Signaling Gateway
VoIP
2002.7.24
한국외국어대학교
정보통신공학과
김희동
031-330-4254
016-9712-0000
[email protected]
2002-7-24
Krnet 2002
1
발표내용









개요
PSTN의 이해(신호망, 지능망)
VoIP관련기술(음성신호처리)
VoIP 표준화 개요
Voice over IP (VoIP) signaling의 개념
VoIP 와 NGN
VoIP 시스템의 구현기술
VoDSL
All IP network (IMT-2000)
2002-7-24
Krnet 2002
2
전화교환망의 개관
2002-7-24
Krnet 2002
3
현재의 회선 교환망
SS7
EO
Toll
Toll
EO
Tan
EO
Tan
EO
Toll
Toll
EO
Tandem/Toll Network
2002-7-24
Krnet 2002
4
교환기의 명칭

Local Switch




Transit Switch





EO (End Office) : 단국
CO (Central Office),
Class 5 Switch
Tandem Switch : 중계교환기
Trunk Switch
Access Tandem
Class 4 Switch
기타 특수교환기


SSP (Service Switching Point)
MSC (Mobile Switching Center) : 이동망의 교환기
2002-7-24
Krnet 2002
5
PSTN(전화망)의 구조
080 SCP
AIN SCP
LNP SCP
PBX
PSTN
STP
Transit
Switch
Local
Switch
VMS
IP
DLC - Digital Loop Carrier
IP - Intelligent Peripheral
PBX - Private Branch Exchange
2002-7-24
Local
Switch
DLC
SCP - Service Control Point
STP - Signal Transfer Point
VMS - Voice Mail System
Krnet 2002
6
신호방식
국간
신호방식
가입자
신호방식
접속요구
발신음
다이얼
점유신호
번호송출허용
호출음
선택신호
응답신호
통
송수화기복구
호출신호
접속점유
화
종화신호
해제요구
절단신호
복구완료
2002-7-24
Krnet 2002
7
가입자 신호방식 Station Signaling

PSTN
Analog 전화기

이용자 선택번호
• Pulse Dial
• DTMF
ISDN
교환기
Dedicated
Network

• Busy tone
• Dial tone
• Ringback tone

Station Signaling
ISDN Terminals





Krnet 2002
BRI(I.430)
LAPD(I.441)
Networking(Q.931)
Digital Telephone

2002-7-24
Call Progress Tone
Voice, Voice+Data
Proprietary Signaling
8
국간신호방식 Trunk Signaling

Signaling

PSTN


Channel Associated
Signaling : R2-MFC
ISDN Signaling : PRI
Common Channel
Signaling : No.7
ISDN
교환기
Dedicated
Network
Trunk
Signaling
2002-7-24
Krnet 2002
9
공중 ISDN과 Signaling System 7
신호망
BRI
PBX1
PRI
BRI
Switch
DSS1

전송망
Transmission
Network
Signaling System 7
Switch
PRI
PBX2
DSS1
신호망의 도입으로



교환기와 교환기 사이의 데이터 경로가 형성됨.
신호망에 컴퓨터를 접속하여, 교환기와 컴퓨터가 상호 연동가능함.
지능망의 개념이 탄생함.
2002-7-24
Krnet 2002
10
SS7 - Protocol View

GSM MAP
INAP
IS-41
ISUP
TUP

TCAP
SCCP
MTP Level 3
MTP Level 2
MTP Level 1






2002-7-24
Krnet 2002
GSM MAP – Global System
for Mobile Communications,
Mobile Application Part
IS-41 – GSM MAP like for NA
wireless systems (AMPS and
TDMA)
INAP – Intelligent Network
Application Part
ISUP – Integrated Services
Digital Network User Part
TUP – Telephony User Part
TCAP – Transaction
Capabilities Application Part
SCCP – Signaling Control
Connection Part
MTP – Message Transfer Part
(Level 1 through 3)
11
SS7 신호망의 요소
SCP
Network 1
SCP
SSP
Network 2
STP
STP
STP
STP
SCP
SCP
SSP
SSP
SSP
SSP: Signal Switching Point
Voice Trunk
Signaling Link STP: Signal Transfer Point
SCP: Service Control Point
2002-7-24
Krnet 2002
12
SS7 ISUP




ISUP, used to establish, monitor and release circuits
for calls in the PSTN
Designed to allow transfer of circuit information and
status between disparate ISDN networks
Provides basic and supplementary services
Allows automated network testing



Provides circuit testing (circuit validation and continuity) and
translation testing (routing instructions to translate dialed
digits into a routable address, e.g. a point code)
Provides interactive and non interactive test calls
Traffic measurements and report generation
2002-7-24
Krnet 2002
13
SS7 ISUP
Originating
Switch
STP
IAM
ACM
Terminating
Switch
STP
IAM
ACM
ANM
IAM
ACM
ANM
ANM
REL
RLC
2002-7-24
REL
RLC
Krnet 2002
REL
RLC
14
지능망으로의 구현기술 진화모델
Provider
Control
800
교환기
기본기능
만
내장한
교환기
2002-7-24
교환기
교환기
AIN
NGN
Vendor
교환기 Control 교환기
다기능을
SCP 의
차세대
내장한
지원을
지능망구조로
교환기 받는 교환기 다기능을
외부로 부터
지원받는
교환기
Krnet 2002
API
교환과
제어가
완전분리된
교환기
15
지능망 서비스의 흐름
4) 5)
DB 검색
SCP
SDP
SS7 network
3) SCP 에 문의
2) 호전달
1) 지능망 호발신
단국
2002-7-24
6) SCP 에 응답
7) 호발신
SSP
Krnet 2002
단국
16
지능망 서비스의 흐름
4) 5)
DB 검색
SCP
SDP
SS7 network
05025005425?
1) 0502-5005425
2) 호전달
단국
2002-7-24
0313304254
7) 호발신
SSP
Krnet 2002
031-330-4254
단국
17
VoIP기술개요
2002-7-24
Krnet 2002
18
VoIP의 개요

용어




개념


VoIP ( Voice Over IP)
VoP ( Voice over Packet Network)
IP Telephony
패킷교환망을 통하여 음성서비스를 제공하는 기술 및 시스템
등장배경





Internet의 활성화와 함께, 패킷망이 통신망의 주류를 형성
패킷망에 음성신호를 전달하는 인터넷폰으로 통신비용절감
PC-to-Phone, Phone-to-Phone의 개념으로 확장
음성서비스를 패킷망을 통하여 전송하도록 확장
NGN(Next Generation Network)의 개념도입
2002-7-24
Krnet 2002
19
PSTN versus VoIP
Today’s PSTN
VoIP
TDM 회선교환
Packet switching
QoS guarantees
Yes
No
Network resource
reserved at call setup
Yes
No
Network elements
Class 4, Class 5
교환기
Gateways, gateway
controllers, routers
Call processing
intelligence
대부분 교환기에
위치
In separate gateway
controllers
64 kb/s
Variable 8 – 32 kb/s
Signaling
DTMF, SS7
SIP, H.323
Transport
TDM in access,
edge, core
ATM, FR, IP in access;
ATM native IP in core
Underlying Technology
Bandwidth per call
2002-7-24
Krnet 2002
20
VoIP Issue

QoS




패킷망에 의한 음성전달기술





Carrier grade VoIP 서비스
게이트웨이의 Decomposition
신뢰성이 높은 시스템의 구현
다양한 서비스의 신속한 제공



음성압축, QoS, Delay, Jitter
Signaling, Enhanced Service
대용량 게이트웨이의 구현


송신측에서의 음성압축
네트워크 측면의 기술
수신측에서의 기술
계층적 구조
개방형 구조
Next Generation Network으로 진화

Packet기술기반, 다양한 서비스의 수용, 고속접속지원
2002-7-24
Krnet 2002
21
Voice over Internet Protocol
IP Transport
Protocol
Uncompressed
Uncompressed
C. Speech
C. Speech
RTP C. Speech
RTP C. Speech
UDP RTP C. Speech
UDP RTP C. Speech
IP UDP RTP C. Speech
IP UDP RTP C. Speech
Medium: Ethernet, ATM, GSM, GPRS, ...
2002-7-24
Krnet 2002
22
Voice/RTP/UDP/IP

IP: Internet Protocol


UDP: User Datagram Protocol



no retransmission, no flow control <-> TCP
UDP header : 8 octets (port identifier, …)
RTP: Real Time Protocol


IP header : 20 octets (IP address origination, IP address
destination, …)
RTP header : 12 octets
Payload : encoded voice or multi-media stream
IP(20)
2002-7-24
UDP(8) RTP(12)
Krnet 2002
C. Speech
23
VoIP Protocol Stack
Application
Application
Codecs
H.323,
SIP
Codecs
Transport Signaling
Signaling Transport
UDP, TCP, ...
UDP, TCP, ...
IP
IP
(Wireless) Link
(Wireless) Link
Physical
2002-7-24
Krnet 2002
24
Next Generation Tandem Network
SS7
EO
EO
Packet
EO
EO
EO
Gateway
Switch
Packet-Based Tandem
Network
전화망이 모두 없어지거나, 통신망이 모두 IP phone으로 대치되기
전에는 게이트웨이에 의한 연동이 필수적임.
2002-7-24
Krnet 2002
25
VoIP 기술의 요소

