Multiple Synchronization sources (SSRC) in RTP Session Signaling

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Last updated 2013-01-17 (latest revision 2012-07-16)
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RTP has always been a protocol that supports multiple participants each sending their own media streams in an RTP session. Unfortunately, many implementations are designed only for point to point voice over IP with a single source in each end-point. Even client implementations aimed at video conferences have often been built with the assumption around central mixers that only deliver a single media stream per media type. Thus any application that wants to allow for more advanced usage, where multiple media streams are sent and received by an end-point, has an issue with legacy implementations. This document describes the problem and proposes a signalling solution for how to use multiple SSRCs within one RTP session and at the same time handle the legacy issues.


Magnus Westerlund (
BoB (
Fredrik Jansson (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)