Indicating source of multi-party Real-time text
draft-hellstrom-avtcore-multi-party-rtt-source-02

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Last updated 2020-03-26
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Network Working Group                                       G. Hellstrom
Internet-Draft                                                   Omnitor
Updates: RFC 4102, RFC 4103 (if                           March 26, 2020
         approved)
Intended status: Standards Track
Expires: September 27, 2020

            Indicating source of multi-party Real-time text
           draft-hellstrom-avtcore-multi-party-rtt-source-02

Abstract

   Real-time text mixers for multi-party sessions need to identify the
   source of each transmitted group of text so that the text can be
   presented by endpoints in suitable grouping with other text from the
   same source.

   Regional regulatory requirements specify provision of real-time text
   in multi-party calls.  RFC 4103 mixer implementations can use
   traditional RTP functions for source identification, but the mixer
   source switching performance is limited when using the default
   transmission with redundancy.

   An enhancement for RFC 4103 real-time text mixing is provided in the
   present specification, suitable for a centralized conference model
   that enables source identification and efficient source switching.
   The intended use is for real-time text mixers and multi-party-aware
   participant endpoints.  The mechanism builds on use of the CSRC list
   in the RTP packet.

   A capability exchange is specified so that it can be verified that a
   participant can handle the multi-party coded real-time text stream.
   The capability is indicated by an sdp media attribute "rtt-mix".

   A brief description about how a mixer can format text for the case
   when the endpoint is not multi-party aware is also provided.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

Hellstrom              Expires September 27, 2020               [Page 1]
Internet-Draft     Indicate source of multi-party RTT         March 2020

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on September 27, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Nomenclature  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Intended application  . . . . . . . . . . . . . . . . . . . .   4
   4.  Use of fields in the RTP packets  . . . . . . . . . . . . . .   4
   5.  Actions at transmission by a mixer  . . . . . . . . . . . . .   5
   6.  Actions at reception  . . . . . . . . . . . . . . . . . . . .   6
   7.  RTCP considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Chained operation . . . . . . . . . . . . . . . . . . . . . .   7
   9.  Usage without redundancy  . . . . . . . . . . . . . . . . . .   8
   10. Use with SIP centralized conferencing framework . . . . . . .   8
   11. SDP Capability negotiation  . . . . . . . . . . . . . . . . .   8
   12. Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   13. Performance considerations  . . . . . . . . . . . . . . . . .  11
   14. Presentation level considerations . . . . . . . . . . . . . .  12
     14.1.  Presentation by multi-party aware endpoints  . . . . . .  12
     14.2.  Multi-party mixing for multi-party unaware endpoints . .  14
   15. Gateway Considerations  . . . . . . . . . . . . . . . . . . .  17
   16. Congestion considerations . . . . . . . . . . . . . . . . . .  17
   17. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   18. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   19. Security Considerations . . . . . . . . . . . . . . . . . . .  17
   20. Change history  . . . . . . . . . . . . . . . . . . . . . . .  18
     20.1.  Changes from version -00 to -01  . . . . . . . . . . . .  18
     20.2.  Changes from version -01 to -02  . . . . . . . . . . . .  18
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