1、 International Telecommunication Union ITU-T Y.1454TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2006) SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS Internet protocol aspects Interworking Tandem free operation (TFO) IP network interworking
2、User plane interworking ITU-T Recommendation Y.1454 ITU-T Y-SERIES RECOMMENDATIONS GLOBAL INFORMATION INFRASTRUCTURE, INTERNET PROTOCOL ASPECTS AND NEXT-GENERATION NETWORKS GLOBAL INFORMATION INFRASTRUCTURE General Y.100Y.199 Services, applications and middleware Y.200Y.299 Network aspects Y.300Y.39
3、9 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, access, network capab
4、ilities 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 NEXT GENERATION NETWORKS Frameworks and functiona
5、l architecture models Y.2000Y.2099 Quality of Service and performance Y.2100Y.2199 Service aspects: Service capabilities and service architecture Y.2200Y.2249 Service aspects: Interoperability of services and networks in NGN Y.2250Y.2299 Numbering, naming and addressing Y.2300Y.2399 Network manageme
6、nt Y.2400Y.2499 Network control architectures and protocols Y.2500Y.2599 Security Y.2700Y.2799 Generalized mobility Y.2800Y.2899 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. Y.1454 (12/2006) i ITU-T Recommendation Y.1454 Tandem free operation (TFO) IP network in
7、terworking User plane interworking Summary This Recommendation focuses on required functions for network interworking of tandem free operation, specifically the user plane interworking mechanisms and procedures for transport. It specifies a list of requirements, interworking scenarios and interworki
8、ng encapsulation formats and semantics for TFO-IP network interworking. Source ITU-T Recommendation Y.1454 was approved on 14 December 2006 by ITU-T Study Group 13 (2005-2008) under the ITU-T Recommendation A.8 procedure. Keywords Gateway, interworking, IWF, RTP, tandem free operation (TFO). ii ITU-
9、T Rec. Y.1454 (12/2006) 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 technical, operating a
10、nd 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, in turn, produce
11、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 IEC. NOTE In this Re
12、commendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interope
13、rability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that
14、compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, val
15、idity 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 this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be req
16、uired to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be reprodu
17、ced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. Y.1454 (12/2006) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 3.1 Terms defined elsewhere 2 3.2 Terms defined in this Recommendation. 2 4 Abbreviations 3 5 Conventions 4 6 TFO-IP interworking 4 7 Gen
18、eral requirements 6 7.1 User plane requirements. 6 7.2 Control plane aspects 7 7.3 Fault management aspects 8 7.4 Traffic management aspects. 8 7.5 Connection admission control for IWF 8 8 Functional group considerations for TFO-IP network interworking 9 8.1 Overview 9 8.2 Transport label 11 8.3 Int
19、erworking label 11 8.4 Common interworking indicators. 11 8.5 Optional timing information. 11 9 Payload formats 11 10 Timing aspects 12 11 Packet loss aspects 12 12 Security considerations. 12 Appendix I Voice-TFO transitioning state diagrams 13 Appendix II Differences between TFO-IP modes of operat
20、ion 15 Bibliography 16 ITU-T Rec. Y.1454 (12/2006) 1 ITU-T Recommendation Y.1454 Tandem free operation (TFO) IP network interworking User plane interworking 1 Scope This Recommendation focuses on required functions for network interworking of tandem free operation (TFO) ETSI TS 123053, ETSI TS 12315
21、3, ETSI TR 123977 and ETSI TS 128062 and IP, specifically the user plane interworking mechanisms and procedures for transport. In particular it specifies a list of requirements, interworking scenarios and interworking encapsulation formats and semantics for TFO-IP network interworking. Since TDM con
