1、INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF TU T.134 (02198) SERIES T: TERMINALS FOR TELEMATIC SERVICES Text chat application entity ITU-T Recommendation T. 134 (Previously CCITT Recommendation) ITU-T T-SERIES RECOMMENDATIONS TERMINALS FOR TELEMATIC SERVI
2、CES For further details, please refer to ITU-T List of Recommendations. STD-ITU-T RECMN TmL3LI-ENGL 1778 W LIBb257L Ob4bZL7 557 ITU-T RECOMMENDATION T.134 TEXT CHAT APPLICATION ENTITY Summary This Recommendation defines a protocol that supports multipoint text conversation. The T. 134 protocol suppo
3、rts multipoint conversation in text by allowing text entered at one site to be advertised within a session to other sites. It enables simple real time text conversation between terminal users. The text conversation presentation protocol in Recommendation T. 140 is used in the text chatting applicati
4、on. Recommendation T. 134 uses services provided by Recommendations T. 122 (MCS) and T. 124 (GCC) also in their light profile defined in Annex C/T. 120. The Chat protocol is intended to be possible to combine with other data services as well as with video and audio in audiovisual services. Source IT
5、U-T Recommendation T.134 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. STDOITU-T RECMN T*L3i-ENGL 1998 48b259L ObibZL8 Y95 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized
6、 Agency in the field of telecommunications. The IT Telecommunication Standardization Sector (ITU-T) is a permanent organ of the ITU. The IT-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a
7、 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. The approval of Recommendations by the Members of the IT-T is cover
8、ed by the procedure laid down in WTSC Resolution No. 1. In some areas of information technology which fall within IT-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to ind
9、icate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position
10、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 Recommendation, the ITU had not received notice of intellectual property, protec
11、ted 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 ITU 1998 All rights reserved. No part of this publication may be repro
12、duced 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 T.134 (02/98) 1 2 3 4 5 5.1 6 6.1 6.2 7 8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 9 9.1 CONTENTS Scope Normative references Definitions Abb
13、reviations . Overview CHAT concepts 5.1.1 Text and control Use of MCS MCS channel usage Use of MCS data services . Use of GCC Protocol specification . Capabilities . CHATPDU formats CHATE activation Response to long delays or high loads . CHAT sessions . Text and presentation control entry Text and
14、presentation control reception . CHATPDU definitions . ASN . 1 definition . Annex A . Static channel ID assignments . Annex B . Object Identifier assignments Appendix I . Informative values . Recommendation T.134 (02/98) Page 1 2 2 3 3 3 4 4 5 5 5 6 6 6 6 6 6 6 7 7 7 8 9 9 . 111 Recommendation T.134
15、 Network Specific Transport Protocols T.123 TEXT CHAT APPLICATION ENTITY (Geneva, 1998) 1 Scope This Recommendation defines a protocol that supports multipoint text conversation, commonly known as chatting. It uses services provided by Recommendations T.122 (MCS) and T.124 (GCC) also in their light
16、profile specified by Annex C/T. 120. Figure 1 presents an overview of the scope of this Recommendation and its relationship to the other elements of the T. 120 framework within a single node. User Application (Using Recommendation T. i 40 presentation level chat protocol) 1 t I Controller I I T. 120
17、 Application Protocol Recommendations l I 1 r T1604150-97 Figure 1R.134 - Scope of this Recommendation Recommendation T.134 (02/98) 1 2 Normative references The following ITU Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this
18、Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and oth
19、er references listed below. A list of the currently valid ITU-T Recommendations is regularly published. ITU-T Recommendation F.71 O (1 991), General principles for audiographic conference sew ice. ITU-T Recommendation T. 120 (1 996), Data protocols for multimedia conferencing. ITU-T Recommendation T
20、. 121 (1 996), Generic application template. ITU-T Recommendation T. 122 (1 993), Multipoint communication service for audiographics and audiovisual conferencing service dejnition. ITU-T Recommendation T. 123 (1 996), Network speclfc data protocol stacks for multimedia conferencing. ITU-T Recommenda
21、tion T. 124 (1 995), Generic Conference Control. ITU-T Recommendation T. 125 (1 994), Multipoint communication service protocol specification. ITU-T Recommendation T. 140 (1 998), Text conversation protocol for multimedia application. ITU-T Recommendation X.680 (1997) I ISO/IEC 8824-1: 1998, Informa
22、tion technology - Abstract Syntax Notation One (ASN) - Specification of basic notation. ITU-T Recommendation X.691 (1997) I ISOAEC 8825-2: 1998, Information technology - ASN. 1 encoding rules - Specification of Packed Encoding Rules (PER). ISO/IEC 10646-1 : 1993 (including Amendments 1996), Informat
23、ion technology - Universal Multiple-Octet Coded Character Set (USC) - Part I: Architecture and Basic Multilingual Plane. Definitions This Recommendation defines the following terms: 3.1 Text Chat (CHAT): A process that enables text entered on one terminal to be displayed at once to the user on that
24、terminal and on one or more other terminals participating in a chat session. 3.2 Chat Protocol Entity (CHATE): An Application Protocol Entity that interacts with a user application above and with the local MCS (Multipoint Communication Service) and local GCC (Generic Conference Control) providers be
25、low to implement application sharing. Data is exchanged between peer CHATEs using CHATPDUs (Chat Protocol Data Units). 3.3 handle: A CHAT session-wide unique number used to identi an addressable item. 3.4 standard capability: The capability is defined within the scope of this Recommendation but is n
26、ot required for all CHATE implementations. Note that all standard capabilities must be negotiated before use. 3.5 unicode: Text string format with multilingual capabilities as defined in ISO/IEC 10646- 1. 2 Recommendation T.134 (02/98) 3.6 area managed by the terminal window manager. 3.7 conversatio
27、n protocol. window: A rectangular area on the terminal display corresponding to a user interface display Chat Channel (CHAT-CHANNEL): A T.120 channel dedicated for use by the text 4 Abbreviations This Recommendation uses the following abbreviations: CHATE Text Chat Protocol Entity CHATPDU Chat Proto
28、col Data Unit GCC Generic Conference Control IEC International Electrotechnical Commission IS0 International Organization for Standardization ITU International Telecommunication Union MCS Multipoint Communication Service 5 Overview The CHAT protocol enables multipoint text conversation in real time
29、by allowing text entered at one site to be displayed within a session at other sites. Each site can enter text in the session. Exchange of text is maintained on a character-by-character or close to character-by-character basis in order to give the session participants an opportunity to exercise a na
30、tural conversation in text. The text and control exchange is done according to Recommendation T. 140. A CHAT session consists of one or more CHATE entities which cooperate via the CHAT protocol to distribute entered text within the session. The CHAT protocol defines interactions between CHATEs. It d
31、oes not define interactions between a CHATE and the operating system or input and output devices on the local terminal. 5.1 CHAT concepts Figure 2 shows an example collection of CHATEs within a CHAT session. i T1604160-97 Figure 2m.134 a CHATE A and B both enters text into the CHAT session and displ
32、ays text received from other CHATEs. Recommendation T.134 (02/98) 3 STD-ITU-T RECMN T-Lgi-ENGL 1998 iAb259L Oblib2Z3 852 D 0 The MCS provider in the mode with CHATE C acts as an MCU, distributing the CHATPDUs among the CHATEs. 5.1.1 Text and control When text is entered or a control action taken, th
33、en the CHATE constructs a suitable chat entry for the other CHATEs. The CHAT chat entry consists of interleaved text entries and presentation control actions as specified in Recommendation T. 140. 6 Use of MCS All T. 134 communication shall be through MCS as specified in Recommendation T. 122 and ke
34、eping within the subset defined by Annex CK.120. This clause details specific use of MCS services, channel allocation and data priorities. This Recommendation complies with the mechanisms described in Recommendation T. 12 1 regarding proper operations for standard base sessions, and the registration
35、 session. A CHATE uses the MCS service primitives described in Table 6-1 to attach and detach from a domain, join and leave the CHAT channel, and send and receive CHATPDUs. Table 6-1m.134 - MCS primitives needed by a CHATE MCS primitive I MCS-ATTACH-USER MC S-DETACH-USER MC S-CHANNEL- JOIN MCS-CHANN
36、EL-LEAVE MCS-UNIFORM-SEND-DATA Description Creates an MCS attachment through an MCS SAP to a domain hosted by the MCS provider. A result is confirmed to the requester. If the request is accepted, a user ID is assigned. Deletes an MCS attachment that was created previously by invocation of MCS-ATTACH
37、-USER. This primitive may be requested by a user or initiated by a provider. It delivers an indication at every other MCS attachment to the same domain. If provider initiated, an indication is also delivered at the deleted attachment. Used by an application client to join an appropriate channel whos
38、e use is defined by the application. This is a prerequisite for receiving data sent to the channel. Used by an application client to leave a previously joined channel and thus stop receiving data sent to that channel. The primitive may be user initiated (request only) or provider initiated (indicati
39、on to affected user only). Used to transmit data to other members of a domain. If the sender is a member of the destination channel, it will not receive its own data indications. However, it will receive data indications from other sources addressed to that channel. MCS request primitives are direct
40、ed from the CHATE to the MCS provider, while indication primitives are directed from the MCS provider towards the CHATE. Additional detail on the MCS primitives described above can be found in Recommendation T. 122 (Multipoint communication service for audiographics and audiovisual conferencing serv
41、ice definition). 4 Recommendation T.134 (02/98) 6.1 MCS channel usage . Table 6-2 describes MCS channel usage for CHATE sessions of the types defined in Recommendation T. 12 1. In the case of a Standard Base Session (see Recommendation T. 12 1) which uses the CHAT protocol, the Channel IDS shown in
42、Table 6-2 shall be used (symbolic IDS shown). For all other session types, the Application Registry Resource IDS shown in the table shall be used for allocating dynamic channels. The given Resource IDS shall be encoded as three-octet T.50 text strings using the characters shown in quotes in Table 6-
43、2. Mnemonic Channel IDS for Static Channel CHAT-CHANNEL CHAT- CHANNEL-O Application Registry Description Resource IDS for Dynamic Channels “T140“ (to be defined) This channel bears all CHATPDUs to be broadcast to all peer CHATEs in a domain. Table 6-3 lists the use of the MCS data service MCS-UNIFOR
44、M-SEND-DATA for the CHATPDU. This table includes the channel over which the data is sent and the data priority at which the data is sent. The CHAT protocol uses only the Medium MCS priority. The CHATPDUs specified in this Recommendation are placed in the Data parameter of the MCS-UNIFORM-SEND-DATA p
45、rimitive. The CHATPDUs are packed into the sequence of octets that form the Data parameter such that the leading bit is placed in the most significant bit of each octet, and filled toward the least significant bit of the octet. Table 6-3E.134 - Use of MCS data primitives for CHATPDUs I Prioriy I 1 C
46、HATPDU I Channel 1 ChatentryPDU 1 CHAT-CHANNEL I Medium I 7 Use of GCC The CHAT protocol may use the procedures defined for a Registration Session and a Standard Base Session in the manner specified in Recommendation T. 121 and shall use as its Application Protocol Key the Object Identifier defined
47、in Annex B. All CHATEs compliant with this Recommendation shall first enrol actively or inactively in the Registration Session using the procedures defined in Recommendation T. 12 1 and shall stay enrolled for as long as support for the CHAT protocol is to be indicated. CHATEs may enrol in a Public
48、Session or Private Session at their discretion using the procedures defined in Recommendation T. 12 1. When a session is in conducted mode, a CHATE may be restricted fiom sending data, depending on the GCC conducted-mode permission mechanism. If the node is given GCC conducted-mode permission, then
49、a CHATE may send any type of ChatPDU. If the node is not given GCC conducted-mode permission, then a CHATE shall not send any type of ChatPDU. Recommendation T.134 (02/98) 5 8 Protocol specification Parameter Chatstring; 8.1 CHAT sessions A CHAT session consists of one or more CHATEs enrolled within a conference as described in clause 7. CHATEs may join or leave the CHAT session at any time. Description One or more text and control items from the T.140 protocol 8.2 Capabilities There are no capabilities to negotiate for this protocol. 8.3 CHATPDU formats The CHATPDUs contain