음성을 디지털 패킷화 및 전송




신호방식



Bearer Call Signaling
Intelligent Network Call Processing
서비스 생성 및 관리



Speech Coding : 음성압축, 묵음검출
Packetization : IP 패킷의 크기, 헤더의 오버헤드
Multiplexing, Trunking
Supplementary and Multimedia Service
Authentication, Mobility and Directory Service
교환 및 제어 구조


MSF
SoftSwitch
2002-7-24
Krnet 2002
26
Packet Voice 요구사항

Services

Basic Services
•
•
•
•

PC-to-Phone
Phone-to-PC
Phone-to-Phone
PC-to-PC
Supplementary Services
• UMS ( Unified Messaging Service)
• Internet Call Waiting
• Click-to-Dial 등

Interoperability
2002-7-24
Krnet 2002
27
Packet Voice 요구사항 (계속)

Digital Signal and Packet Processing
Voice Coding : 음질, 전송속도, 복잡도에 의해 결정
 Trans-coding : 압축방식의 변환에도 음질 저하 최소화
 Silence Removal : 묵음을 검출하여 묵음시 데이터전송 않음.
 Echo canceling : 전송지연에 따른 엑코현상발생
 Packetization (Serialization) : 패킷화 지연시간 고려
 Buffer smoothing : 음성지연


Addressing/Naming & Routing
E.164, IPv4/IPv6, DNS and Directory Service
 IETF ENUM workgroup

2002-7-24
Krnet 2002
28
Packet Voice 요구사항

Call Processing

Signaling Mode의 수용
• CAS : Channel Associated Signaling
• CCS : Common Channel Signaling
Call Response Time
 Call Processing Capacity

• BHCA : Busy Hour Call Attempt

QoS(Quality of Service)
End-to-End Delay/Jitter
 Packet Loss에 대한 대처방안

2002-7-24
Krnet 2002
29
Packet Voice 요구사항 (계속)

Management



Interworking



Security
Accounting/Charging/Billing
Bearer Interworking
Service (IN) Interworking (080-xxxx, 700-xxxx, etc)
Mobility

Terminal and Service mobility
2002-7-24
Krnet 2002
30
패킷망에 의한 음성전달기술
음성압축, QoS, Delay, Jitter
2002-7-24
Krnet 2002
31
Voice Quality Definition
음질 평가 영향 요소:
• 명료성 Clarity - The
Clarity
“Speech Quality
Space”
Delay
Echo
2002-7-24
Krnet 2002
amount of information that
can be extracted out of a
conversation
• 반사 Echo - Reflection of
the originating signal at the
far end with enough
strength and delay that it is
perceptible to a human.
• 지연 Delay - the time a
signal needs to traverse the
network
32
User Perspective of Voice Quality

MOS (mean opinion score) quality:


Echo degradation



control : subjective perception is dependent on delay
faithful reproduction of background noise
Levels :



depends on coder bit rate and complexity
gain control for optimum level
MOS affected by low level
Latency

the effect of pure delay (no echo) on conversation dynamics
can be detected well below 400 ms for highly interactive
tasks.
2002-7-24
Krnet 2002
33
음성의 디지털 표현
x(t)
Sampler
Continuous-time
Continuous-amp.
2002-7-24
x(n) = x(nt)
Discrete-time
Continuous-amp.
Krnet 2002
Quantizer
x(n)
Discrete-time
Discrete-amp.
34
음성부호화 방식의 종류
Parametric
(Vocoding)
Waveform
Coding
PCM
DPCM
ADPCM
DM
ADM
CSVD
2002-7-24
Hybrid
Coding
APC
RELP
MPLPC
CELP
SELP
Krnet 2002
Channel
Formant
LPC
MBE
35
Speech Coder의 형태

Waveform coding




Vocoder




Time domain
Frequency domain
예 : PCM (Pulse Code Modulation) 64kbps
LPC ( Linear Prediction Coding)
Low Rate
음성발생기관을 모델링
Hybrid coding



RELP ( Residual Excited Linear Prediction)
CELP ( Code Excited Linear Prediction)
이동전화, 인터넷폰 응용
2002-7-24
Krnet 2002
36
음성발성기관 모델
2002-7-24
Krnet 2002
37
음성발생과 Vocoder 원리
10-30 ms 사이에는
Quasy-stationary
폐의 여기신호
입, 성도모양
음성파형
Sub optimal Solution
성모모양필터가
구해진 상태에서
여기신호를 추출함.
미지수 1개, 식 1개
음성파형으로부터
성도의 모양 필터
를 추출함.
미지수 1개, 식 1개
음성파형으로부터
성도의 모양 필터
폐의 여기신호를
추출함.
미지수 2개, 식 1개
2가지 값은
저전송속도로
수신단에 전송하고
수신단에서 합성함.
2002-7-24
Krnet 2002
38
분석-합성 방식에 의한 음성부호화

파형부호화 방식으로는 32-64 bps 정도로압축의 한계가
있음.

분석합성 방식이란


폐에서의 공기발생 + 성도필터 = 음성






프레임 구간(10-30ms)으로 구분
우선, 필터계수를 구하고
Excitation 신호를 구하여,
저전송속도로 수신단에 송신함.
수신단에서는


공기발생형태 : Excitation signal
성도필터 : Linear Prediction Filter
송신단에서 입력음성을 분석하기 위해서


음성발생모델을 이용하여 음성을 고능률 압축하는 방식
파라메터 정보를 가지고 음성을 합성함.
전송속도는 2.4 kbps 정도이나 음질이 문제임.
2002-7-24
Krnet 2002
39
Hybrid Coder

음질을 개선하기 위해서는




Excitation Signal 방식



성도필터의 계산방법은 그대로 채용하되, 유성음과 무성음을
구분하는 단순한 방법을 사용하는 대신,
Excitation signal을 변화시켜가면서, 신호를 합성하여,
입력음성과 차이가 최소화 되면,
Excitation signal의 값과 필터계수를 송신
Codebook을 미리 작성하고, index를 찾는 방식
신호를 산술적인 계산에 의해서 찾는 방식
Various excitation signal



MPE (multi-pulse excited)
RPE (regular-pulse excited)
CELP (code-excited linear prediction)
2002-7-24
Krnet 2002
40
Hybrid coders

Multi-Pulse Excitation




Regular-Pulse Excitation (RPE)




Efficient at medium bit rates.
A sequence of nonuniformly spaced pulses as an excitation
signal
Amplitudes and positions are excitation parameters
Efficient at medium bit rates.
A sequence of uniformly spaced pulses as an excitation
signal
The position of first pulse within a vector and amplitudes are
excitation parameters
Code-Excited Linear Prediction (CELP)



Efficient at low bit rates (below 8 kbps)
A code book of excitation sequences
Two key issues; the design and search of a codebook
2002-7-24
Krnet 2002
41
여기 신호의 종류
g3
g1
gk
n4
n2
n1
a) multipulse
n3
nk
g2
0
5
g1
b) regular-pulse
g4
10
g2
15
20
g6
g4
K
g5
g3
Codebook
c) Code-excited
Linear Prediction
Codevector # 1
Codevector # 2
Codevector # 3
2M = N
(M = 전송 bit)
Codevector # N
2002-7-24
Krnet 2002
42
분석/합성 LPC coder
Speech
vector1
CELP
Vocal Tract
Model
Filter
~
S(n)
+
S(n)
e(n)
MP-MLQ
Error
Minimization
2002-7-24
Krnet 2002
43
Frame Processing and Delay

G.729의 linear prediction
Linear Prediction
Frame
Delay
LP parameter
Lookahead
delay
time
120 samples
(past)
2002-7-24
80 samples
current frame
Krnet 2002
40 samples
(future)
44
분석-합성 방식에 의한 음성부호화
Input speech Frame (10,20,30 ms)
codebook
Excitation
Generation
Synthesis
Filter
Error
Minimization
codebook
정보전송
Excitation
Generation
Error
Weighting
(a) Encoder
Synthesis
Filter
Reconstructed
speech
(b) Decoder
2002-7-24
Krnet 2002
45
H.323용 보코더

ITU-T G.7xx series 보코더
보코더
G.711
G.722
G.726
G.728
G.729
G.723.1
2002-7-24
비트율
(kbit/s)
64
64/56/48
32/24/16
16
8
5.3/6.3
지연시간
(ms)
0
3
0.25
1.25
25
62.5
Krnet 2002
복잡도
(MIPS)
<<1
10
1.25
30
20
20
대역폭
(kHz)
4
7
4
4
4
4
46
ITU-T G.723.1





Dual rate (5.3/6.3 kbit/s) ITU-T 표준 보코더
1995년 말 표준확정, 멀티미디어 통신용으로 개발
대부분의 인터넷폰에서 표준으로 지원
Frame size : 30 ms, Lookahead : 7.5 ms
5.3 kbit/s higher rate