22、nections are inherently point-to-point, this interworking defines a single connection between two interworking functions (IWFs). TFO-IP denotes network interworking between “TFO-over-TDM“ networks and “TFO-over-IP“ networks. Particularly: TFO/TDM interfaces without any specific transport mechanisms
23、(like GSM Ater interface) below the TFO protocol; and interworking to TFO/IP interfaces without any mobile-specific transport mechanisms like ETSI framing protocols ETSI TS 125415 and ETSI TS 129415. Use of ETSI framing protocols is excluded from consideration in this Recommendation. The TFO-IP inte
24、rworking function (IWF) is a new and specific type of in path equipment (IPE) form TFO endpoint perspective ETSI TS 128062. This Recommendation may not be suitable for use by recognized operating agencies due to possible degradation of network synchronization performance as compared with native TDM
25、transport. 2 References The following ITU-T Recommendations and other references 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
26、 to revision; users of this Recommendation are therefore encouraged to investigate 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 wit
27、hin this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.711 ITU-T Recommendation G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T G.799.1 ITU-T Recommendation G.799.1/Y.1451.1 (2004), Functionality and interface specifications
28、 for GSTN transport network equipment for interconnecting GSTN and IP networks. ITU-T G.809 ITU-T Recommendation G.809 (2003), Functional architecture of connectionless layer networks. ITU-T H.248.1 ITU-T Recommendation H.248.1 (2005), Gateway control protocol: Version 3. ITU-T Y.1413 ITU-T Recommen
29、dation Y.1413 (2004), TDM-MPLS network interworking User plane interworking. IETF RFC 3261 IETF RFC 3261 (2002), SIP: Session Initiation Protocol. 2 ITU-T Rec. Y.1454 (12/2006) IETF RFC 3550 IETF RFC 3550 (2003), RTP: A Transport Protocol for Real-Time Applications. IETF RFC 3551 IETF RFC 3551 (2003
30、), RTP Profile for Audio and Video Conferences with Minimal Control. IETF RFC 4040 IETF RFC 4040 (2005), RTP Payload Format for a 64 kbit/s Transparent Call. IETF RFC 4566 IETF RFC 4566 (2006), SDP: Session Description Protocol. ETSI TR 123977 ETSI TR 123.977 V6.1.0 (2005), Universal Mobile Telecomm
31、unications System (UMTS); Bandwidth And Resource Savings (BARS) and speech enhancements for Circuit-Switched (CS) networks. ETSI TS 122053 ETSI TS 122.053 V6.0.0 (2004), Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); Tandem Free Operation (T
32、FO); Service description. ETSI TS 123053 ETSI TS 123.053 V6.0.0 (2004), Digital cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System (UMTS); Tandem Free Operation (TFO); Service description. ETSI TS 123153 ETSI TS 123.153 V6.3.0 (2005), Universal Mobile Telecommu
33、nications System (UMTS); Out-of-band transcoder control; Stage 2. ETSI TS 125415 ETSI TS 125.415 V7.3.0 (2006), Universal Mobile Telecommunications System (UMTS); UTRAN Iu interface user plane protocols. ETSI TS 128062 ETSI TS 128.062 V6.3.0 (2006), Digital cellular telecommunications system (Phase
34、2+); Universal Mobile Telecommunications System (UMTS); Inband Tandem Free Operation (TFO) of speech codecs; Service description. ETSI TS 129415 ETSI TS 129.415 V6.1.0 (2006), Universal Mobile Telecommunications Systems (UMTS); Core network Nb interface user plane protocols. 3 Definitions 3.1 Terms
35、defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 egress IWF: See ITU-T Y.1413. 3.1.2 ingress IWF: See ITU-T Y.1413. 3.1.3 TFO frame ETSI TS 128062: A speech frame exchanged between transcoders when tandem free operation is active. 3.1.4 tandem free operation ET
36、SI TS 128062: A call configuration where no transcoder device is physically present and hence no control or conversion or other functions associated with it are activated. 3.1.5 TFO speech frame ETSI TS 128062: A speech frame exchanged between transcoders when tandem free operation is active. 3.1.6
37、transcoder ETSI TS 128062: A device that converts the encoding of information from one particular scheme to a different one. 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: ITU-T Rec. Y.1454 (12/2006) 3 3.2.1 TFO message: A TFO protocol signalling message wh
38、ich is exchanged between two participating codecs used to provide TFO. 3.2.2 TFOoIP (TFO-over-IP): This term is used to refer to the transport of TFO signals over a voice channel of an IP packet network with the encoding appropriate for TFO signals. NOTE 1 TFOoIP capable gateways provide the means t
39、o provide this transport. NOTE 2 A gateway is not responsible for the overall gateway-to-gateway performance, but may be configured to best mitigate the effects of the connected packet network impairments. 3.2.3 TFO service endpoint: The functional entity where the inband signalling (IS) and TFO pro
40、tocol endpoints are located. 4 Abbreviations This Recommendation uses the following abbreviations: 2GMS 2nd Generation Mobile System (e.g., GSM) 3GMS 3rd Generation Mobile System (e.g., UMTS) AAL1 ATM Adaptation Layer type 1 AAL2 ATM Adaptation Layer type 2 ATM Asynchronous Transfer Mode BER Bit Err
41、or Rate BS Base Station BSC Base Station Controller CAC Connection Admission Control CMD Clearmode IETF RFC 4040 CMDTFOTFO-aware Clearmode GoS Grade of Service GSM Global System for Mobile Communications IPE In Path Equipment IS Inband Signalling N-ISDN Narrowband Integrated Services Digital Network
42、 IWF Interworking Function MG Media Gateway QoS Quality of Service PLC Packet Loss Concealment PT Payload Type (RTP) RN Radio Network RNC Radio Network Controller RTP Real-time Transport Protocol RTP/AVP RTP Profile “AVP“ IETF RFC 3551 SS Silence Suppression TDM Time Division Multiplexing 4 ITU-T Re
43、c. Y.1454 (12/2006) TFO Tandem Free Operation (also known as “Vocoder Bypass“, “Codec-Bypass“, or “Transcoder-Through“) TFO-IP IWF interconnecting TFO/TDM with TFO/IP domains TRAU Transcoder and Rate Adaptor Unit TrFO Transcoder Free Operation UMTS Universal Mobile Telecommunications System VBD Voic
44、eband Data b-ITU-T V.152 VBDoIP VBD over IP VBDTFO TFO-aware VBD mode Vccompressed voice mode Vcfixed Vc mode with compressing codecs designed initially for fixed networks or wireline terminals (e.g., G.729, G.726 and G.723.1) Vcmobile Vc mode with compressing codecs designed initially for mobile ne
45、tworks (e.g., GSM codecs, AMR) VoIP Voice over IP Vuuncompressed Voice mode VuSS uncompressed Voice with silence suppression mode Vuw/oSS uncompressed Voice without silence suppression mode VuTFO TFO-transparent, uncompressed Voice mode 5 Conventions This Recommendation uses traditional terminology
46、concerning tandem free operation (TFO) in the same manner as corresponding standards defined for PLMNs such as used in ANSI or ETSI, or defined particularly for NGNs such as those in ITU-T G.799.1. The terms TFO frame and TFO speech frame are used in the context of clause 5 of ETSI TS 128062 and the
47、 term TFO message is used in the context of clause 7 of ETSI TS 128062. 6 TFO-IP interworking There is a need for network interworking between IP domains (for VoIP NGNs) and TDM networks carrying TFO signals in 64 kbit/s TDM bearer connections in the user plane. Such an interworking function (IWF) s
48、hall be denoted as TFO-to-IP user plane IWF. Such an IWF may be provided by various network element types. The VoIP H.248 media gateway ITU-T H.248.1 is a candidate for such an IWF type (see Figure 6-1). ITU-T Rec. Y.1454 (12/2006) 5 Figure 6-1 Reference architecture (1) for TFO-IP network interwork
49、ing Figure 6-2 provides general network architecture for TFO-IP network interworking where TDM networks are interconnected through an IP network. The TDM network segments are bounded by TFO service endpoints in the scope of this Recommendation. For the TFO-to-IP direction, the continuous TDM stream is segmented and encapsulated into RTP/UDP/IP packets by the interworking function (IWF). For the IP-to-TDM direction, the TDM segments are extracted from the RTP/UDP
