1、STD-ITU-T RECMN V.252-ENGL 1998 m 4Bb2591 ObLi6251 717 m INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD IZAT ION SECTOR OF ITU V.252 SERIES V: DATA COMMUNICATION OVER THE TELEPHONE NETWORK Control procedures (02/98) Procedure for control of V.70 and H.324 terminals by a DTE
2、ITU-T Recommendation V.252 (Previously CCITT Recommendation) ITU-T V-SERIES RECOMMENDATIONS DATA COMMUNICATION OVER THE TELEPHONE NETWORK General Interfaces and voiceband modems Wideband modems Error control Transmission quality and maintenance Simultaneous transmission of data and other signals I n
3、 terworki ng with other networks v.1-v.9 V. I 0-V. 34 V.35-v.39 V.40-V.49 V. 504.59 V.60-V.99 V. 100-V. 199 II Interface laver sPecifications for data communication V.200-V.249 Control procedures V.250-V.299 I For further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN V-252-
4、ENGL 1798 48b257L Obqb253 57T ITU-T RECOMMENDATION V.252 PROCEDURE FOR CONTROL OF V.70 AND H.324 TERMINALS BY A DTE Summary This Recommendation describes the operation of the DCE/DTE interface in which either an H.324 entity or a V.70 DSVD entity is implemented in the DCE. The V.70 entity in the DCE
5、 comprises at least a V.76 multiplexer and the V.75 control unit. The H.324 entity in the DCE comprises at least an H.223 multiplexer and the H.245 control unit for H.324. Audio and video transducers and codecs, if present, are implemented in the DCE or in devices attached directly to the DCE. Comma
6、nds and indications defined in this Recommendation are valid in FCLASS=17.0 or FCLASS=18.0. The availability of Class 17.0 in a DCE indicates that the DCE is capable of supporting the control functions of a V.70 DSVD device. The availability of Class 18.0 in a DCE indicates that the DCE is capable o
7、f supporting the control functions of an H.324 terminal. Source ITU-T Recommendation V.252 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on the 6th of February 1998. STD-ITU-T RECMN Vs252-ENGL 1998 48b257L Ob4b254 42h FOREWORD ITU (Intern
8、ational Telecommunication Union) is the United Nations Specialized Agency in the field of telecommunications. The 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 Recommen
9、dations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication 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.
10、 The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommen
11、dation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The IT draws attention to the possibility that the practice or implementation of this Recommendation may involve the use
12、 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 approval of this Recommendat
13、ion, 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 the TSB patent database. O I
14、TU 1998 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. 11 Recommendation V.252 (02198) STDDITU-T RECMN V-252-ENGL 1998 48b257L Obll
15、b255 3b2 CONTENTS 1 2 2.1 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 4.10 4.11 4.12 5 5.1 Scope Control model . Device codes . Commands Terminal configuration. +STC . Close logical channel. +STH Data configuration. +SDC Audio transmit configuration. +SAC .
16、Audio receive mode +SAM Video transmit configuration +SVC (Class 18 only) . Video receive mode +SVM (Class 18 only) . Data indication reporting. +SDR Video indication reporting. +SVRR (Class 18 only) Capabilities indication reporting. +SCRR Audio indication reporting. +SARR . Additional commands . S
17、et audio code. +VAC Receive gain selection. +VGR Beep tone duration timer. +VTD DTMF and tone generation. +VTS . Ring local phone. +VE . Speakerphone ON/OFF. +VSP . Train acoustic echo-canceller. +VTA . Train hybrid echo.canceller. +VTH . Phone hookswitch status. +VPH Telephony port hook control. +V
18、HC Transmit gain selection. +VGT Speakerphone configuration. +VDX Indications Remote terminal capabilities indications 5.1.1 Remote terminal capability table entry indications. +SRCV. +SRCA. +SRCD 5.1.2 Remote terminal simultaneous capability indication. +SRSC Recommendation V.252 (02/98) Page 1 1 2
19、 3 3 4 5 7 8 10 11 12 13 13 14 14 14 15 16 17 17 19 20 20 21 21 22 22 23 23 24 24 . 111 5.2 5.3 5.4 5.5 5.6 6 6.1 6.2 6.3 6.4 7 7.1 7.2 7.3 STD-ITU-T RECMN Vg252-ENGL 1798 m 48b2571 Ubqb25b 2T7 m Data channel indication. +SDI . Audio receive channel indication. +SAR . Audio transmit channel indicati
20、on. +SAT Video transmit channel indication. +SVT (Class 18 only) . Video receive channel indication. +SVR (Class 18 only) Additional indications Audio code report. +VACR Caller ID report. +VCIDR Simple telephony event report. +VTER . DID report. +VDIDR In-band indications and commands In-band indica
21、tions . In-band commands . Remote DCE in-band commands and indications Page 24 25 25 25 25 26 26 26 26 26 27 27 27 28 iv Recommendation V.252 (02/98) STD-ITU-T RECMN V-252-ENGL 1978 E 48b259L Obllb257 135 W Recommendation V.252 PROCEDURE FOR CONTROL OF V.70 AND H.324 TERMINALS BY A DTE (Geneva, I998
22、) 1 Scope This Recommendation describes the operation of the DCEDTE interface in which either an H.324 entity or a V.70 DSVD entity is implemented in the DCE. The V.70 entity in the DCE comprises at least a V.76 multiplexer and the V.75 control unit. The H.324 entity in the DCE comprises at least an
23、 H.223 multiplexer and the H.245 control unit for H.324. Audio and video transducers and codecs, if present, are implemented in the DCE or in devices attached directly to the DCE. In the case of an H.324 DCE, if one or more data channels are present, one of them is assumed to terminate in the DTE. C
24、ommands and indications defined in this Recommendation are valid in FCLASS=l7.0 and/or FCLASS=18.0. The availability of Class 17.0 in a DCE indicates that the DCE is capable of supporting the V.76 multiplexing and V.75 control functions of a V.70 DSVD device. The availability of Class 18.0 in a DCE
25、indicates that the DCE is capable of supporting the H.223 multiplexing and H.245 control functions of an H.324 terminal. 2 Control model Figure 1 is a block diagram of a typical Class 17 system: GSTN Figure 1N.252 - V.70 DSVD DCE Recommendation V.252 (02/98) 1 STD.1TL.i-T RECMN V.252-ENGL 1978 R qb2
26、571 Ubllb25 U71 L MO Figure 2 is a block diagram of a typical Class 18 system: Local telephone port (see Note 1) Internal microphone DTE DCE r M1 Mn .= G.723 - External microphone n = 2255 Additional microphones = I I , , , 1 Ci- s1 Sn I I + External speaker n = 2255 Additional loudspeakers Class 18
27、 U data and Data Control control protocol HO Hn CO H.245 External handsebheadset n = 1 255 Additional handsetsheadsets Internal camera H.223 CI Cn Signal External camera n = 2255 Additional cameras i GSTN T1602550-97 Figure 2N.252 - H.324 terminal with “data port“ The basic model of V.70m.324 DCE co
28、ntrol is that there are a number of named “devices“ which are capable of sourcing or sinking audio, video, or data streams. These logical devices include physical media devices such as cameras, displays, microphones and speakers. All logical devices are assigned a one - or two-character device code.
29、 The DTE can control device characteristics and which devices are active on a given connection. The assignment of devices to specific V.76 or H.223 multiplexer channels, however, is the responsibility of the V.75 or H.245 control entity, respectively, in the DCE. 2.1 Device codes Each logical device
30、 is assigned a one - or two-character “device code“, as follows: Table 1N.252 - Device codes I I Devicecode I Logical device I so I Internal speaker I 2 Recommendation V.252 (02/98) STD-ITU-T RECMN V.252-ENGL 1978 m Li8b257L Obllb257 TO8 vo v1 Table 1N.252 - Device codes (end) Internal video display
31、 device External video display device I Devicecode I Logical device I Vn I n = 2255 Additional video displays NOTE 1 - It may be possible in some DCE, by hardware strapping or other means outside the scope of this Recommendation, to configure the “L“ local telephone port device to interconnect to ei
32、ther a local telephone device and appear as a PSTN telephone line (which would require the DCE to provide loop voltage, etc.) or to interconnect to a second PSTN telephone line and appear as a telephone device (which would require the DCE to provide loop supervision, ring detect, etc.). NOTE 2 - It
33、is intended that the device codes for non-video devices be identical to those defined in other functional classes, such as in Class 8.0. NOTE 3 - Support for “L“ and “R1 suffixes for left and right identification can be added once they are supported by H.245 and V.75. m In addition, data channels ar
34、e given a numeric identification label, with channel O being the “data port“ channel connected to the DTE. Channel existence and source/sink device assignment may be performed prior to a connection, either by default or by configuration command. In this case, the DCE shall automatically negotiate su
35、ch operation with the remote end at the commencement of a communication session. Alternately, channels and devices may be created and/or destroyed dynamically during a connection using the appropriate commands. 3 Commands 3.1 Terminal configuration, +STC Parameter +STC= “ Description This parameter
36、is used to select the audio, video (for Class is), and data devices that are to be used in a connection. If supported by the remote terminal, the specified devices shall be used. If issued during a connection, this is an action command that changes the configuration of the connection; in this case,
37、the DCE shall return ERROR if the new configuration is not supported by the remote terminal (e.g., if an OpenLogicalChannelReject response is received from the remote terminal). Note also that, prior to the ERROR final result code, the DCE may issue information text as to the reason for the failure.
38、 This information text shall take the form of +STC : FAIL , where the parameter has the following value assignments: Definition O Syntax error 1 XID frame rejection 2 OpenLogicalChannel rejection Recommendation V.252 (02198) 3 STD-ITU-T RECMN V-252-ENGL 1998 LiAb259L Ob4b2b0 72T If issued during a c
39、onnection, this shall cause the relevant channels to be established or released. Depending on the channel configuration and specific DCE implementation, this may be preceded by capability exchanges between the DCEs. If the channel indications defined in clause 5 are enabled, they are issued when the
40、 channels are opened or closed. Defined values A valid parameter value consists of a string, bounded by double quotes, of device codes as defined in 2.1 , with the device codes separated by commas. Default value Default configuration is determined by the manufacturer. Read syntax +STC? In command st
41、ate (i.e., not during a connection), the DCE shall return the current parameter setting, e.g.: +STC: “L,CO,VO, O“ for a DCE configured for audio on the local telephone, transmit video from the internal camera, receive video to the internal display, and a data channel to the DTE. In on-line command s
42、tate, the DCE shall return the current configuration in use on the connection. Test syntax +STC=? The DCE shall return information text indicating supported configurations. Lists of alternative devices which cannot be supported simultaneously may be enclosed in parentheses, e.g. : +STC: indicates th
43、e ability to support one audio transmit channel (from either local phone, or internal or external microphones), one audio receive channel, one video channel in each direction, and a data channel to the DTE. As another example, a DCE capable of supporting two duplex audio channel pairs, with one pair
44、 to the local phone, would return: +STC: IL, (MO,Ml), (SO,Sl), (CO,Cl), (V0,Vl) ,O“ More complex dependencies may be indicated by the DCE by returning multiple lines. 3.2 Close logical channel, +STH Parameter +STH=“ Description This action command is issued during a connection to cause the specified
45、 channel(s) to be released. Defined values A valid parameter value consists of a string, bounded by double quotes, of device codes as defined in 2.1, with the device codes separated by commas. Test syntax +STH=? 4 Recommendation V.252 (02/98) STD-ITU-T RECMN V.252-ENGL 1778 48b257L Ob4b2bL bbb In on
46、-line command state, the DCE shall return the current configuration in use on the connection, similar to the +STC? response, e.g.: +STH : “LfCOfVOf O“ for a DCE configured for audio on the local telephone, transmit video from the internal camera, receive video to the internal display, and a data cha
47、nnel to the DTE. In command state .e., not during a connection), the DCE shall retuni ERROR. 3.3 Data configuration, +SDC Parameter +SDC= , arc , 1 1 1 1 1 1 1 1 1 Description This parameter sets the preferred operating mode for duplex data channel . Data channel O is connected to the DTE port; othe
48、r data channels may exist which terminate in the DCE. For data channel O, the data application mode is communicated to the remote terminal, but the application itself is assumed to reside in the DTE. If the remote terminal is incapable of operating at the preferred mode, data channel operation may t
49、ake place in another mode within the DCEs capability. This command serves to configure DCE capabilities exchanges, and may be issued prior to a connection to change the DCE from the default configuration, or during a connection prior to a +STC command. The subsequent + STC will then trigger a capabilities exchange. Defined values Support for V.76 UIH frames for this channel: O Non-supported 1 Supported V.76 window size for this channel (1 127) V.76 error recovery for this channel: O None 1 Non-selective reject 2 Selective reject 3 Multiple selective re
