1、 STD-ITU-T RECMN T-31 AMD 1-ENGL 177b E 4b257L ObZLObI 441 INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 1 TERMINALS FOR TELEMATIC SERVICES T.31 (07196) ASYNCHRONOUS FACSIMILE DCE CONTROL - SERVICE CLASS I ANNEX B - PROCEDURE FOR SERVICE CLASS
2、I SUPPORT OF V.34 MODEMS Amendment I to ITU-T Recommendation T.31 (Previously “CCITT Recommendations”) COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T RECMN T-31 AMD 1-ENGL 177b 48b2571 ObZLOb2 388 m FOREWORD The IT-T (Telecom
3、munication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and miff questions and issuing Recommen- dations on them with a view to standardizing telecommunications on a worldwide basis. The Wo
4、rld Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the IT-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
5、 down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). Amendment 1 to IT-T Recommendation T.31, was prepared by ITU-T Study Group 8 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 3rd of July 1996. NOTE In this Recommendation, the expression “Administration” is us
6、ed for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1996 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 per
7、mission in writing from the ITU. COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services. STD-ITU-T RECMN T.31 AMD 1-ENGL 199b 4Bb257L Ob2LOb3 214 CONTENTS B.l B.2 B.3 B.4 B.5 B.6 B . 7 B.8 B . 9 B.10 Introduction References . Functions Defini
8、tions and conventions . Transparent data commands . Initial V.34 rate controls and indications DTE-DCE Data . Source terminal procedures Recipient terminal procedures Sample sessions (Informative) Recommendation T.31/ Amd.1 (07/96) Page 1 1 2 2 2 2 4 5 7 9 i COPYRIGHT International Telecommunication
9、s Union/ITU TelecommunicationsLicensed by Information Handling ServicesSUMMARY This amendment contains a new Annex B: “Procedure for Service class 1 support of V.34 modems” which support the features in future Recommendation T.30 ii Recommendation T.311 Amd.1 (07/96) COPYRIGHT International Telecomm
10、unications Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T RECMN “-31 AND L-ENGL L77b 48b257L Ub2LOb5 O77 m Amendment 1 to Recommendation T.31 ASYNCHRONOUS FACSIMILE DCE CONTROL - SERVICE CLASS 1 Annex B Procedure for Service Class 1 support of V.34 modems (This annex
11、forms an integral part of the Recommendation) (Geneva, 1996) B.l Introduction B.l.l V.34 Modems References in this annex to user data rates greater than 28,800 bitsls are in anticipation of an amended version of Recommendation V.34 expected in 1996. Recommendation V.34 is standardized for use on the
12、 GSTN at rates up to 33,600 bit/s. Recommendation V.34 defines two modes of operation: 0 Duplex (clauses 5, 7,8,9, 10.1, 11). Half duplex (clauses 5,7,8,9, 10.2, 12). Half duplex mode has two channels: Half duplex high speed primary channel Duplex low speed control channel B.1.2 T.30 procedures for
13、use with V.34 modems Procedures for V.34 facsimile are defined for both V.34 modes: 0 Annex CT.30, with revisions, defines Group 3 facsimile duplex V.34. Annex FR.30 defines Group 3 facsimile procedures for half duplex V.34. This annex defines procedures for a Service Class 1 facsimile DCE to implem
14、ent Annex Cm.30 or Annex F iT.30 with V.34 modems. B.1.3 V.8 call negotiation For all uses of Recommendation V.34, procedures defined in Recommendation V.8 are required for negotiating the call type. For T.30 operation, this includes determination of the V.34 mode (duplex or half-duplex) and the dir
15、ection of the message (send or receive) if half duplex is used. Annex AN.25 ter defines procedures for a DCE to implement V.8 call negotiation under control of a DTE; these procedures are used in implementing Service Class 1 support for V.34 facsimile. B.2 References - ITU-T Recommendation V.34 (199
16、6), 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-ro-point 2-wire telephone-type circuits. IT-T Recommendation V.25 terlAnnex A (1996), Procedure for DTE - controlled call negotiation. - - IT-T Recommendation T.
17、30 (1996). Recommendation T.311 Amd.1 (07/96) 1 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling ServicesB.3 Functions A DCE compliant with this annex shall provide the following functions to the DE: a) b) c) d) e) f) g) h) Procedures to control
18、 V.8 call type negotiation (e.g. Annex AN.25 fer). Optional procedures to constrain the primary channel rate. Optional procedures to constrain the control channel rate. Procedures to simultaneously send and receive data in Annex CiT.30 operation. Procedures to simultaneously send and receive data in
19、 Annex Fm.30 operation. Procedures for flow control of DTE-DCE data streams. Procedures to control the V.34 mode. Indications of the V.34 state. B.4 Definitions and conventions The following definitions apply, in addition to those defined in this Recommendation or in Recommendations T.30 or V.34: B.
20、4.1 B.4.2 B.4.3 HDLC frame octets: The binary coded information contained in the HDLC frames defined in Recommendation T.30 and its Annexes, consisting of the control octet, the address octet, received FCS octets and any FIF octets. The DCE generates and consumes: flags, flag transparency O-bits, tr
21、ansmitted FCS octets. source DCE: The DCE which transmits primary channel data in half duplex mode. recipient DCE: The DCE which receives primary channel data in half duplex mode. B.5 Transparent data commands Table 4 defines three Transparent Data Commands used in Service Class 1 facsimile DCE. Thi
22、s annex defines additional transparent data commands in Table B.l, for the following functions: a) b) c) transmit HDLC frames; d) transmit HDLC aborts; e) f) indicate received HDLC aborts; g) h) i) j) retrain initiation and selection; k) rate selection and indication. shielding of escape characters
23、in data; shielding of DC1 and DC3 characters for duplex DCl/DC3 in band flow control; receive HDLC frames and indicate errorho-error FCS; carrier termination command and indication; half duplex primarykontrol channel selection and indication; rate renegotiation initiation, selection and indication;
24、Unless specified in the text, all transparent data commands defined are valid as commands from the DTE and as indications from the DCE. B.6 Initial V.34 rate controls and indications B.6.1 Write Syntax: Valid Values: see subparameters below. Default values: Initial V.34 rate controls, +F34 parameter
25、 +F34= , , , ,uate transparent command code. Subparameters In half duplex V.34 operation, unaxp is the maximum rate that the DCE may use for the primary channel, in units of 2400 bids. Valid non-zero unaxp values range from 1 (2400 bids) to 14 (33 600 bit/s). In duplex operation, is the maximum rate
26、 that the DCE may use for transmit data. If not set by the DTE, the default value O selects the maximum rate supported by the DCE. In half duplex V.34 operation, uninp is the minimum rate that the DCE may use for the primary channel. Valid values are the same as those defined for unaxp. In duplex V.
27、34 operation, uninp is the minimum rate the DCE may use for transmit data. If not set by the DTE, the default value O selects the minimum rate supported by the DCE (2400 bids in Recommendation V.34). In half duplex V.34 operation, is the preferred rate that the DCE may use for the control channel re
28、ceive rate, in units of 1200 bids. Valid values are 1 (1200 bids) and 2 (2400 bids) and O (no preference specified). The default value is O. If set to O, the DCE allows the V.34 modem to select the rate. If set to 1 or 2, and if that rate is supported by the remote terminal, that rate is selected. T
29、his subparamter is ignored in duplex V.34 operation. unaxp2 is the maximum rate that the DCE may use for receive data in duplex V.34 operation. Valid values are the same as those defined for unaxp. If not set by the DTE, the default value O selects the same value as . This subparameter is ignored in
30、 half duplex V.34 operation. is the minimum rate that the DCE may use for receive data in duplex V.34 operation. Valid values are the same as those defined for . If not set by the DTE, the default value O selects the same value as . This subparameter is ignored in half duplex V.34 operation. B.6.2 I
31、nitiai V.34 rate indication Syntax: +F34:, for half duplex or: +F34:, for duplex The DCE shall issue this indication before the CONNECT result code is issued. The DCE shall include a indication for duplex or half-duplex operation. Valid values for are the same as those defined for (B.6.1). For duple
32、x operation, the indicates the receive rate, if different from the transmit rate. If V.34 half duplex mode is used, the DCE shall also include a indication. indicates the control channel receive rate, if different from the control channel transmit rate. Valid values for and are the same as those def
33、ined for (B.6. I). Recommendation T.31/ Amd.1 (07/96) 3 COPYRIGHT International Telecommunications Union/ITU TelecommunicationsLicensed by Information Handling Services STD-ITU-T RECMN T-31 AND 1-ENGL 177b = 48b257L Ob2LOb8 8Tb T*50code9 1 Subclauses 1 I printed Command pair symbol TABLE B.lm.31 Tra
34、nsparent data commands utn 013 0/7 O14 611 1 6/13 6/12 6/10 6/8 6/9 B.7 B.7 B.8.3 B.8.4 B.8.4 B.8.7 B.9.8 B.8.5-B.8.6 B.8.4 cDLEq 168 q192 cDLEq264 710 711 712 713 714 715 716 717 718 719 7/10 711 1 7/12 711 3 Description Zharacter Transparency: iubstitute one 10h pattern iubstitute two 10h patterns
35、 Shielded Control Words: substitute one 1 lh pattern to enable flow control substitute one 13h pattern to disable flow control HDLC frame Delimiters End of HDLC frame w/o detected FCS error End of HDLC frame with FCS error V.34 mode selectionlindication End transmission Select primary channel (12.5N
36、.34) Select control channel (half duplex only) (12.6N.34) Request primary rate renegotiation (12.5N.34) Request duplex retrain (12.7N.34) Initiate termination of send (Figure F.5.1 l.30) Request control channel retrain V.34 control channel rate requestlindication 1200 bitls 2400 bius V.34 primary ch
37、annel rate requestlindication 2 400 bitls 4 800 bitls 7 200 bitls 9 600 bitls 12 O00 bitls 14 400 bitls 16 800 bitls 19 200 bitls 21 600 bids 24 O00 biUs 26 400 bitls 28 800 bitls 31 200 bitls 33 600 bitls B.7 DTE-DCE Data For V.34 transfer between DTE and DCE, the following procedures apply: B.7.1
38、DTE to DCE messages After the CONNECT result code, the DCE shall accept three types of data from the DTE. a) b) c) Transparent data commands, as defined in Table B. 1. HDLC frame octets, terminated by . and (DLEcDC3 commands for flow control of data from the DCE. B.7.2 DCE to DTE messages After the
39、CONNECT result code, the DCE shall send three types of data to the DTE. Transparent data indications, as defined in Table B. 1. HDLC frame octets, terminated by or and commands for flow control of data from the DTE. a) b) c) 4 Recommendation T.31/ Amd.1 (07/96) COPYRIGHT International Telecommunicat
40、ions Union/ITU TelecommunicationsLicensed by Information Handling ServicesSTD-ITU-T RECMN T-31 AMD 1-ENGL 177b 4Bb257L Ob21Ob7 732 = B.7.3 HDLC frame data The DCE shall transmit FLAGS upon DTE data underrun. HDLC frame octet data may not contain control character . Therefore, the Transparent Data co
41、mmands defined in Table B. 1 shall be used to represent the characters. Each HDLC frame sent from the DTE to the DCE shall be terminated by the transparent data command. Each HDLC frame sent from the DCE to the DTE shall be terminated by the transparent data command if the received FCS sequence is v
42、alid, or by the transparent data command if the received FCS sequence is invalid. This received HDLC frame shall include the FCS sequence, or a substitute sequence of the same length. B.8 Source terminai procedures This subclause defines procedures for the Source DCE and DTE. B.8.1 Transition from V
43、.8 negotiation After V.8 negotiation is complete, the T.30 procedures must commence. These begin with V.34 carrier training, as preconfigured by the V.8 negotiation (direction, half duplex or duplex mode) and the +F34 command (rates). The DCE shall decode V.8 negotiation to detect these selections,
44、and prepare to conduct V.34 carrier training in the appropriate mode. If the source DCE is the originate terminal, it shall issue appropriate indication of the JM selections (e.g. A.6.5N.25 ter) and prompt the DTE for the command to complete Recommendation V.8 (send CJ) and inititate V.34 training.
45、If the source DCE is the answer terminal, the DTE should issue the ATO command on the same command line as the +A8M command (or the ATA command if configured for DCE-controlled V.8 negotiation). This is necessary as the DCE must stop JM transmission shortly after receiving U to avoid missing the beg
46、inning of the V.34 training sequence. B.8.2 Initiate procedures The DCE shall accept an ATO command to complete Recommendation V.8 and initiate V.34 procedures. The DCE shall acknowledge this command with the following consecutive messages: a) b) an +F34 indication (B.6.2). c) d) an +A8J:1 indicatio
47、n (A.6.4N.25 fer). a CONNECT result code (Table 3). If in half duplex mode, a transparent data commands. If in duplex mode, a transparent data commands. Once the DCE has connected, it shall transmit HDLC flags until it receives data from the DTE, and shall hunt for HDLC flags in the received data. T
48、his command is issued once for each T.30 message transfer. If the Source DTE sends an EOM signal to the remote terminal, the V.8 procedures will be repeated, so ATO command execution must be terminated. B.8.3 Terminate procedures B.8.3.1 Terminating events ATO command execution is terminated by one
49、of three events: 0 Source DTE issues a c) d) e) stop carrier transmission; f) g) h) switch to command mode. if sending an HDLC frame, complete sending the frame, including FCS and final flag; send any V.34 specific carrier termination signals; if in half duplex mode, wait for remote carrier to turn off; issue and an OK final result code to the DTE; stay connected to the GSTN; B.8.3.3 DCE initiated termination If the DCE detects remote disconnection or if the half duplex mode receives at least 40 consecutive ones from the remote DCE, the DCE shall: a) stop c