ACELP (Algebraic Code Excited Linear Prediction)
USH (Univ. of Sherbrooke) contributed
6.3 kbit/s lower rate



MP-MLQ (Multi-Pulse maximum Likelihood Quantization)
ACL/DSPG contributed
Toll quality
2002-7-24
Krnet 2002
47
G.723.1 Extensions

Annex A



G.723.1 + VAD/SID/CNG(Comfort Noise Generation)
음성이 없는 구간에서 noise발생
Noise의 특성을 전송 - SID (Silence insertion description)
• Active noise와 silent noise간의 자연스러운 연결

DTX (Discontinuous Transmission)
• Noise특성을 전송할 필요가 있는지 결정

Annex B


G.723.1의 부동소수점 구현
Annex C




Scalable channel coding scheme for wireless applications
H.324의 일부로 개발
Channel bit-rate: 0.7 ~ 14.3 kbit/s
Channel codec: punctured convolutional codes
2002-7-24
Krnet 2002
48
Quality, Complexity and Delay
DELAY/COMPLEXITY
excellent
Quality
ITU4
2000+?
G.729
1996
G.728
1992
G.726
1984
good
G.711
1972
clean speech
G.723.1
1995
fair
poor
2
2002-7-24
4
16
8
bitrate (kb/s)
Krnet 2002
32
64
49
Voice over Internet Protocol
IP Transport
Protocol
Uncompressed
Uncompressed
C. Speech
C. Speech
RTP C. Speech
RTP C. Speech
UDP RTP C. Speech
UDP RTP C. Speech
IP UDP RTP C. Speech
IP UDP RTP C. Speech
Medium: Ethernet, ATM, GSM, GPRS, ...
2002-7-24
Krnet 2002
50
Voice Coding Bandwidth
Bytes
Frame size
G.723.1
G.729a
30ms
10ms
Coder
20(G.723.1)
10(G.729a)
6.3
8.0
RTP
12
3.2
9.6
UDP
8
2.1
6.4
IP
20
5.3
16.0
Total
40
16.9
40.0
IPv6 Total
54
20.7
51.2
G.729a는 20ms 마다 패킷화하여 전송하면, 오버헤드 줄일 수 있음.
Overhead를 줄이기 위한 방안 모색필요
IETF ROHC( Robust Overhead Compression)
2002-7-24
Krnet 2002
51
Packet Loss Characteristics

Packet Loss 원인




Source Site - overwrite
Intermediate Site - dropping
Destination Site - time constraint
Packet Loss 대응방안

Packet Repetition
• GSM 에서 사용하는 방식


Packet Interpolation
Frame Interleaving
• Bursty Error의 영향을 분산시키나 지연시간이 길어짐.

Forward Error Correction
2002-7-24
Krnet 2002
52
Delay Variation—―Jitter‖
A
B
C
Sender Transmits
t
A
D1





B
D2 = D1
C
Sink Receives
D3 = D2
t
Queueing delay 의 변화에 의해 발생
Hold time과 Jitter Buffer size의 비례관계
Jitter가 전체 Delay에 미치는 영향이 더 큼.
50-100ms 사이를 사용
Delay에 따라 Buffer Size가 적응되도록 함.
2002-7-24
Krnet 2002
53
DTMF Transfer

DTMF 문제




음성부호화방식은 음성의 특성에 최적화하여 압축비를 높임.
Tones: fax tones, dialing tone, busy tone
DTMF digits for two-stage dialing or voice-mail
DTMF전송방식

In-band 방식 (G.729에서 사용하는 방식)
• DTMF tone을 음성처럼 부호화하여 전송함.
• 음성부호화 방식이 tone도 정확히 코딩, 디코딩 할 수 있어야 함.

Out-of-band 방식 (G.723.1 의 방식)
•
•
•
•
•
•
2002-7-24
DTMF는 음성특성과 달라 DTMF의 전달특성이 나쁨
Encoder에서 DTMF 검출
제어패킷으로 만들어 별도로 TCP를 통하여 전송
수신부(Decoder)에서 DTMF톤 발생
검출전에 DTMF톤의 일부가 전송됨
데이타망의 상태에 따라 지연이 발생됨.
Krnet 2002
54
Out of Band 방식

The ingress gateway needs to intercept





The tones and DTMT digits
Use an external signaling system
Easy at the start of a call
Difficult in the middle of a call
Encode the tones differently form the speech




Send them along the same media path
An RTP packet provides the name of the tone and the
duration
Or, a dynamic RTP profile; an RTP packet containing the
frequency, volume and the duration
RFC 2198
• An RTP payload format for redundant audio data
• Sending both types of RTP payload
2002-7-24
Krnet 2002
55
Echo
Echo - Reflection of the originating signal at the far end
with enough strength and delay that it is perceptible
to a human.
Phone
PSTN Network
Hybrid
Echo
Cancel.
Echo
Cancel
Gateway
IP Network
H.323 Terminal
Line Echo
Acoustic Echo
Echo tail ( 8 - 120 mS)
2002-7-24
Krnet 2002
56
Echo의 원인 및 대책
Central Office
2 Wire
Local Loop
Rx & Tx
Superimposed
2w-4w
Hybrid
EC
Receive
Direction
인터넷
Transmit
Direction



Echo는 반사에 의해서 생김.
2w-4w hybrid 에서의 Impedance mismatch가 엑코의
발생원인임.
Echo는 항상 발생하지만, Echo의 지연시간과 Echo의 크기에
따라 문제로 대두됨.
2002-7-24
Krnet 2002
57
VoIP 표준
2002-7-24
Krnet 2002
58
VON 관련 표준화기관

ITU - International Telecommunications Union SG 16



IETF - International Engineering Task Force






multimedia 단말과 security에 관한 연구
H.323
web services 와 PSTN/ISDN의 상호연동
Iptel : IP telephony
PINT: PSTN-Internet service
Sigtran : Telephony signaling transport
SIP : Session Initiation Protocol
ETSI - European Telecomm. Standards Institute


TIPHON (Telephony and IP Harmonization Over Networks)
SPS5 (UNI/NNI signaling aspects)
2002-7-24
Krnet 2002
59
표준화기관의 관계
SG16
SG2
Multimedia Numbering
SG11
Signaling
SG13
Architecture
권고안
표준개발요구
Integrated Keeper spec
Global country code
T1
ITU-T
Naming/Addressing
QoS
Interoperability
TIPHON
Collaboration
RFCs
Megaco
2002-7-24
PINT
IPTEL
Krnet 2002
Requirement
SIP
IETF
60
VoIP Protocols

H.323 (ITU-T)



SIP (IETF)




initial push for VON interoperability
Multimedia session control - call control
Session Initiated Protocol – Call Control
SIP/ SAP/ SDP
SIP+ (MGC to MGC communication)
MGCP (IETF : Media Gateway Control Protocol)

Decomposed gateway model
• media gateway controller (MGC)
• media gateway (MG)
• signaling gateway (SG)
2002-7-24
Krnet 2002
61
VoIP Protocols

MEGACO (IETF)


H.248 (ITU-T) [formerly H.GCP]


ITU variant of MEGACO
SIP-T (IETF, Cable Labs)


MEdia GAteway Control; Successor to MGCP
Signaling between media gateway controllers
SCTP (IETF Sigtran)


Simple Control Transmission Protocol
Transport PSTN signaling (SS7, Q.931) over IP
2002-7-24
Krnet 2002
62
H.323
2002-7-24
Krnet 2002
63
H.323

ITU-T Recommendation H.323 Version 4


Describes terminals and other entities that provide
multimedia communications services over Packet Based
Networks (PBN) which may not provide a guaranteed Quality
of Service. H.323 entities may provide real-time audio, video
and/or data communications.
H.323 elements




Terminals
Gateways
Gatekeepers
MCUs
2002-7-24
Krnet 2002
64
H.323
H.323
Terminal
H.323
Gatekeeper
N-ISDN
Speech
Terminal
H.320
Terminal
Scope of H.323
Non-Guaranteed QoS LAN
H.323
Gateway
H.323
Terminal
Guaranteed
QoS LAN
B-ISDN
H.322
Terminal
H.321
Terminal
H.321
Terminal
H.310 terminal
operating in
H.321 mode
2002-7-24
H.323
MCU
Krnet 2002
H.323
Terminal
V.70
Terminal
(DSVD)
GSTN
H.324
Terminal
Speech
Terminal
(H.324M)
65
H.323 Functional Block Diagram
Scope of H.323
Video I/O Equipment
Video Codec
H.261, H.263
Audio I/O Equipment
Audio Codec
G.711, G.722
G.723, G.728
G.729
User Data
Applications
T.120 etc.
Receive
Path
Delay
System Control
H.225.0
Layer
H.245 Control
System Control
User Interface
Local
Area
Network
Interface
Call Control
H.225.0
RAS Control
H.225.0
•RAS - registration, admission, status
2002-7-24
Krnet 2002
66
H.323 표준의 범위

