RTP-mixer formatting of multi-party Real-time text
draft-ietf-avtcore-multi-party-rtt-mix-08

Document Type Active Internet-Draft (avtcore WG)
Last updated 2020-08-12
Replaces draft-hellstrom-avtcore-multi-party-rtt-source
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AVTCore                                                     G. Hellstrom
Internet-Draft                 Gunnar Hellstrom Accessible Communication
Updates: RFC 4103 (if approved)                           12 August 2020
Intended status: Standards Track                                        
Expires: 13 February 2021

           RTP-mixer formatting of multi-party Real-time text
               draft-ietf-avtcore-multi-party-rtt-mix-08

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 characteristics with redundancy.

   Enhancements for RFC 4103 real-time text mixing is provided in this
   document, suitable for a centralized conference model that enables
   source identification and source switching.  The intended use is for
   real-time text mixers and multi-party-aware participant endpoints.
   The specified mechanism build on the standard use of the CSRC list in
   the RTP packet for source identification.  The method makes use of
   the same "text/red" format as for two-party sessions.

   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 use of a media attribute "rtt-mix-rtp-
   mixer".

   The document updates RFC 4103[RFC4103]

   A specifications of 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.

Hellstrom               Expires 13 February 2021                [Page 1]
Internet-Draft    RTP-mixer format for multi-party RTT       August 2020

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   This Internet-Draft will expire on 13 February 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   Please review these documents carefully, as they describe your rights
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Selected solution and considered alternative  . . . . . .   4
     1.2.  Nomenclature  . . . . . . . . . . . . . . . . . . . . . .   6
     1.3.  Intended application  . . . . . . . . . . . . . . . . . .   7
   2.  Specified solutions . . . . . . . . . . . . . . . . . . . . .   7
     2.1.  Negotiated use of the RFC 4103 format for multi-party in a
           single RTP stream . . . . . . . . . . . . . . . . . . . .   7
     2.2.  Mixing for multi-party unaware endpoints  . . . . . . . .  19
   3.  Presentation level considerations . . . . . . . . . . . . . .  19
     3.1.  Presentation by multi-party aware endpoints . . . . . . .  20
     3.2.  Multi-party mixing for multi-party unaware endpoints  . .  22
   4.  Gateway Considerations  . . . . . . . . . . . . . . . . . . .  27
     4.1.  Gateway considerations with Textphones (e.g.  TTYs).  . .  28
     4.2.  Gateway considerations with WebRTC. . . . . . . . . . . .  28
   5.  Updates to RFC 4103 . . . . . . . . . . . . . . . . . . . . .  29
   6.  Congestion considerations . . . . . . . . . . . . . . . . . .  29
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  29
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  29
     8.1.  Registration of the "rtt-mix-rtp-mixer" sdp media
           attribute . . . . . . . . . . . . . . . . . . . . . . . .  29

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