Re: [AVT] SSRC to DTLS-SRTP mapping

[Eric Rescorla <ekr at networkresonance.com>]

At Tue, 19 Feb 2008 13:35:52 +0100,
John W. Floroiu wrote:
> 
> 
> Hello,
> 
> regarding the first error case that you mention, which would translate 
> for instance in both Bob and Charlie sending both of them media streams 
> with SSRC=1, what would happen if the media stream from Bob arrives 
> first (and triggers the SSRC mapping) but Alice's UA actually cancels 
> the call with Bob (because for instance the 200 OK from Charlie arrived 
> first)?

Good point. I hadn't thought of that issue. 

However, since you know which DTLS-SRTP associations are bound to
which fork, you can simply remove the entry from the table and
then when Charlie's next packet comes in it will automatically
get mapped into the table. Obviously, this means that you'll
start by playing Bob's voice and then Charlie's but that's
inherent in this RTP-level SSRC collision strategy, I think.

-Ekr
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