H.323 defines




H.225 defines



System-level characteristics of terminals, gateways,
gatekeepers, and MCUs
Call signaling procedures (phases A-E)
Refers to H.225 and H.245 specs
Packetization and use of RTP/RTCP
Use of Q.931/2 and RAS messages
H.245 defines

Procedures for use of Control Protocol messages
2002-7-24
Krnet 2002
67
H.323 is an “Umbrella” Specification
Media
Signaling
Audio
Codec
G.711
G.723
G.729
Call Control and
Video
Codec
H.261
RTCP
H.263
H.225
H.225
Q.931
RAS
TCP
UDP
H.245
RTP
UDP
TCP
IP
2002-7-24
Krnet 2002
68
Overview of H.323 Singaling



Audio codecs (G.711, G.723.1, G.728, etc.)
Video codecs (H.261, H.263)
Media streams transported on RTP/RTCP


RTP carries actual media
RTCP carries status and control information

RTP/RTCP carried unreliably on UDP

Signaling is transported reliably over TCP



RAS - registration, admission, status (over UDP)
Q.931 - call setup and termination
H.245 - capabilities exchange
2002-7-24
Krnet 2002
69
통신과정

H.323의 통신과정 5단계





Call setup.
Initial communication and capabilities exchange.
Audio/video communication establishment.
Call services.
Call termination.
2002-7-24
Krnet 2002
70
단순한 H.323 Call Setup
Gatekeeper
GK
1. ARQ
2. ACF
3. SETUP
4. Call Proceeding
5. ARQ
6. ACF
7.Alerting
8.Connect
H.245 Messages
RTP Media Path
RAS messages
Call Signaling Messages
2002-7-24
Krnet 2002
71
Simplified H.323 Call Setup








Both endpoints have previously registered with the
gatekeeper.
Terminal A initiate the call to the gatekeeper. (RAS
messages are exchanged).
The gatekeeper provides information for Terminal A to
contact Terminal B.
Terminal A sends a SETUP message to Terminal B.
Terminal B responds with a Call Proceeding message
and also contacts the gatekeeper for permission.
Terminal B sends a Alerting and Connect message.
Terminal B and A exchange H.245 messages to
determine master slave, terminal capabilities, and
open logical channels.
The two terminals establish RTP media paths.
2002-7-24
Krnet 2002
72
H.323 basic protocols
Annex G
Gatekeeper
RAS
Gatekeeper
Q.931/H.245
Q.931/
H.245
Q.931/
H.245
RAS
Signalling (Q.931)
Endpoint
H.245
RTP/RTCP
Endpoint
Gatekeeper Routed Signaling
Direct Routed Signaling
2002-7-24
Krnet 2002
73
H.323 Components and Signaling
H.225/RAS messages
over RAS channel
H.225/Q.931 (optional)
H.225/RAS messages
over RAS channel
Gatekeeper
H.225/Q.931 (optional)
H.245 messages (optional)
H.245 messages (optional)
H.225/Q.931 messages over
call signaling channel
Terminal



H.245 messages over
call control channel
PSTN
Gateway
H.245 – A protocol for capabilities advertisement, media
channel establishment and conference control.
H.225 - Call Control.
RAS – Registration, admission and status protocol
2002-7-24
Krnet 2002
74
H.225 RAS Signaling

RAS(Registration, Admissions, Status)시그널링






GRQ(Gatekeeper Request)
RRQ(Registration Request)
LRQ(Location Request)
ARQ(Admission Request)
IRQ(Inforamation Request)
BRQ(Bandwidth Request)
2002-7-24
Krnet 2002
75
RAS Messages

GRQ/GCF/GRJ (Discovery)










Endpoint alias/IP address
binding
Endpoint authentication
Destination Address
Resolution
Initial bandwidth request
Call Routing
Call Authorization


Get rid of call state
2002-7-24
Krnet 2002
Ping during active calls
Resource information for
gateways
BRQ/BCF/BRJ (Bandwidth)


Stateless name - IP address
resolution
Inter gatekeeper
communication
IRQ/IRR (Information
Request)

DRQ/DCF/DRJ (Disconnect)

LRQ/LCF/LRJ (Location)

ARQ/ACF/ARJ (Admission)


Unicast - Multicast
Find a gatekeeper
RRQ/RCF/RRJ
(Registration)


Ask for more/less bandwidth
during call
URQ/UCF/URJ
(Unregistration)

Get rid of registration state
76
RAS - Direct Call Signaling
Gatekeeper A
LRQ
Gatekeeper B
LCF
ACF
ACF
IP Network
RRQ / RCF
RRQ / RCF
ARQ
H.225 (Q.931) Setup
ARQ
H.225 (Q.931) Alert & Connect
H.245
V
RTP
Gateway A
V
Gateway B
Phone B
Phone A
2002-7-24
Krnet 2002
77
RAS - GK Routed Call Signaling
Gatekeeper A
LRQ
Gatekeeper B
LCF
H.225 (Q.931) Setup
H.225 Alert & Connect
H.245
ACF
A&C
Setup
ACF
IP Network
H.245
H.245
ARQ Setup
V
ARQ
RTP
Gateway A
Phone A
2002-7-24
Alert & Connect
V
Gateway B
Krnet 2002
Phone B
78
H.225

호제어 시그널링(Call Control Signaling)







H.225표준, Q931 signal Message
Setup
Call Proceeding
Alerting
Release Complete
Faclity
호제어 처리방식 종류 – DECS, GKRCS
2002-7-24
Krnet 2002
79
Q.931 Signaling 절차
UNI
UNI
ATM 망
SET UP
SET UP
CALL
PROCESSING
CALL
PROCESSING
CONNECT
CONNECT
CONNECT
ACK
CONNECT
ACK
Signaling Cell(ATM Forum)
VPI=0, VCI=5
2002-7-24
VCC 설정
ATM Cell
Header
Krnet 2002
Signaling Message
80
H.245


H.245 미디어 제어 및 전송(Media Control and Transport)
H.245 제어 동작과정




capabilities 교환 – 단말기의 음성, 비디오 및 데이터를
위한 송수신 능력
Master-Slave 결정
Round –Trip : 송신단말기에서 수신단말기까지의 지연을
결정.
로지컬 채널 시그널링
2002-7-24
Krnet 2002
81
H.245 System Control

Capabilities Exchange




Master/Slave Determination
Open Logical Channel/Ack


Codec negotiation - Transmitter/Receiver capabilities
Mode Request - Request specific transmission format
Create new audio/video/T.120 stream
Commands and Indications

out of band DTMF
2002-7-24
Krnet 2002
82
H.323 End-to-End

Direct Signaling with Slow Start
1. H.225 RAS ARQ/ACF
location/admission
(UDP)
GK
3. H.225 RAS ARQ/ACF
admission
(UDP)
2. H.225 Q.931 signaling-setup, proceed, alert, connect (TCP)
323
4. H.245 media negotiation-TCS, MSD, OLC, OLCA (TCP)
323
5. RTP media
(UDP)
2002-7-24
Krnet 2002
83
H.323 End-to-End

Gatekeeper-Routed Signaling with Fast Start
2. H.225 Q.931 signaling
with fastStart media
negotiation-setup, proceed,
alert, connect (TCP)
GK
1. H.225 RAS
ARQ/ACF
location/admission
(UDP)
323
2002-7-24
3. H.225 Q.931 signaling
with fastStart media
negotiation-setup, proceed,
alert, connect (TCP)
4. H.225 RAS
ARQ/ACF
admission
(UDP)
5. RTP media (UDP)
Krnet 2002
323
84
RTP/RTCP—RFCs 1889/1890

End-to-end network transport function





Sequence numbering
Time Stamping
Delivery monitoring
Payload type identification - Voice, Video, Compression
Type
RTCP (Real-Time Control Protocol) provides feedback
on the quality of the distribution
V
4bytes E
R
CC
M
Payload
Type
Sequence Number
4bytes
RTP Timestamp
4bytes
Synchronization Source (SSRC) ID
2002-7-24
Krnet 2002
85
Session Initiation Protocol
2002-7-24
Krnet 2002
86
Relevant IETF Working Groups













Audio/Video Transport (avt) - RTP
Differentiated Services (diffserv) – QoS in backbone
IP Telephony (iptel) – CPL, GW location, TRIP
Integrated Services (intserv) – end-to-end QoS
Media Gateway Control (megaco) – IP telephony gateways
Multiparty Multimedia Session Control (mmusic) – SIP, SDP
PSTN and Internet Internetworking (pint) – mixt services
Resource Reservation Setup Protocol (rsvp)
Service in the PSTN/IN Requesting InTernet Service (spirits)
Session Initiation Protocol (sip) – signaling for call setup
Signaling Transport (sigtran) – PSTN signaling over IP
Telephone Number Mapping (enum) – surprises !
Instant Messaging and Presence Protocol (impp)
2002-7-24
Krnet 2002
87
What is SIP?

