1、 International Telecommunication Union ITU-T V.151TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (05/2006) SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Interworking with other networks Procedures for the end-to-end connection of analogue PSTN text telephones over an IP network utilizing
2、text relay ITU-T Recommendation V.151 ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK General V.1V.9 Interfaces and voiceband modems V.10V.34 Wideband modems V.35V.39 Error control V.40V.49 Transmission quality and maintenance V.50V.59 Simultaneous transmission of data a
3、nd other signals V.60V.99 Interworking with other networks V.100V.199 Interface layer specifications for data communication V.200V.249 Control procedures V.250V.299 Modems on digital circuits V.300V.399 For further details, please refer to the list of ITU-T Recommendations. ITU-T Rec. V.151 (05/2006
4、) i ITU-T Recommendation V.151 Procedures for the end-to-end connection of analogue PSTN text telephones over an IP network utilizing text relay Summary This Recommendation defines the inter-operation of two PSTN to IP Network gateways that facilitate the end-to-end connection of analogue text telep
5、hone terminals over an IP network utilizing text relay. Amendment 1 introduces Annex E, which defines the RTP payload format for the transport of text as T.140 character data over IP networks, removing the need to make a reference to an historic RFC published by the IETF. It also includes minor edit
6、orial changes throughout the document to make references to the newly introduced Annex, removing references to the RFC. Source ITU-T Recommendation V.151 was approved on 29 May 2006 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure. This release includes new Annex E in
7、troduced by V.151 (2006) Amendment 1, approved on 29 August 2007 by ITU-T Study Group 16 (2005-2008) under the ITU-T Recommendation A.8 procedure Keywords PSTN textphone, text over IP, text relay, text telephony, ToIP. ii ITU-T Rec. V.151 (05/2006) FOREWORD The International Telecommunication Union
8、(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 and tariff questions and issuing Recommendations on them with a view to stan
9、dardizing 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 Recommendations on these topics. The approval of ITU-T Recommendations is c
10、overed 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 Recommendation, the expression “Administration“ is used for conciseness to in
11、dicate 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. interoperability or applicability) and compliance with the Recommendation is achiev
12、ed 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 compliance with the Recommendation is required of any party. INTELLECTUAL P
13、ROPERTY 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, validity or applicability of claimed Intellectual Property Rights, whether ass
14、erted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned tha
15、t this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2008 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. V.151 (05/2006) iii CONTE
16、NTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 3 5 Introduction 4 5.1 Overview of Text over IP. 4 5.2 ToIP system architecture 4 5.3 Compliance requirements. 5 5.4 Relationship with other V.15x Recommendations. 5 6 Text telephone-over-IP functions . 6 7 Connection and network sce
17、narios . 6 7.1 Service and performance requirements for ToIP 7 7.2 Audio and text functionality. 7 8 Transport methods 8 8.1 Audio mode 8 8.2 VBD mode 8 8.3 Text relay mode 9 8.4 Switching between transport modes. 10 9 ToIP operational modes 11 10 Text Relay PHY layer operation. 12 11 IP transport f
18、or text relay 12 11.1 Single and dual port operation of text relay . 13 11.2 Text relay throughput . 13 12 Support of DTMF in ToIP 13 13 Transition out of text relay . 13 14 T.140 encoding of text relay. 14 14.1 Character set support 14 14.2 TIA-825A and T.50 encoding requirements 14 15 Gateway-to-g
19、ateway protocol definitions and procedures . 14 15.1 Gateway capability and call set-up messages. 14 15.2 Gateway call discrimination messages. 16 16 Start-up mode of operation . 16 16.1 Inter-relationship with V.150.1 16 16.2 Inter-relation with V.152 16 17 Voiceband data modem interworking require
20、ments. 17 18 Facsimile interworking requirements . 17 iv ITU-T Rec. V.151 (05/2006) Page 19 Call set-up procedures 17 20 Call discrimination procedures. 17 20.1 V.8 bis processing 17 20.2 V.8 CI/XCI processing . 17 20.3 Call discrimination overview . 18 20.4 Call discrimination SDL diagrams . 18 20.
