system architecture to support higher traffic rates.
Direct Tunnel (DT) offers a solution that optimizes core architecture without impact to UEs and can be
deployed independently of the LTE/SAE architecture.
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Direct Tunnel for 4G Networks - Feature Description
Important
Direct tunnel is a licensed Cisco feature. A separate feature license is required for configuration. Contact
your Cisco account representative for detailed information on specific licensing requirements. For
information on installing and verifying licenses, refer to the Managing License Keys section of the Software
Management Operations chapter in the System Administration Guide.
Important
Establishment of a direct tunnel is controlled by the SGSN; for 4G networks this requires an S4
license-enabled SGSN setup and configured as an S4-SGSN.
Once a direct tunnel is established, the S4-SGSN/S-GW continues to handle the control plane (RANAP/GTP-C)
signaling and retains the responsibility of making the decision to establish direct tunnel at PDP context
activation.
Figure 26: GTP-U Direct Tunneling
A direct tunnel improves the user experience (for example, expedites web page delivery, reduces round trip
delay for conversational services) by eliminating switching latency from the user plane. An additional advantage,
direct tunnel functionality implements optimization to improve the usage of user plane resources (and hardware)
by removing the requirement from the S4-SGSN/S-GW to handle the user plane processing.
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Direct Tunnel for 4G Networks - Feature Description
A direct tunnel is achieved upon PDP context activation when the S4-SGSN establishes a user plane tunnel
(GTP-U tunnel) directly between the RNC and the S-GW over an S12 interface, using a Create Bearer Response
or Modify Bearer Request towards the S-GW.
Figure 27: Direct Tunneling - LTE Network, S12 Interface
A major consequence of deploying a direct tunnel is that it produces a significant increase in control plane
load on both the SGSN/S-GW and GGSN/P-GW components of the packet core. Hence, deployment requires
highly scalable GGSNs/P-GWs since the volume and frequency of Update PDP Context messages to the
GGSN/P-GW will increase substantially. The SGSN/S-GW platform capabilities ensure control plane capacity
will not be a limiting factor with direct tunnel deployment.
S4-SGSN supports establishment of a GTP-U direct tunnel between an RNC and the S-GW under the scenarios
listed below:
• Primary PDP activation
• Secondary PDP activation
• Service Request Procedure
• Intra SGSN Routing Area Update without S-GW change
• Intra SGSN Routing Area Update with S-GW change
• Intra SGSN SRNS relocation without S-GW change
• Intra SGSN SRNS relocation with S-GW change
• New SGSN SRNS relocation with S-GW change
• New SGSN SRNS relocation without S-GW relocation
• E-UTRAN-to-UTRAN Iu mode IRAT handover with application of S12U FTEID for Indirect Data
Forwarding Tunnels as well
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How It Works
• UTRAN-to-E-UTRAN Iu mode IRAT handover with application of S12U FTEID for Indirect Data
Forwarding Tunnels as well
• Network Initiated PDP Activation
Scenarios that vary at S4-SGSN when direct tunneling is enabled, as compared to DT on a 2G or 3G SGSN
using the Gn interface, include:
• RAB Release
• Iu Release
• Error Indication from RNC
• Downlink Data Notification from S-GW
• Downlink Data Error Indication from S-GW
• MS Initiated PDP Modification
• P-GW Initiated PDP Modification while the UE is IDLE
• HLR/HSS Initiated PDP Modification
• Session Recovery with Direct Tunnel
The above scenarios exhibit procedural differences in S4-SGSN when a direct tunnel is established.
How It Works
DT functionality enables direct user plane tunnel between RNC and SGW within the PS domain. With direct
tunneling the S4-SGSN provides the RNC with the TEID and user plane address of the S-GW, and also
provides the S-GW with the TEID and user plane address of the RNC.
The SGSN handles the control plane signaling and makes the decision when to establish the direct tunnel
between RNC and S-GW, or use two tunnels for this purpose (based on configuration).
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DT Establishment Logic
DT Establishment Logic
The following figure illustrates the logic used within the S4-SGSN/S-GW to determine if a direct tunnel will
be setup.
Figure 28: Direct Tunneling - Establishment Logic
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Establishment of Direct Tunnel
Establishment of Direct Tunnel
The S4-SGSN uses the S12 interface for DT.
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Establishment of Direct Tunnel
Direct Tunnel Activation for Primary PDP Context
For the PDP Context Activation procedure this solution uses new information elements (IEs) for the GPRS
Tunnelling Protocol v2 (GTPv2) as defined in TS 29.274. SGSN provides the user plane addresses for RNC
and S-GW as S12U FTEIDs as illustrated in the figure below.
The sequence for establishing a direct tunnel between the RNC and S-GW during PDP activation is as follows:
• SGSN sends a Create Session Request to the S-GW with the indication flag DTF (direct tunnel flag) bit
set
• In its Create Session Response, the S-GW sends the SGSN an S12U FTEID (Fully Qualified Tunnel
Endpoint Identifier).
• The SGSN forwards the S-GW S12U to the RNC during the RAB Assignment Request.
• In its RAB Assignment Response, the RNC sends the SGSN its transport address and Tunnel Endpoint
ID (TEID).
• The SGSN forward the RNC S12 U FTEID o the S-GW via a Modify Bearer Request.
Figure 29: Primary PDP Activation with Direct Tunnel
Direct Tunnel Activation for UE Initiated Secondary PDP Context
The following is the general sequence for establishing a direct tunnel for a Secondary PDP Context Activation:
• The SGSN sends a Bearer Resource Command to the S-GW with no flags set. (S-GW already knows
Direct Tunnel is enabled for primary.)
• The S-GW sends a Create Bearer Response that includes the S12U FTEID to the SGSN.
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• The SGSN forwards the S-GW S12U to RNC via a RAB Assignment Request.
• In its RAB Assignment Response, the RNC sends its transport address and TEID to the SGSN.
• The SGSN forwards the S12U TEID received from the RNC to the S-GW via a Create Bearer Response.
Figure 30: Secondary PDP Activation with Direct Tunnel
RAB Release with Direct Tunnel
If the SGSN receives a RAB Release Request from the RNC for bearer contexts activated with Direct Tunnel,
it sends a Release Access Bearer Request to the S-GW.
Upon receiving the Release Access Bearer Request, the S-GW removes the S12 U RNC FTEID. If any
downlink data appears, the S-GW sends a Downlink Data Notification because it does not have a user plane
FTEID with which to forward data.
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Bearers with a streaming or conversational class will not be included in the Release Access Bearer Request
because these bearers should be deactivated. However, S4-SGSN currently does not support deactivation of
streaming/conversational bearers upon RAB release.
Figure 31: RAB Release Procedure with Direct Tunnel
Important
Operators should not use conversational or streaming class bearers in S4-SGSN.
Iu Release with Direct Tunnel
If the SGSN receives an Iu Release and bearers are activated with direct tunneling, it sends a Release Access
Bearer Request to the S-GW.
Bearers with a streaming or conversational class will not be included in the Release Access Bearer Request
because these bearers should be deactivated. However, S4-SGSN currently does not support deactivation of
streaming or conversational bearers upon Iu release.
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Important
Operators should not use conversational or streaming class bearers in S4-SGSN.
Figure 32: Iu Release Procedure with Direct Tunnel
Service Request with Direct Tunnel
When a UE is Idle and wants to establish a data or signaling connection, it sends a Service Request for data.
Alternatively a UE can also send a Service Request to the SGSN when it is paged by the SGSN.
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Upon receiving a Service Request for data, the SGSN establishes RABs and sends a Modify Bearer Request
to the S-GW with the 12U FTEID received from the RNC.
Figure 33: Service Request Procedure with Direct Tunnel
Downlink Data Notification with Direct Tunnel when UE in Connected State
When RABs are released (but UE retains an Iu connection with the SGSN), the SGSN notifies the S-GW to
release the RNC side TEIDs via a Release Access Bearer Request.
If the S-GW receives any downlink GTPU data from the P-GW after receiving the Release Access Bearer
Request, it knows neither the RNC TEID nor SGSN user plane TEID to which to forward the data. So it
signals the SGSN to establish the RABs. This signaling message is a Downlink Data Notification message
from the S-GW.
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If the Downlink Data Notification is received from the S-GW, all of the missing RABs are established and a
Modify Bearer Request is sent to the S-GW with the RNC S12U FTEID
Figure 34: Downlink Data Notification with Direct Tunnel
Downlink Data Notification with Direct Tunnel when UE in Idle State
When an Iu is released the UE goes IDLE. The SGSN informs the S-GW to release the RNC side TEIDs by
sending a Release Access Bearer Request. After this point if the S-GW receives any downlink GTPU data
from the P-GW, it knows neither the RNC TEID nor SGSN user plane TEID to which to forward the data.
If the S-GW receives any downlink GTPU data after receiving the Release Access Bearer Request, it knows
neither the RNC TEID nor SGSN user plane TEID to which to forward the data. So it signals the SGSN to
establish the RABs. This signaling message is a Downlink Data Notification from the S-GW. If a Downlink
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Data Notification is received from S-GW when the UE is idle, the SGSN pages the UE before establishing
the RABs. The SGSN sends a Modify Bearer Request to the S-GW with the RNC S12U FTEID.
Figure 35: Downlink Data Notification when UE in Idle State
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Intra SGSN Routing Area Update without SGW Change
For a Routing Area Update without an S-GW change with Direct Tunnel, the SGSN sends a Modify Bearer
Request to the S-GW with the RNC FTEID. The SGSN will establish RABs with the target RNC only if the
RABs were present with the source RNC.
Figure 36: Routing Area Update Procedure without SGW Change
The table below includes detailed behaviors for a Routing Area Update without S-GW change.
Table 14: Routing Area Update without S-GW Change Behavior Table
Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
Intra RAU
Not
No RAB Supported
Present
Intra RAU
Present No RAB Supported
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Status
Change
SGSN Action
No
Supported
No
No RAB
establishment with
new RNC. No
Modify Bearer
Request to S-GW
No
Supported
No
No RAB
establishment with
new RNC. No
Modify Bearer
Request to S-GW
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Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
NEW RNC DT S-GW
Status
Change
SGSN Action
Intra RAU
Present Some
RABs
Do not
care
Supported
No
Only the present
RABs are
established. MBR
sent to S-GW with
the bearers with
RABs that are be
modified and the
rest released. The
bearers without
RABs will be
deactivated post
RAU. If PLMN
changed then MBR
will carry the new
PLMN ID.
Intra RAU
Not
No RAB Supported
Present
Yes
Supported
No
No RAB
establishment with
new RNC. MBR is
sent with only
PLMN change.
Bearer Context will
not carry any TEID.
Intra RAU
Present No RAB Supported
Yes
Supported
No
Same as above.
Intra RAU
Not
No RAB Not
Present
Supported
No
Supported
No
No RAB
establishment with
new RNC. Modify
Bearer Request to
S-GW with DTF set
and no user FTEID.
Intra RAU
Present No RAB Not
Supported
No
Supported
No
Same as above.
Supported
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Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
NEW RNC DT S-GW
Status
Change
SGSN Action
Intra RAU
Present Some
RABs
Do not
care
Supported
No
Only the present
RABs are
established. MBR
sent to S-GW with
the bearers with
RABs to be
modified and the
rest to be released.
The bearers without
RABs will be
deactivated post
RAU. If PLMN
changed then MBR
will carry the new
PLMN ID.Modify
Bearer.
Intra RAU
Not
No RAB Not
Present
Supported
Yes
Supported
No
No RAB
establishment with
new RNC. MBR is
sent with only
PLMN change.
SGSN will page /
Service req /
establish RABs
when a downlink
data notification is
received.
Intra RAU
Present No RAB Not
Supported
Yes
Supported
No
Same as above.
Not
Supported
Intra RAU: New RNC does not support Direct Tunnel. No SGW relocation
Intra RAU
Not
No RAB Supported
Present
Do not
care
Not
Supported
No
No RAB
establishment with
new RNC. SGSN
sends Modify
Bearer Request to
S-GW with S4U
TEID. If there is
change in PLMN
ID, then new PLMN
ID will be carried.
Intra RAU
Present No RAB Supported
Do not
care
No
Supported
No
Same as above.
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Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
Intra RAU
Present Some
RABs
Supported
Do not
care
NEW RNC DT S-GW
Status
Change
SGSN Action
Not
supported
Only the present
RABs are
established. MBR
sent to S-GW with
all bearers having
S4U TEID. If there
is change in PLMN
ID, the new PLMN
ID will be carried.
No
Routing Area Update with S-GW Change
In a Routing Area Update with an S-GW change, the SGSN sends a Create Session Request with DTF flag
set and no user plane FTEID. In its Create Session Response,. the S-GW sends an S12U FTEID which is
forwarded to the RNC via a RAB Assignment Request.
The SGSN sends the RNC FTEID received in the RAB Assignment Response to the S-GW in a Modify Bearer
Request. There are many scenarios to consider during Intra SGSN RAU.
Figure 37: Routing Area Update Procedure with SGW Change
The table below includes detailed behaviors for a Routing Area Update with S-GW change.
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Table 15: Routing Area Update with S-GW Change Behavior Table
Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
NEW RNC DT S-GW
Status
Change
SGSN Action
Intra RAU: Both RNCs support Direct Tunnel. SGW relocation
Intra RAU
Not
No RAB Supported
Present
Do not
care
Supported
Yes
Send CSR request to
new S-GW with
DTF flag but no
S4U / S12U FTEID.
S-GW will send its
S12U TEID that
SGSN stores as part
of DP's remote
TEID. SGSN will
not initiate any
MBR request to
S-GW since no
RABs are
established with
new RNC. If S-GW
subsequently gets
downlink data,
SGSN will get DDN
and establish RABs
and send MBR.
Intra RAU
Present No RAB Supported
Do not
care
Supported
Yes
Same as above.
Intra RAU
Present Some
RABs
Do not
care
Supported
Yes
Send CSR request to
new S-GW with
DTF flag but no
S4U / S12U FTEID.
S-GW sends its
S12U TEID. RABs
that are present will
be established with
new RNC. MBR
will be initiated only
with those RABs
that are present rest
of bearers to be
removed.
Supported
Intra RAU: Old RNC does not support Direct Tunnel. SGW relocation
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Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
NEW RNC DT S-GW
Status
Change
SGSN Action
Intra RAU
Not
No RAB Not
Present
Supported
Do not
care
Supported
Yes
Send CSR request to
new S-GW with
DTF flag but no
S4U / S12U FTEID.
S-GW sends its
S12U TEID that
SGSN stores as part
of our DP's remote
TEID. SGSN will
not initiate any
MBR request to
S-GW since no
RABs are
established with
new RNC. If S-GW
subsequently gets
downlink data,
SGSN gets DDN
and establishes
RABs and sends
MBR.
Intra RAU
present No RAB Not
Supported
Do not
care
Supported
Yes
Same as above.
Intra RAU
Present Some
RABs
Do not
care
Supported
Yes
Send CSR request to
new S-GW with
DTF flag but no
S4U / S12U FTEID.
S-GW sends its
S12U TEID. RABs
that are present will
be established with
new RNC and MBR
will be initiated only
with those RABs
that are present and
the rest as bearers to
be removed.
Not
SUpported
Intra RAU: New RNC does not support Direct Tunnel. SGW relocation
Intra RAU
Not
No RAB Supported
Present
Do not
care
Not
Supported
Yes
CSR request
without DTF flag
and with S4U
FTEID.
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Scenario
Old
RNC
Status
Old RNC Old RNC DT PLMN
RAB
Status
Change
Intra RAU
Present No RAB Supported
Intra RAU
Present Some
rABs
Supported
NEW RNC DT S-GW
Status
Change
SGSN Action
Do not
care
Not
Supported
Yes
CSR request
without DTF flag
and with S4U
FTEID.
Do not
care
Not
Supported
Yes
CSR request
without DTF flag
and with S4U
FTEID. No
deactivation of
PDPs.
Intra SRNS with S-GW Change
In Intra SRNS (Serving Radio Network Subsystem) with S-GW change, the SGSN sends a Create Session
Request with DTF flag set and no user plane FTEID. The Create Session Response from the new S-GW
contains the SGW S12U FTEID which the SGSN forwards to the Target RNC in a Relocation Request.
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The SGSN sends the RNC S12U FTEID to the new S-GW in a Modify Bearer Request.
Figure 38: Intra SRNS with S-GW Change
The table below includes detailed behaviors for intra SRNS scenarios.
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Intra SRNS without S-GW Change
In Intra SRNS without S-GW change, a Relocation Request is sent with SGW S12U FTEID. The RNC S12U
FTEID received is forwarded to the S-GW in a Modify Bearer Request.
Figure 39: Intra SRNS without S-GW Change
The table below includes detailed behaviors for intra SRNS scenarios.
Table 16: Intra SRNS Behaviors
Old RNC DT Status
New RNC DT
Status
S-GW
Relocation
Behavior
Supported
Supported
No
Relocation Request to Target RNC is sent with S-GW
S12 U FTEID. Modify Bearer Request to S-GW is
sent with RNC S12 U FTEID.
Supported
Not Supported No
Relocation Request to Target RNC is sent with SGSN
S4 U FTEID. Modify Bearer Request to S-GW is sent
with SGSN S4 U FTEID
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Old RNC DT Status
New RNC DT
Status
S-GW
Relocation
Behavior
Not Supported
Supported
No
Relocation Request to Target RNC is sent with S-GW
S12U FTEID. Modify Bearer Request to S-GW is sent
with RNC S12 U FTEID.
Not Supported
Supported
Yes
Create Session Request to new S-GW is sent with DTF
flag set and no user plane FTEID. Even if S-GW sent
S4U FTEID in CSR Response SGSN internally treats
that as an S12U FTEID and continues the relocation.
Relocation Request to Target RNC is sent with S12 U
FTEID received in Create Session Response. Modify
Bearer Request to new S-GW is sent with RNC S12U
FTEID
Supported
Not Supported Yes
Create Session Request to new SGW is sent with S4
U FTEID. Relocation Request to Target RNC is sent
with SGSN U FTEID.Modify Bearer Request is sent
with SGSN S4U FTEID.
Supported
Supported
SGSN sends a Create Session Request to new SGW
with DTF flag set and no user plane FTEID.Even if
S-GW sent S4U FTEID in CSR Response, SGSN will
internally treat that as S12U FTEID and continue the
relocation. Relocation Request to the Target RNC is
sent with the S12 U FTEID received in the Create
Session Response. Modify Bearer Request to new
S-GW is sent with RNC U FTEID.
Yes
New SRNS with S-GW Change and Direct Data Transfer
The new SGSN sends a Create Session Request with DTF flag set and no user plane FTEID to the new S-GW.
The new SGSN sends the SGW S12U FTEID received in the Create Session Response in Relocation Request
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to the Target RNC. The new SGSN sends the RNC S12U FTEID received in a Relocation Request Ack to
the new S-GW in a Modify Bearer Request.
Figure 40: New SRNS with S-GW Change with Data Transfer
The table below includes detailed behaviors for New SRNS scenarios.
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New SRNS with S-GW Change and Indirect Data Transfer
Indirect Data Transfer (IDFT) during a new SGSN SRNS happens during E-UTRAN-to-UTRAN connected
mode IRAT handover. See the figure below for a detailed call flow.
Figure 41: New SRNS with S-GW Change and Indirect Data Transfer
The table below includes detailed behaviors for New SRNS scenarios.
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Table 17: New SRNS Behaviors
Target RNC DT
Status
Direct
Forwarding
S-GW
Relocation
Behavior
Supported
No
No
Relocation Request with SGW S12U FTEID received
in Forward Relocation Request. SGSN includes RNC
U FTEID in Forward Relocation Response. RNC U
FTEID is also sent in Modify Bearer Request with
DTF flag set.
Supported
Yes
No
Relocation Request with SGW S12U FTEID received
in Forward Relocation Request. In Forward Relocation
Response RNC U FTEID is included. And in Modify
Bearer Request RNC U FTEID is sent and DTF flag
is set.
Supported
No
Yes
Create Session Request with DTF flag set and no user
plane FTEID. Relocation Request is sent is SGW S12U
FTEID received in Create Session Response. Even if
SGW sent S4U FTEID in CSR Response we will
internally treat that as S12U FTEID and continue the
relocation. Create Indirect Data Forwarding Tunnel
Request is sent with RNC FTEID received in
Relocation Request Acknowledge.In Forward
Relocation Response SGW DL U FTEID received in
Create IDFT response is sent. Modify Bearer Request
is send with DTF set and RNC U FTEID.
Supported
Yes
Yes
Create Session Request with DTF flag set and no user
plane FTEID. Relocation Request is sent with SGW
S12U FTEID received in Create Session Response.
Even if SGW sent S4U FTEID in CSR Response we
will internally treat that as S12U FTEID and continue
the relocation. In Forward Relocation Response RNC
FTEID is sent and Modify Bearer Request is sent with
DTF flag set and RNC U FTEID
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Old SRNS with Direct Data Transfer
This scenario includes SRNS relocation between two SGSNs and hence IDFT is not applicable. Data will be
forwarded between the source and target RNCs directly. Forward Relocation Request is sent with S12U
FTEID.
Figure 42: Old SRNS with Direct Data Transfer
The table below includes detailed behaviors for Old SRNS.
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Old SRNS with Indirect Data Transfer
Indirect Data Transfer (IDFT) during Old SGSN SRNS happens during UTRAN-to-E-UTRAN connected
mode IRAT handover. A Forward Relocation Request is sent with SGW S12U FTEID.
Figure 43: Old SRNS with Indirect Data Transfer 4
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Table 18: Old SRNS Behaviors
Source RNC DT
Status
Direct
Forwarding
S-GW
Relocation
Behavior
Supported
No
No
Forward Relocation Request is send with SGW S12
U FTEID. If peer is MME, IDFT is applied. Then a
Create Indirect Data Forwarding Tunnel Request is
sent with User plane FTEID received in the Forward
Relocation Response. This will be the eNB user plane
FTEID. The SGW DL forwarding user plane FTEID
received in the Create Indirect Data Forwarding Tunnel
Response is sent in the Relocation Command.
Supported
Yes
No
Forward Relocation Request is sent with SGW S12 U
FTEID. The eNB / RNC user plane FTEID received
in the Forward Relocation Response is sent in the
Relocation Command.
Supported
No
Yes
Forward Relocation Request is sent with SGW S12 U
FTEID. If peer is MME, IDFT is applied. Then Create
Indirect Data Forwarding Tunnel Request is sent with
eNB User plane FTEID received in the Forward
Relocation Response. The SGW DL forwarding user
plane FTEID received in the Create Indirect Data
Forwarding Tunnel Response is sent in the Relocation
Command.
Supported
Yes
Yes
Forward Relocation Request is sent with SGW S12 U
FTEID. The eNB / RNC use plane FTEID received in
the Forward Relocation Response is sent in the
Relocation Command.
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Network Initiated Secondary PDP Context Activation
The S-GW sends a Create Bearer Request for Network Initiated Secondary PDP Context Activation with the
SGW S12U FTEID. This FTEID is sent in a RAB Assignment Request to the RNC. The RNC S12U FTEID
received in the RAB Assignment Response is sent to the S-GW in a Create Bearer Response.
Figure 44: Network Initiated Secondary PDP Context Activation 5
PGW Init Modification when UE is Idle
If UE is in IDLE state and PGW Init Modification is received, the SGSN sends the first MBR. Upon getting
PGW Init Modification in Idle State, the SGSN queues the PGW Init Modification and feeds a Downlink Data
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Limitations
Notification internally. This sets up all RABs (using old QoS) and sends a Modify Bearer Request. When the
Downlink Data Procedure is completed, the queued PGW Init Modification is processed.
Figure 45: PGW Init Modification when UE in Idle State
Limitations
During an intra RAU, intra SRNS or Service Request triggered by RAB establishment, if a few RABs fail the
Modify Bearer Request the SGSN will mark those RABs as bearers to be removed. Under current specifications,
it is not possible to send a Modify Bearer Request with a few bearers having S12U U-FTEIDs and a few
bearers not having U-FTEIDs.
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Standards Compliance
There is an ongoing CR at 3GPP to allow such Modify Bearer Requests and the S-GW should send DDN
when it gets downlink data for the bearers that did not have U-FTEIDs. If this CR is approved, the SGSN will
support (in a future release) sending a partial set of bearers with S12U FTEID and some bearers without any
U-FTEID.
Standards Compliance
The Direct Tunnel complies with the following standards:
• 3GPP TS 23.060 version 10 sec 9.2.2 General Packet Radio Service (GPRS) Service description
• 3GPP TS 29.274 v10.5.0 3GPP Evolved Packet System (EPS) Evolved General Packet Radio Service
(GPRS) Tunnelling Protocol for Control plane (GTPv2-C)
Configuring Support for Direct Tunnel
The SGSN determines if setup of a direct tunnel is allowed or disallowed. Currently, the SGSN and S-GW
are the only products that provide configuration commands for this feature. All other products that support
direct tunnel do so by default.
By default, direct tunnel support is
• disallowed on the SGSN/S-GW
• allowed on the GGSN/P-GW
The SGSN/S-GW direct tunnel functionality is enabled within an operator policy configuration. One aspect
of an operator policy is to allow or disallow the setup of direct GTP-U tunnels. If no operator policies are
configured, the system looks at the settings in the operator policy named default. If direct tunnel is allowed
in the default operator policy, then any incoming call that does not have an applicable operator policy configured
will have direct tunnel allowed. For more information about the purpose and uses of operator policies, refer
to the section Operator Policy.
Configuring Direct Tunnel on an S4-SGSN
Configuration of a GTP-U direct tunnel (DT) requires enabling DT both in a call control profile and for the
RNC.
Important
Direct tunneling must be enabled at both end points to allow direct tunneling for the MS/UE.
Enabling Setup of GTP-U Direct Tunnel
The SGSN determines whether a direct tunnel can be setup and by default the SGSN does not support direct
tunnel. The following configuration enables a GTP-U DT in a call control profile:
config
call-control-profile policy_name
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direct-tunnel attempt-when-permitted [ to-ggsn | to-sgw ]
end
Notes:
• A call-control profile must have been previously created, configured, and associated with a previously
created, configured, and valid operator policy. For information about operator policy
creation/configuration, refer to the Operator Policy chapter in this guide.
• Beginning with Release 19.3.5, to-ggsn and to-sgw options have been added to the direct-tunnel
command to enable the operator to select the interface the SGSN will use for its direct tunnel. For a
collocated Gn/GP-SGSN and an S4-SGSN,
• Use the keyword attempt-when-permitted without a filter to enable both interface types: GTP-U
towards the GGSN and S12 towards the SGW.
• Use the keyword attempt-when-permitted with the to-ggsn keyword filter to enable only the
GTP-U interface between the RNC and the GGSN.
• Use the keyword attempt-when-permitted with the to-sgw keyword filter to enable only the S4's
S12 interface between the RNC and the SGW.
• To remove the direct tunnel settings from the configuration, use the following command: direct-tunnel
attempt-when-permitted [ to-ggsn | to-sgw ]
• Direct tunnel is allowed on the SGSN but will only setup if allowed on both the destination node and
the RNC.
Enabling Direct Tunnel to RNCs
SGSN access to radio access controllers (RNCs) is configured in the IuPS service. Each IuPS service can
include multiple RNC configurations that determine communications and features depending on the RNC.
By default, DT functionality is enabled for all RNCs.
The following configuration sequence enables DT to a specific RNC that had been previously disabled for
direct tunneling:
config
context ctxt_name
iups-service service_name
rnc id rnc_id
default direct-tunnel
end
Notes:
• An IuPS service must have been previously created, and configured.
• An RNC configuration must have been previously created within an IuPS service configuration.
• Command details for configuration can be found in the Command Line Interface Reference.
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Configuring Direct Tunnel on an S4-SGSN
Restricting Direct Tunnels
The following configuration scenario prohibits the S4-SGSN to setup direct tunneling over the S12 interface
during Inter SGSN RAUs:
config
call-control-profile profile_name
rau-inter avoid-s12-direct-tunnel
end
Restrict direct tunneling by a specific RNC. The following configuration scenario restricts the SGSN from
attempting to setup a direct tunnel when a call originates from a specific RNC.
config
context context_name
iups-service service_name
rnc id rnc_id
direct-tunnel not-permitted-by-rnc
end
Verifying the Call-Control Profile Configuration
Use the following command to display and verify the direct tunnel configuration for the call-control profiles:
show call-control-profile full name <profile_name>
The output of this command displays all of the configuration, including direct tunnel for the specified
call-control profile.
Call Control Profile Name = ccprofile1
.
.
.
Re-Authentication
: Disabled
Direct Tunnel
: Not Restricted
GTPU Fast Path
: Disabled
.
.
Verifying the RNC Configuration
Use the following command to display and verify the direct tunnel configuration in the RNC configuration:
show iups-service name <service_name>
The output of this command displays all of the configuration, including direct tunnel for the specified IuPS
service.
IService name
.
.
.
Available RNC:
Rnc-Id
Direct Tunnel
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: iups1
: 1
: Not Restricted
Direct Tunnel for 4G (LTE) Networks
Configuring S12 Direct Tunnel Support on the S-GW
Configuring S12 Direct Tunnel Support on the S-GW
The example in this section configures an S12 interface supporting direct tunnel bypass of the S4 SGSN for
inter-RAT handovers.
The direct tunnel capability on the S-GW is enabled by configuring an S12 interface. The S4 SGSN is then
responsible for creating the direct tunnel by sending an FTEID in a control message to the S-GW over the
S11 interfaces. The S-GW responds with it\'s own U-FTEID providing the SGSN with the identification
information required to set up the direct tunnel over the S12 interface.
Use the following example to configure this feature:
configure
context egress_context_name -noconfirm
interface s12_interface_name
ip address s12_ipv4_address_primary
ip address s12_ipv4_address_secondary
exit
exit
port ethernet slot_number/port_number
no shutdown
bind interface s12_interface_name egress_context_name
exit
context egress_context_name -noconfirm
gtpu-service s12_gtpu_egress_service_name
bind ipv4-address s12_interface_ip_address
exit
egtp-service s12_egtp_egress_service_name
interface-type interface-sgw-egress
validation-mode default
associate gtpu-service s12_gtpu_egress_service_name
gtpc bind address s12_interface_ip_address
exit
sgw-service sgw_service_name -noconfirm
associate egress-proto gtp egress-context egress_context_name egtp-service
s12_egtp_egress_service_name
end
Notes:
• The S12 interface IP address(es) can also be specified as IPv6 addresses using the ipv6 address command.
Monitoring and Troubleshooting Direct Tunnel
show subscribers sgsn-only
The output of this command indicates whether. Direct Tunnel has been established.
show subscribers sgsn-only full all
Username: 123456789012345
Access Type: sgsn-pdp-type-ipv4
Access Tech: WCDMA UTRAN
|
Network Type: IP
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Direct Tunnel Bulk Statistics
|
NSAPI: 05
Context initiated by: MS
Direct Tunnel : Established
Context Type: Primary
show gmm-sm statistics sm-only
The output of this command indicates the number of total active PDP contexts with direct tunnels.
show gmm-sm statistics sm-only
Activate PDP Contexts:
Total Actv PDP Ctx:
3G-Actv Pdp Ctx:
Gn Interface:
S4 Interface:
Total Actv Pdp Ctx:
with Direct Tunnel:
1
1
1
2G-Avtv Pdp Ctx:
Gn Interface:
S4 Interface:
0
0
0
1
Direct Tunnel Bulk Statistics
Currently there are no bulk statistics available to monitor the number of PDP contexts with Direct Tunnel.
Bulk statistics under the EGTPC schema are applicable for both Direct Tunnel and Idle Mode Signalling
Reduction (ISR) [3G and 2G]. The following statistics track the release access bearer request and response
messages which are sent by the SGSN to the S-GW upon Iu or RAB release when either a direct tunnel or
ISR is active:
• tun-sent-relaccbearreq
• tun-sent-retransrelaccbearreq
• tun-recv-relaccbearresp
• tun-recv-relaccbearrespDiscard
• tun-recv-relaccbearrespaccept
• tun-recv-relaccbearrespdenied
The following bulkstats under EGTPC schema track Downlink Data Notification (DDN) Ack and failure
messages between the S-GW and the SGSN when either direct tunnel or ISR is active:
• tun-recv-dlinknotif
• tun-recv-dlinknotifDiscard
• tun-recv-dlinknotifNorsp
• tun-recv-retransdlinknotif
• tun-sent-dlinknotifackaccept
• tun-sent-dlinknotifackdenied
• tun-sent-dlinkdatafail
For complete descriptions of these variables, see the EGTPC Schema Statistics chapter in the Statistics and
Counters Reference.
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CHAPTER
14
GMM-SM Event Logging
With the introduction of this feature, the SGSN now supports limited use of event data records (EDRs). This
chapters details the SGSN\'s event logging feature, with the use of EDRs, which is intended to facilitate
subscriber-level troubleshooting. This feature is relevant for StarOS Release 12.0 (and higher) software
supporting SGSN services within GPRS and UMTS networks.
This chapter provides the following information:
• Feature Description, page 247
• Configuration, page 253
Feature Description
Feature Overview
At any one time, the SGSN handles a large number of mobile stations (MS). In order to efficiently troubleshoot
any issue for a single subscriber, it is necessary to know the events that have happened for that subscriber.
Prior to this event logging feature, the SGSN did not support a debugging method that was event-based per
subscriber.
The debugging framework will allow operators to troubleshoot problems related to a particular IMSI. The
event logging feature will capture procedure-level information per subscriber. Upon completing a procedure,
either successfully or unsuccessfully, the SGSN generates a procedure-summary or event report logging the
event.
The SGSN uses the event reports to generate event data record (EDR) files comprised of logged information
in comma-separated ASCII values - CSV format. The SGSN sends one ASCII formatted CSV record per line.
The CSV records are stored in a file and are optionally compressed before sending to an external server. The
storage space in the ASR5K is limited so the CSV records need to be SFTed to an external server periodically.
The transfer of the CSV record file from the SGSN and to the external server can be based on configurable
PULL or PUSH models. In case of PUSH, the time-interval can be configured at the SGSN.
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GMM-SM Event Logging
Events to be Logged
Events to be Logged
The following subscriber events will be logged:
• Attaches
• Activation of PDP Context
• Routing Area Update (RAU)
• Inter-SGSN RAU (ISRAU)
• Deactivation of PDP Context
• Detaches
• Authentications
• PDP Modifications
Event Record Fields
The EDRs include the following information in CSV format.
Important
If particular information is not relevant or is unavailable for the procedure being logged, then the field is
left blank.
Table 19: Event Record Fields for GMM/SM Event Logging
Field
Field Content
Field Information
1
header-field-1
Number from 1 to 512.
2
header-field-2
Number from 0 to 4294967295.
3
time
Format: YYYY-MMM-DD+HH:MM:SS
4
event-identity
Enumeration: Attach(0); Activate(1); LOCAL-RAU (2);
NEW-ISRAU (3); OLD-ISRAU (4); Deactivation (5); Detach
(6); Authentication (7); Modification (8).
5
result
Enumeration: Success (0); Reject (1); Aborted (2).
6
radio type
Enumeration: UTRAN (0); GERAN (1).
7
ATT type
Enumeration: GPRS-only; Comb.
8
RAU type
Enumeration: GPRS-only (0); Comb (1); Comb-IMSI-Attach(2);
Periodic (3).
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Event Record Fields
Field
Field Content
Field Information
9
intra-RAU type
Enumeration: 2G -> 3G (-); 3G -> 2G (1); 2G -> 2G [Diff Serv]
(2); 3G -> 3G [Diff Serv] (3); Local 2G (4); Local 3G (5).
10
origin-of-deactivation
Enumeration: HLR (0); GGSN (1); LOCAL (2); MS (3) .
11
cause-prot-indicator
Enumeration: GMM(0); GSM(1).
12
gmm-cause/gsm-cause
Number between 0 and 255 to identify failure cause code. Refer
to the 3GPP TS 24.008 specification, sections 10.5.5.14 (GMM
cause codes) and 10.5.6.6 (SM cause codes) for an up-to-date
listing.
13
disc-reason
Number 0 to 500 identifies Cisco proprietary detailed reason for
session failure. To see the explanation for the SGSN-only
disconnect reasons, see Cisco ASR 5000 Series Statistics and
Counters Reference.
14
RAI
Routing area identifier in the format: ddd-ddd-xxxx-xx (d =
decimal; x = hex).
15
Cell ID or SAI
One or the other, depends whether the event is generated in 3G
or 2G. An integer between 0 and 65535.
16
SAC
Service area code, an integer between 0 and 65535.
17
MSISDN
Mobile subscriber\'s ISDN number consisting of 7 to 16 digits.
18
IMSI
Unique international mobile subscriber identity comprised of 1
to 15 digits.
19
P-TMSI
The packet-temporary mobile subscriber identity, an integer
between 1 and 4294967295.
20
IMEISV
Unique 16 digit integer that indicates the IMEI with the software
version to identify the equipment identity retrieval type.
21
HLR-number
16 digit integer that identifies a specific HLR.
22
APN-size
Number 1 to 128.
23
APN
Dotted alphanumeric string, typically includes the network
identifier or the operator identifier to identify the access point
node (APN).
24
GGSN IP
dotted string
25
Old SGSN IP
dotted string
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Event Record Fields
Field
Field Content
Field Information
26
Old RAI
Routing area identifier in the format: ddd-ddd-xxxx-xx (d =
decimal; x = hex)
27
Number of PDP contexts
transferred
Number from 1 to 11.
28
Number of PDP contexts
dropped
Number from 1 to 11.
29
Requested QoS
Hex-digits. Refer to TS 24.008 for encoding.
30
Negotiated QoS
Hex-digits. Refer to TS 24.008 for encoding.
31
SGSN-IP-address
dotted string
The following table contains the availability of each field in each of the different event types:
• Type 1 - Attach
• Type 2 - Activate
• Type 3 - Local RAU
• Type 4 - New-ISRAU
• Type 5 - Old-ISRAU
• Type 6 - Deactivation
• Type 7 - Detach
• Type 8 - Authentication
• Type 9 - Modification
Table 20: Occurrence of Fields in Various Event Types
Field
Type 1
Type 2
Type 3
Type 4
Type 5
Type 6
Type 7
Type 8
Type 9
SMGR_NUMBER
X
X
X
X
X
X
X
X
X
SEQUENCE_NO
X
X
X
X
X
X
X
X
X
TIME
X
X
X
X
X
X
X
X
X
EVENT-IDENTITY
X
X
X
X
X
X
X
X
X
RESULT
X
X
X
X
X
X
X
X
X
RADIO-TYPE
X
X
X
X
X
X
X
X
X
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Event Record Fields
Field
Type 1
ATT-TYPE
X
Type 2
Type 3
Type 4
RAU-TYPE
X
X
INTRA-RAU TYPE
X
Type 5
ORIGIN-OF-
Type 6
Type 7
Type 8
X
Type 9
X
DEACTIVATION
CAUSE-PROT-
C4
C5
C4
C4
C4
C5
C4
C4
C5
GMM-CAUSE /
GSM-CAUSE
C4
C5
C4
C4
C4
C5
C4
C4
C5
DISC-REASON
C1
C1
C1
C1
C1
C1
C1
C1
C1
RAI
X
X
X
X
X
X
X
X
X
CELL-ID
C2
C2
C2
C2
C2
C2
C2
C2
C2
SAC
C2
C2
C2
C2
C2
C2
C2
C2
C2
MSISDN
C3
X
X
C3
X
X
C3
X
X
IMSI
X
X
X
X
X
X
X
X
X
(PTMSI)
C3
X
X
C3
X
X
C3
C3
X
IMEISV
C3
C3
C3
C3
C3
C3
C3
C3
C3
HLR-NUMBER
C3
X
X
X
X
X
C3
C3
X
INDICATOR
APN-SIZE
X
X
X
APN
X
X
X
GGSN-IP
C3
X
OLD-SGSN-IP
OLD-RAI
NO-OF-PDP-
X
X
X
X
X
X
TRANSFERRED
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EDR Storage
Field
Type 1
Type 2
Type 3
NO-OF-PDP-
Type 4
Type 5
Type 6
Type 7
Type 8
Type 9
X
DROPPED
Requested-QoS
X
X
Negotiated-QoS
X
X
Self SGSN IP
X
X
X
X
X
X
X
X
X
Notes:
• C1:
◦event disc-reason will be empty for successful attach/new-rau/local-rau/activation/modification
procedures.
◦disc-reason will be included for all old-rau/detach/deactivation.
◦disc-reason will be available for rejected/aborted attach/new-rau/local-rau/activation/modification
procedures.
• C2: cell ID for 2G, SAC for 3G
• C3: information provided if available
• C4:
◦attach/new-rau/local/rau/detach will have reject case if an attach-reject or accept was sent with the
cause value.
◦for authentication, only sync and mac failures will be logged if they are present - otherwise, the
value will be left blank.
• C5:
◦cause is present only for activate-reject or modify-reject
◦deactivation will always have a cause
◦activate-accept might have a cause sent (e.g., single address bearers only allowed)
EDR Storage
The EDRs are stored in CSV format on an external server. The external server relieves the SGSN of the storage
overhead and the post-processing overhead while the SGSN continues to perform call processing.
Architecture
The primary components of the feature architecture include:
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Limitations
• Session Manager (SessMgr) - reports events to the CDRMOD
• CDRMOD - stores EDR file in RAMDisk
• HardDisk Controller - transfers EDR files from RAMDisk to hard disk
Limitations
The reliability of event generation is limited by the CDRMOD framework, specifically:
• Any SessMgr death will result in the loss of event records that are not yet released to the CDRMOD.
• Any death of the CDRMOD proclet will result in the loss of records that are not yet written to the
RAMDisk.
• Any reboot of the chassis will result in the loss of records that are not yet flushed to the hard disk or to
an external server.
• In the case of overload of the CDRMOD, the SessMgr will ignore event records when its queue is full.
• The IMSI of the subscriber should be available while generating the EDR. Procedures which couldn't
be associated with any particular IMSI will not generate EDRs, for example, the inter-SGSN-RAU being
rejected because of its inability to contact the old-SGSN.
Configuration
The following commands enable the SGSN to log GMM/SM events in EDR files for 3G services:
configure
context ctx_name
sgsn-service srvc_name
[ default | no ] reporting-action event-record
Where:
• [ default | no ] - disables the logging function.
The following commands enable the SGSN to log GMM/SM events in EDR files for 2G services:
config
context ctx_name
gprs-service srvc_name
[ default | no ] reporting-action event-record
Where:
• [ default | no ] - disables the logging function.
The following commands access the EDR module configuration mode commands to enable the operator to
configure logging and file parameters and to configure file-transfer parameters.
config
context ctx_name
[ no ] edr-module active-charging-service
Where:
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Configuration
• no - disables the configured EDR logging and file parameters for the services in the context.
[ default | no ] cdr [ push-interval | push-trigger | remove-file-after-transfer | transfer-mode
| use-harddisk ]
Where:
• cdr - configures the EDR transfer parameters
• default - restores default parameter values
• no - disables the configuration
[ default | no ] file [ charging-service-name | compression | current-prefix | delete-timeout
| directory | edr-format-name | exclude-checksum-record | field-separator | file-sequence-number |
headers | name | reset-indicator | rotation | sequence-number | storage-limit | time-stamp | trailing-text
| trap-on-file-delete | xor-final-record
Where:
• file - configures file creation properties for the records
• default - restores the default file creation properties
• no - disables the configuration
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CHAPTER
15
GTPU Error Indication Enhancement
• Feature Description, page 255
Feature Description
This enhancement provides a solution to avoid GTPU Path Failure when a burst of GTPU Error Indication
occurs. This enhancement is applicable only for SGSN.
Consider the following scenario:
1 Following a kernel crash and Hardware Failure (Fabric corruption) in a Demux Card, the SGSN is unable
to respond Echo Requests from the GGSN. This results in Path Failure detection by the GGSN and a large
number of sessions are cleaned up.
2 But the sessions are still active at the SGSN in PSC3 Cards where Session Manager is running. The SGSN
sends uplink data for these sessions and this triggers a flood of GTPU Error Indications (~6 to ~9 million)
from the GGSN to SGSN.
3 Simultaneously a Demux card migration is triggered in the SGSN to recover from the kernel crash and
Hardware Failure. After the migration is completed, the SGSN restarts the Path Management Echo Requests.
But the GGSN had already started sending Echo requests as soon as the new sessions were set up at the
GGSN. This difference in the restarting of the Echo requests from both ends on the path leads to delay in
detecting path failure between the SGSN and GGSN if echo responses are not received for any reason.
4 Once the Demux card has recovered at SGSN, the following are observed:
• A flood of GTPU Error Indication messages further result in packet drops at the SGSN
• The Echo Request causing another path failure at the GGSN
• Echo Response cause a path failure on the SGSN with delay as well as loss of GTPU Error Indications
at SGSN
5 This delay in Path Failure results in another flood of GTPU Error Indications in response to SGSN uplink
data for the active sessions, which were already cleaned up at the GGSN (those created after first path
failure). This flood of GTPU Error Indications results in additional packet drops at the SGSN. The cycle
of cleaning up sessions and setting up new sessions continues until the SGSN is restarted.
The issue is resolved by creating an additional midplane socket for GTPU Error Indications so that flood of
GTPU Error Indication will not create any impact on Path Management. New midplane socket and flows have
been introduced to avoid path management failure due to flood of GTPU Error Indication packets. GTPU
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GTPU Error Indication Enhancement
Feature Description
Echo Request/Response will continue to be received at existing midplane sockets. A new path for GTPU
Error Indication will prevent issues in Path Management towards GGSN or towards RNC and avoids un-wanted
detection of path failures. This enhancement requires new flows to be installed at the NPU.
The following existing statistics are helpful in observing loss of packets and drop of GTPU Error Indication
Packets:
[local]asr5000# show sgtpu statistics
Total Error Ind Rcvd: 0
Rcvd from GGSN: 0
Rcvd from RNC: 0
Rcvd from GGSN through RNC: 0
Rcvd from RNC through GGSN: 0
The following show commands are useful to verify the NPU related statistics:
• To check the flow id range associated with sgtpcmgr, use the following command:
For ASR55K: show npumgr flow range summary
• To check whether flow corresponding to GTPU Error Indication is installed or not, use the following
command:
For ASR5K: [local]asr5000# show npu flow record min-flowid id max-flowid id slot no verbose
For ASR55K: show npumgr flow statistics
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CHAPTER
16
Identity Procedure on Authentication Failure
• Feature Description, page 257
• How It Works, page 258
• Configuring Performance of Identity Procedure, page 259
• Monitoring and Troubleshooting the Performance of Identity Procedure for Authentication Failure,
page 260
Feature Description
Performing Identity Procedure in response to authentication failures results in fewer subscribers losing network
connectivity due to Authentication Rejects. In the network, authentication rejects due to authentication failures
such as Sync failure, GSM authentication unacceptable, and MAC failure, cause loss of network connectivity
to subscribers. Often uthentication failure is due to incorrectly sent authentication vectors, which could be
due to a P-TMSI (Packet Temporary Mobile Subscriber Identity) collision in the network.
Authentication Failures
GSM Authentication Unacceptable
When a 3G MS/UE attaches and sends a RAU Request with P-TMSI identity, this means that this subscriber:
• was registered in the SGSN,
• received this P-TMSI identity from the SGSN,
• left the SGSN, and
• has returned to this SGSN.
• And in the time between leaving and returning, another subscriber, a 2G subscriber, has registered with
this SGSN and has the same P-TMSI.
The SGSN tries to authenticate the returning 3G subscriber with the authentication vectors of the 2G subscriber.
This causes the MS/UE to send authentication failure with cause "GSM authentication unacceptable" because
the SGSN has sent RAND from the 2G subscriber when the 3G subscriber's MS/UE was expecting quintets.
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Identity Procedure
MAC Failure
When a 2G MS sends a RAU Request (new SGSN RAU) with a P-TMSI identity, the SGSN tries to authenticate
the new 2G subscriber with the authentication vectors of a different 2G subscriber. In this scenario, it appears
as if IMSI-PTMSI collision occurs within the SGSN or it is due to the peer-SGSN sending vectors of another
subscriber or an incorrect IMSI in the Context Response. This results in authentication failure with cause
"MAC failure".
Identity Procedure
In most cases, these forms of authentication failure can be resolved by the subscriber restarting their device
- if the subscriber knows to try this.
MAC Failure
The SGSN supports performing an Identity Procedure on receiving MAC Failure in 3G and on MAC Failure
during 2G Attach.
Beginning with release 19.2, the SGSN also supports performing Identity Procedure on MAC Failure in 2G
New-ISRAU.
If the SGSN gets MAC failure for the first time from an MS/UE, the SGSN sends an SGSN-Context-ACK
Failure message to the peer-SGSN and starts an Identity Procedure.
1 Once the SGSN receives the IMSI from the MS/UE in an Identity Response, if the IMSI is different from
the IMSI received from the peer-SGSN then the SGSN will authenticate by fetching vectors from the
HLR.
2 Next the SGSN tries to get the context from the peer-SGSN by initiating a new Context Request, including
the IMSI obtained from the MS/UE, and the MS/UE validated flag is set.
3 The SGSN proceeds with the call.
If the IMSI is not found in the peer-SGSN, the SGSN sends RAU Reject with cause "MS Identity Cannot Be
Derived by the Network". In accordance with the 3GPP specification, the MS/UE tries to register again using
its IMSI.
GSM Authentication Unacceptable
Beginning with Release 19.2, the SGSN performs Identity Procedure on receiving GSM Authentication
Unacceptable failure for 3G Attach, for 3G New-ISRAU, for 3G Intra-RAU, and for Inter-RAT.
If the SGSN gets the correct IMSI in the Identity Response, then the SGSN will try to authenticate the MS/UE
again using the vectors from the HLR. If the authentication fails again, the SGSN send Authentication Reject
to the MS/UE.
How It Works
3GPP specification TS 24.008, section 4.3.2.6 (c) suggest that "Upon the first receipt of an AUTHENTICATION
FAILURE message from the MS with reject cause "MAC failure" or "GSM authentication unacceptable", the
network may initiate the identification procedure. This is to allow the network to obtain the IMSI from the
MS. When the SGSN receives authentication failure message with cause as GSM authentication unacceptable
or MAC failure from a 3G/2G subscriber respectively, it will start identity procedure and authenticate the
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Identity Procedure on Authentication Failure
GSM Authentication Unacceptable
subscriber with vectors fetched using IMSI. This will avoid network loss to subscribers due to such PTMSI
collision cases.
With Release 19.2, the SGSN performs Identity Procedure in accordance with 3GPP recommendations, as
detailed below.
GSM Authentication Unacceptable
Scenarios:
• 3G Attach Request from a UE with P-TMSI (with the same P-TMSI the SGSN gave to a 2G subscriber
now registered in the SGSN)
• 3G New-ISRAU with a P-TMSI
In the above scenarios, if authentication fails due to cause "GSM authentication unacceptable", then the SGSN
performs the identity procedure and authenticates using vectors from the HLR.
In the case of a 3G Intra-RAU or Inter-RAT, if the arriving MS/UE is a different subscriber than the already
registered one, then the SGSN rejects the RAU with cause "MS Identity Cannot be Derived by the Network",
so the UE will use the IMSI at the next Attach.
MAC Failure in 2G
The SGSN will perform identity procedure if MAC failure is received for any of the following scenario:
• 2G Atach Request from a UE with P-TMSI (with a P-TMSI given to a different 2G subscriber now
registered in the SGSN).
• 2G New-ISRAU with a P-TMSI
Configuring Performance of Identity Procedure
The default behavior of the SGSN is to perform identity procedure when authentication failures occur. The
configuration noted below, allows the operator to disable or to re-enable the SGSN's default behavior.
With Release 19.2, the default behavior has been extended to enable the SGSN to initiate the identity procedure
on receiving authentication failures with either cause "MAC Failure" or cause "GSM Authentication Failure".
The following command sequence configures the SGSN so that performance of the identity procedure upon
receipt of an authentication failure is disabled:
config
context context_name
sgsn-service sgsn_srvc_name
no gmm perform-identity-on-auth-failure
end
Notes:
• If the default behavior has been disabled with the command sequence noted above, then to re-enable
performance of the identity procedure upon receipt of an authentication failure, re-enter the sequence
but do not include the no prefix with the gmm perform-identity-on-auth-failurecommand.
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Verifying the Configuration
Verifying the Configuration
To determine the current configuration for this feature, issue the following command sequence in the Exec
mode.
show sgsn-service name sgsn_srvc_name
The output generated by this command will include the following information field with either a 'Disabled'
or 'Enabled' value :
GMM-Perform-Identity-After-Auth
:
Disabled
Monitoring and Troubleshooting the Performance of Identity
Procedure for Authentication Failure
show gmm-sm statistics verbose
Statistics are available which track of the number of IMSI Identity Requests triggered in response to
authentication failures noted in this chapter.
The show gmm-sm statistics verbose command from the Exec mode will generate an output that includes
the following:
IMSI-Identity-Req triggered due to auth failures:
3G-GSM Auth Unacc:
0
2G-MAC failure:
3G-MAC failure:
0
0
show gmm-sm statistics
The number of IMSI identity requests initiated by the SGSN are captured in the following counter:
Total-IMSI-Identity-Req
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17
Idle Mode Signalling Reduction on the S4-SGSN
This chapter describes the Idle Mode Signaling Reduction (ISR) feature and its implementation and use on
the ASR 5000 S4-SGSN.
Important
A separate feature license is required to enable the ISR feature. Contact your Cisco representative for
licensing information.
• Feature Description, page 261
• How ISR Works, page 262
• Configuring Idle-Mode-Signaling Reduction, page 268
• Monitoring and Troubleshooting the ISR Feature, page 270
Feature Description
The Idle mode signaling reduction (ISR) feature on the S4-SGSN provides a mechanism to optimize and/or
reduce signaling load during inter-RAT cell-reselection in idle mode (that is, in the ECM-IDLE, PMM-IDLE,
and GPRS-STANDBY states). It is a mechanism that allows the UE to remain simultaneously registered in
a UTRAN/GERAN Routing Area (RA) and an E-UTRAN Tracking Area (TA) list. This allows the UE to
make cell reselections between E-UTRAN and UTRAN/GERAN without having to send any TAU or RAU
requests, as long as the UE remains within the registered RA and TA list.
ISR is a feature that reduces the mobility signalling and improves the battery life of UEs. ISR also reduces
the unnecessary signalling with the core network nodes and air interface. This is important especially in initial
deployments when E-UTRAN coverage will be limited and inter-RAT changes will be frequent.
The benefit of the ISR functionality comes at the cost of more complex paging procedures for UEs, which
must be paged on both the registered RA and all registered TAs. The HSS also must maintain two PS
registrations (one from the MME and another from the SGSN).
Important
The Gn/Gp SGSN does not support ISR functionality.
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Relationships
Relationships
The ISR feature on the S4-SGSN is related to:
• ISR must be enabled on the peer MME and SGW nodes.
• The SGSN must be configured with the following:
◦2G Service + S4 Support
◦3G Service + S4 Support
◦2G + 3G Services + S4 Support
Important
If the S4-SGSN is configured to support both 3G and 2G services, it is recommended to enable both 2G
and 3G ISR functionality. This ensures that for the ISR activated subscribers, inter-RAT routing area
updates between 2G and 3G preserve the ISR status if there is no SGW relocation.
How ISR Works
ISR requires special functionality in both the UE and the network (i.e. in the SGSN, MME, SGW and HSS)
to activate ISR for a UE. The network can decide for ISR activation individually for each UE. ISR support is
mandatory for E-UTRAN UEs that support GERAN and/or UTRAN and optional for the network. Note that
the Gn/Gp SGSN does not support ISR functionality.
ISR is not activated on Attach. ISR can only be activated when a UE first registers in a RA on an SGSN and
then registers in a TA on an MME or vice-versa. It is an inherent functionality of the mobility management
(MM) procedures to enable ISR activation only when the UE is able to register via E-UTRAN and via
GERAN/UTRAN. For example, when there is no E-UTRAN coverage there will be also no ISR activation.
Once ISR is activated it remains active until one of the criteria for deactivation in the UE occurs, or until the
SGSN or the MME indicate ISR is no longer activated during an update procedure, i.e. the ISR status of the
UE has to be refreshed with every update.
When ISR is activated this means the UE is registered with both the MME and the SGSN. Both the SGSN
and the MME have a control connection with the SGW. The MME and the SGSN are both registered at the
HSS. The UE stores mobility management parameters from the SGSN (for example, P-TMSI and RA) and
from the MME (for example, GUTI and TAs). The UE stores session management (bearer) contexts that are
common for E-UTRAN and GERAN/UTRAN accesses. In an idle state the UE can reselect between E-UTRAN
and GERAN/UTRAN (within the registered RA and TAs) without any need to perform TAU or RAU procedures
with the network. the SGSN and MME store each other's address when ISR is activated.
The S4 SGSN supports the following scenarios for 2G ISR:
• ISR activation by SGSN on new SGSN RAU from MME
• ISR activation on SGSN in old SGSN RAU to MME
• Ready to standby state transition triggered Release Access Bearer Request to SGW
• Downlink data notification from SGW:
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How ISR Works
◦Downlink data notification UE responds to SGSN
◦Downlink data notification no response from UE
• Stop paging indication
• UE initiated detach for ISR activated subscriber under GERAN
• UE initiated detach under EUTRAN/MME initiated detach or Detach notification from MME
• SGSN initiated detach for ISR activated subscriber
• HSS/HLR initiated detach for ISR activated subscriber
• ISR deactivation due to delete bearer request with ISR deactivation cause
• ISR deactivation due to last PDN connection deletion (SGSN/UE/PGW/HSS/HLR-initiated)
• ISR deactivation due to SGW change
• ISR-deactivation due to context transfer between same Node types(S4 SGSN to and from S4 SGSN)
• Intra-RAU without SGW change for ISR-activated subscriber
• Inter-GPRS service RAU without SGW change for ISR-activated subscriber
• Intra-SGSN inter-system handover from 2G to 3G without SGW change for ISR activated subscriber
• Intra-SGSN inter-system handover from 3G to 2G without SGW change for ISR activated subscriber
The following scenarios are supported for 3G ISR:
• ISR activation by 3G SGSN on new 3G SGSN RAU from MME
• ISR activation by 3G SGSN on old 3G SGSN RAU to MME
• ISR activation by 3G SGSN on new 3G SGSN SRNS relocation from MME (Connected mode IRAT
handover from MME to SGSN)
• ISR activation by 3G SGSN on old 3G SGSN SRNS relocation to MME (Connected mode IRAT
handover from SGSN to MME)
• Iu release triggered Release Access Bearer Request to SGW
• Downlink data notification from SGW:
◦Downlink data notification UE responds to SGSN
◦Downlink data notification no response from UE
• Stop paging indication
• UE initiated detach for ISR activated subscriber under UTRAN
• UE initiated detach under EUTRAN/MME initiated detach or Detach notification from MME
• SGSN initiated detach for ISR activated subscriber
• HSS/HLR initiated detach for ISR activated subscriber
• ISR deactivation due to delete bearer request with ISR deactivation cause
• ISR deactivation due to last PDN connection deletion (SGSN/UE/PGW/HSS/HLR-initiated)
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Limitations
• ISR deactivation due to SGW change
• ISR-deactivation due to context transfer between same Node types (S4 SGSN to and from S4 SGSN)
• Intra-RAU without SGW change for ISR-activated subscriber
• Intra-SRNS without SGW change for ISR activated subscriber
Limitations
There are no known limitations to the 2G ISR feature.
