Re: [rtcweb] CNAMEs and multiple peer connections

Magnus Westerlund <> Wed, 05 March 2014 12:44 UTC

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Date: Wed, 05 Mar 2014 12:44:16 +0000
From: Magnus Westerlund <>
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Subject: Re: [rtcweb] CNAMEs and multiple peer connections
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On 2014-03-05 10:04, Martin Thomson wrote:
> I haven't thought about this in detail yet, but I wanted to ensure
> that this issue is tracked.  I think that our chairs might be able to
> create an issue in some tracker.  Can I request that they do that for
> this issue?

I will currently not stuff anything into our tracker.

However, I will give a bit of context from what the rtp-usage says about

On the receiver side, we have a clear requirement on handling multiple
CNAMEs in Section 11.

   A WebRTC endpoint MUST support receiving multiple MediaStreamTracks,
   where each of different MediaStreamTracks (and their sets of
   associated packet streams) uses different CNAMEs.  However,
   MediaStreamTracks that are received with different CNAMEs have no
   defined synchronisation.

On the sending side the text says the following:

   The same MediaStreamTrack can also be included in multiple
   MediaStreams, thus multiple sets of MediaStreams can implicitly need
   to use the same synchronisation base.  To ensure that this works in
   all cases, and don't forces a endpoint to change synchronisation base
   and CNAME in the middle of a ongoing delivery of any packet streams,
   which would cause media disruption; all MediaStreamTracks and their
   associated SSRCs originating from the same endpoint MUST be sent
   using the same CNAME within one RTCPeerConnection as well as across
   all RTCPeerConnections part of the same communication session
   context, which for a browser are a single origin.

Martin, you talked about linking in this context. I wonder if there
really are an issue with linking as this is all in the same
communication context. Can you please make clear your concerns?


Magnus Westerlund

Services, Media and Network features, Ericsson Research EAB/TXM
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