IETF RFC 2543 Session Initiation Protocol


Session Initiation Protocol - An application layer signaling
protocol that defines initiation, modification and termination
of interactive, multimedia communication sessions between
users.
Components





User Agents
Proxy Server
Location Server
Redirect Server
Registrar Server
2002-7-24
Krnet 2002
88
SIP Distributed Architecture
SIP Components
Location
Server
Redirect
Server
Registrar
Server
PSTN
User Agent
Gateway
Proxy
Server
2002-7-24
Proxy
Server
Krnet 2002
89
SIP Components

User Agents

An application that initiates, receives and terminates calls.
• User Agent Clients (UAC) – An entity that initiates a call.
• User Agent Server (UAS) – An entity that receives a call.
• Both UAC and UAS can terminate a call.

Proxy Server




An intermediary program that acts as both a server and a
client to make requests on behalf of other clients.
Requests are serviced internally or by passing them on,
possibly after translation, to other servers.
Interprets, rewrites or translates a request message before
forwarding it.
Location Server

A location server is used by a SIP redirect or proxy server to
obtain information about a called party’s possible location(s).
2002-7-24
Krnet 2002
90
SIP Components

Redirect Server




A server that accepts a SIP request, maps the address into
zero or more new addresses and returns these addresses to
the client.
Unlike a proxy server, the redirect server does not initiate its
own SIP request.
Unlike a user agent server, the redirect server does not
accept or terminate calls.
Registrar Server



A server that accepts REGISTER requests.
The register server may support authentication.
A registrar server is typically co-located with a proxy or
redirect server and may offer location services.
2002-7-24
Krnet 2002
91
SIP Messages – Methods

SIP Methods:







INVITE – Initiates a call by inviting user to participate in
session.
ACK - Confirms that the client has received a final response
to an INVITE request.
BYE - Indicates termination of the call.
CANCEL - Cancels a pending request.
REGISTER – Registers the user agent.
OPTIONS – Used to query the capabilities of a server.
INFO – Used to carry out-of-bound information, such as
DTMF digits.
2002-7-24
Krnet 2002
92
SIP Messages –Responses

SIP Responses:






1xx - Informational Messages.
2xx - Successful Responses.
3xx - Redirection Responses.
4xx - Request Failure Responses.
5xx - Server Failure Responses.
6xx - Global Failures Responses.
2002-7-24
Krnet 2002
93
통신설정 과정

SIP을 이용한 6가지 통신설정 단계






Registering, initiating and locating the user.
Determine the media to use – involves delivering a
description of the session that the user is invited to.
Determine the willingness of the called party to communicate
– the called party must send a response message to indicate
willingness to communicate – accept or reject.
Call setup.
Call modification or handling – example, call transfer
(optional).
Call termination.
2002-7-24
Krnet 2002
94
SIP - Session Initiation Protocol


IETF RFC2543, March 1999
Function



SIP Redirect Server
2
Conveyed as message body



Based on IP
Interoperability
Scalability
Platform for applications
5
4
1
6
11
12
Benefits

Location Service
3
Independent of session


Invite user to interactive
sessions
Terminate and modify
sessions
7
SIP Proxy
1
0
8
9
SIP Client
SIP Proxy
Request
SIP Client
(User Agent Server)
Response
2002-7-24
Krnet 2002
95
SIP/ SAP/ SDP

SIP – Session Initiation Protocol





SAP – Session Announcement Protocol



Application layer signaling protocol
Text, HTTP-like
Extensions being drafted for Calling party privacy, distributed
call signaling (DCS), local number portability (LNP)
SIP+ is now SIP-T (or SIP-BCP) for Telephony Interworking
Multicast multimedia session directory
Announcers and listeners
SDP – Session Description Protocol


Not really a protocol
Also used by MGCP
2002-7-24
Krnet 2002
96
H.323 and SIP

H.323





SIP






Widely deployed (in gateways and PC’s)
Full backwards compatibility
Multimedia ready
Complex protocol (bulky code size)
Firewall friendly
User friendly
Shorter call setup time
Easy implementation (smaller code size)
새로운 표준으로 우세한 상황으로 전개되고 있음.
Hot Topic: SIP and H.323 Interworking
2002-7-24
Krnet 2002
97
H.323 vs. SIP








H.323
ITU Standard
Binary-based ASN.1
encoding
Utilizes other ITU
standards such as ISDN
(Q.931) and Q.SIG model
Defines call signaling, call
transfer, codec negotiation
Network services are
provided by Gatekeepers
Direct endpoint or
Gatekeeper routed call
signaling
Uses RTP for media
2002-7-24








Krnet 2002
SIP
IETF Standard
ASCII text-based
Leverages other Internet
standards such as HTTP,
DNS, MIME, etc.
Defines only session
initiation and termination
(call signaling)
Network services provided
by SIP servers (Proxy,
Redirect, and Registrar)
Endpoint signaling or
“record-route” signaling
Uses RTP for media
98
Why SIP and H.323 Must Co-exist

Established base of large-scale H.323 networks



SIP is the new “buzz” word




ITSPs have been around for several years
Equipment vendors only supported H.323 until recently
Gaining industry momentum (embedded SIP clients in
future operating systems and PDAs)
Protocol based on Internet standards
Concept of presence in the network brings with it new and
exciting services
As a result, existing ITSPs are now beginning to offer
SIP services along with their existing H.323 services
2002-7-24
Krnet 2002
99
System Decomposition
2002-7-24
Krnet 2002
100
ITU H.323 Decomposition
Service Agent
User GK
Gatekeeper
Network GK
H.323
gateway
분산시스템
개방형 인터페이스
독립적 발전가능
Media
Gateway
Controller
MGCP
Media
Gateway
2002-7-24
Krnet 2002
101
스위치의 구현기술 진화모델
Provider
Control
800
교환기
기본기능
만
내장한
교환기
2002-7-24
교환기
다기능을
내장한
교환기
교환기
AIN
교환기
NGN
Vendor
교환기
Control
SCP 의
차세대
지원을
지능망구조로
받는 교환기 다기능을 외부로
부터 지원받는
교환기
Krnet 2002
API
교환과
제어가
완전분리된
교환기
102
IP Gateway 의 기능요소

제어정보 ( Control )


Telephony Protocols
IP Call Control Protocols
ISUP
• H.323 (ITU)
• SIP(IETF)

이용자정보 (Media)

PCM streams
GSTN
Side
• 64kbps

IP Packets
• Jitter
• Delay
• Sequence 변경
2002-7-24
Voice Stream
PCM
Krnet 2002
Signaling
Gateway
Media
Gateway
Controller
Media
Gateway
IP
Side
Voice Stream
IP Packet
103
Gateway Decomposition IETF
SG: Signaling Gateway
MGC: Media Gateway Controller
MG: Media Gateway
Gateway Function
SG
SS7,
Q.931
SSP
Sigtran
MGC
PSTN
IP
Network
Megaco
Bearer
Channels
2002-7-24
IP Signaling
(e.g. H.323, SIP)
MG
Krnet 2002
Packetized Media
(e.g., RTP)
104
VoIP Gateway의 구성(IETF)
SG: Signaling Gateway
MGC: Media Gateway Controller
MG: Media Gateway
IP
Device
PSTN
PSTN
SS7,
SSP Q.931
SG
SCTP
MGC
MGCP,
MEGACO,
H.GCP/H.248
Gateway
Bearer
Channels
2002-7-24
SIP+
MGC
MG
RTP/RTCP
IP
Network
Krnet 2002
SCTP
SG
SS7, SSP
Q.931
Gateway
MG
Bearer
Channels
105
VoIP Standards
Applications
(…)
(…)
Call Control
& Service
Control
H.225 Annex G
SIP-T or BICC
Call Control
& Service
Control
H.225
H.225
Bearer
Control
H.245 SDP
Bearer
Control
MGCP/Megaco MGCP/Megaco
/AAL1/2/5
RTP
Media
2002-7-24
Media
Krnet 2002
106
Gateways

Media Gateway (MG)



미디어 변환기능 수행 e.g., TDM-to-RTP
No call states
Gateway의 종류

Trunking gateways
• digital circuits으로 PSTN접속

Business gateways
• Digital PBX interface, soft-PBX interface

Residential gateways
• Set-top boxes, xDSL devices, cable modem equipment

Access Gateways
• 소용량 VoIP gateways, MG, CA, MGC

Voice over ATM gateways
• ATM network에 접속
2002-7-24
Krnet 2002
107
Media Gateways Controller

Media Gateway Controller (MGC)



MGC 는 망내의 지능이 분산가능하도록 함.
Call processing, routing, billing, protocol conversion etc.
Media gateway의 제어프로토콜을 사용
• SGCP, MGCP
• Megaco protocol, H.248






Controls MG by sending MGCP commands to create, modify,
delete connections
Receives PSTN and Internet signalling
Maintains overall call state
Monitors MG resources
Makes call routing decisions
Records call detail records
2002-7-24
Krnet 2002
108
VoIP Controllers

ITU H.323 Gatekeeper





IETF SIP server



Name Address translation : Alias  IP @
Admission control : CAC, authorisation of access to a LAN
Bandwidth control
Zone management : registration of terminals, gateways and
MCUs
Invitation to multimedia conferences
Name Address Translation, Capabilities negotiation,
Gateway service invocation, ...
IETF MGCP : Media Gateway Control protocol


It provides call control for multiple media gateways
It interfaces with signalling gateways
2002-7-24
Krnet 2002
109
What is MGCP?