For the 3G SGSN, if an ISR is already active between the SGSN and an MME and the system receives a
relocation required towards an eNodeB served by the same ISR associated with the MME, the S4-SGSN first
tears down the existing S3 tunnel and will initiate a forward relocation request on a new tunnel. If the procedure
completes successfully, ISR association would be continued on the new tunnel. However, if the relocation is
cancelled then the tunnel is lost and the ISR is deactivated.
Call Flows
This section provides various call flows that illustrate the primary procedures used for the ISR feature:
2G ISR Activation by the S4-SGSN
The following illustration shows the ISR activation procedure when initiated by the S4-SGSN for a 2G
subscriber.
Note the following major procedural functions:
• E-URTRAN attach at the MME.
• A Routing Area Update is sent to the SGSN.
• The SGSN sends a Context Request to the MME upon receiving the RAU Request. If the MME supports
ISR, it will set the ISRSI bit in the Context Response message.
• Upon receiving the Context Response from the MME, the GMM sets the ISRAI flag if ISR is already
activated for the subscriber or if all of following conditions are satisfied:
◦The UE is EPC-capable.
◦ISR is enabled in the configuration.
◦The peer node is the MME.
◦The peer node has indicated that ISR is supported in the Context Response message.
• The SGSN will not activate ISR if there is change in SGW. So, the SGSN will be setting the 'ISRAI' bit
in the Modify Bearer Request/Context Ack message provided there is no change in SGW and all of
above conditions in the previous bullet point are satisfied.
• If the SGSN also monitors the SGSN-MME-Separated flag in the Update location Response or the
Separation Indicator in Update Location Ack - ULA Flags IE to activate ISR for subscriber and ISR
status is marked deactivated if not indicated by HLR/HSS.
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Call Flows
• The SGSN sends a RAU accept with update type RA updated and ISR activated or combined RA/LA
updated and ISR activated depending on the update request.
• The SGSN sends a Periodic RAU timer to the UE in a RAU accept message and also a GERAN/UTRAN
Deactivate ISR timer (T3323) timer value to the UE. Parallel to the periodic RAU timer, the SGSN starts
its mobile reachability timer (MNR timer) which is configurable. The default is 4 minutes greater than
the periodic RAU timer. The UE is expected to contact the SGSN again within the mobile reachability
timer duration either by sending a periodic RAU or some other signalling. If the UE fails to contact the
SGSN during this timer, SGSN will start the implicit detach timer which by default is 4 minutes greater
than T3323 timer. The implicit detach timer value is also configurable at the SGSN. If the UE fails to
contact even within this implicit detach timer, then the SGSN will locally detach the UE and will send
a Detach Notification with cause Local detach to the MME so that ISR gets deactivated at the MME.
Figure 46: ISR Activation on the S4-SGSN
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Call Flows
2G ISR Activation by the MME
The following illustration shows the ISR activation procedure when initiated by the MME for a 2G subscriber.
Note the following major procedural functions:
• Context request from MME.
• The SGSN sends a Context Response to the MME with the 'ISRSI' bit set provided all of following
conditions are satisfied:
◦The UE is EPC-capable.
◦The UE is ISR-capable.
◦The ISR is enabled by configuration.
◦The peer node is an MME.
• If the old node is an old S4-SGSN, the MME sends a Context Acknowledge (ISR Activated) message
to the old SGSN.
• Unless ISR Activated is indicated by the MME, the old S4-SGSN marks in its context that the information
in the Gateways is invalid. This ensures that the old S4-SGSN updates the Gateways if the UE initiates
a RAU procedure back to the old S4-SGSN before completing the ongoing TAU procedure. If ISR
Activated is indicated to the old S4-SGSN, this indicates that the old S4-SGSN shall maintain its UE
context including authentication quintets and stop the inter-SGSN handover procedure guard timer
(2G).When the UE is initially attached, the SGSN started the Mobile Reachability Timer (MNR timer).
This timer value is slightly larger than the Periodic RAU Timer value given to the UE by SGSN. The
default is 4 minutes longer. The UE is expected to contact SGSN through a periodic RAU or some other
signalling message within this timer. If the UE did not contact SGSN within this timer, the S4-SGSN
shall start the implicit detach timer with a slightly larger value than the UE's GERAN/UTRAN Deactivate
ISR timer (T3323). The implicit detach timer value is also configurable at the SGSN. If the UE fails to
contact even within this implicit detach timer, then the SGSN will locally detach the UE and will send
a Detach Notification with cause Local detach to the MME so that ISR is deactivated at the MME.
• When ISR Activated is not indicated and an inter-SGSN handover procedure guard timer expires, the
old SGSN deletes all bearer resources of that UE. As the Context Acknowledge from the MME does
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Standards Compliance
not include any S-GW change, the S4 SGSN does not send any Delete Session Request message to the
S-GW.
Figure 47: 2G ISR Activation by the MME
Standards Compliance
The 2G ISR feature complies with the following standards:
• TS 23.060 version 10: 3rd Generation Partnership Project Technical Specification Group Services and
System Aspects General Packet Radio Service (GPRS) Service description Stage 2.
• TS 23.401 version 10: 3rd Generation Partnership Project Technical Specification Group Services and
System Aspects General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial
Radio Access Network (E-UTRAN) access.
• TS 23.272 version 10: Universal Mobile Telecommunications System (UMTS) LTE 3GPP Evolved
Packet System (EPS) Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control
plane (GTPv2-C) Stage 3.
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Configuring Idle-Mode-Signaling Reduction
• TS 29.274 version 10: Universal Mobile Telecommunications System (UMTS) LTE 3GPP Evolved
Packet System (EPS) Evolved General Packet Radio Service (GPRS) Tunnelling Protocol for Control
plane (GTPv2-C) Stage 3.
Configuring Idle-Mode-Signaling Reduction
This section describes how to configure ISR on the S4-SGSN.
Note
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Configuring 2G ISR
Configuring 2G ISR includes creating a call-control-profile with ISR enabled for GPRS, and configuring an
implicit-detach-timeout in the configured GPRS service on the S4-SGSN.
config
call-control-profile name
idle-mode-signaling-reduction access-type gprs
end
config
context plmn_name
gprs-service gprs_service_name
gmm implicit-detach-timeout value
end
Notes:
• Where call-control-profile name specifies the name of the call-control-profile tin which 2G ISR
functionality is to be configured.
• gprs enables 2G ISR functionality.
• Alternatively, remove idle-mode-signaling-reduction access-type gprs can be used to disable 2G ISR
functionality.
• context plmn_name is the name of the public land mobile network context in which the GPRS (2G)
service is configured.
• gprs-service gprs_service_name specifies the name of the configured GPRS (2G) service for which
you want to configure the implicit-detach-timeout value.
• gmm implicit-detach-timeout value specifies the implicit detach timeout value to use for 2G ISR. Valid
entries are from 240 to 86400 seconds. The default value is 3600 seconds.
Verifying the 2G ISR Configuration
This section describes how to verify the 2G ISR configuration.
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Configuring 3G ISR
To verify that 2G ISR and the gmm implicit-detach-timeout is configured:
show configuration
...
call-control-profile
name
idle-mode-signaling-reduction access-type gprs
....
context context_name
gmm T3323-timeout
value
gmm implicit-detach-timeout value
To verify that 2G ISR is enabled in the call-control-profile:
show call-control-profile full name cc-profile-name
...
Treat as PLMN
:Disabled
Idle-Mode-Signaling-Reduction (ISR) for UMTS
Idle-Mode-Signaling-Reduction (ISR) for GPRS
:Disabled
:Enabled
Location Reporting for UMTS
...
:Disabled
Configuring 3G ISR
Configuring 3G ISR includes creating a call-control-profile with ISR enabled for UMTS, and configuring an
implicit-detach-timeout in the configured SGSN service on the S4-SGSN.
config
call-control-profile cc-profile-name
idle-mode-signaling-reduction access-type umts
end
config
context context_name
sgsn-service sgsn_service_name
gmm T3323-timeout mins
end
Notes:
• idle-mode-signaling-reduction access-type umts enables 3G ISR in the call-control-profile.
• gmm t3323-timeout mins specifies the amount of time, in minutes, the UE should wait after the Periodic
RAU timer (t3312 timer) expiry before deactivating ISR. Valid entries are from 1 to 186. The default
is 54.
Verifying the 3G ISR Configuration
This section describes how to verify the 3G ISR configuration.
To verify that 3G ISR is enabled and the gmm T3323 timeout is configured:
show configuration
...
call-control-profile
name
idle-mode-signaling-reduction access-type umts
....
context context_name
gmm T3323-timeout value
...
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Monitoring and Troubleshooting the ISR Feature
To verify that 3G ISR is enabled in the call-control-profile:
show call-control-profile full name cc-profile-name
...
Treat as PLMN
:Disabled
Idle-Mode_Signaling-Reduction (ISR) for UMTS
:Enabled
...
Monitoring and Troubleshooting the ISR Feature
This section provides information on how to monitor the ISR feature and to determine that it is working
correctly.
ISR Show Command(s) and Outputs
This section provides information regarding show commands and/or their outputs in support of the ISR feature.
show subscribers gprs-only full
This command provides information that indicates whether ISR is activated for 2G subscribers, provides the
MME tunnel endpoint ID being used for the ISR-activated 2G subscriber, and the IP address of the MME
associated with the ISR-activated 2G subscriber.
• ISR-Activated: (True or False)
• MME Ctrl Teid: (MME Control Tunnel Endpoint Identifier)
• MME IP Address: (IP address of MME)
show subscribers sgsn-only full
This command provides information that indicates whether ISR is activated for 3G subscribers, provides the
specific S3 tunnel on the MME being used for this ISR-activated subscriber, and the IP address of the MME
associated with the ISR-activated 3G subscriber.
• ISR-Activated: (True or False)
• MME Ctrl Teid: (MME Control Tunnel Endpoint Identifier)
• MME IP Address: (IP address of MME)
show s4-sgsn statistics (2G ISR)
The output of this command provides information on the various reasons for deactivations of ISR-activated
2G subscribers:
• 2G Intra RAU with SGW Relocation
• Detach Notification from MME to 2G
• 2G MS Initiated Detach
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ISR Show Command(s) and Outputs
• 2G Cancel Location from HSS/HLR
• 2G Local Admin Detach
• 2G Implicit Detach Timer Expiry
show s4-sgsn statistics (3G ISR)
The output of this command tracks the number of ISR deactivations due to various reasons for a 3G
ISR-activated subscriber:
• 3G Intra RAU with SGW Relocation
• 3G NW Initiated Detach
◦3G MR IDT Expiry
• 3G MS Initiated Detach
• 3G Cancel Location from HSS/HLR
• 3G SRNS Abort
• 3G Local Admin Detach
• 3G SGW Change During SRNS
show gmm statistics (2G ISR)
The output of this command indicates the total of currently activated 2G ISR subscribers:
• ISR Activated Subscribers:
◦2G Intra RAU with SGW Relocation
show gmm statistics (3G ISR)
The output of this command tracks the number of currently ISR-activated 3G subscribers:
• ISR Activated Subscribers:
◦3G-ISR-Activated
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ISR Show Command(s) and Outputs
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CHAPTER
18
IMSI Manager Broadcast Control
• Feature Description, page 273
• How It Works, page 274
• Configuring IMSI Manager Broadcast Control, page 275
• Monitoring and Troubleshooting IMSI Manager Broadcast Control, page 275
Feature Description
The IMSI Manager is the Demux process that selects the Session Manager instance based on the Demux
algorithm logic to host a new session for 2G/3G/4G subscribers for SGSN/MME. The IMSI Manager maintains
the IMSI-SMGR mapping for SGSN (2G/3G) and MME (4G) subscribers. The mapping maintained at
IMSIMGR task is usually in sync with the mapping maintained at all session managers. But in some rare
cases, there is a mismatch due to problems during the synchronization process. In such scenarios, the IMSIMGR
task sends out a broadcast message to all session managers hoping that at least one of them will be hosting
that session and could respond positively to this broadcast.
If none of the Session Managers respond with the mapping, the IMSI Manager considers it as request for an
UNKNOWN (unregistered) subscriber and forwards it to a random Session Manager, which in turn sends an
error response for the HLR request. The broadcasts from the IMSI Manager happen through a non-blocking
vector call to all active Session Managers which can lead the IMSI Manager into a CPU overload condition
considering the high number of session managers.
IMSI Manager broadcast control is implemented by the following:
• In IMSI Manager, broadcast disabling CPU threshold value defined; once the CPU utilization crosses
this threshold, the IMSI Manager will not broadcast any unknown subscriber requests from HLR. Default
value of this threshold is set as 50%. A CLI command is provided to optionally define the CPU threshold.
• In IMSI Manager, congestion threshold value of 70% is defined; once the CPU utilization crosses this
threshold, the IMSI Manager will trigger congestion control action and will drop all unknown subscriber
requests from HLR.
Important
This feature is enabled by default.
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How It Works
How It Works
IMSI Manager Broadcast Control
IMSI Manager broadcast control is applicable only to SGSN. The MAP requests from the HLR arrives at the
IMSI Manager as the Link Manager cannot find the Session manager instance from IMSI in the request. The
following MAP requests arrive at the IMSI Manager:
1 CANCEL LOCATION REQUEST
2 Standalone INSERT SUBSCRIPTION DATA (ISD)
3 Delete Subscriber Data (DSD)
4 Provide Subscriber Location (PSL)
The IMSI Manager looks for the Session manager id which hosts the IMSI in its mapping table. If the mapping
does not exist, the requests are broadcasted to all active Session Managers for finding the session or mapping.
If all the Session managers respond with negative response, the IMSI Manager sends the MAP request to a
random Session manager which in turn responds with a Map User Error response with cause as "Unidentified
Subscriber". Broadcasting of request consumes a huge amount of IMSI Manager CPU capacity, it is also
observed that the most of the unknown requests received genuine unknown subscriber requests sent by HLR
and the HLR is incorrectly sending these requests to the SGSN. To conserve the IMSI Manager CPU,
broadcasting of these requests are avoided.
IMSI Manager Broadcast Disabled During System Reboot
After a system reboot, the subscribers are not yet registered in the system. During this period, if HLR sends
ISD or Cancel Location Requests to the system in huge numbers, these requests are broadcasted thus leading
to an IMSI Manager CPU overload condition. To conserve IMSI manager CPU, the IMSI Manager will not
perform any broadcasting for the UNKNOWN MAP requests from HLR for first 60 minutes after reboot of
the system. This SGSN feature is enabled by default and is not configurable. After 60 mins, the behavior as
per the CLI configuration for IMSI manager broadcasting will be applied.
Disabling Broadcast
Broadcasting is stopped when the IMSI Manager is busy handling heavy traffic (that is, when IMSI Manager
reaches a specific CPU threshold). All the IMSI Manager instances monitor their CPU usage and when the
CPU threshold is reached, broadcasting is stopped until the CPU comes down below the threshold value.
Instead of broadcasting to all Session Managers, the request is sent to any random Session Manager which in
turn sends the response back to the originating node. This feature is enabled by default and the default CPU
threshold for disabling broadcasting is 50%. The configured CPU threshold overrides this default value.
Congestion Control
In IMSI Manager, congestion is triggered when CPU crosses 70%; once the CPU utilization crosses this
threshold, the IMSI Manager will trigger congestion control action and will silently drop all unknown subscriber
requests from HLR. No responses will be sent to peer originating the requests.
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Configuring IMSI Manager Broadcast Control
Note
The thresholding application is a best effort at that instance and if the incoming rate of unknown messages
is unusually high, a brief spike in the CPU usage of IMSIMGR task might occur.
Configuring IMSI Manager Broadcast Control
This section describes the configuration procedure for this feature. A new keyword is added to the command
task facility imsimgr command under the global configuration mode to configure an IMSI Manager CPU
threshold, once this threshold is reached the IMSI Manager stops broadcasting to conserve CPU.
config
task facility imsimgr { avoid-sessmgr-broadcast { cpu_threshold percentage_value }| max integer_value
| required-sessmgr no_sess_mgrs | sessmgr-sessions-threshold high-watermark high_value low-watermark
low_value }
end
Notes:
• The keyword cpu_threshold specifies the CPU value of the IMSI Manager in percentage.
• The percentage_value is a percentage integer from 50 up to 70 %. The default value is 50%.
Examples
The following command is used to disable all IMSI Manager Broadcasts:
task facility imsimgr avoid-sessmgr-broadcast
The following command is used to disable broadcast after the IMSI Manager CPU reaches 60%:
task facility imsimgr avoid-sessmgr-broadcast cpu_threshold 60
Monitoring and Troubleshooting IMSI Manager Broadcast
Control
New statistics are introduced as a part feature which can be viewed in the Debug mode. The operator can use
these statistics to get the current status of broadcasting, which is either broadcasting is enabled or disabled.
Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs:
show demuxmgr statistics imsimgr all
• Total Unknown Subscriber Request Rx counters
• Insert Subscriber Data req
• Delete Subscriber Data req
• Cancel location req
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Show Command(s) and/or Outputs
• Other unknown req
• Imsimgr-Sessmgr Broadcast statistics for unknown Subscriber requests
• Broadcast Current status ( enabled/disabled and reason for disabling)
• Number of requests sent to Random smgr (after bcast failure rsp)
• Number of requests sent to Random smgr (broadcast disabled)
• Number of request dropped due to High CPU
Apart from the statistics listed above, SGSN Network Overload protection statistics which were only available
in the show gmm-sm statistics are now available as a part of show demuxmgr statistics imsimgr all. The show
output is realigned for better readability. Unusual logs are added in IMSIMGR to print the IMSI of subscriber
and the unknown request type received from the peer node. Debug logs are also provided to display the current
CPU usage and the request types that are dropped.
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IMSI Manager Overload Control
• Feature Description, page 277
• Monitoring and Troubleshooting IMSI Manager Overload Control, page 278
Feature Description
The IMSI Manager is the Demux process that selects the Session Manager instance based on the Demux
algorithm logic to host a new session for 2G/3G/4G subscribers for SGSN/MME. The IMSI Manager maintains
the IMSI-SMGR mapping for SGSN (2G/3G) and MME (4G) subscribers. The mappings maintained for all
registered subscribers are synchronous with the Session Managers.
When the incoming attach rate is high at the IMSIMGR in a short span of time, the CPU consumption is very
high and affects the normal processing activities of the IMSI Manager. At times this can lead to an IMSI
Manager crash. Overload control methods are devised through this feature enhancement to keep the IMSI
Manager CPU under control.
Important
This feature is enabled by default.
IMSI Manager Overload Control
IMSI Manager Overload control is implemented on both SGSN and MME call flows. Attach rate
throttling(network overload protection) is implemented in IMSI Manager to cap the rate at which new requests
are accepted by SGSN and MME. This feature helps us process the incoming new subscriber requests (for
example ATTACH/ISRAU) at a configured rate, therefore the HLR and other nodes are not overloaded. The
SGSN and MME have separate pacing queues in the IMSI Manager to monitor the incoming rate of requests
and have a separate network overload configuration as well.
For the SGSN, the following requests are paced using the pacing queues:
• Initial ATTACH (with IMSI , L-PTMSI ,F-PTMSI)
• Inter-SGSN RAU
• Empty-CR requests
In the MME, new connections are setup for the following events:
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• UE initiated initial Attach
• All types of attach – IMSI, local GUTI, foreign GUTI, mapped GUTI, emergency and so on.
• UE initiated Inter-CN node TAU request requiring context transfer from old MME/SGSN
• TAU request with foreign GUTI or mapped GUTI
• Peer SGSN/MME initiated forward relocation request via Gn/S10/S3
With this feature enhancement when the incoming attach rate is high, the pacing queue becomes full and the
further requests are either dropped or forwarded to Session Manager. The Session Manager in turn sends the
reject response based on the configuration. When network overload protection action is set as "reject", the
IMSI Manager has to forward overflowing requests from the pacing queue to Session Manager through a
messenger call to send back error response. The IMSI Manager spends more time on messenger read and
write. The IMSI Manager CPU reaches high values when the incoming call rate is very high (both SGSN/MME)
though the network overload protection is configured. To ensure that the IMSI Manager CPU is under control,
the IMSI Manager reduces certain messenger activities on reaching the default CPU threshold of 70%. This
threshold value is fixed and this feature is enabled by default. This value is currently non-configurable. The
IMSI Manager drops the overflowing requests from the pacing queue when the CPU crosses 70% mark instead
of rejecting the request. Every IMSI Manager instance monitors its CPU usage independently and actions are
taken according to the CPU usage.
Relationships to Other Features
Attach throttling feature will have an impact due to this feature enhancement. Once the CPU reaches the
threshold of 70%, the messages will be dropped (irrespective of configured action).
Monitoring and Troubleshooting IMSI Manager Overload Control
New statistics are introduced as a part of feature which can be viewed in the Debug mode. The operator can
use these statistics to find the number of requests dropped due to overload.
Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs:
show demuxmgr statistics imsimgr all
These counters are available for both MME and SGSN separately.
• Requests dropped due to pacing queue with High Imsimgr CPU
Apart from the statistics listed above, SGSN Network Overload protection statistics which were only available
in the show gmm-sm statistics are now available as a part of show demuxmgr statistics imsimgr all. The show
output is realigned for better readability. Debug logs are also provided to display the current CPU usage.
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ISR with Circuit Switched Fallback
• ISR with CSFB - Feature Description, page 279
• Call Flows, page 280
• Relationships to Other Features, page 282
• Relationships to Other Products, page 282
• How it Works, page 283
• ISR CSFB Procedures, page 284
• Standards Compliance , page 287
• Configuring ISR with Circuit Switched Fallback, page 288
• Monitoring and trouble-shooting the CSFB feature, page 288
ISR with CSFB - Feature Description
Idle-mode Signaling Reduction (ISR) feature allows the UE to move between LTE and 2G/3G without
performing Tracking Area (TA) or Routing Area (RA) updates once it has been activated. A pre-requisite for
ISR activation is that the UE, SGSN, MME, Serving GW and HSS all support ISR. At the first attach to the
network, ISR is not activated. ISR can only be activated when the UE has first been registered in an RA on
2G/3G and then registers in a TA or vice versa.
If the UE first registers on GERAN/UTRAN and then moves into an LTE cell, the UE initiates a TA update
procedure. In the TA update procedure, the SGSN, MME and Serving GW communicate their capabilities to
support ISR, and if all the nodes support ISR, the MME indicates to the UE that ISR is activated in the TAU
accept message.
Circuit-Switched Fallback (CSFB) is an alternative solution to using IMS and SRVCC to provide voice
services to users of LTE. The IMS is not part of the solution, and voice calls are never served over LTE.
Instead, the CSFB relies on a temporary inter-system that switches between LTE and a system where
circuit-switched voice calls can be served.
The ISR feature must be enabled for the CSFB feature to work, the ISR feature is a license controlled feature.
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Call Flows
The LTE terminals 'register' in the circuit switched domain when powered and attaching to LTE. This is
handled through an interaction between the MME and the MSC-Server in the circuit-switched network domain
over the SGs interface.
Consider the following scenarios:
• Voice calls initiated by the mobile user: If the user makes a voice call, the terminal switches from a LTE
system to a system with circuit-switched voice support. Depending on where the UE latches on after
completion of the voice call:
◦The packet-based services that are active on the end-user device at this time are handed over and
continue to run in a system with circuit-switched voice support but with lower data speeds.
OR
◦The packet-based services that are active on the end-user device at this time are suspended until
the voice call is terminated and the terminal switches back to LTE again and the packet services
are resumed.
• Voice calls received by the mobile user: If there is an incoming voice call to an end-user that is currently
attached to the LTE system, the MSC-Server requests a paging in the LTE system for the specific user.
This is done through the SGs interface between the MSC Server and the MME. The terminal receives
the page, and temporarily switches from the LTE system to the system with circuit-switched voice
support, where the voice call is received. Once the voice call is terminated, the terminal switches back
to the LTE system.
Call Flows
To support CS fallback, existing procedures are modified and some additional CS fallback specific procedures
added to the EPS. Additions are done to the "Attach" and "TA update" procedures which activate an interface
called the SGs. This interface is between the MME and MSC. It is used by the MSC to send paging messages
for CS calls to the UE on the LTE system.
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Call Flows
Example of a CS fallback call
Figure 48: CS Fallback Call
Table 21: Steps in a CS fallback call
Step
Description
1.
The MSC receives an incoming voice call and sends a CS page to the MME over a
SGs interface.
2.
The MME uses the TMSI (or IMSI) received from the MSC to find the S-TMSI (which
is used as the paging address on the LTE radio interface).
3.
The MME forwards the paging request to the eNodeB in the TAs where the UE is
registered. The eNodeBs perform the paging procedures in all the cells in the indicated
TAs.
4.
The paging message includes a special CS indicator that informs the UE that the
incoming paging is for a terminating CS call.
5.
On receiving the paging message, the UE performs a service request procedure which
establishes the RRC connection and sends a Service Request to the MME. The Service
Request message includes a special CS Fall-back indicator that informs the MME that
the CS fallback is required.
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Relationships to Other Features
Step
Description
6.
This triggers the MME to activate the bearer context in the eNodeB with an indication
to perform fallback to GERAN or UTRAN.
7.
The eNodeB selects a suitable target cell, by triggering the UE to send measurements
on the neighbour cells, and initiates a handover or cell change procedure. The selection
between handover or cell change procedure is based on the target cell capabilities and
is configured in the eNodeB.
Note
If the target cell is a UTRAN cell, then MME can do subscriber context
transfer using Forward Relocation Req / Rsp / Complete / Complete Ack
messages and set up the radio contexts in UTRAN a-priori. However if the
target cell is GERAN, then the SGSN currently does not support PS handover
procedure and hence transfer of radio context from MME to 2G SGSN through
Fwd reloc req / rsp /complete/complete ack procedure is not possible in the
current release. In this scenario, CSFB is performed through a RRC release
at the eNodeB and then a Suspend Request is sent to the SGSN.
8.
After a handover or cell change procedure, the UE detects the new cell and establishes
a radio connection and sends a page response to the MSC, through the target RAN.
9.
When the page response arrives at the MSC, a normal mobile terminated call setup
continues and CS call is activated towards the UE.
The CS fallback is primarily supports voice calls but it also supports other CS services. In the case of SMS
services the UE need not switch to other radio interfaces. The UE can remain on LTE and still send and receive
SMSes. The SMS messages are tunnelled between the UE and the MSC through the MME NAS signalling
and the SGs interface.
When ISR is activated the UE is simultaneously registered at both SGSN and MME. So any paging for CS
services occurs at both the SGSN and the MME. In a network if ISR is activated for an UE and CSFB is used
in the network, the SGSN has to support additional call flows.
Relationships to Other Features
The CS Fallback feature is inter-works with the Idle Mode Signaling Reduction (ISR) feature. The CS Fallback
feature is primarily for the EPS, but at the SGSN, it plays a role in deciding when the ISR feature should be
activated or de-activated at the SGSN.
Relationships to Other Products
To enable ISR for subscriber peer nodes, the MME and SGW must support ISR functionality.
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How it Works
How it Works
Listed below are the scenarios where ISR with CSFB is impacted by the SGSN, these scenarios are applicable
to both 2G and 3G when ISR is enabled:
1 The ISR is de-activated (by not sending ISR active status indication in RAU Accept message sent to UE)
in the following cases:
• The SGSN will not sent the ISR activated indication at combined RAU/LAU procedure (As per
3GPP TS23.272, section 4.3.5 ,release 11.2)
• When the UE sends a combined RAU and LAU to a S4-SGSN, the SGSN checks the "Combined
EPS/IMSI Attach Capability" bit in the "MS Network Capability" IE received. If that bit indicates
CSFB and/or SMS over SGs is enabled for this UE, then the SGSN de-activates the ISR by not
indicating the "ISR Activated" status in RAU Accept message sent to the UE. The SGSN in a
CSFB/SMS over SGs configuration never indicates "ISR Activated" in combined RAU procedures
for CSFB/SMS over SGs enabled UEs.
2 If CS Paging Indication is received from MME for an ISR activated subscriber, the SGSN pages to the
subscriber indicating that the paging is for a CS call. When a Mobile Terminating call arrives at the
MSC/VLR (via the G-MSC) for a UE that is camped on an E-UTRAN (ISR is active and the SGs interface
is active between MSC and MME), the MSC/VLR sends a Page Request (SGsAP-PAGING-REQUEST)
to the MME.
As ISR is active and the UE is in ECM_IDLE state, the MME forwards the CS paging message received
from the MSC/VLR to the associated SGSN. The MME gets the SGSN information in the regular ISR
activation process. The MME builds a "CS Paging Indication" message, which is a GTPv2 message, from
the SGsAP-PAGING_REQUEST to the correct SGSN. The SGSN receives the CS Paging Indication
message from the MME, and sends paging messages to RNS/BSSs. This information is described in detail
in 3GPP TS 23.060.
3 In Receive and handle "Alert MME Notification" and send "Alert MME "Acknowledge" scenarios.
4 When the SGSN sends an UE Activity Notification message over the S3 interface, if the MME sends an
Alert MME Notification earlier for the same subscriber and the SGSN detects any UE activity (like Iu
connection established and so on).
5 Handling the problem of Mobile Terminated voice calls getting dropped due to NULL SGs or SGs
association at MSC/VLR, when the implicit detach timer expires at MME. In this case, the flag "EMM
Combined UE Waiting" is set at the SGSN, this ensures waiting for a combined procedure (Combined
RAU). A Combined RAU is forced if we receive a normal periodic RAU (non-combined) by sending an
IMSI Detach request to UE. When a MME detaches the UE locally from E-UTRAN (due to PTAU timer
expiry and no contact with UE at E-UTRAN till the implicit detach timer expiry at MME) it sends a Detach
Notification with cause "local detach" to the SGSN. The SGSN sets the "EMM Combined UE Waiting"
flag if UE is CSFB capable and this flag will be reset only after combined RAU is received.
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ISR CSFB Procedures
ISR CSFB Procedures
CS Paging Procedure
The call flow below depicts a CS Paging example:
Figure 49: CS Paging
Table 22: Steps in a CS Paging Procedure
Step
Description
1.
A Mobile Terminating call arrives at MSC/VLR (via the G-MSC) for a UE which is
camped on E-UTRAN.
2.
If the ISR is active and the SGs interface is active between MSC and MME, then the
MSC/VLR sends a Page Request (SGsAP-PAGING-REQUEST) to the MME.
3.
As ISR is active and the UE is in ECM_IDLE state, the MME forwards the CS paging
message received from the MSC/VLR to the associated SGSN. The MME receives
the SGSN information in the regular ISR activation process. The MME builds a "CS
Paging Indication" message, which is a GTPv2 message, from the
SGsAP-PAGING_REQUEST to the correct SGSN.
4.
The SGSN receives the CS Paging Indication message from the MME, and sends
paging messages to RNS/BSSs.
5.
The RNS/BSS forwards the CS Paging Indication message to the UE.
6.
The CS fallback or Cell re-selection process progresses.
7.
Once the process is complete, the UE sends a CS Paging response to the RNS/BSS.
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Step
Description
8.
The RNS/BSS forwards the CS Paging Response to the MSC/VLR.
For detailed information on CS paging procedure refer to 3GPP TS 23.060.
Alert and UE Notification Procedure
The call flow below depicts an Alert and UE Notification scenario:
Figure 50: Alert and UE Notification Procedure 0
1 The MSC/VLR requests the MME to report activity from a specific UE. The MSC/VLR sends a SGsAP
Alert Request (IMSI) message to the MME where the UE is currently attached to an EPS network. On
receiving the SGsAP Alert Request (IMSI) message, the MME sets a Non-EPS Alert Flag (NEAF). If
NEAF is set for an UE, the MME informs the MSC/VLR of the next activity from that UE (and the UE
is both IMSI and EPS attached) and clears the NEAF.
2 If ISR is activated for this UE, an "Alert MME Notification" message (GTPv2) is created based on above
SGs message and sent on the S3 interface by the MME to the associated SGSN, in order to receive a
notification when any activity from the UE is detected.
3 The SGSN sends an "Alert MME Acknowledge" and sets the SSAF flag, the "Alert MME Acknowledge"
is a GTPv2 message to the MME in response to the Alert MME Notification message.
4 If any UE Activity is detected (UE is active, after an Iu connection is established), the SGSN sends a "UE
Activity Notification message" to the MME over the S3 interface.
ISR De-activation Procedure
When the UE wants to perform a combined RAU/LAU, the SGSN verifies the "combined EPS/IMSI attach
capability" bit in MS Network Capability and if it indicates that CSFB and/or SMS over SGs is enabled, then
the SGSN de-activates ISR. The SGSN does not indicate that ISR is activated in the RAU Accept message.
Detach Procedures for CSFB Capable UEs
If the MME clears a subscriber then SGs association with the MSC is closed and leads to a drop of voice calls
from the MSC. To avoid this issue a few changes are done in SGSN to establish the Gs association between
the MSC and the SGSN on ISR de-activation.
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If "Detach Notification" is received from the MME with Detach Type set as "Local Detach" and if the UE
supports EMM Combined procedures then, the SGSN sends an IMSI Detach request to the UE and sets the
"EMM Combined UE Waiting" flag.
If the SGSN then receives a Periodic RAU Request and the flag "EMM Combined UE Waiting" is set, an
IMSI Detach is sent to the UE in order to ensure that next time the UE performs a Combined RAU. This
enables Gs association between the SGSN and the MSC/VLR and the MT voice calls are not lost.
If the SGSN receives a Combined RAU Request when the flag "EMM Combined UE Waiting" is set, then
this flag is cleared and Gs association is activated.
MS Initiated Last PDN De-activation Procedure
The MS initiated last PDN de-activation procedure is listed below:
The SGSN sends a DSR with OI=1, the cause not set to ISR deactivated.
PDP is deleted from the SGW and the PGW.
In SGSN all PDPs are de-activated. The S4 association is cleared.
In SGW all PDPs are de-activated. Both the S4 and S11 associations at the SGW are cleared.
The MME continues to retain the S11 tunnel.
Both the SGSN and MME retain the ISR and S3 tunnel active. The active S3 tunnel serves incoming voice
calls if SGs association is retained at the MME.
7 If MME has a SGs association and if periodic TAU timer from UE expires, the MME performs the following
actions:
1
2
3
4
5
6
• The MME starts an implicit detach timer. If voice call is received at MSC/VLR when this timer is
running then:
1 The MSC/VLR sends a SGs page to the MME.
2 The MME sends an S3 page to the SGSN.
3 The SGSN pages the UE with the "CN Domain Indicator = CS domain", and if the UE responds
to the page by doing a cell re-selection to CS domain, the MSC/VLR stops paging.
4 The voice call is completed.
• If the implicit detach timer expires:
◦The MME sends an EPS Detach Notification (IMSI detach) to the MSC/VLR.
◦The MME sends a Detach Notification with cause "Local detach" to the SGSN (Refer to 3GPP
TS 23.272v10.08, section 5.3.2 point no. 3).
◦If the UE is "combined EPS/IMSI attach capable" (as derived from MS Network capability)
and if ISR is active, the SGSN sends an IMSI detach request to the UE on receiving Detach
Notification with cause "local detach".
◦The SGSN sets a flag called "EMM Combined UE waiting" (Refer to 3GPP TS 23.272v10.08,
section 5.5)
◦If the IMSI detach request reaches the UE, the UE performs a Combined RAU, the "EMM
Combined UE waiting" flag is cleared at the SGSN and Gs association is established between
SGSN and MSC/VLR. ISR is deactivated at the UE.
◦If the IMSI detach request does not reach the UE, then on next signaling from the UE based
on the "EMM Combined UE waiting" flag being set, following action is taken:
If an UE performs a periodic RAU or NAS Service Request, then the UE is forced to do an
IMSI detach so that the UE does a Combined RAU again to establish Gs association.
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Standards Compliance
PGW Initiated Last PDN De-activation Procedure
Listed below are the sequence of events which occur, if an UE is "combined EPS/IMSI attach capable" and
the last PDN is de-activated due to PGW initiated de-activation or HSS initiated de-activation:
1 The SGW forwards the DBR to both the SGSN and the MME.
2 Both MME and SGSN de-activate the PDN, and locally de-activate ISR (Refer to 3GPP TS 23.401 v10.08,
section 5.4.4.1 (Note 2 and 3) and 3GPP TS 23.060 v10.801, section 9.2.4.3B).
3 The MME need not send a Detach Notification to the SGSN.
4 Consider the scenario, where the SGSN is aware that it is a PGW initiated last PDN de-activation, the UE
is "combined EPS/IMSI attach capable" (as derived from MS Network capability) and ISR was active
earlier, the SGSN performs the following actions:
• If the UE is in a PMM-CONNECTED state at the SGSN, then SGSN sends an IMSI detach request.
The SGSN sets a flag called "EMM Combined UE waiting". If the UE receives this IMSI detach
request, it performs a combined RAU into SGSN and at that point the Gs association is established
and the "EMM Combined UE Waiting" flag is cleared by the SGSN.
• If the UE is in an IDLE state at the SGSN, then the SGSN pages the UE to deliver the PDP
de-activation request. If paging fails, the SGSN sets the "EMM Combined UE Waiting" flag. When
this UE performs a combined RAU to SGSN at a later time or attaches to the SGSN, this flag is
cleared.
5 If the UE is in an E-UTRAN coverage area then, the MME detaches the UE and the UE is re-attached to
the network. If the UE is not in an UTRAN/GERAN coverage area, then the SGSN pages the UE prior to
sending IMSI detach. This paging request fails.
6 If the UE does not receive an E-UTRAN detach request or a paging request from the SGSN, and at a later
point if the UE returns to the SGSN with a periodic RAU / NAS Service Request, then the SGSN performs
the following:
• The "EMM Combined UE waiting" flag is set, this forces the UE to perform a IMSI detach so that
the UE does a Combined RAU again to establish a Gs association.
7 If the UE receives the IMSI detach request sent in step (4), the UE performs a Combined RAU to establish
Gs association. On receiving a Combined RAU, the SGSN clears the "EMM Combined UE waiting" flag.
Standards Compliance
The Idle mode signaling reduction complies with the following standards:
• 3GPP TS 23.060, version 10
• 3GPP TS 23.401, version 10
• 3GPP TS 23.272, version 10
• 3GPP TS 29.274, version 10
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Configuring ISR with Circuit Switched Fallback
Configuring ISR with Circuit Switched Fallback
The following commands are used to configure 3G paging cause for CSFB:
config
context context_name
iups-service iups_service_name
rnc id rnc_id
[default | no ] ranap paging-cause-ie mme-signalling paging_cause_value
end
Where:
• The command ranap paging-cause-ie mme-signalling paging_cause_value is used to set the Paging
Cause IE value for paging from MME due to Circuit Switch Fallback (CSFB). Listed below are the
paging cause values which can be set:
◦0 - Terminating conversational call
◦1 - Terminating streaming call
◦2 - Terminating interactive call
◦3 - Terminating background call
◦4 - Terminating low priority signaling
◦5 - Terminating high priority signaling
• The default command resets the specific parameters value to default. In this case it is set to "5 Terminating high priority signaling".
• The no form of the command suppresses the Paging Cause IE so that it is not included in responses to
Paging Requests.
Monitoring and trouble-shooting the CSFB feature
The configuration can be verified by executing the show command show iups-service, the following parameter
is displayed on executing the command:
• MME-Signalling : Terminating Low Priority Signalling (4)
The show command show subscriber sgsn-only full all has been updated to include a display for "SSAF"
and "Emm_combined_ue_waiting" flags. The new parameters are displayed as below:
• SSAF : False
• EMM Combined UE Waiting Flag : False
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Location Services
• Location Services - Feature Description, page 289
• How Location Services Works, page 289
• Configuring Location Services (LCS) on the SGSN, page 294
• Monitoring and Troubleshooting the LCS on the SGSN, page 298
Location Services - Feature Description
The Location Services (LCS) feature enables the EPC MME and the GPRS/UMTS SGSN to use the SLg
(MME) or Lg (SGSN) interface which provides the mechanisms to support specialized mobile location services
for operators, subscribers, and third party service providers. Use of this feature and the SLg/Lg interface is
license controlled.
The location information is reported in standard geographical co-ordinates (longitude and latitude) together
with the time-of-day and the estimated errors (uncertainty) of the location of the UE. For external use, the
location information may be requested by and reported to a client application associated with the UE, or a
client within or attached to the core network. For internal use, the location information can be utilized by the
SGSN for functions such as location assisted handover or to support other features.
Location information is intended to be used for
• location-based charging (e.g., home-location billing, roaming-location billing),
• location-based services (e.g., lawful interception, emergency calls),
• positioning services offered to the subscribers (e.g., mobile yellow pages, navigation applications on
mobiles), and
• by the operator for service provider services such as network planning and enhanced call routing.
How Location Services Works
The SGSN LCS responsibilities center around UE subscription authorization and managing LCS positioning
requests. The LCS functions of the SGSN are related to charging and billing, LCS co-ordination, location
request, authorization and operation of the LCS services.
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Relationship to Other SGSN Functions
When using the Iu interface, before the SGSN can request location information of a target UE from the radio
access network (RAN), an Iu signaling connection must have been established between the SGSN and the
RAN. The SGSN sends a Location Request message to the RAN. The RAN determines the location of the
target UE related to this Iu signaling connection and sends a Location Report to the SGSN over the same Iu
signaling connection. On the Iu interface, only one location request for a geographic location estimate can be
ongoing at any time.
Only one location request can be ongoing at any time.
The operation begins with a LCS Client requesting location information for a UE from the LCS server. The
LCS server will pass the request to the LCS functional entity (SGSN) in the core network. The LCS functional
entitiy (SGSN) in the core network then:
1 verifies that the LCS Client is authorized to request the location of the UE or subscriber
2 verifies that location services are supported by the UE
3 establishes whether it (the MME/SGSN) is allowed to locate the UE or subscriber, for privacy or other
reasons
4 establishes which network element in the radio access network ( GERAN or UTRAN or E-UTRAN )
should receive the Location Request
5 requests the access network (via the A, Gb, Iu or S1 interface) to provide location information for an
identified UE, with indicated QoS
6 receives information about the location of the UE from the Access Network and forward it to the Client
7 sends appropriate accounting information to an accounting function.
Relationship to Other SGSN Functions
The Location Services feature utilizes several of the existing SGSN functionalities:
• Mobility Management module
• MAP Service module
Architecture
The MME is accessible to the Gateway Mobile Location Center (GMLC) via the SLg interface.
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Location Services
Limitations
The SGSN is accessible to the GMLC via the Lg interface.
Figure 51: LCS Architecture
The SGSN informs the HLR/HSS regarding the LCS capabilities of UE in GPRS (2G) or UMTS (3G) networks.
The SGSN may include the IP address of the V-GMLC associated with the SGSN in the
MAP_UPDATE_GPRS_LOCATION message during Attach and ISRAU procedures.
Limitations
Currently, SGSN support is limited to:
1 A single location request at a time for the target UE. Concurrent location requests are not supported.
2 Only Provide Subscriber Location messages with the id as IMSI are supported.
Flows
Flows
Location Services call flows are standards compliant for the SGSN.
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Flows
SGSN
Figure 52: 2G Mobile Terminating Location Request
Figure 53: 3G Mobile Terminating Location Request
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Standards Compliance
Standards Compliance
The SGSN\'s Location Services feature complies with the following standards:
• TS 3GPP 23.271, v9.6.0
• TS 3GPP 24.030, v9.0.0
• TS 3GPP 24.080, v9.2.0
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Configuring Location Services (LCS) on the SGSN
• TS 3GPP 25.413, v9.8.0 (sections 8.19.2 and 8.20.2)
• TS 3GPP 29.002, v9.7.0
Configuring Location Services (LCS) on the SGSN
This section provides a high-level series of steps and the associated configuration examples to configure
Location Services on the 2G or 3G SGSN -- or for both.
The commands could be issued in a different order, but we recommend that you follow the outlined order for
an initial LCS configuration. All listed configuration steps are mandatory unless otherwise indicated.
Important
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Step 7
Step 8
Step 9
For all the required configuration commands to be available and to implement the configuration, the SGSN
must have loaded the license for the Lg interface.
Enable Location Services on the SGSN.
Identify the GMLC (in the MAP service) to which the SGSN connects for LCS access to the external LCS client.
Configure the MAP service\'s M1 timer.
Important
Step 3 is not mandatory but it is
recommended.
Create a location services configuration and associate the MAP service.
Fine-tune LCS configuration per UE by defining LCS-related restrictions.
Associate the location services configuration with the appropriate SGSN - GPRS (2G) service and/or UMTS (3G) service.
Associate the location services configuration with an operator policy.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide.
Verify the configuration for each component by following the instructions provided in the Verifying the Feature
Configuration section.
Enabling LCS
Location Services functionality is enabled globally for the SGSN.
config
sgsn-global
location-services
end
Notes:
• This command enables and \'starts\' LCS on the SGSN.
• This command also enables support for the Lg interface on the SGSN.
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Identifying the GMLC
• Using the \'no\' keyword stops LCS.
Identifying the GMLC
Use the MAP service configuration to identify the GMLC to which the SGSN connects for LCS access to the
external LCS client. We recommend that you also configure the MAP service\'s M1 timer, however, this is
option.
config
context context_name
map-service map_service_name
gmlc { isdn E.164 | point-code point_code } gsn-address ipv4_address [ source-ssn
ssn
]
timeout m1 seconds
end
Notes:
• Only one GMLC can be configured per MAP service.
• SGSN includes the configured GMLC address as the value for the v-GMLC (an optional IE) in
Update-GPRS-Location messages to the HLR. It is possible to configure the SGSN to exclude the GMLC
address in Update-GPRS-Location messages, see Configuring Exclusion of GMLC Address from
Update-GPRS-Location Messages below.
• isdn is the 1-15 digit E.164 number that identifies the GMLC.
• point-code is the address for the GMLC in dotted-decimal ... or decimal SS7 point-code format
• gsn-address is the IPv4 address for the GMLC
• source-ssn optionally identifies the source SSN value to be used.
Configuring Exclusion of GMLC Address from Update-GPRS-Location Messages
By default, the SGSN includes the GMLC address, configured in the MAP service, in all Update-GPRS-Location
(UGL) messages going to the HLR. Some HLRs do not recognize the v_GMLC field or value when it arrives
in the UGL. As a result, the HLRs reject the calls. This prevents roaming-in subscribers from using some
networks where LCS is enabled.
Beginning with Release 19.4, it is possible to configure the SGSN to exclude the GMLC from the UGL
message. This is done with a new keyword, exclude-gmlc , added to the map command in the Call-Contol
Profile configuration mode. Use the following configuration, illustrated below, to exclude the GMLC from
the UGL message:
config
call-control-profile profile_name
map message update-gprs-location exclude-gmlc
end
Notes:
• exclude-gmlc - This keyword configures the SGSN to exclude the GMLC address in the
Update-GPRS-Location (UGL) messages sent to the HLR.
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Creating the Location Service Configuration
• To re-enable the default behavior to include the GMLC address in the map message, enter the following
configuration command:
remove map message update-gprs-location exclude-gmlc
• For information about the other keywords available for the map command, refer to the Command Line
Interface Reference.
Creating the Location Service Configuration
This set of configuration commands creates a location service configuration and associates the MAP service
with the location service. Up to 16 separate location services can be created.
config
context context_name
location-service loc_serv_name
associate map-service map_serv_name
end
Notes:
• The SGSN supports a maximum of 16 location service configuration. It should be noted that this number,
16, is not part of the SGSN\'s service configuration limit of 256.
• Associate the MAP Service configuration in which the GMLC is defined.
Fine-tuning the Location Service Configuration
Fine-tune the location service configuration per UE by defining LCS-related restrictions. The following
commands will be used to configure the LCSN timer (location notification invoke procedures timer).
Configuring the timer value is optional.
config
context context_name
location-service loc_serv_name
timeout lcsn seconds
Notes:
LCSN timer range is 10 - 20 with a default of 15. seconds.
The following command is used to configure the UE available guard timer. Configuring this timer is optional.
config
context context_name
location-service loc_serv_name
timeout ue-available-guard-timer ueagtimer_seconds
Notes:
This timer, set in seconds, is used to guard the packet-switched deferred location request (UE available event)
procedures. It is an integer from 10 to 600. Default is 600.
The following command is used to configure area event invoke procedure timer. Configuring this timer is
optional.
config
context context_name
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Associating the Location Service Config with the SGSN
location-service loc_serv_name
timeout area-event-invoke-timer aietimer_seconds
Notes:
This timer, set in seconds, is used to guard the area event invoke procedure. It is an integer from 10 through
20. Default is 15.
The following command is used to configure periodic event invoke procedure timer. Configuring this timer
is optional.
config
context context_name
location-service loc_serv_name
timeout periodic-event-invoke-timer peitimer_seconds
Notes:
This timer, set in seconds, is used to guard the period location invoke procedure.. It is an integer from 10
through 20. Default is 15.
Associating the Location Service Config with the SGSN
Location service functionality can be associated with either the 3G SGSN via commands in the SGSN Service
configuration mode or with the 2G SGSN via commands in the GPRS Service configuration mode.
The following associates the location service configuration with a 3G SGSN:
config
context context_name
sgsn-service service-name
associate location-service loc_serv_name
Notes:
• To associate with a 2G SGSN, enter the GPRS service configuration mode in place of the SGSN service
configuration mode.
Associating the Location Service Config with an Operator Policy
Location service functionality can be associated with an operator policy to provide granular control.
The following associates the location service configuration with a call-control profile by IMSI and these CLIs
will disable/enable Mobile Terminating, Mobile Originating and/or Network Induced location requests by
access-type.
config
call-control-profile ccprofile_name
lcs-mt { allow | restrict } access-type { gprs | umts }
Notes:
• lcs-mt enables mobile-terminating location requests.
• replace lcs-mt with lcs-mo to enable the mobile-originating location requests, lcs-ni is not supported
by SGSN.
• Default for the 3 lcs commands is allow
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Verifying the LCS Configuration for the SGSN
Verifying the LCS Configuration for the SGSN
View the location service configuration to verify the configurations created for the Location Service
functionality, by using the following commands:
show location-service service { all | name loc_serv_name
View the MAP configuration to verify the MAP configurations created for the Location Service functionality,
by using the following commands:
show map-service { all | name map_serv_name }
View the call-control profile configuration to verify the configurations created for the Location Service
functionality, by using the following commands:
show call-control-profile full name ccprof_name
Monitoring and Troubleshooting the LCS on the SGSN
Use the commands listed below to monitor and/or troubleshoot the operation of the Location Services on the
SGSN.
• show map statistics name map-service-name
• clear map statistics name map-service-name
• show gmm-sm statistics
• show subscribers sgsn-only summary
• show subscribers gprs-only summary
• show location-service service {all | name location-service-name }
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22
LORC Subscriber Overcharging Protection for
S4-SGSN
The SGSN\'s Subscriber Overcharging Protection feature has been enhanced and now extends to the S4-SGSN
to prevent both 2G and 3G subscribers from being overcharged when a loss of radio coverage (LORC) occurs
over the S4 interface.
As part of this functionality, the operator configures all cause codes on the SGSN. If the SGSN receives a
cause code, via Iu/Gb interfaces, that matches one of the cause codes configured on the SGSN, then the
SGSN includes the ARRL (Abnormal Release of Radio Link) bit in the Release Access Bearer Request.
• Feature Description, page 299
• How It Works, page 300
• Configuring Subscriber Overcharging Protection, page 303
Feature Description
Subscriber Overcharging Protection prevents subscribers from being overcharged when a loss of radio coverage
(LORC) occurs.
Important
In order for the Subscriber Overcharge Protection feature to be most effective, the SGSN supports initiation
of Release Access Bearer Request on Iu-Release for all subscribers (even for non-ISR and non-DT cases).
Refer to the section on Release Access Bearer Requests below for details.
LORC Subscriber Overcharge Protection on the S4-SGSN
LORC is standardized in 3GPP release 12.0 specifications. According to 3GPP TS 23.401, the SGSN includes
the ARRL (Abnormal Release of Radio Link) Indication in Release Access Bearer Request messages if the
Iu-Release procedure is due to an abnormal release of the radio link.
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Release Access Bearer Requests
It should be noted that 3GPP has not defined LORC for UMTS / GPRS access in an EPS network. Currently,
it is defined only for E-UTRAN access. However, the SGSN can use the defined 3GPP mechanism to achieve
PDN pause of charging in UMTS / GPRS access as well.
With this feature the S4-SGSN should include the ARRL (Abnormal Release of Radio Link) bit in indication
flags IE of Release Access Bearer Request when Iu-Release occurs due to the cause 'Radio Connection With
UE Lost (46)' in 3G.
Also the S4-SGSN should include the ARRL (Abnormal Release of Radio Link) bit in indication flags IE of
Release Access Bearer Request when Radio Status Bad ia received in 2G.
The operator configures all cause codes on the SGSN so if the SGSN receives a cause code via Iu/Gb interfaces
that matches one of the cause codes configured on the SGSN, then the SGSN includes the ARRL bit in the
Release Access Bearer Request.
Release Access Bearer Requests
3G (UMTS):
Upon RNC failure or Iu-Release, the SGSN preserves non-GBR (i.e., non-guaranteed bit rate) PDPs (interactive
/ background) by default. From release 15.0 onwards, for DT and ISR cases the SGSN supports sending
Release Access Bearer Request on Iu-Release. In accordance with TS 23.060 v11.7.0, the SGSN can optionally
send a Release Access Bearers Request to the S-GW to remove the downlink user plane on S4 for non-DT
and non-ISR subscribers.
As part of this feature, the operator can configure the S4-SGSN to send Release Access Bearer Request on
Iu-Release for non-DT and non-ISR subscribers. For DT and ISR subscribers, Release Access Bearer Initiation
functions as it has done prior to this feature\'s implementation.
2G (GPRS):
Upon Ready-to-Standby, the SGSN preserves non-GBR (i.e., non-guaranteed bit rate) PDPs (interactive /
background) by default. From release 15.0 onwards, for ISR cases the S4-SGSN supports sending Release
Access Bearer Request on Ready-to-Standby state transition. In accordance with 3GPP TS 23.060 v11.7.0,
the SGSN optionally sends a Release Access Bearers Request to the S-GW to remove the downlink user plane
on S4 for non-ISR subscriberes.
As part of this feature, the operator can configure the S4-SGSN to send Release Access Bearer Request on
Ready-to-Standby or Radio Status Bad for non-ISR subscribers. For ISR subscribers, Release Access Bearer
Initiation is independent and functions as it has done prior to this feature\'s implementation.
Relationships
• The S-GW should support receiving ARRL bit on S4 interface.
• For this feature to function effectively, the S-GW and P-GW also be configured to support the "PGW
Pause of Charging" procedure.
How It Works
The S4-SGSN handles LORC-based subscriber overcharging protection functionality in accordance with
3GPP specifications as described below.
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3G Iu-Release Procedure and Overcharge Protection over S4
3G Iu-Release Procedure and Overcharge Protection over S4
The following call flow is derived from section 12.7.3.2 of TS 23.060 v11.7.0 and it illustrates how the
S4-SGSN handles the Iu-Release procedure due to LORC with the overcharging protection functionality
enabled.
Figure 54: Iu-Release and Overcharging Protection on the S4
If the cause in the Iu-Release Request matches with the cause code configured under the LTE Policy and if
overcharge protection is enabled under the SGSN-service, then the S4-SGSN includes ARRL (i.e., Abnormal
Release of Radio Link) bit in the Release Access Bearer Request. For configuration details, refer to the section
on Configuring Subscriber Overcharging Protection
2G Ready-to-Standby State Transition and Overcharge Protection over S4
The following flow is derived from section 8.1.3a of TS 23.060 v11.7.0 and it illustrates how the S4-SGSN
handles the state transiton with regard to the overcharging protection functionality.
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Standards Compliance
When idle mode packet buffering is performed on the S-GW, the SGSN needs to inform the S-GW each time
that the MS changes from Ready state to Standby state. The following figure illustrates the procedure between
the SGSN and the S-GW.
Figure 55: 2G Ready-to-Standby State Transition Using S4
If the BSSGP radio-cause code that is configured by the operator matches with the radio cause code received
in the RADIO STATUS message and if the overcharge protection functionality is enabled under GPRS-service,
then the SGSN includes the ARRL bit in Release Access Bearer Request. For configuration details, refer to
the section on Configuring Subscriber Overcharging Protection.
Standards Compliance
Overcharging protection complies with the following standards:
• TS 23.060 version 11
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Configuring Subscriber Overcharging Protection
• TS 23.401 version 11
• TS 29.274 version 11
• TS 25.413 version 11
• TS 48.018 version 11
Configuring Subscriber Overcharging Protection
Important
In order for the Subscriber Overcharging Protection feature to be most effective, the operator should first
enable sending the Release Access Bearer Request and next configure the cause codes for the SGSN for
matching with received codes which enables the SGSN to include the Abnormal Release of Radio Link
(ARRL) bit in the Release Access Bearer Request.
Important
For details about all the commands listed in the Configuration sections below, refer to the Command Line
Interface Reference, StarOS Release 17.
Important
After creating or modifying the configuration for an S4-SGSN, you must save the configuration and reboot
the S4-SGSN node for the change(s) to take effect.
Enabling Release Access Bearer Request
The operator can control the sending of Release Access Bearer Request on Iu-Release for non-DT and non-ISR
subscribers in 3G and on Ready-to-Standby or Radio-Status-Bad for non-ISR subscribers in 2G.
Use commands similar to those illustrated below to enable sending of the Release Access Bearer Request:
configure
call-control-profile profile_name
release-access-bearer [ on-iu-release | on-ready-to-standby ]
remove release-access-bearer [ on-iu-release | on-ready-to-standby ]
end
Notes:
• on-iu-release: This optional keyword instructs the SGSN to send Release Access Bearer upon Iu-Release
in a 3G network so that Release Access Bearer will be initiated for non-ISR and non-DT subscribers
upon Iu-Release. For ISR and DT subscribers, Release Access Bearer will be initiated unconditionally.
• on-ready-to-standby: This optional keyword instructs the SGSN to send Release Access Bearer on
Ready-to-Standby transition in a 2G network so that Release Access Bearer will be initiated for non-ISR
subscribers on Ready-to-Standby transition. For ISR subscribers, Release Access Bearer will be initiated
unconditionally.
• If no optional keywords are included with the release-access-bearer command, then the S4-SGSN
applies Release Access Bearer for both 2G and 3G networks.
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Configuring the Causes to Include ARRL in Release Access Bearer Request
Configuring the Causes to Include ARRL in Release Access Bearer Request
In support of the subscriber overcharging protection functionality, the operator must configure all cause codes
on the SGSN. If the SGSN receives a cause code via Iu/Gb interfaces that matches one of the cause codes
configured on the SGSN, then the SGSN includes the ARRL (Abnormal Release of Radio Link) bit in the
Release Access Bearer Request.
