T.140 Real-time Text Conversation over WebRTC Data Channels
draft-ietf-mmusic-t140-usage-data-channel-03
MMUSIC Working Group C. Holmberg
Internet-Draft Ericsson
Updates: RFC8373 (if approved) September 17, 2019
Intended status: Standards Track
Expires: March 20, 2020
T.140 Real-time Text Conversation over WebRTC Data Channels
draft-ietf-mmusic-t140-usage-data-channel-03
Abstract
This document specifies how a WebRTC data channel can be used as a
transport mechanism for Real-time text using the ITU-T Protocol for
multimedia application text conversation (Recommendation ITU-T
T.140), and how the SDP offer/answer mechanism can be used to
negotiate such data channel, referred to as T.140 data channel.
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Holmberg Expires March 20, 2020 [Page 1]
Internet-Draft T.140 Data Channel September 2019
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. WebRTC Data Channel Considerations . . . . . . . . . . . . . 3
4. SDP Considerations . . . . . . . . . . . . . . . . . . . . . 4
4.1. Use of dcmap Attribute . . . . . . . . . . . . . . . . . 4
4.2. Use of dcsa Attribute . . . . . . . . . . . . . . . . . . 5
4.2.1. Maximum Character Transmission . . . . . . . . . . . 5
4.2.2. Real-time Text Conversation Languages . . . . . . . . 5
4.2.3. Real-time Text Direction . . . . . . . . . . . . . . 5
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 7
5. T.140 Considerations . . . . . . . . . . . . . . . . . . . . 9
5.1. Session Layer Functions . . . . . . . . . . . . . . . . . 9
5.2. Data Encoding and Sending . . . . . . . . . . . . . . . . 10
5.3. Data Buffering . . . . . . . . . . . . . . . . . . . . . 10
5.4. Loss of T140blocks . . . . . . . . . . . . . . . . . . . 10
5.5. Multi-party Considerations . . . . . . . . . . . . . . . 11
6. Gateway Considerations . . . . . . . . . . . . . . . . . . . 11
7. Update to RFC 8373 . . . . . . . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 12
9. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13
9.1. Subprotocol Identifier t140 . . . . . . . . . . . . . . . 13
9.2. SDP fmtp Attribute . . . . . . . . . . . . . . . . . . . 13
9.3. SDP Language Attributes . . . . . . . . . . . . . . . . . 13
9.4. SDP Media Direction Attributes . . . . . . . . . . . . . 14
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
11.1. Normative References . . . . . . . . . . . . . . . . . . 16
11.2. Informative References . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
The ITU-T Protocol for multimedia application text conversation
(Recommendation ITU-T T.140) [T140] defines a protocol for text
conversation, also known as real-time text. The native transport for
IP networks is the "RTP Payload for Text Conversation" [RFC4103]
mechanism, based on the Real-time Transport Protocol (RTP) [RFC4103].
This document specifies how a WebRTC data channel
[I-D.ietf-rtcweb-data-channel] can be used as a transport mechanism
for T.140, and how the SDP offer/answer mechanism
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