T.140 Real-Time Text Conversation over WebRTC Data Channels
RFC 8865
Document | Type |
RFC - Proposed Standard
(January 2021; No errata)
Updates RFC 8373
|
|
---|---|---|---|
Authors | Christer Holmberg , Gunnar Hellstrom | ||
Last updated | 2021-01-19 | ||
Replaces | draft-holmberg-mmusic-t140-usage-data-channel | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html xml pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication (wg milestone: Mar 2020 - Submit T.140 Real-ti... ) | |
Document shepherd | Flemming Andreasen | ||
Shepherd write-up | Show (last changed 2019-12-19) | ||
IESG | IESG state | RFC 8865 (Proposed Standard) | |
Action Holders |
(None)
|
||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Murray Kucherawy | ||
Send notices to | Flemming Andreasen <fandreas@cisco.com> | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | RFC-Ed-Ack | ||
IANA expert review state | Expert Reviews OK |
Internet Engineering Task Force (IETF) C. Holmberg Request for Comments: 8865 Ericsson Updates: 8373 G. Hellström Category: Standards Track Gunnar Hellström Accessible Communication ISSN: 2070-1721 January 2021 T.140 Real-Time Text Conversation over WebRTC Data Channels Abstract This document specifies how a Web Real-Time Communication (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 Session Description Protocol (SDP) offer/answer mechanism can be used to negotiate such a data channel, referred to as a T.140 data channel. This document updates RFC 8373 to specify its use with WebRTC data channels. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8865. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction 2. Conventions 3. WebRTC Data Channel Considerations 4. SDP Considerations 4.1. Use of the 'dcmap' Attribute 4.2. Use of the 'dcsa' Attribute 4.2.1. Maximum Character Transmission Rate 4.2.2. Real-Time Text Conversation Languages 4.2.3. Real-Time Text Direction 4.3. Examples 5. T.140 Considerations 5.1. Session-Layer Functions 5.2. Data Encoding and Sending 5.3. Data Buffering 5.4. Loss of T140blocks 5.5. Multi-party Considerations 6. Gateway Considerations 7. Update to RFC 8373 8. Security Considerations 9. IANA Considerations 9.1. Subprotocol Identifier "t140" 9.2. SDP 'fmtp' Attribute 9.3. SDP Language Attributes 9.4. SDP Media Direction Attributes 10. References 10.1. Normative References 10.2. Informative References Acknowledgements Authors' Addresses 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" mechanism [RFC4103], based on the Real-time Transport Protocol (RTP) [RFC3550]. This document specifies how a Web Real-Time Communication (WebRTC) data channel [RFC8831] can be used as a transport mechanism for T.140 and how the Session Description Protocol (SDP) offer/answer mechanism for data channels [RFC8864] can be used to negotiate such a data channel. In this document, a T.140 data channel refers to a WebRTC data channel for which the instantiated subprotocol is "t140" and where the channel is negotiated using the SDP offer/answer mechanism [RFC8864]. | NOTE: The decision to transport real-time text using a WebRTC | data channel instead of using RTP-based transport [RFC4103] is | motivated by use case "U-C 5: Real-time text chat during an | audio and/or video call with an individual or with multiple | people in a conference"; see Section 3.2 of [RFC8831]. The brief notation "T.140" is used as a name for the text conversation protocol according to [T140]. Real-time text is intended to be entered by human users via 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. Section 3 defines the generic data channel properties for a T.140 data channel, and Section 4 defines how they are conveyed in an SDP 'dcmap' attribute. While this document defines how to negotiate a T.140 data channel using the SDP offer/answer mechanism [RFC8864],Show full document text