1、COVERING NOTE GENERAL SECRETARIAT INTERNATIONAL TELECOMMUNICATION UNION Geneva, 4 February 2004 ITU -TELECOMMUNICATION STANDARDIZATION SECTOR Subject: Erratum 1 (02/2004) to ITU-T Recommendation Y. 126 1 (12/2002), Service requirements and architecture for voice services over Multi-Protocol Label Sw
2、itching In Figure II.lN.1261 - Alternate solutions for Voice Services over MPLS, in first service solution “voice over MPLS“, delete last line “AAL 1, AAL 2, AAL 5“ as shown below: Voice Services over Transport Network Union internationale des tlcommunications Place des Nations 121 1 GENVE 20 Suisse
3、 - Switzerland - Suiza INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TE LEC0 M M U N I CATI ON STANDARDIZATION SECTOR OF ITU Y.1261 (1 2/2002) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS Internet protocol aspects - Architecture, access, network capabilities and resource
4、management Service requirements and architecture for voice services over Multi-Protocol Label Switching ITU-T Recommendation Y. 1261 ITU-T Y-SENES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS GLOBAL INFORMATION INFRASTRUCTURE General Services, applications and midd
5、leware Network aspects Interfaces and protocols Numbering, addressing and naming Operation, administration and maintenance Security Performances General Services and applications INTERNET PROTOCOL ASPECTS Y. 1 OkY. 199 Y.20kY.299 Y.30kY.399 Y.40kY.499 Y.50kY.599 Y.60kY.699 Y.70kY.799 Y.80kY.899 Y. 1
6、 OOkY. 1 o99 Y.llOkY.1199 Architecture, access, network capabilities and resource management Y.1200-Y.1299 Transport Intenvorking Quality of service and network performance Signalling Operation, administration and maintenance Charging Y.130kY.1399 Y. 140kY. 1499 Y.150kY.1599 Y. 160kY. 1699 Y.17OkY.1
7、799 Y.180kY.1899 For further details, please refe. to the list of ITD-T Recommendations. 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
8、of Voice Services 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 1.366.2 Voice Trunking Format (based on ITU-T Rec. 1.366.2 adapted f
9、or MPLS). Possible 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 pro
10、cedure on 14 December 2002. ITU-T Rec. Y.1261 (12/2002) i 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 f
11、or studying technical, 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 stu
12、dy groups which, 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
13、 with IS0 and IEC. 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 th
14、is Recommendation 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 dat
15、e of approval of 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
16、 the TSB patent database. O 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) 11 CONTENTS Scope References . 2.1 Normative references 2.2 Informative references Definitions Abb
17、reviations Architecture 5.1 Voice Services over MPLS logical service reference model . 5.2 Voice services over MPLS Reference Architecture . Requirements for Voice Services over MPLS 6.2 User plane requirements . 6.3 User plane requirements for combined audio and video service 6.5 Management plane r
18、equirements 6.1 General service requirements . 6.4 Control plane requirements Voice Services over MPLS interworking requirements . 7.1 Voice Services over MPLS Interworking requirements with Voice over IP . 7.2 Voice Services over MPLS interworking requirements with Voice over ATM . 7.3 Voice Servic
19、es over MPLS interworking requirements with Voice over 7.4 7.5 Frame Relay Voice Services over MPLS interworking requirements with PSTNhSDN Voice Services over MPLS Interworking requirements with mobile access networks Appendix I . Voice over Packet Protocol architectures FR reference model and serv
20、ice description I . 1.3 Voice over Frame Relay user plane protocol stack 1.2 Voice over ATM as described in AAL type 2 Service Specific 1.2.1 User plane protocol stack for Voice over ATM as described in AAL 1.3 Voice over IP I . 1 I . 1.1 Voice over Frame Relay . I . 1.2 Multiplexing . Convergence S
21、ublayer for trunking 9 type 2 Service-Specific Convergence Sublayer for trunking 9 Page 1 1 1 2 2 3 3 4 5 5 5 6 6 7 7 7 7 7 7 7 8 8 8 8 9 10 10 11 11 . ITU-T Rec . Y.1261(12/2002) 111 Page Appendix II . Alternate solutions for Voice Services over MPLS II . 1 Voice over ATM . 11.2 Voice over IP II .
