1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T Y.1261TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2002) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS Internet protocol aspects Architecture, access, network capabilities and resource management Service requirements and
2、 architecture for voice services over Multi-Protocol Label Switching ITU-T Recommendation Y.1261 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Networ
3、k aspects Y.300Y.399 Interfaces and protocols Y.400Y.499 Numbering, addressing and naming Y.500Y.599 Operation, administration and maintenance Y.600Y.699 Security Y.700Y.799 Performances Y.800Y.899 INTERNET PROTOCOL ASPECTS General Y.1000Y.1099 Services and applications Y.1100Y.1199 Architecture, ac
4、cess, network capabilities and resource management Y.1200Y.1299 Transport Y.1300Y.1399 Interworking Y.1400Y.1499 Quality of service and network performance Y.1500Y.1599 Signalling Y.1600Y.1699 Operation, administration and maintenance Y.1700Y.1799 Charging Y.1800Y.1899 For further details, please re
5、fer to the list of ITU-T Recommendations. ITU-T Rec. Y.1261 (12/2002) i ITU-T Recommendation Y.1261 Service requirements and architecture for voice services over Multi-Protocol Label Switching Summary This Recommendation describes service requirements and architecture for transport of Voice Services
6、 over MPLS networks. Voice Services over MPLS networks include a family of protocols that may be supported over MPLS, including Voice over IP (as specified by IETF), Voice over MPLS (as specified by MPLS Forum) and I.366.2 Voice Trunking Format (based on ITU-T Rec. I.366.2 adapted for MPLS). Possibl
7、e approaches for transporting Voice Services over MPLS are provided in Appendix II. Detailed protocol specifications are subject of other Recommendations. Source ITU-T Recommendation Y.1261 was prepared by ITU-T Study Group 13 (2001-2004) and approved under the WTSA Resolution 1 procedure on 14 Dece
8、mber 2002. ii ITU-T Rec. Y.1261 (12/2002) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying tech
9、nical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which,
10、 in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IE
11、C. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendatio
12、n may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of
13、 this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent
14、database. ITU 2003 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. Y.1261 (12/2002) iii CONTENTS Page 1 Scope 1 2 References. 1 2.1 Normative references 1 2.2 Informative references 2 3 Definitions 2
15、 4 Abbreviations 3 5 Architecture 3 5.1 Voice Services over MPLS logical service reference model . 4 5.2 Voice services over MPLS Reference Architecture. 5 6 Requirements for Voice Services over MPLS 5 6.1 General service requirements . 5 6.2 User plane requirements. 6 6.3 User plane requirements fo
16、r combined audio and video service 6 6.4 Control plane requirements 7 6.5 Management plane requirements 7 7 Voice Services over MPLS interworking requirements . 7 7.1 Voice Services over MPLS Interworking requirements with Voice over IP. 7 7.2 Voice Services over MPLS interworking requirements with
17、Voice over ATM . 7 7.3 Voice Services over MPLS interworking requirements with Voice over Frame Relay 7 7.4 Voice Services over MPLS interworking requirements with PSTN/ISDN 7 7.5 Voice Services over MPLS Interworking requirements with mobile access networks 8 Appendix I Voice over Packet Protocol a
18、rchitectures 8 I.1 Voice over Frame Relay. 8 I.1.1 FR reference model and service description 8 I.1.2 Multiplexing . 9 I.1.3 Voice over Frame Relay user plane protocol stack 10 I.2 Voice over ATM as described in AAL type 2 Service Specific Convergence Sublayer for trunking 9 10 I.2.1 User plane prot
19、ocol stack for Voice over ATM as described in AAL type 2 Service-Specific Convergence Sublayer for trunking 9 11 I.3 Voice over IP 11 iv ITU-T Rec. Y.1261 (12/2002) Page Appendix II Alternate solutions for Voice Services over MPLS 12 II.1 Voice over ATM. 12 II.2 Voice over IP 13 II.3 I.366.2 Voice T
20、runking format over MPLS . 13 II.4 Voice over MPLS. 13 II.5 Summary of different solutions for Voice Services over MPLS 14 Appendix III BICC architecture 14 Appendix IV Examples of Voice Services over MPLS deployment scenarios 15 ITU-T Rec. Y.1261 (12/2002) 1 ITU-T Recommendation Y.1261 Service requ