Configuring the Causes for 2G
Use the following configuration commands to define the cause codes received over the Gb interface for GPRS
2G service (BSSGP) when the SGSN initiates Release Access Bearer Request with ARRL bit set.
configure
lte-policy
cause-code-group group_name protocol bssgp
radio-cause cause_code
end
Notes:
• Under LTE Policy, the maximum number of cause code groups supported is 4. Note that this means that
the total number of cause code groups available across all the services (SGSN+GPRS+MME) is 4.
• group_name: Enter an alphanumeric string up to 16 characters long.
• bssgp:
◦Accesses BSSGP Cause Code Group configuration mode for the commands to define the cause
codes for the 2G service
◦Presents a prompt similar to the following: [local]sgsn-test(bssgp-cause-code)
◦radio-cause: A maximum of 16 BSSGP protocol radio cause codes can be defined per group. This
command, in the new BSSGP Cause Code Group configuration mode, enables the operator to
define multiple cause codes for the 2G service so that
◦if the BSSGP radio cause code configured by the operator matches with the radio cause
received in the Radio Status message, and
◦if the Subscriber Overcharging Protection feature is enabled for 2G service in the
GPRS-Service configuration (see command information above),
◦then the S4-SGSN includes ARRL (Abnormal Release of Radio Link) bit in Release Access
Bearer Request message Initiated on Ready-to-Standby state transition.
◦Under each cause code group the maximum number of cause codes (ranap+bssgp+s1ap) that can
be supported is 16.
◦cause_code : Enter an integer from 0 to 255 to identify a BSSGP protocol radio cause code, as
defined in the Radio Cause section of the 3GPP TS 48.028 specification.
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Configuring the Causes to Include ARRL in Release Access Bearer Request
Note
The SGSN does not support Enhanced Radio Status functionality therefore, the SGSN treats cause code
values 0x03 and 0x04 as "Radio contact lost with MS". Therefore, the valid configurable cause codes
values are 0, 1, and 2.
Configuring the Causes for 3G
Use the following configuration commands to define the cause codes received over the the Iu interface for
UMTS 3G service (RANAP) when the SGSN initiates Release Access Bearer Request with ARRL bit set.
configure
lte-policy
cause-code-group group_name protocol ranap
cause cause_code
end
Notes:
• Under LTE Policy, the maximum number of cause code groups supported is 4. Note that this means that
the total number of cause code groups available across all the services (SGSN+GPRS+MME) is 4.
• group_name: Enter an alphanumeric string up to 16 characters long.
• ranap:
◦Accesses the RANAP Cause Code Group configuration mode for the commands to define the
cause codes for the 3G service
◦Presents a prompt similar to the following: [local]sgsn-test(ranap-cause-code)
◦cause: A maximum of 16 RANAP protocol cause codes can be defined per group. This command,
in the new RANAP Cause Code Group configuration mode, enables the operator to define multiple
cause codes for the 3G service so that
◦if the RANAP cause code configured by the operator matches with the radio cause received
in the Iu-Release Request message, and
◦if the Subscriber Overcharging Protection feature is enabled for 3G service in the
SGSN-Service configuration,
◦then the S4-SGSN includes ARRL (Abnormal Release of Radio Link) bit in Release Access
Bearer Request message Initiated on Ready-to-Standby state transition.
◦Under each cause code group the maximum number of cause codes (ranap+bssgp+s1ap) that can
be supported is 16.
◦cause_code : Enter an integer from 1 to 512 to identify a cause code. Valid options are listed in
3GPP TS 25.413 v11.5.0 (or later version), subsection on Cause in subsection for Radio Network
Layer Related IEs.
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Enabling Subscriber Overcharging Protection on S4
Enabling Subscriber Overcharging Protection on S4
Configuring for 3G
Use commands similar to those illustrated below to
• enable or disable Subscriber Overcharging Protection feature for the S4-SGSN in the 3G network.
• associate a cause code group with the SGSN Service configuration.
configure
context context_name
sgsn-service service_name
s4-overcharge-protection ranap-cause-code-group group_name
no s4-overcharge-protection
end
Notes:
• group_name: Enter an alphanumeric string up to 16 characters long to identify the cause code group.
Important
This CLI does not have any control over Release Access Bearer Initiation. If Release Access Bearer is
going out of the S4-SGSN, the ARRL bit will be included if this CLI is enabled and if LORC (loss of
radio coverage) is detected.
Configuring for 2G
Use commands similar to those illustrated below to
• enable Subscriber Overcharging Protection feature for the S4-SGSN in the 2G network.
• associate a cause code group with the GPRS Service configuration.
configure
context context_name
gprs-service service_name
s4-overcharge-protection bssgp-cause-code-group group_name
end
Notes:
• group_name: Enter an alphanumeric string up to 16 characters long to identify the cause code group.
Important
This CLI does not have any control over release access bearer initiation. If Release Access Bearer is going
out of the S4-SGSN, the ARRL bit will be included if this CLI is enabled and if LORC (loss of radio
coverage) is detected.
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23
MOCN for 2G SGSN
The SGSN has long supported Multi-Operator Core Network (MOCN) network sharing operations for the
3G SGSN. With Release 15.0, the SGSN now supports MOCN operations for 2G scenarios.
Important
The MOCN network sharing functionality now requires a feature license for both 2G and 3G network
sharing scenarios. Contact your Cisco representative for licensing information.
• Feature Description, page 307
• How It Works, page 309
• Configuring 2G MOCN, page 313
• Monitoring and Troubleshooting 2G SGSN MOCN Support, page 316
Feature Description
A Public Land Mobile Network (PLMN) is uniquely identified by the combination of a mobile country code
and a mobile network code (the PLMN-Id). Sharing of radio resource and network nodes requires a PLMN
network to support more than one than one PLMN-Id.
GPP defines two different configurations for supporting network sharing based on the resources being shared.
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Gate Core Network (GWCN) Configuration
Gate Core Network (GWCN) Configuration
In this configuration, the radio access network and some core network services are shared among different
operators. Each operator has its own network node for GGSN, HLR etc, while sharing SGSN and MSC with
the rest of the radio network. The figure below depicts a GWCN configuration.
Figure 56: GWCN Configuration for Network Sharing
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Relationships to Other Features
Multi Operator Core Network (MOCN) Configuration
In this configuration, the radio network is shared among different operators, while each operator maintains
its separate core network. The figure below depicts a MOCN configuration.
Figure 57: MOCN Configuration
Relationships to Other Features
SGSN supports both MOCN and GWCN in 3G. GPRS. The MOCN feature can work with 3G network sharing.
Inter-RAT from 3G to 2G in shared to non-shared area, and non-shared area to shared are supported.
To enable GPRS MOCN, the BSC also needs to support the GPRS MOCN. For "Supporting-MS", the MS
shall have the capability to select the network from the PLMN details shared by the BSC. Currently, the SGSN
supports only "non-supporting MS", thus the MS always selects the common PLMN.
How It Works
Automatic PLMN Selection in Idle Mode
This section briefly describes the normal PLMN selection procedure performed by MS along with modifications
for network sharing.
Whenever MS is switched on or has just returned to network coverage after being out of coverage, it tries to
select a network to register itself and receive network services. Traditionally, each network broadcasts its own
PLMN-Id on common broadcast channels that are visible to all MSs in that area.
The MS starts by scanning for all the available radio networks in that area and creating an Available PLMN
list. It then refers to the Equivalent PLMN list and Forbidden PLMN list (stored on its SIM) to prioritize the
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Automatic PLMN Selection in Idle Mode
Available PLMN list. Once this prioritized PLMN list is available, the MS attempts registration with a PLMN
based on priority.
With network sharing a single radio network is shared by more than one network operator. Information about
the availability of multiple operators must be propagated to the MS so that it can correctly select a home or
equivalent network from all available networks.
To advertise availability of multiple core network operators on a single radio network, broadcast information
has been modified to contain a list of PLMN-Ids representing core network operators sharing the particular
radio network. The traditional PLMN-Id broadcast by a radio network before network sharing support was
available is known as a "common PLMN Id".
An MS that does not support network sharing (a non-supporting MS) sees only the "common PLMN Id",
while an MS supporting network sharing (a supporting MS) is able to see the list of PLMN-Ids along with
"common PLMN Id".
A supporting MS is responsible for selecting an appropriate core network, while the RNC and SGSN will
help select an appropriate core network for a non-supporting MS.
MOCN Configuration with Non-supporting MS
In this scenario, only the radio network is shared by different network operators while each operator manages
its own SGSN and the rest of the core network. The MS does not support network sharing it is unable to
understand the modified broadcast information and would always choose the PLMN based on the advertised
"common PLMN-Id".
The SGSN performs the following steps:
1 Extract the subscriber\'s IMSI.
• If it is available, use IMSI in a BSSGP UL-UNITDATA message.
• For inter-SGSN RAU and a P-TMSI Attach Request, retrieve the IMSI from the old SGSN or the
MS by doing an Identity Procedure.
2 Based on the MCC-MNC from the IMSI, apply roaming control.
3 If the subscriber can be admitted in the SGSN, send a response message (Attach-Accept or RAU-Accept)
with an Redirection-Completed IE via BSSGP UL-UNITDATA.
4 If the subscriber cannot be admitted in the SGSN, send a BSSGP DL-UNITDATA message to the BSC
with a redirection indication flag set containing the reject cause, the attach reject message, and the original
attach request message received from the UE. The IMSI is also included in the message.
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Architecture
Redirection in GERAN with MOCN Configuration
The figure below illustrates the information flow for this configuration.
Figure 58: Information Flow for Redirection in GERAN (PS Domain)
1
Establish the TBF (Temporary Block Flow).
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2
The BSC receives the LLC frame with foreign [or random] TLLI =X.
The BSC works in a Shared RAN MOCN, and, therefore, forwards the message in a BSSGP
ULUNITDATA message with an additional redirect attempt flag set. The flag indicates that
the SGSN shall respond to the attach request with a BSSGP DL-UNITDATA message
providing when relevant a redirection indication flag set to inform the BSC that a redirection
to another CN must to be performed. The selection of a CN node is based on NRI (valid or
invalid) or random selection. The mechanism defined for Gb-Flex in TS 23.236 [8] is used.
3
The SGSN receives the BSSGP UL-UNITDATA message with the redirect attempt flag set.
It then knows it may have to provide the BSC with a redirection indication flag set or a
redirection completed flag set.
4
The SGSN needs the IMSI of the UE retrieves it either from the old SGSN or from the UE
as in this example. By comparing the IMSI with the roaming agreements of the CN operator,
SGSN A discovers that roaming is not allowed or that roaming is allowed but CS/PS
coordination is required. The Attach procedure is aborted.
5
5a) A BSSGP DL-UNITDATA message is sent back to the BSC with a redirection indication
flag set containing the reject cause, the attach reject message, and the original attach request
message received from the UE. The V(U) shall also be included in the message. The IMSI is
also included in the message. The BSC selects a SGSN B in the next step. The already tried
SGSN A is stored in the BSC during the redirect procedure so that the same node is not
selected twice.
5b) The BSC makes a short-lived binding between the TLLI =X and SGSN ID so that it points
to SGSN B.
6
The BSC sends a new BSSGP UL-UNITDATA to the next selected SGSN B with the original
attach request message (for CS/PS coordination the BSSGP UL-UNITDATA may also be
sent back to the first SGSN depending on the outcome of the coordination). Redirect attempt
flag is set and IMSI is included to avoid a second IMSI retrieval from the UE or old SGSN
and to indicate that PS/CS domain coordination has been done in BSC (if enabled in BSC).
The V(U) shall also be included in the message. The SGSN B receiving the message starts
its attach procedure.
7
SGSN B does support roaming for the HPLMN of the IMSI authentication is done and RAN
ciphering is established. The value of V(U) in SGSN-B is set according to the received value
from BSC. Uplink LLC frames are routed to SGSN B despite the NRI of the TLLI=X pointing
to SGSN A.
8
SGSN B updates the HLR and receives subscriber data from HLR Subscriber data allows
roaming, and the SGSN B completes the attach procedure.This includes the assignment of a
new P-TMSI with an NRI that can be used by BSC to route subsequent signalling between
UE and the correct SGSN (Gb-Flex functionality).
9
A BSSGP DL-UNITDATA Attach accept message is sent to BSC with the Redirection
Completed flag set. The BSC knows that the redirect is finished and can forward the Attach
Accept message to the UE and clean up any stored redirect data.
SGSN B is allowed to reset the XID parameter only after the Attach Request is accepted.
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10
The Attach Accept is forwarded to the UE. The UE stores the P-TMSI with the Gb-Flex NRI
to be used for future signalling, even after power off.
11
UE responds with an Attach Complete message (P-TMSI [re-]allocation if not already made
in Attach Accept). The Attach Complete uses the new TLLI. After this, the BSS releases the
binding between TLLI=X and SGSN B.
If the BSC finds no SGSNs to redirect to after receiving a BSSGP DL-UNITDATA message with the
Redirection Indication flag set, it compares the cause code with cause codes from other BSSGP DL-UNITDATA
messages it has previously received for this UE. A cause code ranking is done and the "softest" cause code
is chosen. The corresponding saved Attach Reject message is returned to the UE.
Each CN node that receives a BSSGP UL-UNITDATA, runs its own authentication procedure. This may in
some rare situations cause the UE to be authenticated more than once. However, the trust-model used is that
one CN operator shall not trust an authentication done by another CN operator. This is not an optimal usage
of radio resources, but given the rare occurrence of this scenario, the increased signalling is insignificant.
During the redirect procedure the BSC keeps a timer, which corresponds to the UE timer for releasing the RR
connection (20 seconds). If the BSC when receiving a BSSGP DL-UNITDATA message with the Redirection
Indication flag set finds that there is insufficient time for another redirect, further redirect attempts are stopped
(for this Attach Request message). The UE will repeat its Attach Request four times (each time waiting 15
seconds before it re-establishes the RR connection for another try).
Standards Compliance
Support for 2G MOCN functionality on the SGSN complies with the following standards:
• 3GPP TS 23.251 Network Sharing: Architecture and functional description
• 3GPP TS 40.018 version 10.7.0 Release 10 BSSGP layer specification
• 3GPP TS 44.064 Mobile Station - Serving GPRS Support Node (MS-SGSN) Logical Link Control
(LLC) Layer Specification
• 3GPP TS 24.008 Mobile radio interface Layer 3 specification Core network protocols
Configuring 2G MOCN
For details about the commands listed below, refer to the Cisco ASR 5000 Command Line Interface Reference
for the appropriate release.
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GPRS MOCN Configuration
GPRS MOCN Configuration
gprs-mocn
The SGSN mode gprs-mocn command enables or disables 2G MOCN support.
config
sgsn-global
gprs-mocn
end
Verifying gprs-mocn Configuration
From the Exec mode, run the show sgsn-mode command and look for the line:
Multi Operator Core NW (MOCN)
: Enabled
Common PLMN-Id and List of PLMN Ids Configuration
plmn id
The following command sequence configures the common PLMN-Id and an optional list of dedicated PLMN-Ids
in the GPRS service.
config
context ctxt_name
gprs-service gprs_srvc_name
plmn id mcc mcc_id mnc mnc_id [ network-sharing common-plmn mcc mcc_id mnc mnc_id
[ plmn-list mcc mcc_id mnc mnc_id [ mcc mcc_id mnc mnc_id ] + ] ]
end
Notes:
• + in the syntax above indicates that the mcc/mnc combination can be repeated as often as needed to
define all PLMN-Ids needed in the list.
Verifying plmn id Configuration
From the Exec mode, run the show gprs-service command, including the name keyword to identify the
specific GPRS service you configured above, and check the output for the following lines:
Network Sharing
Common Plmn-id
Local PLMNS:
PLMN
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: <Enabled/Disabled>
: MCC: <mcc_id>, MNC:
<mnc_id>
: MCC: <mcc_id>, MNC:
<mnc_id>
MOCN for 2G SGSN
Network Sharing Configuration
Network Sharing Configuration
network-sharing cs-ps-coordination
Next, the operator should configure cs-ps-coordination checking explicitly for homer or roamer subscribers
and for the failure-code to be sent when the SGSN asks the BSC to perform CS-PS coordination.
The network-sharing command enables or disables the cs-ps coordination check for homer or roamer. It is
also used to set the failure code that will be sent while the SGSN is requesting the BSC to provide CS-PS
coordination.
config
context <ctxt_name>
gprs-service <gprs_srvc_name>
network-sharing cs-ps-coordination [ roamer | homer | failure-code gmm-cause ]
end
Notes: Variations of the network sharing command can be used to adjust the CS-PS configuration.
• [ no ] network-sharing cs-ps-coordination roamer enables/disables the cs-ps-coordination check for
a roamer.
• [ no ] network-sharing cs-ps-coordination homer enables/disables the cs-ps-coordination check for
a homer.
• network-sharing cs-ps-coordination failure-code gmm-cause sets the gmm cause value to be sent
while cs-ps-coordination is required. This setting applies to both homer and roamer.
• default network-sharing cs-ps-coordination sets the cs-ps-coordination parameters to default. By
default, checking for cs-ps-coordination is enabled for homer and roamer. The default failure code is
0xE.
Verifying network-sharing Configuration
From the Exec mode, run the show gprs-service command, including the name keyword, and check the
output for the following lines:
CS/PS Co-ordination homer
: <Enabled/Disabled>
CS/PS Co-ordination roamer
: <Enabled/Disabled>
CS/PS Co-ordination failcode : <valid gmm cause>
network-sharing failure-code
The following command sequence sets the failure code that is used by GPRS MOCN if no failure cause is
available when the SGSN sends an Attach/RAU Reject message
config
context ctxt_name
gprs-service gprs_srvc_name
network-sharing failure-code gmm-cause
end
Default network sharing failure-code is 7.
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Monitoring and Troubleshooting 2G SGSN MOCN Support
Verifying Failure Code Configuration
From the Exec mode, run the show gprs-service name command and look for the following line:
Network-sharing Failure-code : <gmm-cause>
Monitoring and Troubleshooting 2G SGSN MOCN Support
The output generated by the following show commands will assist you in monitoring and troubleshooting 2G
SGSN MOCN support.
show sgsn-mode
From the Exec mode, run the show sgsn-mode command and look for the following line:
Multi Operator Core NW (MOCN)
: <Enabled/Disabled>
This line indicates whether or not MOCN has been enabled.
show gprs-service name
From the Exec mode, run show gprs-service name gprs-service-name and check the output for the following
lines:
CS/PS Co-ordination homer
: <Enabled/Disabled>
CS/PS Co-ordination roamer
: <Enabled/Disabled>
CS/PS Co-ordination failcode : <valid gmm cause>
The above lines display details regarding cs/ps coordination for homer and roamer, as well as the GMM cause
to be sent in the Reject message when cs/ps coordination is required.
Network-sharing Failure-code : <gmm-cause>
The above line displays the GMM cause to be sent as a Reject cause only when no valid cause code was
derived while sending the Reject message. This gmm-cause is used for non-cs/ps coordination Rejects.
Network Sharing
Common Plmn-id
Local PLMNS:
PLMN
: <Enabled/Disabled>
: MCC: <mcc_id>, MNC:
<mnc_id>
: MCC: <mcc_id>, MNC:
<mnc_id>
The above lines display details about the GPRS service with MOCN enabled, including the configured common
PLMN-id and the list of local PLMN Ids.
show gmm-sm statistics verbose
From the Exec mode, run show gmm-sm statistics verbose and look for the following lines:
GPRS MOCN Attach Statistics
Total Redirection Attempts Rcvd:
Redirection attempts rcvd with bsgp imsi:
Redirection attempts rcvd without bssgp imsi:
Total Redirection Completes Sent:
Successful Redirection completes sent:
Failure Redirection completes sent:
Total Redirection Indications Sent:
Illegal PLMN:
Illegal LA:
No roaming:
No gprs PLMN:
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<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
MOCN for 2G SGSN
show gmm-sm statistics verbose
No cell in LA:
CS/PS Coord Rqrd:
Others:
<value>
<value>
<value>
GPRS MOCN RAU Statistics
Total Redirection Attempts Rcvd:
Redirection attempts rcvd with bssgp imsi:
Redirection attempts rcvd without bssgp imsi:
Total Redirection Completes Sent:
Successful Redirection completes sent:
Failure Redirection completes sent:
Total Redirection Indications Sent:
Illegal PLMN:
Illegal LA:
No roaming:
No gprs PLMN:
No cell in LA:
CS/PS Coord Rqrd:
Others:
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
<value>
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show gmm-sm statistics verbose
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CHAPTER
24
MTC Congestion Control
The SGSN\'s MTC (mobile type communications) Congestion Control feature implements General NAS-level
congestion control and APN-based congestion control for both Session Management (SM) and Mobility
Management (MM) in the SGSN. As well, the functionality associated with this feature also provides support
for configuring and sending an Extended T3312 timer value to the MS.
This is an optional licensed feature. Speak with your Cisco Customer Representative for information about
obtaining an MTC Feature license.
• Feature Description, page 319
• How It Works, page 320
• Configuring MTC Congestion Control, page 328
• Monitoring MTC Congestion Control, page 337
Feature Description
Congestion is detected based on various threshold-configurable parameters, such as (but not limited to) system
CPU utilization, system memory utilization, service CPU utilization. This feature enables the operator to
determine the SGSN\'s response to various congestion scenarios.
The MTC Congestion Control functionality gives the operator control over the congestion threshold settings
and the actions taken in response to congestion. The operator defines a set of congestion actions in a
congestion-action-profile. The selected actions are executed when congestion is detected.
Congestion control can be enabled as:
• General congestion control - applicable only for Mobility Management messages.
• APN-based congestion control for Mobility Management
• APN- based congestion control for Session Management
There are three levels of system-detected congestion: critical, major, and minor. The percentage at which
these levels are hit is controlled via threshold configuration.
The operator defines the SGSN\'s congestion response actions for new calls, active calls, and SM-messages
in congestion-action-profiles and association those congestion-action-profiles with the various congestion
level.
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Relationships
In addition to system-detected congestion, the SGSN also provides a management option to trigger congestion.
This option can be useful when testing system readiness and response.
Relationships
Other SGSN Features: Low Access Priority Indicator (LAPI) in S-CDRs. The SGSN allows for the use of
the LAPI bit in S-CDRs of the custom24 dictionary. Use of this functionality is CLI controlled. For details
about this functionality, refer to the GTPP Interface Administration and Reference for StarOS Release 17.
Other Products:While specific operations may vary, MTC Congestion Control functionality is also supported
by the MME. For details, refer to the MME Administration Guide for StarOS Release 17
How It Works
SGSN Congestion Control
The deciding parameter for triggering congestion control in the SGSN will be the overall system CPU utilization,
service CPU utilization, and system memory utilization. This information will be periodically monitored by
the resource manager (ResMgr) which will informed the SGSN\'s IMSIMgr.
Mobility Management (MM) Congestion Control - For congestion control of MM messages, system-detected
congestion is based on
• system CPU utilization,
• service CPU utilization
• system memory utilization
Session Management (SM) Congestion Control - For congestion control of session management messages,
system-detected congestion is based only on system CPU utilization.
The MTC Congestion Control functionality enables the operator to configure different
congestion-action-profiles, which applies at different threshold levels.
APN-level Congestion Control for MM
APN-level congestion control for mobility management (MM) is applied to those UEs that have subscribed
for APNs configured for congestion control.
During system-level congestion, if the chosen congestion-action-profile has the "apn-based" parameter
configured as enabled, then APN-based congestion control is applied.
Once the SGSN receives the subscription for a subscriber, if any of the subscribed APNs are configured for
congestion control, then the call is rejected with a backoff timer value sent to the UE in the Reject message
according to the following scenario:
• A random MM backoff timer (T3346) value, derived from the selected min-max range configured for
that APN, is sent to the UE in Reject messages.
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APN-level Congestion Control for SM
1 The minimum and maximum range for the MM backoff timer value is selected from the APN Profile
configuration.
2 If the timer is not configured at the APN Profile level, then the SGSN takes the MM backoff timer
as configured at either the GPRS or SGSN service level.
3 If timer is not configured at the service level, then the default values (min-15 max-4320) are applied.
• If the subscriber retries Attach when the backoff timer is running, then the SGSN rejects the Attach,
sending the remaining time for backoff in the Reject message.
• If the subscriber retries Attach with a change in signaling priority when the backoff timer is running,
then the SGSN accepts the Attach, based on configuration for example,
1 if Reject is associated with LAPI and APN-based parameters,
2 then subscriber sends a message without LAPI
3 then the Attach is accepted.
• If the subscriber retries Attach while backoff timer is running and the SGSN is not under congestion,
then the backoff timer is cleared and the call Accepted.
• If the subscriber retries Attach after backoff timer expires, and if the SGSN continues under congestion,
then a new backoff timer value is assigned and sent in the Attach Reject message.
APN-level Congestion Control for SM
APN-level congestion control for session management (SM) is applicable to both activation and modification
types of SM messages. Detection of SM APN-based congestion is determined according to system utilization
or O&M (triggered) congestion at any one of three levels: critical, major, minor with the following possible
ropiness:
If congested:
• If the configured response action indicates the low access priority indicator (LAPI), then only SM
messages with LAPI are rejected during congestion. If LAPI is not configured then all SM messages
are rejected.
• A random SM backoff timer (T3396) value, derived from the selected min-max range configured for
that APN, is sent to the UE in Reject messages.
1 The minimum and maximum range for the SM backoff timer value is selected from the APN Profile
configuration.
2 If the timer is not configured at the APN Profile level, then the SGSN takes the SM backoff timer
as configured at either the GPRS or SGSN service level.
3 If timer is not configured at the service level, then the default values (min-15 max-4320) are applied.
• If the UE attempts to retry before expiry of the SM backoff timer and if the SGSN is still congested,
then a new random value is included in the rejection message.
• A UE that is attached as a LAPI device may override its priority for PDN activation / secondary PDP
activation (if the UE is a dual access priority device). SGSN will only consider the value of LAPI received
in PDP Activation message for applying congestion control on activation procedure.
• If a LAPI UE has activated a PDN without LAPI (i.e., the UE is dual access priority capable) but is
sending PDP Modification Request with LAPI bit, then the SGSN will apply congestion control for the
modification procedure if LAPI-based APN congestion control for SM messages is configured.
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Support for the Extended T3312 Timer
• Dual access priority devices can send PDN Activation with LAPI but subsequent SM procedures without
LAPI. In this scenario, SGSN does not apply congestion based on LAPI.
• For LAPI devices, the SGSN sends LAPI indication to the AAA module for inclusion in S-CDRs if the
appropriate GTPP dictionary is configured.
Support for the Extended T3312 Timer
The SGSN supports sending the Extended T3312 timer value for Attach Accept and/or RAU Accept messages
if the MS indicates support for extended periodic timer in the MS Network Feature Support.
Important
The SGSN will not send an Extended T3312 value if offloading is enabled for that subscriber.
For both Gn-SGSN and S4-SGSN, a longer periodic RAU timer can be assigned to the M2M UEs based on
subscription. The Subscribed-Period-RAU-TAU-Timer AVP is supported for the "Subscribed Period TAU/RAU
Timer" via the SGSN\'s S6d interface. The Subscribed Period TAU/RAU Timer value can be included in the
ISD (Insert Subscriber Data) from the HLR or in the ULA (Update Location Answer) from the HSS.
The maximum value for a standard T3312 timer value is 186 minutes and the new Extended T3312 timer
maximum value is 18600 minutes. Using the longer value for routing area updates reduces network load from
periodic RAU signaling.
Important
Now, despite enabling the Extended T3312 timer in the SGSN\'s configuration, the SGSN may be prevented
from sending the Extended T3312 timer value in messages as the SGSN also supports the "Subscribed
Periodic TAU/RAU Timer Withdrawn" flag.
The SGSN also supports the Subscribed Periodic TAU-RAU Timer Withdrawn Flag in MAP DSD messages.
When the flag is set in MAP DSD messages, it indicates to the SGSN that the subscriber no longer has a
subscription for the "subscribed periodic RAU/TAU timer" (Extended T3312 timer) value, so
• the SGSN will delete any subscribed periodic RAU/TAU timer value information when it is received
from the HLR, and
• the SGSN will no longer send Extended T3312 in Attach/RAU Accept messages for that subscriber
even if the sending of the Extended T3312 is configured.
Limitations
The following resources for congestion detection are not yet supported:
• License utilization
• Max session count
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Flows for SGSN Congestion Control
Flows for SGSN Congestion Control
New Call Policy for Congestion
The following flowchart explains how new calls are handled, during congestion, based on configuration.
Figure 59: New Call Handling during Congestion
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Flows for SGSN Congestion Control
Active Call Policy for Congestion
The following flowchart explains how active calls are handled, during congestion, based on configuration.
Figure 60: Active Call Handling during Congestion
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Flows for APN-level Congestion Control for MM
Flows for APN-level Congestion Control for MM
The following flow chart illustrates the APN-level congestion control for mobility management.
Figure 61: APN-level Congestion Control for MM
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Flows for APN-level Congestion Control for SM
Flows for APN-level Congestion Control for SM
The following flow chart illustrates the APN-level congestion control for session management.
Figure 62: APN-level Congestion Control for SM
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Flows for APN-level Congestion Control for SM
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Handling Value for Extended T3312 Timer
Handling Value for Extended T3312 Timer
The following flow chart explains how and when t3312 extended value is sent in Attach and RAU Accepts
Figure 63: Handling Value for Extended T3312 Timer
Standards Compliance
The MTC Congestion Control feature only implements some of the MTC overload control mechanisms defined
by the 3GPP but for those it implements, they are in compliance with the 3GPP TS23.060 R10 specification.
Configuring MTC Congestion Control
This section illustrates the required and optional configuration steps for setting up MTC Congestion Control
on the SGSN.
The following is broken into the following configuration components:
• Enabling Global-level Congestion Control
• Configuring System-detected Congestion Thresholds
• Configuring SGSN Congestion Control
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Enabling Global-level Congestion Control
• Configuring APN-based Congestion Control
• Configuring Extended T3312 Timer
• Configuring Backoff Timers
• Configuring O&M Triggered Congestion
Important
Details for each of the commands listed in the following sections are available in the Command Line
Interface Reference.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Enabling Global-level Congestion Control
The following configuration is mandatory to enable congestion control on the SGSN.
The following configuration accomplishes several tasks, all of which must be performed to enable congestion
control on the SGSN.
1 Enables or disables global-level congestion control for the SGSN and the IMSIMgr.
2 Associates the SGSN\'s congestion-response action-profile with each of the three possible levels of
congestion - critical, major, and minor.
configure
congestion-control
congestion-control policy { critical | major | minor } sgsn-service action-profile action_profile_name
end
Notes:
• sgsn-service: Identifies the StarOS service type in this case, the SGSN (Gn-SGSN and/or S4-SGSN).
• action_profile_name: Enter a string of 1 to 64 alphanumeric characters to identify the
congestion-action-profile to associate with the congestion-control policy. We recommend that you
remember the name(s) that you assign so that you will have them when you actually create and configure
your congestion-action-profiles.
• Repeat the congestion-control policy command as needed to associate one or more
congestion-action-profile(s) with each congestion level.
Verifying the Global-level Congestion Control Configuration
Use the command illustrated below to verify that congestion control has been enabled and to view the SGSN\'s
congestion-control policy with the congestion-action-profile names association with the level of congestion
severity.
The following command is entered from the Exec mode:
[local]SGSN1-NH
show congestion-control configuration
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Configuring System-detected Congestion Thresholds
The following provides a sample of the display generated by the command illustrated above:
[local]R16sgsn-Sim show congestion-control configuration
Congestion-control: enabled
Congestion-control Critical threshold parameters
system cpu utilization:
80
...
...
Congestion-control Policy
...
sgsn-service:
Minor
Action-profile : ActProf6
Configuring System-detected Congestion Thresholds
The following configuration accomplishes several tasks, all of which are optional:
1
2
3
4
Associates utilization threshold(s) with a congestion severity level - critical, major, minor.
Enables detection based on System CPU Usage.
Enables detection based on System Memory Utilization.
Enables detection based on Service Control CPU Utilization
configure
congestion-control threshold system-cpu-utilization { critical | major | minor } threshold_value
congestion-control threshold system-memory-utilization { critical | major | minor } threshold_value
congestion-control threshold service-control-cpu-utilization { critical | major | minor } threshold_value
end
Notes:
• threshold_value: Enter an integer from 1 to 100 to define a percentage threshold value.
• For congestion control of mobility management messages, any of the above parameters can be configured.
• For congestion control of session management messages, only "system-cpu-utilization" is supported.
• At present, only APN-based congestion control is applicable for session management messages.
Verifying System-detected Congestion Thresholds Configuration
Use the command illustrated below to verify thresholds you may have configured with the commands illustrated
above. The display will include a section for Critical threshold parameters, Major threshold parameters, and
Minor threshold parameters. The following display only illustrates samples for Critical threshold parameters.
The following command is entered from the Exec mode:
show congestion-control configuration
The following provides a sample of the display generated by the command illustrated above:
[local]SGSN1-NH
[local]R16sgsn-Sim show congestion-control configuration
Congestion-control: enabled
Congestion-control Critical threshold parameters
system cpu utilization:
80
service control cpu utilization: 80
system memory utilization: 80
message queue utilization: 80
message queue wait time: 5 seconds
port rx utilization: 80
port tx utilization: 80
license utilization: 100
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Configuring SGSN Congestion Control
max-session-per-service utilization: 80
tolerance limit: 10
Notes:
• At this time, you are only setting the values for the first three displayed parameters.
Configuring SGSN Congestion Control
The following configuration is mandatory to enable congestion control on the SGSN.
Important
Remember, congestion control must also be enabled with the congestion-control command in the Global
Configuration mode. The following is not sufficient to enable congestion control on the SGSN.
The following configuration accomplishes several tasks, all of which must be performed to enable congestion
control on the SGSN.
1 Enables or disables SGSN-level congestion control.
2 Creates and configures congestion-action-profiles.
configure
sgsn-global
congestion-control
congestion-action-profile action_profile_name
active-call-policy { rau | service-req } { drop | reject } [ low-priority-ind-ue ]
new-call-policy { drop | reject } [ low-priority-ind-ue ] [ apn-based ]
sm-messages reject [ low-priority-ind-ue ] [ apn-based ]
end
Notes:
• congestion-control: Opens the Congestion-Control configuration mode, in which the congestion control
action-profile can be created.
• congestion-action-profile action_profile_name: Enter a string of 1 to 64 alphanumeric characters to
create or identify a congestion-action-profile and/or to open the Congestion-Action-Profile configuration
mode, which accesses the commands that define the congestion responses for:
◦active calls
◦new calls
◦SM messages
• A maximum of 16 action-profiles can be defined.
• active-call-policy: This command instructs the SGSN to drop or reject any active call messages when
congestion occurs during an active call. The active call instructions in the congestion-action-profile can
be refined to only drop or reject active call messages with LAPI.
• new-call-policy: This command instructs the SGSN to drop or reject any new calls (Attach Request
messages or new Inter SGSN RAU messages) if new call messages are received during congestion. The
new call instructions in the congestion-action-profile can be refined to only drop or reject new call
messages with low access priority indicator (LAPI).
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Configuring APN-based Congestion Control
• sm-messages: This command instructs the SGSN to reject any SM signaling messages (activation or
modification) during congestion. The congestion-action-profile parameter can be refined to only reject
SM signaling messages with LAPI.
Important
For SM congestion to work, the apn-based option must be configured with the
sm-messages reject command .
• rau | service-req : Defines congestion response for Routing Area Update messages or Service Request
messages.
• drop | reject: Defines the congestion response action, drop or reject, to be taken when RAU or Service
Request messages are received during an active call.
• low-priority-ind-ue: Instructs the SGSN to only take defined action if messages include LAPI.
• apn-based: Instructs the SGSN to reject a new call based on the subscribed APN if congestion control
is configured for that APN under an applicable Operator Policy.
• If both the LAPI and APN-based options are included in the action-profile, then the call event will only
be rejected if both conditions are matched.
Verifying the SGSN Congestion Control Configuration
Use the command illustrated below to verify the configuration created with the commands in the Configuring
SGSN Congestion Control section above.
The following command is entered from the Exec mode. NOTE that the entire command must be typed,
tabbing does not function for this command.
show sgsn-mode
The following provides a sample of the display generated by the command illustrated above:
[local]SGSN1-NH
[local]R16sgsn-Sim show sgsn-mode
Congestion Action Profile
------------------------Congestion Action Profile Name:profile1
New Call Policy
:Reject only LAPI devices
Active Call Policy
:
Routing Area Update
:Not configured
Service Request
:Reject
APN Based Congestion Control :
MM messages
:Not configured
SM messages
:Reject
Configuring APN-based Congestion Control
The following configuration associates congestion control functionality with a specific APN so that congestion
responses can be applied per APN.
configure
operator-policy name op_policy_name
apn network-identifier apn_name congestion-control
end
Notes:
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Configuring Extended T3312 Timer
• op_policy_name: Enter a string of 1 to 64 alphanumeric characters to create or identify an operator
policy.
• apn_name: Enter a string of 1 to 63 characters, including dots (.) and dashes (-), to identify a specific
APN network ID.
• congestion-control: Including this keyword associates congestion control functionality with the identified
APN.
• During an Attach Request, new Inter SGSN RAU, or when receiving sm-messages, all subscribed APNs
for mobility management (MM) or selected APNs for session management (SM) will be checked to
determine if any of them is configured for congestion control, in which case the new call or sm-messages
would be rejected.
Verifying the APN-based Congestion Control Configuration
Use the command illustrated below to verify the configuration created with the commands in the Configuring
APN-based Congestion Control section above.
The following is entered from the Exec mode.
show operator-policy full all
The following provides a sample of the display generated by the command illustrated above:
[local]SGSN1-NH
...
APN NI internet.com
APN Profile Name
Congestion-control
...
:
: Yes
Configuring Extended T3312 Timer
The Extended T3312 timer can be configured at two different levels: Call-Control Profile or Service-level
(GPRS or SGSN).
Extended T3312 Timer Values for a 2G GPRS Network
Use the following configuration to enable Extended T3312 timer values in a 2G GPRS network environment.
configure
context context_name
gprs-service service_name
gmm Extended-T3312-timeout { value exT3312_minutes | when-subscribed } [ low-priority-ind-ue
]
end
Notes:
• value : This keyword instructs the SGSN to send the defined Extended T3312 timer value in Attach or
RAU Accept messages to the MS if the subscriber has a subscription for the Extended T3312 timer
(Subscribed Periodic RAU/TAU Timer in ISD) and indicates support for the extended periodic timer
via the MS Network Feature Support.
• exT3312_minutes : Enter an integer from 0 to 18600 to identify the number of minutes for the timeout
default is 186 minutes.
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Configuring Extended T3312 Timer
• when-subcribed: This keyword instructs the SGSN to only send the Extended T3312 period RAU timer
value in Attach or RAU Accept messages if the SGSN receives the timeout value in an ISD (Insert
Subscriber Data) when the MS has indicated support in "MS Network Feature Support".
• low-priority-ind-ue: This keyword instructs the SGSN to include the Extended T3312 timer value only
if the Attach/RAU Request messages include a LAPI (low access priority indicator) in the "MS Device
Properties".
Extended T3312 Timer Values for a 3G GPRS Network
Use the following configuration to enable Extended T3312 timer values in a 3G UMTS network environment.
configure
context context_name
sgsn-service service_name
gmm Extended-T3312-timeout { value exT3312_minutes | when-subscribed } [ low-priority-ind-ue
]
end
Notes:
• value : This keyword instructs the SGSN to send the defined Extended T3312 timer value in Attach or
RAU Accept messages to the MS if the subscriber has a subscription for the Extended T3312 timer
(Subscribed Periodic RAU/TAU Timer in ISD) and indicates support for the extended periodic timer
via the MS Network Feature Support.
• exT3312_minutes : Enter an integer from 0 to 18600 to identify the number of minutes for the timeout
default is 186 minutes.
• when-subcribed: This keyword instructs the SGSN to only send the Extended T3312 period RAU timer
value in Attach or RAU Accept messages if the SGSN receives the timeout value in an ISD (Insert
Subscriber Data) when the MS has indicated support in "MS Network Feature Support".
• low-priority-ind-ue: This keyword instructs the SGSN to include the Extended T3312 timer value only
if the Attach/RAU Request messages include a LAPI (low access priority indicator) in the "MS Device
Properties".
Extended T3312 Timer Values in the Call-Control Profile
(Reminder: a configuration in the Call-Control Profile would override an Extended-T3312-timeout
configuration done for either the GPRS or SGSN services. As well, a Call-Control Profile configuration
enables the operator to fine-tune for Homers and Roamers.)
Use the following configuration to enable Extended T3312 timer values for all subscribers:
configure
call-control-profile profile_name
gmm Extended-T3312-timeout { value exT3312_minutes | when-subscribed } [ low-priority-ind-ue
]
end
Notes:
• value : This keyword instructs the SGSN to send the defined Extended T3312 timer value in Attach or
RAU Accept messages to the MS if the subscriber has a subscription for the Extended T3312 timer
(Subscribed Periodic RAU/TAU Timer in ISD) and indicates support for the extended periodic timer
via the MS Network Feature Support.
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Configuring Backoff Timers
• exT3312_minutes : Enter an integer from 0 to 18600 to identify the number of minutes for the timeout
default is 186 minutes.
• when-subcribed: This keyword instructs the SGSN to only send the Extended T3312 period RAU timer
value in Attach or RAU Accept messages if the SGSN receives the timeout value in an ISD (Insert
Subscriber Data) when the MS has indicated support in "MS Network Feature Support".
• low-priority-ind-ue: This keyword instructs the SGSN to include the Extended T3312 timer value only
if the Attach/RAU Request messages include a LAPI (low access priority indicator) in the "MS Device
Properties".
Verifying the Extended T3312 Configurations
To verify the configuration for the 2G network environment, use the following command:
show gprs-service name service_name
To verify the configuration for the 3G network environment, use the following command:
[local]SGSN1-NH
show sgsn-service name service_name
To verify the configuration for the Extended T3312 in the Call-Control Profile, use the following command:
[local]SGSN1-NH
[local]SGSN1-NH
show call-control-profile full name profile_name
Configuring Backoff Timers
There are two backoff timers and they can each be configured at two different levels: Call-Control Profile or
Service-level (GPRS or SGSN).
• T3346 MM Backoff Timer
• T3349 SM Backoff Time
T3346Timer Values at the Service Level
Use the following configuration to enable T3346 timer values for a 2G GPRS-service or for a 3G SGSN-service.
configure
context context_name
( gprs-service | sgsn-service } service_name
gmm t3346 min minimum_minutes max maximum_minutes
end
Notes:
• minimum_minutes: Enter an integer from 1 to 15 to identify the minimum number of minutes default is
15 minutes.
• maximum_minutes: Enter an integer from 1 to 30 to identify the maximum number of minutes default
is 30 minutes.
• If an Attach Request or RAU Request or Service Request is rejected due to congestion, then the T3346
value will be included in the reject message with GMM cause code 22 (congestion). The MM backoff
timer value sent will be chosen randomly from within the configured T3346 timer value range.
• The timer will be ignored if an Attach Request or RAU Request is received after congestion has cleared.
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Configuring O&M Triggered Congestion
• If T3346 timer value is configured in a Call-Control Profile then that value will override the backoff
timer values defined for this GPRS Service configurations.
T3346Timer Values at the Call-Control Profile Level
Use the following configuration to enable T3346 timer values in a the Call-Control Profile.
configure
call-control-profile ccpolicy_name
gmm t3346 min minimum_minutes max maximum_minutes
end
Notes:
• minimum_minutes: Enter an integer from 1 to 15 to identify the minimum number of minutes default is
15 minutes.
• maximum_minutes: Enter an integer from 1 to 30 to identify the maximum number of minutes default
is 30 minutes.
• If an Attach Request or RAU Request or Service Request is rejected due to congestion, then the T3346
value will be included in the reject message with GMM cause code 22 (congestion). The backoff timer
value sent will be chosen randomly from within the configured T3346 timer value range.
• If T3346 timer value is configured in a Call-Control Profile then it will override the backoff timer values
defined for either the SGSN Service or GPRS Service configurations.
• The timer will be ignored if an Attach Request or RAU Request is received after congestion has cleared.
Verifying the T3346 Configurations
To verify the configuration for the 2G service, use the following command:
show gprs-service name service_name
To verify the configuration for the 3G service, use the following command:
[local]SGSN1-NH
show sgsn-service name service_name
To verify the configuration for the in the Call-Control Profile, use the following command:
[local]SGSN1-NH
[local]SGSN1-NH
show call-control-profile full name profile_name
Configuring O&M Triggered Congestion
Enabling Congestion
For operations and maintenance purposes (e.g., testing), this command triggers a congestion state at the global
level.
sgsn trigger-congestion level { critical | major | minor }
Notes:
• critical | major | minor: Selecting one of the three congestion severity levels indicates the associated
congestion-action-profile to be chosen and applied. Reminder: the profile is associated with the severity
level with the congestion-control policy command.
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Monitoring MTC Congestion Control
Disabling Congestion
For operations and maintenance purposes (e.g., testing), this command clears congestion triggered using the
sgsn trigger congestion command.
sgsn clear-congestion
Notes:
• If the command is applied then the SGSN resumes normal operations and does not apply any congestion
control policy.
Monitoring MTC Congestion Control
The commands and displays illustrated below are additional commands that can be used to monitor the
operations of the MTC Congestion Control functionality.
show session disconnect-reasons
The following disconnect reason pegs calls (Attach and new Inter SGSN RAU) rejected due to APN-based
congestion control. The following display is an example of what you might see when you issue the show
command:
[local]bngnc3 show session disconnect-reasons
Session Disconnect Statistics
Total Disconnects: 1
Disconnect Reason
Num Disc
Percentage
---------------------------------------------------------------------mm-apn-congestion-control
1
100.00000
show congestion-control statistics imsimgr all full
The following illustrates the fields for statistics generated if congestion control is engaged.
show congestion-control statistics imsimgr all full
Current congestion status:
Current congestion Type :
Congestion applied:
Critical Congestion Control Resource Limits
system cpu use exceeded:
service cpu use exceeded:
system memory use exceeded:
SGSN Congestion Control:
MM Congestion Level:
Congestion Resource:
SM Congestion Level:
O&M Congestion Level:
Cleared
None
0 times
None
None
None
None
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show congestion-control statistics imsimgr all full
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CHAPTER
25
Network Requested Secondary PDP Context
Activation
This chapter describes SGSN support for the Network Requested Secondary PDP Context Activation
(NRSPCA) feature.
• Feature Description, page 339
• How It Works, page 340
• Configuring NRSPCA, page 347
• Monitoring and Troubleshooting the NRSPCA Feature, page 348
Feature Description
The SGSN supports Secondary PDP context activation by the network - NRSPCA.
3GPP TS 23.060 specifies two procedures for GGSN-initiated PDP Context Activation:
• Network Requested PDP Context Activation (NRPCA) is supported by SGSN but only for 3G access
• Network Requested Secondary PDP Context Activation (NRSPCA) is now supported by both Gn/Gp
and S4 type SGSNs.
P-GW supports only the NRSPCA procedure. Network requested bearer control, uesed by P-GW and the
SGSN, makes use of the NRSPCA procedure.
Benefits
NRSPCA allows the network to initiate secondary PDP context activation if the network determines that the
service requested by the user requires activation of an additional secondary PDP context.
Network requested bearer control functionality is mandatory in EPC networks, requiring use of NRSPCA.
With this feature S4-SGSN now supports network requested bearer control.
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Relationships to Other Features
Relationships to Other Features
For NRSPCA on Gn/Gp SGSN, the sgtp-service configuration must include common IE flags in GTP messages.
Network requested activation must be enabled in the call-control profile.
NRSPCA must be supported on the GGSN used for the PDP session. SGSN indicates support of NRSPCA
by setting the NRSN flag in the common flags IE of the Create PDP Context Request and the Update PDP
Context Request/Response messages to GGSN.
For S4-SGSN, network requested activation must be enabled in the call-control profile.
How It Works
Gn/Gp SGSN
During PDP Context Activation Procedure the Bearer Control Mode (BSM) is negotiated. BCM is applicable
to all PDP Contexts within the activated PDP Address/APN pair. It is either "MS_only" or "MS/NW".
For "MS/NW" both the MS and the GGSN may request the creation of additional PDP contexts for the PDP
Address/APN pair. The MS uses the Secondary PDP Context Activation Procedure, whereas the GGSN uses
NRSPCA. When BCM is "MS_only", the GGSN does not initiate NRSPCA.
The MS indicates support of Network Requested Bearer control through the Network Request Support UE
(NRSU) parameter. Using the PCO IE during Primary PDP context Activation, NRSU is applicable to all
PDP contexts within the same PDP address/APN pair. The SGSN indicates support of the Network Requested
Bearer control to the GGSN through the Network Request Support Network (NRSN) parameter in common
flags of the Created PDP Context Request during PDP activation.
During a new SGSN RAU, the new SGSN indicates the support by means of the NRSN parameter in Update
PDP Context Request. If common flags are not included in the Update PDP Context Request message, or the
SGSN does not indicate support of the Network Requested Bearer control (NRSN flag is not set), the GGSN,
following a SGSN-Initiated PDP Context Modification (triggered by SGSN change), performs a GGSN-Initiated
PDP Context Modification to change the BCM to "MS-Only" for all PDP-Address/APN-pairs for which the
current BCM is "MS/NW".
When BCM is "MS/NW", the GGSN may trigger activation of secondary PDP context based on local
configuration or on PCRF/PCEF direction.
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Gn/Gp SGSN
Successful Activation for Gn/Gp SGSN
The call flow below illustrates the NRSPCA procedure for a successful activation.
Figure 64: Call Flow: Successful Network Requested Secondary Activation (Gn/Gp)
GGSN initiates secondary PDP activation by sending an Initiate PDP Context Activation Request (linked
NSAPI, requested Qos, TFT, PCO, correlation-Id) to SGSN. The SGSN sends a Requested Secondary PDP
Context Activation (linked Ti, Ti, QoS Requested, TFT, PCO) message to MS. The QoS Requested, TFT and
PCO are transparently passed through the SGSN.
The TFT sent by the GGSN contains the uplink packet filters to be applied at the MS. The GGSN uses the
Correlation-Id is to correlate the subsequent Secondary PDP Context Activation procedure with the Initiate
PDP Context Activation Request. The SGSN includes this correlation-Id in the subsequent Create PDP Context
Request to GGSN.
The MS sends an Activate Secondary PDP Context Request (linked Ti, Ti, NSAPI, PCO, QoS Requested).
Linked Ti, Ti, QoS Requested will be the same as received in a previous message from SGSN. The TFT sent
by the MS will contain the downlink packet filters to be applied at GGSN.
On receiving a successful response (Activate Secondary PDP Context Request), the SGSN sends an Initiate
PDP Context Activation Response with cause as Accepted to the GGSN. Additionally the SGSN sends a
Create PDP Context Request (correlation-Id, linked NSAPI, NSAPI, TFT, PCO) to the GGSN. After the
GGSN responds with a Create PDP Response with cause Accepted, the SGSN completes the procedure by
sending an Activate Secondary PDP Context Accept to the MS.
Unsuccessful Activation for Gn/Gp SGSN
After sending a Requested Secondary PDP Context Activation to the MS, the SGSN starts the T3385 radio
interface retransmission timer. Upon expiry the SGSN re-sends the message with a limit of maximum four
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Gn/Gp SGSN
retries. Upon the fifth expiry, the SGSN releases all allocated resources and sends an Initiate PDP Context
Activation Response to the GGSN with cause as "MS is not GPRS responding".
The MS may choose to reject the Secondary Activation by the network. In such cases, the MS sends a Requested
Secondary PDP Context Activation Reject message with an appropriate cause. The SGSN informs the GGSN
by sending an Initiate PDP Context Activation Response with an appropriate GTP cause mapped from Session
Management (SM) cause. SM-to-GTP cause mapping is listed in the table below.
Table 23: SM-to-GTP Cause Mapping
SM Cause
GTP Cause
26, Insufficient resources
199, No resources available
31, activation rejected, unspecified
197, MS refuses
40, feature not supported
200, Service not supported
41, semantic error in TFT operation
215, semantic error in TFT operation
42, syntactical error in TFT operation
216, syntactical error in TFT operation
43, unknown PDP context
210, Context not found
44, semantic error in packet filter(s)
217, semantic error in packet filter(s)
45, syntactical error in packet filter(s)
218, syntactical error in packet filter(s)
46, PDP context without TFT already activated
221, PDP context without TFT already activated
48, activation rejected, BCM violation
227, BCM violation
95 - protocol error
197, MS refuses
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Gn/Gp SGSN
Upon receipt of an Activate Secondary PDP Context Request or Requested Secondary PDP Context Activation
Reject message, the SGSN stops the T3385 timer.
Figure 65: Call Flow: Unsuccessful Network Requested Secondary Activation (Gn/Gp)
The SGSN will reject the IPCA for the following conditions:
• Subscriber has switched to CS call with cause "GPRS connection suspended".
• Old SGSN RAU/SRNS is ongoing with cause "MS is not GPRS responding".
• IPCA Request is received when BCM is MS only with "BCM mode violation".
• The received Correlation Id is the same as that for another ongoing NRSPCA request for the same bundle
with "Invalid Correlation Id".
• Linked context is in deactivating state (collision case), with "context not found".
• Failure conditions such as "memory allocation failure" are encountered with "No resources available".
• An operator policy restriction causes IPCA Req to be rejected with the configured cause under the
call-control profile.
The following table lists the GTP causes in the Initiate PDP Context Activation Response that will initiate
SGSN rejects.
Table 24: SGSN GTP Reject Causes
GTP Cause
Scenario
225, Invalid Correlation Id
SGSN stores the Correlation Id until completion of Activation.
It rejects the newer NRSPCA activation if the GGSN uses the
same value for two NRSPCA activations (uniquely identified by
sequence number).
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S4-SGSN
GTP Cause
Scenario
199, No resources available
Rejection is due to insufficient memory, the maximum number
of temporary Ti allocations has been reached, or the NRSPCA
procedure collides with a new SGSN RAU procedure.
210, Context not found
Rejection occurs because the PDP bundle identified by a linked
NSAPI does not have any active PDP context.
197, GPRS connection Suspended
MS is in suspended state (CS call active).
196, MS is not GPRS responding
Rejection occurs if the Request Secondary PDP Context
Activation message times out (T3385 timer), no response to
Paging, PPF flag is set to 0, or the NRSPCA procedure collides
with an old SGSN RAU/SRNS, intra-SGSN intersystem/RAT
RAU.
Configured GTP cause, or 200, Service
not supported (default)
Rejection is based on operator policy.
227, BCM violation
IPCA Request is received for a bundle with BCM set to MS only.
S4-SGSN
Successful Activation for S4-SGSN
A P-GW initiates a Secondary PDP activation by sending a Create Bearer Request (linked Bearer Identity,
Bearer Ctx(s), PCO etc) to the S-GW. The S-GW then forwards the request to the S4-SGSN.
The Bearer Contexts contain Bearer level parameters such as TFT, Bearer level QoS, S5/8-U PGW FTeid,
PCO, etc. The S-GW includes the S12-U SGW FTeid or S4-U SGW FTeid depending on whether an S12 or
S4 interface is used. The S4-SGSN sends the Requested Secondary PDP Context Activation (linked Ti, Ti,
Qos Requested, TFT, and PCO) message to MS.
The QoS Requested, TFT and PCO are transparently passed through the S4-SGSN. The MS sends an Activate
Secondary PDP Context Request (linked Ti, Ti, NSAPI, PCO, and QoS Requested). Linked Ti, Ti, Qos
Requested will be as same as received in a previous message from the S4-SGSN. The TFT sent to MS may
contain both the uplink and downlink packet filters.
On receiving a successful response (Activate Secondary PDP Context Request) in UMTS access, the S4-SGSN
establishes RAB with the serving RNC and then sends a Create Bearer Response with Accepted cause to
S-GW. For GPRS access, the RAB establishment is skipped.
The S4-SGSN includes the S4-U SGW FTeid (received in Create Bearer Request) in the Create Bearer
Response to S-GW. S-GW uses this to correlate the Bearer Contexts in Response with that of Request. The
S4-SGSN completes the procedure by sending an Activate Secondary PDP Context Accept to the MS.
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S4-SGSN
A successful Network Requested Secondary PDP Context Activation Procedure is illustrated in the figure
below.
Figure 66: Call Flow: Successful Network Requested Secondary Activation (S4-SGSN)
Unsuccessful Activation for S4-SGSN
After sending a Requested Secondary PDP Context Activation to the MS, the S4-SGSN starts the T3385 radio
interface retransmission timer. Upon expiry the S4-SGSN resends the message, a maximum of four retries.
Upon the fifth expiry, the S4-SGSN releases all allocated resources and sends a Create Bearer Response to
the S-GW/P-GW with cause as "UE not responding".
The MS may choose to reject a Secondary Activation by network. In such cases, the MS sends a Requested
Secondary PDP Context Activation Reject message with an appropriate cause. S4-SGSN informs the SGW/PGW
by sending a Create Bearer Response with an appropriate GTPv2 cause mapped from an SM cause as shown
in the table below.
Table 25: SM Cause to GTPv2 Cause Mapping
SM Cause
GTPv2 Cause
26, Insufficient resources
73, No resources available
31, activation rejected, unspecified
88, UE refuses
40, feature not supported
68, service not supported
41, semantic error in TFT operation
74, semantic error in TFT operation
42, syntactical error in TFT operation
75, syntactic error in TFT operation
43, unknown PDP context
64, context not found
44, semantic error in packet filter(s)
76, semantic error in packet filter(s)
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S4-SGSN
SM Cause
GTPv2 Cause
45, syntactical error in packet filter(s)
77, syntactic error in packet filter(s)
46, PDP context without TFT already activated
85, UE context without TFT already activated
48, activation rejected, BCM violation
88, UE refuses
95 - protocol error
88, UE refuses
Upon receipt of an Activate Secondary PDP Context Request or Requested Secondary PDP Context Activation
Reject message, the S4-SGSN stops the T3385 timer.
The S4-SGSN will reject a Create Bearer Request for the following conditions:
• Subscriber has switched to CS call with cause "Unable to page UE due to suspension".
• A collision occurs with an old SGSN RAU/SRNS with cause "Temporarily rejected due to handover
procedure in progress".
• Linked context is in deactivating state (collision case) with "context not found".
• A failure conditions such as \'memory allocation failure" is encountered with "No resources available".
• Operator policy restriction rejects the CBR Req with the configured cause under the call-control profile.
• PPF flag is cleared with cause "Unable to Page UE".
• Paging failure or Request Secondary PDP activation request times out with cause "UE not responding".
An unsuccessful NRSPCA procedure is illustrated in the figure below.
Figure 67: Call Flow: Unsuccessful Network Requested Secondary Activation (S4-SGSN)
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Limitations
Limitations
Security function during NRSPCA procedure is not supported.
Standards Compliance
The NRSPCA feature complies with the following standards:
• 3GPP TS 23.060 version 10 General Packet Radio Service (GPRS)
• 3GPP TS 24.008 version 10 Mobile radio interface Layer 3 specification Core network protocols
• 3GPP TS 29.060 version 10 General Packet Radio Service (GPRS) GPRS Tunnelling Protocol (GTP)
across the Gn and Gp interface
• 3GPP TS 29.278 version 10 Customized Applications for Mobile network Enhanced Logic (CAMEL)
CAMEL Application Part (CAP) specification for IP Multimedia Subsystems (IMS)
Configuring NRSPCA
Configuration of the NRSPCA feature requires:
• Enabling the common flags IE in SGTP service
• Including the NRSPCA feature in a specific call control profile
Note
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Sample NRSPCA Configuration
The first set of commands enables the common flags IE:
config
context <context-name>
sgtp-service <sgtp-service-name>
gtpc send common-flags
end
The second set of commands includes a new keyword (secondary) to configure NRSPCA in a call control
profile.
config
call-control-profile <profile_name>
network-initiated-pdp-activation secondary access-type <gprs|umts> { all failure-code
<failure_code> | location-area-list instance <instance> failure-code <failure_code> }
end
NOTES:
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Verifying the NRSPCA Configuration
• remove added to the command disables NRSPCA by removing the network-initiated-pdp-activation
definition from the configuration.
• There is no default form of the command.
Verifying the NRSPCA Configuration
show sgtp-service name <sgtp-service-name>
Service name
Service-Id
Context
Status
:
:
:
:
<sgtp-service-name>
3
source
STARTED
Sending RAB Context IE
Sending Common Flags IE
Sending Target Identification Preamble
: Enabled
: Enabled
: Disabled
show call-control-profile full name <cc-profile-name>
Call Control Profile Name = <cc-profile-name>
Accounting Mode (SGW)
Accounting stop-trigger (SGW)
UMTS
UMTS
GPRS
GPRS
GPRS
GPRS
UMTS
UMTS
UMTS
UMTS
SRNS
: None
: Not configured
Secondary PDP Context Activation All
: Allow
PDP Context Activation All Failure Code
: 8
Nw Init Primary PDP Context Activation All
: Allow
Nw Init Primary PDP Ctxt Activation All Failure Code : 200
Nw Init Secondary PDP Context Activation All
: Allow
Nw Init Secondary PDP Ctxt Activation All Failure Code : 200
Nw Init Primary PDP Context Activation All
: Allow
Nw Init Primary PDP Ctxt Activation All Failure Code : 200
Nw Init Secondary PDP Context Activation All
: Allow
Nw Init Secondary PDP Ctxt Activation All Failure Code : 200
Intra All
: Allow
Monitoring and Troubleshooting the NRSPCA Feature
• The show subscriber sgsn-only/gprs-only full command indicates whether or not the Secondary PDP
context was network initiated. The last received BCM from the GGSN (applicable for Gn/Gp only) is
also be displayed.
• Two new disconnect reasons have been introduced:
◦sgsn-nrspca-actv-rej-by-ms MS sends a Request Secondary PDP Context Activation Reject message
◦sgsn-nrspca-actv-rej-by-sgsn For all other cases where NRSPCA context activation does not
complete successfully
• Additional counters have been added to session management statistics in the output of the show gmm-sm
statistics command to represent the session management messages used by NRSPCA. Similarly, counters
have been added to the tunnel management statistics in the output of the show sgtpc statistics command.
These counters are described in the next section.
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NRSPCA show Commands
• For NRSPCA activation failures, the Abort statistics in the verbose mode of the show gmm-sm statistics
or show gmm-sm statistics sm-only command outputs provide reasons for the failure. The various
counters are described in next section.
• Network initiated flag in SCDRs will be set for NRSPCA PDP contexts. Note that network initiated flag
is present in only a few dictionaries, such custom24, custom13, and custom6.
NRSPCA show Commands
The following show commands are available in support of the NRSPCA feature:
• show gmm-sm statistics sm-only displays the Session Management messages exchanged for NRSPCA
activation.
• show sgtpc statistics displays the GTPC messages exchanged for NRSPCA activation.
• show subscribers sgsn-only/gprs-only full indicates whether or not the Secondary PDP context was
network initiated. Displays the last received BCM from the GGSN (applicable for Gn/Gp only).
show gmm-sm statistics sm-only
The following counters are included in the show gmm-sm statistics sm-only command output to support the
NRSPCA feature. For detailed descriptions of these statistics, refer to the ASR 5x00 Statistics and Counters
Reference.
Table 26: NRSPCA SM Statistics
NRSPCA SM Statistics
Activate Context Request
Actv-Request-Nrspca
3G-Actv-Request-Nrspca
2G-Actv-Request-Nrspca
Activate Context Request Retransmitted
3G-Secondary-Actv-Drop-Nrspca
2G-Secondary-Actv-Drop-Nrspca
Activate Context Accept
Actv-Accept-Nrspca
3G-Actv-Accept-Nrspca
2G-Actv-Accept-Nrspca
Activate Context Reject
Actv-Reject-Nrspca
3G-Actv-Reject-Nrspca
2G-Actv-Reject-Nrspca
Network Initiated Secondary Activation Aborted (verbose only)
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NRSPCA show Commands
NRSPCA SM Statistics
3G-NRSPCA-Abort-GTP-Suspend
2G-NRSPCA-Abort-GTP-Suspend
3G-NRSPCA-Abort-Handoff
2G-NRSPCA-Abort-Handoff
3G-NRSPCA-Abort-Max-Retry-Attempts
2G-NRSPCA-Abort-T3385-Expiry
3G-NRSPCA-Abort-Paging-Expiry
2G-NRSPCA-Abort-Paging-Expiry
3G-NRSPCA-Abort-Linked-Ctx-Deactv
2G-NRSPCA-Abort-Linked-Ctx-Deactv
3G-NRSPCA-Abort-Linked-Ctx-Detach
2G-NRSPCA-Abort-Linked-Ctx-Detach
3G-NRSPCA-Abort-Inter-RAT-Handoff
2G-NRSPCA-Abort-Inter-RAT-Handoff
3G-NRSPCA-Abort-Iu-release
2G-NRSPCA-Abort-Intra-RAU
3G-NRSPCA-Abort-SRNS-Handoff
2G-NRSPCA-Abort-Ready-Tmr-Expiry
3G-NRSPCA-Abort-Intra-RAU
2G-NRSPCA-Abort-Radio-Status
3G-NRSPCA-Abort-Intra-SRNS
2G-NRSPCA-Abort-BVC-Block-Or-Reset
3G-NRSPCA-Abort-RAB-Failure
3G-NRSPCA-Abort-Ctx-Deactv
Request Secondary Pdp Context Activation
Total-Request-Sec-Pdp-Ctxt-Req
3G-Request-Sec-Pdp-Ctxt-Req
2G-Request-Sec-Pdp-Ctxt-Req
Retransmission
Total-Request-Sec-Pdp-Ctxt-Req
3G-Request-Sec-Pdp-Ctxt-Req
2G-Request-Sec-Pdp-Ctxt-Req
Request Secondary Pdp Context Activation Reject
Total-Request-Sec-Pdp-Ctxt-Reject
3G-Request-Sec-Pdp-Ctxt-Reject
2G-Request-Sec-Pdp-Ctxt-Reject
Request Secondary Pdp Context Activation Denied (verbose only)
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NRSPCA show Commands
NRSPCA SM Statistics
3G-Insufficient Resources
2G-Insufficient Resources
3G-Actv Rej Unspecified
2G-Actv Rej Unspecified
3G-Feature Not Supported
2G-Feature Not Supported
3G-Sem Err in TFT OP
2G-Sem Err in TFT OP
3G-Syntactic Err in TFT OP
2G-Syntactic Err in TFT OP
3G-Unknown Ctx
2G-Unknown Ctx
3G-Sem Err in Pkt Filter
2G-Sem Err in Pkt Filter
3G-Syntactic Err in Pkt Filter
2G-Syntactic Err in Pkt Filter
3G-Ctx No-Tft Already Activated
2G-Ctx No-Tft Already Activated
3G-Actv Rej BCM violation
2G-Actv Rej BCM violation
3G-Proto Err Unspecified
2G-Proto Err Unspecified
Request Secondary Pdp Context Activation Rejects Dropped
3G-Request-Sec-Pdp-Ctxt-Rej-Dropped
2G-Request-Sec-Pdp-Ctxt-Rej-Dropped
Request Secondary Pdp Context Activation Aborted
3G-NRSPCA-Abort-Subs-Detach
2G-NRSPCA-Abort-Subs-Detach
3G-NRSPCA-Abort-Linked-Ctx-Deactv
2G-NRSPCA-Abort-Linked-Ctx-Deactv
3G-NRSPCA-Abort-Max-Retry-Attempts
2G-NRSPCA-Abort-Max-Retry-Attempts
3G-NRSPCA-Abort-Paging-Expiry
2G-NRSPCA-Abort-Paging-Expiry
3G-NRSPCA-Abort-Subs-Suspend
2G-NRSPCA-Abort-Subs-Suspend
3G-NRSPCA-Abort-Handoff
2G-NRSPCA-Abort-Handoff
3G-NRSPCA-Abort-Inter-RAT-Handoff
2G-NRSPCA-Abort-Inter-RAT-Handoff
3G-NRSPCA-Abort-Intra-RAU
2G-NRSPCA-Abort-Intra-RAU
3G-NRSPCA-Abort-Iu-release
2G-NRSPCA-Abort-Ready-Tmr-Expiry
3G-NRSPCA-Abort-SRNS-Handoff
2G-NRSPCA-Abort-Radio-Status
3G-NRSPCA-Abort-Intra-SRNS
2G-NRSPCA-Abort-BVC-Block-Or-Reset
3G-NRSPCA-Abort-RAB-Failure
3G-NRSPCA-Abort-Ctx-Deactv
Secondary Pdp Context Activation Request Ignored (verbose only)
Total-Actv-Request-Nrspca-Ignored
3G-Actv-Request-Nrspca-Ignored
2G-Actv-Request-Nrspca-Ignored
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NRSPCA show Commands
show sgtpc statistics
The following counters are included in the show sgtpc statistics command output to support the NRSPCA
feature. For detailed descriptions of these statistics, refer to the ASR 5x00 Statistics and Counters Reference.
Table 27: NRSPCA SGTPC Statistics
NRSPCA SGTC Statistics
Initiate PDP Context Activation Request
Total IPCA Req
Initial IPCA Req
Retrans IPCA Req
Initiate PDP Context Activation Response:
Total Accepted
Initial IPCA Rsp
Retrans IPCA Rsp
Total Denied
Initial IPCA Rsp
Retrans IPCA Rsp
Initiate PDP Context Activation Response Not Sent (verbose only)
Linked PDP deact coll
Retrans IPCA Req bef MS rsp
Initiate PDP Context Activation Request Denied (verbose only)
IPCA Req Denied
No Resources Available
Service Not Supported
System Failure
Mandatory IE Incorrect
Mandatory IE Mis
Optional IE Incorrect
Invalid Message Format
Context not Found
Semantic Error in TFT
Syntactic Error in TFT
Semantic Error in Pkt Fltr
Syntactic Error in Pkt Fltr
MS Not GPRS Responding
MS Refuses
Invalid Correlation Id
PDP without TFT already Active
BCM Violation
MS GPRS Suspended
Unknown cause
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26
Operator Policy
The proprietary concept of an operator policy, originally architected for the exclusive use of an SGSN, is
non-standard and currently unique to the ASR 5x00. This optional feature empowers the carrier with flexible
control to manage functions that are not typically used in all applications and to determine the granularity
of the implementation of any operator policy: to groups of incoming calls or to simply one single incoming
call.
The following products support the use of the operator policy feature:
• MME (Mobility Management Entity - LTE)
• SGSN (Serving GPRS Support Node - 2G/3G/LTE)
• S-GW (Serving Gateway - LTE)
This document includes the following information:
• What Operator Policy Can Do, page 353
• The Operator Policy Feature in Detail, page 354
• How It Works, page 358
• Operator Policy Configuration, page 359
• Verifying the Feature Configuration, page 365
What Operator Policy Can Do
Operator policy enables the operator to specify a policy with rules governing the services, facilities and
privileges available to subscribers.
A Look at Operator Policy on an SGSN
The following is only a sampling of what working operator policies can control on an SGSN:
• APN information included in call activation messages are sometimes damaged, misspelled, missing. In
such cases, the calls are rejected. The operator can ensure calls aren't rejected and configure a range of
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A Look at Operator Policy on an S-GW
methods for handling APNs, including converting incoming APNs to preferred APNs and this control
can be used in a focused fashion or defined to cover ranges of subscribers.
• In another example, it is not unusual for a blanket configuration to be implemented for all subscriber
profiles stored in the HLR. This results in a waste of resources, such as the allocation of the default
highest QoS setting for all subscribers. An operator policy provides the opportunity to address such
issues by allowing fine-tuning of certain aspects of profiles fetched from HLRs and, if desired, overwrite
QoS settings received from HLR.
A Look at Operator Policy on an S-GW
The S-GW operator policy provides mechanisms to fine tune the behavior for subsets of subscribers. It also
can be used to control the behavior of visiting subscribers in roaming scenarios by enforcing roaming agreements
and providing a measure of local protection against foreign subscribers.
The S-GW uses operator policy in the SGW service configuration to control the accounting mode. The default
accounting mode is GTPP, but RADIUS/Diameter and none are options. The accounting mode value from
the call control profile overrides the value configured in SGW service. If the accounting context is not
configured in the call control profile, it is taken from SGW service. If the SGW service does not have the
relevant configuration, the current context or default GTPP group is assumed.
The Operator Policy Feature in Detail
This flexible feature provides the operator with a range of control to manage the services, facilities and
privileges available to subscribers.
Operator policy definitions can depend on factors such as (but not limited to):
• roaming agreements between operators,
• subscription restrictions for visiting or roaming subscribers,
• provisioning of defaults to override standard behavior.
These policies can override standard behaviors and provide mechanisms for an operator to circumvent the
limitations of other infrastructure elements such as DNS servers and HLRs in 2G/3G networks.
By configuring the various components of an operator policy, the operator fine-tunes any desired restrictions
or limitations needed to control call handling and this can be done for a group of callers within a defined IMSI
range or per subscriber.
Re-Usable Components - Besides enhancing operator control via configuration, the operator policy feature
minimizes configuration by drastically reducing the number of configuration lines needed. Operator policy
maximizes configurations by breaking them into the following reusable components that can be shared across
IMSI ranges or subscribers:
• call control profiles
• IMEI profiles (SGSN only)
• APN profiles
• APN remap tables
• operator policies
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Call Control Profile
• IMSI ranges
Each of these components is configured via a separate configuration mode accessed through the Global
Configuration mode.
Call Control Profile
A call control profile can be used by the operator to fine-tune desired functions, restrictions, requirements,
and/or limitations needed for call management on a per-subscriber basis or for groups of callers across IMSI
ranges. For example:
• setting access restriction cause codes for rejection messages
• enabling/disabling authentication for various functions such as attach and service requests
• enabling/disabling ciphering, encryption, and/or integrity algorithms
• enabling/disabling of packet temporary mobile subscriber identity (P-TMSI) signature allocation (SGSN
only)
• enabling/disabling of zone code checking
• allocation/retention priority override behavior (SGSN only)
• enabling/disabling inter-RAT, 3G location area, and 4G tracking area handover restriction lists (MME
and S-GW only)
• setting maximum bearers and PDNs per subscriber (MME and S-GW only)
Call control profiles are configured with commands in the Call Control Profile configuration mode. A single
call control profile can be associated with multiple operator policies
For planning purposes, based on the system configuration, type of packet services cards, type of network (2G,
3G, 4G, LTE), and/or application configuration (single, combo, dual access), the following call control profile
configuration rules should be considered:
• 1 (only one) - call control profile can be associated with an operator policy
• 1000 - maximum number of call control profiles per system (e.g., an SGSN).
• 15 - maximum number of equivalent PLMNs for 2G and 3G per call control profile
◦15 - maximum number of equivalent PLMNs for 2G per ccprofile.
◦15 - maximum number of supported equivalent PLMNs for 3G per ccprofile.
• 256 - maximum number of static SGSN addresses supported per PLMN
• 5 - maximum number of location area code lists supported per call control profile.
• 100 - maximum number of LACs per location area code list supported per call control profile.
• unlimited number of zone code lists can be configured per call control profile.
• 100 - maximum number of LACs allowed per zone code list per call control profile.
• 2 - maximum number of integrity algorithms for 3G per call control profile.
• 3 - maximum number of encryption algorithms for 3G per call control profile.
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APN Profile
APN Profile
An APN profile groups a set of access point name (APN)-specific parameters that may be applicable to one
or more APNs. When a subscriber requests an APN that has been identified in a selected operator policy, the
parameter values configured in the associated APN profile will be applied.
For example:
• enable/disable a direct tunnel (DT) per APN. (SGSN)
• define charging characters for calls associated with a specific APN.
• identify a specific GGSN to be used for calls associated with a specific APN (SGSN).
• define various quality of service (QoS) parameters to be applied to calls associated with a specific APN.
• restrict or allow PDP context activation on the basis of access type for calls associated with a specific
APN.
APN profiles are configured with commands in the APN Profile configuration mode. A single APN profile
can be associated with multiple operator policies.
For planning purposes, based on the system configuration, type of packet processing cards and 2G, 3G, 4G,
and/or dual access, the following APN profile configuration rules should be considered:
• 50 - maximum number of APN profiles that can be associated with an operator policy.
• 1000 - maximum number of APN profiles per system (e.g., an SGSN).
• 116 - maximum gateway addresses (GGSN addresses) that can be defined in a single APN profile.
IMEI-Profile (SGSN only)
The IMEI is a unique international mobile equipment identity number assigned by the manufacturer that is
used by the network to identify valid devices. The IMEI has no relationship to the subscriber.
An IMEI profile group is a set of device-specific parameters that control SGSN behavior when one of various
types of Requests is received from a UE within a specified IMEI range. These parameters control:
• Blacklisting devices
• Identifying a particular GGSN to be used for connections for specified devices
• Enabling/disabling direct tunnels to be used by devices
IMEI profiles are configured with commands in the IMEI Profile configuration mode. A single IMEI profile
can be associated with multiple operator policies.
For planning purposes, based on the system configuration, type of packet processing cards, type of network
(2G, 3G, 4G, LTE), and/or application configuration (single, combo, dual access), the following IMEI profile
configuration rules should be considered:
• 10 - maximum number of IMEI ranges that can be associated with an operator policy.
• 1000 - maximum number of IMEI profiles per system (such as an SGSN).
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APN Remap Table
APN Remap Table
APN remap tables allow an operator to override an APN specified by a user, or the APN selected during the
normal APN selection procedure, as specified by 3GPP TS 23.060. This atypical level of control enables
operators to deal with situations such as:
• An APN is provided in the Activation Request that does not match with any of the subscribed APNs
either a different APN was entered or the APN could have been misspelled. In such situations, the SGSN
would reject the Activation Request. It is possible to correct the APN, creating a valid name so that the
Activation Request is not rejected.
• In some cases, an operator might want to force certain devices/users to use a specific APN. For example,
all iPhone4 users may need to be directed to a specific APN. In such situations, the operator needs to
be able to override the selected APN.
An APN remap table group is a set of APN-handling configurations that may be applicable to one or more
subscribers. When a subscriber requests an APN that has been identified in a selected operator policy, the
parameter values configured in the associated APN remap table will be applied. For example, an APN remap
table allows configuration of the following:
• APN aliasing - maps incoming APN to a different APN based on partial string match (MME and SGSN)
or matching charging characteristic (MME and SGSN).
• Wildcard APN - allows APN to be provided by the SGSN when wildcard subscription is present and
the user has not requested an APN.
• Default APN - allows a configured default APN to be used when the requested APN cannot be used for
example, the APN is not part of the HLR subscription.
APN remap tables are configured with commands in the APN Remap Table configuration mode. A single
APN remap table can be associated with multiple operator policies, but an operator policy can only be associated
with a single APN remap table.
For planning purposes, based on the system configuration, type of packet processing cards, type of network
(2G, 3G, 4G, LTE), and/or application configuration (single, combo, dual access), the following APN remap
table configuration rules should be considered:
• 1 - maximum number of APN remap tables that can be associated with an operator policy.
• 1000 - maximum number of APN remap tables per system (such as an SGSN).
• 100 - maximum remap entries per APN remap table.
Operator Policies
The profiles and tables are created and defined within their own configuration modes to generate sets of rules
and instructions that can be reused and assigned to multiple policies. An operator policy binds the various
configuration components together. It associates APNs, with APN profiles, with an APN remap table, with
a call control profile, and/or an IMEI profile (SGSN only) and associates all the components with filtering
ranges of IMSIs.
In this manner, an operator policy manages the application of rules governing the services, facilities, and
privileges available to subscribers.
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IMSI Ranges
Operator policies are configured and the associations are defined via the commands in the Operator Policy
configuration mode.
The IMSI ranges are configured with the command in the SGSN-Global configuration mode.
For planning purposes, based on the system configuration, type of packet processing cards, type of network
(2G, 3G, 4G, LTE), and/or application configuration (single, combo, dual access), the following operator
policy configuration rules should be considered:
• 1 maximum number of call control profiles associated with a single operator policy.
• 1 maximum number of APN remap tables associated with a single operator policy.
• 10 maximum number of IMEI profiles associated with a single operator policy (SGSN only)
• 50 maximum number of APN profiles associated with a single operator policy.
• 1000 maximum number of operator policies per system (e.g., an SGSN) this number includes the single
default operator policy.
• 1000 maximum number of IMSI ranges defined per system (e.g., an SGSN).
Important
SGSN operator policy configurations created with software releases prior to Release 11.0 are not forward
compatible. Such configurations can be converted to enable them to work with an SGSN running Release
11.0 or higher. Your Cisco Account Representative can accomplish this conversion for you.
IMSI Ranges
Ranges of international mobile subscriber identity (IMSI) numbers, the unique number identifying a subscriber,
are associated with the operator policies and used as the initial filter to determine whether or not any operator
policy would be applied to a call. The range configurations are defined by the MNC, MCC, a range of MSINs,
and optionally the PLMN ID. The IMSI ranges must be associated with a specific operator policy.
IMSI ranges are defined differently for each product supporting the operator policy feature.
How It Works
The specific operator policy is selected on the basis of the subscriber's IMSI at attach time, and optionally the
PLMN ID selected by the subscriber or the RAN node's PLMN ID. Unique, non-overlapping, IMSI + PLMN-ID
ranges create call filters that distinguish among the configured operator policies.
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Operator Policy Configuration
The following flowchart maps out the logic applied for the selection of an operator policy:
Figure 68: Operator Policy Selection Logic
Operator Policy Configuration
This section provides a high-level series of steps and the associated configuration examples to configure an
operator policy. By configuring an operator policy, the operator fine-tunes any desired restrictions or limitations
needed to control call handling per subscriber or for a group of callers within a defined IMSI range.
Most of the operator policy configuration components are common across the range of products supporting
operator policy. Differences will be noted as they are encountered below.
Important
After creating or modifying the S4-SGSN's configuration, you must save the configuration and reboot the
node for the change(s) to take effect.
Important
This section provides a minimum instruction set to implement operator policy. For this feature to be
operational, you must first have completed the system-level configuration as described in the System
Administration Guide and the service configuration described in your product's administration guide.
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Call Control Profile Configuration
The components can be configured in any order. This example begins with the call control profile:
Step 1
Step 2
Create and configure a call control profile, by applying the example configuration presented in the Call Control Profile
Configuration section.
Create and configure an APN profile, by applying the example configuration presented in the APN Profile Configuration
section.
Note
It is not necessary to configure both an APN profile and an IMEI profile. You can associate either type of profile
with a policy. It is also possible to associate one or more APN profiles with an IMEI profile for an operator
policy (SGSN only).
Step 3
Create and configure an IMEI profile by applying the example configuration presented in the IMEI Profile Configuration
section (SGSN only).
Step 4
Create and configure an APN remap table by applying the example configuration presented in the APN Remap Table
Configuration section.
Step 5
Create and configure an operator policy by applying the example configuration presented in the Operator Policy
Configuration section.
Configure an IMSI range by selecting and applying the appropriate product-specific example configuration presented
in the IMSI Range Configuration sections below.
Associate the configured operator policy components with each other and a network service by applying the example
configuration in the Operator Policy Component Associations section.
Save your configuration to flash memory, an external memory device, and/or a network location using the Exec mode
command save configuration. For additional information on how to verify and save configuration files, refer to the
System Administration Guide .
Step 6
Step 7
Step 8
Step 9
Verify the configuration for each component separately by following the instructions provided in the Verifying the
Feature Configuration section of this chapter.
Call Control Profile Configuration
This section provides the configuration example to create a call control profile and enter the configuration
mode.
Use the call control profile commands to define call handling rules that will be applied via an operator policy.
Only one call control profile can be associated with an operator policy, so it is necessary to use (and repeat
as necessary) the range of commands in this mode to ensure call-handling is sufficiently managed.
Configuring the Call Control Profile for an SGSN
The example below includes some of the more commonly configured call control profile parameters with
sample variables that you will replace with your own values.
configure
call-control-profile profile_name>
attach allow access-type umts location-area-list instance list_id
authenticate attach
location-area-list instance instance area-code area_code
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APN Profile Configuration
sgsn-number E164_number
end
Notes:
• Refer to the Call Control Profile Configuration Mode chapter in the Command Line Interface Reference
for command details and variable options.
• This profile will only become valid when it is associated with an operator policy.
Configuring the Call Control Profile for an MME or S-GW
The example below includes some of the more commonly configured call control profile parameters with
sample variables that you will replace with your own values.
configure
call-control-profile profile_name
associate hss-peer-service service_name s6a-interface
attach imei-query-type imei verify-equipment-identity
authenticate attach
dns-pgw context mme_context_name
dns-sgw context mme_context_name
end
Notes:
• Refer to the Call Control Profile Configuration Mode chapter in the Command Line Interface Reference
for command details and variable options.
• This profile will only become valid when it is associated with an operator policy.
APN Profile Configuration
This section provides the configuration example to create an APN profile and enter the apn-profile configuration
mode.
Use the apn-profile commands to define how calls are to be handled when the requests include an APN. More
than one APN profile can be associated with an operator policy.
The example below includes some of the more commonly configured profile parameters with sample variables
that you will replace with your own values.
configure
apn-profile profile_name
gateway-address 123.123.123.1 priority 1(SGSN only)
direct-tunnel not-permitted-by-ggsn (SGSN only)
idle-mode-acl ipv4 access-group station7 (S-GW only)
end
Notes:
• All of the parameter defining commands in this mode are product-specific. Refer to the APN Profile
Configuration Mode chapter in the Command Line Interface Reference for command details and variable
options.
• This profile will only become valid when it is associated with an operator policy.
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IMEI Profile Configuration - SGSN only
IMEI Profile Configuration - SGSN only
This section provides the configuration example to create an IMEI profile and enter the imei-profile
configuration mode.
Use the imei-profile commands to define how calls are to be handled when the requests include an IMEI in
the defined IMEI range. More than one IMEI profile can be associated with an operator policy.
The example below includes some of the more commonly configured profile parameters with sample variables
that you will replace with your own values.
configure
imei-profile profile_name
ggsn-address 211.211.123.3
direct-tunnel not-permitted-by-ggsn
associate apn-remap-table remap1
end
Notes:
(SGSN only)
• It is optional to configure an IMEI profile. An operator policy can include IMEI profiles and/or APN
profiles.
• This profile will only become valid when it is associated with an operator policy.
APN Remap Table Configuration
This section provides the configuration example to create an APN remap table and enter the apn-remap-table
configuration mode.
Use the apn-remap-table commands to define how APNs are to be handled when the requests either do or
do not include an APN.
The example below includes some of the more commonly configured profile parameters with sample variables
that you will replace with your own values.
configure
apn-remap-table table_name
apn-selection-default first-in-subscription
wildcard-apn pdp-type ipv4 network-identifier apn_net_id
blank-apn network-identifier apn_net_id (SGSN only)
end
Notes:
• The apn-selection-default first-in-subscription command is used for APN redirection to provide
"guaranteed connection" in instances where the UE-requested APN does not match the default APN or
is missing completely. In this example, the first APN matching the PDP type in the subscription is used.
The first-in-selection keyword is an MME feature only.
• Some of the commands represented in the example above are common and some are product-specific.
Refer to the APN-Remap-Table Configuration Mode chapter in the Command Line Interface Reference
for command details and variable options.
• This profile will only become valid when it is associated with an operator policy.
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Operator Policy Configuration
This section provides the configuration example to create an operator policy and enter the operator policy
configuration mode.
Use the commands in this mode to associate profiles with the policy, to define and associate APNs with the
policy, and to define and associate IMEI ranges. Note: IMEI ranges are supported for SGSN only.
The example below includes sample variable that you will replace with your own values.
configure
operator-policy policy_name
associate call-control-profile profile_name
apn network-identifier apn-net-id_1 apn-profile apn_profile_name_1
apn network-identifier apn-net-id_2 apn-profile apn_profile_name_1
imei range <imei_number to imei_number imei-profile name profile_name
associate apn-remap-table table_name
end
Notes:
• Refer to the Operator-Policy Configuration Mode chapter in the Command Line Interface Reference
for command details and variable options.
• This policy will only become valid when it is associated with one or more IMSI ranges (SGSN) or
subscriber maps (MME and S-GW).
IMSI Range Configuration
This section provides IMSI range configuration examples for each of the products that support operator policy
functionality.
Configuring IMSI Ranges on the MME or S-GW
IMSI ranges on an MME or S-GW are configured in the Subscriber Map Configuration Mode. Use the
following example to configure IMSI ranges on an MME or S-GW:
configure
subscriber-map name
lte-policy
precedence number match-criteria imsi mcc mcc_number mnc mnc_number msin first
start_range last end_range operator-policy-name policy_name
end
Notes:
• The precedence number specifies the order in which the subscriber map is used. 1 has the highest
precedence.
• The operator policy name identifies the operator policy that will be used for subscribers that match the
IMSI criteria and fall into the MSIN range.
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Associating Operator Policy Components on the MME
Configuring IMSI Ranges on the SGSN
The example below is specific to the SGSN and includes sample variables that you will replace with your
own values.
configure
sgsn-global
imsi-range mcc
imsi-range mcc
imsi-range mcc
imsi-range mcc
imsi-range mcc
end
Notes:
311
312
313
314
315
mnc
mnc
mnc
mnc
mnc
411
412
413
414
415
operator-policy
operator-policy
operator-policy
operator-policy
operator-policy
oppolicy1
oppolicy2
oppolicy3
oppolicy4
oppolicy5
• Operator policies are not valid until IMSI ranges are associated with them.
Associating Operator Policy Components on the MME
After configuring the various components of an operator policy, each component must be associated with the
other components and, ultimately, with a network service.
The MME service associates itself with a subscriber map. From the subscriber map, which also contains the
IMSI ranges, operator policies are accessed. From the operator policy, APN remap tables and call control
profiles are accessed.
Use the following example to configure operator policy component associations:
configure
operator-policy name
associate apn-remap-table table_name
associate call-control-profile profile_name
exit
lte-policy
subscriber-map name
precedence match-criteria all operator-policy-name policy_name
exit
exit
context mme_context_name
mme-service mme_svc_name
associate subscriber-map name
end
Notes:
• The precedence command in the subscriber map mode has other match-criteria types. The all type is
used in this example.
Configuring Accounting Mode for S-GW
The accounting mode command configures the mode to be used for the S-GW service for accounting, either
GTPP (default), RADIUS/Diameter, or None.
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Verifying the Feature Configuration
Use the following example to change the S-GW accounting mode from GTPP (the default) to
RADIUS/Diameter:
configure
context sgw_context_name
sgw-service sgw_srv_name
accounting mode radius-diameter
end
Notes:
• An accounting mode configured for the call control profile will override this setting.
Verifying the Feature Configuration
This section explains how to display the configurations after saving them in a .cfg file as described in the
System Administration Guide .
Important
All commands listed here are under Exec mode. Not all commands are available on all platforms.
Verify that the operator policy has been created and that required profiles have been associated and configured properly
by entering the following command in Exec Mode:
show operator-policy full name oppolicy1
The output of this command displays the entire configuration for the operator policy configuration.
[local]asr5x00 show operator-policy full name oppolicy1
Operator Policy Name = oppolicy1
Call Control Profile Name
: ccprofile1
Validity
: Valid
APN Remap Table Name
: remap1
Validity
: Valid
IMEI Range 711919739
to
711919777
IMEI Profile Name
: imeiprof1
Include/Exclude
: Include
Validity
: Valid
APN NI homers1
APN Profile Name
: apn-profile1
Validity
: Valid
Notes:
• If the profile name is shown as "Valid", the profile has actually been created and associated with the policy. If the
Profile name is shown as "Invalid", the profile has not been created/configured.
• If there is a valid call control profile, a valid APN profile and/or valid IMEI profile, and a valid APN remap table,
the operator policy is valid and complete if the IMSI range has been defined and associated.
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Verifying the Feature Configuration
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Paging in Common Routing Area for 2G and 3G
• Feature Description, page 367
• How it Works, page 367
• Configuring Paging in Common Routing Area for 2G and 3G, page 369
• Monitoring and Troubleshooting Paging in Common Routing Area for 2G and 3G feature, page 369
Feature Description
If the RA is configured in both 2G and 3G, the SGSN now supports paging in both the RATs. In previous
releases common Routing Area across 2G and 3G was not supported completely. Paging was done only in
the last known RAT and power-off detach from other RAT was not supported.
With the introduction of this feature, the following enhancements have been made:
1 If paging has to be done in RA which is common across the RATs, the SGSN supports paging initiation
in both the RATs.
2 The SGSN accepts power-off detach from the common RA.
3 If the MS is in STANDBY or PMM-IDLE state and a downlink packet arrives at the SGSN, paging is
done. This is applicable for both A/Gb and Iu modes.
GPRS detach (power-off) may be initiated by the MS, but as the request is received in switched off mode the
core network does not send a Detach Accept. When the Routing Area is shared across (Iu/Gb), the Detach
Request is accepted at any of the modes and the subscriber details are cleared.
How it Works
This section describes the support for common Routing Area (RA) for 2G and 3G in detail. Consider the
following 2G and 3G scenarios:
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Paging in Common Routing Area for 2G subscriber
Paging in Common Routing Area for 2G subscriber
The Subscriber is attached in 2G and is in Standby state. Downlink data is received at the SGSN and it starts
paging in both 3G and 2G as the RA is shared.
Scenario-1:
• A detach request (power off) is sent in 3G, stop paging in 2G
• Handle the detach request (power off).
Scenario-2:
• If detach request (power off) is sent in 3G, stop paging in 3G
• Indicate to the 2G network
Scenario-3:
• If page response arrives in 2G, stop paging in 3G
• Handle the page response in 2G.
Scenario-4:
• If service request arrives in 3G, drop the packet.
Any packet other than RAU, Attach and Detach (power off) as page response will be dropped in the other
RAT.
In paging policy has to be RA based under GPRS service to initiate common RA paging.
To enable common Routing Area paging, the configured paging-policy under the GPRS service must be
Routing Area based. If the paging-policy configuration is not Routing Area based BSSGP paging, this feature
will not be supported though the Routing Area is shared.
Paging in Common Routing Area for 3G subscriber
The Subscriber is attached in 3G and is in an IDLE state. Downlink data is received at the SGSN and it starts
paging in both 3G and 2G as the RA is shared.
Scenario-1:
• If a detach request (power off) is sent in 3G, stop paging in 2G.
• Handle detach request (power off).
Scenario-2:
• If a detach request (power off) is sent in 2G, stop paging in 2G.
• Indicate to 3G network.
Scenario-3:
• If service request is sent in 3G, stop paging in 2G.
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Standards Compliance
• Handle the page response in 3G.
Scenario-4:
• If a page response (LLC PDU) arrives in 2G, drop the packet.
Any packet other than RAU, Attach and Detach (power off) as page response will be dropped in the other
RAT.
The paging algorithm under GPRS service will be applicable if a BSSGP page is done for 3G subscriber. If
the paging-policy configuration is not Routing Area based BSSGP paging, this feature will not be supported
though the Routing Area is shared.
Once a valid response arrives, both the RANAP page and BSSGP page will be stopped. However, in case of
expiry the other RAT will not be informed it will continue to page.
Standards Compliance
Support for Paging in Common Routing Area for 2G and 3G complies with the following standard:
• 3GPP TS 23.060 (version 10.0)
Configuring Paging in Common Routing Area for 2G and 3G
The following command is configured to enable support for this feature:
config
sgsn-global
no common-ra-paging
exit
This command enables paging across common Routing Area (RA) for 2G and 3G. For more information on
this command see, Cisco ASR 5X00 Command Line Interface Reference.
Verifying the Paging in Common Routing Area for 2G and 3G Configuration
Execute the following command to verify the configuration of this feature:
show sgsn-mode
The following parameter indicates if common Routing Area paging is "Enabled" or "Disabled":
• Common RA Paging
Monitoring and Troubleshooting Paging in Common Routing
Area for 2G and 3G feature
This section provides information on the show commands and bulk statistics available to support this feature.
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Paging in Common Routing Area for 2G and 3G Show Command(s) and/or Outputs
Paging in Common Routing Area for 2G and 3G Show Command(s) and/or
Outputs
This section provides information regarding show commands and/or their outputs in support of the Paging in
Common Routing Area for 2G and 3G feature:
show gmm-sm statistics
The following new parameters are added to this show command to display the statistics for this feature:
Paging Statistics
• Total-CRA-Page-Req-Same-RAT
• 3G-PS-CRA-Page-Req
• Total-CRA-Page-Ret-Same-RAT
• 3G-PS-CRA-Page-Ret-Req-in-2G
• Total-CRA-Page-Req-Other-RAT
• 3G-PS-CRA-Page-Req-in-2G
• Total-CRA-Page-Ret-Other-RAT
• 3G-PS-CRA-Page-Ret-Req
• Total-CRA-Page-Rsp-Same-RAT
• 3G-PS-CRA-Page-Rsp
• Total-CRA-Page-Rsp-Other-RAT
• 3G-PS-CRA-Attach-from-2G
• 3G-PS-CRA-RAU-from-2G
• 3G-PS-CRA-Power-Off-from-2G
• Total-CRA-Page-TO-Other-RAT
• 3G-PS-CRA-Timeout-in-2G
• Total-CRA-Page-Stop
• 3G-PS-CRA-Page-Stop
• 2G-PS-CRA-Page-in-3G
• 2G-PS-CRA-Page-Ret-Req-in-3G
• 2G-PS-CRA-Page-Req
• 2G-PS-CRA-Page-Ret-Req
• 2G-PS-CRA-Page-Rsp
• 2G-PS-CRA-Attach-from-3G
• 2G-PS-CRA-RAU-from-3G
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Paging in Common Routing Area for 2G and 3G Bulk Statistics
• 2G-PS-CRA-Power-Off-from-3G
• 2G-PS-CRA-Timeout-in-3G
• 2G-PS-CRA-Page-Stop
Non-Paging Statistics
• 3G-CRA-Attach
• 3G-CRA-RAU
• 3G-CRA-Power-Off
• 2G-CRA-Attach
• 2G-CRA-RAU
• 2G-CRA-Power-Off
Paging in Common Routing Area for 2G and 3G Bulk Statistics
The following statistics are included in the SGSN Schema in support of this feature:
SGSN Schema
• common-ra-3g-page-req-same-rat
• common-ra-2g-page-req-same-rat
• common-ra-3g-page-req-ret-same-rat
• common-ra-2g-page-req-ret-same-rat
• common-ra-3g-page-req-other-rat
• common-ra-2g-page-req-other-rat
• common-ra-3g-page-req-ret-other-rat
• common-ra-2g-page-req-ret-other-rat
• common-ra-3g-page-rsp-same-rat
• common-ra-2g-page-rsp-same-rat
• common-ra-3g-page-rsp-attach-other-rat
• common-ra-2g-page-rsp-attach-other-rat
• common-ra-3g-page-rsp-rau-other-rat
• common-ra-2g-page-rsp-rau-other-rat
• common-ra-3g-page-rsp-power-off-other-rat
• common-ra-2g-page-rsp-power-off-other-rat
• common-ra-3g-page-timeout-other-rat
• common-ra-2g-page-timeout-other-rat
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Paging in Common Routing Area for 2G and 3G Bulk Statistics
• common-ra-3g-page-stop
• common-ra-2g-page-stop
• common-ra-3g-attach-other-rat
• common-ra-2g-attach-other-rat
• common-ra-3g-rau-other-rat
• common-ra-2g- rau-other-rat
• common-ra-3g-power-off-other-rat
• common-ra-2g-power-off-other-rat
For descriptions of these variables, see "SGSN Schema Statistics" in the Statistics and Counters Reference.
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Page Throttling
This chapter describes the Page Throttling feature.
• Feature Description, page 373
• How it Works, page 374
• Configuring Page Throttling, page 378
• Monitoring and Troubleshooting the Page Throttling feature, page 380
Feature Description
The Page Throttling feature limits the number of paging messages going out of the SGSN. It provides flexibility
and control to the operator who can now reduce the number of paging messages going out from the SGSN
based on the network conditions. In some of the customer locations, the amount of paging messages initiated
from the SGSN is very high due to the bad radio conditions. A higher number of paging messages results in
the consumption of bandwidth in the network. This feature provides a configurable rate-limit, in which the
paging message gets throttled at:
• Global level for both 2G and 3G accesses
• NSE level for 2G only
• RNC level for 3G only
This feature improves the bandwidth consumption on the radio interface.
Important
A RLF license is required to configure a RLF Template.
Relationships to Other SGSN Features
The Page Throttling feature inter-works with common RA paging, in which paging messages are initiated
from both 2G and 3G accesses or vice versa.
Introduction of the Page Throttling feature does not result in any changes to the existing paging procedures.
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How it Works
How it Works
The Rate Limiting Function (RLF) framework is used to limit the paging load sent from the SGSN. The Rate
Limiting function is a generic framework which provides the rate-limiting functionality using the Token
Bucket algorithm to achieve rate-limiting.
Page Throttling in a GPRS Scenario
The diagram below represents the design of the Page Throttling feature in a 2G scenario:
Figure 69: Paging Process in 2G with Rate Limiting
The following modules inter-work with each other to achieve page throttling in a GPRS scenario:
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Page Throttling in a GPRS Scenario
1 The Session Manager
2 The GPRS Application
3 The GMM Layer
4 The GPRS Stack
5 RLF Module
Consider the following GPRS scenario, where the SGSN wants to send downlink data or signaling messages
to a subscriber and the subscriber is in a STAND-BY state:
1 The SGSN initiates a paging message to identify the subscriber's current location.
2 The GPRS application sends an indication to the GMM layer whenever it wants to page the MS either for
signaling or data packets. Throttling of paging messages for GPRS is performed at the GMM layer in the
Session Manager (SESSMGR). Throttling can be performed either at the Global or NSE level.
3 For throttling at the global level, the RLF context is created at the Session Manager level and is maintained
in the GMM Control block in the GMM layer.
4 For throttling at the NSE level, the RLF context is created at the Session Manger level for each NSE and
is maintained in the NSE control block in the GMM layer.
5 The GMM layer collects the information about the subscriber to be paged and sends it to the RLF module
for throttling. The RLF template is configurable, and the RLF module performs the throttling function
based on the thresholds configured in the template.
6 The RLF module applies the rate limiting algorithm based on the configured limits. It sends or queues
paging message based on the configured limits, once the maximum rate or the configured threshold is
reached the paging messages are dropped by the RLF module.
7 The GMM layer registers the call-back functions which are used by RLF module to send the paging
messages out of SGSN.
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Page Throttling in an UMTS Scenario
Page Throttling in an UMTS Scenario
The diagram below represents the design of the Page Throttling feature in a 3G scenario:
Figure 70: Paging Process in 3G with Rate Limiting
The following modules inter-work with each other to achieve page throttling in a UMTS scenario:
1 The Session Manager
2 The PMM Application
3 The Access Layer
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Limitations
4 The RANAP Stack
5 RLF Module
Consider the following UMTS scenario, where the SGSN wants to send downlink data or signaling messages
to a subscriber and the subscriber is in a STAND-BY state:
1 The SGSN initiates a paging message to identify the subscriber's current location.
2 The PMM application sends an indication to the Access layer whenever it wants to page the MS either for
signaling or data packets. Throttling of paging messages for UMTS is performed at the Access layer in
the Session Manager (SESSMGR). Throttling can be performed either at the Global or NSE level.
3 For throttling at the global level, the RLF context is created at the Session Manager level and is maintained
in the Access layer.
4 Currently, the SGSN does not allow configuring the same RA in different RNCs across the IuPS services,
instead it allows only within the same IuPS service. For throttling at the RNC level, the RLF context is
created for each RNC and is maintained in the RNC control block of the Access layer in the Session
Manager.
5 The Access layer collects the information about the subscriber to be paged and sends it to the RLF module
for throttling. The RLF template is configurable, and the RLF module performs the throttling function
based on the thresholds configured in the template.
6 The RLF module applies the rate limiting algorithm based on the configured limits. It sends or queues
paging message based on the configured limits, once the maximum rate or the configured threshold is
reached the paging messages are dropped by the RLF module.
7 The Access layer registers the call-back functions which are used by RLF module to send the paging
messages out of SGSN.
Limitations
Listed below are the known limitations of the Page Throttling feature:
• In the SGSN Global configuration mode "interface" command, the NSE-NAME (already existing) and
RNC-NAME (added as part of this feature) are not validated against the configuration under
GPRS-SERVICE or IuPS-SERVICE. This configuration is used only for the purpose of associating the
paging-rlf-template for the peer entity (either NSE/BSC or RNC). It is possible to change the ID to
NAME mapping of both BSC and RNC. The BSC/RNC ID is used for associating the paging-rlf-template
as well as throttling the paging messages internally even though the user can associate the
paging-rlf-template using NAME explicitly.
• The rate limiting parameters for the rlf-template associated at global level should be configured in such
a way that it applies to all configured NSE and RNC's. The SGSN does not guarantee a uniform
distribution of message rate for each NSE/RNC while throttling at a global level.
• Page throttling is applicable to all RNC's whenever the operator configures the same RNC-ID with
different PLMN-ID in different IuPS services. If the operator associates the Paging RLF template for
that RNC-ID, the SGSN starts page throttling for both the RNC's irrespective of the PLMN.
• No mechanism is present to identify if the operator associates the paging-rlf-template by either configured
RNC name or RNC identifier while generating the CLI for "show/save configuration". The
paging-rlf-template CLI is always generated with the RNC name if the operator configured the name
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mapping even though the association is done using the RNC-ID otherwise the output is always generated
with the RNC-ID.
• Currently, the show output "show sgsn mode interface-mgmt-status" displays a maximum of "32"
characters (truncated value) of the name configured for both NSE/RNC and the RLF template name.
• The SGSN does not support paging load limitation to the common RA paging initiated in the other
access.
• Whenever the operator removes the association of paging-rlf-template from a particular NSE/RNC and
if the page-limiting is already enabled at global level, all the queued messages in RLF context maintained
for that NSE/RNC will be flushed out by RLF and it does not accept any new paging messages for
throttling. The RLF context for that NSE/RNC will be cleaned up after all the messages in the queue
flushed out. All the new paging messages for that NSE/RNC will use the global RLF context for further
rate-limiting.
• Currently, the paging message initiated for both signalling and data packets are treated with same priority
as the generic RLF framework does not support priority for throttling.
• Run time association of Paging RLF template to global or per entity level (NSE/RNC) results in statistics
discrepancy (when it gets associated during re-transmission of paging messages already in progress).
• This feature results in a performance impact whenever the GPRS service is configured with many NSE's
and when the service is stopped or removed.
Configuring Page Throttling
The following commands are used to configure the Page Throttling feature. These CLI commands are used
to associate/remove the RLF template for Page Throttling at the Global level, NSE level and RNC level at
the SGSN.
To map RNC Name to RNC Identifier
The interface command is used to configure the mapping between the RNC Id and the RNC name. The
operator can configure the paging-rlf-template either by RNC name or RNC identifier.
config
sgsn-global
interface-management
[ no ] interface {gb peer-nsei | iu peer-rnc} {name value | id value }
exit
Notes:
The no form of the command removes the mapping and other configuration associated for the RNC
paging-rlf-template configuration from the SGSN and resets the behavior to default for that RNC.
Example configurations:
[local]asr5000 configure
[local]asr5000(config) sgsn-global [local]asr5000(config-sgsn-global) interface-management
[local]asr5000(config-sgsn-interface-mgmt) interface
iu peer-rnc id 250 name bng_rnc1
[local]asr5000(config-sgsn-interface-mgmt) end
[local]asr5000
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To associate a paging RLF template
To associate a paging RLF template
This command allows the SGSN to associate a RLF template either at the global level which limits the paging
messages initiated across both 2G (NSE level) and 3G (RNC level) access or at the per entity level either at
RNC level for 3G access or at NSE level for 2G access.
config
sgsn-global
interface-management
[no] paging-rlf-template {template-name template-name} {gb peer-nsei | iu peer-rnc} {name value
| id value}
exit
Notes:
If there no rlf-template is associated for a particular NSE/RNC then the paging load is limited based on the
global rlf-template associated (if present). If no global rlf-template associated then, no rate-limiting is applied
on the paging load.
[local]asr5000(config) sgsn-global
[local]asr5000(config-sgsn-global) interface-management
[local]asr5000(config-sgsn-interface-mgmt) paging-rlf-template
template-name rlf1
[local]asr5000(config-sgsn-interface-mgmt) end[local]asr5000
[local]asr5000 configure
[local]asr5000(config) sgsn-global
[local]asr5000(config-sgsn-global) interface-management
[local]asr5000(config-sgsn-interface-mgmt) paging-rlf-template
template-name rlf2 gb peer-nsei id 1
[local]asr5000(config-sgsn-interface-mgmt) end
[local]asr5000
[local]asr5000 configure
[local]asr5000(config) sgsn-global
[local]asr5000(config-sgsn-global) interface-management
[local]asr5000(config-sgsn-interface-mgmt) paging-rlf-template
template-name rlf2 iu peer-rnc name bng_rnc1
[local]asr5000(config-sgsn-interface-mgmt) end
[local]asr5000
For more information on the CLI commands see, Command Line Interface Reference.
The RLF template can be configured under the global configuration mode which provides the option to
configure the message-rate, burst-size, threshold and delay-tolerance for throttling or rate-limiting. To Configure
the RLF template see, Command Line Interface Reference.
Verifying the Page Throttling Configuration
The Page Throttling feature configuration can be verified by executing the following show commands:
• show configuration
Listed below are the parameters added for the Page Throttling feature:
◦paging-rlf-template template-name
◦paging-rlf-template template-name gb peer-nsei id
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◦paging-rlf-template template-name iu peer-rnc id
◦interface iu peer-rnc id rnc_id name name
• show sgsn-mode interface-mgmt-status
Listed below are the parameters added for the Page Throttling feature:
◦Global Paging RLF template
◦Paging RLF Template
Monitoring and Troubleshooting the Page Throttling feature
This section provides information on the show outputs updated with new statistics to support the Page Throttling
feature.
Page Throttling Show Command(s) and/or Outputs
Listed below are the show outputs and new statistics added for the Page Throttling feature:
show gmm-sm statistics verbose
The following new statistics are added in the show gmm-sm statistics verbose status command to support
the Page Throttling feature:
• 3G Page Throttling statistics
• PS-Page-Req sent by RLF
• Ret-PS-Page-Req sent by RLF
• PS-Page-Req dropped by RLF
• Ret-PS-Page-Req dropped by RLF
• PS-Page-Req dropped due to no memory
• 2G Page Throttling statistics
• Paging Request sent out by RLF
• Total-Page-Req sent
• Ret-Total-Page-Req sent
• Page-Requests-LA
• Ret-Page-Requests-LA
• Page-Requests-RA
• Ret-Page-Requests-RA
• Page-Requests-BSS
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Page Throttling Show Command(s) and/or Outputs
• Ret-Page-Requests-BSS
• Page-Requests-Cell
• Ret-Page-Requests-Cell
• Paging Request dropped by RLF
• Total-Page-Req dropped
• Ret-Total-Page-Req dropped
• Page-Requests-LA
• Ret-Page-Requests-LA
• Page-Requests-RA
• Ret-Page-Requests-RA
• Page-Requests-BSS
• Ret-Page-Requests-BSS
• Page-Requests-Cell
• Ret-Page-Requests-Cell
• PS-Page-Req dropped due to no memory
For detailed information and description of the parameters see, Statistics and Counters Reference.
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CHAPTER
29
PGW Restart Notification in S4-SGSN
This chapter describes the PGW Restart Notification in S4-SGSN.
• Feature Description, page 383
• Overview, page 383
• How it Works, page 384
• Configuring PGW Restart Notification in S4-SGSN, page 385
• Monitoring and Troubleshooting PRN support in S4-SGSN, page 386
Feature Description
The purpose of enabling PGW Restart Notification (PRN) in S4-SGSN is to provide a simple and optimized
solution for handling the signaling overload on the SGSN when a PGW failure occurs. Until release 10, the
SGW used to send Delete Bearer Request for every PDN connection activated through the failed PGW. This
results in signaling overload on the SGSN. From 3GPP Release 10 specifications onwards it is possible for a
SGW to indicate a PGW failure through a single PRN message to the SGSN.
When the SGW detects that a peer PGW has restarted or it is not reachable, it deletes all the PDN connections
associated with that peer node and releases all the internal resources associated with those PDN connections.
The SGW sends a PGW Restart Notification only to the SGSNs that have configured advertisement of PGW
restart notification in echo request/response messages. When the S4-SGSN receives this message, according
to the control plane IP address of the restarted PGW and the control plane IP address of the SGW on the S4
interface included in the message, the S4-SGSN deletes all PDN connections associated with the SGW and
the restarted PGW. The SGSN also releases any internal resources associated with those PDN connections.
The S4-SGSN sends a PGW Restart Notification Acknowledge message in response to the PGW Restart
Notification message sent by the SGW.
Overview
Listed below is an overview of the PRN feature in the S4-SGSN:
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How it Works
• When the PGW Restart Notification is enabled at the S4-SGSN, the PRN bit in Node Features IE in
Echo Request message is set. This indicates to the SGW that the S4-SGSN supports PGW Restart
Notification message (PRN).
• The SGW sends the PRN message to the S4-SGSN in case of PGW node restart or if a path failure
occurs. In case of PGW node restart the PRN arrives without any cause, but if a path failure has occurred
the PRN is received with cause "PGW not responding".
• The S4-SGSN on receiving the PRN, deletes all PDN connections associated with the SGW and the
restarted PGW. It also releases the internal resources associated with those PDN connections.
• The S4-SGSN prioritizes the PDN connections to be restored based on subscribed APN restoration
priority (if received from the HSS). A locally configured value as default restoration priority shall be
used for a user's PDN connection if it is not received from the HSS. Restoration priority value received
in subscription record from HSS value has more priority over locally configured default value.
• If the S4-SGSN wants to restore the PDN connections, it does so by using the "reactivation requested"
cause if restoration priority value is available irrespective of whether UE is in CONNECTED or IDLE
state.
• Deactivation is performed with cause "regular deactivation" if the UE is in CONNECTED state and
restoration priority is not available. If the UE is in IDLE state and restoration priority value is not
available, then local deactivation is done.
How it Works
Listed below is a detailed description of how the PGW restart notification feature in S4-SGSN works:
1 The PRN support should be enabled through the gtpc command in egtp-service configuration mode.
2 If PRN is received and support for PRN is not configured then the S4-SGSN sends PRN Acknowledge
message with EGTP_CAUSE_SERVICE_DENIED cause code.
3 If PRN is received and support for PRN is configured then S4-SGSN responds with PRN Acknowledge
message with cause code EGTP_CAUSE_REQ_ACCEPTED.
4 When PRN is enabled at the S4-SGSN, the PRN bit in Node Features IE in Echo Request message is set.
This indicates to the SGW that the S4-SGSN supports PGW Restart Notification message.
5 The SGW sends the PRN to the S4-SGSN in case of PGW node restart or path failure. In case of PGW
node restart, PRN arrives without any cause. In case of path failure, PRN is received with cause specified
as "PGW not responding". The behavior of S4-SGSN on receiving PRN is same in both scenarios.
6 When a PRN is received, the PDN connections are deleted based on SGW and PGW address received in
PRN message.
7 The S4-SGSN restores the PDN connections by sending Deactivate Request to UE using sm cause
"reactivation required".
8 Restoration will be done only when the restoration priority is received from the HSS subscription for that
PDN or when the default apn-restoration priority is configured locally under the apn-profile.
Limitations
The PRN feature in S4-SGSN supports either IPv4 or IPv6 but not both at the same time.
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Standards Compliance
Standards Compliance
The PRN feature in S4-SGSN complies with the following standards:
• 3GPP TS 23.007 version 11
• 3GPP TS 29.274 version 11
Configuring PGW Restart Notification in S4-SGSN
The following commands are used to configure the PGW restart notification support in the S4-SGSN:
Configure Node IE For PRN Advertisement
The following CLI command configures advertisement of PGW Restart Notification in echo request/response
messages. This is an existing CLI command under the EGTP Service Configuration mode which has to be
configured in order to inform SGW that S4-SGSN supports receiving PRN. The command option node-feature
pgw-restart-notification has to be configured in order to inform SGW that S4-SGSN supports receiving
PRN.
configure
context context_name
egtp_service service_name
gtpc { bind { ipv4-address ipv4_address [ ipv6-address ipv6_address ] | ipv6-address ipv6_address
[ ipv4-address ipv4_address ] } | echo-interval seconds [ dynamic [ smooth-factor multiplier ] ] |
echo-retransmission-timeout seconds | ip qos-dscp { forwarding_type } | max-retransmissions num |
node-feature pgw-restart-notification | path-failure detection-policy echo | private-extension
overcharge-protection | retransmission-timeout seconds }
exit
Configure Default APN Restoration Priority
The following CLI command configures APN restoration priority for an APN profile:
configure
apn-profile profile_name
apn-restoration priority priority_value
exit
Notes:
• The PGW Restart Notification (PRN) message is sent by the S-GW when it detects a peer P-GW has
re-started. The S4-SGSN on receiving the PRN message, uses the default apn-restoration priority value,
if priority value is not available in HSS Subscription to prioritize the affected PDN connections for
restoration. To restore PDN it is mandatory to get priority value from HSS in subscription record or
default value must be configured under apn-profile.
• The priority value is an integer value from 1 through 16. Where "1" is the highest priority and "16" is
the lowest priority.
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Verifying the PRN Configuration in S4-SGSN
Verifying the PRN Configuration in S4-SGSN
Execute the command show egtp-service all to verify the PRN support configuration in S4-SGSN:
show egtp-service all
The output of this command displays if the PRN support has been configured:
.
.
.
GTPC Node Feature
PGW Restart Notification
: Enabled
.
.
Monitoring and Troubleshooting PRN support in S4-SGSN
This section provides information on the show commands and disconnect reasons available to support this
feature.
PGW Restart Notification Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs in support of the PRN
feature in S4-SGSN:
show s4-sgsn statistics
The following PDP Deletion Statistics have been added to the show s4-sgsn statistics command:
• PDP Deletion Statistics
• 3G S4 PDPs Deleted due to PGW Restart Notification
• 2G S4 PDPs Deleted due to PGW Restart Notification
show egtpc statistics
The following PGW Restart Notification statistics have been added to show egtpc statistics :
• PGW Restart Notification Request
• Total RX
• Initial RX
• Retrans RX
• PGW Restart Notification Ack
• Total TX
• Initial TX
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show session disconnect-reasons verbose
• Accepted
• Denied
• Discarded
Notes:
• When APN Restoration priority value is available, either through local configuration or through
subscription received from HSS, then the SGSN sends Deactivation Request with SM Cause "Reactivation
Required" towards MS after PGW Restart Notification Request from SGW.
• When APN Restoration priority value is not available and the subscriber is in Idle/Standby state, the
SGSN deletes the affected bearers locally and does not trigger Paging Request towards the MS to send
Deactivation Request.
• When APN Restoration priority value is not available and the subscriber is in Connected/Ready state,
the SGSN will send Deactivation Request.
show session disconnect-reasons verbose
The following disconnect reason is used to track both PGW Restart or path failure and SGW path failure:
• sgsn-gtpc-path-failure(267)
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show session disconnect-reasons verbose
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CHAPTER
30
Quality of Service (QoS) Management for SGSN
This chapter describes the implementation of Quality of Service (QoS) related features and functionali ties
in SGSN.
• Quality of Service Management, page 389
Quality of Service Management
The network associates a certain Quality of Service (QoS) with each data transmission in the GPRS packet
mode. The QoS attributes are collectively termed as a "QoS Profile". The PDP context stores the QoS Profile
information. The QoS management is performed by using the PDP context management procedures, such as
PDP context activation, modification and de-activation. QoS enables the differentiation between services
provided.
SGSN Quality of Service Management
The SGSN applies an admission control function on each PDP context activation request. The function results
in further processing of the request; that is, either negotiation of the QoS with the Mobile Subscriber (MS),
or rejection of the PDP context activation request. The SGSN negotiates QoS with the MS when the level
requested by the subscriber cannot be supported or when the QoS level negotiated from the previous SGSN
cannot be supported at an inter-SGSN routing area update. The response to the mobile subscriber depends on
the provisioned subscription data, the requested QoS, the QoS permitted by the Gateway node and the QoS
permitted by the Radio Access Network.
Quality of Service Attributes
In an End-to- End Service the network user is provided with a certain Quality of Service, which is specified
by a set of QoS attributes or QoS profile. The first list of attributes was defined in Release 97/98 of the 3GPP
recommendations but these are now replaced by Release 99 3GPP recommendations. Many QoS profiles can
be defined by the combination of these attributes. Each attribute is negotiated by the MS and the
GPRS/UMTS/LTE network. If the negotiated QoS profiles are accepted by both parties then the network will
have to provide adequate resources to support these QoS profiles.
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Quality of Service Attributes in Release 97/98
In Release 97/98 recommendations, the PDP context is stored in the MS, SGSN and GGSN. It represents the
relation between one PDP address, PDP type (static or dynamic address), the address of a GGSN that serves
as an access point to an external PDN, and one Quality of Service (QoS) profile. PDP contexts with different
QoS parameters cannot share the same PDP address. In Release 99 recommendations a subscriber can use
more than one PDP contexts with different QoS parameters and share the same PDP address.
Quality of Service Attributes in Release 97/98
In Release 97/98 of the 3GPP recommendations, QoS is defined according to the following attributes:
• Precedence Class: This attribute indicates the packet transfer priority under abnormal conditions, for
example during a network congestion load.
• Reliability Class: This attribute indicates the transmission characteristics. It defines the probability of
data loss, data delivered out of sequence, duplicate data delivery, and corrupted data. This parameter
enables the configuration of layer "2" protocols in acknowledged or unacknowledged modes.
• Peak Throughput Class: This attribute indicates the expected maximum data transfer rate across the
network for a specific access to an external packet switching network (from 8 Kbps up to 2,048 Kbps).
• Mean Throughput Class: This attribute indicates the average data transfer rate across the network
during the remaining lifetime of a specific access to an external packet switching network (best effort,
from 0.22 bps up to 111 Kbps).
• Delay Class: This attribute defines the end-to-end transfer delay for the transmission of Service Data
Units (SDUs) through the GPRS network. The SDU represents the data unit accepted by the upper layer
of GPRS and conveyed through the GPRS network.
Quality of Service Attributes in Release 99
The attributes of GPRS QoS were modified in Release 99 of the 3GPP recommendations in order to be identical
to the ones defined for UMTS.
The quality of service is a type "4" information element with a minimum length of "14" octets and a maximum
length of "18" octets.
The Release 99 of 3GPP recommendations defines QoS attributes such as Traffic class, Delivery order, SDU
format information, SDU error ratio, Maximum SDU size, Maximum bit rate for uplink, Maximum bit rate
for downlink, Residual bit error ratio, Transfer delay, Traffic-handling priority, Allocation/retention priority,
and Guaranteed bit rate for uplink and Guaranteed bit rate for downlink. The attributes are listed below:
• Traffic Class: Indicates the application type (conversational, streaming, interactive, background). Four
classes of traffic have been defined for QoS:
◦Conversational Class: These services are dedicated to bi-directional communication in real time
(for example, voice over IP and video conferencing).
◦Streaming Class: These services are dedicated to uni-directional data transfer in real time (for
example, audio streaming and one-way video).
◦Interactive Class: These services are dedicated to the transport of human or machine interaction
with remote equipment (for example, Web browsing, access to a server and access to a database).
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◦Background Class: These services are dedicated to machine-to-machine communication; this
class of traffic is not delay sensitive (for example, e-mail and SMS).
• Delivery Order: Indicates the presence of an in-sequence SDU delivery (if any).
• Delivery of Erroneous SDUs: Indicates if erroneous SDUs are delivered or discarded.
• SDU Format Information: Indicates the possible exact sizes of SDUs.
• SDU Error Ratio: Indicates the maximum allowed fraction of SDUs lost or detected as erroneous.
• Maximum SDU Size: Indicates the maximum allowed SDU size (from "10" octets up to "1,520" octets).
• Maximum Bit Rate for Uplink: Indicates the maximum number of bits delivered to the network within
a period of time (from "0" up to "8,640" Kbps).
• Maximum Bit Rate for Downlink: Indicates the maximum number of bits delivered by the network
within a period of time (from "0" up to "8,640" Kbps).
• Residual Bit Error Ratio: Indicates the undetected bit error ratio for each sub-flow in the delivered
SDUs.
• Transfer Delay: Indicates the maximum time of SDU transfer for 95th percentile of the distribution of
delay for all delivered SDUs.
• Traffic-Handling Priority: Indicates the relative importance of all SDUs belonging to a specific GPRS
bearer compared with all SDUs of other GPRS bearers.
• Allocation/Retention Priority: Indicates the relative importance of resource allocation and resource
retention for the data flow related to a specific GPRS bearer compared with the data flows of other GPRS
bearers (this attribute is useful when resources are scarce).
• Guaranteed Bit Rate for Uplink: Indicates the guaranteed number of bits delivered to the network
within a period of time (from "0" up to "8,640" Kbps).
• Guaranteed Bit Rate for Downlink: Indicates the guaranteed number of bits delivered to the network
within a period of time (from "0" up to "8,640" Kbps).
• Maximum Bit Rate for Uplink (extended, octet 17): This field is an extension of the Maximum bit
rate for uplink in octet "8". The coding is identical to that of the Maximum bit rate for downlink
(extended). It is used to signal extended Maximum bit rates in uplink (up to "256" Mbps)
• Maximum Bit Rate for Downlink (extended, octet 15): Used to signal extended bit rates for downlink
delivered by the network (up to "256" Mbps). This attribute is supported in 3GPP Release 6 and beyond.
• Guaranteed Bit Rate for Uplink (extended, octet 18): This field is an extension of the Guaranteed bit
rate for uplink in octet "12". The coding is identical to that of the guaranteed bit rate for downlink
(extended). Used to signal extended Guaranteed bit rates in uplink (up to "256" Mbps)
• Guaranteed Bit Rate for Downlink (extended, octet 16): Used to signal extended Guaranteed bit rates
in downlink (up to "256" MBps). This attribute is supported in 3GPP Release 6 and beyond.
Quality of Service Management in SGSN
QoS management comprises of approximately "23" individual parameters. As part of QoS Management, the
SGSN negotiates the MS requested QoS with the following during PDP context Activation and Modification
procedures:
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• Subscribed QoS
• Local QoS capping limit (if configured)
• QoS sent by GGSN in tunnel management messages
• QoS sent by RNC in RAB assignment messages (UMTS only)
Each negotiation is between QoS parameters of the two sets, and the resulting negotiated QoS will be the
lower of the two. QoS negotiation for Secondary PDP contexts is same as Primary PDP context.
For more information see, 3GPP TS 24.008 (section 10.5.6.5 "Quality of Service".
QoS Negotiation During an Activation Procedure
During an Activation procedure the MS requested QoS is negotiated with the subscribed QoS. Higher values
are not valid in case of GPRS access, the SGSN restricts some of the QoS parameters during PDP activation
in GPRS access. Listed below are the QoS parameters which are restricted in GPRS access:
• Maximum Bitrate (MBR) DL is capped to "472" kbps.
• Maximum Bitrate (MBR) UL is capped to "472" kbps.
• Peak Throughput (PR) is capped to "6" ("32000" octets/sec).
• Reliability class (RC) of "0x2", "Unacknowledged GTP; Acknowledged LLC and RLC, Protected data"
is not supported. In such cases, RC is over-ridden as "0x3", "Unacknowledged GTP and LLC;
Acknowledged RLC, Protected data"
The SDU Error ratio is capped in following cases:
• For Reliability Class "0x3", the SDU error ratio is capped to "4" (1x10-4) if it exceeds a value of "4", a
value greater than "4" represents stringent error ratios.
• For Reliability Class greater than "0x3", the SDU error ratio capped to "3" (1x10-3) if the value provided
exceeds "4".
For more information see, 3GPP TS 23.107 (Table 6 "Rules for determining R99 attributes from R97/98
attributes").
The QoS parameters are sent to GGSN in the Create PDP Context Request. On receiving a Create PDP Context
Response, the QoS sent by GGSN is negotiated with the one sent by SGSN to GGSN. For GPRS access, this
negotiated QoS is sent to the MS in Activate PDP Context Accept.
If the UE requests a subscribed traffic class, the SGSN defaults it to "Interactive" traffic class regardless of
the configuration in the HLR subscription.
In a UMTS access scenario, the negotiated QoS is sent to RNC in RAB Assignment Request. By default, the
SGSN includes Alternative Max Bit Rate with type set to "Unspecified". This indicates to the RNC that it can
further negotiate the QoS downwards if either the RNC/UE cannot support the QoS value sent. The RNC may
downgrade the QoS based on its current load/capability and include it in RAB Assignment Response. The
SGSN does QoS negotiation once more with received QoS from the RNC. This is used as the negotiated QoS
of PDP context and is sent to the MS in Activate PDP context Accept. If the RNC has downgraded the QoS,
the same will be informed to GGSN by means of an Update PDP context procedure.
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Important
When the MS sends an Activate PDP Context Request, it may set all the QoS values to "0", this implies
that the MS is requesting the SGSN to take QoS values from the subscription. In this case the SGSN
negotiates the subscribed QoS with any locally configured QoS and sends the negotiated QoS value to
GGSN.
QoS Negotiation During a Modification Procedure
The PDP Context Modification procedure can be MS initiated or Network initiated, it is used to change the
current negotiated QoS. If it is a MS initiated PDP Context Modification procedure the QoS negotiation is
similar to the QoS negotiation followed during an Activation procedure. The HLR or GGSN or SGSN (RNC
in case of UMTS access) can perform a Network Initiated QoS modification.
For more information on "PDP Context Modification Procedure" see, 3GPP TS 24.008 section 6.1.3.3
HLR Initiated QoS Modification
The Subscription Information of a Subscriber may change due to the following:
• User action (The user may subscribe for a more premium service)
• Service provider action (The QoS is restricted on reaching download limits)
This change is relayed by the HLR to the SGSN through the Insert Subscription Data procedure. As per 3GPP
TS 23.060 section 6.11.1.1 "Insert Subscriber Data procedure", the SGSN negotiates the current QoS with
new subscribed QoS and initiates a Network Initiated PDP modification procedure only in case of QoS
downgrade. As part of this procedure, the GGSN (and RNC in case of UMTS access) is updated with the new
negotiated QoS followed by the MS. If a failure occurs or no response is received from the MS for the Modify
Request, the PDP context is deactivated.
The SGSN is compliant with 3GPP TS 23.060 Release 7 version. The specifications Release 8 and above
specify a modified behavior when the UE is in a IDLE/STANDBY state. If the QoS is modified by the HLR
when an UE is an IDLE/STANDBY state the PDP is de-activated. The SGSN is made compliant with this
change to align its behavior with LTE elements like MME. Therefore the SGSN is compliant with both the
Release 7 and Release 8 specifications.
GGSN Initiated QoS Modification
The GGSN may initiate a QoS Modification Request due to any of the following reasons:
• An External Trigger (PCRF)
• Current load or capability of the GGSN
• If the "No Qos negotiation" flag is set in the previous Tunnel Management Request from SGSN.
The SGSN negotiates this QoS with the subscription. The negotiated Qos is then sent to the UE in a Modify
PDP Request. In an UMTS access scenario, the SGSN updates the new negotiated QoS to the RNC. The new
negotiated Qos is then forwarded to the GGSN in response message.
SGSN Initiated QoS Modification
The SGSN initiated QoS Modification occurs during an Inter-RAT HO (2G to 3G / 3G or 2G), here the
negotiated QoS in new access is different from the negotiated QoS in old access. The SGSN QoS initiated
QoS Modification can also occur during a new SGSN ISRAU/SRNS procedure where the new negotiated
QoS is different from the negotiated QoS received from the peer SGSN.
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Whenever a UE performs an Intra or Inter SGSN HO, the SGSN receives the requested QoS, subscribed QoS
and the negotiated QoS from the old access (during Intra SGSN HO) or from peer SGSN (during Inter SGSN
HO). This requested QoS is then negotiated with the subscribed QoS. If the negotiated QoS is different from
the received negotiated QoS, the SGSN initiates a network initiated QoS modification procedure to update
the new negotiated QoS to the UE after completing the HO procedure.
RNC Initiated QoS Modification (UMTS access only)
In a RNC initiated QoS modification procedure the SGSN negotiates the QoS with the current negotiated
QoS. In case of a downgrade, the SGSN updates the GGSN and MS with the new negotiated QoS.
For more information see, 3GPP TS 23.060 section 9.2.3.6 on "RAN-initiated RAB Modification Procedure"
No QoS Negotiation Flag
When the \'No QoS Negotiation\' flag is set, the SGSN indicates to the GGSN not to negotiate the QoS. The
"No QoS Negotiation" flag is set in the following scenarios:
• While sending Update PDP Context request during activation (Direct tunnel).
• During a service request for data with direct tunnel enabled for the subscriber, a UPCQ is initiated to
inform the GGSN with the teid and the address of the RNC. This Update PDP context request has no
negotiation bit set.
• Update PDP context request sent during preservation procedures.
• UPCQ sent to indicate establishment / removal of direct tunnel.
• Intra SGSN SRNS.
• Downlink data for the subscriber without active RABs and direct tunnel enabled for the subscriber,
UPCQ is initiated to inform the GGSN of the teid and the address of the RNC. This Update PDP context
request has "No QoS Negotiation" flag set.
• In all modification procedures (HLR, RNC, MS) if any other node other than the modifying entity has
downgraded the QoS. For example, consider a HLR Initiated Modification procedure where the SGSN
does the following signaling:
◦Initiates a UPCQ to inform the GGSN of the QOS change, GGSN sends a UPCR with same QOS
as UPCQ.
◦Modify PDP context Request to MS, the MS sends a Modify PDP Accept.
◦RAB establishment request to the RNC, the RNC downgrades the QoS in the RAB assignment
response.
◦The SGSN initiates a UPCQ to inform the GGSN of the new QoS sent in the previous step. This
UPCQ will have no QoS negotiation bit set.
• If loss of Radio connectivity feature is enabled, then the Update PDP Context initiated to inform the
GGSN that the MS is back in Radio Coverage will have the "No Qos Negotiation" bit set.
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QoS Features
Traffic Policing
The SGSN can police uplink and downlink traffic according to predefined QoS negotiated limits fixed on the
basis of individual contexts - either primary or secondary. The SGSN employs the Two Rate Three Color
Marker (RFC2698) algorithm for traffic policing. The algorithm meters an IP packet stream and marks its
packets either green, yellow, or red depending upon the following variables:
• PIR: Peak Information Rate (measured in bytes/second)
• CIR: Committed Information Rate (measured in bytes/second)
• PBS: Peak Burst Size (measured in bytes)
• CBS: Committed Burst Size (measured in bytes)
The following figure depicts the working of the TCM algorithm:
Figure 71: TCM Algorithm Logic for Traffic Policing
The policing function compares the data unit traffic with the related QoS attributes. Data units not matching
the relevant attributes will be dropped or marked as not matching, for preferential dropping in case of
congestion.
Procedure To Configure Traffic Policing:
This procedure is used to configure the actions governing the subscriber traffic flow. That is, if the flow
violates or exceeds the configured, negotiated peak or committed data-rates. The SGSN performs traffic
policing only if the command qos rate-limit direction is configured.
config
apn-profile profile_name
qos rate-limit direction { downlink | uplink } [ burst-size { auto-readjust [ duration seconds ] | bytes }
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] [ class { background | conversational | interactive traffic_priority | streaming } ] [ exceed-action { drop
| lower-ip-precedence | transmit } ] [ gbr-qci [ committed-auto-readjust durarion seconds ] ] [ non-gbr-qci
[ committed-auto-readjust durarion seconds ] ] [ violate-action { drop | lower-ip-precedence | transmit
}]+
exit
This command can be entered multiple times to specify different combinations of traffic direction and class.
The remove keyword can be used with the qos rate-limit direction command to remove the qos rate-limit
direction entries from the configuration.
config
apn-profile profile_name
remove qos rate-limit direction { downlink | uplink } [ burst-size { auto-readjust [ duration seconds ]
| bytes } ] [ class { background | conversational | interactive traffic_priority | streaming } ] [ exceed-action
{ drop | lower-ip-precedence | transmit } ] [ gbr-qci [ committed-auto-readjust durarion seconds ] ] [
non-gbr-qci [ committed-auto-readjust durarion seconds ] ] [ violate-action { drop | lower-ip-precedence
| transmit } ] +
exit
QoS Traffic Policing Per Subscriber
Traffic policing enables the operator to configure and enforce bandwidth limitations on individual PDP contexts
for a particular traffic class. It deals with eliminating bursts of traffic and managing traffic flows in order to
comply with a traffic contract.
The SGSN complies with the DiffServ model for QoS. The SGSN handles the 3GPP defined classes of traffic,
QoS negotiation, DSCP marking, traffic policing, and support for HSDPA/HSUPA.
The per Subscriber traffic policing can be achieved by creating an operator policy for required subscribers
(IMSI range) and associating the APN profile having the relevant qos-rate-limit configuration with the operator
policy.
DSCP Marking and DSCP Templates
Differentiated Services Code Point specifies a mechanism for classifying and managing network traffic and
providing Quality of Service (QoS) on IP networks. DSCP uses the 6-bit Differentiated Services Code Point
(DSCP) field in the IP header for packet classification purposes. DSCP replaces the Type of Service (TOS)
field.
The SGSN performs a DiffServ Code Point (DSCP) marking of the GTP-U packets according to the
allowed-QoS to PHB mapping. The default mapping matches that of the UMTS to IP QoS mapping defined
in 3GPP TS 29.208.
DSCP is standardized by the RFCs 2474 and 2475. DSCP templates contain DSCP code points for specific
traffic types. DSCP is used to differentiate traffic types and the priority with which they should be allowed
through the network. In MPC, DSCP templates are created and applied for signaling (2G/3G) and data traffic,
where signaling takes precedence over the data plane. When signaling and data are sent through a single
channel, critical signaling messages are adversely affected due to the queueing created by large chunks of
data. With DSCP it is possible to have separate queues for signaling and data based on code point value and
handle them based on relative precedence.
The SGSN supports DSCP marking of the GTP control plane messages on the Gn/Gp interface. This allows
the QoS to be set on GTP-C messages, and is useful if Gn/Gp is on a less than ideal link. DSCP can also be
configured at the NSEI level and this configuration has higher precedence over GPRS level configuration.
DSCP marking is configurable through the CLI, with default being "Best Effort Forwarding".
The following configuration procedures are used to configure DSCP marking parameters:
1 The IP command
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The ip command is used to configure DSCP Marking which is used for sending packets of a particular
3GPP QoS class.
config
apn-profile profile_name
ip { qos-dscp { { downlink | uplink } { background forwarding | conversational forwarding | interactive
traffic-handling-priority priority forwarding | streaming forwarding } + } | source-violation { deactivate
[ all-pdp | exclude-from accounting | linked-pdp | tolerance-limit } | discard [ exclude-from-accounting
] | ignore }
exit
To reset the values to the default configuration, use the following procedure:
config
apn-profile profile_name
default ip { qos-dscp [ downlink | uplink ] | source-violation }
exit
The following procedure is used to disable IP QoS-DSCP mapping:
config
apn-profile profile_name no ip qos-dscp { downlink | uplink } { background | conversational |
interactive | streaming } +
exit
2 DSCP template configuration mode commands
DSCP template configuration mode commands are used to configure DSCP marking for control packets
and data packets for Gb over IP. Any number of DSCP templates can be generated in the SGSN Global
configuration mode and then a template can be associated with one or more GPRS Services via the
commands in the GPRS Service configuration mode.
The following configuration procedure is used to configure DSCP value for 3GPP QoS class downlink
control packets:
config
context context_name
sgsn-global
dscp-templatetemplate_name
control-packet qos-dscp { af11 | af12 | af13 | af21 | af22 | af23 | af31 | af32 | af33 | af41 | af42 | af43
| be | cs1 | cs2 | cs3 | cs4 | cs5 | cs6 | cs7 | ef }
exit
The following command is used to configure the QoS DSCP value to "BE" (Best Effort):
config
context context_name
sgsn-global
dscp-templatetemplate_name
default control-packet
exit
The following configuration procedure is used to configure DSCP value for 3GPP QoS class downlink
data packets:
config
context context_name
sgsn-global
dscp-templatetemplate_name
data-packet { background | conversationa | interactive { priority1 | priority2 | priority3 } | streaming
} qos-dscp { af11 | af12 | af13 | af21 | af22 | af23 | af31 | af32 | af33 | af41 | af42 | af43 | be | cs1 | cs2 |
cs3 | cs4 | cs5 | cs6 | cs7 | ef }
exit
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The following command is used to configure the QoS DSCP value to "BE" (Best Effort):
config
context context_name
sgsn-global
dscp-templatetemplate_name
default data-packet { background | conversationa | interactive { priority1 | priority2 | priority3 } |
streaming }
exit
3 The associate-dscp-template command
To associate a specific DSCP template with a specific service configuration (for example GPRS Service,
IuPS Service, SGSN PSP Service) use the associate-dscp-template command.
GPRS Service Configuration Mode:
config
context context_name
gprs-service service_name
associate-dscp-template downlink template_name
exit
To disassociate a previously associated DSCP marking template:
config
context context_name
gprs-service service_name
no associate-dscp-template downlink
exit
IuPS Service Configuration Mode:
config
context context_name
iups-service service_name
associate dscp-template downlink dscp_template_name
exit
To disassociate a previously associated DSCP marking template:
config
context context_name
iups-service service_name
no associate dscp-template downlink
exit
SGSN PSP Configuration Mode:
config
context context_name
ss7-routing-domain routing_domain_id variant variant_type
associate { asp instance asp_num | dscp-template downlink template_name }
exit
To disassociate a previously associated DSCP marking template:
config
context context_name
ss7-routing-domain routing_domain_id variant variant_type
no associate [ asp | dscp-template downlink ]
exit
4 The peer-nse command, to associate DSCP template for NSEI
By using this command, a specific DSCP marking template can be identified to be associated with the
peer-NSE. The DSCP template must first be created with SGSN Global configuration mode and then
defined with the commands in the DSCP Template configuration mode. The template provides a mechanism
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for differentiated services code point (DSCP) marking of control packets and LLC signaling messages on
Gb interfaces. The DSCP marking feature enables the SGSN to perform classifying and managing of
network traffic and to determine quality of service (QoS) for the interfaces to an IP network.
To associate a peer (remote) network service entity (NSEI) for a BSS with this GPRS service:
config
context context_name
gprs-service service_name
peer-nsei nse_id { associate dscp-template downlink template_name | lac lac_id rac rac_id | name
peer_nsei_name | pooled }
exit
To remove the specified configuration from this peer-nsei configuration:
config
context context_name
gprs-service service_name
no peer-nsei nse_id [ associate dscp-template downlink | lac lac_id rac rac_id | name | pooled ]
exit
5 The gtpc command
To configure the DSCP marking to be used when sending GTP-C messages originating from the Session
Manager and the SGTPC manager, use the following procedure:
config
context context_name
sgtp-service service_name
gtpc { bind address ipv4_address | dns-sgsn context context_name | echo-interval interval_seconds |
echo-retransmission { exponential-backoff [ [ min-timeout timeout_seconds ] [ smooth-factor
smooth_factor ] + ] | timeout timeout_seconds } | guard-interval interval_seconds | ignore
response-port-validation | ip qos-dscp dscp_marking | max-retransmissions max_retransmissions |
retransmission-timeout timeout_seconds | send { common flags | rab-context |
target-identification-preamble } }
exit
To reset the values to the default configuration, use the following procedure:
config
context context_name
sgtp-service service_name
default gtpc { echo-interval | echo-retransmission | guard-interval | ignore response-port-validation
| ip qos-dscp | max-retransmissions | retransmission-timeout | send { common-flags | rab-context |
target-identification-preamble } }
exit
The default value is "BE" (Best Effort).
Important
To check values configured for DSCP templates, use the show sgsn-mode command.
Local QoS Capping
The QoS bit rate can be capped by the operator. The SGSN can be configured to limit the QoS bit rate parameter
when the subscribed QoS provided by the HLR is lower than the locally configured value. Based on the
configuration enabled, the SGSN can choose the QoS parameter configuration from the HLR configuration
or from the local settings used in the APN profile. During session establishment the SGSN applies the lower
of the two, that is either the HLR subscription or locally configured value.
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The following procedure is used to configure the local Traffic Class (TC) parameters:
Important
To enable any of the values/features configured with this command, the qos prefer-as-cap configuration
(also in the APN profile configuration mode) must be set to either local or both-hlr-and-local.
config
apn-profile profile_name qos class { background | conversational | interactive | streaming } [
qualif_option ]
exit
To remove the previously defined TC parameters, use the following procedure:
config
apn-profile profile_name remove qos class { background | conversational | interactive | streaming }
[ qualif_option ]
exit
To specify the operational preferences of QoS Parameters (specifically the QoS bit rates), use the following
procedure:
config
apn-profile profile_name qos prefer-as-cap { both-hlr-and-local | both-hss-and-local {
local-when-subscription-not-available | minimum | subscription-exceed-reject } | hlr-subscription | local
}
exit
To remove all the previous configurations and reset the values to default, use the following procedure:
config
apn-profile profile_name remove qos prefer-as-cap
exit
QoS Management When UE is Using S4-interface for PDP Contexts
The SGSN uses the S4 interface with EPC network elements S-GW or P-GW. The QoS parameters used in
the EPC network are different from the ones used in GPRS/UMTS network. For more information refer to
the 3GPP TS 23.203 section 6.1.7.
EPC QoS Parameters
• QoS Class Identifier (QCI): The QCI is scalar that is used as a reference to node specific parameters
that control packet forwarding treatment (for example, scheduling weights, admission thresholds, queue
management thresholds, link layer protocol configuration and so on.) and that have been pre-configured
by the operator owning the node (for example, eNodeB). The standardized characters associated with a
standard QCI are listed below:
◦Resource Type (GBR or Non-GBR)
◦Priority
◦Packet Delay Budget
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◦Packet Error Loss Rate
Figure 72: QCI table
• APN AMBR: The APN-AMBR limits the aggregate bit rate that can be provided across all Non- GBR
PDP contexts of the same APN (for example, excess traffic may get discarded by a rate shaping function).
Each of those Non-GBR PDP contexts can potentially utilize the entire APN AMBR (for example, when
the other Non-GBR PDP contexts do not carry any traffic). The GBR PDP contexts are outside the scope
of APN AMBR. The PGW enforces the APN AMBR in downlink. Enforcement of APN AMBR in
uplink may be done in the UE and additionally in the PGW.
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• UE AMBR: The UE AMBR limits the aggregate bit rate that can be provided across all Non-GBR PDP
contexts of a UE (for example, excess traffic may get discarded by a rate shaping function). Each of the
Non-GBR PDP contexts can potentially use the entire UE AMBR (for example, when the other Non-GBR
PDP contexts do not carry any traffic). The GBR (real-time) PDP contexts are outside the scope of UE
AMBR. The RAN enforces the UE AMBR in uplink and downlink.
• E-ARP: The EPC uses Evolved ARP, which has priority level ranging from "1" up to "15". Additionally,
evolved ARP comprises of pre-emption capability and pre-emption vulnerability. The preemption
capability information defines whether a bearer with a lower priority level should be dropped to free up
the required resources. The pre-emption vulnerability information indicates whether a bearer is applicable
for such dropping by a preemption capable bearer with a higher priority value.
For handover between UTRAN/GERAN and E-UTRAN, refer to 3GPP TS 24.101 "Annexure-E". It
defines the mapping rule between ARP and Evolved ARP during R99 QoS to EPS bearer QoS mapping
and vice versa.
• MBR: Maximum Bit Rate indicates the maximum number of bits delivered to the network or by the
network within a period of time. This parameter is as defined in GMM QoS Parameters. In EPC, these
values are encoded as a "5" octet linear value but in GMM QoS it is a single octet or a two octet step
wise value.
• GBR: Guaranteed Bit Rate indicates the guaranteed number of bits delivered to the network or by the
network within a period of time. This parameter is as defined in GMM QoS Parameters. In EPC, these
values are encoded as a "5" octet linear value but in GMM QoS it is a single octet or a two octet step
wise value.
Subscription Types Supported by S4-SGSN
1 EPC Subscription: If a subscriber has an EPC subscription, the QoS in subscription data is sent in the
EPC format.
2 GPRS Subscription: If the subscriber does not have an EPC subscription, the QoS in subscription data
is sent in R99/R5/R7 format.
QoS Mapping
The S4-SGSN communicates the QoS parameters towards the S-GW and P-GW in EPC QoS.In UTRAN /
GERAN access, the QoS carried over NAS messages to UE are in legacy GMM QoS R99/R5/R7 format
(Refer to, 3GPP TS 24.008 section 10.5.6.5). However on the S4 / S5 / S16 / S3 interfaces the QoS is carried
in EPC format (APN-AMBR, E-ARP and so on). A mapping is required between EPC QoS and GMM QoS,
this mapping for EPS QoS to pre-release 8 QoS is defined in 3GPP TS 23.401, Annexure E.
Mapping Details
Information on the parameters mapped is listed below:
• APN-AMBR is mapped to MBR for non-GBR bearers.
• Per bearer MBR and GBR is mapped to MBR and GBR towards UE for GBR bearers.
• For information on other mapping values refer to, 3GPP TS 23.203, table 6.1.7.
Mapping is performed during the following scenarios:
• During Activate Accept (EPC QoS to GMM QoS)
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• During Activation initiated Create Session Request (if GPRS subscription is used GMM QoS to EPC
QoS mapping)
• During S4-SGSN to Gn SGSN handover (EPC QoS to GMM QoS)
• During HLR / HSS initiated QoS modification (if GPRS subscription is used GMM to EPC QoS towards
SGW/PGW; towards UE EPC to GMM QoS for both types of subscription)
Calculation on UE-AMBR
The S4-SGSN sets the value of UE-AMBR as follows:
Value of used UE-AMBR = Sum of APN-AMBRs of all active PDN connections for the given UE, limited
or capped by the subscribed UE-AMBR.
For more information refer to, 3GPP TS 23.401, section 4.7.3.
Important
Local capping of UE-AMBR will be applicable in the upcoming software releases.
The calculated UE-AMBR is communicated to the RNC. The RNC enforces the UE level aggregate bit
rate in both uplink and downlink directions. The RNC has to be R9 compliant. This functionality of sending
IE to RNC will not be supported on release 15.0, it is planned for future releases.
To obtain E-ARP when GPRS subscription is used
To obtain E-ARP, configure ARP high and medium priority values at the Call Control Profile through the
CLI command listed below:
qos gn-gp { arp high-priority priority medium-priority priority | pre-emption { capability {
may-trigger-pre-emption | shall-not-trigger-pre-emption } | vulnerability { not-pre-emptable |
pre-emptable }
For more information refer to, 3GPP TS 23.401, Annexure E
To obtain QCI when GPRS subscription is used
The mapping information on obtaining QCI when GPRS subscription is used is listed in 3GPP TS 23.401
(table E.3) and 3GPP TS 23.203 (table 6.1.7).
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QoS Mapping from SGSN to SGW/PGW
The QoS Mapping from SGSN to SGW/PGW can be depicted as follows:
Figure 73: QoS Mapping from SGSN to SGW/PGW
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QoS Mapping from SGSN to UE/RNC
The QoS Mapping from SGSN to UE/RNC can be depicted as follows:
Figure 74: QoS Mapping from SGSN to UE/RNC
Important
QoS in GMM is an encoded octet. QoS in EPC is a linear "4" octet value in kbps. It is not possible to
encode an odd value like "8991" kbps in GMM QoS.
QoS Handling Scenarios
Listed below are various QoS handling scenarios and QoS Mapping for each of the scenarios:
Scenario-1:
Description of the scenario:
1 Attach is received from an EPC capable UE.
2 The HLR subscription does not have EPS subscription data. Only GPRS subscription is present.
3 Activate a PDP context with all QoS parameters set to "subscribed".
Important
For this scenario, PDP context activation through Gn/Gp interface by default is not done. Instead a S4
election is done as the UE is EPC capable. However, if the local operator policy overrides this to select
Gn/Gp, then Gn/Gp is preferred.
QoS mapping for the scenario:
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If S4 is the selected interface, then the subscribed MBR is mapped to APN AMBR. The EPS bearer QoS
MBR is set to subscribed MBR (for conversational and streaming class bearers). For non-GBR bearers the
EPS bearer QoS MBR is set to "0". If the traffic class is conversational or streaming, then the EPS bearer QoS
GBR is set to subscribed GBR.
A detailed list of mapping:
1 APN AMBR = Subscribed MBR
2 Bearer QoS PVI = Taken from local policy [use call-control-profile qos gn-gp config]
3 Bearer QoS PCI = Taken from local policy [use call-control-profile qos gn-gp config]
4 Bearer QoS PL = Taken from local policy [use call-control-profile qos gn-gp config]
5 Bearer QoS QCI = Mapped from subscribed traffic class
6 Bearer QoS MBR UL and DL = Mapped from subscribed MBR + MBR-Extended for UL and DL
7 Bearer QoS GBR UL and DL = Zero for interactive or background traffic. For streaming or conversational
it is mapped from subscribed GBR + Ext.GBR UL / DL
References:
3GPP TS 23.401 Annexure E and 3GPP TS 29.274 section 8.15.
Scenario-2:
Description of the scenario:
The scenario is same as Scenario-1 described above, the only change being inclusion of sending activate
accept to UE.
1 Attach is received from an EPC capable UE.
2 The HLR subscription does not have EPS subscription data. Only GPRS subscription is present.
3 Activate a PDP context with all QoS parameters set to "subscribed".
Important
For this scenario, PDP context activation through Gn/Gp interface by default is not done. Instead a S4
election is done as the UE is EPC capable. However, if the local operator policy overrides this to select
Gn/Gp, then Gn/Gp is preferred.
QoS mapping for the scenario:
After the create session response is received from the S-GW, the following mapping shall be used to send the
QoS towards UE:
1 Traffic Class = Mapped from QCI based on Table E.3 in 3GPP TS 23.401.
2 Delivery Order = Taken from local configuration [apn-profile --> qos --> class [traffic class] --> sdu -->
delivery order]
3 Delivery of erroneous SDU = Taken from local configuration [apn-profile --> qos --> class [traffic class]
--> sdu --> erroneous]
4 Maximum SDU Size = [apn-profile --> qos --> class [traffic class] --> sdu --> max size]
5 MBR Uplink = APN-AMBR-UL (if traffic class = interactive /background) or Bearer MBR-UL (if TC =
streaming / conversational)
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6 MBR DL = APN-AMBR-DL (if traffic class = interactive /background) or Bearer MBR-DL (if TC =
streaming / conversational)
7 Residual BER = Taken from local config [apn-profile-->qos-->class [tc] --> residual-bit-error-rate
8 SDU error ratio = Mapped based on Table 6.1.7 in 3GPP TS 23.203
9 Transfer delay = Mapped based on Table 6.1.7 in 3GPP TS 23.203
10 THP = Mapped from QCI based on Table E.3 in 3GPP TS 23.401
11 GBR UL = "0" for interactive or background class traffic. Mapped from Bearer QoS GBR UL for
conversational or streaming traffic.
12 GBR DL = "0" for interactive or background class traffic. Mapped from Bearer QoS GBR DL for
conversational or streaming traffic.
13 Signaling Indication = Mapped from QCI as per Table E.3 3GPP TS 23.401
14 Extended bit rates will be present if the mapped MBR / GBR exceeds "8640" Kbps
Scenario-3:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription does not have EPS subscription data. Only GPRS subscription data is present.
3 A primary PDP context is activated with all QoS parameters set to some requested values.
QoS mapping for the scenario:
1 Negotiate the requested QoS with subscribed QoS. Map the negotiated QoS as described in Scenario-1.
2 After receiving a Create Session Response, map the accepted EPS QoS to R99+ QoS as described in
Scenario-2 and send the Activate accept.
Scenario-4:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription has EPS subscription data.
3 A PDP context is activated with all QoS parameters set to "Subscribed" values or some requested values.
QoS mapping for the scenario:
1 For every primary PDP context to an APN, the EPS subscribed QoS is used as is.
2 Once the EPS bearer is activated, the Activate PDP Accept is sent by mapping the accepted QoS value as
described in Scenario-2.
Scenario-5:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription has EPS subscription data.
3 A secondary PDP context is activated with all QoS parameters set to "Subscribed" values.
QoS mapping for the scenario:
The SGSN sends a Bearer Resource Command with the following parameters:
1 Linked EPS Bearer ID = EPS bearer ID of linked Primary PDP
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2 PTI = Transaction ID received from the MS (In MME, the received PTI is used in the NAS message as
the PTI towards S-GW. But for the SGSN PTI is not there in the NAS message. The 3GPP TS is not clear
on what the SGSN should send as PTI, therefore TI is sent.
Flow QoS:
1
2
3
4
5
6
Important
QCI = Mapped from requested Traffic Class, if TC= conversational / streaming
MBR UL = APN-AMBR last received from P-GW for primary PDP activation
MBR DL = APN-AMBR last received from P-GW for primary PDP activation
GBR UL = APN-AMBR last received from P-GW for primary PDP activation
GBR DL = APN-AMBR last received from P-GW for primary PDP activation
Else, the values will be MBR UL = "0", BR DL ="0", GBR UL = "0", GBR DL = "0"
The value sent in the Flow QoS does not have any impact as it is the P-GW which decides the correct
QoS value to be provided. If the requested QoS is set to "subscribed" then as a placeholder value the
APN-AMBR value is sent as the MBR and GBR values.
References:
3GPP TS 23.401 Annexure E and 3GPP TS 29.274 (sections 8.15 and 8.16).
Scenario-6:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription has EPS subscription data.
3 A secondary PDP context is activated with all QoS parameters set to specified values.
QoS mapping for the scenario:
The SGSN sends a Bearer Resource Command with the following parameters:
1 Linked EPS Bearer ID = EPS bearer ID of linked Primary PDP
2 PTI = Transaction ID received from the MS (In MME, the received PTI is used in the NAS message as
the PTI towards S-GW. But for the SGSN PTI is not there in the NAS message. The 3GPP TS is not clear
on what the SGSN should send as PTI, therefore TI is sent.
Flow QoS:
1 QCI = Mapped from requested Traffic Class, if TC= conversational or streaming.
2 MBR UL = Requested MBR UL, MBR DL = Requested MBR DL
3 GBR UL = Requested GBR UL, GBR DL = Requested GBR DL or GBR UL = "0", GBR DL = "0"
Important
If the traffic class is conversational or streaming, the requested MBR or GBR values can be greater than
the subscribed APN-AMBR.
References:
3GPP TS 23.401 Annexure E and 3GPP TS 29.274 (sections 8.15 and 8.16)
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QoS Handling Scenarios
Scenario-7:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription does not have EPS subscription data.
3 A secondary PDP context is activated with all QoS parameters set to "Subscribed".
QoS mapping for the scenario:
The SGSN sends a Bearer Resource Command with the following parameters:
1 Linked EPS Bearer ID = EPS bearer ID of linked Primary PDP
2 PTI = Transaction ID received from the MS (In MME, the received PTI is used in the NAS message as
the PTI towards S-GW. But for the SGSN PTI is not there in the NAS message. The 3GPP TS is not clear
on what the SGSN should send as PTI, therefore TI is sent.
Flow QoS:
1
2
3
4
5
6
QCI = Mapped from requested Traffic Class, if TC= conversational or streaming
MBR UL = APN-AMBR-UL last obtained from P-GW for primary
MBR DL = APN-AMBR-DL last obtained from P-GW for primary
GBR UL = APN-AMBR-UL last obtained from P-GW for primary
GBR DL = APN-AMBR-UL last obtained from P-GW for primary
Else, MBR UL = "0", MBR DL = "0", GBR UL = "0", GBR DL = "0"
Scenario-8:
Description of the scenario:
1 Attach is received from an EPC capable UE
2 The HLR subscription does not have EPS subscription data.
3 A secondary PDP context is activated with all QoS parameters set to valid requested values.
QoS mapping for the scenario:
Cap the requested QoS with the subscribed QoS. Then use the negotiated QoS as described below, the SGSN
sends a Bearer Resource Command with the following parameters:
1 Linked EPS Bearer ID = EPS bearer ID of linked Primary PDP
2 PTI = Transaction ID received from the MS (In MME, the received PTI is used in the NAS message as
the PTI towards S-GW. But for the SGSN PTI is not there in the NAS message. The 3GPP TS is not clear
on what the SGSN should send as PTI, therefore TI is sent.
Flow QoS:
1
2
3
4
5
6
QCI = Mapped from requested Traffic Class, if TC= conversational or streaming
MBR UL = MBR-UL negotiated
MBR DL = MBR-DL negotiated
GBR UL = GBR-UL negotiated
GBR DL = GBR-DL negotiated
Else, MBR UL = "0", MBR DL = "0", GBR UL = "0", GBR DL = "0"
Scenario-9:
Description of the scenario:
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QoS Handling Scenarios
In-bound RAU or Forward Relocation Request for a subscriber, who was earlier attached on a Gn/Gp SGSN.
Important
This scenario is currently not supported.
QoS mapping for the scenario:
1 APN-AMBR-UL = Subscribed MBR-UL
2 APN-AMBR-DL = Subscribed MBR-DL
3 Bearer QoS MBR = Negotiated MBR received from peer SGSN Bearer QoS GBR = "0", for Interactive
or Background traffic classes and it is Negotiated GBR value for Conversational or Streaming traffic
classes.
4 Bearer QoS - PVI = Use from Local Policy (use call-control-profile qos gn-gp configuration)
5 Bearer QoS - PCI = Use from Local Policy (use call-control-profile qos gn-gp configuration)
6 Bearer QoS - PL = Use from Local Policy (use call-control-profile qos gn-gp configuration), based on the
negotiated ARP received.
7 Bearer QoS - QCI = Mapped from negotiated traffic class.
References:
3GPP TS 23.401 Annexure E and 3GPP TS 23.060 v8.9.0 (section 6.9.1.2.2.a)
Scenario-10:
Description of the scenario:
Outbound RAU or Forward Re-location Request is sent towards a Gn/Gp SGSN.
QoS mapping for the scenario:
1
2
3
4
5
Subscribed QoS = Mapped from subscribed EPS QoS
Requested QoS = Return the MS requested value
Negotiated QoS = Mapped from the current EPS QoS
The mapping of EPS QoS to pre- release "8" QoS is as described in scenario-2.
When mapping subscribed EPS QoS to pre-release "8" MBR and GBR the following rules are applied:
• MBR-UL = APN-AMBR-UL
• MBR-DL = APN-AMBR-DL
• GBR-UL / DL = "0" (for TC = interactive / background)
• GBR-UL / DL = APN-AMBR-UL / DL (for TC = interactive / background)
Scenario-11:
Description of the scenario:
Initiating modify a PDP towards UE from SGSN (for instances of P-GW initiated QoS modification, HSS
initiated modification and so on.)
QoS mapping for the scenario:
The current EPS QoS at SGSN is mapped to pre-release "8" QoS as described in Scenario-2.
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QoS Handling During Primary PDP Activation
Important
QoS in GMM is an encoded octet. QoS in EPC is a linear "4" octet value in kbps. It is not possible to
encode an odd value like "8991" kbps in GMM QoS.
QoS Handling During Primary PDP Activation
QoS Handling When EPS Subscription is Available
1 The subscribed APN-AMBR and ARP values are sent in Create Session Request to SGW or PGW.
2 The PGW can change the APN-AMBR value in Create Session Response.
3 The SGSN accepts the APN-AMBR value sent by the PGW. No further negotiation happens as described
in 3GPP TS 23.060 section 9.2.2.1A, list item "d".
4 In most cases the S4-SGSN does not perform any further QoS negotiation. (However, there is a special
case of SGSN capping the bit rate sent to RAN at 16Mbps. This requirement will be supported in future
releases).
5 The S4-SGSN maps the received APN-AMBR to MBR values as per the mapping table provided in 3GPP
TS 23.203 Table 6.1.7 and 3GPP TS 23.401 Annex E.
6 The mapped MBR values are sent to the RNC in RAB assignment request and in Activate Accept to the
UE.
7 In Release 14.0 local override of APN-AMBR / ARP based on CLI configuration is supported.
QoS Handling When Only GPRS Subscription is Available
1 The requested QoS from UE and the subscribed QoS are negotiated, the SGSN chooses the least of the
two values as the negotiated output. If the requested QoS is the Subscribed QoS, the SGSN chooses the
Subscribed QoS as is. If any local QoS capping is configured, the Negotiated QoS is the least of Requested
QoS or Subscribed QoS capped by local values).
2 The Negotiated QoS is mapped to EPC QoS as per the mapping table in 3GPP TS 23.203 Table 6.1.7 and
3GPP TS 23.401 Annexure E.
3 The mapped values are sent in Create Session Request to the SGW or PGW.
4 The PGW is allowed to change the APN-AMBR value in Create Session Response.
5 The SGSN accepts the APN-AMBR value sent by the PGW. No further negotiation happens as described
in 3GPP TS 23.060 section 9.2.2.1A, list item "d".
6 The S4-SGSN maps the received the APN-AMBR to MBR value as per the mapping table described in
3GPP TS 23.203 table 6.1.7 and 3GPP TS 23.401 Annexure "E".
7 The mapped MBR values are sent to the RNC in RAB assignment request and in Activate Accept to UE.
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QoS Handling During Secondary PDP Activation
QoS Handling During Secondary PDP Activation
QoS Handling When EPS Subscription is Available
1 The Requested QoS is mapped to EPC QoS and sent in the Bearer Resource Command to the SGW or
PGW.
2 If the traffic class requested is a non-GBR traffic class (interactive / background), the per bearer MBR /
GBR values sent in Bearer Resource Command will all be zeroes.
3 The PGW sends a Create Bearer Request to the SGW or SGSN.
4 The SGSN sends a RAB assignment request to the RNC by mapping QoS as follows:
a If the bearer is a non-GBR: The APN-AMBR is mapped to MBR values and GBR is set to "0".
b If the bearer is GBR: The MBR / GBR values received in Create Bearer Request are sent to RNC / UE
in the Secondary Activate Accept.
QoS Handling When Only GPRS Subscription is Available
1 The Requested QoS from the UE and the Subscribed QoS are negotiated. The SGSN chooses the least of
the two values as the negotiated output. If the Requested QoS is mentioned as the Subscribed QoS, then
the SGSN chooses the Subscribed QoS as is, if local QoS capping is not configured.
2 The Requested QoS is mapped to the EPC QoS and sent in the Bearer Resource Command to the SGW
or PGW.
3 If the traffic class requested is a non-GBR traffic class (interactive / background), the per bearer MBR /
GBR values sent in Bearer Resource Command will be all zeroes.
4 The PGW sends a Create Bearer Request to SGW or SGSN.
5 The SGSN sends a RAB assignment request to the RNC by mapping QoS as follows:
a If the bearer is non-GBR: The APN-AMBR is mapped to MBR values and the GBR value is set to
"0".
b If the bearer is GBR: The MBR / GBR values received in the Create Bearer Request will be sent to
RNC / UE in Secondary Activate Accept.
MS Initiated QoS Modification
• The MS sends a Modify PDP Context Request (TI, QoS Requested, TFT, and Protocol Configuration
Options) message to the SGSN. Either QoS Requested or TFT or both may be included. The QoS
Requested indicates the desired QoS profile, while the TFT indicates the TFT that is to be added or
modified or deleted from the PDP context. Protocol Configuration Options may be used to transfer
optional PDP parameters and/or requests to the PGW.
• The SGSN identifies the bearer modification scenario that applies and sends the Bearer Resource
Command (TEID, LBI, PTI, EPS Bearer QoS (excluding ARP), TFT, EBI, RAT type, Protocol
Configuration Options, serving network identity, CGI/SAI, User CSG Information, MS Info Change
Reporting support indication, DL TEID and DL Address, DTI) message to the selected Serving GW.
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MS Initiated QoS Modification
◦An S4-based SGSN applies the BCM 'MS/NW' whenever the S4 is selected for a certain MS. The
following table list the details of MS-initiated EPS bearer modification, MS/NW mode:
Table 28: MS-initiated EPS bearer modification, MS/NW mode
Sl No.
PDP context modification use Information provided by SGSN
case
at S4 signaling
1.
Add TFT filters and increase
QoS
2.
Increase of QoS related to one QoS related to EPS Bearer
or more TFT filter(s)
filters, Impacted TFT filters,
TEID, EPS Bearer ID
3.
Increase of QoS, TFT filters
not specified
Not allowed in MS/NW mode
4.
Add/remove TFT filters, no
QoS change
TFT filters added/removed,
TEID, EPS Bearer ID
5.
Decrease QoS related to one or QoS related to EPS Bearer
more TFT filter(s)
filters, Impacted TFT filters,
TEID, EPS Bearer ID
6.
Remove TFT filters and
decrease QoS
QoS related to EPS Bearer,
TFT filters removed, TEID,
EPS Bearer ID
7.
Decrease of QoS, TFT filters
not specified
Not allowed in MS/NW mode
QoS related to EPS Bearer,
TFT filters added, TEID, EPS
Bearer ID
Note: Only the modified QCI and/or GBR parameters are forwarded by the SGSN.
• The S4-SGSN may assume that the BCM mode of a bearer is MS/NW there are instances where the
BCM mode negotiated between UE and PGW can be "UE only". In such cases, a UE sends a Modify
PDP Request to the SGSN without a TFT. But SGSN cannot honor it in a R9 capable network since
TAD is mandatory in BRC. In a R10 network, TAD is conditional optional on the S4 interface. Once
the EGTP stack is upgraded to R10 compliance, the S4-SGSN honors PDP modification without TFT.
For release 14.0, the SGSN rejects such PDP modifications.
• If the PDP modification is for non-GBR bearer, the SGSN sets the MBR and GBR values in Bearer
Resource Command to "0". If the PDP modification is for GBR bearer, then SGSN sets the MBR and
GBR values in Bearer Resource Command to the requested values.
• The Serving GW Forwards the message to the PGW.
• If the request is accepted, the PGW Initiated Bearer Modification Procedure is invoked by the PGW to
modify the EPS Bearer indicated by the TEID.
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HSS Initiated PDP Context Modification
◦The PDN GW sends an Update Bearer Request (TEID, EPS Bearer Identity, PTI, EPS Bearer QoS,
APN-AMBR, TFT, Protocol Configuration Options, Prohibit Payload Compression, MS Info
Change Reporting Action, and CSG Information Reporting Action) message to the Serving GW.
The Procedure Transaction Id (PTI) parameter is used to link this message to the Request Bearer
Resource Modification message received from the Serving GW.
• The Serving GW sends an Update Bearer Request (PTI, EPS Bearer Identity, EPS Bearer QoS, TFT,
APN AMBR, Protocol Configuration Options, Prohibit Payload Compression, MS Info Change Reporting
Action, CSG Information Reporting Action) message to the SGSN.
• In Iu mode, radio access bearer modification may be performed by the RAB Assignment procedure. If
the radio access bearer does not exist, the RAB setup is done by the RAB Assignment procedure.
• The SGSN acknowledges the bearer modification by sending an Update Bearer Response (TEID, EPS
Bearer Identity, DL TEID and DL Address, DTI) message to the Serving GW.
• The Serving GW acknowledges the bearer modification by sending an Update Bearer Response (TEID,
EPS Bearer Identity) message to the PDN GW.
• The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns a Modify
PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id, and Protocol Configuration
Options) message to the MS.
HSS Initiated PDP Context Modification
• The Home Subscriber Server (HSS) initiated PDP context modification procedure is used when the HSS
decides to modify the subscribed QoS, where typically QoS related parameters are changed. The
parameters that may be modified are UE-AMBR, APN-AMBR QCI and Allocation/Retention Policy.
• The HSS initiates the modification by sending an Insert Subscriber Data (IMSI, Subscription Data)
message to the SGSN. The Subscription Data includes EPS subscribed QoS (QCI, ARP) and the
subscribed UE-AMBR and APN AMBR.
• The S4-SGSN then updates the stored Subscription Data and acknowledges the Insert Subscriber Data
message by returning an Insert Subscriber Data Ack (IMSI) message to the HSS and sends the Modify
Bearer Command (EPS Bearer Identity, EPS Bearer QoS, APN AMBR) message to the S-GW. The
S-GW forwards the Modify Bearer Command (EPS Bearer Identity, EPS Bearer QoS, APN AMBR)
message to the P-GW. Note that the EPS Bearer QoS sent in the Modify Bearer Command does not
modify the per bearer bit-rate. It is sent to carry only a change in the ARP / QCI received from
subscription. Also, the Modify Bearer Command can be sent only for the default bearer (primary PDP)
in a PDN connection.
• The P-GW modifies the default bearer of each PDN connection corresponding to the APN for which
subscribed QoS has been modified. If the subscribed ARP parameter has been changed, the P-GW shall
also modify all dedicated EPS bearers having the previously subscribed ARP value unless superseded
by PCRF decision. The P-GW then sends the Update Bearer Request (EPS Bearer Identity, EPS Bearer
QoS [if QoS is changed], TFT, APN AMBR) message to the S-GW.
• The S-GW sends the Update Bearer Request (EPS Bearer Identity, EPS Bearer QoS (if QoS is changed)
APN-AMBR, TFT) message to the SGSN. On completion of modification S4-SGSN acknowledges the
bearer modification by sending the "Update Bearer Response (EPS Bearer Identity)" message to P-GW
via S-GW. If the bearer modification fails, the P-GW deletes the concerned EPS Bearer.
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PGW Initiated QoS Modification
PGW Initiated QoS Modification
• The P-GW sends the Update Bearer Request (TEID, EPS Bearer Identity, EPS Bearer QoS, APN-AMBR,
Prohibit Payload Compression, MS Info Change Reporting Action, CSG Information Reporting Action,
TFT, and Protocol Configuration Options) message to the S-GW.
◦The TFT is optional and included in order to add, modify or delete the TFT related to the PDP
Context. Protocol Configuration Options is optional.
• The S- GW sends the Update Bearer Request (TEID, EPS Bearer Identity, EPS Bearer QoS, APN-AMBR,
Prohibit Payload Compression, MS Info Change Reporting Action, CSG Information Reporting Action,
TFT, and Protocol Configuration Options) message to the SGSN.
• In Iu mode, radio access bearer modification may be performed by the RAB Assignment procedure.
• The SGSN selects Radio Priority and Packet Flow Id based on the QoS Negotiated, and sends a Modify
PDP Context Request (TI, PDP Address, QoS Negotiated, Radio Priority, Packet Flow Id, TFT, and
PCO) message to the MS. The TFT is included only if it was received from the P-GW in the Update
Bearer Request message. Protocol Configuration Options are sent transparently through the SGSN.
• The MS should accept the PDP context modification requested by the network if it is capable of supporting
any modified QoS Negotiated as well as any modified TFT. For a successful modification the MS
acknowledges by returning a Modify PDP Context Accept message. If the MS is incapable of accepting
a new QoS Negotiated or TFT it shall instead de-activate the PDP context with the PDP Context
Deactivation Initiated by MS procedure.
• On receiving the Modify PDP Context Accept message, or on completion of the RAB modification
procedure, the SGSN returns an Update PDP Context Response (TEID, QoS Negotiated) message to
the S-GW.
• The S-GW acknowledges the bearer modification to the P- GW by sending an Update Bearer Response
(EPS Bearer Identity) message.
ARP Handling
Difference between Gn SGSN and S4 SGSN
In Create PDP Context response the GGSN sends {1, 2, and 3} as ARP value whereas the S-GW sends "15"
value ARP in Create Session response. In Gn SGSN while sending the RAB assignment request, the Allocation
retention priority values {1, 2, and 3} are mapped to "15" values so there is need of conversion from "3"
values to "15" values.
In S4 SGSN, since the P-GW sends ARP in the "15" value range there is no need for conversion.
ARP values in Gn SGSN
According to GTPv1 3GPP TS 29.060 clause 7.7.34 Allocation/ Retention priority encodes each priority level
defined in 3GPP TS 23.107 as the binary value of the priority level.
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ARP Handling
Quality of Service (QoS) Profile
The Quality of Service (QoS) Profile includes the values of the defined QoS parameters.
Octet "4" carries the Allocation/Retention priority octet that is defined in 3GPP TS 23.107. The
Allocation/Retention priority octet encodes each priority level defined in 3GPP TS 23.107 as the binary value
of the priority level.
The Allocation/Retention priority field is ignored by the receiver if:
• The QoS profile is pre-Release '99.
• The QoS profile IE is used to encode the Quality of Service Requested (QoS Req) field of the PDP
context IE.
Octet "5" the QoS Profile Data Field is coded according to the 3GPP TS 24.008 [5] Quality of Service IE,
octets 3-m. The minimum length of the field QoS Profile Data is "3" octets, the maximum length is "254"
octets.
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ARP Handling
The clause 11.1.6 "Error handling" defines the handling of the case when the sent QoS Profile information
element has a Length different from the Length expected by the receiving GTP entity.
Figure 75: Quality of Service (QoS) Profile Information Element
Figure 76: Value Ranges for UMTS Bearer Service Attributes
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ARP Handling
ARP values in S4 SGSN
The behavior of ARP values in S4 SGSN is according to GTPv2 3GPP TS 29.274 clause 8.15.
Bearer Quality of Service (Bearer QoS)
Bearer Quality of Service (Bearer QoS) is transferred through the GTP tunnels. The sending entity copies the
value part of the Bearer l QoS into the Value field of the Bearer QoS IE.
Figure 77: Bearer Level Quality of Service (Bearer QoS)
Octet "5" represents the Allocation/Retention Priority (ARP) parameter. The meaning and value range of the
parameters within the ARP are defined in 3GPP TS 29.212 [29]. The bits within the ARP octet are:
• Bit 1 - PVI (Pre-emption Vulnerability), see 3GPP TS 29.212[29], clause 5.3.47 Pre-emption-Vulnerability
AVP.
• Bit 2 - Spare bit.
• Bits 3 up to 6 - PL (Priority Level), see 3GPP TS 29.212[29], clause 5.3.45 ARP-Value AVP. Priority
Level encodes each priority level defined for the ARP-Value AVP as the binary value of the priority
level.
• Bit 7 - PCI (Pre-emption Capability), see 3GPP TS 29.212[29], clause 5.3.46 Pre-emption-Capability
AVP.
• Bit 8 - Spare bit.
Priority-Level AVP (All access types)
The values "1" up to "15" are defined, with value "1" as the highest level of priority.
Values "1" up to "8" should only be assigned for services that are authorized to receive prioritized treatment
within an operator domain. Values "9" up to "15" can be assigned to resources that are authorized by the home
network and thus applicable when a UE is roaming.
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Handling of ARP Values in Various Scenarios
Pre-emption-Capability AVP
PRE-EMPTION_CAPABILITY_ENABLED (0)
This value indicates that the service data flow or bearer which is allowed to get resources that were already
assigned to another service data flow or bearer with a lower priority level.
PRE-EMPTION_CAPABILITY_DISABLED (1)
This value indicates that the service data flow or bearer is not allowed to get resources that were already
assigned to another service data flow or bearer with a lower priority level. This is the default value applicable
if this AVP is not supplied.
Pre-emption-Vulnerability AVP
PRE-EMPTION_VULNERABILITY_ENABLED (0)
This value indicates that the resources assigned to the service data flow or bearer which can be pre-empted
and allocated to a service data flow or bearer with a higher priority level. This is the default value applicable
if this AVP is not supplied.
PRE-EMPTION_VULNERABILITY_DISABLED (1)
This value indicates that the resources assigned to the service data flow or bearer which shall not be pre-empted
and allocated to a service data flow or bearer with a higher priority.
Handling of ARP Values in Various Scenarios
Gn + GPRS Subscription
The following CLI command is used to send RAB parameters in RAB Assignment request:
config
apn-profile profile_name
ranap allocation-retention-priority-ie subscription-priority priority class { { background | conversational
| interactive | streaming } { not-pre-emptable | priority | queuing-not-allowed |
shall-not-trigger-pre-emptable } + }
exit
S4 + EPC subscription
For EPC subscription with S4 activation, ARP in RAB is filled from the Evolved ARP applied for the PDP
context. The Evolved ARP applied is:
• Subscribed Evolved ARP if P-GW does not send any evolved ARP in Create Session Response.
Or
• Evolved ARP supplied by the P-GW.
S4+GPRS Subscription
For GPRS subscription with S4 activation, the ARP in RAB is filled from the Evolved ARP applied for the
PDP context. The Evolved ARP applied is:
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Mapping EPC ARP to RANAP ARP
• Evolved ARP derived from the GPRS subscription using CLIs displayed below, when the P-GW does
not send any Evolved ARP in Create Session Response:
config
call-control-profile profile_name
qos { gn-gp | ue-ambr }
qos gn-gp { arp high-priority priority medium-priority priority | pre-emption { capability {
may-trigger-pre-emption | shall-not-trigger-pre-emption } | vulnerability { not-pre-emptable |
pre-emptable }
exit
Or
• Evolved ARP supplied by the P-GW.
The Evolved ARP applied is sent in RANAP towards the RNC.
Mapping EPC ARP to RANAP ARP
The ARP values are defined as per 3GPP TS 29.212 clause 5.3.46 and 5.3.47 for the Core Network Side.
The following values are defined:
• PRE-EMPTION_CAPABILITY_ENABLED (0)
This value indicates that the service data flow or bearer which is allowed to get resources that were
already assigned to another service data flow or bearer with a lower priority level.
• PRE-EMPTION_CAPABILITY_DISABLED (1)
This value indicates that the service data flow or bearer which is not allowed to get resources that were
already assigned to another service data flow or bearer with a lower priority level. This is the default
value applicable if this AVP is not supplied.
• PRE-EMPTION_VULNERABILITY_ENABLED (0)
This value indicates that the resources assigned to the service data flow or bearer which can be pre-empted
and allocated to a service data flow or bearer with a higher priority level. This is the default value
applicable if this AVP is not supplied.
• PRE-EMPTION_VULNERABILITY_DISABLED (1)
This value indicates that the resources assigned to the service data flow or bearer which shall not be
pre-empted and allocated to a service data flow or bearer with a higher priority level.
For more information on ARP values and their definitions see, 3GPP TS 25.413 clause 9.2.1.3.
The ARP values defined are different on the RNC side and the Core Network side, the RAB assignment
request is mapped according to the following table:
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ARP configured in CC Profile
Table 29: RAB Assignment Request Mapping
RAB parameters (ARP)
ARP values received from SGW
(According to 3GPP TS 29.212
clause5.3.46 and 5.3.47)
Mapping EPC ARP to RANAP ARP
in RNC side (According to RANAP
3GPP TS 25.413 clause 9.2.1.3)
Pre-emption-Capability
PRE-EMPTION_CAPABILITY_ENABLED Pre-emption is triggered.
(0)
Pre-emption-Capability
PRE-EMPTION_CAPABILITY_DISABLED Pre-emption is not triggered.
(1)
Pre-emption-Vulnerability
PRE-EMPTION_VULNERABILITY_ENABLED Pre-emption is triggered.
(0)
Pre-emption-Vulnerability
PRE-EMPTION_VULNERABILITY_DISABLED Pre-emption is not triggered.
(1)
ARP configured in CC Profile
The QoS configured in the Call Control Profile is used if the S4 interface is chosen for PDP activation, but
the subscription does not have an EPS subscription. Therefore, GPRS subscription data (which uses QoS in
pre-release 8 format), will be mapped to EPS QoS. The Allocation and Retention policy will be mapped to
EPS ARP using the configuration in the Call Control Profile.
If the QoS mapping configuration is not used, the following default mappings are used:
• Default ARP high-priority value = 5.
• Default ARP medium-priority value = 10.
• Default pre-emption capability = shall-not-trigger-pre-emption.
• .Default pre-emption vulnerability = not pre-emptable
The mapping is configured through the following CLI command:
config
call-control-profile <profile_name>
qos { gn-gp | ue-ambr }
qos gn-gp { arp high-priority priority medium-priority priority | pre-emption { capability {
may-trigger-pre-emption | shall-not-trigger-pre-emption } | vulnerability { not-pre-emptable |
pre-emptable }
exit
The mapping of these configured values to EPC ARP is given in below, this table is present 3GPP TS 23.401:
Table 30: Mapping of Release 99 bearer parameter ARP to EPS bearer ARP
Release 99 bearer parameter ARP value
EPS bearer ARP priority value
1
1
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ARP-RP Mapping for Radio Priority in Messages
Release 99 bearer parameter ARP value
EPS bearer ARP priority value
2
H+1
3
M+1
In the above table H = High-priority value configured and M = Medium-priority value.
ARP-RP Mapping for Radio Priority in Messages
The SGSN can choose a preferred radio priority according to the ARP values sent by the GGSN and HLR
using the ARP to RP mapping. These mappings will be used by the corresponding 2G and/or 3G services to
choose the radio priority value while triggering messages (such as those listed below) towards the MS/UE:
• Activate PDP Accept.
• Modify PDP Request during network-initiated PDP modification procedure.
• Modify PDP Accept during MS-initiated PDP modification procedure provided the ARP has been
changed by the network.
Important
In releases prior to 15.0 MR4 ER5, the Radio priority was hardcoded to "4" irrespective of ARP values
received by the SGSN from either a GGSN or an HLR.
The following commands are used to create profiles for mapping ARP to RP values and associate the mapping
with SGSN (3G) and GPRS (2G) services.
Use the following command in the SGSN Global configuration mode to create an ARP-RP mapping profile:
configure
sgsn-global
qos-arp-rp-map-profile arp_profile_name
no qos-arp-rp-map-profile arp_profile_name
end
Notes:
• arp_profile_name - Enter a string of 1 to 64 alphanumeric characters to identify the mapping profile
and moves into the ARP-RP mapping profile configuration mode.
• no qos-arp-rp-map-profile - Removes the profile definition from the configuration.
When the ARP-RP mapping profile is created, the default ARP-RP mapping is automatically included (see
default values in the Notes section below). This arp command, in the ARP-RP mapping profile configuration
mode, modifies the ARP-RP mapping for the profile.
configure
sgsn-global
qos-arp-rp-map-profile arp_profile_name
arparp_value radio-priority rp_value
end
Notes:
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ARP-RP Mapping for Radio Priority in Messages
• arp_value - Defines the allocation retention priority. Enter an integer from 1 to 3.
• rp_value - Defines the radio priority. Enter an integer from 1 to 4.
• Default ARP-RP mapping would be
◦ARP1 RP4
◦ARP2 RP4
◦ARP3 RP4
• Use the show sgsn-mode command to display the ARP-RP profile and configuration.
The radio-priority keyword in the sm commands in both the GPRS-Service and SGSN-Service configuration
modes. This keyword is used to associate an ARP-RP mapping profile with a 2G and/or a 3G service.
configure
context context_name
gprs-service service_name
sm radio-priority from-arp arp_profile_name
no sm radio-priority from-arp arp_profile_name
end
Notes:
• This example illustrates the GPRS Service configuration mode, but either GPRS or SGSN Service
configuration modes could be entered. The command sequent would have to be repeated, once for each
type of service, to associate the ARP-RP profile with both types of services.
• no sm radio-priority from-arp - This command will remove the association from the configuration.
• Use the show configuration command to display the association.
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31
RIM Message Transfer from BSC or RNC to
eNodeB
This chapter describes how the SGSN transfers RIM messages to/from an MME (eNodeB) via GTPv1
protocol. It also provides details about RIM messages transferred to/from an MME (eNodeB).
• Feature Description, page 425
• How It Works, page 426
• Configuring RIM Msg Transfer to or from eNodeB, page 429
• Monitoring and Troubleshooting RIM Msg Transfer, page 430
Feature Description
RIM message transfer is one of the standards-based RAN Information Management procedures supported by
the SGSN.
RAN Information Management (RIM)
RIM procedures provide a generic mechanism for the exchange of arbitrary information between RAN nodes.
The RAN information is transferred via the SGSN core network node(s). In order to make the RAN information
transparent for the core network, the RAN information is included in a RIM container that shall not be
interpreted by the core network nodes.
The RAN information is transferred in RIM containers from the source RAN node to the destination RAN
node by use of messages. The SGSN independently routes and relays each message carrying the RIM container.
In pre-15.0 releases, the SGSN supported RIM messages from BSS/RNC to another BSS/RNC belonging to
a different or the same SGSNover GTPv1 protocol. Now, the SGSN also supports transfer of RIM messages
to/from an MME (eNodeB) via GTPv1 protocol.
The SGSN uses existing CLI to enable the RIM transfer functionality. Whether or not the RIM message goes
from/to BSC/RNC to/from BSC/RNC or to/from eNodeB is determined by the addressing. To transfer RIM
messages to the MME (eNodeB),
• requires RIM functionality be enabled for the SGSN.
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Relationships to Other Feature or Products
• requires the DNS server be configured to respond to a TAI-based DNS query
OR
• requires the MME (eNodeB) address be added to the SGSNs Call Control Profile
Relationships to Other Feature or Products
For this feature to work properly, the peer-MME for the eNodeB must also support RIM message handling.
How It Works
RIM Addressing
All the messages used for the exchange of RAN information contain the addresses of the source and destination
RAN nodes. An eNodeB is addressed by tracking area identity (TAI) + eNodeB Identity (enbId).
The source RAN node sends a message to its SGSN including the source and destination addresses. From the
destination address, the SGSN shall decide whether or not it is connected to the destination RAN node. If the
destination address is that of an eNodeB, then the SGSN uses the destination address to route the message,
encapsulated in a GTPv1 message, to the correct MME via the Gn interface.
The MME connected to the destination RAN node decides which RAN node to send the message based on
the destination address or the RIM routing address.
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Call Flows - Transmitter of GTP RIM Msg
Call Flows - Transmitter of GTP RIM Msg
The following call flow illustrates how the SGSN behaves as the transmitter of GTP RIM messages.
Figure 78: Transmitting RIM Message
In the above illustration, the RIM message is transferred to the peer SGSN as follows:
1 Upon receiving a RIM message from the network access BSS/RNC, the SGSN determines the RIM routing
address type. If the message indicates that the target is an eNodeB, then SGSN searches for a locally
configured MME address.
2 If a locally configured MME address is not available, then a DNS-SNAPTR query will be initiated to
determine the MME address.
3 On receiving the DNS response and upon getting a valid MME address, an appropriate GTP API would
be invoked.
4 On invocation of this API the GTP module will encode the RAN info relay message (as per TS 29.060)
and dispatch the PDU to the peer MME.
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Call Flows - Receiver of GTP RIM Msg
Call Flows - Receiver of GTP RIM Msg
The following call flow illustrates how the SGSN behaves as the receiver of GTP RIM messages.
Figure 79: Receiving a GTP RIM Message
In this case, the SGSN has to decode the incoming GTP message correctly and forward the RIM message to
the destination RNC/BSS.
1 SGSN would decode the received GTP RAN info relay message and construct a RANAP or BSSGP RIM
message.
2 Appropriate actions would be taken to forward the RIM message to the destination RNC/BSS.
RIM Application
The RIM application processes the decoded RIM PDU from the access application. The routing area identifier
(RAI) -- comprised of the mcc, mnc, rac -- is extracted from the destination address and is used to decide if
the target routing area (RA) is local. If the RAI is locally available, the PDU is forwarded to either the RANAP
or BSSGP stack based on the RIM routing address discriminator field.
The SGSN has a global list of local RAs. Each RA in turn has a list of RNCs and NSEIs that control it. If the
destination RA is local, the list of NSEIs which serve the RAI is fetched. Each NSEI is searched for a matching
cell id in the cellid-list. The PDU is then forwarded to the NSEI when signaling the BVCI.
If the RNC Id is in the destination cell identifier, then the IuPS service serving the local RAI is identified.
The PDU is encoded in a RIM container and forwarded to the corresponding RANAP stack instance of that
IuPS service.
If the eNodeB Id is in the destination cell identifier, then the PDU will be sent to the GTP app using the
appropriate event.
The peer-MME address is resolved using the SGSN's local configuration or a DNS query for the TAI present
in the destination address. For a successful DNS response, the PDU is encoded in a GTP RIM container and
forwarded to the peer-MME. The SGTP service used will be the default SGTP service associated with the
GPRS service or the SGSN service under which the source BSS/RNC was present. The RIM app drops a PDU
if the DNS response fails. There will no retransmission or state-maintenance for the RIM PDU at the GTP-app.
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Standards Compliance
Standards Compliance
The SGSN's RIM message transfer from/to eNodeB functionality complies with the following standards:
• 3GPP TS 29.060 version 11
• 3GPP TS 23.003 version 11
• 3GPP TS 25.413 version 11
• 3GPP TS 48.018 version 11
• 3GPP TS 24.008 version 11
Configuring RIM Msg Transfer to or from eNodeB
To enable successful RIM message transfer to/from an eNodeB, the following must be included in the SGSN's
configuration:
• Configuring RIM functionality to work on SGSN
• Associating previously configured SGTP and IuPS services
• Configuring the peer-MME's address, in one or both of two ways
◦Configuring the peer-MME address locally
◦Configuring the DNS server
Configuring RIM Functionality
The following command sequences are used to enable RAN information management (RIM) functionality
on the SGSN. The order in which these two configurations are performed is not significant.
The first command sequence enables RIM for the entire SGSN (global level).
configure
sgsn-global
ran-information-management
end
The second command sequence associates the RNC configuration, the part of the IuPS service configuration
governing the SGSN communication with any RNC, needs to have the RIM functionality enabled.
configure
context context_name
iups-service service_name
rnc id rnc_id
ran-information-management
end
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Associating Previously Configured SGTP and IuPS Services
Associating Previously Configured SGTP and IuPS Services
The SGTP service configuration is a mandatory part of the SGSN's setup (refer to Configuring an SGTP
Service in the SGSN Administration Guide), so an SGTP service configuration must already exist. The SGTP
service is needed to send and/or receive GTPv1 protocol messages.
It is also a good idea to associate the IuPS service for the SGSN service to use for communication with the
RAN.
The following illustrates the minimum configuration required to associate the SGTP and IuPS services for
the RIM message transfers:
configure
context context_name
sgsn-service service_name
associate sgtp-service service_name context context_name
ran-protocol iups-service service_name
end
Configuring the peer-MME's address - Locally
Use the Call Control Profile to define the peer-MME address.
Use the tac keyword to configure the tracking area code (TAC) of the target eNodeB that maps to the peer-MME
address. For RIM message transfer, you also need to configure the Gn interface. The following is an example
of the configuration to use:
configure
call-control-profile profile_name
peer-mme tac tac_value prefer local address ip_address interface gn
end
Where:
• tac_value can be an entry from 1 to 65535.
• ip_address is the standard format address for either IPv4 or IPv6.
• gn is the interface selection used for RIM message transfer.
Configuring the peer-MME's address - for DNS Query
If using a DNS query to determine the peer-MME RIM address, then the DNS server must be pre-configured
to respond to a TAI-based DNS query in the following format:
tac-lb<TAC-low-byte>.tac-hb<TAC-high-byte>.tac.epc.mnc<MNC>.mcc<MCC>.3gppnetwork.org
Monitoring and Troubleshooting RIM Msg Transfer
The show command statistics illustrated below, can be used to monitor or troubleshoot this functionality. Note
that the selected output is only a portion of the information displayed by the command.
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show gmm-sm statistics verbose
show gmm-sm statistics verbose
show gmm-sm statistics verbose
...
Ranap Procedures:
Direct Transfer Sent:
0
Direct Transfer Rcvd:
0
show gmm-sm statistics verbose | grep RIM
show gmm-sm statistics verbose | grep RIM
...
RIM Message Statistics:
RIM Messages dropped:
due to RIM disabled in SGSN:
due to RIM Routing Address not present:
0
0
due to RNC not Capable:
0
due to RNC does not exist:
0
show sgtpc statistics verbose
show sgtpc statistics verbose
...
RAN info Relay Msg:
Total messages received:
Total messages dropped:
due to DNS failure:
due to RIM disabled in SGSN:
due to Invalid Routing Addr:
0
0
0
0
0
Total messages sent:
0
show bssgp statistics verbose
show bssgp statistics verbose
...
RIM Messages
RAN Information messages received
RAN Information messages transmitted
RAN Information Request messages received
RAN Information Request messages transmitted
RAN Information ACK messages received
RAN Information ACK messages transmitted
RAN Information Error messages received
RAN Information Error messages transmitted
RAN Information Appln Error messages received
RAN Information Appln Error messages transmitted
RIM messages dropped
due to RIM disabled in SGSN
due to destination BSC not RIM capable
due to destination cell does not exist
due to invalid destination address
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show bssgp statistics verbose
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CHAPTER
32
RTLLI Management for 2G M2M Devices
• Feature Description, page 433
• How It Works, page 433
• Configuring RTLLI Management, page 434
• Monitoring and Troubleshooting, page 435
Feature Description
Fixed Random TLLI (RTLLI) Management for 2G M2M devices is intended to expand the operator's control
of TLLI (temporary logical link identifier) in the following scenario:
When multiple M2M devices attempt PS Attaches, with the same fixed RTLLI coming from different NSEIs
(network service entity identifier), the SGSN cannot distinguish between the devices. The SGSN functions
as if the first device bearing an RTLLI is no longer attached and begins to communicate with the next device
using that same RTLLI. With multiple M2M devices attempting attaches - all with the same RTLLI - the
result is TLLI collision and dropped calls.
How It Works
This feature deals with Attach problems due to simultaneous IMSI attaches, all with the same fixed RTLLI.
Beginning with Release 16.3, it became possible to configure the SGSN to discard/drop Attach Request
messages received from an MS with an RTLLI already in use on the SGSN by adding validation of the NSEI.
Attach gets processed if the attach is coming from a different NSEI. This functionality is disabled by default.
Beginning with Release 19.3, to further reduce jumbling of authentication vectors across subscribers, the
Fixed Random TLLI Handling mechanism extends the functionality noted above. A new verification table
has been added to the GbMgr. The table maintains a list of TLLI + NSEI and if an incoming Attach Request
includes a TLLI + NSEI already on the table then the call is dropped. This functionality is disabled by default.
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Configuring RTLLI Management
Configuring RTLLI Management
No new commands or keywords have been added to the command line interface (CLI) in support of Fixed
Random TLLI Management. Enabling / disabling this mechanism is integrated into existing CLI.
For information about the commands, parameters and parameter values, please check your Command Line
Interface Reference manual for each of the commands listed below.
Important
The following configurations should be performed during system boot up. It is not advisable to
enable/disable this TLLI management functionality during runtime.
Verifying Both the RTLLI and the NSEI
To enable the SGSN to handle Attach Requests with the same fixed RTLLI by verifying both the RTLLI and
the NSEI, use the following configuration:
config
sgsn-global
gmm-message attach-with-tlli-in-use discard-message only-on-same-nsei
old-tlli invalidate tlli hex_value
old-tlli hold-time time
end
Notes:
• only-on-same-nsei - This keyword is required to enable this new verification mechanism.
Verifying Only the RTLLI
To enable the SGSN to handle Attach Requests with the same fixed RTLLI by verifying only the RTLLI, use
the following configuration:
config
sgsn-global
gmm-message attach-with-tlli-in-use discard-message
old-tlli invalidate tlli hex_value
old-tlli hold-time time
end
Notes:
• only-on-same-nsei - Do not include this keyword to disable this new verification mechanism. The
system defaults to the verification mechanism provided with Release 16.3 (see How It Works).
Verifying Configuration
To verify if the functionality is enabled or disabled, use the following commands from the Exec mode:
show configuration | grep gmm-mess
show configuration | grep oldshow configuration verbose | grep old-
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Monitoring and Troubleshooting
Monitoring and Troubleshooting
This section provides information for monitoring and/or troubleshooting the RTLLI Management functionality.
To see the statistics of attach drops that are due to same-RTLLI collisions, execute the show commands listed
below. When you are looking at the generated statistics, consider the following:
• If the generated counter values are not increasing then collisions are not occurring.
• If the generated counter values are increasing then it means collisions are occurring and attaches were
dropped.
Configured to Verify Both RTLLI and NSEI
If gmm-message attach-with-tlli-in-use discard-message only-on-same-nsei is configured then the following
show command can give the drop count of attaches caused by same RTLLI and NSEI:
[local]asr5000# show gbmgr all parser statistics all | grep use
IMSI Key: 1487 P-TMSI Key: 0 attach with tlli in use : 592 <-- drops from existing table
with RTLLI+NSEI
Add P-TMSI Key: 0 attach drop tlli in use(pre tlli check): 297 <-- drops from new table
with RTLLI
IMSI Key : 1190 P-TMSI Key : 594 attach with tlli in use : 395
Add P-TMSI Key : 0 attach drop tlli in use(pre tlli check) : 198
Configured to Verify Only RTLLI
If "gmm-message attach-with-tlli-in-use discard-message" is configured then the following show command
can give the drop count of attaches caused by same RTLLI:
[local]asr5000# show gbmgr all parser statistics all | grep use
IMSI Key: 1487 P-TMSI Key: 0 attach with tlli in use : 592 <-- drops from existing table
with RTLLI
Add P-TMSI Key: 0 attach drop tlli in use(pre tlli check): 297 <-- drops from new table
with RTLLI
IMSI Key : 1190 P-TMSI Key : 594 attach with tlli in use : 395
Add P-TMSI Key : 0 attach drop tlli in use(pre tlli check) : 198
Verify Attach Rejects due to Same RTLLI
The following show command generates SessMgr counters that track the Attach Rejects due to same RTLLI
collision:
[local]asr5000#show gmm sm stats | grep Same random tlli collision
Same random tlli collision: 10
Beginning with Release 19.3.5, the 'sgsn-implicit-detach(237)' session disconnect reason pegs when the
2G-SGSN rejects the Attach Request due to same RTLLI collision.
Beginning in Release 19.4, the following show command identifies the two bulk statistics the SGSN uses to
track the number of times the SGSN rejects Attach Requests or Combined Attach Requests due to same RTLLI
collision.
[local]asr5000# show bulkstats variables sgsn | grep colli
%2G-simple-attach-rej-randomtlli-collision%
%2G-combined-attach-rej-randomtlli-collision%
Int32
Int32
0
0
Counter
Counter
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CHAPTER
33
S4 interface Support For Non-EPC Devices
This chapter describes the S4 interface support for Non-EPC capable devices.
• Feature Description, page 437
• How it Works, page 438
• Configuring S4 Interface Support for Non-EPC Capable Devices, page 440
• Monitoring and Troubleshooting S4 Interface Support for Non-EPC Capable devices, page 441
Feature Description
The S4 interface support has been extended to Non-EPC capable devices. This support was only available for
EPC service capable devices or subscribers with EPS subscription. S4 interface support to Non-EPC devices
allows more control on interface selection and ability to handle QoS and legacy UE related behavior issues.
Overview
To enable S4 support for Non-EPC devices, interface selection options during first PDP activation have been
added, these options allow the following:
1 S4 interface selection based on UEs EPC capability alone.
2 S4 interface selection only for UEs that are EPC capable and those that have EPS subscription.
3 S4 interface selection for all UEs having EPS subscription.
4 An option to always select S4 interface.
Important
For all the options listed above (except option "2"), the HSS/HLR subscription could have both EPS and
GPRS subscription. In such cases, the S4-SGSN prefers EPS subscription, but chooses the subscription
that has the record for requested or default APN. The type of subscription chosen during the first PDP
context activation is stored as UE level information and this is used to choose the same subscription for
all subsequent primary PDP activations by the UE.
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How it Works
When the S4 interface is used and a Non-E-UTRAN capable device requests for PDP de-activation of only
the primary PDP without de-activating the associated secondary PDP's (that is, without a teardown indicator),
the SGSN deletes the associated secondary PDP contexts locally without informing UE.
When a Non-E-UTRAN capable UE activates a PDP context with Conversational or Streaming class (GBR
bearers) and if Iu is released, the UE preserves the PDP with bit rate set to "0" kbps. However, when the
S4-SGSN notices an Iu-Release, it has to de-activate the GBR bearers. Currently the S4-SGSN does not
support the de-activation of GBR bearers. When S4-SGSN support for PDP context preservation procedures
is added in a future release (for both EPC and Non-EPC devices), GBR bearers will be de-activated without
informing the UE.
How it Works
Architecture
To implement S4 interface support for Non-EPC capable devices the existing CLI command
sgsn-core-nw-interface under the Call-Control-Profile configuration has been enhanced with options for
interface selection during first PDP activation, the various options include:
1
2
3
4
Option to select the S4 interface based on UE's EPC capability alone.
Option to select the S4 interface only for UEs that are EPC capable and those that have EPS subscription.
Option to select the S4 interface for all UEs having EPS subscription
Option to select the S4 interface always.
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Architecture
Various combinations of the options listed above can be configured and the logic UE can use the S4 interface
based on the following logic:
Figure 80:
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Limitations
When the S4 interface is allowed, APN selection is performed based on the following logic:
Figure 81:
For more information on the CLI commands see, Command Line Interface Reference.
Limitations
1 QoS modification of non-GBR bearer - A Non-E-UTRAN capable UE can request QoS bit rate modification
even for Non-GBR bearers. This functionality is currently not supported. The MS initiated QoS modification
for primary PDP is rejected and QoS modification for non-GBR secondary PDP is handled by sending
BRC with zero Flow QoS. The PGW can respond with UBR (with modified APN-AMBR) or DBR and
both are handled appropriately.
2 Restricting APN-AMBR to "472" Kbps after 3G to 2G IRAT - Restricting APN-AMBR to "472" Kbps
after 3G to 2G IRAT is based on the assumption that the PGW /PCRF decide on correct QoS based on
RAT, hence additional signaling can be avoided. However, upgrading of APN-AMBR after 2G to 3G
IRAT is supported, the SGSN can initiate bearer modification based on RNC / UE capabilities and same
are honored by PGW/PCRF.
Configuring S4 Interface Support for Non-EPC Capable Devices
This section describes how to configure S4 interface support for Non-EPC capable devices.
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Configuring selection of the S4 interface
Configuring selection of the S4 interface
The command sgsn-core-nw-interface in the Call-Control-Profile configuration is enhanced with keywords
to support S4 interface selection:
config
call-control-profile cc-profile name
sgsn-core-nw-interface {gn | s4 [epc-ue {always | eps-subscribed} non- epc-ue {never | always |
eps-subscribed}]}
exit
Notes:
• When keywords or options are not selected with the selection of the S4 interface option, it implies that
the SGSN will apply S4 interface always for both EPC and Non- EPC devices. This is also synonymous
to the CLI command configured as sgsn-core-nw-interface s4 epc-ue always non-epc-ue always.
• To configure SGSN behavior supported in previous releases, the CLI is configured as
sgsn-core-nw-interface s4 epc-ue always non-epc-ue eps-subscribed. This is also the default behavior
when the CLI is not configured.
For more information on the CLI commands see, Command Line Interface Reference.
Monitoring and Troubleshooting S4 Interface Support for
Non-EPC Capable devices
This section provides information on how to monitor S4 interface support for Non-EPC capable devices and
to determine that it is working correctly.
S4 Interface Support for Non-EPC devices Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs in support of the S4 interface
support for Non-EPC devices.
show call-control-profile full name < >
This show command is updated with information about SGSN core network interface selection. The following
new fields have been added:
• SGSN Core Network Interface Selection
• SGSN Core Network Interface Type
• S4 for EPC Capable Devices
• S4 for Non-EPC Capable Devices
The field SGSN Core Network Interface Type displays interface selected as either Gn or S4.
The field S4 for EPC Capable Devices displays the configuration as either Always or When EPS Subscription
Available, based on the CLI configured in the command sgsn-core-nw-interface in the Call-Control Profile.
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S4 Interface Support for Non-EPC devices Show Command(s) and/or Outputs
The field S4 for Non-EPC Capable Devices displays the configuration as Never or Always or When EPS
Subscription Available, based on the CLI configured in the command sgsn-core-nw-interface in the
Call-Control Profile.
show subscribers sgsn-only full imsi < >
This show command is updated to display the subscription type being used for primary PDP activation. The
field Subscription Type is added to the show output. The subscription type is displayed as either EPS or
GPRS.
show subscribers gprs-only full imsi < >
This show command is updated to display the subscription type being used for primary PDP activation. The
field Subscription Type is added to the show output. The subscription type is displayed as either EPS or
GPRS.
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CHAPTER
34
S4-SGSN Suspend-Resume Feature
This chapter describes the S4-SGSN Suspend/Resume feature.
• Feature Description, page 443
• How it Works, page 444
• Configuring the S4-SGSN Suspend/Resume Feature, page 455
• Monitoring and Troubleshooting the S4-SGSN Suspend/Resume Feature, page 455
Feature Description
The S4-SGSN Suspend/Resume feature provides support for suspend/resume procedures from the BSS and
a peer S4-SGSN.
When a UE is in a 2G coverage area wants to make a circuit switched voice call but the Class A mode of
operation is not supported by the network, then the packet switched data session (PDP contexts) must be
suspended before the voice call can be made. In this case, the BSS sends a Suspend Request to the SGSN. If
the UE is already attached at that SGSN then the suspend request is handled via an intra-SGSN suspend/resume
procedure. If the UE is not attached at the SGSN then the Suspend Request is forwarded to a peer SGSN/MME
through GTPv2 and an inter-SGSN/SGSN-MME suspend procedure occurs. Once the UE completes the voice
call, either the BSS sends a resume request to resume the suspended PDPs or the UE directly sends a Routing
Area Update Request (RAU) in 2G which will be treated as an implicit resume.
The ability for a GPRS user to access circuit-switched services depends on the subscription held, the network
capabilities, and the MS capabilities.
Suspension of GPRS Services
The MS sends a request to the network for the suspension of GPRS services when the MS or the network
limitations make it unable to communicate on GPRS channels in one or more of the following scenarios:
1 A GPRS-attached MS enters dedicated mode and the support of the Class A mode of operation is not
possible (for example, the MS only supports DTM and the network only supports independent CS and
PS).
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Relationships to Other Features
2 During CS connection, the MS performs a handover from Iu mode to A/Gb mode, and the MS or the
network limitations make it unable to support CS/PS mode of operation, (for example, an MS in CS/PS
mode of operation in Iu mode during a CS connection reverts to class-B mode of operation in A/Gb mode).
3 When an MS in class A mode of operation is handed over to a cell where the support of Class A mode of
operation is not possible (for example, a DTM mobile station entering a cell that does not support DTM).
Relationships to Other Features
One of the following configurations must exist on the SGSN for the Suspend Resume feature to work properly
on the S4-SGSN:
• 2G SGSN Service + S4-SGSN Support
• 3G SGSN Service + S4-SGSN Support
• 2G SGSN Service + 3G SGSN Service + S4-SGSN Support
Configuration procedures for the above deployments are available in the ASR 5000 Serving GPRS Support
Node Administration Guide.
How it Works
S4-SGSN Suspend-Resume Feature
When a UE wants to make or receive a voice call via a GERAN circuit switched domain, and if the UE/BSS
doesn't support DTM mode, then the BSS sends a Suspend Request to the SGSN to suspend any packet data
transmission. This suspend request can be received on the same SGSN where a subscriber is already attached,
or it can be received on an SGSN where the subscriber is not yet attached.
SGSN where subscriber is attached: The SGSN initiates an intra-SGSN suspend procedure and will have
to suspend the data transmission all the way up to the PGW by sending a Suspend Request to the SGW/PGW.
When the UE completes the CS call, it will resume the packet transmission. The BSS will send a Resume
request in this case.
SGSN where subscriber is not yet attached: The SGSN initiates an inter-SGSN suspend procedure by
sending a GTPv2 / GTPv1 Suspend Request to the peer SGSN/MME. The peer node will suspend the data
transmission. When the UE completes the CS call, it may directly send a Routing Area Update request to the
2G SGSN to handover the packet switched contexts. The 2G SGSN will do a Context Request / Context
Response / Context Ack procedure with the peer node and will send a Create Session Request (if SGW
relocation occurs) or a Modify Bearer Request (if no SGW relocation occurs) to the SGW. The Modify Bearer
Request at the PGW will be treated as an implicit Resume.
Limitations
The following are the known limitations for the S4-SGSN Suspend/Resume feature:
1 If a suspend request aborts an ongoing RAU triggered SGW relocation, the Create Session Request will
be aborted and the PDN will be cleaned up. This is to avoid complexities in the state machine. If the system
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Call Flows
retained PDP, the system would have to recreate the tunnel towards the old SGW to PGW before sending
the Suspend Notification. This would delay the Suspend procedure.
2 A Suspend Request from the default SGSN in a pool to the SGSN serving the NRI of the given PTMSI
is not possible via the S16 interface due to a standards limitation. R10 specifications don't have a hop
counter and UDP source port IEs in the Suspend Notification message and hence this limitation. This is
corrected in R11 specifications. TheS4-SGSN will support this call flow only in later releases.
3 HSS initiated modification will be queued, if the Suspend preempts an HSS initiated modification while
pending for an Update Bearer Request from the PGW. The queued procedure will be restarted in a
subsequent procedure (RAU / Resume). Queued information will not be transferred to another RAT type,
if a subsequent procedure changes the RAT type.
4 A Suspend Acknowledge with rejected cause will not be sent to the peer SGSN/MME when an inter-SGSN
Suspend procedure is preempted by procedures such as RAU, Context Request, and Detach Request at
the old SGSN. Suspend Acknowledge is not sent because it is very complex on the PMM-side to distinguish
between two procedures as the PMM has the same state for both the inter-SGSN Suspend procedure and
the inter-SGSN RAU procedure.
Call Flows
This section includes various diagrams that illustrate the Suspend/Resume call flow procedures, and the
interface selection logic.
Intra-SGSN Suspend Procedure with Resume as the Subsequent Procedure
The intra-SGSN Suspend procedure with Resume as the subsequent procedure is illustrated in the following
diagram.
• When a 2G SGSN receives a Suspend Request from the BSS and if the subscriber is already attached
to the 2G SGSN, the PDPs shall be suspended. The SGSN then sends a Suspend Notification to the
SGW, which subsequently is sent to the PGW to stop all data transmissions on non-GBR bearers.
• When a 2G SGSN receives a Resume Request from the BSS, and if the subscriber that is already
suspended is attached to the 2G SGSN, the PDPs are resumed. The SGSN then sends a Resume
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Notification to the SGW, which subsequently is sent to the PGW to resume all data transmissions on
non-GBR bearers.
Figure 82: Intra-SGSN Suspend Procedure with Resume as Subsequent Procedure
Intra-SGSN Suspend with Resume Procedure with Intra-RAU as Subsequent Procedure
An Intra-SGSN Suspend procedure call flow with an Intra-SGSN RAU procedure as the subsequent procedure
is shown in the following illustration.
• If there is no SGW change for the RAU request, then the 2G-SGSN sends a Resume Notification to the
SGW and the SGW then sends a Resume Notification to the PGW to resume all data transmissions.
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Call Flows
• If there is a SGW change for the RAU request, then the 2G-SGSN sends a Create Session request to the
SGW and the SGW sends a Modify Bearer Request to the PGW to resume all data transmissions.
Figure 83: Intra-SGSN Suspend Procedure with Intra-RAU as Subsequent Procedure
Inter-SGSN Suspend and Resume Procedure with Peer S4-SGSN/MME
The procedure for a new SGSN Suspend Request and Resume procedure with a peer S4-SGSN/MME is shown
in the following diagram.
• When an S4-SGSN receives a Suspend Request from the BSS and if the subscriber is not attached to
the 2G SGSN, the S4-SGSN will send a Suspend Notification to the peer S4-SGSN/MME.
• The new SGSN RAU is the Resume procedure after a new SGSN Suspend procedure has been completed.
The SGSN sends a Create Session Request / Modify Bearer Request to the SGW which subsequently
is sent to the PGW to resume all data transmissions on non-GBR bearers.
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Call Flows
• When the Gn-SGSN receives a Suspend Request from the BSS and if the subscriber is not attached to
the 2G SGSN, it sends a Suspend Notification to the peer Gn-SGSN / S4-SGSN/MME.
Figure 84: Inter-SGSN Suspend and Resume Procedure with Peer S4-SGSN/MME
New Inter-SGSN Suspend and Resume Procedure from BSS to 2G Gn-SGSN
A new SGSN Suspend Request from the BSS to a 2G Gn-SGSN is shown in the following illustration.
• The new SGSN RAU is the Resume procedure after the new SGSN Suspend procedure has been
completed. The Gn-SGSN sends an Update PDP Context Request to the GGSN which subsequently is
sent to PGW to resume all data transmissions on non-GBR bearers.
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Call Flows
• When the S4-SGSN receives a Suspend Request from the BSS and if the subscriber is not attached to
the 2G SGSN and the peer is a Gn-SGSN, it sends a Context Request with Suspend header (GTPv1
Suspend Request) to the peer Gn-SGSN.
Figure 85: New Inter-SGSN Suspend and Resume Procedure from BSS to 2G Gn-SGSN
New SGSN Suspend and Resume Procedure with Peer Gn-SGSN as Old SGSN
The new SGSN Suspend procedure with a peer Gn-SGSN as the old SGSN is shown in the following illustration.
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Call Flows
• The new SGSN RAU is the Resume procedure after the new SGSN Suspend procedure is completed.
The SGSN sends a Create Session Request / Modify Bearer Request to the SGW which subsequently
is sent to the PGW to resume all data transmissions on non-GBR bearers.
Figure 86: New SGSN Suspend and Resume Procedure with Peer Gn-SGSN as Old SGSN
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Call Flows
Interface Selection Logic for Inter-SGSN Suspend (New SGSN) Procedure
Interface selection logic to find the peer address during the Inter SGSN Suspend (New SGSN Suspend)
procedure is explained in the flowing flow chart.
Figure 87: Interface Selection Logic for Inter-SGSN Suspend (New Suspend) Procedure
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Call Flows
Intra-SGSN Inter-System Suspend and Resume Procedure
The intra-SGSN Inter-System Suspend and Resume procedure is shown in the following illustration. In this
case, the BSS sends a Suspend Request to the 2G part of the SGSN. The 2G SGSN will internally send the
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request to the 3G S4-SGSN where the PDPs are anchored. The PDP contexts are then suspended by 3G
S4-SGSN as shown in the diagram.
The RAU is the Resume procedure after the 2G-3G Inter-System Intra-SGSN Suspend procedure is completed.
The SGSN sends a Create Session Request / Modify Bearer Request / Resume Notification to the SGW which
subsequently is sent to PGW to resume all data transmissions on non-GBR bearers.
Figure 88: Intra-SGSN Inter-System Suspend and Resume Procedure
Inter-SGSN Inter-System Suspend and Resume Procedure
The inter-SGSN inter-system Suspend and Resume procedure is shown in the following illustration. This
describes the scenario when the suspend message is received in an SGSN that is different from the SGSN
currently handling the packet data transmission and would be valid for at least the following cases:
• MS performs inter-system handover from Iu mode to A/Gb mode during CS connection and the SGSN
handling the A/Gb mode cell is different from the SGSN handling the Iu mode cell, (that is. the 2G and
3G SGSNs are separated).
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Call Flows
The RAU is the Resume procedure after the 2G-3G Inter-System Inter-SGSN Suspend procedure has completed.
The SGSN sends a Create Session Request / Modify Bearer Request to the SGW which subsequently is sent
to PGW to resume all data transmissions on non-GBR bearers.
• If there is no SGW change for the RAU request, then the 2G-SGSN sends a Modify bearer request to
the SGW. The SGW then sends a MBR all the way up to the PGW if the RAT type / Serving network
changes. Otherwise it will send the Resume Request to the PGW to resume all data transmissions.
• If there is a SGW change for the RAU request, then the 2G-SGSN sends a Create Session Request to
the SGW and the SGW sends a Modify Bearer Request to the PGW to resume all data transmissions.
Figure 89: Suspend and Resume Procedure for Inter-SGSN Inter-System Suspend and Resume
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Standards Compliance
Standards Compliance
The Suspend/Resume feature on the S4-SGSN complies with the following standards:
• 3GPP TS 23.060 version 10.11.0 Release 10 - section 16.2.1 3rd Generation Partnership Project
Technical Specification Group Services and System Aspects General Packet Radio Service (GPRS)
Service description Stage 2 (Release 10)
• 3GPP TS 29.274 version 10.7.0 Release 10 - section 7.4 3rd Generation Partnership Project Technical
Specification Group Core Network and Terminals 3GPP Evolved Packet System (EPS) Evolved General
Packet Radio Service (GPRS) Tunnelling Protocol for Control plane (GTPv2-C) Stage 3 (Release 10)
• 3GPP TS 23.272 version 10.11.0 Release 10 - section 6.7 (No PS HO Support) 3rd Generation
Partnership Project Technical Specification Group Services and System Aspects Circuit Switched (CS)
fallback in Evolved Packet System (EPS) Stage 2 (Release 10)
Configuring the S4-SGSN Suspend/Resume Feature
No configuration is required to enable the S4-SGSN Suspend/Resume Feature.
Monitoring and Troubleshooting the S4-SGSN Suspend/Resume
Feature
This section provides information on the show commands and bulk statistics available to support the
Suspend/Resume feature.
S4-SGSN Suspend and Resume Feature Show Commands
This section provides information regarding show commands available in support of the S4-SGSN
Suspend/Resume feature.
show subscriber gprs-only full all
If the state field in the output of this command reads Suspended, it indicates that a subscriber has been moved
from the Ready state to the Suspended state in 2G. Once this state change occurs, operators can use the show
bssgp statistics and show egtpc statistics commands to view information on whether the Suspend procedure
was successful or not.
Username: 123456789012345
Access Type: sgsn
Access Tech: GPRS GERAN
callid: 00004e25
Network Type: IP
msid: 262090426000193
state: Suspended
connect time: Mon Jun 17 02:27:40 2013
idle time: 00h00m14s
User Location (RAI): 26209-4369-19
IMEI(SV): n/a
call duration: 00h00m14s
Cell Global Identity: 3
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If the state field in the output of this command reads Ready, it indicates that a subscriber has moved from the
Suspended state to the Ready state in 2G. For example:
Username: 123456789012345
Access Type: sgsn
Access Tech: GPRS GERAN
callid: 00004e25
Network Type: IP
msid: 262090426000193
state: Ready
connect time: Mon Jun 17 02:27:40 2013
idle time: 00h00m14s
User Location (RAI): 26209-4369-19
IMEI(SV): n/a
call duration: 00h00m14s
Cell Global Identity: 3
show subscriber sgsn-only full all
If the state field in the output of this command reads Idle, it indicates that a subscriber has moved from the
Connected state to the Idle state in 3G. For example:
Username: 123456789012345
Access Type: sgsn
Access Tech: GPRS GERAN
callid: 00004e25
Network Type: IP
msid: 262090426000193
state: Ready
connect time: Mon Jun 17 02:24:05 2013
idle time: 00h00m12s
User Location (RAI): 26209-4660-18
Serving PLMN:
26209
IMEI(SV): n/a
call duration: 00h00m23s
Service Area Code : 1202
Equipment Status
If the state field in the output of this command reads Idle, it indicates that a subscriber has moved from the
Connected state to the Idle state in 3G. For example:
Username: 123456789012345
Access Type: sgsn
Access Tech: GPRS GERAN
callid: 00004e25
Network Type: IP
msid: 262090426000193
state: Connected
connect time: Mon Jun 17 02:24:05 2013
idle time: 00h00m12s
User Location (RAI): 26209-4660-18
Serving PLMN:
26209
IMEI(SV): n/a
call duration: 00h00m23s
Service Area Code : 1202
Equipment Status
show bssgp statistics verbose
The output of this command tracks the number of BSSGP messages (BSS Suspend procedure) transmitted
and received at the SGSN. It does not track the number messages between the BSS and the peer S4-SGSN or
peer MME. The show egtpc statistics command is used to track EGTPC messages transmitted and received
between the SGSN and a peer S4-SGSN or peer MME. Operators can check number of suspend ack messages
received to identify successful suspend procedures. The number of suspend nack messages indicate unsuccessful
suspend procedures.
Table 31: show bssgp statistics verbose Command Output
suspend messages received:
Intra-Sgsn suspend message received:
Inter-Sgsn suspend message received:
Inter-System suspend message received:
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suspend ack messages transmitted:
Intra-Sgsn suspend ack message transmitted:
Inter-Sgsn suspend ack message transmitted:
Inter-System suspend ack message transmitted:
suspend nack messages transmitted:
Intra-Sgsn suspend nack message transmitted:
Inter-Sgsn suspend nack message transmitted:
Inter-System suspend nack message transmitted:
resume messages received:
resume ack messages transmitted:
resume nack messages transmitted:
show egtpc statistics
The output of this command tracks the number of Suspend EGTPC messages transmitted and received from
or to a peer SGSN/ MME or SGW. The output also tracks the number of Resume EGTPC messages transmitted
to SGW.
Detailed descriptions of these counters are available in the ASR 5x00 Statistics and Counters Reference.
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Table 32: show egtpc statistics Command Output for S4-SGSN Suspend/Resume Feature
CS Fallback Messages:
Suspend Notification:
Initial TX: Initial RX:
Retrans TX Discarded:
No Rsp RX:
Suspend Acknowledge:
Initial TX:
Initial RX:
Discarded:
Resume Notification
Initial TX:
Initial RX:
Retrans TX:
Discarded:
No Rsp RX
Resume Acknowledge:
Initial TX:
Initial RX:
Discarded:
show egtpc statistics verbose
The output of this command tracks the number of denied Suspend notification recived and transmitted
procedures.
• Suspend Notification Denied TX means Suspend notification was denied due to any of errors listed in
the table that follows.
• Suspend Notification Denied RX means a Suspend notification was received incorrectly from the peer
S4-SGSN.
Detailed descriptions of these counters are available in the ASR 5x00 Statistics and Counters Reference.
Table 33: show egtpc statistics verbose Command Output for S4-SGSN Suspend/Resume Feature
Suspend Notification Denied
Suspend Notification Denied TX
Suspend Notification Denied RX
Context not existent:
Context not existent:
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Invalid message format:
Invalid message format:
Version not supported:
Version not supported:
Invalid length:
Invalid length:
Service not supported:
Service not supported:
Mandatory IE incorrect:
Mandatory IE incorrect:
Mandatory IE missing:
Mandatory IE missing:
System failure:
System failure:
No resources available:
No resources available:
Semantic error in TFT:
Semantic error in TFT:
Syntactic error in TFT:
Syntactic error in TFT:
Semantic error in Pkt Fltr:
Semantic error in Pkt Fltr:
Syntactic error in Pkt Fltr:
Syntactic error in Pkt Fltr:
Missing or unknown APN
Missing or unknown APN
GRE key not found:
GRE key not found:
Reallocation failure:
Reallocation failure:
Denied in RAT:
Denied in RAT:
Pref. PDN type unsupported:
Pref. PDN type unsupported:
All dynamic addr occupied:
All dynamic addr occupied:
UE ctx w/o TFT activated:
UE ctx w/o TFT activated:
Prot type not supported:
Prot type not supported:
UE not responding:
UE not responding:
UE refuses:
UE refuses:
Service denied:
Service denied:
Unable to page UE:
Unable to page UE:
No Memory:
No Memory:
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User Auth Failed:
User Auth Failed:
Apn Access Denied:
Apn Access Denied:
Request Rejected:
Request Rejected:
Semantic error in TAD:
Semantic error in TAD:
Syntactic error in TAD:
Syntactic error in TAD:
Collision with Nw init Req:
Collision with Nw init Req:
UE page unable due to Susp:
UE page unable due to Susp:
Conditional IE missing:
Conditional IE missing:
Apn Restr Type Incompatible:
Apn Restr Type Incompatible:
Invalid len Piggybacked msg:
Invalid len Piggybacked msg:
Invalid remote Peer reply:
Invalid remote Peer reply:
PTMSI signature mismatch:
PTMSI signature mismatch:
IMSI not Known:
IMSI not Known:
Peer not responding:
Peer not responding:
Data Fwding not supported:
Data Fwding not supported:
Fallback to GTPV1:
Fallback to GTPV1:
Invalid Peer:
Invalid Peer:
Temp Rej due to HO in prog:
Temp Rej due to HO in prog:
Unknown:
Unknown:
Resume Notification Denied
Resume Notification Denied TX
Resume Notification Denied RX
Context not existent:
Context not existent:
Invalid message format:
Invalid message format:
Version not supported:
Version not supported:
Invalid length:
Invalid length:
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Service not supported:
Service not supported:
Mandatory IE incorrect:
Mandatory IE incorrect:
Mandatory IE missing:
Mandatory IE missing:
System failure:
System failure:
No resources available:
No resources available:
Semantic error in TFT:
Semantic error in TFT:
Syntactic error in TFT:
Syntactic error in TFT:
Semantic error in Pkt Fltr:
Semantic error in Pkt Fltr:
Syntactic error in Pkt Fltr:
Syntactic error in Pkt Fltr:
Missing or unknown APN
Missing or unknown APN
GRE key not found:
GRE key not found:
Reallocation failure:
Reallocation failure:
Denied in RAT:
Denied in RAT:
Pref. PDN type unsupported:
Pref. PDN type unsupported:
All dynamic addr occupied:
All dynamic addr occupied:
UE ctx w/o TFT activated:
UE ctx w/o TFT activated:
Prot type not supported:
Prot type not supported:
UE not responding:
UE not responding:
UE refuses:
UE refuses:
Service denied:
Service denied:
Unable to page UE:
Unable to page UE:
No Memory:
No Memory:
User Auth Failed:
User Auth Failed:
Apn Access Denied:
Apn Access Denied:
Request Rejected:
Request Rejected:
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Semantic error in TAD:
Semantic error in TAD:
Syntactic error in TAD:
Syntactic error in TAD:
Collision with Nw init Req:
Collision with Nw init Req:
UE page unable due to Susp:
UE page unable due to Susp:
Conditional IE missing:
Conditional IE missing:
Apn Restr Type Incompatible:
Apn Restr Type Incompatible:
Invalid len Piggybacked msg:
Invalid len Piggybacked msg:
Invalid remote Peer reply:
Invalid remote Peer reply:
PTMSI signature mismatch:
PTMSI signature mismatch:
IMSI not Known:
IMSI not Known:
Peer not responding:
Peer not responding:
Data Fwding not supported:
Data Fwding not supported:
Fallback to GTPV1:
Fallback to GTPV1:
Invalid Peer:
Invalid Peer:
Temp Rej due to HO in prog:
Temp Rej due to HO in prog:
Unknown:
Unknown:
show sgtpc statistics verbose
The output of this comnand tracks the number of SGSN Context Request transmitted and received message
transmitted from the peer Gn-SGSN. It also tracks the number of SGSN Context Response messages transmitted
and received from a peer Gn-SGSN.
Table 34: show sgtpc statistics Command Output for S4-SGSN Suspend/Resume Feature
SGSN Context Request:
Total SGSN-Ctx-Req TX:
Total SGSN-Ctx-Req RX:
Initial SGSN-Ctx-Req TX:
Initial SGSN-Ctx-Req RX:
SGSN-Ctx-Req-TX(V1):
SGSN-Ctx-Req-RX(V1):
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Suspend-Req-Hdr-TX:
Suspend-Req-Hdr-RX:
SGSN-Ctx-Req-TX(V0):
SGSN-Ctx-Req-RX(V0):
Retrans SGSN-Ctx-Req TX:
Retrans SGSN-Ctx-Req RX:
Ret-SGSN-Ctx-Req-TX(V1):
Ret-SGSN-Ctx-Req-RX(V1):
Ret-Suspend-Req-Header-TX:
Ret-SGSN-Ctx-Req-TX(V0):
Ret-SGSN-Ctx-Req-RX(V0):
SGSN Context Response:
Total SGSN-Ctx-Rsp TX:
Total SGSN-Ctx-Rsp RX:
Denied TX:
Denied RX:
Suspend-Rsp-Hdr-TX:
Suspend-Rsp-Hdr-Rx:
Accepted TX:
Accepted RX:
Initial SGSN-Ctx-Rsp TX:
Initial SGSN-Ctx-Rsp RX:
SGSN-Ctx-Rsp-TX(V1):
SGSN-Ctx-Rsp-RX(V1):
Suspend-Rsp-Hdr-TX:
Suspend-Rsp-Hdr-RX:
SGSN-Ctx-Rsp-TX(V0):
SGSN-Ctx-Rsp-RX(V0):
Retrans SGSN-Ctx-Rsp TX:
Retrans SGSN-Ctx-Rsp RX:
Ret-SGSN-Ctx-Rsp-TX(V1):
Ret-SGSN-Ctx-Rsp-RX(V1):
Ret-SGSN-Ctx-Rsp-TX(V0):
Ret-SGSN-Ctx-Rsp-RX(V0):
Decode Failure RX:
S4-SGSN Suspend and Resume Feature Bulk Statistics
The following statistics are included in various bulk statistics schema in support of the Suspend/Resume
feature:
• SGSN Schema:
◦2G-attach-fail-suspend-received
◦2G-attach-fail-comb-suspend-received
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For descriptions of these variables, see the SGSN Schema Statistics section in the ASR 5x00 Statistics and
Counters Reference.
• GPRS Schema
◦bssgp-suspend-msg-rcvd
◦bssgp-suspend-ack-msg-sent
◦bssgp-suspend-nack-msg-sent
◦bssgp-resume-msg-rcvd
◦bssgp-resume-ack-msg-sent
◦bssgp-resume-nack-msg-sent
For descriptions of these variables, see GPRS Schema Statistics in the ASR 5x00 Statistics and Counters
Reference.
• EGTPC Schema:
◦csfb-sent-suspendnotf
◦csfb-sent-retranssuspendnotf
◦csfb-recv-suspendnotf
◦csfb-recv-suspendnotfDiscard
◦csfb-recv-suspendnotfNorsp
◦csfb-recv-retranssuspendnotf
◦csfb-sent-suspendack
◦csfb-sent-suspendackaccept
◦csfb-sent-suspendackdenied
◦csfb-recv-suspendack
◦csfb-recv-suspendackDiscard
◦csfb-recv-suspendackaccept
◦csfb-recv-suspenddenied
◦csfb-sent-resumenotf
◦csfb-sent-retransresumenotf
◦csfb-sent-resumeack
◦csfb-sent-resumeackaccept
◦csfb-sent-resumeackdenied
◦csfb-recv-resumeack
◦csfb-recv-resumeackDiscard
◦csfb-recv-resumeackaccept
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◦csfb-recv-resumedenied
For descriptions of these variables, see EGTPC Schema Statistics in the ASR 5x00 Statistics and Counters
Reference.
• SGTP Schema:
◦sgtpc-sgsn-ctxt-req-v1-tx
◦sgtpc-sgsn-ctxt-req-v1-rx
◦sgtpc-sgsn-ctxt-req-accept-tx
◦sgtpc-sgsn-ctxt-req-accept-rx
◦sgtpc-sgsn-ctxt-req-accept-v1-tx
◦sgtpc-sgsn-ctxt-req-accept-v1-rx
◦sgtpc-sgsn-ctxt-req-denied-tx
◦sgtpc-sgsn-ctxt-req-denied-rx
◦sgtpc-sgsn-ctxt-ack-accept-tx
◦sgtpc-sgsn-ctxt-ack-accept-rx
◦sgtpc-sgsn-ctxt-ack-accept-v1-tx
◦sgtpc-sgsn-ctxt-ack-accept-v1_rx
◦sgtpc-sgsn-ctxt-ack-denied-tx
For descriptions of these variables, see SGTP Schema Statistics in the ASR 5x00 Statistics and Counters
Reference.
