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RTP Payload for Text Conversation (RFC2793)

IP.com Disclosure Number: IPCOM000003392D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 8 page(s) / 19K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

G. Hellstrom: AUTHOR

Abstract

This memo describes how to carry text conversation session contents in RTP packets. Text conversation session contents are specified in ITU-T Recommendation T.140 [1].

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 15% of the total text.

Network Working Group G. Hellstrom

Request for Comments: 2793 Omnitor AB

Category: Standards Track May 2000

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 (2000). All Rights Reserved.

Abstract

This memo describes how to carry text conversation session contents

in RTP packets. Text conversation session contents are specified in

ITU-T Recommendation T.140 [1].

Text conversation is used alone or in connection to other

conversational facilities such as video and voice, to form multimedia

conversation services.

This RTP payload description contains an optional possibility to

include redundant text from already transmitted packets in order to

reduce the risk of text loss caused by packet loss. The redundancy

coding follows RFC 2198.

1. Introduction

This memo defines a payload type for carrying text conversation

session contents in RTP packets. Text conversation session contents

are specified in ITU-T Recommendation T.140 [1]. Text conversation is

used alone or in connection to other conversational facilities such

as video and voice, to form multimedia conversation services. Text in

text conversation sessions is sent as soon as it is available, or

with a small delay for buffering.

The text is supposed 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. Therefore, the expected number of characters to

transmit is low. Only one or a few new characters are expected to be

transmitted with each packet.

T.140 specifies that text and other T.140 elements MUST be

transmitted in ISO 10 646-1 code with UTF-8 transformation. That

makes it easy to implement internationally useful applications, and

to handle the text in modern information technology environments.

The payload of an RTP packet following this specification consists of

text encoded according to T.140 without any additional framing. A

common case will be a single ISO 10646 character, UTF-8 encoded.

T.140 requires the transport channel to provide characters without

duplication and in original order. Text conversation users expect

that text will be delivered with no or a low level of lost

information. If lost information can be indicated, the willingness to

accept loss is expected to be higher.

Therefore a mechanism based on RTP is specified here. It gives text