22、3 1.3 66.2 Voice Trunking format over MPLS . 11.4 Voice over MPLS . 11.5 Summary of different solutions for Voice Services over MPLS Appendix III . BICC architecture Appendix IV . Examples of Voice Services over MPLS deployment scenarios 12 12 13 13 13 14 14 15 iv ITU-T Rec . Y.1261(12/2002) ITU-T R
23、ecommendation Y.1261 Service requirements 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 inclu
24、de 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 1.366.2 Voice Trunking Format (based on ITU-T Rec. 1.366.2 adapted for MPLS). An overview of several possible approaches that have been proposed
25、as the basis for the family of protocols 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 ref
26、erences contain provisions which, 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 in
27、vestigate the possibility of applying 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
28、status of a Recommendation. Normative references ITU-T Recommendation G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T Recommendation G.723.1 (1 996), Speech coders: Dual rate speech coder for multimedia communications transmitting at 5.3 and 6.3 kbith. ITU-T Recommendation G.72
29、6 (1990), 40, 32, 24, 16 kbith Adaptive Dzferential Pulse Code Modulation (ADPCM) . ITU-T Recommendation G.729 (1996), Coding of speech at 8 kbith using conjugate- structure-algebraic-code-excited linear prediction (CS-A CELP). ITU-T Recommendation 1.361 (1 999), B-ISDN ATM layer speczjkation. ITU-T
30、 Recommendation 1.363.1 (1996), B-ISDNAdaptation Layer speczjkation: Type 1 AAL. ITU-T Recommendation 1.363.2 (2000), B-ISDN Adaptation Layer speczjkation: Type 2 AAL. ITU-T Recommendation 1.363.5 (1996), B-ISDNAdaptation Layer speczjkation: Type 5 AAL. ITU-T Recommendation 1.366.2 (2000), AAL type
31、2 service speczjk convergence sublayer for narrow-band services. ITU-T Recommendation 1.61 O (1 999), B-ISDN operation and maintenance principles and functions. ITU-T Rec. Y.1261(12/2002) 1 ITU-T Recommendation 4.922 (1992), ISDN data link layer specijkation for frame mode bearer services. ETSI TS 1
32、26 071 V3.0.1 (2000-02), Universal Mobile Telecommunications System (UMTS); AMR Speech Codec; General description. IETF RFC 303 1 (2001), Multiprotocol Label Switching Architecture. IETF RFC 3032 (2001), MPLS Label Stack encoding. IETF RFC 3036 (2001), LDP Speczjkation. IETF RFC 3270 (2002) Multi-Pr
33、otocol Label Switching WPLS). Support of Dzferentiated Services. Informative references ITU-T Recommendation Q. 1950 (2002), Bearer independent call bearer control protocol. IETF RFC (1996), RTP: A Transport Protocol For Real-Time applications. IETF RFC 1890 (1996), RTP Profile for Audio and Video C
34、onferences with Minimal Control. FRF. 1 1.1 (1999), Voice over Frame Relay Implementation Agreement. MPLS Forum 1 .O (2001), Voice over MPLS - Bearer Transport Implementation Agreement. Definitions This Recommendation defines the following terms: 3.1 voice services over MPLS: The term encompasses th
35、e 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. The classification is made by a Vo
36、ice 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, including voice and voiceband data. 3.4
37、 channel-associated signalling: Bits dedicated for connection control across a 1 544 kbith or 2048 kbith interface that carries 64 kbith channels. Procedures are based on the state of up to four signalling bits (A, B, C, D) that are allocated per channel per multifi-ame. 3.5 circuit mode data: A con
38、tinuous stream of digital information at 64 kbit/s or 2 x 64 kbith 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 established call. Depending on the syst
39、em, 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 fi-om the incoming analogue modulated signal, transporting this across a trunk in packet for
40、mats, 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 only be sent when 2 ITU-T Rec.
41、Y.1261(12/2002) 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 Transfer Mode BICC Bearer Independent Ca
42、ll 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 Media Gateway MGC Media Gateway Contr
43、oller 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 Time Division Multiplexing UDP Us
44、er Datagram Protocol 5 Architecture MPLS is being introduced into IP networks to support Trafic 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 by: a using label-switched-paths a
45、s a bearer capability for encoded voice thereby providing appropriate QoS capability; providing efficient transport mechanism. ITU-T Rec. Y.1261(12/2002) 3 5.1 A logical service reference model for Voice Services over MPLS consists of two main components: 1) 2) Voice Services over MPLS logical servi
46、ce reference model a high-capacity MPLS core network consisting of MPLS nodes (LSR) with support of MPLS control protocols; Gateway Devices used at the edge of the MPLS network to perform interworking between a variety of technologies such as ATM, fi-ame relay, TDM, IP, PSTN, ISDN, etc. and the MPLS
47、 network. Figure 1 shows the Voice Services over MPLS logical service reference model including control plane, transport plane, and management plane. Logical view Physical c.g. PSTN, ISDN, nctwork GW Gateway device - . - . - . - . - . Link 0 Label Edge Router . Label Switched Path # Label Switching
48、Router Figure 1N.1261- Voice Services over MPLS logical service reference model Y.1261-FOl 4 ITU-T Rec. Y.1261(12/2002) 5.2 Figure 2 identifies the Reference Architecture for Voice Services over MPLS. The MPLS network contains a number of Gateway devices (GY, Label Switching Routers (LSR), and Label
49、 Switched Paths (LSP) 13, 14, 15. An example LSP is shown as a solid line in the figure. Gateways may be directly connected to each other or indirectly connected through a number of LSRs. Voice services over MPLS Reference Architecture Gateway device Interworking Function - Label Switched Path _ Physical link Label Switching Router Y.1261-FO2 Figure 2N.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 confi
