1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T V.8 bis TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (11/2000) SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK General Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCE
2、s) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits ITU-T Recommendation V.8 bis (Formerly CCITT Recommendation) ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK General V.1V.9 Inte
3、rfaces 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 and other signals V.60V.99 Interworking with other networks V.100V.199 Interface layer specifications for data communication V.200V.249
4、 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 V.8 bis (11/2000) i ITU-T Recommendation V.8 bis Procedures for the identification and selection of common modes of operation between data circuit-termin
5、ating equipments (DCEs) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits Summary This Recommendation defines signals, messages and the procedures for exchanging these over the PSTN and on leased point-to-point
6、 telephone-type circuits, for the identification and selection of common modes of operation between Data Circuit-terminating Equipments (DCEs) and Data Terminal Equipments (DTEs). These are used when the modes of operation of DCEs and DTEs communicating over the connection need to be automatically e
7、stablished and selected, but before signals are exchanged which are specific to a particular Recommendation. Considerations are included for the standard analogue telephony mode of operation. Revision 2 of this Recommendation adds support for PCM Modems, as described in ITU-T V.90, V.91 and V.92. So
8、urce ITU-T Recommendation V.8 bis was revised by ITU-T Study Group 16 (2001-2004) and approved under the WTSA Resolution 1 procedure on 17 November 2000. ii ITU-T V.8 bis (11/2000) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telec
9、ommunications. 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 standardizing telecommunications on a worldwide basis. The World Telecom
10、munication 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 covered by the procedure laid down in WTSA Resolution 1. In some area
11、s 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 indicate both a telecommunication administration and a recognized oper
12、ating agency. 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, validity or applicability of claimed Intellectual
13、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 received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, im
14、plementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including ph
15、otocopying and microfilm, without permission in writing from ITU. ITU-T V.8 bis (11/2000) iii CONTENTS Page 1 Scope. 1 2 References. 1 3 Definitions 3 4 Abbreviations 3 5 Overview of this Recommendation 4 6 Description of signals and messages 5 6.1 Escape Signal (ES) 5 6.2 Mode Request (MR) . 5 6.3
16、Capabilities Request (CR) 5 6.4 Mode Select (MS). 5 6.5 Capabilities List (CL) . 5 6.6 Capabilities List Request (CLR). 5 6.7 Acknowledge Message (ACK) . 5 6.8 Negative Acknowledge Message (NAK) . 6 7 Structure of signals and messages 6 7.1 Signals. 6 7.1.1 Frequencies 6 7.1.2 Duration. 7 7.1.3 Tole
17、rances 7 7.1.4 Transmitted power levels. 7 7.2 Messages. 7 7.2.1 Transmitted power level 7 7.2.2 Format convention. 7 7.2.3 Frame structure 8 7.2.4 Preamble 9 7.2.5 Flag sequence 9 7.2.6 Information field 9 7.2.7 Frame check sequence field. 9 7.2.8 Transparency . 9 7.2.9 Invalid frames 10 8 Informat
18、ion field coding format . 10 8.1 General 10 8.2 Coding format for parameters in the I and S fields. 10 8.2.1 Parameter classification. 10 8.2.2 Order of transmission of parameters . 11 iv ITU-T V.8 bis (11/2000) Page 8.2.3 Delimiting and parsing of data blocks. 12 8.3 Identification field (I) 13 8.3
19、.1 Message type . 13 8.3.2 Revision number 14 8.3.3 Parameter field. 14 8.4 Standard information field (S) 15 8.4.1 ACK and NAK messages 15 8.4.2 MS, CL, and CLR messages 16 8.5 Non-standard information field (NS) 23 8.6 Information field length 23 9 V.8 bis transactions. 24 9.1 Permitted V.8 bis tr
20、ansactions 24 9.2 Transactions permitted at any time on the PSTN and on leased point-to-point circuits. 25 9.2.1 Transactions with no a priori knowledge of V.8 bis support 25 9.2.2 Transactions with a priori knowledge of V.8 bis capability . 26 9.3 Transactions permitted only upon automatic answerin
21、g of a PSTN call 26 9.4 Use of escape signals 26 9.5 Use of the Negative Acknowledge Message (NAK) 26 9.6 State transition diagrams. 27 9.7 Suppression of ACK(1) after an MS message 28 9.8 Error recovery. 29 9.9 Procedures for initiating a modem start-up after a V.8 bis transaction 29 9.9.1 V.8 star
22、t-up following a V.8 bis transaction 29 9.9.2 Shortened V.8 start-up following a V.8 bis transaction 30 9.9.3 V.25 start-up following a V.8 bis transaction 31 9.10 Message segmentation 31 10 Operating procedures 32 10.1 Operating procedures when not automatically answering on the PSTN and on leased
23、point-to-point circuits 32 10.1.1 Initiating station (MR or CR initiation). 32 10.1.2 Initiating station (MS, CL or CLR) . 32 10.1.3 Responding station 32 10.2 Operating procedures upon automatic answering of a call on the PSTN . 32 10.2.1 Calling station 32 10.2.2 Answering station (MReor CReinitia
24、tion) . 33 10.2.3 Answering station (MS, CL or CLR initiation). 34 ITU-T V.8 bis (11/2000) v Page 11 DTE-DCE interface 34 Appendix I Recommendation V.8 bis features. 34 I.1 Introduction. 34 I.2 Basic features of this Recommendation 34 I.3 Selection of a desired communication mode 35 I.4 Identificati
25、on of common operating modes 35 I.5 Automatic selection between terminals 35 I.6 User-friendly switching from telephony to data . 35 I.7 Conferencing applications 36 I.8 Interworking considerations . 36 I.9 Relationship between ITU-T V.8 and V.8 bis 36 Appendix II Examples of V.8 bis transactions .
26、37 Appendix III Effect of echo suppressors 41 III.1 Introduction. 41 III.2 Operation of echo suppressors 41 III.3 Dual tone signal breakthrough of echo suppressors . 42 III.4 V.8 bis transactions 4, 5 and 6 43 III.5 Automatic answering together with a voice recording device 44 III.5.1 Blocking of V.
27、8 bis initiating signals 44 III.5.2 Blocking of response to MReand CReby OGM. 45 III.6 Optional status of provisions 46 ITU-T V.8 bis (11/2000) 1 ITU-T Recommendation V.8 bis Procedures for the identification and selection of common modes of operation between data circuit-terminating equipments (DCE
28、s) and between data terminal equipments (DTEs) over the public switched telephone network and on leased point-to-point telephone-type circuits 1 Scope This Recommendation defines signals, messages and procedures for exchanging these over the PSTN and on leased point-to-point telephone-type circuits,
29、 when the modes of operation of DCEs and DTEs communicating over the connection need to be automatically established and selected, but before signals are exchanged which are specific to a particular Recommendation. Considerations are included for the standard analogue telephony mode of operation. Th
30、e current revision number of this Recommendation is 2. The principal characteristics of this Recommendation are as follows: a) use over the PSTN or on leased telephone-type circuits; b) use at call establishment on the PSTN upon automatic answering; c) use after PSTN call establishment when the circ
31、uit is in telephony mode; d) provisions to exchange capabilities information for identifying common modes of operation between DCEs and between DTEs; e) provisions for a DCE to request the remote DCE to initiate a common mode of operation: mode determination by the calling station upon automatic ans
32、wering at PSTN call establishment; mode determination by the answering station upon automatic answering at PSTN call establishment; and mode determination after circuit establishment by either station; f) provisions to prevent inadvertent disconnection of calls or annoying disturbance to users who m
33、ay not have V.8 bis capability or be aware of V.8 bis procedures. 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 vali
34、d. All Recommendations and other references are subject 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
35、is regularly published. ITU-T H.324 (1998), Terminal for low bit-rate multimedia communication. ITU-T T.30 (1999), Procedures for document facsimile transmission in the general switched telephone network. ITU-T T.35 (2000), Procedure for the allocation of ITU-T defined codes for non-standard facilit
36、ies. ITU-T T.84 (1996) | ISO/IEC 10918-3:1997, Information technology Digital compression and coding of continuous-tone still images: Extensions. 2 ITU-T V.8 bis (11/2000) ITU-T T.120 (1996), Data protocols for multimedia conferencing. ITU-T T.434 (1999), Binary file transfer format for the telemati
37、c services. ITU-T V.8 (2000), Procedures for starting sessions of data transmission over the public switched telephone network. ITU-T V.14 (1993), Transmission of start-stop characters over synchronous bearer channels. ITU-T V.18 (2000), Operational and interworking requirements for DCEs operating i
38、n the text telephone mode. ITU-T V.21 (1988), 300 bits per second duplex modem standardized for use in the general switched telephone network. ITU-T V.22 (1988), 1200 bits per second duplex modem standardized for use in the general switched telephone network and on point-to-point 2-wire leased telep
39、hone-type circuits. ITU-T V.22 bis (1988), 2400 bits per second duplex modem using the frequency division technique standardized for use on the general switched telephone network and on point-to-point 2-wire leased telephone-type circuits. ITU-T V.23 (1988), 600/1200-baud modem standardized for use
40、in the general switched telephone network. ITU-T V.32 (1993), A family of 2-wire, duplex modems operating at data signalling rates of up to 9600 bit/s for use on the general switched telephone network and on leased telephone-type circuits. ITU-T V.32 bis (1991), A duplex modem operating at data sign
41、alling rates of up to 14 400 bit/s for use on the general switched telephone network and on leased point-to-point 2-wire telephone-type circuits. ITU-T V.34 (1998), A modem operating at data signalling rates of up to 33 600 bit/s for use on the general switched telephone network and on leased point-
42、to-point 2-wire telephone-type circuits. ITU-T V.42 (1996), Error-correcting procedures for DCEs using asynchronous-to-synchronous conversion. ITU-T V.42 bis (1990), Data compression procedures for data circuit-terminating equipment (DCE) using error correction procedures. ITU-T V.61 (1996), A simul
43、taneous voice plus data modem, operating at a voice plus data signalling rate of 4800 bit/s, with optional automatic switching to data-only signalling rates of up to 14 400 bit/s, for use on the General Switched Telephone Network and on leased point-to-point 2-wire telephone type circuits. ITU-T V.7
44、0 (1996), Procedures for the simultaneous transmission of data and digitally encoded voice signals over the GSTN, or over 2-wire leased point-to-point telephone-type circuits. ITU-T V.76 (1996), Generic multiplexer using V.42 LAPM-based procedures. ITU-T V.80 (1996), In-band DCE control and synchron
45、ous data modes for asynchronous DTE. ITU-T V.90 (1998), A digital modem and analogue modem pair for use on the Public Switched Telephone Network (PSTN) at data signalling rates of up to 56 000 bit/s downstream and up to 33 600 bit/s upstream. ITU-T V.8 bis (11/2000) 3 ITU-T V.91 (1999), A digital mo
46、dem operating at data signalling rates of up to 64 000 bit/s for use in a 4-wire circuit switched connection and on leased point-to-point 4-wire digital circuits. ITU-T V.92 (2000), Enhancements to Recommendation V.90. ITU-T V.250 (1999), Serial asynchronous automatic dialling and control. ITU-T V.2
47、51 (1998), Procedure for DTE-controlled call negotiation. ISO/IEC 3309:1993, Information technology Telecommunications and information exchange between systems High-level data link control (HDLC) procedures Frame structure. 3 Definitions This Recommendation defines the following terms: 3.1 answering
48、 station: The DTE, DCE and other associated terminal equipment which answers a call placed on the PSTN. 3.2 calling station: The DTE, DCE and other associated terminal equipment which originates a call over the PSTN. 3.3 initiating station: The DTE, DCE and other associated terminal equipment which
49、initiates a V.8 bis transaction. This may be either the answering or calling station on the PSTN or either station on a leased circuit, and may change from one V.8 bis transaction to the next. When a transaction is initiated upon automatic answering of a call placed on the PSTN, the answering station is the initiating station. 3.4 responding station: The station which responds to initiation of a V.8 bis transaction from the remote station. This may be either the answering or calling station on the PSTN or
