Using Simulcast in SDP and RTP Sessions

Approval announcement
Draft of message to be sent after approval:

From: The IESG <>
To: IETF-Announce <>
Cc:,, The IESG <>,,,,
Subject: Protocol Action: 'Using Simulcast in SDP and RTP Sessions' to Proposed Standard (draft-ietf-mmusic-sdp-simulcast-13.txt)

The IESG has approved the following document:
- 'Using Simulcast in SDP and RTP Sessions'
  (draft-ietf-mmusic-sdp-simulcast-13.txt) as Proposed Standard

This document is the product of the Multiparty Multimedia Session Control
Working Group.

The IESG contact persons are Adam Roach, Alexey Melnikov and Ben Campbell.

A URL of this Internet Draft is:

Technical Summary

In some application scenarios it may be desirable to send multiple differently encoded versions of the same media source in different RTP streams.  This is called simulcast.  This document describes how to accomplish simulcast in RTP and how to signal it in SDP.  The described solution uses an RTP/RTCP identification method to identify RTP streams belonging to the same media source, and makes an extension to SDP to relate those RTP streams as being different simulcast formats of that media source.  The SDP extension consists of a new media level SDP attribute that expresses capability to send and/or receive simulcast RTP streams.

Working Group Summary

There was nothing in particular worth noting. There has been a few different simulcast proposals in the past, however once this proposal was made and adopted by the WG, progress and consensus has been smooth. 

Document Quality

The document is part of the RTCWeb suite of specifications. There is currently one known partial implementation of the specification. 


Flemming Andreasen is the Document Shepherd. Ben Campbell is the Responsible Area Director.