21、irements and architecture for voice services over Multi-Protocol Label Switching 1 Scope The scope of this Recommendation is to describe services requirements and architecture for transport of Voice Services over MPLS networks. Voice Services over MPLS networks include a family of protocols that may
22、 be supported over MPLS, including Voice over IP (as specified by IETF), Voice over MPLS (as specified by MPLS Forum) and I.366.2 Voice Trunking Format (based on ITU-T Rec. I.366.2 adapted for MPLS). An overview of several possible approaches that have been proposed as the basis for the family of pr
23、otocols for transporting Voice services over MPLS is provided in Appendix II. Nothing in this Recommendation precludes the progression of all these protocols for the transport of Voice Services over MPLS. 2 References The following ITU-T Recommendations and other references contain provisions which,
24、 through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of appl
25、ying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. 2.1 N
26、ormative references 1 ITU-T Recommendation G.711 (1988), Pulse code modulation (PCM) of voice frequencies. 2 ITU-T Recommendation G.723.1 (1996), Speech coders: Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbit/s. 3 ITU-T Recommendation G.726 (1990), 40, 32, 24, 1
27、6 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM). 4 ITU-T Recommendation G.729 (1996), Coding of speech at 8 kbit/s using conjugate-structure-algebraic-code-excited linear prediction (CS-ACELP). 5 ITU-T Recommendation I.361 (1999), B-ISDN ATM layer specification. 6 ITU-T Recommendation I
28、.363.1 (1996), B-ISDN Adaptation Layer specification: Type 1 AAL. 7 ITU-T Recommendation I.363.2 (2000), B-ISDN Adaptation Layer specification: Type 2 AAL. 8 ITU-T Recommendation I.363.5 (1996), B-ISDN Adaptation Layer specification: Type 5 AAL. 9 ITU-T Recommendation I.366.2 (2000), AAL type 2 serv
29、ice specific convergence sublayer for narrow-band services. 10 ITU-T Recommendation I.610 (1999), B-ISDN operation and maintenance principles and functions. 2 ITU-T Rec. Y.1261 (12/2002) 11 ITU-T Recommendation Q.922 (1992), ISDN data link layer specification for frame mode bearer services. 12 ETSI
30、TS 126 071 V3.0.1 (2000-02), Universal Mobile Telecommunications System (UMTS); AMR Speech Codec; General description. 13 IETF RFC 3031 (2001), Multiprotocol Label Switching Architecture. 14 IETF RFC 3032 (2001), MPLS Label Stack encoding. 15 IETF RFC 3036 (2001), LDP Specification. 16 IETF RFC 3270
31、 (2002) Multi-Protocol Label Switching (MPLS). Support of Differentiated Services. 2.2 Informative references 17 ITU-T Recommendation Q.1950 (2002), Bearer independent call bearer control protocol. 18 IETF RFC (1996), RTP: A Transport Protocol For Real-Time applications. 19 IETF RFC 1890 (1996), RTP
32、 Profile for Audio and Video Conferences with Minimal Control. 20 FRF.11.1 (1999), Voice over Frame Relay Implementation Agreement. 21 MPLS Forum 1.0 (2001), Voice over MPLS Bearer Transport Implementation Agreement. 3 Definitions This Recommendation defines the following terms: 3.1 voice services o
33、ver MPLS: The term encompasses the set of technical approaches used to transport encoded voice over MPLS. This terminology is independent of the method by which MPLS frames are transported. 3.2 active voice: A sampled audio interval that has been determined to contain speech as opposed to silence. T
34、he classification is made by a Voice Activity Detection algorithm. It enables discontinuous transmission, whereby the bit rate of the signal is reduced during silent intervals. 3.3 audio: In the context of this Recommendation, audio is used as a general term for signals of the audible medium, includ
35、ing voice and voiceband data. 3.4 channel-associated signalling: Bits dedicated for connection control across a 1544 kbit/s or 2048 kbit/s interface that carries 64 kbit/s channels. Procedures are based on the state of up to four signalling bits (A, B, C, D) that are allocated per channel per multif
36、rame. 3.5 circuit mode data: A continuous stream of digital information at 64 kbit/s or 2 64 kbit/s having an 8 kHz structure. 3.6 dialled digits: Multifrequency audio tones typically used for inter-register signalling of addresses during call set-up or for end-to-end device control during an establ
