1、 INTERNATIONAL TELECOMMUNICATION UNION V.251TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (02/98) SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Control procedures Procedure for DTE-controlled call negotiation ITU-T Recommendation V.251 (Previously CCITT Recommendation) ITU-T V-SERIES REC
2、OMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK For further details, please refer to ITU-T List of Recommendations.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 transmissio
3、n of data and 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 Recommendation V.251 (02/98) i ITU-T RECOMMENDATION V.251 PROCEDURE FOR DTE-CONTROLLED
4、 CALL NEGOTIATION Summary This Recommendation defines means for use in DTE control of V.8 and V.8 bis call negotiation. Source ITU-T Recommendation V.251 was prepared by ITU-T Study Group 16 (1997-2000) and was approved and published as V.25 ter Annex A under the WTSC Resolution No. 1 procedure on 1
5、1 July 1997. It was then renumbered as V.251 under the WTSC Resolution No. 1 procedure on 6 February 1998, without further modification. ii Recommendation V.251 (02/98) FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. T
6、he ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The 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 Telecommunicati
7、on Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Reso
8、lution No. 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 term recognized operating agency (ROA) includes any individual, company, corporation or governmental
9、 organization that operates a public correspondence service. The terms Administration, ROA and public correspondence are defined in the Constitution of the ITU (Geneva, 1992). INTELLECTUAL PROPERTY RIGHTS=The ITU draws attention to the possibility that the practice or implementation of this Recommen
10、dation may involve the use of a claimed Intellectual Property Right. The 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 ap
11、proval of this Recommendation, the 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 th
12、e TSB patent database. =ITU 2000 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. Recommendation V.251 (02/98) iii CONTENTS Page 1 In
13、troduction and scope 1 2 References. 1 3 Functions. 2 4 Definitions and conventions . 2 5 Commands 3 5.1 V.8 and V.8 bis operation controls, +A8E 3 5.2 Send V.8 menu signals 5 5.3 Send V.8 bis signal and/or message(s) . 5 6 V.8 signal indications . 6 6.1 CI signal indication, +A8I. 6 6.2 Calling ton
14、e indication, +A8C 6 6.3 Answer signal indication, +A8A. 7 6.4 V.8 negotiation complete, +A8J . 8 6.5 V.8 menu report, +A8M 8 6.6 V.8 bis signal and message reporting 8 7 V.8 origination procedures 9 7.1 Configuration before the Dial command 9 7.2 Operation after dialling is completed 9 7.3 Answerin
15、g signal detection. 9 7.4 V.8 abort . 9 7.5 CM signal generation 10 7.6 JM signal detection . 10 7.7 Transition to communications 10 8 V.8 Answer procedures. 10 8.1 Configuration before the Answer command. 10 8.2 Operation after the Answer command 10 8.3 Calling signal detection. 11 8.4 JM signal ge
16、neration. 11 8.5 V.8 abort . 11 8.6 Transition to communications 11 9 V.8 bis procedures 12 9.1 Initiation 12 9.2 Reception 12 iv Recommendation V.251 (02/98) Page 9.3 Transmission. 12 9.4 Termination. 12 10 Sample sessions 12 10.1 V.8 origination, connect as V.34 transmit and receive data . 13 10.2
17、 V.8 answer, preconfigure for facsimile, but adaptively connect as a V.34 data modem 14 10.3 V.8 bis sample session, based on Figure II.4/V.8 bis . 14 Recommendation V.251 (02/98) 1 Recommendation V.251 PROCEDURE FOR DTE-CONTROLLED CALL NEGOTIATION (Geneva, 1998) 1 Introduction and scope Recommendat
18、ion V.8 is standardized for use in negotiating the call type at the beginning of a PSTN call. Recommendation V.8 bis is standardized for use in negotiating the call type during a PSTN call. They provide means to select amongst several single media or multimedia operating modes. data modem (V-Series
19、modems); text telephone (Recommendation V.18); send G3 facsimile (from calling terminal); receive G3 facsimile (polling); simple voice telephony; analog simultaneous Voice and data; digital simultaneous Voice and data; multimedia terminal (e.g. Recommendation H.324). Means are defined in this Recomm
20、endation for use in DTE control of V.8 and V.8 bis call negotiation. These means are designed so that the negotiation decisions are made in the DTE, so that compliant DCE do not need modification each time V.8 or V.8 bis code points are added or modified in other ways. 2 References The following ITU
21、-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 to revision; all users of this Recommend
22、ation 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. ITU-T Recommendation V.8 bis (1998), Procedures for the identificati
23、on and selection of common modes of operation between data circuit-terminating equipments (DCEs) 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.25 (1996), Automatic answering equipmen
24、t and general procedures for automatic calling equipment on the general switched telephone network including procedures for disabling of echo control devices for both manually and automatically established calls. 2 Recommendation V.251 (02/98) 3 Functions A DCE compliant with this annex shall provid
25、e the following functions: a) accept DTE preconfiguration command before call establishment; b) provide necessary V.8 physical layer functions, including ANSam and V.21 modem; c) provide indications to the DTE for detection of remote V.8 signals (ANSam, CI, CM, JM, CJ), V.25 signals (CT, T.30 CNG) a
26、nd relevant sigA and sigC signals (e.g. T.30 Ch2 flags); d) accept V.8 signals from the remote station, and convert them to hexadecimal octet coding for presentation to the DTE; e) accept V.8 signal octets in hexadecimal octet coding from the DTE and convert them to V.8 format for transmission; f) r
27、eturn to Command State after CJ transmission, detection or failure detection, so that DTE can take timely action; g) accept V.8 bis signal codes and V.8 bis message octets in hexadecimal octet coding from the DTE and convert them to V.8 bis format for transmission; h) detect V.8 bis signals and mess
28、ages from the remote station, and convert them to the appropriate signal codes and hexadecimal octet coding for presentation to the DTE. 4 Definitions and conventions This Recommendation defines the following terms: 4.1 hexadecimal octet coding: Hexadecimal octet coding is a means for representing a
29、 string of octets as a string of hexadecimal digits, with two digits representing each octet. Each octet is issued by the DTE or DCE in the same time sequence as transmitted on the GSTN line, with no intervening characters. For each octet, the 8-bit sequence is encoded as two hexadecimal digits. Bit
30、 0 is the first transmitted; bit 7 is the last. Bits 7-4 are encoded as the first hexadecimal digit, with Bit 7 as MSB and Bit 4 as LSB. Bits 3-0 are encoded as the second hexadecimal digit, with Bit 3 as MSB and Bit 0 as LSB. Examples: Octet bit pattern (time order) Hexadecimal coding T.50 codes 00
31、011011 D8 4/4, 3/8 11100100 27 3/2, 3/7 10000011 10100010 11001000 00001001 C1451390 4/3, 3/1, 3/4, 3/5, 3/1, 3/3, 3/9, 3/0 4.2 hexadecimal octet sequence: A hexadecimal octet sequence is an even number of hexadecimal digits, terminated by a (T.50 0/13) character. 4.3 V.8 signal format: There are th
32、ree V.8 signals that include strings of octets: CI, CM and JM. In these signals, the DCE transmits a repeating pattern including 10 bits of 1 (mark idle) followed by a synchronization signal and one or more octets; see Tables 1/V.8 to 6/V.8. 4.4 V.8 bis signal and message format: All V.8 bis signals
33、 consist of a dual tone followed by a single tone; see 7.1/V.8 bis. All V.8 bis messages consist of one or two HDLC frames carried on V.21 (H) modulation; see 7.2/V.8 bis. Recommendation V.251 (02/98) 3 5 Commands 5.1 V.8 and V.8 bis operation controls, +A8E Write Syntax: +A8E=, Valid Values: see Ta
34、ble 1 below Default values: 1,1,1,“,“ Description This command is defined for two conditions: as a parameter while the DCE is on-hook, and as an action command while the DCE is off-hook. If enabled, V.8 negotiation does not preclude simultaneous implementation of other negotiation means (e.g. Recomm
35、endation V.8 bis, Recommendation V.18, Annex A/V.32 bis). This command is a compound parameter if issued while the DCE is on-hook, used to precondition V.8 and V.8 bis originating and answering operation. It is issued by the DTE before the Dial (D) or Answer (A) command, regardless of the state of t
36、he +FCLASS parameter. This command is an action command if issued while the DCE is off-hook, to (re)start V.8 or V.8 bis negotiation. For example, if initial V.8 negotiation failed, but subsequent T.30 negotiation indicated V.8 capability, this command may be used to initiate V.8 negotiation. The su
37、bparameters are defined as follows: Table 1/V.251 V.8 operation control subparameters Values Description =0 Disable V.8 origination negotiation =1 Enable DCE-controlled V.8 origination negotiation =2 Enable DTE-controlled V.8 origination negotiation, send V.8 CI only =3 Enable DTE-controlled V.8 ori
38、gination negotiation, send 1100 Hz CNG only =4 Enable DTE-controlled V.8 origination negotiation, send 1300 Hz CT only =5 Enable DTE-controlled V.8 origination negotiation, send no tones =6 Enable DCE-controlled V.8 origination negotiation, issue +A8x indications =0 Disable V.8 answer negotiation =1
39、 Enable DCE-controlled V.8 answer negotiation =2 Enable DTE-controlled V.8 answer negotiation, send ANSam =3 Enable DTE-controlled V.8 answer negotiation, send no signal =4 Disable DTE-controlled V.8 answer negotiation, send ANS =5 Enable DCE-controlled V.8 answer negotiation, issue +A8x indications
40、 =XY Set the V.8 CI signal call function to the hexadecimal octet value XY =0 Disable V.8 bis negotiation =1 enable DCE-controlled V8 bis negotiation =2 Enable DTE-controlled V.8 bis negotiation = “ Set to alternative list of call function “option bit“ values that the answering DCE shall accept from
41、 the caller = “ Set to alternative list of protocol “option bit“ values that the answering DCE shall accept from the caller 4 Recommendation V.251 (02/98) For subparameters , and , values of 0 disable the corresponding feature. Values of 1 enable the feature, with operation controlled by the DCE, ba
42、sed implicitly on manufacturer-determined procedures and on previous configuration commands. The ATD and ATA commands behave as specified in 6.3.1 and 6.3.5, respectively, and +A8n indications are not generated by the DCE. For example, a DCE configured with +FCLASS=0 gets V.8 CI, CM and JM informati
43、on from the settings of the +MS, +ES, +DS, +MV18S parameters in this Recommendation. Similarly, a DCE configured with +FCLASS=1.0 gets some CI, CM and JM information from the +F34 parameter (Annex B/T.31). For subparameter values =6 and =5, the +A8I, +A8C, +A8A, +A8J, and +A8M indications are issued
44、 during the course of the V.8 session to notify the DTE when the relevant V.8 signals are received. The DCE control the V.8 session, however, and the +A8M command is not used. The subparameter setting is used when =5. The subparameter is set to a string, consisting of an alternative list of call fun
45、ction “option bit“ values that the answering DCE shall accept from the caller; for example, “2,6“ for V.18 and data. If the caller transmits a call function of either the preferred value, or a value from this list, the answerer shall respond with a JM set to the value received from the caller. If a
46、different call function is received, the DCE shall transmit a JM with the call function set to the preferred value, with the modulation bits set to zero (per Recommendation V.8). The range of valid option bit values depends on the extension octet capabilities of the DCE. Values 0-6 correspond to the
47、 setting of the b5-b7 bits in a basic (non-extended) call function octet, e.g. a value of 6 corresponds to Transmit and Receive data. Values 7-38 correspond to the use of one extension octet, where bits b5-b7 in the basic octet all set to one. Each extension octet has five bits available for express
48、ing category values. Thus, values 39-1062 correspond to the use of two extension octets, constructed by considering b0 of the first extension octet to be the least significant bit of a ten-bit number, with b7 of the second extension octet as the most significant bit; this ten-bit number is then offs
49、et by 39 so as not to conflict with the single-extension-octet values. This process may be extended for additional call function extension octets. The preferred call function option bit value is determined by DCE configuration. For example, it is equal to 4 if +FCLASS=1.0. The function of the subparameter is identical to , except it applies to the protocol category. See Table 2. Table 2/V.251 V.8 operation control read and test Command DCE action +A8E? Report current values of subparameters +A8E=? Report supported ranges of values: (range of suppor