IETF RFC 2705 Media Gateway Control Protocol



Components
Call agent or media gateway controller



Media Gateway Control Protocol - A protocol for controlling
telephony gateways from external call control elements
called media gateway controllers or call agents.
Provides call signaling, control and processing intelligence to
the gateway.
Sends and receives commands to/from the gateway.
Gateway



Provides translations between circuit switched networks and
packet switched networks.
Sends notification to the call agent about endpoint events.
Execute commands from the call agents.
2002-7-24
Krnet 2002
110
Components
Call Agent or
Media Gateway
Controller
(MGC)
Call Agent or
SIP
Media Gateway
H.323
Controller
(MGC)
MGCP
MGCP
Media Gateway
(MG)
2002-7-24
Media Gateway
(MG)
Krnet 2002
111
단순화한 호흐름(Call Flow)






Phone A 가 오프후크하면, Gateway A 는 Call agent에서
신호를 전송
Gateway A는 발신음을 송출하고, 이용자가 입력한 번호를
수신함. 이 번호는 call agent로 전달됨.
call agent는 호 라우팅을 결정함.
call agent가 Gateway B에 명령을 내림.
Gateway B 는 phone B에 호출음 송출
call agent 는 양측 게이트웨이에 RTP/RTCP sessions을
개설하도록 명령을 내림.
2002-7-24
Krnet 2002
112
Call Flow

MGCP



A user picks up analog phone and dials a number.
The gateway notifies call agent of the phone (endpoint) event.
The Call agent determines capabilities, routing information, and
issues a command to the gateways to establish RTP/RTCP session
with other end.
2
Call Agent/
Media Gateway
Controller
1
Analog
Phone
2002-7-24
RTP/
Gateway
A
RTCP
Krnet 2002
Gateway
B
Analog
Phone
113
MGCP Commands

Call Agent Commands:








EndpointConfiguration
NotificationRequest
CreateConnection
ModifyConnection
DeleteConnection
AuditEndpoint
AuditConnection
Gateway Commands:



Notify
DeleteConnection
RestartInProgress
2002-7-24
Krnet 2002
114
Characteristics of MGCP

MGCP:

A master/slave protocol.
• Assumes limited intelligence at the edge (endpoints) and
intelligence at the core (call agent).
• Used between call agents and media gateways.
• Differs from SIP and H.323 which are peer-to-peer protocols.

Interoperates with SIP and H.323.
2002-7-24
Krnet 2002
115
Decomposed Gateway Components

Signaling Gateway (SG)


대역외 신호방식(SS7, Q.931)의 신호를 종단하여, MGC로
전달 (Sigtran)
신호변환기능은 수행하지 않음. (i.e., no ISUP-H.323 interworking)
SS7 SSP
Signaling
Gateway
App
MGC/
Softswitch
App
IWF
ISUP
ISUP
MTP-3
MTP-3
M3UA
M3UA
MTP-2
MTP-2
SCTP
SCTP
IP
IP
IWF = Inter-working Function
M3UA = MTP-3 Adaptation Layer
2002-7-24
Krnet 2002
116
SCTP Protocol Features

Connection oriented



Reliable packet delivery






Fail-over to a redundant link(s), but no load sharing
Supports IPv4 and IPv6 addressing
TCP-like flow control and congestion avoidance


Selective retransmission of lost/corrupted packets
Detection of duplicate packets
Packet integrity protected by checksum and verification tags
Explicit support for multi-homed hosts


Multiple control “streams” per port
In-sequence delivery within a “stream”, if desired
Internet friendly
Fragmentation of long packets on network MTU
boundaries
Bundling of multiple small chunks into single
transmission unit
2002-7-24
Krnet 2002
117
VoIP와 Next Generation Network
2002-7-24
Krnet 2002
118
네트워크 발전추세

음성과 데이타망의 통합



광대역 전송 기술의 도입



XoIP – 모든 미디어가 IP로 전송됨.
QoS 만족을 위한 전송망의 진화
유선분야 : xDSL, Cable, Optical network
무선분야 : W-CDMA, W-LAN, Bluetooth
Content 및 application을 망에서 제공



Personal rich media
Storage networks
Application Services
2002-7-24
Krnet 2002
119
차세대통신망의 진화경로
PSTN 및
지능망
지능망서비스를 인터넷에서 제어
Hybrid
Networks
Internet 및
데이타망
Internet
Telephony
VoP
Networks
Next
Generation
Networks
ALL IP 핵심망
무선통신망
2002-7-24
Krnet 2002
120
서비스 제공구조

현재의 voice 서비스 구조





현재의 IP network architecture





PSTN 에 기반, Services Nodes 와 SCP 사용
제한된 customer data features
Back end provisioning – no customer interaction
Limited customer control of new features or services
데이터 서비스 중심이며, 제한된 음성서비스 제공
Easy customer or end user provisioning - Web
Flexible environment for new features and services
Powerful platform for integrated data, voice and video
services
통신사업자의 목표는 음성과 데이터 서비스를 통합하고,
공통의 IP 기반망 플랫폼에서 서비스를 제공하고자 함.
2002-7-24
Krnet 2002
121
Hybrid Network 개념


PSTN의 지능망과 IP 데이타망/VoIP망과 연동하는
망서비스
Web 기반 서비스 관리




데이터 저장 및 접근


LDAP(Lightweight Directory Access Protocol) 이용
Service Invocation and Call Control



PSTN의 지능망 서비스의 내용을 웹에서 변경
적용가능분야 ; 평생전화번호서비스의 번호변경
예 : 대만의 청화통신
PINT(PSTN and Internet Internetworking)
SPIRITS(Services In the PSTN/IN Requesting Internet
service)
New Applications for specialized resources

NTT의 L-mode
2002-7-24
Krnet 2002
122
Network Architecture
STP
Call
Agent
Call
Agent
MGCP
RGW
RGW




TCAP/SS7
SS7
Gateway
ISUP/SS7
MGCP
Internet
Trunking
Gateway
PSTN
Voice
Residential Gateway(RGW)
Trunking Gateway(TGW)
Call Agent - Media gateway controller
SS7 Gateway
2002-7-24
SCP
Krnet 2002
MGCP : Media Gateway Control Protocol
SIP
: Session Initiation Protocol
SCP : Signaling Control Point
STP : Signaling Transfer Point
ISUP : ISDN User Part
TCAP : Transaction Capabilities Application Part
123
Protocol Support
Application Specific
Application Layer
• Call intelligence
• Service creation/ execution
• Mgmt of provisioning
Call-Control Layer
(Softswitch)
AS or SCP
AS or SCP
SIP
TCAP
IP: SIP, SIP-T
MGC
• Resource mgmt
• Bearer control
• Call routing/translation
• IN/AIN
MGC
Control
Protocols
M3UA/SCTP
(Sigtran)
VoATM: BICC
TDM: ISUP, Q.931, CAS
Signaling Layer
• Signal processing
• Signal control
Inter-App Protocols
Signaling
Protocols
SG
MEGACO/H.248
SG
Media Layer
• Media processing
• Media control
• Tone & announcement
• QoS
2002-7-24
TDM, IP/RTP, ATM
MG
Media Transport
Krnet 2002
MG
124
Next Gen Network


One Network for all Service
특성





모든 형태의 서비스를 제공하기 위해서 새로운 제어, 관리 및
신호기술을 사용하는 packet 기반 네트워크
음성과 데이타망이 분리되지 않음.
다른 서비스에 대해서 Overlay망의 형태로 제공되는 것이
아님.
음성, 데이터, 멀티미디어가 IP 중심으로 전달되며, 각
미디어 특성에 맞는 QoS가 제공됨.
개방형 구조를 가진 플랫폼상에서 구현됨. 이때, 전송과
교환이 분리된 형태를 가짐.
2002-7-24
Krnet 2002
125
NGN Layered Architecture


separating control/services from transport functions
single packet based transport infrastructure (voice + data)
Softswitch
Network Service
Layer
Control Layer
Media Layer
Media Gateway
Access and Transport
Layer
Enterprise Customers
Remote Office/SOHO
2002-7-24
Krnet 2002
Mobile
Residential
Users
126
개방형 네트워크 기술표준화동향

MSF(Multiservice Switching Forum)



Telcodia, Cisco, MCI WorldCom등 14개 통신관련 회사를
주축으로 98년8월에 구성
ATM, Frame Relay, IP, 영상 서비스 등을 모두 하나의 전송
및 교환 인프라로 수용할 수 있는 방안에 대해서 reference
architecture를 제시하고 구성기능 및 기능간의 개방형
인터페이스에 대한 정의
ISC(International Soft Switch Consortium)


Voice over IP를 중심으로 Cisco, Lucent등과 같은 대형
통신업체와 Venture 기업까지 포함한 조직으로서 MGC(Call
Agent)의 architecture, 상호 연동성 등에 대한 활동
주로 Soft Switch를 개발 하거나 제품을 가진 업체들이 중심이
되어 활동
2002-7-24
Krnet 2002
127
MSF VoP Architecture
Service
Service
Agent
Applications Plane
SS7 Signaling
Gateway
Control
Plane
Call
Agent
Call Agent
Signalling
Controller
Proxy
Signaling
Switching
Plane
Switching Fabric
Adaptation
Plane
TGW
TGW
Voice TDM
2002-7-24
Voice TDM
Krnet 2002
128
An NGN VoP Architecture
Service
Agent
Call
Connection
Agent
SCP
IP Phones, PCs,
H.323 Terminals
STP
SS7
Gateway
Customer
Gateway
2002-7-24
Access
Network
Access
Gateway
Core Packet
Network
Voice Streams
Trunk
Gateway
NB
Trunks
Krnet 2002
LE
129
International Softswitch Consortium

목적 :



to support rapid advancement of application development
for the evolving Internet protocol networks which support
both voice and multimedia communications.
Internet protocol networks are built on distributed call control
servers generally called "call agents," "media gateway
controllers,” "softswitches," and "media gateways".
구성 :

1999.05. 창립, 2000.07. 현재 15여 기관 참여 중
• Cisco, HP, Lucent, Nortel, Telcordia 등


WG : Application, Architecture, Device Control, SIP, Session
Mn.
활동 사항 :

IP 망을 기반으로 기존 망과의 연동 기능에 대한 구조 제시
• VoIP
2002-7-24
Krnet 2002
130
Basic Softswitch Concepts

A conventional voice switch has three components:




Switching matrix
Line cards
Intelligence
In new voice networks:





The switching matrix is now the IP network
The line cards are now gateways
The intelligence is a softswitch
There is a single virtual distributed switch
The new distributed switch must communicate with legacy
switches
2002-7-24
Krnet 2002
131
SoftSwitch Model
Circuit Switch Model
SoftSwitch Model
Services
Services
Controller
*GCP
T
D
M
Time Slot
Interchange
Line
Card
2002-7-24
T
D
M
T
D
M
Trunk
Card
*GCP
T
D
M
Packet
Data
Backbone
Media
Gateway
Krnet 2002
Soft
Switch
Media
Gateway
132
Classic Softswitch
SS7 Network
SCP
SG
Local
Carrier
SG
Local
Carrier
IMT
MGC
Service Routing/Call Control/RM
IMT
MGCP/
MEGACO
Managed
Packet
Network
MG
ISDN PRI
MRS
FS
App
Server
MG
ISDN PRI
ISP B
PBX
Third Party
Apps
2002-7-24
Krnet 2002
133
Softswitch의 연동
Softswitch1
STP
SoftSwitch
Softswitch2
BICC
SIP-T
SoftSwitch
SS7
SIP
ISUP
ANSI/ITU
LE
C
MEGACO/H.248
Trunk
MG
Trunk
MG
IP/ATM
Access
MG
LE
C
DLC
Fax
SIP
2002-7-24
Krnet 2002
Fax
134
IP 기반 통합 서비스망 구조
wireless
network
wireless
access
sub mgmt
messaging
security
billing
network admin
sub mgmt
messaging
security
billing
network admin
sub mgmt
messaging
security
billing
network admin
Today’s Business
Environment
wireline
network
Internet
wireline
access
data
access
Next Generation Communications
Networks
intelligent unified
central
sub mgmt message security
central
billing
network
admin
Internet / packet network
(ATM / IP)
wireless
wired
data
Content-driven environments
 Seamless, integrated service
 Access distinctions minimized
 wireless and wireline
 voice and data

서비스 내용의 중복
 특정망에 적용된 컨텐츠

2002-7-24
Krnet 2002
135
Service Intelligent IP Network Vision
Application
Layer
Programmability
제3자
응용
응용
Hosting
메시징
응용
• 제3자 응용
• Web access
• Open APl's
Web 기반
서비스 선택
Application Mediation Layer
Service
Control
Layer
Network
Layer
IP Service and
Application Control
•
•
•
•
Policy Server
LDAP based
Soft
Switch
QoS
Authentication
Security
Multicast
Metro
Optical
RAS
DSL
Multimedia Call
Control
• VoIP and Video
• H.323/SIP
• MGCl (H.248)
IP
Service
Switch
lP/MPLS
Core
Aggregation
Network
Media
GW
PSTN
Cable
Frame/ATM
ASP
Wireless
2002-7-24
Internet
Enterprise
Krnet 2002
136
NexGen Service Architecture:
Service provider / ASP
application servers
Utility
Services
Communications
Services
Messaging
Services
Commerce
Services
Customer Profiles
Internet
Directory
Servers
Content
Services
Secure
Intranets
IP-based
Transport and Signaling
Wireless
voice/data
IN/AIN/WIN
Packet
Core
PSTN
2002-7-24
Wireless
Data
Wireless data
Wireline
voice
Web appliances
Entertainment
Services
Dialup/broadband
Packet voice
Krnet 2002
137
VoIP 응용분야
2002-7-24
Krnet 2002
138
VoIP 응용분야의 주요이슈

One Pipe access for all comm. Services
Unified IP infrastructure

VoDSL case




xDSL
VoDSL
Wireless Internet Case


GSM+GPRS
IMT-2000 ALL IP Network
2002-7-24
Krnet 2002
139
고속 인터넷 접속서비스
IAS: Internet Access Server
DSLAM: DSL Access Multiplexer
PSTN/ISDN
IAS
Modem
Data Network
DSLAM
ISP-1
POP
ISP-2
POP
ISP-3
음성과 데이터의 결합
- 접속망은 Hybrid
- 핵심망은 분리
ADSL
Modem
2002-7-24
POP
Krnet 2002
140
VoDSL (Voice over DSL)



음성과 데이터를 다중화하여, ATM over xDSL의 형식으로 전송
복수의 음성채널을 하나의 AAL2 VC로 다중화함.
데이터 채널은 AAL5 VC로 전송
Power
Spectrum
POTS
상
향
100 kHz
하향
Freq
1 MHz
ADSL frequency usage
2002-7-24
Voice Data
AAL2 AAL5
ATM
xDSL
Frequency
Non-voiceband frequency
Krnet 2002
141
VoDSL (Voice over DSL) 연결
V - IF
Transmitted by AAL2(I.366.2)
Subscriber
Switch
VoDSL
CLAD
IAD
DSLAM
LAN
ATM-SW
Router
ISP
VC for Voice
VC for IP
2002-7-24
VC for Voice and VC for IP
are separated by ATM Switch
Krnet 2002
142
제2단계 VoDSL
ATM-SW
IAD
DSLAM
Media GW
Controller
Media
Gateway
PSTN
Switch
Router
LAN
ISP


Access Gateway가 Media GW와 MGC로 대체됨.
MGC에서 교환기능을 수행함.
2002-7-24
Krnet 2002
143
VoDSL Solution Characteristics

VoDSL Solution Characteristics



Based on ATM, not on IP


Today supports up to 16 lines of toll-quality voice plus data
on as little as 384 kbps DSL connection
Leverages existing DSL deployments
(both ADSL and SDSL)
Voice packetization based on native ATM using AAL2
Why ATM?





ATM is there: most DSL is ATM-based
대역폭이 효율성이 우수함.
QoS가 제공되는 것이 입증되었음.
No security concerns (using PVCs)
Almost no local service providers looking for a VoIP solution
2002-7-24
Krnet 2002
144
Current VoDSL Network
Voice
Gateway
IAD
GR
303
Class 5
Switch
PSTN
xDSL
DSLAM
Packet
Backbone
xDSL
IAD
Broadband
Access
Server
ISP1
ISP2
IAD = Integrated Access Device
DSLAM = DSL Access Multiplexer
2002-7-24
Krnet 2002
145
GSM Architecture
GMSC
PSTN
A-bis
BTS
2002-7-24
„A‟
MSC
MAP
BSC
Krnet 2002
GPRS
Register
H/VLR
HLR/AUC
GPRS
Register
146
GPRS

GPRS(General Packet Radio Service)

3GPP packet data services standards
a packet-mode technique to transfer data and signaling
Applications based on standard data protocols and SMS
Interworking defined with IP networks and X.25

By adding GPRS functionality to the PLMN



• Optimizes the use of network and radio resources
• Value added services - internet
• Reasonable charging: amount of translated data, QoS,
connection time
2002-7-24
Krnet 2002
147
무선망에서의 인터넷접속구조(GPRS)
GMSC
PSTN
Circuit
Switched
Traffic
A-bis
BTS
„A‟
MSC
MAP
Peer
Elements
BSC
GPRS
Register
H/VLR
PCU
Gb
MSC : Mobile Switching Center
GMSC : Gateway MSC
PCU : Packet Control Unit
SGSN: serving GPRS support Node
GGSN: gateway GPRS support Node
2002-7-24
Packet
Traffic
MAP
SGSN
Gn
GGSN
Krnet 2002
HLR/AUC
GPRS
Register
Gi
Public
Switched
Packet Network
148
GSM/GPRS Network Configuration
MAP
BTS
BSC
HLR
MSC/
VLR
PSTN
BTS
BTS
Intranet
BSC
SGSN
BTS
GGSN
BSC
Internet
Radio Link
GTP
Tunnel
TCP/IP connection
.GPRS is a IP packet network for P-to-P packet data transportation
2002-7-24
Krnet 2002
149
VoIP over GPRS
End-to-end IP
codec
RTP
UDP
IP
codec
RTP
UDP
IP
회선교환
network
GW
BSS
codec
RTP
UDP
IP
2002-7-24
SGSN
IP
GGSN
Public
IP
Protocol stack
in the MS
codec
RTP
UDP
IP
Krnet 2002
150
VoIPoGPRS : 이용자 평면
CODEC
RTP
UDP
IP
IP
Relay
SNDCP
SNDCP
GTP
GTP
LLC
LLC
UDP /
TCP
UDP /
TCP
IP
IP
Relay
RLC
RLC
BSSGP
BSSGP
MAC
MAC
Network
Service
Network
Service
L2
L2
GSM RF
GSM RF
L1bis
L1bis
L1
L1
Um
MS
2002-7-24
Gb
BSS
Gn
SGSN
Krnet 2002
Gi
GGSN
151
VoIPoGPRS의 개념정리

VoIPoGPRS 은 GSM voice services을 대체하는 것은
아님.