37、ished call. Depending on the system, codes are defined for the digits 0-9 of a telephone keypad and other auxiliary signals. 3.7 facsimile demodulation/remodulation: The process of detecting facsimile traffic, extracting digital information from the incoming analogue modulated signal, transporting t
38、his across a trunk in packet formats, and reproducing the facsimile control and image information by remodulation at the other end. 3.8 silence insertion descriptor: A compressed representation of the audio background noise that can be sent during silent intervals. SIDs may not be continuous and may
39、 only be sent when ITU-T Rec. Y.1261 (12/2002) 3 there is a change in noise characteristics. Playing out received SIDs is known as Comfort Noise Generation. 4 Abbreviations This Recommendation uses the following abbreviations: AAL ATM Adaptation Layer AMR Adaptive Multi-Rate ATM Asynchronous Transfe
40、r Mode BICC Bearer Independent Call Control CAS Channel-Associated Signalling CPCS Common Part Convergence Sublayer DTMF Dual-Tone Multi-Frequency GW Gateway IP Internet Protocol ISDN Integrated Services Digital Network LER Label Edge Router LSP Label Switched Path LSR Label Switching Router MG Medi
41、a Gateway MGC Media Gateway Controller MPLS Multi-Protocol Label Switching MSC Mobile Switching Center MTU Maximum Transmission Unit NT Network Termination PSTN Public Switched Telephone Network RAN Radio Access Network RTP Real-Time Transport Protocol SSCS Service-Specific Convergence Sublayer TDM
42、Time Division Multiplexing UDP User Datagram Protocol 5 Architecture MPLS is being introduced into IP networks to support Traffic Engineering and various applications. One of the motivations for Voice Services over MPLS is to take advantage of the MPLS network capabilities to improve voice services
43、by: using label-switched-paths as a bearer capability for encoded voice thereby providing appropriate QoS capability; providing efficient transport mechanism. 4 ITU-T Rec. Y.1261 (12/2002) 5.1 Voice Services over MPLS logical service reference model A logical service reference model for Voice Servic
44、es over MPLS consists of two main components: 1) a high-capacity MPLS core network consisting of MPLS nodes (LSR) with support of MPLS control protocols; 2) Gateway Devices used at the edge of the MPLS network to perform interworking between a variety of technologies such as ATM, frame relay, TDM, I
45、P, PSTN, ISDN, etc. and the MPLS network. Figure 1 shows the Voice Services over MPLS logical service reference model including control plane, transport plane, and management plane. GWY.1261_F01e.g. PSTN, ISDN,ATMe.g. PSTN, ISDN,ATMControl planeUser planeManagement plane Management networkControl pl
46、aneUser planeManagement planeTransport networkSignalling networkGW GWGW GWMPLS networkLinkLabel Edge RouterLabel Switched PathLabel Switching RouterGateway deviceLogicalviewPhysicalnetworkFigure 1/Y.1261 Voice Services over MPLS logical service reference model ITU-T Rec. Y.1261 (12/2002) 5 5.2 Voice
47、 services over MPLS Reference Architecture Figure 2 identifies the Reference Architecture for Voice Services over MPLS. The MPLS network contains a number of Gateway devices (GW), Label Switching Routers (LSR), and Label Switched Paths (LSP) 13, 14, 15. An example LSP is shown as a solid line in the
48、 figure. Gateways may be directly connected to each other or indirectly connected through a number of LSRs. Y.1261_F02GWGWGWGWIWFIWFIWFIWFVoice terminalPSTN, ISDN, ATM PSTN, ISDN, ATMGWIWFGateway deviceInterworking FunctionLabel Switched PathPhysical linkLabel Switching RouterMPLS networkFigure 2/Y.
49、1261 Voice services over MPLS Reference Architecture Gateway devices include LER functionality as well as the interworking functions. This architecture should be capable of supporting different LSP configurations (e.g., E-LSP, L-LSP 16, hierarchical LSP, etc.) to convey voice payloads in an MPLS environment. NOTE Voice Services over MPLS can be deployed in both core and access networks. Network architecture functions and definitions for the usage of Voice Services over MPLS in access networks are
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