[AVTCORE] I-D Action: draft-hellstrom-avtcore-multi-party-rtt-solutions-03.txt

Gunnar Hellström <gunnar.hellstrom@ghaccess.se> Sun, 09 August 2020 14:10 UTC

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Subject: [AVTCORE] I-D Action: draft-hellstrom-avtcore-multi-party-rtt-solutions-03.txt
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Thee is a new version of 
draft-hellstrom-avtcore-multi-party-rtt-solutions available.

The main differences are that the performance requirements are more 
elaborated, and clear recommended solutions provided with preference for 
rapidly standardised and easily implemented solutions.

The topic was presented and briefly discussed in IETF 108.

Here is a link to the presentation:


The focus is now proposed to be on the method for mixing for multi-party 
unaware endpoints based on RTP and on the RTP-mixer based version using 
RFC 4103 with 100 ms transmission interval when  more than one 
participant is sending text simultaneously.


A New Internet-Draft is available from the on-line Internet-Drafts 

Title : Real-time text solutions for multi-party sessions
Author : Gunnar Hellstrom
Filename : draft-hellstrom-avtcore-multi-party-rtt-solutions-03.txt
Pages : 45
Date : 2020-08-08

This document specifies methods for Real-Time Text (RTT) media
handling in multi-party calls. The main discussed transport is to
carry Real-Time text by the RTP protocol in a time-sampled mode
according to RFC 4103. The mechanisms enable the receiving
application to present the received real-time text media, separated
per source, in different ways according to user preferences. Some
presentation related features are also described explaining suitable
variations of transmission and presentation of text.

Call control features are described for the SIP environment. A
number of alternative methods for providing the multi-party
negotiation, transmission and presentation are discussed and a
recommendation for the main ones is provided. The main solution for
SIP based centralized multi-party handling of real-time text is
achieved through a media control unit coordinating multiple RTP text
streams into one RTP stream.

Alternative methods using a single RTP stream and source
identification inline in the text stream are also described, one of
them being provided as a lower functionality fallback method for
endpoints with no multi-party awareness for RTT.

Bridging methods where the text stream is carried without the
contents being dealt with in detail by the bridge are also discussed.

Brief information is also provided for multi-party RTT in the WebRTC

The intention is to provide background for decisions, specification
and implementation of selected methods.

The IETF datatracker status page for this draft is:

There are also htmlized versions available at:

A diff from the previous version is available at:

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at: