Extract from Wholesale NGN Ethernet Technical Handbook

Extract from Wholesale NGN Ethernet Technical Handbook
Extract from Wholesale NGN Ethernet Technical Handbook
The below text is the proposed additions to the Wholesale NGN Ethernet Technical handbook.
2.3
Bitstream Ethernet Connectivity Service
eircom
NGN
Operator Site
IES
7750PE
eircom
NTU
7450ESS
WEIL (EIL)
NGN BECS Bitstream (NBB)
NGN BECS Bitstream Managed Backhaul (NBM)
Figure 1: NGN BECS
The eircom Wholesale NGN BECS service consists of the following components:
1. Wholesale Ethernet Interconnect Link (EIL) provides (physical) connectivity from an Operator’s
handover site to the 7450ESS.
2. Logical connection providing handover of ADSL Bitstream L2TP traffic from ADSL DSLAMs to an
Operator’s IP network. Two options are available for the logical connection:
a. NGN BECS Bitstream logical connection (NBB)
b. NGN BECS Bitstream Managed Backhaul logical connection (NBM)
For purposes of clarity, NGN BECS is a layer 3 service and will be available on all EIL types (e.g. ISH,
IBH, CSH and ENH) and whether the EIL is configured as a port or a lag.
3.3
Bitstream Ethernet Connectivity Service
The Bitstream Ethernet Connectivity Service (BECS) is used for handing over standard (NGB and
Legacy) Wholesale Bitstream traffic to an Operator using L2TP. BECS is not used for hand-over of the
Bitstream Ethernet Access (BEA) service which is described in this document.
For simplicity, the description is based on an NTU being deployed on the EIL connection. However, as
described in the previous sections it is possible to have an EIL connection with no NTU.
3
2
1
4
5
6
Bitstream Traffic
Modem
Modem
ADSL
ADSL
ADSL
Operator
Handover Site
DSLAM
DSLAM
BRAS
eircom
Aggregation
Network
Modem
DSLAM
Operator
Network
(LNS)
L2TP Tunnels
BRAS
eircom NGN
Node
BRAS
eircom
IP Core
eircom
NTU
E-NNI
1G/10G
Optical/Electrical Port
Figure 2: NGN BECS Traffic Flow
The following describes how End User traffic is treated for the NGN BECS service:
1. The Operator’s customers connect to an eircom ADSL line with PPPoE credentials on the ADSL
modem set according to the Operator’s requirements (e.g. username@OAO1.ie, password)
2. The Bitstream traffic is forwarded from the eircom DSL Access Multiplexer (DSLAM) to the
eircom BRAS nodes. First stage End User authentication is performed on the eircom BRAS based
on the realm associated with the Operator (e.g. @OAO1.ie).
3. An L2TP tunnel is established between the eircom BRAS (LAC) and the Operator BRAS (LNS)
based on the RADIUS profile associated with the realm. The L2TP traffic is routed over the
eircom IP core to the BECS handover site.
4. At the BECS handoff an S-VLAN is added to the traffic and the appropriate service policy (e.g. CoS
profile/bandwidth) is applied. All of the L2TP traffic for a particular NBB or NBM connection is
presented on this S-VLAN.
5. The BECS traffic is passed to the eircom managed NTU located at the Operator’s handover site.
The S-VLAN on the network-facing port is mapped to the Operator facing port on the NTU (E-NNI
port). The E-NNI port is configured as an 802.1ad port. The S-VLAN ID is assigned by eircom and
is used to identify the end user traffic associated with an individual NBB or NBM connection. The
Operator can optionally specify the S-VLAN ID presented at the E-NNI.
6. BECS traffic is handed off to the Operator’s IP network where it is routed to the Operator’s LNS
to terminate the L2TP tunnels and perform second stage authentication for the end users PPP
session.
The BECS product supports the hand-off of ‘legacy’ Bitstream (NBB) and Bitstream Managed
Backhaul (NBM) traffic types on the same physical BECS connection. The handoff of both types of
traffic is on separate S-VLANs.
eircom
NGN
SAP
Individual
WES
Logical
Connections
SAP
E-NNI
SAP
Bitstream
NGN BECS
Connections
BMB
SAP
eircom
NTU
SAP
SABs
7450ESS
Figure 3: Support for BMB and Legacy Bitstream Traffic on EIL
Individual NGN BECS connections are required to carry the ‘Legacy’ Bitstream (NBB) and Bitstream
Managed Backhaul traffic (NBM) on the same EIL. Usage based measurements are required for the
BMB traffic and therefore this traffic cannot be carried in the same service as the ‘Legacy’ Bitstream
traffic.
3.3.1
Layer 3 Redundant Connectivity
In order to offer increased levels of resilience to their End Users, Operators can add further physical
connections to the eircom IP network. In the event of one link failing, the remaining link(s) will carry
the IP traffic. Bitstream traffic is only permitted to flow to and from the Operator over these specific
links.
In summary, the redundant solution will permit the eircom BRAS’s to build multiple L2TP tunnels to
multiple Operator BRAS’s (LNS’s). Individual PPP sessions will be carried in these L2TP tunnels. The
BRAS actually selects the LNS randomly from the list, but where there is a high number of PPP
sessions, the distribution becomes evenly spread across the LNSs.
eircom IP Network
L2TP Tunnels
Operator IP Network
BRAS
NGN BECS
eircom
ADSL
Network
NGN BECS
NGN BECS
L2TP Tunnels
Operator
Edge Router 1
LNS
1
Operator
Edge Router 2
Operator
Edge Router 3
LNS
2
Figure 4: Load-balancing Network Map
When an Operator’s End User enters their username and password, the PPP session causes the
eircom BRAS to lookup one of the eircom DSL RADIUS servers. Based on the domain name entered
by the End User, the eircom RADIUS server will send back the IP addresses of the Operator’s LNS
devices.
The first PPP session to each LNS will cause the eircom BRAS’s to build L2TP tunnels to each of these
IP addresses. Subsequent PPP sessions to each LNS will travel within the existing L2TP tunnel. The
BRAS’s will load-share PPP sessions into the L2TP tunnels.
3.3.2
IP Routing for the Redundant Solution
An eBGP peering is established across each link between eircom and the Operator. The eBGP peering
uses an MD5 password.
Each Operator router advertises the IP addresses of every L2TP tunnel termination point to eircom.
Each eircom edge router only advertises the IP addresses of each required eircom BRAS tunnel
initiation point to the Operator.
Routing of traffic from the Operator to eircom is under the control of the Operator. eircom sets the
MED to 100 for all eircom BRAS prefixes. By setting the MED to the same value for all prefixes, no
link appears ‘closer’ than another.
The use of the BGP MED (Multi-Exit Discriminator) parameter allows individual paths to be preferred
for individual prefixes.
For example, on the first link the Operator could advertise the IP addresses as follows:
A.B.C.D/32 with MED of 10
A.B.C.E/32 with MED of 20
On the second link, the Operator would advertise the IP addresses as follows:
A.B.C.D/32 with MED of 20
A.B.C.E/32 with MED of 10
In normal operation the eircom network will see two possible paths to each individual prefix, and the
path advertising the lower MED will be preferred. In the event of the preferred link failing, the path
with the less preferred higher MED will automatically be selected.
Hence, in normal operation the outbound L2TP tunnel to A.B.C.D will prefer the first link; the
outbound L2TP tunnel to A.B.C.E will prefer the second link.
3.3.3
Operator configuration for BGP

The Operator must use their own public AS number. Private AS numbers are not used.

The Operator (Peer) announces the /32s only for their L2TP LNS (home gateways)

eircom announce /32s only for the BRAS loopbacks.

Peer should not also announce their /32s at INEX as this could cause traffic to go the wrong way
and be blackholed.

eircom will honor the MED values the Operator sends to eircom unless there is an internal traffic
engineering (capacity) requirement for eircom to sent the traffic back a different way.

eircom will announce all of the eircom BRAS /32s with MED 100 so that they appear equidistant.
Peer has control of which peering they send traffic to eircom on. If there are any capacity
management issues this may have to be tweaked in co-operation with eircom to ensure optimum
performance.
4.3
Bitstream Ethernet Connectivity Service
This section summarises the service parameters associated with the eircom Wholesale NGN BECS
service:
Parameter
Value
CoS Offering
All NGN BECS traffic will be
mapped to the Best Effort queue.
Bandwidth Sharing
SAB Bandwidth may be shared
across S-VLANs or dedicated to
each service.
Service Bandwidth
Dedicated bandwidth per S-VLAN
or shared across both (i.e.
bandwidth sharing).
Routing Options
BGP
AS Number
Operator provides their own AS
number
BGP password
Default: Operator provides BGP
password
LNS/HGW Addresses
Operator provides their LNS/HGW
IP addresses (/32s)
Routing Table Options
No Routing table options
supported. eircom advertises all BRAS loopbacks (loopback0 for
Bitstream, loopback2 for BMB)
1620 bytes
MTU size 1
Layer 2 S-VLAN Tagging
Tagged
Layer 2 Access Model
Tagged EPL type access
Service Type Required
A single SAB may support either
Bitstream or BMB services or both
(2 S-VLANs)
S-VLAN allocation
Default:
Assigned by Eircom
Option: Provided by Operator
Table 1: NGN BECS Service Parameters
5.4
Bitstream Ethernet Connectivity Service
The NGN BECS bandwidth options are shown in the following table:
1 Gbit/s EIL
10 Gbit/s EIL
100
100
250
250
500
500
750
750
1000
1000
2000
3000
1
The 1620 byte setting permits a standard customer MTU of 1500 bytes and the associated L2TP
header.
4000
5000
6000
7000
8000
9000
10000
Table 1:
NGN BECS Bandwidth Options (Mbit/s)
As part of the BECS order, the Wholesale Operator will have to specify both the EIL and SAB
reference IDs (and SAB bandwidth) to which the NGN BECS services are associated.
NBM and NBB S-VLANs can be ordered against the same SAB or individual SABs. Refer to section
Error! Reference source not found. for a description of SABs
EIL Service Access Bandwidth 1
eircom
NGN
SAP
Individual
WSEA
Logical
Connections
SAP
E-NNI
SAP
Bitstream
NGN BECS
Connections
BMB
SAP
eircom
NTU
SAP
EIL Service Access Bandwidth 2
7450ESS
EIL Service Access Bandwidth 3
Figure 5: Non-Bandwidth Sharing Model – NGN BECS
In non-bandwidth sharing mode the ‘Legacy’ Bitstream and BMB NGN BECS services are each
associated with their own dedicated SAB.
EIL Service Access Bandwidth 1
eircom
NGN
SAP
Individual
WSEA
Logical
Connections
SAP
E-NNI
SAP
Bitstream
NGN BECS
Connections
BMB
SAP
eircom
NTU
SAP
EIL Service Access Bandwidth 2
7450ESS
Figure 6: Bandwidth Sharing Model – NGN BECS
In bandwidth sharing mode the ‘Legacy’ Bitstream and BMB NGN BECS services are both associated
with the same SAB.
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