RTP Payload for Text Conversation
RFC 4103
| Document | Type |
RFC - Proposed Standard
(June 2005; Errata)
Obsoletes RFC 2793
|
|
|---|---|---|---|
| Last updated | 2018-12-20 | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4103 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | csp@csperkins.org, magnus.westerlund@ericsson.com | ||
Network Working Group G. Hellstrom
Request for Comments: 4103 Omnitor AB
Obsoletes: 2793 P. Jones
Category: Standards Track Cisco Systems, Inc.
June 2005
RTP Payload for Text Conversation
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This memo obsoletes RFC 2793; it describes how to carry real-time
text conversation session contents in RTP packets. Text conversation
session contents are specified in ITU-T Recommendation T.140.
One payload format is described for transmitting text on a separate
RTP session dedicated for the transmission of text.
This RTP payload description recommends a method to include redundant
text from already transmitted packets in order to reduce the risk of
text loss caused by packet loss.
Hellstrom & Jones Standards Track [Page 1]
RFC 4103 RTP Payload for Text Conversation June 2005
Table of Contents
1. Introduction ...................................................3
2. Conventions Used in This Document ..............................4
3. Usage of RTP ...................................................4
3.1. Motivations and Rationale .................................4
3.2. Payload Format for Transmission of text/t140 Data .........4
3.3. The "T140block" ...........................................5
3.4. Synchronization of Text with Other Media ..................5
3.5. RTP Packet Header .........................................5
4. Protection against Loss of Data ................................6
4.1. Payload Format When Using Redundancy ......................6
4.2. Using Redundancy with the text/t140 Format ................7
5. Recommended Procedure ..........................................8
5.1. Recommended Basic Procedure ...............................8
5.2. Transmission before and after "Idle Periods" ..............8
5.3. Detection of Lost Text Packets ............................9
5.4. Compensation for Packets Out of Order ....................10
6. Parameter for Character Transmission Rate .....................10
7. Examples ......................................................11
7.1. RTP Packetization Examples for the text/t140 Format ......11
7.2. SDP Examples .............................................13
8. Security Considerations .......................................14
8.1. Confidentiality ..........................................14
8.2. Integrity ................................................14
8.3. Source Authentication ....................................14
9. Congestion Considerations .....................................14
10. IANA Considerations ...........................................16
10.1. Registration of MIME Media Type text/t140 ...............16
10.2. SDP Mapping of MIME Parameters ..........................17
10.3. Offer/Answer Consideration ..............................17
11. Acknowledgements ..............................................18
12. Normative References ..........................................18
13. Informative References ........................................19
Hellstrom & Jones Standards Track [Page 2]
RFC 4103 RTP Payload for Text Conversation June 2005
1. Introduction
This document defines a payload type for carrying text conversation
session contents in RTP [2] packets. Text conversation session
contents are specified in ITU-T Recommendation T.140 [1]. Text
conversation is used alone or in connection with other conversational
facilities, such as video and voice, to form multimedia conversation
services. Text in multimedia conversation sessions is sent
character-by-character as soon as it is available, or with a small
delay for buffering.
The text is intended to be entered by human users from a keyboard,
handwriting recognition, voice recognition or any other input method.
The rate of character entry is usually at a level of a few characters
per second or less. In general, only one or a few new characters are
expected to be transmitted with each packet. Small blocks of text
may be prepared by the user and pasted into the user interface for
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