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35
SGSN-MME Combo Optimization
This section describes Combo Optimization available for a co-located SGSN-MME node. It also provides
detailed information on the following:
• Feature Description, page 467
• How It Works, page 468
• Configuring the Combo Optimization, page 471
• Monitoring and Troubleshooting Combo Optimization , page 472
Feature Description
The SGSN and MME can be enabled simultaneously in the same chassis and, though co-located, they each
behave as independent nodes. This Combo Optimization feature enables the co-located SGSN and MME to
co-operate with each other in order to achieve lower memory and CPU utilizations and to reduce signaling
towards other nodes in the network. When functioning as mutually-aware co-located nodes, the SGSN and
the MME can share UE subscription data between them.
Important
This feature is supported by both the S4-SGSN and the Gn-SGSN. For the feature to apply to a Gn-SGSN,
the Gn-SGSN must be configured to connect to an HSS. Combo Optimization for an SGSN-MME node
is a licensed Cisco feature. Contact your Cisco account representative for detailed information on specific
licensing requirements. For information on installing and verifying licenses, refer to the Managing License
Keys section of the Software Management Operations chapter in the System Administration Guide.
Overview
The load on S6d/S6a interfaces towards an HSS is reduced effectively by utilizing the resources in a co-located
SGSN-MME node scenario. Requests for subscription data in Update Location Request (ULR) are skipped
by setting the 'skip-subscriber-data' bit in the ULR flags this, in turn, reduces the load on the HSS. The Skip
Subscriber Data AVP is used and the subscriber data is shared across the SGSN and the MME services.
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How It Works
As per 3GPP TS 29.272, setting the 'skip-subscriber-data' bit in the ULR indicates that the HSS may skip
sending subscription data in Update Location Answer (ULA) to reduce signaling. If the subscription data has
changed in the HSS after the last successful update of the MME/SGSN, the HSS ignores this bit and sends
the updated subscription data. If the HSS skips sending the subscription data, then the
GPRS-Subscription-Data-Indicator flag can be ignored.
Important
The SGSN supported the Skip-Subscription-Data bit prior to Release 18.0. Support for this functionality
was added to the MME in Release 18.0.
Ensuring that packets are routed internally reduces network latency for S3/Gn interface messages. This is
achieved by configuring the SGTP and EGTP services in the same context for the SGSN and the MME
configurations.
For outbound Inter-RAT SRNS Relocations, the MME gives preference to the co-located SGSN, irrespective
of the order/priority or preference/weight configured for the SGSN entry in DNS Server. When Inter-RAT
handovers take place between the co-located MME and the SGSN, the new call arrives at the same Session
Manager that hosted the call in the previous RAT. If the subscription data is available for a given UE at the
co-located SGSN, then the MME does not need to request this data from the HSS and provides UE subscription
data obtained from the SGSN. This optional function can be turned on or off through the MME Service
configuration.
Combo Optimization is available for subscribers with an EPC-enabled UE and an EPC subscription configured
at the HSS. During handoff from 4G to 3G or 4G to 2G, the EPC subscription will be copied from the MME.
Combo Optimization is also applicable for Non-EPC subscribers if core-network-interface is selected as S4
for the EPS-subscription.
How It Works
Subscriber Movement from MME to SGSN: Subscription information is first fetched by the MME. On
subscriber movement to a co-located SGSN, the SGSN sends a ULR with "skip-subscriber-data" flag set and
the HSS sends a ULA (with or without subscription data depending on time of MME update).
Subscriber Movement from SGSN to MME: Subscription information is first fetched by the SGSN. On
subscriber movement to a co-located MME, the MME sends a ULR with "skip-subscriber-data" flag set and
the HSS sends a ULA (with or without subscription data depending on time of SGSN update).
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Architecture
Architecture
Figure 90: SGSN-MME Combo Node
The above diagram displays the interworking of various modules when the Combo Optimization feature is
enabled in a co-located SGSN-MME setup.
When the subscriber does RAU from MME to SGSN, or vice versa, a DNS query is initiated to fetch the
address of the peer node. Based on the IP address obtained, the peer MME or SGSN is selected. When a DNS
response is received with a list of peer SGSN addresses, the MME matches the configured EGTP/SGTP SGSN
service address in the system and uses it for the S3/Gn UE Context Transfer procedures. If a DNS response
is not received and a locally configured EGTP/SGTP SGSN service is present as a peer-SGSN, the peer-SGSN
will be selected. Context transfer and copying of subscription information happens internally between the
SGSN and the MME nodes. The SGSN maintains the s6d interface towards the HSS and the MME maintains
the S6a interface towards the HSS. All network-initiated messages are sent separately towards the SGSN and
the MME nodes respectively.
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Flows
Flows
This section includes various diagrams that illustrate the session manager (SessMgr) selection logic during
RAU, SRNS, and Attach procedures:
Figure 91: Selection of SessMgr Instance during RAU from MME to SGSN
Listed below is the SessMgr instance selection logic during a RAU procedure from the MME to SGSN:
1 A RAU request from UE is forwarded to the LinkMgr or GbMgr.
2 The LinkMgr identifies if the RAU is local and extracts the SessMgr instance from the PTMSI and forwards
the request to IMSIMgr.
3 The IMSIMgr tries to select the SessMgr instance extracted from the PTMSI and forwards the request to
the selected SessMgr.
Figure 92: Selection of SessMgr Instance during SRNS
Listed below is the SessMgr instance selection logic during an SRNS procedure:
1 During an SRNS procedure, the MME service sends a Forward Relocation Request to the EGTPCMgr.
2 The EGTPCMgr forwards the request to the IMSIMgr.
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Limitations
3 The IMSIMgr uses the IMSI received in the request message to identify the SessMgr instance and forwards
the request to the appropriate SessMgr instance.
Figure 93: Selection of SessMgr Instance during Attach
Listed below is the SessMgr instance selection logic during an Attach procedure:
1 During Attach procedure, the LinkMgr/GbMgr forwards the request to the IMSIMgr.
2 The IMSIMgr first verifies if the IMSI is present in the SGSN's IMSI table. If it is not present, the MME's
IMSI table is verified. Once the entry is found the request is forwarded to the appropriate SessMgr.
3 If the entry is not found in either table, then an alternate SessMgr instance is used to process the call.
Limitations
Subscription information is shared between MME and SGSN only when both are connected to an HSS. Combo
Optimization is not be applicable if either the MME or the SGSN is connected to an HLR. Though the
subscription information is shared between the SGSN and MME services, a separate HSS service and diameter
endpoint will be maintained for both the SGSN and the MME. All network-initiated messages are received
separately for both the MME and the SGSN. Subscription data is copied based on time-stamp validation.
A small impact on the performance is observed during Inter-RAT handoffs as subscription data is exchanged
between the SGSN and the MME. This impact is a limited increase in the number of instructions per handoff
per UE depending on the number of APNs configured for the UE in the HSS.
It is necessary that the HSS honors the request from the MME/SGSN and not send subscription data when
'Skip-Subscriber-Data' flag is set in the ULR. However, there are some known and valid cases where the HSS
ignores this flag for example, if the UE's subscription data changed since the last time the UE attached in 4G.
(Typically, UE subscription data does not change frequently, therefore, HSS overrides are less frequent.)
Configuring the Combo Optimization
This section describes how to configure the Combo Optimization for an SGSN-MME combo node.
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Verifying Combo Optimization Configuration
By default, Combo Optimization is not enabled. This command both enables or disables Combo Optimization
on an SGSN-MME combo node.
config
lte-policy
[ no ] sgsn-mme subscriber-data-optimization
end
Note:
• no as a command prefix disables Combo Optimization.
The following CLI (applicable only to the SGSN in the combo node), under the call-control profile configuration
mode, controls requests for GPRS subscription information from the HSS:
config
call-control-profile profile_name
hss message update-location-request gprs-subscription-indicator [ never | non- epc-ue ]
end
Verifying Combo Optimization Configuration
Execute the following command to verify the configuration of this feature.
show lte-policy sgsn-mme summary
The following field value indicates if data optimization on the SGSN-MME combo node is "Enabled" or
"Disabled":
• subscriber-data-optimization
Monitoring and Troubleshooting Combo Optimization
This section provides information on the show commands and bulk statistics available to monitor and
troubleshoot Combo Optimization for the SGSN-MME combo node, and for each element separately.
Monitoring Commands for the SGSN-MME Combo Node
This section provides information regarding show commands and/or their outputs in support of the Combo
Optimization feature on the SGSN-MME Combo Node:
show hss-peer-service statistics all
The following new fields are added to the show output to display the subscription data statistics:
• Subscription-Data Stats
• Skip Subscription Data
• Subscription-Data Not Received
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Monitoring Commands for the SGSN
The Skip Subscription Data statistic is incremented when the ULR is sent with the skip-subscription-data flag
set. The Subscription-Data Not Received statistic is incremented if the HSS does not send the subscription
data in the ULA when skip-subscription-data flag is set in ULR. The difference between the Skip Subscription
Data and Subscription-Data Not Received gives us the number of times HSS does not honor the
skip-subscription-data flag.
Monitoring Commands for the SGSN
This section provides information regarding show commands and/or their outputs in support of the Combo
Optimization feature on the SGSN:
show demux-mgr statistics imsimgr all sgsn
The following new fields are added in the show output to display the number of RAU, Attach, PTIMSI attach
and Forward relocation requests arriving from a subscriber attached with co-located MME:
• IMSI attach with context in co-located MME
• P-TMSI attach with mapped P-TMSI of co-located MME
• RAU with mapped P-TMSI of co-located MME
• Fwd reloc request from co-located MME
show subscribers sgsn-only summary
The following new field is added in the show output to display the number of subscribers currently sharing
subscription information with the MME:
• Total HSS subscribers sharing subscription-info
show subscribers gprs-only summary
The following new field is added in the show output to display the number of subscribers currently sharing
subscription information with MME:
• Total HSS subscribers sharing subscription-info
show subscribers sgsn-only full all
The STN-SR , ICS-indicator , Trace-Data and CSG subscription information is now displayed under the show
subscribers sgsn-only full all output. These AVPs are currently used by MME only .Values are displayed
as received from HSS without any format changes.
• Trace Data
• Trace Reference
• Trace Depth
• Trace NE Type List
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Monitoring Commands for the SGSN
• Trace Interface List
• Trace Event List
• OMC Id
• Trace Collection Entity
• STN-SR
• ICS-Indicator
• CSG Subscription
• CSG ID
• Expiration Date
show subscribers gprs-only full all
The STN-SR, ICS-indicator, Trace-Data and CSG subscription information is now displayed under the show
subscribers gprs-only full all output. These AVPs are currently used only by the MME. Values are displayed
as received from HSS without any format changes.
• Trace Data
• Trace Reference
• Trace Depth
• Trace NE Type List
• Trace Interface List
• Trace Event List
• OMC Id
• Trace Collection Entity
• STN-SR
• ICS-Indicator
• CSG Subscription
• CSG ID
• Expiration Date
show session subsystem facility aaamgr instance
The following new fields are added in the show output to display the total number of CSG subscription records
and Trace data records:
• SGSN: Total Trace data records
• SGSN: Total CSG data records
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Monitoring Commands for the MME
Monitoring Commands for the MME
This section provides information regarding show commands and/or their outputs in support of the Combo
Optimization feature on the MME:
show mme-service statistics handover
The following new statistics are added to the show output to display the information about Inter-RAT Optimized
Handoffs between the co-located SGSN and MME:
• Inter-RAT Optimized Handoffs Between Co-located MME and SGSN
• Outbound MME to SGSN RAU procedure
• Attempted
• Success
• Failures
• Inbound SGSN to MME TAU procedure
• Attempted
• Success
• Failures
• Outbound MME to SGSN Connected Mode Handover
• Attempted
• Success
• Failures
• Inbound SGSN to MME Connected Mode Handover
• Attempted
• Success
• Failures
Bulk Statistics for Monitoring the MME in an SGSN-MME Combo Node
The following bulk statistics in the MME schema facilitate tracking MME optimization functionality for the
SGSN-MME nodes when co-located in the same chassis with the Combo Optimization functionality enabled:
• optimized-out-rau-ho-4gto2g3g-attempted
• optimized-out-rau-ho-4gto2g3g-success
• optimized-out-rau-ho-4gto2g3g-failures
• optimized-in-tau-ho-2g3gto4g-attempted
• optimized-in-tau-ho-2g3gto4g-success
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Bulk Statistics for Monitoring the MME in an SGSN-MME Combo Node
• optimized-in-tau-ho-2g3gto4g-failures
• optimized-out-s1-ho-4gto2g3g-attempted
• optimized-out-s1-ho-4gto2g3g-success
• optimized-out-s1-ho-4gto2g3g-failures
• optimized-in-s1-ho-2g3gto4g-attempted
• optimized-in-s1-ho-2g3gto4g-success
• optimized-in-s1-ho-2g3gto4g-failures
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36
SGSN Pooling
This chapter describes the SGSN Pooling feature.
• Feature Description, page 477
• How it Works, page 479
• Configuring the SGSN Pooling feature, page 486
• Monitoring and Troubleshooting the SGSN Pooling feature, page 488
Feature Description
An SGSN pool is a collection of SGSNs configured to serve a common geographical area for a radio network.
This common part is referred to as the SGSN pool service. SGSN Pooling is also referred to as Iu/Gb flex
support based on if the access is 3G or GPRS respectively.
An SGSN pool provides a flexible and resource-efficient architecture with built-in network redundancy for
the GPRS/UMTS packet core network. Each BSC/RNC has the ability to connect to all SGSNs in the pool.
If any SGSN becomes unavailable, any terminal attached to that SGSN will be automatically re-routed to
another SGSN in the pool by the BSC/RNC. This implies that the SGSN pool provides network level
redundancy. SGSN failure is discovered by the BSCs/RNCs and the uplink traffic from the terminal is routed
to another SGSN in the pool. The substituting SGSN orders the terminal to re-attach and re-activate any PDP
contexts. Therefore service availability is maintained. Please note that all SGSNs in a pool are required to
have the same capacity, feature sets and scalability and hence the same vendor, failing which might lead to
varying subscriber experience across SGSNs.
In a pooled network, Inter-SGSN routing area updates (RAUs) are avoided and this provides a faster response
time, compared to non-pooled networks. With SGSN pool for GPRS/UMTS, Inter-SGSN RAU is replaced
by Intra-SGSN RAU, for terminals moving within the pool area. Intra-SGSN RAU provides reduced interruption
time for data transfer, compared to Inter-SGSN RAU. Furthermore, due to the fewer Inter-SGSN RAUs, there
is less signaling generated on the Gr interface.
When an UE connects to an SGSN in the pool, by Attach or Inter-SGSN RAU (ISRAU) procedures, the UE
is allocated a Packet Temporary Mobile Subscriber Identity (P-TMSI) containing a Network Resource Identifier
(NRI) identifying the SGSN. The BSC/RNC then identifies the SGSN from the NRI, and routes the user data
to the correct SGSN. Load-sharing between the SGSN pool members is thus based on the NRI routing algorithm
in the BSC/RNC. UEs that have not yet been assigned a P-TMSI, and MSs without matching NRI, are
distributed among the pool members by the BSC/RNC according to the traffic distribution procedure. Once
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A Basic Pool Structure
a UE has been allocated a P-TMSI, it stays connected to the same SGSN as long as it remains in the pool area.
This period can be quite long, since MSs normally keep the P-TMSI even after power off.
A valid license key is required to enable the SGSN Pooling feature. Contact your Cisco Account or Support
representative for information on how to obtain a license.
A Basic Pool Structure
A basic SGSN pool structure is depicted in the diagram below:
Figure 94: A basic pool structure
• Multiple SGSNs form a single logical entity called SGSN pool.
• SGSN pools service areas larger than stand-alone SGSN service areas.
• This set up is compatible with non-pool aware nodes and is transparent to the end-user.
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Benefits of SGSN Pooling
Benefits of SGSN Pooling
1 Increased Availability: If one SGSN fails, another SGSN from the pool can substitute it. Any node can
be taken out of a pool during maintenance.
2 Increased Scalability: More number of SGSN nodes can be added to the pool.
3 Reduced Signaling: Number of inter-SGSN routing area updates is reduced.
Pooling Requirements
Listed below are the requirements to support pooling:
1 The SGSN should support configuration of NRI and use that NRI in all the PTMSI issued.
2 If the SGSN is configured as a default SGSN, it should relay SGSN Context Request / Identification
request received from peer SGSN (outside of pool) to SGSN (in pool) anchoring that subscriber anchoring
SGSN in pool.
3 Support of non-broadcast RAI, null-NRI configurations to allow off-loading of self-SGSN and handle the
off-loading of a peer SGSN.
How it Works
P-TMSI - NRI and Coding
Every SGSN is configured with one or several NRIs (O&M). One of these NRIs is part of every Packet
temporary Mobile Subscriber identity (P-TMSI) which the SGSN assigns to an UE for connecting via pooled
BSC/RNC. For non-pooled BSC/RNC SGSN sets all NRI bits to "0". The P-TMSI allocation mechanism in
the SGSN generates P-TMSIs which contain one of the configured NRIs in the relevant bit positions. A NRI
has a flexible length up to "6" bits). The maximum number of SGSNs in a pool is limited to "63" (One NRI
value reserved for NULL-NRI).
P TMSI is of length "32" bits, where the two top most bits are reserved and always set to "11". The NRI field
is included at the beginning of P TMSI starting at bit "23" and down up to bit "18". The most significant bit
of the NRI is located at bit "23" of the P TMSI regardless of the configured length of the NRI
Once a subscriber attaches to a new SGSN, a new P-TMSI is allocated by the P-TMSI re-allocation procedure.
That P-TMSI contains the NRI of the SGSN. This is also the case when an Inter-SGSN RA update or an
Inter-System Change (IRAT) occurs.
Non-Broadcast LAC and RAC
The LAC and RAC information is made available by off-loading the SGSN to the UE in the
GMM_ATTCH_ACCEPT/GMM_RAU_ACCEPT message along with the NULL-NRI in the P-TMSI. This
value is different from the LAC and RAC that an UE receives from BSS/UTRAN as broadcast information.
These parameters are set unique per SGSN node.
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SGSN Address Resolution
SGSN Address Resolution
The following kinds of SGSN address resolution can be identified:
1 Address resolution with NRI.
2 Address resolution without NRI.
Address Resolution with NRI
A NRI based look-up occurs in the following scenarios:
1 An Inter-SGSN RAU occurs within a pooled area. This could be due to one of the SGSNs offloading the
subscribers or due to a Gb/ Iu link failure on one of the SGSNs.
2 An Inter-SGSN RAU occurs from a pooled to a non-pooled SGSN. The
GTP_SGSN_CONTEXT_REQUEST is routed to the default SGSN in the pool. The default SGSN looks
up for the Gn address of the member in the pool based on the NRI retrieved from the P-TMSI in the
GTP_SGSN_CONTEXT_REQUEST message received. A local configuration of these entries has to be
present in the SGSN Operator Policy.
3 When offloading is enabled, the nb-rai and null-nri of the SGSN which is being offloaded should be
configured in the cc-profiles of other SGSN\'s in the pool. Unless a entry is present, a periodic RAU will
not be accepted in the other SGSN\'s carrying that nb-rai and null-nri.A local configuration of these entries
has to be present in the SGSN Operator Policy.
Address resolution without NRI
Address resolution without NRI is used for Inter-SGSN RAU between non-pooled areas or between multiple
pools. In this case the SGSN context request is routes towards the default SGSN, which in turn relays the
GTP message to the right SGSN based on the NRI value in the P-TMSI.
Refer to the configuration section for the procedure to "Configure an Operator Policy".
Mobility Inside the Pool
The distribution of UEs in a pool is handled by the BSCs/RNCs.
1 The UE sends an Attach Request or a RA Update Request to a SGSN.
2 This request passes through the BSC/RNC.
3 The BSC/RNC uses the NRI to locate the SGSN.
4 Once the SGSN is located Gb/Iu connection is set up.
If the NRI from the UE is invalid or does not match any of the NRIs of the pool members, the request is
directed to one of the pool members by the BSC/RNC. International Mobile Subscriber Identity (IMSI) attaches
are also distributed among the SGSN pool members by the BSCs.
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Mobility Outside the Pool
Once a P-TMSI containing the NRI of a pool member has been assigned to an UE, the UE stays attached to
that pool member as long as it remains in that pool service area. The frequency of inter-SGSN RA updates
decreases, as the UE can move over a greater geographical area for one SGSN.
Figure 95: Mobility inside the pool
Consider the scenario depicted in the diagram above:
1 A subscriber attached to SGSN-1 through RNC-1 moves under the coverage area of RNC-2, while being
attached to SGSN-1. This results only in an Intra-SGSN RAU.
2 A subscriber attached to SGSN-1 through BSC-1 moves under the coverage area of BSC-2, while being
attached to SGSN-1. This results only in an Intra-SGSN RAU.
Important
Inter-SGSN RAU within the pool is not very common unless one of the SGSNs within the pool is offloading
the subscribers or the Gb/Iu link towards one of the SGSNs from a BSC/RNC is unavailable.
Mobility Outside the Pool
When an UE leaves a pool service area and performs an Attach or a RA update to an SGSN outside the pool
service area, the new SGSN cannot identify the old SGSN based on the old Routing Area Identity (RAI).
Finding the address of the old SGSN is facilitated by a DNS query with RAI specified. First the new SGSN
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uses the RAI to identify the default SGSN in the pool. The new SGSN then fetches the subscriber data from
the old SGSN and continues with the routing area update procedure.
Figure 96: Mobility outside the Pool
Consider the scenario depicted in the diagram above:
The subscriber movement can be traced through the numbers 1, 2, 3 and 4 in the diagram.
1 The SGSN-X is not pooled. The SGSN-X queries the DNS to identify the source SGSN from where the
UE arrived to initiate a GTP_SGSN_CONTEXT_REQUEST.
2 The DNS responds back with the IP address of the default SGSN in the pool, which could be either SGSN-1
or SGSN-2 or both.
3 The address resolution is performed based on the LAC and RAC similar to other Inter-SGSN RAU.
4 The designated default SGSN relays the GTP message to the source SGSN in the pool, which is located
using the NRI in the P-TMSI and hence the DNS query with NRI, LAC and RAC.
5 In the implementation above both SGSN-1 and SGSN-2 are designated as default SGSNs to load share
the GTP signaling traffic.
6 For every LAC/RAC in the pooled areas the DNS resolves the query into two IP addresses pertaining to
the Gn loopback addresses of SGSN-1 and SGSN-2 respectively.
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MS Offloading
MS Offloading
MS offloading is a procedure of offloading the subscribers from one SGSN in the pool to another SGSN
within the same pool. Offloading is performed during the following scenarios:
1 The operator wants to carry out a scheduled maintenance.
2 The operator wants to perform a load re-distribution.
3 To avoid an overload.
Offloading has to be performed with minimum impact on the end users.
Types of MS Offloading:
1 Null-NRI based.
2 Target-NRI based.
3 IMSI based offloading
Null-NRI based Offloading
Null-NRI based offloading is carried out in the following three phases:
Phase - 1
1 UEs performing a RAU or Attach are moved to other SGSN in the pool.
2 When the SGSN receives the Routing Area Update or Attach request, it returns a new P-TMSI with the
null-NRI, and non-broadcast LAC and RAC in the accept message.
3 A new Routing Area Update is triggered by setting the periodic routing area update timer to a sufficiently
low value in the accept message.
4 The UE sends a new Routing Area Update, the BSC then routes this RAU to a new SGSN due to the
presence of a null-NRI. The BSC uses a round robin mechanism to allocate an SGSN for this UE.
Phase - 2
1 All PDP context activation requests are rejected and the UEs are requested to detach and re-attach (Detach
request sent from the network with cause code "reattach required").
2 When the UEs re-attach, the SGSN moves them as described above in "Phase 1", that is, by sending the
null-NRI and non-broadcast LAC and RAC and triggering a periodic RAU update.
Phase -3
This phase includes scanning through the remaining UEs and initiating a detach procedure for them. The UEs
are requested to detach and re-attach, this results in the UEs moving as described in "Phase 1".
UEs being moved from one SGSN can be stopped from registering to the same SGSN again by issuing a CLI
command in BSCs connected to the pool. UEs moving into a pool area may also be stopped from registering
into a SGSN being off-loaded in the same manner. The move operation will not overload the network, as
throttling is supported for both Attach and Inter SGSN RAU procedures.
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Target-NRI based offloading
Target NRI based offloading was primarily introduced so that subscribers can be offloaded to a chosen SGSN.
In the case of NULL-NRI based offloading there is no control on which SGSN the subscribers are offloaded
to. SGSN offloads subscribers by assigning NB-RAI, stamping Target-NRI in PTMSI and reducing periodic
routing area update timer during Attach/RAU accept messages.
IMSI-based offloading is carried in the following three phases:
IMSI based offloading
With Target-NRI based method of offloading though there is control on the SGSN to which the subscribers
are offloaded, there is no control on the subscribers being offloaded to the SGSN. IMSI-based offloading
enhancement allows the operator to choose the subscribers to be offloaded to a particular SGSN.
Phase -1
When a Attach accept or a RAU accept is issued, the offloading configuration is verified and if offloading is
enabled, the corresponding NRI is issued (if it is not issued earlier). In case the specific IMSI based offloading
configuration is configured, the configured target-nri is used. When offloading is enabled, if ptmsi allocation
configuration is absent, a ptmsi is allocated to the subscriber in Attach/RAU accept.
Phase -2
On receiving an activation trigger from the MS, the subscriber is detached and the re-attach required is set to
true. The MS will return an attach in due time, after which the MS is offloaded to another SGSN by setting
the Target-NRI and NB-RAI appropriately.
Phase -3 0
The subscriber is cleared unconditionally and a detach is sent by setting the re-attach required to true. The
subscriber is lost at this stage. In the next attach, the subscriber is offloaded to the configured SGSN.
For information on the procedure to configure MS-Offloading, refer to the section "Configuration of SGSN
Pooling - Procedure to configure MS-Offloading".
Iu/Gb Flex support over S16/S3 interface
SGSN Pooling support has been extended to S16/S3 interface. The enhancement also includes support for
default SGSN functionality for S16/S3 interface as in the case of Gn interface. The peer SGSN in this case is
a S4-SGSN. The incoming message (EGTP_CONTEXT_REQ/IDENTIFICATION_REQ) is received from
a non-pooled SGSN, it is forwarded to the old-SGSN if the SGSN is configured as default SGSN. The SGSN
in a pool is identified on the basis on NRI value and OLD- RAI value. The NRI value is extracted from PTMSI.
Backward compatibility and default SGSN functionality
If a default SGSN that is serving a pool-area receives EGTP signaling it resolves the ambiguity of the multiple
SGSNs per RAI by deriving the NRI from the P-TMSI. The SGSN relays the EGTP signaling to the old SGSN
identified by the NRI in the old P-TMSI unless the default SGSN itself is the old SGSN. For default-SGSN
functionality to work, static IP address entries are mandatory in the call-control profile.
Messages are relayed by the Default-SGSN (Default SGSN functionality and pooling are enabled) in following
cases:
• Pooled local RAI and non-local NRI
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• Non-local RAI and Null-NRI
• Non-local RAI and Target-NRI
For "Non-local RAI and Null-NRI" and "Non-local RAI and Target-NRI" options, the NB-RAI of other SGSN
is considered. It is non-local to the SGSN. No other configuration entries are present at the SGSN other than
cc-profile entries.
Mobility Management
The MS performs RA Updates and Attachments, which result in a change of the serving SGSN. In these
procedures the new SGSN requests MS specific parameters from the old SGSN. The default SGSN node uses
the old RA together with the NRI to derive the signaling address of the old SGSN from its configuration data.
Address and TEID for the Control Plane
• The relaying SGSN forwards the Context Request message to the interface of the old SGSN. The
incoming request can arrive over a S3 interface in case of MME or S3 in case of S4-SGSN. However
the old RAI interface will be always S16.
• When the default-sgsn relays the message, if the UDP port number is absent in the request received, the
default-sgsn adds the "UDP source port number" IE while relaying. This is applicable for both Context
Request and Identification Request relay functionality.
• If in an Identification request message, "Address for control plane" is an optional IE. A SGSN within
the same SGSN pool with the old SGSN receives the Identification request message it includes the old
IP address of the received message in this optional parameter if this IE is not present and relays the
message to the old SGSN.
• In cases where default-sgsn has to send a negative response, it sends the message to the IP as indicated
in the "S3/S16 Address and TEID for Control Plane" IE and destination port set as indicated by "UDP
source port number" IE.
• If an SGSN within the same SGSN pool with the old SGSN receives this message, the SGSN decrements
the Hop Counter if this IE is present in the received message. Otherwise, the SGSN includes a Hop
Counter with a configured value and relays the message to the old SGSN. This is applicable for both
Context Request and Identification Request relay functionality.
For more information refer to 3GPP TS 29.274 (Table 7.3.5-1: Information Elements in a Context Request,
Table 7.3.8-1: Information Elements in an Identification Request).
For information on procedure to configure Iu/Gb flex on S16/S3 interface refer to the section "Configuration
of SGSN Pooling - Procedure to configure default SGSN (S16/S3 interface)".
Standards Compliance
The SGSN Pooling feature complies with the following standards:
• 3GPP TS 23.236
• 3GPP TS 29.274
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Configuring the SGSN Pooling feature
Configuring the SGSN Pooling feature
2G-SGSN pool configuration
Listed below are the pre-requisite CLI configurations that should be enabled to configure a 2G SGSN Pool:
1 2G SGSN Pooling configuration is done under the GPRS service in the Gb context.
2 The NRI value, NRI length, Null-NRI value and non-broadcast LAC/RAC are configured for the GPRS
service.
3 The GPRS service is capable of handling both pooled and non-pooled BSCs.
GPRS Service Configuration:
config
context context_name
gprs-service service_name
peer-nsei nse_id pooled
nri length nri_length { nri-value nri_value | null-nri-value null_nri_value non broadcast-lac lac_id
rac rac_id [ nri-value value ]}
exit
Notes:
• The above configuration must be repeated each time a BSC is added.
• The command peer-nsei is used to render a BSC as pooled or non-pooled.
3G-SGSN pool configuration
Listed below are the pre-requisite CLI configurations that should be enabled to configure a 3G SGSN pool:
1 3G SGSN pooling configuration is done under the IuPS service in the Iu context.
2 The NRI value, NRI length, Null-NRI value and non-broadcast LAC/RAC are configured for the SGSN
service.
3 The IuPS service is capable of handling both pooled and non-pooled RNCs.
IuPS Service Configuration
config
context <context_name>
iups-service <service_name>
rnc id <rnc_id> pooled
exit
SGSN Service Configuration
config
context <context_name>
sgsn-service <service_name>
nri length nri_length [ nri-value nri_value | null-nri-value null_nri_value non-broadcast mcc mcc
mnc mnc lac lac_id rac rac_id nri-value value ]
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default nri
no nri
exit
To Configure a Default SGSN
This procedure is common to both 2G and 3G SGSN pooling configurations. The SGSN can be configured
as a "default SGSN" in the pool under the SGTP service in the Gn context. This configuration is to be performed
only once to render a SGSN as a "default SGSN".
config
context <context_name>
sgtp-service <service_name>
pool {default-sgsn | hop-counter count}
exit
Procedure to Configure a Default SGSN (S16/S3 interface)
The following CLI command under the eGTP Service Configuration mode is used to configure the default
SGSN:
config
context <context_name>
egtp-service <service_name>
pool {default-sgsn | hop-counter count}
exit
The default SGSN receives inbound SGSN context request messages and forwards it to the correct SGSN in
the pool based on the NRI bits of the P-TMSI. If the incoming message EGTP_CONTEXT_REQ/
IDENTIFICATION_REQ has the hop count IE, the default SGSN decrements the count by one and forwards
it to the Old-SGSN. The hop count is not over written even if it is configured. If the hop count IE is missing
with incoming message then the then hop count configured gets populated. If no value is configured the default
value is chosen. The hop Counter prevents endless relaying of context/identification request. Each relaying
SGSN keeps decrementing the hop-counter value if received from the peer-sgsn, otherwise the SGSN includes
hop-counter IE. If default-sgsn receives request having hop counter "0", it does not relay the request.
Procedure to Configure an Operator Policy
Step 1:
config
operator-policy (default | name policy_name) [-noconfirm]
Step 2:
config
call-control profile profile_name
sgsn-address { nri nri | rac rac-id lac lac_id | rnc_id rnc_id } [ nri nri ] prefer { fallback-for-dns | local
} address { ipv4 ip_address | ipv6 ip_address } interface { gn | s16 }
Procedure to Configure MS Offloading
The SGSN offload command is used to configure the MS offloading procedure.
The following CLI command (for phase 1 and phase 2 of offloading) is issued for each GPRS/SGSN service:
sgsn offload { gprs-service service_name | sgsn-service service_name } { activating [ imsi imsi | nri-value
nri_value | stop [ imsi imsi | nri-value nri_value ] ] | connecting [ nri-value nri_value | stop [ imsi imsi |
nri-value nri_value | target-nri target_nri ] | t3312-timeout seconds [ nri-value nri_value | target-nri
target_nri ] | target-nri target_nri [ imsi imsi | target-count num_to_offload ] }
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Important
Various combinations of the same command is issued based on whether it is a 2G, 3G, Null-NRI based
offloading, Target-NRI based offloading or IMSI based offloading and so on.
The following CLI has to be issued for the phase-3 of offloading:
clear subscribers sgsn-serviceservice_name {nri[ <val> | any ]}
Consider and SGSN node which was offloaded due to a maintenance requirement, once this SGSN is again
operational it will not recover the subscribers attached before the maintenance occurred. In due course this
SGSN will be leveraged, with subscribers moved from (partial offload) two or three most loaded SGSNs.
Monitoring and Troubleshooting the SGSN Pooling feature
SGSN Pooling Show Command(s) and/or Outputs
This section provides information regarding show commands and their outputs in support of the SGSN Pooling:
• show subscribers sgsn-only/gprs-only full all
• show sgsn-pool statistics sgsn-service
• show sgsn-pool statistics gprs-service
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37
SGSN Processes Uplink Data Status IE in Service
Request
This chapter describes the SGSN Processesing the Uplink Data Status IE in Service Request.
• Feature Description, page 489
• Standards Compliance, page 489
• Configuring Processing of Uplink Data Status IE in Service Request, page 490
• Monitoring and Troubleshooting the Feature, page 490
Feature Description
The Gn SGSN now supports processing of Uplink Data Status IE in Service Request; RABs are established
for NSAPIs present in the Uplink Data Status IE. With this feature enhancement the RAB's are selectively
established for NSAPIs which require uplink data transfer. In earlier releases RABs were established for all
PDPs. Support has been added to decode Uplink Data Status IE in the Service Request. Performance
improvement and reduced signaling are observed as RABs are established only for NSAPIs which require
uplink data transfer.
A new CLI command has been provided under the Call Control Profile to enable or disable this feature. The
user can configure the CLI to either ignore or process the Uplink Data Status IE in Service Request. This
feature is enabled by default.
Standards Compliance
This feature complies with the 3GPP TS24.008.
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Configuring Processing of Uplink Data Status IE in Service Request
Configuring Processing of Uplink Data Status IE in Service
Request
This section describes the configuration procedure for this feature. The following new CLI command under
the Call Control Profile is used enable or disable processing of Uplink Data Status IE in Service Request
config
call-control-profile profile_name
[remove] ignore-ul-data-status
exit
Notes:
• This feature is enabled by default, to disable the feature use the command ignore-ul-data-status.
• To enable this feature use the command remove ignore-ul-data-status.
• When this feature is enabled, RAB is established for NSAPIs present in the Uplink data status IE. RABs
are not established if the NSAPI PDPs are not present in the SGSN. If the Uplink data Status IE contains
NSAPI not known to the SGSN, the SGSN establishes all the RAB's. RAB's are not established if
corresponding NSAPI is absent in the PDP-Context Status IE.
• When this feature is disabled, if Uplink data status IE is received in service request the SGSN ignores
it and establishes RABs for all the PDPs.
Verifying the Configuration
The show call-control-profile full command is used to verify the configuration of this feature. The following
field displays whether the Uplink Data Status IE is Processed or Ignored:
• Uplink data status IE in service request
Monitoring and Troubleshooting the Feature
This section provides information on how to monitor the processing of Uplink Data Status IE in Service
Request.
Show Command(s) and/or Outputs
This section provides information regarding show commands and/or their outputs when the Uplink Data Status
IE is processed:
show gmm-sm statistics
This show command is updated to display the number of RABs not re-established due to absence of NSAPI
bit set in the Uplink Data Status IE. This field is also used as a measure to verify the reduction in radio
signaling. The new field Rab-Not-Re-Estd-UL-Data-Stat is added to the show output.
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38
SGSN Serving Radio Network Subsystem
Relocation
This chapter describes the SGSN Serving Radio Network Subsystem Relocation (SRNS) feature.
• Feature Description, page 491
• How it Works, page 492
• Configuring SRNS Relocation on the SGSN, page 528
• Monitoring and Troubleshooting SRNS Relocation, page 530
Feature Description
The SRNS relocation feature facilitates connected mode inter-RAT handovers between UTRAN (3G) networks
or between UTRAN and EUTRAN (LTE) networks. The advantage of this feature is that the radio bearer
establishment occurs before the actual handover at the target.
The Gn/Gp SGSN and S4-SGSN support inter- and intra-SGSN SRNS relocation to enable:
• Handovers of an MS from one RNC to another RNC
• Handovers of an MS from one RNC to an eNodeb
The S4-SGSN supports the optional setup of indirect data forwarding tunnels (IDFT) between the eNodeB
and the RNC via the SGW during connected mode handovers. This allows the S4-SGSN to support connected
mode handovers between the UTRAN and E-UTRAN networks across the S3 interface. IDFT is not supported
on the SGSN across the Gn interface.
The SRNS Relocation feature is included with the base SGSN license. It does not require an additional feature
license.
Relationships to Other Features
This section describes how the SRNS Relocation feature relates to other SGSN features.
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How it Works
• For an SGSN operating via the Gn/Gp interfaces, a 3G service (sgsn-service) must be configured and
enabled before SRNS Relocation can be configured.
• For an S4-SGSN, both a 3G service (sgsn-service) and S4-SGSN support (egtp-service) must be
configured before SRNS Relocation can be configured.
• If operators are using non-standard LAC ranges, then a network-global-mme-id-mgmt-db must be
configured and associated with the sgsn-service.
For detailed instructions on configuring the above, refer to the Cisco ASR 5000 Serving GPRS Support Node
Administration Guide.
How it Works
SRNS Relocation on the SGSN (Gn/Gp)
On the Gn/Gp SGSN, the SRNS relocation feature is triggered by subscribers (MS/UE) moving from one
RNS to another. If the originating RNS and destination RNS are connected to the same SGSN but are in
different routing areas, the behavior triggers an intra-SGSN Routing Area Update (RAU). If the RNSs are
connected to different SGSNs, the relocation is followed by an inter-SGSN RAU.
The following table describes the interface selection logic for the various types of SRNS relocation that can
occur when the interface used for a subscriber is Gn for PDP contexts. Note that the Gn/Gp SGSN SRNS
relocation selection logic is applicable in the following instances:
• An S4-SGSN is configured (both the S4 license and EGTP service are available), but a given subscriber
uses the Gn interface for PDP contexts.
• Only the Gn/Gp interfaces are utilized on the SGSN. S4 support is not configured.
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Table 35: Interface Selection Logic for SRNS Relocation on the SGSN Gn/Gp
SI.No
RNC Release Target Type
Compliance Sent in Rel.
Req.
LAC
LAC MSB Peer Type DNS Query
Configured Set
Type
as MME
Group ID
Interface Interface Chosen
IP
Provided
by DNS
1
R8+
eNodeB
Not
Irrelevant MME
Applicable
When the Gn Gn
interface is
used, the
system maps
the eNB ID to
the RNC ID as
follows: The
MSB 12 bits
of the 20 bit
eNB ID is
mapped to
RNC ID. DSN
A query with
RNC ID
FQDN is sent
and Gn
address is
selected.
Gn
2
R8+
RNC
Not
Irrelevant SGSN
Applicable
DNS A Query Gn
with RNC ID
FQDN
Gn
3
Pre R8
RNC
Irrelevant Irrelevant It is not
DNS A Query Gn
important with RNC ID
to a Gn
FQDN
SGSN if
the peer is
an MME
or an
SGSN.
For a Gn
SGSN, a
peer
MME is
treated
just like
an SGSN
Gn
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SGSN (Gn/Gp) SRNS Relocation Call Flow Diagrams
This section provides call flow diagrams and process descriptions for the following SGSN Gn/Gp SRNS
Relocation scenarios:
• Inter-SGSN (Gn/Gp) SRNS Relocation Call Flow
• Intra-SGSN (Gn/Gp) SRNS Relocation Call Flow
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The Inter-SGSN (Gn/Gp) SRNS Relocation procedure is illustrated in the following diagram.
Figure 97: Inter-SGSN Gn/Gp SRNS Relocation Call Flow
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Table 36: Inter-SGSN (Gn/Gp) SRNS Relocation Process Description
Step
Description
1
The source SRNC decides to perform/initiate SRNS relocation.
2
The source SRNC sends a Relocation Required message (Relocation Type, Cause,
Source ID, Target ID, Source RNC to target RNC transparent container) to the old
SGSN.
3
The old SGSN determines from the Target ID that an inter-SGSN SRNS relocation
is required. A DNS A query is performed for the target RNC ID FQDN to obtain the
target SGSN IP address. The old SGSN then sends a Forward Relocation Request to
the new SGSN.
4
The new SGSN sends a Relocation Request message to the new RNC. At this point,
radio access bearers have been established.
5
The new RNC sends a Relocation Request Response message to the new SGSN.
6
When resources for the transmission of user data between the new RNC and the new
SGSN have been allocated and the new SGSN is ready for relocation of SRNS, the
Forward Relocation Response message (Cause, RANAP Cause, and RAB Setup
Information) is sent from the new SGSN to the old SGSN.
7
The old SGSN continues the relocation of SRNS by sending a Relocation Command
message to the old RNC. The old SGSN sends the RAB setup information received
in the Forward Relocation Response in a Relocation Command to the old RNC. This
enables the old RNC to establish a data path with new RNC so that it can forward the
data packets.
8
The old SRNC may, according to the QoS profile, begin the forwarding of data for
the RABs to be subject for data forwarding.
9
Before sending the Relocation Commit the uplink and downlink data transfer in the
source, the SRNC shall be suspended for RABs, which require a delivery order. The
source RNC starts the data-forwarding timer. When the old SRNC is ready, the old
SRNC triggers the execution of relocation of SRNS by sending a Relocation Commit
message (SRNS Contexts) to the new RNC over the Iur interface.
10
The target RNC sends a Relocation Detect message to the new SGSN when the
relocation execution trigger is received.
11
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
12
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Complete message to the new SGSN.
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Step
Description
13
The old SGSN sends a Forward Relocation Complete message.
14
The old SGSN sends a Forward Relocation Acknowledgement to the new SGSN. to
signal to the new SGSN the completion of the SRNS relocation procedure.
15
Upon receipt of the Relocation Complete message, the CN switches the user plane
from the old RNC to the new SRNC. The new SGSN sends Update PDP Context
Request messages to the GGSN.
16
The GGSN sends Update PDP Context Response messages to the new SGSN.
17
The old SGSN sends an Iu Release Command message to the old RNC.
18
The old RNC sends an Iu Release Complete message to the old SGSN.
19
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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The intra-SGSN Gn/Gp SRNS Relocation procedure is illustrated in the following figure.
Figure 98: Intra-SGSN Gn/Gp SRNS Relocation Call Flow
Table 37: Intra-SGSN (Gn/Gp) SRNS Relocation Process Description
Step
Description
1
The source SRNC decides to perform/initiate SRNS relocation.
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Step
Description
2
The old RNC sends a Relocation Required message to the SGSN.
3
The SGSN sends a Relocation Request message to the new RNC. At this point, radio
access bearers have been established.
4
The new RNC sends a Relocation Request Acknowledgement message to the SGSN.
5
The SGSN sends a Relocation Command to the old RNC and the UE is detached from
the old RNC and attached to the new RNC.
6
The old SRNC may, according to the QoS profile, begin the forwarding of data for
the RABs to be subject for data forwarding.
7
Before sending the Relocation Commit the uplink and downlink data transfer in the
source, the SRNC shall be suspended for RABs, which require a delivery order. The
source RNC starts the data-forwarding timer. When the old SRNC is ready, the old
SRNC triggers the execution of relocation of SRNS by sending a Relocation Commit
message (SRNS Contexts) to the new RNC over the Iur interface.
8
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
9
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
10
The new RNC sends a Relocation Detect message to the SGSN.
11
The SGSN sends a Relocation Complete message to the new RNC.
12
If Direct Tunnel was established during intra-SGSN SRNS relocation, the SGSN
sends Update PDP Context Request messages to the GGSN.
13
If Direct Tunnel was established during intra-SGSN SRNS relocation, the SGSN
sends Update PDP Context Response messages to the GGSN.
14
The SGSN sends an Iu Release Command to the old RNC.
15
The old RNC releases the Iu connection and sends a Release Complete message to
the SGSN.
16
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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SRNS Relocation on the S4-SGSN
On the S4-SGSN, the SRNS relocation feature is triggered by subscribers (MS/UE) moving between an
eNodeB and an RNC or between two RNCs.
If the originating and destination nodes are connected to the same S4-SGSN but are in different routing areas,
the behavior triggers an intra-SGSN Routing Area Update (RAU).
If the nodes are connected to different S4-SGSNs, the relocation is followed by an inter-SGSN RAU. This
RAU occurs over a RANAP direct transfer. As a result, it does not trigger Context Request/Context
Response/Context Ack procedures with the old SGSN/MME. These procedures are otherwise performed
during a normal SGSN RAU.
The GTPv2 protocol is used for SRNS relocation between two RNCs and between an eNodeB and an RNC.
In addition to supporting Inter-SGSN SRNS relocation across the Gn interface, the S4-SGSN supports SRNS
relocation for the following scenarios across the S3 (S4-SGSN to MME) and S16 (S4-SGSN to S4-SGSN)
interfaces:
• Inter-SGSN SRNS relocation over the S16 interface
• UTRAN-to-E-UTRAN connected mode Inter-RAT handover over the S3 interface
• E-UTRAN-to-UTRAN connected mode Inter-RAT handover over the S3 interface
As part of the SRNS relocation feature implementation on the S4-SGSN, the SGSN application also supports
the gtpv2 (egtp) protocol for:
• Inter-SGSN SRNS relocations over the S16 interface
• MME - SGSN SRNS relocations over the S3 interface
S4-SGSN SRNS relocation interface selection logic is based on the following assumptions:
• If the egtp-service is configured, it is assumed the network is EPC capable and therefore must require
a DNS SNAPTR.
• If the egtp-service is configured on the S4-SGSN, then for outbound SRNS relocation, the system always
performs a DNS SNAPTR as follows:
•
◦x-S16 if the peer detected is another S4-GSN, or x-S3 if the peer detected is an MME (based on
whether the target is an eNodeB/the MSB of the target LAC being 1, or, if a local MME group ID
is configured).
◦x-gn if a local configuration for a peer SGSN or MME exists with a Gn address, or, if DNS SNAPTR
returned a GN address.
If both DNS queries fail, the system rejects the SRNS relocation.
The following table describes the interface selection logic for the various types of SRNS relocation that can
occur when the interface used for a subscriber is S4 for PDP contexts.
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Table 38: Interface Selection Logic for S4-SGSN SRNS Relocation
SI.No
RNC
Target Type
Release
Sent in
Compliance Relocation
Request
LAC
LAC MSB
Configured as Set
MME Group ID
Peer Type
Type of DNS
Query
Interface
IP
Provided
by DNS
Interface Chosen
1
R8+
eNodeB
n/a
n/a
MME
DNS
S3
SNAPTR w/
service type
x-3gpp-mme:x-s3
and TAC
FQDN
S3
2
R8+
eNodeB
n/a
n/a
MME
DNS
Gn
SNAPTR w/
service type
x-3gpp-mme:x-s3
and TAC
FQDN
When a TAC
FQDN is used to
query the MME
address the
system expects
that the MME
supports S3
interface. If this
is the case, the S3
interface is
chosen. If DNS
returns a Gn
address, then the
system rejects the
Relocation, and
sends a
Relocation
Preparation
Failure to the
source RNC.
3
R8+
RNC
n/a
n/a
SGSN
DNS
S16
SNAPTR w/
service type
x-3gpp-sgsn:x-s16
and RNC ID
FQDN
S16
4
R8+
RNC
n/a
n/a
SGSN
DNS
Gn
SNAPTR w/
service type
x-3gpp-sgsn:x-s16
and RNC ID
FQDN
Gn
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SI.No
RNC
Target Type
Release
Sent in
Compliance Relocation
Request
LAC
LAC MSB
Configured as Set
MME Group ID
Peer Type
Type of DNS
Query
5
Pre R8
RNC (A pre R8 Yes
RNC cannot
send eNB as
the target type.
Currently,
operators
configure eNB
ID to RNC ID
mapping in
such these pre
R8 RNCs so
that the SGSN
receives an
RNC ID that is
actually
mapped from
the eNB ID)
6
Pre R8
RNC
7
Pre R8
8
Pre R8
Irrelevant
MME
DNS
S3
SNAPTR w/
service type
x-3gpp-mme:x-s3
and MME GI
+ MME
Code FQDN
S3
Yes
Irrelevant
MME
DNS
Gn
SNAPTR w/
service type
x-3gpp-mme:x-s3
and MME GI
+ MME
Code FQDN
Gn
RNC
No
Yes
MME
DNS
S3
SNAPTR w/
service type
x-3gpp-mme:x-s3
and MME GI
+ MME
Code FQDN
S3
RNC
No
Yes
MME
DNS
Gn
SNAPTR w/
service type
x-3gpp-mme:x-s3
and MME GI
+ MME
Code FQDN
Gn
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IP
Provided
by DNS
Interface Chosen
SGSN Serving Radio Network Subsystem Relocation
SRNS Relocation on the S4-SGSN
SI.No
RNC
Target Type
Release
Sent in
Compliance Relocation
Request
LAC
LAC MSB
Configured as Set
MME Group ID
Peer Type
Type of DNS
Query
Interface
IP
Provided
by DNS
Interface Chosen
9
Pre R8
RNC
No
No
SGSN
DNS
S16
SNAPTR w/
service type
x-3gpp-sgsn:x-s16
and RNC ID
FQDN
S16
10
Pre R8
RNC
No
No
SGSN
DNS
Gn
SNAPTR w/
service type
x-3gpp-sgsn:x-s16
and RNC ID
FQDN
Gn
IDFT Support During Connected Mode Handovers
The S4-SGSN supports the setup of indirect data forwarding tunnels (IDFT) between the eNodeB and the
RNC via the SGW during connected mode handovers.
Once enabled, IDFT is employed under the following conditions:
• If the SGSN is the old node:
◦The target node to which the connected mode handover is initiated should be an eNodeB (i.e., the
SGSN performs the handover to the MME).
◦The enb-direct-data-forward CLI setting is not configured as the source RNC configuration (in
RNC Configuration Mode).
• If the SGSN is the new node:
◦The source node from which connected mode handover is initiated is an eNodeB (i.e., the MME
is performing a handover to the SGSN).
◦The enb-direct-data-forward setting is not configured in the source RNC configuration (in RNC
Configuration Mode).
◦The source MME indicated that it does not support direct forwarding via a Forward Relocation
Request.
Important
If the target SGSN did not relocate to a new SGW, IDFT setup does not apply at the SGSN. The target
SGSN sets up an indirect data forwarding tunnel with the SGW only if the SGW is relocated. If the SGW
is not relocated, then it is the source MME that sets up the indirect data forwarding tunnel between source
the eNodeB and target RNC through the SGW.
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The following diagram illustrates the interface selection logic for S4-SGSN connected mode handovers.
Figure 99: Interface Selection Logic for S4-SGSN SRNS Connected Mode Handovers
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S4-SGSN SRNS Relocation Call Flow Diagrams
This section provides call flow diagrams for the following S4-SGSN SRNS relocation scenarios:
• Inter-S4-SGSN SRNS Relocation without SGW Relocation
• Inter-S4-SGSN Relocation with SGW Relocation
• Intra-S4-SGSN SRNS Relocation without SGW Relocation
• Inter-S4-SGSN Relocation with SGW Relocation
• S4-SGSN E-UTRAN to UTRAN Connected Mode Handover without SGW Relocation
• S4-SGSN UTRAN to E-UTRAN Connected Mode Handover with SGW Relocation Call Flow
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• S4-SGSN Inter-SGSN SRNS Relocation with Hard Handover and SGW Relocation
Figure 100: S4 Inter-SGSN SRNS Relocation without SGW Relocation Call Flow
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Table 39: Inter-S4-SGSN SRNS Relocation without SGW Relocation Process Description
Step
Description
1
The decision is made to perform SRNS relocation.
2
The old RNC sends a Relocation Required message to the old SGSN.
3
The old SGSN sends a Forward Relocation Request to the new SGSN.
4
The new SGSN performs SGW selection, but does not select a new SGW, as the
subscriber is anchored at the same SGW as it was previously.
5
The new SGSN sends a Relocation Request message to the new RNC. At this point,
Radio Access Bearers are established.
6
The new RNC sends a Relocation Request Acknowledgment to the new SGSN.
7
The new SGSN sends a Forward Relocation Response to the old SGSN. In this
message, the old SGSN sends the RAB context information of the new RNC, which
was obtained from the Relocation Request Ack message.
8
The old SGSN sends a Relocation Command to the old RNC. The old SGSN sends
the new RNC RAB context information to the old RNC in the Relocation Command
message so that old RNC can forward packets to the new RNC.
9
The old SRNC may, according to the QoS profile, begin the forwarding of data for
the RABs to be subject for data forwarding.
10
Before sending the Relocation Commit the uplink and downlink data transfer in the
source, the SRNC shall be suspended for RABs, which require a delivery order. The
source RNC starts the data-forwarding timer. When the old SRNC is ready, the old
SRNC triggers the execution of relocation of SRNS by sending a Relocation Commit
message (SRNS Contexts) to the new RNC over the Iur interface.
11
The new RNC sends a Relocation Detect message to the new SGSN.
12
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
13
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
14
The new RNC sends a Relocation Complete message to the new SGSN.
15
The new SGSN sends a Forward Relocation Notification Complete message to the
old SGSN.
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Step
Description
16
The new SGSN sends a Forward Relocation Complete Ack message to the old SGSN.
17
The new SGSN sends a Modify Bearer Request to the SGW.
18
The SGW sends a Modify Bearer Response to the new SGSN.
19
The old SGSN sends an Iu Release Command message to the old RNC.
20
The old RNC sends an Iu Release Complete message to the old SGSN.
21
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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Figure 101: Inter-S4-SGSN Relocation with SGW Relocation
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Table 40: Inter-S4-SGSN Relocation with SGW Relocation Process Description
Step
Description
1
The decision is made to perform SRNS relocation.
2
The old RNC informs the old SGSN that relocation is required by sending a Relocation
Required message.
3
The old SGSN initiates the relocation resource allocation procedure by sending a
Forward Relocation Request message to the new SGSN.
4
The new SGSN performs SGW selection.
5
The new SGSN sends a Create Session Request to the new SGW with Indication Flags
- Operations Indication bit = 0. The new SGW will not send a Modify Bearer Request
to the PGW at this time.
6
The new SGW sends a Create Session Response to the new SGSN.
7
The new SGSN sends a Relocation Request to the new RNC. At this point radio access
bearers are set up between the new RNC and the new SGSN.
8
The new RNC sends a Relocation Request Acknowledge message to the new SGSN.
9
The new SGSN sends a Forward Relocation Response message to the old SGSN. In
this message, the old SGSN sends the RAB context information of the new RNC,
which was obtained from Relocation Request Acknowledge message.
10
The old SGSN sends a Relocation Command to the old RNC. The old SGSN sends
the new RNC RAB context information to the old RNC in the Relocation Command
so that the old RNC can forward packets to the new RNC.
11
The old SRNC may, according to the QoS profile, begin the forwarding of data for
the RABs to be subject for data forwarding.
12
Before sending the Relocation Commit the uplink and downlink data transfer in the
source, the SRNC shall be suspended for RABs, which require a delivery order. The
source RNC starts the data-forwarding timer. When the old SRNC is ready, the old
SRNC triggers the execution of relocation of SRNS by sending a Relocation Commit
message (SRNS Contexts) to the new RNC over the Iur interface.
13
The new RNC sends a Relocation Detect message to the new SGSN.
14
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
15
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
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Step
Description
16
The new RNC sends a Relocation Complete message to the new SGSN.
17
The new SGSN sends a Forward Relocation Complete Notification message to the
old SGSN.
18
The old SGSN sends a Forward Relocation Complete Ack message to the new SGSN.
19
The new SGSN sends a Modify Bearer Request message to the new SGW.
20
The SGW sends a Modify Bearer Request message to the PGW.
21
The PGW sends a Modify Bearer Response to the new SGW.
22
The SGW sends a Modify Bearer Response to the new SGSN.
23
The old SGSN sends a Delete Session Request to the old SGW.
24
The old SGW sends a Delete Session Response to the old SGSN.
25
The old SGSN sends an Iu Release Command message to the old RNC.
26
The old RNC sends an Iu Release Complete message to the old SGSN.
27
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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Figure 102: Intra-S4-SGSN SRNS Relocation without SGW Relocation
Table 41: Intra-S4-SGSN SRNS Relocation without SGW Relocation Process Description
Step
Description
1
The decision is made to perform SRNS relocation.
2
The old RNC sends a Relocation Required message to the SGSN.
3
The SGSN performs SGW selection, but does not select a new SGW, as the subscriber
is anchored at the same SGW as it was previously.
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Step
Description
4
The SGSN sends a Relocation Request message to the new RNC. At this point, radio
access bearers have been established.
5
The new RNC sends a Relocation Request Acknowledgment message to the SGSN.
6
The SGSN sends a Relocation Command to the old RNC and the UE is detached from
the old RNC and attached to the new RNC.
7
The old SRNC may, according to the QoS profile, begin the forwarding of data for
the RABs to be subject for data forwarding.
8
Before sending the Relocation Commit the uplink and downlink data transfer in the
source, the SRNC shall be suspended for RABs, which require a delivery order. The
source RNC starts the data-forwarding timer. When the old SRNC is ready, the old
SRNC triggers the execution of relocation of SRNS by sending a Relocation Commit
message (SRNS Contexts) to the new RNC over the Iur interface.
9
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
10
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
11
The new RNC sends a Relocation Detect message to the SGSN.
12
The SGSN sends a Relocation Complete message to the new RNC.
13
The SGSN sends an Iu Release Command to the old RNC.
14
The old RNC releases the Iu connection and sends a Release Complete message to
the SGSN.
15
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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Figure 103: Intra-S4-SGSN Relocation with SGW Relocation
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Table 42: Intra-S4-SGSN Relocation with SGW Relocation Process Description
Step
Description
1
The decision is made to perform SRNS relocation.
2
The old RNC sends a Relocation Required message to the SGSN.
3
The SGSN selects a new SGW for the UE.
4
The SGSN sends a Create Session Request to the new SGW with Indication Flags Operations Indication bit=0. The new SGW does not send a Modify Beater Request
to the PGW at this time.
