T.140 Real-time Text Conversation over WebRTC Data Channels
draft-ietf-mmusic-t140-usage-data-channel-10

Document Type Active Internet-Draft (mmusic WG)
Last updated 2019-12-10
Replaces draft-holmberg-mmusic-t140-usage-data-channel
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state WG Consensus: Waiting for Write-Up
Document shepherd Flemming Andreasen
IESG IESG state I-D Exists
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Send notices to Flemming Andreasen <fandreas@cisco.com>
MMUSIC Working Group                                         C. Holmberg
Internet-Draft                                                  Ericsson
Updates: 8373 (if approved)                            December 11, 2019
Intended status: Standards Track
Expires: June 13, 2020

      T.140 Real-time Text Conversation over WebRTC Data Channels
              draft-ietf-mmusic-t140-usage-data-channel-10

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.  The
   document updates RFC 8373.

Status of This Memo

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   This Internet-Draft will expire on June 13, 2020.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Holmberg                  Expires June 13, 2020                 [Page 1]
Internet-Draft             T.140 Data Channel              December 2019

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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 Rate . . . . . . . . .   5
       4.2.2.  Real-time Text Conversation Languages . . . . . . . .   6
       4.2.3.  Real-time Text Direction  . . . . . . . . . . . . . .   6
     4.3.  Examples  . . . . . . . . . . . . . . . . . . . . . . . .   8
   5.  T.140 Considerations  . . . . . . . . . . . . . . . . . . . .  10
     5.1.  Session Layer Functions . . . . . . . . . . . . . . . . .  10
     5.2.  Data Encoding and Sending . . . . . . . . . . . . . . . .  11
     5.3.  Data Buffering  . . . . . . . . . . . . . . . . . . . . .  11
     5.4.  Loss of T140blocks  . . . . . . . . . . . . . . . . . . .  11
     5.5.  Multi-party Considerations  . . . . . . . . . . . . . . .  12
   6.  Gateway Considerations  . . . . . . . . . . . . . . . . . . .  12
   7.  Update to RFC 8373  . . . . . . . . . . . . . . . . . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  IANA considerations . . . . . . . . . . . . . . . . . . . . .  14
     9.1.  Subprotocol Identifier t140 . . . . . . . . . . . . . . .  14
     9.2.  SDP fmtp Attribute  . . . . . . . . . . . . . . . . . . .  14
     9.3.  SDP Language Attributes . . . . . . . . . . . . . . . . .  15
     9.4.  SDP Media Direction Attributes  . . . . . . . . . . . . .  16
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     11.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  19

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 transport used for
   IP networks is the "RTP Payload for Text Conversation" [RFC4103]
   mechanism, based on the Real-time Transport Protocol (RTP) [RFC3550].

   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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