Subject: RE: [AVT] Vorbis RTP issues list for Vienna

From: "Rosen, Brian" <[email-masked]>
Date: Tue, 15 Jul 2003 07:25:42 -0400

> The keys to the data need to be delivered "at least as 
> reliably" as the 
> data but not necessarily "reliably."  Putting keys in the 
> data packet is 
> one such method, but we are not likely to use this method in 
> RTP (poor 
> separation of functions, no third-party key mgt, etc).  But 
> there have been 
> proposals for using RTCP or SRTCP.  Rather than extend RTCP 
> or SRTCP for 
> this purpose, however, a better approach IMHO is to put the 
> key in the SDP 
> and send it "at least as reliably" as the SRTP.  The SDP must 
> of course be 
> authenticated/integrity-checked and encrypted.
I'm not sure this is a good idea.  At least in SIP, the
media path is considerably different, and in most cases,
considerably shorter than the signalling path, because
the signalling path has intermediaries that the media
path does not.  Key change is not something I would
want to see delayed by the intermediaries.  It really
is a "real time" transport problem, although somewhat
less real time than the actual media.
Passing keys may be best done in the media path.  

Brian

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