RTP-mixer formatting of multi-party Real-time text
draft-ietf-avtcore-multi-party-rtt-mix-13

Document Type Active Internet-Draft (avtcore WG)
Author Gunnar Hellstrom 
Last updated 2021-02-11 (latest revision 2021-02-10)
Replaces draft-hellstrom-avtcore-multi-party-rtt-source
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication (wg milestone: Feb 2021 - Submit RTP Mixer For... )
Doc Shepherd Follow-up Underway
Document shepherd Bernard Aboba
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IESG IESG state AD Evaluation
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AVTCore                                                     G. Hellstrom
Internet-Draft                 Gunnar Hellstrom Accessible Communication
Updates: 4103 (if approved)                             10 February 2021
Intended status: Standards Track                                        
Expires: 14 August 2021

           RTP-mixer formatting of multi-party Real-time text
               draft-ietf-avtcore-multi-party-rtt-mix-13

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, while new text from other sources is also presented in
   readable grouping as received interleaved in real-time.

   Use of RTT is increasing, and specifically, use in emergency calls is
   increasing.  Emergency call use requires multi-party mixing.  RFC
   4103 "RTP Payload for Text Conversation" mixer implementations can
   use traditional RTP functions for source identification, but the
   performance of the mixer when giving turns for the different sources
   to transmit is limited when using the default transmission
   characteristics with redundancy.

   Enhancements for RFC 4103 real-time text mixing are provided in this
   document, suitable for a centralized conference model that enables
   source identification and rapidly interleaved transmission of text
   from different sources.  The intended use is for real-time text
   mixers and participant endpoints capable of providing an efficient
   presentation or other treatment of a multi-party real-time text
   session.  The specified mechanism builds on the standard use of the
   CSRC list in the RTP packet for source identification.  The method
   makes use of the same "text/t140" and "text/red" formats as for two-
   party sessions.

   Solutions using multiple RTP streams in the same RTP session are
   briefly mentioned, as they could have some benefits over the RTP-
   mixer model.  The possibility to implement the solution in a wide
   range of existing RTP implementations made the RTP-mixer model be
   selected to be fully specified in this document.

   A capability exchange is specified so that it can be verified that a
   mixer and a participant can handle the multi-party coded real-time
   text stream using the RTP-mixer method.  The capability is indicated
   by use of an SDP media attribute "rtt-mixer".

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Internet-Draft    RTP-mixer format for multi-party RTT     February 2021

   The document updates RFC 4103 "RTP Payload for Text Conversation".

   A specification 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.

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

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 14 August 2021.

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
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   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   6
     1.2.  Selected solution and considered alternatives . . . . . .   6
     1.3.  Intended application  . . . . . . . . . . . . . . . . . .   9
   2.  Overview of the two specified solutions and selection of
           method  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     2.1.  The RTP-mixer based solution for multi-party aware
           endpoints . . . . . . . . . . . . . . . . . . . . . . . .  10
     2.2.  Mixing for multi-party unaware endpoints  . . . . . . . .  10
     2.3.  Offer/answer considerations . . . . . . . . . . . . . . .  11

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