5
The new SGW sends a Create Session Response to the SGSN.
6
The SGSN sends a Relocation Request to the new RNC. At this point, radio access
bearers have been established.
7
The new RNC sends a Relocation Request Acknowledge message to the SGSN.
8
The SGSN sends a Relocation Command to the old RNC.
9
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
10
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
11
The new RNC sends a RAN Mobility Information message. This message contains
UE information elements and CN information elements.
12
When the new SRNC receives the RAN Mobility Information Confirm message, i.e.
the new SRNCID + S-RNTI are successfully exchanged with the MS by the radio
protocols, the target SRNC initiates the Relocation Complete procedure by sending
the Relocation Commit message to the new SGSN.
13
The new RNC sends a Relocation Detect message to the SGSN.
14
The new RNC sends a Relocation Complete message to the SGSN.
15
The SGSN sends a Modify Bearer Request message to the new SGW.
16
The new SGW sends a Modify Bearer Request to the PGW.
17
The PGW sends a Modify Bearer Response to the new SGW.
18
The new SGW sends a Modify Bearer Response to the SGSN.
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Step
Description
19
The SGSN sends a Delete Session Request to the old SGW.
20
The old SGW sends a Delete Session Response to the SGSN.
21
The SGSN sends an Iu Release Command to the old RNC.
22
The old RNC sends an Iu Release Complete message to the SGSN.
23
After the MS has finished the RNTI reallocation procedure, and if the new Routing
Area Identification is different from the old one, the MS initiates the Routing Area
Update procedure.
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Figure 104: S4-SGSN E-UTRAN to UTRAN Connected Mode Handover without SGW Relocation Call Flow
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Table 43: S4-SGSN E-UTRAN to UTRAN Connected Mode Handover without SGW Relocation Process Description
Step
Description
1
The eNodeB determines that relocation is required and sends a Relocation Required
message to the old MME.
2
The old MME sends a Forward Relocation Request message to the new SGSN.
3
The new SGSN performs SGW selection for the UE.
4
The new SGSN sends a Relocation Request message to the new RNC. At this time,
radio access bearers are established.
5
The new RNC sends a Relocation Request Ack message to the new SGSN.
6
The new SGSN sends a Forward Relocation Response to the old MME.
7
The old MME sends a Create Indirect Data Forwarding Tunnel Request message to the
SGW (if IDFT is configured on the SGSN and MME).
8
The SGW sends a Create Indirect Data Forwarding Tunnel Response message to the
old MME (if IDFT is configured on the SGSN and MME).
9
The old MME sends a Handover Command message to the eNodeB.
10
Downlink packets are sent from the SGW to the eNodeB.
11
Downlink packets are sent from the eNodeB to the SGW via Indirect Data Forwarding
Tunnel (if IDFT is configured on the new SGSN and the old MME). Downlink packets
then are sent from the SGW to the new SGSN, and finally, from the new SGSN to the
new RNC.
12
The new RNC sends a Relocation Detect message to the new SGSN.
13
The new RNC sends a Relocation Complete message to the new SGSN.
14
The new SGSN sends a Forward Relocation Complete Notification message to the old
MME.
15
The old MME sends a Forward Relocation Complete Ack message to the new SGSN.
16
The new SGSN sends a Modify Bearer Request message to the SGW.
17
The new SGW sends a Modify Bearer Request message to the PGW.
18
The PGW sends a Modify Bearer Response message to the SGW.
19
The new SGW sends a Modify Bearer Response message to the new SGSN.
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Step
Description
20
After timer expiry, the old MME sends a Delete IDFT Tunnel Request to the SGW and
deletes the IDFT tunnel.
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Figure 105: S4-SGSN UTRAN to E-UTRAN Connected Mode Handover with SGW Relocation Call Flow
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Table 44: S4-SGSN UTRAN to E-UTRAN Connected Mode Handover with SGW Relocation Process Description
Step
Description
1
The old RNC determines that relocation is required for a UE and sends a Relocation
Required message to the old SGSN.
2
The old SGSN sends a Forward Relocation Request message to the new MME.
3
The new MME performs the selection of a new SGW.
4
The new MME sends a Create Session Request message to the new SGW.
5
The new SGW sends a Create Session Response to the new MME.
6
The new MME sends a Handover Request message to the eNobeB. At this point radio
access bearers are established.
7
The eNodeB sends a Handover Request Ack message to the new MME.
8
The MME sends an Indirect Data Forwarding Tunnel Request to the new SGW.
9
The new SGW sends an Indirect Data Forwarding Tunnel Response to the new MME.
The new SGW sends the SGW DL data forwarding TEID to the MME in this message.
10
The new MME sends a Forward Relocation Response message to the old SGSN. The
new MME forwards the SGW DL data forwarding TEID received in step 9 to the old
SGSN in this message.
11
The old SGSN sends a Create IDFT Request to the old SGW. The old SGSN sends the
SGW DL data forwarding TEID received in step 10 to the old SGW in this request.
This enables the old SGW to setup an indirect forwarding path towards the new SGW.
12
The old SGW sends a Create IDFT Response to the old SGSN. The old SGW sends the
SGW DL data forwarding TEID to the SGSN in this message. The SGSN will forward
the re-forwarded downlink packets back to the old SGW to this TEID.
13
The old SGSN sends a Relocation Command to the old RNC. Downlink packets are
then routed through the architecture in the following manner:
• PGW to old SGW
• Old SGW to old SGSN
• Old SGSN to old RNC
• Old RNC to old SGSN
• Old SGSN to old SGW
• Old SGW to new SGW
• New SGW to eNodeB
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Step
Description
14
The eNodeB sends a Handover Complete message to the new MME.
15
The new MME sends a Forward Relocation Complete message to the old SGSN.
16
The old SGSN sends a Forward Relocation Complete Notification message to the new
MME.
17
The new MME sends a Modify Bearer Request to the new SGW.
18
The new SGW sends a Modify Bearer Request to the PGW.
19
The PGW sends a Modify Bearer Response to the new SGW.
20
The new SGW sends a Modify Bearer Response to the new MME.
21
After timer expiry, the old SGSN sends a Delete Session Request to the old SGW.
22
The old SGW sends a Delete Session Response to the old SGSN.
23
The old SGSN also sends a Delete IDFT Request to the old SGW.
24
Similar to the timer started at the old SGSN, the new MME also would have started a
timer to guard the holding of the IDFT tunnel created there. Upon expiry of this timer,
the new MME sends a Delete IDFT Request to the new SGW.
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Figure 106: S4-SGSN Inter-SGSN Hard Handover and SGW Relocation (Part 1)
Figure 107: S4-SGSN Inter-SGSN Relocation with Hard Handover and SGW Relocation (Part 2)
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Table 45: S4-SGSN Inter-SGSN Hard Handover with SGW Relocation Process Description
Step
Description
1
The decision is made to initiate relocation.
2
The source RNC sends a Relocation Required message to the target RNC.
3
The old SGSN selects the new SGSN and sends a Forward Relocation Request message
to the new SGSN.
4
The new SGSN sends a Create Session Request message to the new SGW.
5
The new SGW sends a Create Session Response back to the new SGSN.
6
The new SGSN sends a Relocation Request message to the new RNC.
7
The new RNC sends a Relocation Request Acknowledgment back to the new SGSN.
8
The new SGSN sends a Forward Relocation Response message to the old SGSN.
9
The old SGSN sends a Relocation Command to the old RNC.
10
The old RNC sends the RRC message to the UE. Upon reception of this message the
UE will remove any EPS bearers for which it did not receive the corresponding EPS
radio bearers in the target cell.
11
The old RNC sends a Forward SRNS Context message to the old SGSN.
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Step
Description
12
The old SGSN sends a Forward Access Context Notification message to the new
SGSN.
13
The new SGSN sends a Forward Access Context Acknowledge message to the old
SGSN
14
The new SGSN sends a Forward SRNS Context message to the new RNC. At this
point, the UE detaches from the old RNC and attaches to the new RNC.
15
The source RNC should start direct forwarding of downlink data from the source RNC
towards the target RNC for bearers subject to data forwarding.
16
The UE sends an RRC message to the new RNC. Downlink packets forwarded from
the old RNC can be sent to the UE. In addition, uplink packets can be sent from the
UE, which are forwarded to the new SGW and then on to the PGW.
17
The new RNC sends a Relocation Complete message to the new SGSN.
18
The new SGSN then ends a Forward Relocation Complete Notification message to
the old SGSN.
19
The old SGSN sends a Forward Relocation Complete Acknowledgement message to
the new SGSN.
20
The new SGSN sends a Modify Bearer Request message to the new SGW for each
PDN connection.
21
The new SGW sends a Modify Bearer Request message to the PGW.
22
The PGW sends a Modify Bearer Response message to the new SGW.
23
The new SGW sends a Modify Bearer Response message to the new SGSN. The PGW
begins sending downlink packets to the new SGW, which in turn sends them to the
new RNC, and then to the UE.
24
The UE initiates a Routing Area Update procedure. This RAU occurs on a RANAP
Direct Transfer and therefore does not involve a Context transfer with the peer SGSN.
25
The old SGSN sends a Delete Session Request to the old SGW.
26
The old SGSN sends an Iu Release Command to the old RNC.
27
The old RNC then sends a Iu Release Complete message to the old SGSN.
28
The old SGW sends a Delete Session Response message to the old SGSN.
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Standards Compliance
Standards Compliance
The SGSN SRNS Relocation feature complies with the following standards:
• SGSN Gn/Gp SRNS Relocation: 3GPP TS 23.060 V8.10.0 (2010-09): 3rd Generation Partnership
Project Technical Specification Group Services and System Aspects General Packet Radio Service
(GPRS) Service description Stage 2 (Release 8)
• S4-SGSN (S3/S16) SRNS Relocation: 3GPP TS 23.060 V9.8.0 (2011-03): 3rd Generation Partnership
Project Technical Specification Group Services and System Aspects General Packet Radio Service
(GPRS) Service description Stage 2 (Release 9)
• MME to 3G SGSN Hard Handover and Relocation: LTE General Packet Radio Service (GPRS)
enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (3GPP TS
23.401 version 9.8.0 Release 9)
Configuring SRNS Relocation on the SGSN
This section provides examples of how to configure the SRNS relocation feature on the SGSN. An optional
configuration example is also provided for enabling IDFT.
Important
After creating or modifying the configuration for an S4-SGSN, you must save the configuration and reboot
the S4-SGSN node for the change(s) to take effect.
Configuring the SRNS Relocation Feature
Configuring the SRNS Relocation feature includes creating a call-control-profile and then enabling intraand/or inter-SGSN SRNS relocation via the Command Line Interface (CLI).
config
call-control-profile cc-profile name
srns-intra all failure-code integer
srns-inter all failure-code integer
end
config
context context_name
iups-service iups_service_name
inter-rnc-procedures source-rnc-as-target
Notes:
• cc-profile-name is the name assigned to this call-control-profile
• srns-intra all enables intra-SGSN SRNS relocations for all location areas.
• srns-inter all enables inter-SGSN SRNS relocations for all location areas.
• failure-code integer specifies the failure code that applies to SRNS relocations.
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Verifying the SRNS Feature Configuration
• Optionally, operators can use the restrict and allow keywords to identify specific location areas where
SRNS relocation will, or will not, occur. For detailed information on these optional keywords, refer to
the Cisco ASR 5x00 Command Line Reference.
• inter-rnc-procedures source-rnc-as-target: Optional. Configures the SGSN to support SRNS relocation
for those scenarios where the source RNC is behaving as the target RNC. The default is not to allow
SRNS relocation in those scenarios.
Enabling IDFT (Optional, S4-SGSN Only)
To enable support of IDFT between the eNodeB and a specified RNC via the SGW during connected mode
handovers on the S4-SGSN:
config
context context_name
iups-service iups_service_name
rnc id rnc_id
no enb-direct-data-forward
end
Where:
• no enb-direct-data-forward enables the setup of IDFT between the eNodeB and the RNC via the SGW
for connected mode inter RAT handovers. If IDFT is enabled, the SGSN/MME will send the IDFT
request towards the SGW.
• To disable IDFT, enter the enb-direct-data-forward command.
Verifying the SRNS Feature Configuration
This section describes how to verify that SRNS feature configuration.
The following commands provide information on how the SRNS relocation feature is configured:
show call-control-profile full all
show call-control-profile full name cc-profile-name
The output of these commands includes the complete SRNS configuration for the specified Call Control
Profile. For example:
[local]asr5x00 show call-control-profile
...
...
...
SRNS Intra All
SRNS Intra All Failure Code
SRNS Inter All
SRNS Inter All Failure Code
...
...
...
name cc-profile-name
:
Allow
: 10
: Allow
: 15
The following command provides information on how IDFT is configured:
show iups-service name service_name
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The output of this command indicates whether IDFT is enabled or disabled for the RNC configuration. If the
E-Node Direct Data Forwarding setting reads "Disabled," then IDFT is enabled. If it reads "Enabled," then
IDFT is disabled.
[local]asr5x00 show iups-service name
..
..
..
Available RNC:
..
..
..
E-NodeB Direct Data Forwarding
..
..
..
service-name
: Disabled
Monitoring and Troubleshooting SRNS Relocation
This section provides information that assists operators in monitoring and troubleshooting the SRSN Relocation
feature.
SRNS Bulk Statistics
The following statistics are included in the SGSN Schema in support of the SRNS Relocation feature. For
detailed descriptions of these bulk statistics, refer to the ASR 5x00 Statistics and Counters Reference.
Table 46: SRNS Relocation Feature Bulk Statistics
Bulk Statistics Supporting SRNS Relocation Feature
SRNS-ctxt-req-sent
srns-ctx-deny-ip-up-failure
SRNS-ctxt-rsp-rcvd
srns-ctx-deny-reloc-alloc-expiry
SRNS-ctxt-req-tmr-expired
srns-ctx-deny-reloc-failure-target-system
SRNS-ctxt-total-pdp-acc
srns-ctx-deny-invalid-rdb-id
SRNS-ctxt-total-pdp-rej
srns-ctx-deny-no-remaining-rab
SRNS-data-fwd-cmd-sent
srns-ctx-deny-interaction-with-other-proc
srns-ctx-deny-rab-preempt
srns-ctx-deny-integrity-check-fail
srns-ctx-deny-reloc-overall-tmr-exp
srns-ctx-deny-req-type-not-supported
srns-ctx-deny-reloc-prep-tmr-exp
srns-ctx-deny-req-superseeded
srns-ctx-deny-reloc-complete-tmr-exp
srns-ctx-deny-rel-due-to-ue-sig-con-rel
srns-ctx-deny-queuing-tmr-exp
srns-ctx-deny-res-optimization-reloc
srns-ctx-deny-reloc-triggered
srns-ctx-deny-req-info-unavail
srns-ctx-deny-unable-to-est-reloc
srns-ctx-deny-reloc-due-to-radio-reason
srns-ctx-deny-unknown-target-rnc
srns-ctx-deny-reloc-unsupport-target-sys
srns-ctx-deny-reloc-cancel
srns-ctx-deny-directed-retry
srns-ctx-deny-reloc-success
srns-ctx-deny-radio-con-with-ue-lost
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Bulk Statistics Supporting SRNS Relocation Feature
srns-ctx-deny-cypher-algo-no-support
srns-ctx-deny-rnc-unable-to-estab-all-rfcs
srns-ctx-deny-conflict-cypher-info
srns-ctx-deny-deciphering-keys-unavail
srns-ctx-deny-failure-radio-if-proc
srns-ctx-deny-dedicated-assist-data-unavail
srns-ctx-deny-rel-utran-reason
srns-ctx-deny-reloc-target-not-allowed
srns-ctx-deny-utran-inactivity
srns-ctx-deny-location-reporting-congestion
srns-ctx-deny-time-crit-relocation
srns-ctx-deny-reduce-load-in-serving-cell
srns-ctx-deny-req-traffic-class-unavail
srns-ctx-deny-no-radio-res-avail-target-cell
srns-ctx-deny-invalid-rab-param-val
srns-ctx-deny-geran-iu-mode-failure
srns-ctx-deny-req-max-bit-rate-unavail
srns-ctx-deny-access-restrict-shared-nwtk
srns-ctx-deny-req-max-bit-rate-dl-unavail
srns-ctx-deny-in-reloc-nwt-support-puesbine
srns-ctx-deny-req-max-bit-rate-ul-unavail
srns-ctx-deny-traffic-target-more-src-cell
srns-ctx-deny-req-gbr-unavail
srns-ctx-deny-mbms-no-multicat-svc-for-ue
srns-ctx-deny-req-gbr-dl-unavail
srns-ctx-deny-mbms-unknown-ue-id
srns-ctx-deny-req-gbr-ul-unavail
srns-ctx-deny-mbms-sess-start-no-data-bearer
srns-ctx-deny-req-trans-delay-not-achieve
srns-ctx-deny-mbms-superseed-nnsf
srns-ctx-deny-inval-rab-param-combo
srns-ctx-deny-mbms-ue-linking-already-done
srns-ctx-deny-violation-for-sdu-param
srns-ctx-deny-mbms-ue-delinking-failure
srns-ctx-deny-violation-traffic-hanlde-prio
srns-ctx-deny-tmgi-unknown
srns-ctx-deny-violation-for-gbr
srns-ctx-deny-ms-unspecified-failure
srns-ctx-deny-usr-plane-ver-unsupported
srns-ctx-deny-no-response-from-rnc
Show Command Output Supporting the SRNS Relocation Feature
This section provides information regarding CLI show commands that provide output to support of the SRSN
Relocation feature.
The following show commands are available in support of the SRNS Relocation feature on the SGSN and
the S4-SGSN:
show s4-sgsn statistics all
show gmm-sm statistics
The following counters are included in the show gmm-sm statistics command output to support the SRNS
Relocation feature. These statistics provide information on RAN application messages and the total number
of attempted and successful SGSN Gn/Gp and S4-SGSN SRNS relocations. These totals are further subdivided
by SRNS relocation type. Note that these statistics apply to the SGSN (Gn/Gp) and the S4-SGSN on the
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SGSN-RNC-UE interface side. For detailed descriptions of these statistics, refer to the ASR 5x00 Statistics
and Counters Reference.
Table 47: GMM SM Statistics Supporting SRNS Relocation
GMM SM Statistics Supporting SRNS Relocation
RANAP Procedures
Relocation Required
Relocation Complete
Relocation Request
Relocation Command
Relocation Failure
Relocation Request Ack
Relocation Cancel
Relocation Prep Failure
Relocation Detect
Relocation Cancel Ack
3G-SRNS Stats
Attempted
Successful
Total SRNS
Total SRNS
Intra-SGSN SRNS
Intra-SGSN SRNS
Intra-SRNS UE involved
Intra-SRNS UE involved
Intra-SRNS UE not involved
Intra-SRNS UE not involved
Inter-SGSN SRNS
Inter-SGSN SRNS
Inter-SRNS UE involved (old SGSN)
Inter-SRNS UE involved (old SGSN)
Inter-SRNS UE not involved (old SGSN)
Inter-SRNS UE not involved (old SGSN)
Inter-SGSN UE involved (new SGSN)
Inter-SGSN UE involved (new SGSN)
Inter-SGSN UE not involved (new SGSN)
Inter-SGSN UE not involved (new SGSN)
Inter-SGSN UE involved (old SGSN with MME)
Inter-SGSN UE involved (old SGSN with MME)
Inter-SGSN UE not involved (old SGSN with MME Inter-SGSN UE not involved (old SGSN with MME
Inter-SGSN UE involved (new SGSN with MME)
Inter-SGSN UE involved (new SGSN with MME)
Inter-SGSN UE not involved (new SGSN with MME) Inter-SGSN UE not involved (new SGSN with MME)
The following counters are included in the show s4-sgsn statistics all command output in support of the
SRNS Relocation feature. These statistics apply to the S4 interface network level. They provide information
on the number and type of SRNS SGW relocations, SRNS procedure aborts, and IDFT packets and bytes sent
to and from the SGW (if IDFT is enabled). For detailed descriptions of these statistics, refer to the ASR 5x00
Statistics and Counters Reference.
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Table 48: Statistics Supporting S4-SGSN SRNS Relocation
Statistics Supporting SRNS Relocation on the S4-SGSN
SGW Relocations
3G Intra SGSN SRNS Relocation
3G Inter SGSN SRNS Relocation (S16)
MME-SGSN SRNS Relocation (S3)
Procedure Abort Statistics
3G Intra SRNS Abort Due to Total CSR Failure
3G New SGSN SRNS Abort Due to Total CSR Failure
GTPU Statistics
IDFT packets to SGW
IDFT packets from SGW
IDFT bytes to SGW
IDFT bytes from SGW
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CHAPTER
39
SGSN Support for IMSI Manager Scaling
• Feature Description, page 535
• How it Works, page 536
• Configuring Support for Multiple IMSI Managers, page 537
• Monitoring and Troubleshooting the Multiple IMSI Manager Support, page 537
Feature Description
The IMSI Manager is a de-multiplex process that selects the Session Manager instance based on the de-multiplex
algorithm logic to host a new session. The IMSI Manager process also maintains the mapping of IMSI/F-PTMSI
(UE identifier) to the Session Manager instance. Currently only a single instance of the IMSI Manager task
is present on the SGSN or SGSN and MME combo nodes. This feature is developed to increase the number
of IMSI Manager Instances. The maximum number of IMSI Managers supported on ASR5000 and SSI remains
at "1". This feature is only supported on ASR5500 and VPC-DI platforms.
The IMSI Manager task is a bottleneck during single event performance testing, the Attach/RAU rates are
restricted to a lower value than desired on the ASR5000 /ASR5500 platforms. The IMSI Manager receives
new session requests from the Link Manager (3G) and Gb Manager (2G) processes in the SGSN. It also
receives messages from the MME Manager (12 instances) processes in the MME. The IMSI Manager task
communicates with a maximum of "288" Session Manager instances in a fully loaded chassis on ASR5000.
On DPC2 the numbers of Session Manager Instances are much more than on ASR5000, therefore one instance
of IMSI Manager will not be sufficient to support the number of Session Manager Instances on ASR5500 and
VPC-DI platforms. Scaling up the number of IMSI Manager Instances improves the single event performance
numbers of SGSN and MME. It also helps in utilizing the full capability of the ASR 5500 and VPC-DI
platforms.
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How it Works
How it Works
Detailed Description
The LINKMGR, GBMGR and the MMEMGR select an IMSIMGR instance that needs to be contacted for
session setup. Each subscriber session in the Session Manager maintains the IMSIMGR instance number that
"hosts" the mapping for this IMSI. This information is required while communicating during audit and session
recovery scenarios.
When a single IMSI manager instance is present, there is only one centralized entry point for new calls into
the system. Network overload protection is configured using the command "network-overload-protection",
new call acceptance rates are configured and controlled using this command. Once the configured rate is
reached the new calls are dropped. When there are multiple IMSI manager instances, the configured new call
acceptance rate is distributed equally across all IMSI Manager instances to throttle new calls.
The IMSI manager manages target (NRI and count) based offloading. Though number of IMSI Manager
instances is increased, only the first IMSI Manager instance is allowed to perform the target based offloading.
It keeps track of the total offloaded subscribers for every Target-NRI from all Session Managers and notifies
all the Session Managers on attaining Target-count for that Target-NRI.
Several race handling scenarios like ISRAU-Attach collision scenario, Inter-MME TAU attach (FGUTI) on
attach (IMSI) collision scenario and so on can occur, specific measures have been taken to ensure these race
handling scenarios are handled correctly in a multiple IMSI Manager instance scenario.
The control plane messaging throughput on the ASR5500 platform is increased, therefore Performance
degradation or congestion is not observed during multiple IMSI Manager instance recovery after a crash or
an unplanned card migration. Also mechanisms are devised to ensure there is no impact on Session Manager
recovery and Session Manager Thresholding.
The Monitor subscriber next-call option is used to trace the next incoming call into the system. With multiple
IMSI Manager instances, the Session Controller now sends the next-call details to IMSI manager instance 1.
So the next incoming call through IMSI manager instance "1" is monitored.
The IMSI managers are updated with information on critical parameters that lead to congestion control. The
IMSI managers have to inform the congestion status to all Link Managers and Gb Managers. In order to avoid
multiple IMSI managers sending information to all Link Managers and Gb Managers, only the first IMSI
Manager instance informs the congestion status to all Link Managers and Gb Managers. Also only the first
IMSI Manager instance sends the traps indicating congestion status this reduces the number of traps to be
sent.
From this release onwards, the Diameter Proxy Server queries the IMSI Manager instances to obtain
IMSI/IMEI/MSISDN to Session manager instance mapping information.
Relationships to Other Features
Many SGSN and MME features are based on the assumption that there is only one IMSI Manager and there
is only one centralized entry point to the system, this assumption now no longer holds good with multiple
IMSI manager instances. Workarounds have been arrived at to ensure there are no changes observed during
such scenarios. Examples of such scenarios are listed below:
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Configuring Support for Multiple IMSI Managers
• MME per service session limit: The per MME service session limits are enforced by each IMSI manager
instance. The per service session limit is configured by the command bind s1-mme max-subscribers
number.
• MME traps generated by IMSI Manager: Each IMSI Manager instance generates traps for new call
allowed/disallowed independently. The trap information includes the IMSI Manager instance information
Configuring Support for Multiple IMSI Managers
The following configuration command is used to configure the number of IMSIMGR tasks that are required
in the system:
config
task facility imsimgr { avoid-sessmgr-broadcast | max integer_value | required-sessmgr no_sess_mgrs
| sessmgr-sessions-threshold high-watermark high_value low-watermark low_value }
end
Notes:
• The keyword max denotes the number of IMSI managers spawned in the system. This keyword is
supported only on ASR5500 and VPC-DI platforms. A maximum of "4" IMSI Manager can be configured.
• The default number of IMSI Managers supported is "4" on ASR5500 and VPC-DI platforms.
• This is a boot-time configuration and should be added in the configuration file before any SGSN/MME
related configuration is created or any IMSI Manager is started. Run-time configuration of this CLI is
not valid. Any such attempt will result in the following error message being displayed:
New config requires system restart to be effective. Please save config and restart
• This configuration should be added in the configuration file and the system should be re-loaded to apply
this new configuration.
The sgsn imsimgr command in the Exec mode initiates audit for managing the SGSN's IMSI manager's
(IMSIMgr) IMSI table. The command is updated with a new keyword instance to extend support for multiple
IMSI Managers. The audit is initiated from only one specified instance of IMSI Manager at a time.
sgsn imsimgr { instance instance_id }{ add-record imsi sessmgr instance sessmgr | audit-with sessmgr
{ all | instance sessmgr } | remove-record imsi }
Verifying the Configuration
The feature configuration can be verified by executing the show configuration command, the number IMSI
Managers configured is displayed:
• task facility imsimgr max 4
Monitoring and Troubleshooting the Multiple IMSI Manager
Support
This section provides information on the show commands available to support this feature.
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Multiple IMSI Managers Show Command(s) and/or Outputs
Multiple IMSI Managers Show Command(s) and/or Outputs
show linkmgr all
The following new parameters are added to this show command to display the statistics for this feature:
• IMSIMGR Selection counters
• IMSIMGR 1
• IMSIMGR 2
• IMSIMGR 3
• IMSIMGR 4
show linkmgr instance parser statistics all
The following new parameters are added to this show command to display the statistics for this feature:
• Messenger Counters
• IMSIMGR Selection counters
• IMSIMGR 1
• IMSIMGR 2
• IMSIMGR 3
• IMSIMGR 4
show gbmgr instance parser statistics all
The following new parameters are added to this show command to display the statistics for this feature:
• Messenger Counters
• IMSIMGR Selection counters
• IMSIMGR 1
• IMSIMGR 2
• IMSIMGR 3
• IMSIMGR 4
show demuxmgr statistics imsimgr verbose
The following new parameter is added to this show command to display the statistics for this feature:
• IMSIMGR instance number
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Multiple IMSI Managers Show Command(s) and/or Outputs
show demux-mgr statistics sgtpcmgr instance < id >
The following new parameters are added to this show command to display the statistics for this feature:
• Interactions with IMSI Manager
• Num requests sent to IMSIMgr
• Num requests not sent to IMSIMgr
• Num requests bounced from IMSIMgr
• Num responses received from IMSIMgr
• Num responses with unknown IMSI
• Num Forwarded Relocation Request forwarded
• Num Relocation Cancel Requests With IMSI forwarded
• Num Forward Relocation Requests rejected by IMSIMGR
• Num Relocation Cancel Requests rejected by IMSIMGR
show session subsystem facility mmemgr instance < id >
New counters are added in the MME manager to count the number of requests sent towards the IMSI managers:
• IMSIMGR Selection counters
• IMSIMGR 1
• IMSIMGR 2
• IMSIMGR 3
• IMSIMGR 4
show subscribers mme-only full all/ show mme-service session full all
The IMSI Manager instance holding the mapping entry for a subscriber session is displayed as part of the
subscriber session information:
• Imsimgr Instance
show mme-service db record call-id <id>
The following new parameters are added to this show command to display the statistics for this feature:
• Sessmgr Instance
• Imsimgr Instance
• MME Service
• Lookup Keys
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Multiple IMSI Managers Show Command(s) and/or Outputs
• IMSI
• Service-id
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40
SGSN Support for Peer-Server Blocking
This chapter describes SGSN support for Peer-Server Blocking.
• Feature Description, page 541
• How it Works, page 542
• Configuring Peer-Server Blocking , page 544
• Monitoring and Troubleshooting the Peer-Server Blocking , page 544
Feature Description
The validity of SCTP redundancy has to be tested by simulating fail overs when new RNCs/STPs have to be
commissioned. Peer-Server Blocking support has been added to prevent any issues during commissioning of
new RNCs/STPs.
The Peer Server Blocking feature provides the following functionalities:
1 The SCTP association can be either brought up or down in order to test the redundancy of the same.
2 The PSPs can be brought down without removing the configuration.
3 The SGSN supports a new configuration command under the psp-instance to block/unblock peer endpoint
and this configuration is pushed to the Link Manager to achieve peer-server blocking.
4 The SGSN sends a SCTP Shutdown to the remote endpoint and marks the endpoint as LOCKED when
the PSP is configured as blocked and if the PSP is in ESTABLISHED state.
5 The SGSN initiates a SCTP INIT when a blocked PSP is un-blocked and if the SGSN is a client and is
asp-associated.
6 The SGSN replies with an ABORT when the peer sends INIT in LOCKED state.
7 The SGSN marks the remote endpoint as LOCKED when the PSP is configured as blocked and if the PSP
is in a CLOSED state.
8 The PSP state is recovered if the Link Manager expires and no messages are initiated after recovery if the
PSP is in locked state.
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How it Works
How it Works
The SCTP associations are between PSPs and ASPs. The control to bring down a SCTP association is added
at the PSP level. The option for shutdown/no shutdown is added under each PSP configuration. This
information is stored in SCT and is forwarded to the Session Controller. The Session Controller sends this
configuration request to the Master Link Manager via a messenger call. The Link Manager receives the
configuration from the Master Manager. Based on the current association state and the CLI (shutdown/no
shutdown) issued the following actions are taken:
1 If the CLI shutdown is issued, the shutdown flag is set. When the association is in an ESTABLISHED
state, the Link Manager initiates a SCTP SHUTDOWN towards the peer and moves to the LOCKED state
after shutdown procedure is completed.
2 If the CLI no shutdown is issued, the shutdown flag is not set and this serves as a trigger to INIT towards
the peer, provided the PSP is already in LOCKED state and SGSN is configured as client. A SCTP INIT
is triggered towards the peer. If the association is in any state other than LOCKED state, the configuration
is ignored.
The following table provides information on various Peer Server blocking scenarios based on the CLI
configuration:
CLI configuration
Current Association
State
shutdown
LOCKED
shutdown
CLOSED
shutdown
COOKIE-WAIT
shutdown
COOKIE-ECHOED
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SGSN Action
Result Association State
1 No action taken.
2 Association remains in
LOCKED state.
1 Association is marked
as LOCKED.
2 SCTP Abort is sent on
receiving Init from
peer, and the Init is
dropped.
1 Association is marked
as LOCKED.
2 SCTP Abort is sent for
every subsequent Init
from peer.
1 Association is marked
as LOCKED.
2 SCTP Abort is sent on
receiving Init from
peer and the Init is
dropped.
LOCKED
LOCKED
LOCKED
SGSN Support for Peer-Server Blocking
How it Works
CLI configuration
Current Association
State
SGSN Action
shutdown
ESTABLISHED
shutdown
SHUTDOWN-PENDING Once the SCTP shutdown LOCKED
procedure is completed
SHUTDOWN-SENT
the association is moved
SHUTDOWN-RECEIVED to the LOCKED state.
SHUTDOWN-ACK
SENT
no shutdown
LOCKED
If SGSN is the client, an
INIT is initiated and the
association is moved to
COOKIE-WAIT state. If
SGSN is the server the
association is moved to
CLOSED state
COOKIE-WAIT (on
triggering
INIT)/CLOSED
no shutdown
CLOSED
No action required.
No change in state
1 SCTP SHUTDOWN
is initiated
2 The association is
moved to the
LOCKED state after
SCTP shutdown
procedure is complete
Result Association State
LOCKED
COOKIE-WAIT
COOKIE-ECHOED
ESTABLISHED
no shutdown
SHUTDOWN-PENDING No action required, an
No change in state
Error
is
displayed
until
the
SHUTDOWN-SENT
shutdown procedure
SHUTDOWN-RECEIVED completed and PSP is
moved to either LOCKED
SHUTDOWN-ACK
state (if the shutdown
SENT
procedure is due to a
previous "shutdown" on
PSP) or CLOSED state (if
the shutdown is due to
some other reason).
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Configuring Peer-Server Blocking
Configuring Peer-Server Blocking
The following command is used to configure the Peer-Server Blocking feature:
config
ss7-routing-domain routing_domain_id variant variant_type
peer-server id id
psp instance psp_instance
[no] shutdown
exit
Notes:
• On configuring shutdown, the PSP is brought down via a SCTP Shutdown procedure (if association is
already ESTABLISHED) or Abort (any other association state) and it is marked LOCKED. The SGSN
does not initiate any messages towards the peer and any message from the peer will be responded with
a SCTP Abort, when the PSP is in a LOCKED state.
• On configuring no shutdown, the PSP is marked unlocked and the SGSN initiates an association
establishment towards the peer. This is the default configuration for a PSP. The default is no shutdown.
Listed below are the error codes added to support the Peer-Server blocking feature:
• Once the CLI is configured if the operator tries to re-configure the same CLI again, a CLI failure is
displayed. This suppresses the Link Manager error logs while trying to push same configuration twice.
The error code displayed is:
Failure: PSP: Re-configuring same value
• During an ongoing shutdown procedure if the command no shutdown is executed, the execution of the
command will be unsuccessful and a CLI failure error message is displayed.
The error code displayed is:
Cannot unlock PSP during ongoing shutdown procedure
This ensures that the shutdown procedure is graceful. The command no shutdown can be configured
only when there is no ongoing shutdown procedure.
Verifying the Peer-Server Blocking Configuration
Use the following show command to verify the Peer-Server Blocking configuration:
show ss7-routing-domain num sctp asp instance num status peer-server id num peer-server-process
instance num
The field Association State is displayed as LOCKED when the PSP is locked via the shutdown CLI.
Monitoring and Troubleshooting the Peer-Server Blocking
The following traps are generated on locking a PSP via shutdown CLI:
• SCTPAssociationFail
• M3UAPSPDown
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Monitoring and Troubleshooting the Peer-Server Blocking
• SS7PCUnavailable
• M3UAPSDown
The trap M3UAPSPDown additionally indicates the cause, the cause value indicated is
Administrative-Shutdown.
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Monitoring and Troubleshooting the Peer-Server Blocking
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CHAPTER
41
Support for EPC QoS Attributes on SGSN
• Feature Description, page 547
• How It Works, page 548
• Configuring EPC QoS Support on SGSN, page 549
• Monitoring and Troubleshooting EPC QoS Support on SGSN, page 551
• Troubleshooting EPC QoS Support on SGSN, page 551
Feature Description
The Gn-Gp SGSN now supports EPC QoS parameters during PDP Activation/Modification procedures.
Support is added for Evolved-ARP, APN-AMBR and UE-AMBR QoS parameters. The purpose of adding
this support is to achieve end to end synchronization of QoS parameters during IRAT (3G/4G) mobility
procedures. In previous releases it was observed that there is no synchronization between QoS parameters
during TAU/RAU mobility from a 4G scenario to a 3G scenario or vice versa.
Overview
The EPC QoS attributes now supported Gn SGSN can be briefly described as below:
Evolved-ARP (E-ARP): Evolved allocation or retention priority specifies the relative importance of a Radio
Access Bearers as compared to other Radio Access Bearers for allocation or retention of the Radio access
bearer. The EPC uses Evolved ARP, which has priority level ranging from "1" up to "15". Additionally,
evolved ARP comprises of pre-emption capability and pre-emption vulnerability. The preemption capability
information defines whether a bearer with a lower priority level should be dropped to free up the required
resources. The pre-emption vulnerability information indicates whether a bearer is applicable for such dropping
by a preemption capable bearer with a higher priority value.
APN-AMBR (per APN Aggregate Maximum Bit Rate): The APN-AMBR limits the aggregate bit rate that
can be provided across all Non- GBR PDP contexts of the same APN (for example, excess traffic may get
discarded by a rate shaping function). Each of those Non-GBR PDP contexts can potentially utilize the entire
APN AMBR (for example, when the other Non- GBR PDP contexts do not carry any traffic). The PGW
enforces the APN AMBR in downlink. Enforcement of APN AMBR in uplink may be done in the UE and
additionally in the PGW.
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How It Works
UE-AMBR: The UE AMBR limits the aggregate bit rate that can be provided across all Non-GBR PDP
contexts of a UE (for example, excess traffic may get discarded by a rate shaping function). Each of the
Non-GBR PDP contexts can potentially use the entire UE AMBR (for example, when the other Non-GBR
PDP contexts do not carry any traffic). The GBR (real-time) PDP contexts are outside the scope of UE AMBR.
The RAN enforces the UE AMBR in uplink and downlink.
With this feature enhancement the SGSN now supports the following functionalities:
1 EPC QoS parameters for Gn/Gp interface activated PDPs are supported.
2 The Gn-Gp SGSN reads the EPC QoS parameters from the HLR/HSS and the user.
3 The Gn-Gp SGSN now performs capping of the QoS parameters and sends the negotiated values towards
the GGSN and RAN.
How It Works
During PDP context activation/modification, Inbound ISRAU/SRNS and Standalone ISDs the SGSN sends
negotiated E-ARP and APN-AMBR values to the GGSN. The SGSN reads the Subscribed QoS values from
the HSS/HLR and from the user (configured through the CLI commands), based on the QOS capping configured
the SGSN caps the QoS values.
The QoS profile configuration mode is used to configure the APN-AMBR values; this mode is now enhanced
to configure E-ARP values. The QoS-profile is associated to APN profile which is selected based on the APN
name, the QoS profile now contains locally configured E-ARP and APN-AMBR values. The command
prefer-as-cap is configured to instruct either to take values from HLR/HSS or local configuration or the
minimum of these two.
If the APN profile is not configured, E-ARP and APN-AMBR values are same as the subscribed values
provided by the HSS/HLR. If E-ARP and APN-AMBR values are locally configured in the QoS profile,
subscribed E-ARP and APN-AMBR values are overridden with locally configured values. This enforcement
is done for all contexts which are activated in the SGSN for the first time or during Inter SGSN RAU when
the user shifts from other SGSNs to our SGSN or during context activation when a user switches from 2G to
3G or vice versa.
The SGSN calculates the authorized UE-AMBR equal to the sum of all the APN-AMBRs. If the calculated
UE-AMBR is greater than subscribed value it is capped to subscribed value.
The SGSN sends the negotiated E-ARP and APN-AMBR values in the following GTPV1 messages to the
GGSN during PDP activation/modification or when subscription is received with new values of E-ARP and
APN-AMBR:
• Create PDP Context Request.
• Update PDP Context Request
• Update PDP Context Response
The SGSN receives the E-ARP and APN-AMBR in the following GTPV1 messages from the GGSN during
PDP activation/modification:
• Create PDP Context Response.
• Update PDP Context Response
• Update PDP Context Request
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Standards Compliance
If the GGSN replies with changed values of E-ARP and APN-AMBR then the downgraded values will be
accepted immediately, but upgraded values are accepted only if the allow upgrade option is configured through
the CLI.
The following CLI under the Call Control Profile is configured to allow upgrade of E-ARP:
override-arp-with-ggsn-arp
If the GGSN replies with changed values of APN-AMBR then the upgrade and downgrade values are accepted
unconditionally.
The SGSN sends negotiated E-ARP, UE-AMBR , APN-AMBR in the following GTPV1 messages to the peer
SGSN/MME during Inter- SGSN RAU and SRNS procedures:
• SGSN Context Response.
• Forward Relocation Request
The SGSN sends E-ARP and UE-AMBR in the following RANAP messages to RNC during RABs
establishment and modification procedures:
• RAB assignment Request.
• RAB Modification Request
Standards Compliance
This feature complies with the following 3GPP standards:
• 3GPP TS 29.060 (version 12.0.0)
• 3GPP TS 25.413 (version 12.0.0)
Configuring EPC QoS Support on SGSN
The following commands are used to configure EPC QoS Support on Gn SGSN:
Configuring QoS Profile to Support EPS QoS Parameters in GTPv1 messages
The following new command has been introduced in the QoS Profile configuration mode to enable or disable
the SGSN to send EPC QoS parameters to GGSN:
config
quality-of-service-profile profile_name
[remove] epc-qos-params-in-gtpv1 { eps-subscription | gprs-subscription }
exit
Notes:
• This command is disabled by default.
• On enabling this command E-ARP and APN-AMBR parameters are included in the GTPV1 SM messages
towards the GGSN
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Configure E-ARP values in the Quality of Service Profile
• If the keyword eps-subscription is configured, the EPC QoS parameters from EPS subscription are sent
to the GGSN. (Note: This option is not supported in this release)
• If the keyword gprs-subscription is configured, E-ARP and APN-AMBR from the GPRS subscription
are sent. The UE-AMBR value is read from the user (local capping).
Configure E-ARP values in the Quality of Service Profile
A new keyword is introduced in the class command under the QoS profile configuration mode to configure
the E-ARP values.
config
[remove] class { background | conversational | interactive | streaming } evolved-arp {
preemption-capability capability_value | preemption-vulnerability vulnerability_value | priority-level
level_value }
exit
Notes:
• This command is disabled by default.
• Use the keyword preemption-capability to configure the preemption capability value. The value is
configured as "0" or "1".
• Use the keyword preemption-vulnerability to configure the preemption capability value. The value is
configured as "0" or "1".
• Use the keyword priority-level to configure the priority level of the E-ARP. The priority can be
configured as any value in the range "1" up to "15".
Configure Local Capping in the Quality of Service Profile
The existing command prefer-as-cap is used to instruct the SGSN to use either the local or subscription or
both-subscription-and-local (lower of either the locally configured QoS bit rate or the subscription received
from HLR/HSS) QoS configuration value as the capping value for the QoS parameters.
config
quality-of-service-profile profile_name
prefer-as-cap [ both-subscription-and-local | subscription | local ]
exit
Configure Override of E-ARP Values Provided by GGSN
The existing command [remove] override-arp-with-ggsn-arp under the Call Control Profile is used to enable
or disable the ability of the SGSN to override an Allocation/Retention Priority (ARP) value with one received
from a GGSN. If there is no authorized Evolved ARP received from the GGSN, by default the SGSN continues
to use the legacy ARP included in the Quality of Service (QoS) Profile IE.
config
call-control-profile profile_name
[remove] override-arp-with-ggsn-arp
exit
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Verifying the Configuration
Verifying the Configuration
The configuration can be verified by executing the show command show quality-of-service-profile full all.
The following parameter is displayed if gprs-subscription is selected in the epc-qos-params-in-gtpv1
command:
Sending of epc-qos-params to GGSN : Enabled with GPRS Subs
Monitoring and Troubleshooting EPC QoS Support on SGSN
This section provides information on the show commands available to support this feature.
Show Command(s) and/or Outputs
Listed below are the show outputs and new statistics added for EPC QoS support on SGSN:
show subscriber sgsn-only full all
The following new statistics are added in the show subscriber sgsn-only full all command:
• Evolved Allocation/Retention Priority
• Priority level
• Pre-emption Vulnerability
• Pre-emption Capability
• AMBR
• Negotiated APN-AMBR UL
• Negotiated APN-AMBR DL
• Max-Requested-Bandwidth-UL
• Max-Requested-Bandwidth-DL
• Applied UE-AMBR DL
Troubleshooting EPC QoS Support on SGSN
This section provides troubleshooting information for some common scenarios which might occur when EPC
QoS parameter support is enabled on the SGSN.
If EPC QoS parameters are not being sent to the GGSN, execute the following troubleshooting procedure:
• Ensure that E-ARP and APN-AMBR values are received in subscription from HLR/HSS.
• Verify if epc-qos-params-in-gtpv1 command is configured in the QoS profile. Execute the command
show quality-of-service-profile full all to verify the configuration.The following statistic is displayed
based on the configuration:
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Troubleshooting EPC QoS Support on SGSN
◦Sending of epc-qos-params to GGSN : Enabled with GPRS Subs
If UE-AMBR is not being sent to the RNC, execute the following troubleshooting procedure:
• Ensure that the UE-AMBR is received in subscription from HLR/HSS.
• Verify if sending of UE-AMBR is configured for the RNC. Execute the show command show iups-service
all to verify the configuration. The following statistic is displayed based on the configuration:
◦UE Aggregate Maximum Bit Rate : IE included in message
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42
Support For QoS Upgrade From GGSN or PCRF
This chapter describes the Support for QoS Upgrade feature.
• Feature Description, page 553
• How it Works, page 553
• Configuring Support for QoS upgrade from GGSN/PCRF, page 555
Feature Description
The SGSN negotiates the Requested QoS with Subscribed QoS from HLR (the HLR Subscribed QoS can be
over-ridden by the local configuration). The SGSN includes this Negotiated QoS in Create PDP Context
Request and Update PDP Context Request messages to the GGSN, the negotiate QoS is capped to the Subscribed
QoS and cannot exceed it. The "Upgrade QoS Supported" flag is not set, and the GGSN cannot negotiate a
QoS higher than that sent by the SGSN.
This feature enables the functionality, where the SGSN can set the "Upgrade QoS Supported" flag within the
common flags IE in Tunnel management messages, Create PDP Context Request and Update PDP Context
Request messages. The SGSN accepts the QoS from GGSN in Create PDP Context Response, Update PDP
Context Request/Response messages as the Negotiated QoS for the PDP session.
In a 3G scenario, if QoS is downgraded by the RNC then SGSN sets the "No QoS negotiation" flag in the
common Flags IE of the corresponding Update PDP Context Request. The "QoS upgrade supported" flag is
not set.
How it Works
A new configuration CLI is provided under the APN Profile configuration mode to support the QoS upgrade
feature. If this CLI is configured, the SGSN sets the "Upgrade QoS Supported" bit in the Common Flags IE
in Create PDP Context Request and Update PDP Context Request. The SGSN accepts the QoS from the
GGSN in Create PDP Context Response, Update PDP Context Request/Response as the Negotiated QoS for
the PDP session.
A detail description of the implementation of the QoS upgrade feature in various 3G scenarios is provided
below:
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How it Works
The "Upgrade QoS Supported" flag in Create PDP Context Request and Response messages
1 During the primary and secondary PDP context activation, if support to send "Upgrade QoS Supported"
flag is configured under the APN-Profile, the SGSN sets the flag while sending the Create PDP Context
Request.
2 The Create PDP Context Response arrives from the GGSN. If the configuration for "Upgrade QoS
Supported" flag is enabled under the APN-Profile, the GGSN requested QoS is handled.
A CLI option is provided to enable or disable the keyword prefer-as-cap subscription. Based on the
configuration of this keyword, the following QoS processing occurs:
• The keyword prefer-as-cap subscription is disabled: The SGSN accepts the QoS in the Create PDP
Context Response as the negotiated QoS. This negotiated QoS can be downgraded by the RNC during
RAB assignment. If the RNC downgrades the QoS then "Upgrade QoS Supported" flag is not set in the
corresponding Update PDP Context Request message.
• The keyword prefer-as-cap subscription is enabled: The SGSN negotiates the QoS received in the
Create PDP Context Response with the Subscribed QoS. After negotiation if the QoS is downgraded,
the "Upgrade QoS Supported" flag not set in the Update PDP Context Request message.
The "Upgrade QoS Supported" flag in Update PDP Context Request and Response messages
If support to send "Upgrade QoS Supported" flag is configured under the APN-Profile and "No QoS negotiation'
flag is not set, the SGSN sets the "Upgrade QoS Supported" flag while sending the Update PDP Context
Request. The "Upgrade QoS Supported" flag is not set in every Update PDP Context Request, for example,
in preservation and direct tunnel this flag is not set in Update PDP Context Request message. The relationship
between the "No QoS negotiation" flag and the "Upgrade QoS Supported" flags in Update PDP Context
Request messages is summarized as:
• If "No QoS negotiation" flag is set, the "Upgrade QoS Supported" flag is not set.
• If "No QoS negotiation" flag is not set, the "Upgrade QoS Supported" flag is set.
A CLI option is provided to enable or disable the keyword prefer-as-cap subscription. Based on the
configuration of this keyword, the following QoS processing occurs:
• The keyword prefer-as-cap subscription is disabled: The SGSN accepts the QoS in the Create PDP
Context Response as the Negotiated QoS. This Negotiated QoS can be downgraded by the RNC during
RAB assignment. If the RNC downgrades the QoS then "Upgrade QoS Supported" flag is not set in the
corresponding Update PDP Context Request message.
• The keyword prefer-as-cap subscription is enabled: The SGSN negotiates the QoS received in the
Create PDP Context Response with the Subscribed QoS. After negotiation if the QoS is downgraded,
the "Upgrade QoS Supported" flag not set in the Update PDP Context Request message.
A detail description of the implementation of the QoS upgrade feature in various 2G scenarios is provided
below:
The "Upgrade QoS Supported" flag for Create PDP Context Request and Response
1 During the primary and secondary PDP context activation, if support to send "Upgrade QoS Supported"
flag is configured under the APN-Profile, the SGSN sets the flag while sending the Create PDP Context
Request.
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Configuring Support for QoS upgrade from GGSN/PCRF
2 The Create PDP Context Response arrives from the GGSN. If the configuration for "Upgrade QoS
Supported" flag is enabled under the APN-Profile, the GGSN requested QoS is handled.
A CLI option is provided to enable or disable the keyword prefer-as-cap subscription. Based on the
configuration of this keyword, the following QoS processing occurs:
• The keyword prefer-as-cap subscription is disabled: The SGSN accepts the QoS in the Create PDP
Context Response as the Negotiated QoS. In an ideal 2G scenario where all the parameters are configured
appropriately at the GGSN/PCRF, an upgrade beyond "472" kbps does not occur. If the GGSN sends
QoS greater than "472" kbps, this requested bitrate is capped to "472" kbps.
• The keyword prefer-as-cap subscription is enabled: The SGSN negotiates the QoS received in the
Create PDP Context Response with the Subscribed QoS. After negotiation if the QoS is downgraded,
the "Upgrade QoS Supported" flag not set in the Update PDP Context Request message.
The "Upgrade QoS Supported" flag for Update PDP Context Request and Response
If support to send "Upgrade QoS Supported" flag is configured under the APN-Profile and "No QoS negotiation'
flag is not set, the SGSN sets the "Upgrade QoS Supported" flag while sending the Update PDP Context
Request. The "Upgrade QoS Supported" flag is not set in every Update PDP Context Request, for example,
in preservation and direct tunnel this flag is not set in Update PDP Context Request message. The relationship
between the "No QoS negotiation" flag and the "Upgrade QoS Supported" flags in Update PDP Context
Request messages is summarized as:
• If "No QoS negotiation" flag is set, the "Upgrade QoS Supported" flag is not set.
• If "No QoS negotiation" flag is not set, the "Upgrade QoS Supported" flag is set.
A CLI option is provided to enable or disable the keyword prefer-as-cap subscription. Based on the
configuration of this keyword, the following QoS processing occurs:
• The keyword prefer-as-cap subscription is disabled: The SGSN accepts the QoS in the Create PDP
Context Response as the Negotiated QoS. This Negotiated QoS can be downgraded by the RNC during
RAB assignment. If the RNC downgrades the QoS then "Upgrade QoS Supported" flag is not set in the
corresponding Update PDP Context Request message.
• The keyword prefer-as-cap subscription is enabled: The SGSN negotiates the QoS received in the
Create PDP Context Response with the Subscribed QoS. After negotiation if the QoS is downgraded,
the "Upgrade QoS Supported" flag not set in the Update PDP Context Request message.
Configuring Support for QoS upgrade from GGSN/PCRF
The following command is used to configure the support for QoS upgrade from GGSN/PCRF:
config
apn-profile profile_name
qos allow-upgrade access-type { gprs | umts }[ prefer-as-cap subscription ]
remove qos allow-upgrade access-type { gprs | umts }
end
Notes:
• The "Upgrade QoS Supported" flag is now set in "Create PDP Context" and "Update PDP Context"
messages sent by SGSN. The SGSN signals the availability of this functionality by use of the "Upgrade
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Verifying the QoS Upgrade Support Configuration
QoS Supported" bit within the Common Flags IE. The SGSN sets the "Upgrade QoS Supported" bit
within the Common Flags IE to "1" within the "Create PDP Context" and "Update PDP Context"
• If keyword prefer-as-cap subscription is enabled, SGSN accepts a higher QoS in the Create/Update
PDP Context Response than sent in Create/Update PDP Context Request, but negotiates and restricts
the value within HLR/local subscribed QoS. If this keyword is disabled, the SGSN accepts the QoS in
Create PDP Context Response and Update PDP Context Response as the Negotiated QoS (this QoS may
be downgraded by the RNC in case of UMTS access).
For more information on the command, see Command Line Interface Reference.
Verifying the QoS Upgrade Support Configuration
The configuration can be verified by executing the show command show apn-profile full name
<apn_profile_name>. The following parameters are displayed on executing the command:
1 Allow QoS Upgrade from GGSN
2 QoS Upgrade From GGSN (UMTS)
3 Capped with Subscribed QoS
4 QoS Upgrade From GGSN (GPRS)
5 Capped with Subscribed QoS
For description of the fields listed above see, Statistics and Counters Reference.
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CHAPTER
43
Support for SGSN QoS based on PLMN, RAT Type
This chapter describes the Support for SGSN QoS based on PLMN, RAT type.
• Feature Description, page 557
• How it Works, page 557
• Configuring SGSN Support for RAT Type based QoS Selection , page 558
• Monitoring and Troubleshooting RAT Type Based QoS Selection, page 559
Feature Description
SGSN support for QoS selection based on RAT type is introduced through this feature, this functionality
improves the Operator Policy based QoS Control capabilities. Currently, the SGSN supports only PLMN
based QoS selection. The Operator policy on SGSN allows the operators to control QoS for visiting subscribers
(National or International roaming-in subscribers or MVNO subscribers) on an APN basis depending on the
PLMN-ID or IMSI range. APN profiles are configured under the Operator Policy as either default for all APN
or specific profiles for particular APN.
The following limitations are encountered when only PLMN based QoS selection is supported:
1 When co-locating MME and SGSN into the same node, separate Operator Policy can be configured for
E-UTRAN on the MME and both GERAN/UTRAN on the SGSN but not for GERAN and UTRAN
separately on the SGSN.
2 The Operator policy currently allows to 'allow' or 'restrict' access to the network based on zone-code (set
of LA/SA for 2G/3G and TA for LTE) but does not allow restricting the QoS in specific area of the network
based on zone-code.
To overcome the limitations listed above, Operator Policy based QoS Control capabilities are introduced
based on RAT-Type or a combination of RAT-Type with PLMN-ID or IMSI range.
How it Works
With the introduction of QoS selection based on RAT type, several QoS profiles can now be configured and
associated with the APN profile with the access type marked as either GPRS or UMTS.
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Configuring SGSN Support for RAT Type based QoS Selection
Listed below are the SGSN functions now supported for QoS selection:
1 Configuration of QoS based on RAT type
2 Configuration of QoS based on PLMN, this configuration automatically happens as the Operator policy
is PLMN based. The QoS Profile is configured on RAT basis.
3 SGSN provides support for configuring APN-AMBR and UE-AMBR per RAT Type.
The SGSN supports configuring all the R99 QoS parameter under the APN profile except for Traffic class.
It also supports configuring the R97 QoS parameters namely Delay Class, Reliability class, Peak throughput,
Precedence class and Mean Throughput. This configuration is used to over-ride the HLR provided Subscribed
QoS value or the configured values are used in combination with subscribed values.
QoS capping has to be performed at various levels like the RAT-Type and PLMN. To achieve QoS capping
at different levels, the QoS parameters under the APN profile are also made available under a new profile
called the "QoS-profile". The QoS-profile also provides support for over-riding the R97 QoS parameters,
Traffic class, UE-AMBR and the APN-AMBR (UE-AMBR and APN-AMBR applicable only for S4-SGSN).
This feature enhancement supports backward compatibility.
The QoS Profile can be associated with the APN profile, for each access-type independently or as common
to profile.
At the APN profile level, if QoS parameters (R99 parameters except traffic class) as well as a QoS profile are
configured, then the QoS profile takes precedence over the QoS parameters.
QoS parameters in QoS profile and APN profile are identical. The new QoS profile provides the modular
approach in configuring QoS parameters and associate it to APN Profile per RAT Type.
QoS profile also provides an additional configuration (when compared to apn-profile) named "prefer-tc". This
configuration allows the operator to override the Traffic class received in Subscription. "prefer-tc" works
closely with "prefer-as-cap" configuration; either:
1 If "prefer-as-cap" is set to both subscription and local then SGSN will negotiate the traffic class configured
to traffic class subscribed. Further QoS parameters under this traffic class will be negotiated.
2 If "prefer-as-cap" is set to local then QoS parameters under local configuration will be negotiated with
requested for QoS capping.
If operator configures "prefer-tc" then he is expected to configure all the QoS parameters of all traffic class
under QoS profile.
Configuring SGSN Support for RAT Type based QoS Selection
This section provides information on configuring SGSN support for QoS selection based on PLMN, RAT
Type. The following commands have to be configured to enable RAT type based QoS selection:
Configuring APN Profile and QoS Profile Association
Use the following command to associate an APN profile with a QoS profile:
config
apn-profile profile_name
associate quality-of-service-profile profile_name access-type [ gprs | umts ]
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Configuring the Quality of Service Profile
remove associate quality-of-service-profile profile_name access-type [ gprs | umts ]
exit
Notes:
This command is used to associate the specified Quality of Service profile with the APN profile. The access-type
must be configured as either gprs or umts.
Configuring the Quality of Service Profile
Use the following commands under the new CLI configuration mode "Quality of Service Profile" to configure
the QoS parameters:
config
quality-of-service-profile