21、5 Visual flow control. 32 Annex A Procedures for the optional support of SPRT protocol . 33 A.1 Overview 33 A.2 SDP negotiation 33 A.3 H.245 negotiation . 34 Annex B Definition of capabilities for use within H.245-based systems . 35 Annex C SDP description of sessions supporting V.151 39 Annex D Int
22、erworking IP text devices with V.151 gateways. 41 D.1 Introduction 41 D.2 Exchanging capabilities and opening media streams . 41 D.3 State transition and text handling . 42 Annex E Payload format and signaling syntax for real-time text transported within an audio stream 44 E.1 Overview 44 E.2 Payloa
23、d format 44 E.3 Use of redundancy 45 Appendix I Background to PSTN text telephony . 47 Appendix II ToIP call discrimination call flows. 48 II.1 Scope 48 II.2 Scenarios for call discrimination flows 48 II.3 Scenarios with SSE protocol being used 49 II.4 Scenarios with payload type switching being use
24、d 72 Appendix III The use of IETF RFC 2198 in ITU-T V.151 . 83 Appendix IV Text buffering and transmission . 84 Appendix V Probing sequence 85 Bibliography. 86 ITU-T Rec. V.151 (05/2006) 1 ITU-T Recommendation V.151 Procedures for the end-to-end connection of analogue PSTN text telephones over an IP
25、 network utilizing text relay 1 Scope This Recommendation defines the interoperation of two PSTN to IP Network gateways that facilitate the end-to-end connection of analogue text telephone terminals over an IP network. 2 References The following ITU-T Recommendations and other references contain pro
26、visions 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 investigate the possi
27、bility 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 status of a Recomme
28、ndation. ITU-T F.700 ITU-T Recommendation F.700 (2000), Framework Recommendation for multimedia services. ITU-T F.703 ITU-T Recommendation F.703 (2000), Multimedia conversational services. ITU-T G.177 ITU-T Recommendation G.177 (1999), Transmission planning for voiceband services over hybrid Interne
29、t/PSTN connections. ITU-T G.711 ITU-T Recommendation G.711 (1998), Pulse code modulation (PCM) of voice frequencies. ITU-T H.245 ITU-T Recommendation H.245 (2006), Control protocol for multimedia communication. ITU-T H.248.1 ITU-T Recommendation H.248.1 (2005), Gateway control protocol: Version 3. I
30、TU-T H.323 Ann.P ITU-T Recommendation H.323 (2003), Packet-based multimedia communications systems, Annex P: Transfer of modem signals over H.323. ITU-T V.8 ITU-T Recommendation V.8 (2000), Procedures for starting sessions of data transmission over the public switched telephone network. ITU-T V.8 bi
31、s ITU-T Recommendation V.8 bis (2000), Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCEs) and between data terminal equipments (DTEs) over the general switched telephone network and on leased point-to-point telephone-type c
32、ircuits. ITU-T V.18 ITU-T Recommendation V.18 (2000), Operational and interworking requirements for DCEs operating in the text telephone mode. ITU-T V.21 ITU-T Recommendation V.21 (1988), 300 bits per second duplex modem standardized for use in the general switched telephone network. ITU-T V.150.0 I
33、TU-T Recommendation V.150.0 (2003), Modem-over-IP networks: Foundation. 2 ITU-T Rec. V.151 (05/2006) ITU-T V.150.1 ITU-T Recommendation V.150.1 (2003), Modem-over-IP networks: Procedures for the end-to-end connection of V-series DCEs. ITU-T V.152 ITU-T Recommendation V.152 (2005), Procedures for sup
34、porting voice-band data over IP networks. IETF RFC 2198 IETF RFC 2198 (1997), RTP Payload for Redundant Audio Data. IETF RFC 2327 IETF RFC 2327 (1998), SDP: Session Description Protocol. IETF RFC 2733 IETF RFC 2733 (1999), An RTP Payload Format for Generic Forward Error Correction. IETF RFC 2833 IET
35、F RFC 2833 (2000), RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals. IETF RFC 3407 IETF RFC 3407 (2002), Session Description Protocol (SDP) Simple Capability Declaration. 3 Definitions This Recommendation defines the following terms: 3.1 Baudot: A five-bit code formerly used in Tel
36、etype machines including those text telephones that operate per TIA-825-A standard. The use of the term “Baudot“ in this Recommendation is expanded to also include the modulation used by text telephones complying with TIA-825-A. 3.2 constant carrier PTP: A PSTN Textphone (PTP) modulation that uses a