VoIPoGPRS는 다음의 기능을 제공함.




No bandwidth gain on the radio interface
Lower speech quality (lower Codec quality, delay 와 loss 증가)
단말기가 변경되어야 하고, 게이트웨이 및 Call Agent 가 요구됨.
“click-and-talk”, “browse and phone” 등과 같은 멀티미디어
서비스와 결합기능제공
Particular long-distance tariff distortions
Integrated end-to-end multi-media 통신으로의 진화경로
실시간 패킷음성전달에 표준의 개발이 요구됨.



QoS renegotiation or multiple QoS per PDP-Context
Mobile constrained Coding-Scheme
New SNDCP features such as RTP/UDP/IP compression
2002-7-24
Krnet 2002
152
IMT-2000의 표준환경
Modular IMT-2000 Harmonization
(Terrestrial Component)
IMT-DS
(Direct Spread)
IMT-MC
(Multi-Carrier)
IMT-TC
(Time-Code)
IMT-SC
(Single Carrier)
IMT-FT
(Frequency-Time)
조각
2분기
1
3분기
4분기
Flexible connection between Radio modules
& Core Networks based on operator needs
Core Networks
Evolved
GSM (MAP)
Inter-Network Roaming
2002-7-24
Evolved
ANSI-41
IP-based
Networks
Network-to-Network Interfaces
Krnet 2002
153
IMT-2000의 All IP Network

ALL IP 망





IMT-2000 이동통신망을 IP기술로 구성하여
패킷망을 기반으로 하여
실시간, 비실시간 데이터를 동시에 서비스할 수 있도록 함.
패킷음성서비스, 멀티미디어 서비스 제공
All IP network의 특성





이동통신망과 인터넷의 결합
IP protocols을 사용하여 패킷전송
IP 기반의 호처리 프로토콜사용
IP 수용하는 단말사용
실시간 IP 기능을 가진 radio access network 및 Cable과
HIPERLAN을 포함한 다른 접속방식을 지원함.
2002-7-24
Krnet 2002
154
ALL IP Network의 목표

Goals of ALL IP Network






Seamless High-Speed Network, supporting a variety of End
to End Mobile Multimedia Services with IPv6 functions
High Quality (IP QoS)
Cost Reduction
Simple Mobility Management, only through IP Addressing
Open and Rapid Services Development Environment
Approach



Start point is 2G : separate voice and data with internet
access
3G Release 99 : gives a higher performance and some
important additional service capabilities
3G Releases 4 and 5 : gives the opportunity to transition to
integrated multimedia service
2002-7-24
Krnet 2002
155
ALL IP 망에서의 주요 이슈

IP Transport




이동성 관리



GPRS(3GPP) 및 PPP-MIP(3GPP2)에 기반한 망에서
진화함에 따른 망의 구조를 도출하고, 망기능요소를 정의하며
이들 요소들 사이에 인터페이스를 설계
무선접속망에 IP의 도입 (IP BTS)
전송기능과 제어기능을 분리하여 독립적으로 구현
음성 및 실시간 서비스에 패킷기술을 도입함으로써, Mobile
IP와 같은 이동성 관리 기능의 성능개선
핸드오버의 성능개선
QoS


end-to-end QoS를 위한 백본망의 개선
QoS 구조로서 RSVP 나 DiffServ 등의 도입방안
2002-7-24
Krnet 2002
156
ALL IP 망에서의 주요 이슈

VoIP



VoIP의 기능을 무선통신망에 도입(multimedia domain)
새로운 호제어, 미디어 제어기능을 핵심망의 요소로 포함
신속한 서비스의 도입

개방형 구조를 취함으로서 신속한 서비스의 생성 및 진화가
가능토록함.
2002-7-24
Krnet 2002
157
3GPP All IP의 개념
Release 99 Architecture - Hybrid
PSTN/ISDN
회선모드단말
Circuit domain
Iu-cs
UTRAN
패킷모드단말
Iu-ps
packet domain
Internet
•hybrid circuit/packet architecture
•2 separate domains - circuit and packet
Pure “All IP” Architecture
GW
회선모드단말
UTRAN
/
PSTN/ISDN
packet domain
Internet
Iu-ps
GERAN
packet mode
terminal
2002-7-24
long term vision
•call control H.323 or SIP
• no support for circuit mode terminals
Krnet 2002
158
3GPP All IP의 개념(2)
Pure “All IP” Architecture
GW
회선모드단말
UTRAN
/
PSTN/ISDN
packet domain
Internet
Iu-ps
GERAN
packet mode
terminal
Pure “All IP” CS option Architecture
회선모드단말
GW
UTRAN
/
GW
PSTN/ISDN
packet domain
Internet
Iu-ps
GERAN
packet mode
terminal
2002-7-24
Krnet 2002
159
3GPP All IP Network Architecture
Legacy mobile
signaling
Network
Applications
& Services
SCP
Alternative
Access
Network
R-SGW
Ms
Mh
Multimedia
IP Networks
CSCF
Mw
Mm
HSS
CAP
CSCF
Cx
Gr
TE
TE
Um
Iu-ps'
Iu
UTRAN
MT
R
Gc
Uu
Gn
SGSN
2002-7-24
SGSN
GGSN
Gn
Gp
Mg
MRF
Gi
ERAN
MT
R
Mr
Gi
Gf
Gi
MGCF
Gi
T-SGW
Mc
MGW
PSTN/
Legacy/External
EIR
GGSN
GPRS Based
Other PLMN
Signalling Interface
Signalling and Data Transfer Interface
Krnet 2002
160
New Functional Elements

Call State Control Function (CSCF)


Home Subscriber Server (HSS)






유선망과 신호연동
Roaming Signalling Gateway Function (R-SGW)
Media Gateway Control Function (MGCF)
Media Gateway Function (MGW)
Multimedia Resource Function (MRF)


HLR
Transport Signaling Gateway Function (T-SGW)


Call Agent
Intelligent Peripheral
MSC Server(for Option 2)
Gateway MSC Server(for Option 2
2002-7-24
Krnet 2002
161
IMT-2000 ALL IP – 망 참조모델
Legacy mobile network
MSC/VLR
HLR/HSS
TE
MT
R
Um
BS
BSC/
RNC
TE
Feature
server
legacy
Gateway
다양한 기술에 의한
무선접속망
BTS/Node B
MSC server
Signaling
Gateway
ISDN
PSTN
다양한
무선접속
기술에
대한
투명한
접속
인터페이스
Media Gateway
Controller
IP
Network
Media
Gateway
Gateway
router
Session
Control/
multimedia
call server
Other IP
Network
Operation/
Management/
Accounting/ Billing
/authentication
IP based Network / IP Multimedia Domain
2002-7-24
Krnet 2002
162
차세대 무선망의 개념
Services and
applications
download channel
New radio
interface
DAB
DVB
IP based core network
return channel:
e.g. GSM
cellular
GSM
IMT-2000
UMTS
Wireline
xDSL
WLAN
type
other
entities
short range
connectivity
2002-7-24
Krnet 2002
163
Beyond IMT-2000 System Overview
동기/ 비동기 3G Access
30Mbps 급
Radio Access
Um
cell
access
node
Multi-service
IP MM Subsystem
IP기반 3G/3.5G
Network
RAN
Servers
Legacy
Mobile Network
UE
PSTN/ISDN
All IP RAN
(high mobility)
Intelligent
Edge for
4G core
cell
Access
node
IPv6 기반 광대역
backbone network
IWU
4G Integrated
WLAN
AP
(low mobility)
AP
11Mbps 급
Radio Access
100Mbps 급
Radio Access
2002-7-24
Krnet 2002
광/IP 기반
초고속 기간망
Conventional
WLAN
(Internet Access)
164
감사합니다.
한국외국어대학교
정보통신공학과
김희동
2002-7-24
Krnet 2002
165
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement