1、 STD=ITU-T RECMN TmL40-ENGL 1998 = 4862591 Ob48995 LTT INTERNATIONAL TELECOMMUNICATION UNION lTU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU T.140 (02198) SERIES T: TERMINALS FOR TELEMATIC SERVICES Protocol for multimedia application text conversation ITU-T Recommendation T. 140 (Previously CC
2、ITT Recommendation) ITU-T T-SERI ES RECOMMENDATIONS TERMINALS FOR TELEMATIC SERVICES For further details, please refer to PU-T List of Recommendations. STD-ITU-T RECMN T-140-ENGL 1998 Y862591 Ob48997 T72 ITU-T RECOMMENDATION T.140 PROTOCOL FOR MULTIMEDIA APPLICATION TEXT CONVERSATION Summary This Re
3、commendation specifies a text conversation protocol. The intention of this protocol is to be a common presentation level suitable for straightforward real-time text conversation in multimedia services and in text telephony. It is based on ISOAEC 10646-1 Universal Character Set 16-bit characters and
4、features character-by-character transmission and a limited set of presentation controls. Its application to the data conferencing environment is specified in Recommendation T. 134. Its application for plain text telephony in the PSTN is specified in Recommendation V. 18. Its application in video tel
5、ephony is specified in Recommendations H.324 and H.245. It is meant to be easily applied wherever there is a data channel available to carry the protocol. Source ITU-T Recommendation T.140 was prepared by ITU-T Study Group 16 (1997-2000) and was approved under the WTSC Resolution No. 1 procedure on
6、the 6th of February 1998. - STDmITU-T RECMN T-l4O-ENGL 1998 48b2591 Ob48998 909 FOREWORD IT (International 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 IT. Th
7、e 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 Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics
8、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 Resolution No. 1. In some areas of information technology which fall within ITU-T?s purview, th
9、e necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression ?Administration? is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS The IT draws attentio
10、n 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 concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or other
11、s outside of the Recommendation development process. As of the date of approval 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 repres
12、ent 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 reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in
13、 writing from the ITU. Recommendation T.140 (02/98) 11 1 2 3 4 5 6 6.1 6.2 7 7.1 8 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 CONTENTS Page Background . Scope References Definitions Abbreviations . Protocol . Required session control functions . Requirements on the data transmission functions . Presentation pr
14、otocol functions 6.1.1 Code elements Code signature and synchronization . Detailed coding and procedures . Text . Erase last character . New line Alert user in session Interrupt Application protocol function . Select graphic rendition Identie UCS subset Appendix I . Display arrangements 1 2 2 2 3 3
15、3 4 4 5 6 8 . Recommendation T.140 (02/98) 111 Recommendation T.140 PROTOCOL FOR MULTIMEDIA APPLICATION TEXT CONVERSATION (Geneva, 1998) 1 Background This is a brief description of the application environment where the protocol is intended to be used. Text entered at one terminal is distributed to o
16、ther terminals participating in the same session. Text entered by one terminal is displayed in a window on that terminal and on others included in the session. The character set is 16-bit ISO/IEC 10646-1 level 3, used in order to be useful on all markets with no or little extra configuration problem
17、s. The intention to use a specific subset of ISO/IEC 10646- 1 can be signalled in the protocol. The normal case is to transmit and display character by character as they are entered. Short time buffering (0.5 s) may be introduced by the transport mechanism in some configurations to reduce overhead.
18、If used, the buffering is part of the transport mechanism used and is beyond the scope of this Recommendation. The text entries from the different participants should be displayed in such a way that they can be easily read and the order of the entries perceived. In case of multipoint use, the origin
19、 of the text should be displayed in connection to the text. The supporting multipoint protocol is assumed to supply the identification. If characters fiom languages with writing directions right to left are supported, the implicit writing direction should also be supported according to rules in ISOA
20、EC 10646- 1. Editing and control functions fiom ISO/IEC 6429 and ISO/IEC 10646-1 are included for: - New line; - Erase last character; - - Select graphic rendition. A mechanism is defined for extending the protocol without disturbing communication with terminals implementing only limited versions. S
21、ession control and transmission functions are needed fiom the implementation environment for: - - - Accepting a session; - Ending a session; - Transport the protocol data. Alert the user during a session; Initiating and identiing a session; Alerting on incoming calls (activate external signals; visu
22、al, audible or tactile); Recommendation T.140 (0298) 1 11) The protocol is suitable for application in: - Point-to-point situations; - Multipoint conferencing when the session control functions provide the multipoint distribution services. 12) Support for use of the protocol is foreseen: - in pure t
23、ext conversation situations, or in combination with. voice, video, data conferencing; or in any combination of the above modes. - 2 Scope This Recommendation specifies a simple text conversation protocol. Its purpose is to offer a standardized way to perform conversations in text mode between termin
24、als. The described protocol is intended to be used in the following environments: As the text conversation protocol used between two devices using Recommendation V. 18 O As the text conversation protocol between nodes in a point-to-point or multipoint As the point-to-point text conversation protocol
25、 between multimedia terminals using a modems for text telephony; multimedia conference as specified in Recommendation T. 134; logical data channel transport mechanism in cases when T. 120 functionality is not available. O 3 References The following ITU-T Recommendations and other references contain
26、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 Recommendation are therefore encouraged to investigate th
27、e possibility of applying the most recent editions of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. - - ITU-T Recommendation T. 134 (1 998), Text chat application protocol entity. ITU-T Recommendation V. 18 (1 998),
28、 Operational and interworking requirements for DCEs operating in the text telephone mode. ISOfIEC 6429: 1992, Information technology - Controlfunctions for coded character sets. Character Set (UCS) - Part 1 : Architecture and Basic Multilingual Plane. - - ISO/IEC 10646-1 : 1993, Information technolo
29、gy - Universal Multiple-Octet Coded 4 Definitions This Recommendation defines the following terms: 4.1 purpose of exchanging information in text format on a real-time basis. session: A session is a logical connection between two or more user terminals for the 2 Recommendation T.140 (02/98) STD-ITU-T
30、 RECMN T.Ii4O-ENGL 1998 m 4862591 Ob49002 T38 m 4.2 node: A terminal or group of terminals. A node can also incorporate a MCU for the purpose of coordinating multipoint sessions. 4.3 data channels: A communication path used to carry text and presentation control information. 4.4 origin identificatio
31、n: The user terminal may have an origin identification that can be used to identiQ the display of text fiom that terminal. The origin is specified by the surrounding transport protocol. 5 Abbreviations This Recommendation uses the following abbreviations: MCU Multipoint Control Unit UCS UTF UCS Tran
32、sformation Format Universal Multiple-Octet Coded Character Set 6 Protocol This Recommendation only addresses the session contents. The procedures used to establish a session are beyond the scope of this Recommendation. 6.1 Required session control functions The session control functions are implemen
33、ted with functions external to the channel and may be different for each transport mechanism. Although not part of this Recommendation, the following parameters and functions are required and should be specified for each implementation environment. - - - - User identity: - Data: Data for transmissio
34、n fiom the text conversation protocol. During session establishment, the protocol identity connected to Recommendation T. 140 should be signalled. The following conceptual session functions are needed to support a T. 140 session. Protocol identity: Destination node: Originating node: Registered valu
35、e for the initial version of the T. 140 protocol. An address valid in the environment where the protocol is used. An address for the node where the text origins. Name and other valid identifications for an end user. Recommendation T.140 (0298) 3 STD-ITU-T RECMN T-lLiO-ENGL 1998 = 4862591 Ob49003 774
36、 = Function title Table 1rn.140 - Functions in the session layer Purpose _ Disconnect session Leave a session Data Transmit data to one or all members of a session Prepare session Announce readiness to accept invitations to sessions (may be a local function) Initiate session Ask for a session with a
37、 specified 1 node I Accept session I Accept to enter a session I Deny session I Refuse to enter a session Parameters Supported T. 140 protocol Destination node, originating node and user identity, T. 140 protocol Accepted protocol, accepting user identity Refusing user identity Data from the present
38、ation protocol, destination node or all 6.1.1 A data channel is set up with mechanisms specific to each environment where the protocol is implemented. Text is transmitted to the data channel from the text conversation protocol character by character. The requirements and the specific mechanisms for
39、buffering are beyond the scope of this Recommendation. However, if buffering is provided in the data channel, it should not delay transmission more than 0.5 s and should not be related to complete lines of input. Any grouping of data into blocks for transmission should be transparent to the text pro
40、tocol. Data from one node shall be delivered in the same order as it was transmitted. Requirements on the data transmission functions 6.2 Presentation protocol functions The protocol functions of the protocol are invoked by transmission of protocol data elements in the channel established by the ses
41、sion control functions. The following parameters are used in specific protocol functions. Parameter Purpose Text content Display characteristics UCS subset Function Protocol function. Table 2 gives an overview over the presentation protocol functions. Text fiom one source in a session. As defined in
42、 SGR of ISO/IEC 6429. An ISO-registered subset of ISOAEC 10646-1. 4 Recommendation T. 140 (02198) STD-ITU-T RECMN T.340-ENGL 1778 4862573 0649004 800 Function Alert user in session Erase last character IdentiSr UCS subset Interrupt New line Text Application protocol function Select graphic rendition
43、 Purpose Parameters Intended to cause an alerting signal from the user terminal during a session Used to erase the last character Indicate intended subset within Initiate mode change Move current display position to the next line Text to display in conversation Extended control function Suggests dis
44、play attributes for the following text characteristics UCS subset ISODEC 10646- 1 A character of text Function and parameters (to be defined) Colours, fonts and other display 7 Code elements Characters shall be sent, ordered in octets. If implemented in a user terminal, the terminal should also prov
45、ide for local display of transmitted characters. The character set shall conform to the two-octet version of ISOAEC 10646-1. All terminals implementing this Recommendation shall support the characters in the “IRV“ and “Latin-1 supplement“ in ISOAEC 10646-1. Support for other parts of ISOAEC 10646-1
46、is optional. SO/IEC 6429 Presentation control functions are coded according to the principles of ISO/IEC 6429. control functions shall be padded with O0 characters as specified in ISOIEC 10646-1. In transmission, all code elements shall be transformed to the UTF-8 form of ISO/IEC The following contr
47、ol sequences are included in this protocol. Usage Name BEL BS NEW LINE CR LF INT SGR SOS Code 0007 0008 2028 000D 000A ESC 0061 009B Ps 006D 0098 0646- 1. Bell: Provides for alerting during an active session. Back Space: Erases the last entered character. Line separator. A supported, but not preferr
48、ed, way of requesting a new line. Interrupt (used to initiate mode negotiation procedure). Select Graphic Rendition: Ps is rendition parameters specified in ISOIEC 6429. Start of String: Used as a general protocol element introducer. Recommendation T.140 (02/98) 5 ST 009C String Terminator: End of S
49、OS string. ESC 001B Escape: Used in control strings. Byte order mark FEFF Zero width, no-break space: Used for synchronization. 7.1 Code signature and synchronization The ZERO WIDTH NO-BREAK SPACE character (FEFF) shall be inserted in the beginning of the session. The reception of ZERO WIDTH NO-BREAK SPACE shall be used as a tool to verifj the right byte- order within the characters (see ISOAEC 10646-1). 8 Detailed coding and procedures 8.1 Text Purpose: Transfer text to display as text in the receiving window of the peer terminal(
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