37、 carrier signal whose transmission is maintained in-between text spurts. Examples of constant carrier PTP modulations schemes include PTPs that utilize V.21 and V.23 modulations. Constant carrier modulations are also referred to as full duplex (FDX) modulations in this Recommendation. 3.3 gateway: A
38、 gateway converts media provided in one type of network to the format required in another type of network. For example, a gateway could terminate bearer channels from a switched circuit network (e.g., DS0s) and media streams from a packet network (e.g., RTP streams in an IP network). 3.4 IP text dev
39、ice: Native IP device that supports text communications and provides text communications interoperability with V.151-compliant gateways. Examples include IP-based IVR systems, voicemail systems, and IP phones. 3.5 non-constant carrier PTP: A PTP modulation that uses a carrier that is only transmitte
40、d during a text spurt (and possibly for a period before the text spurt as a preamble). An example of non-constant carrier PTP modulations schemes is that used by EDT-based PTP devices. Non-constant carrier modulations are also referred to as half-duplex (HDX) modulations in this Recommendation. 3.6
41、PSTN textphone: Term used in this Recommendation to represent all classes of text telephones, including TDD devices. 3.7 protocol conversion: The interworking of dissimilar PTP terminals performed by the ToIP gateways. 3.8 telecommunications terminal for the deaf: A term used in the USA for equipmen
42、t that provides text telephony. It is synonymous to text telephone. 3.9 text over IP: The dependable transport of analogue PSTN text telephones signals over IP networks using the methods and procedures as defined in this Recommendation. 3.10 text spurt: A sequence of one or more characters transmitt
43、ed in a text telephony signal without loss of carrier. ITU-T Rec. V.151 (05/2006) 3 3.11 text telephone mode: The operational mode when two devices are interconnected to provide text telephone communications. 3.12 text telephone: A device incorporating text telephony functions. 3.13 text telephony:
44、A telecommunications capability that supports real-time text conversation on communication networks. 3.14 voice-band data: The transport of modem signals over a voice channel of a packet network with the encoding appropriate for modem signals. 3.15 Conventions This Recommendation includes mandatory
45、requirements, recommendations and options; these are designated by the words “shall,“ “should,“ and “may“ respectively. A State Signalling Event (SSE) message is indicated using SSE:(), where is one of the defined media states and is the applicable reason code. 4 Abbreviations This Recommendation us
46、es the following abbreviations: ANS V.25 Answer Tone ASNam V.8 Answer Tone ASN.1 Abstract Syntax Notation One CI V.8 Call Indicator DS0 Digital Signal level 0 DCE Data Circuit-terminating Equipment (Modem) DTE Data Terminal Equipment FEC Forward Error Correction FDX Full Duplex FoIP Fax over Interne
47、t Protocol G1 On-Ramp Gateway G2 Off-Ramp Gateway HDX Half Duplex I1 Originating end-point IP Text telephone I2 Answering end-point IP Text telephone IP Internet Protocol IP-TLP IP Transport Layer Protocol ITD IP Text Device IVR Interactive Voice Response MoIP Modem over Internet Protocol PCM Pulse
48、Code Modulation PHY Physical transport layer of modem connection PSTN Public Switched Telephone Network 4 ITU-T Rec. V.151 (05/2006) PTP PSTN Textphone QoS Quality of Service RIC Reason Identifier Code RTP Real Time Protocol SPRT Simple Packet Relay Transport (Annex B of ITU-T V.150.1) SSE State Sig
49、nalling Events SSRC Synchronization Source T1 Originating end-point analogue PSTN Text Telephone T2 Answering end-point analogue PSTN Text Telephone TDD Telecommunications Devices for the Deaf TDM Time division multiplex(ing) ToIP Text Telephony over IP UDP User Datagram Protocol VBD Voice Band Data Mode VoIP Voice over Internet Protocol XCI Signal used in V.18 5 Introduction 5.1 Overview of Text over IP Text Telephony over IP (ToIP) is the dependable transport of analogue modulated signals generated by PSTN text tele
