Re: [rtcweb] Relaxing SDP O/A (was RE: Agenda requests for Atlanta meeting)

worley@ariadne.com (Dale R. Worley) Thu, 18 October 2012 18:18 UTC

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Subject: Re: [rtcweb] Relaxing SDP O/A (was RE: Agenda requests for Atlanta meeting)
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> From: Matthew Kaufman <matthew.kaufman@skype.net>
>
> The JSEP API enforces no such rules. If you want to change the API
> to bring it into compliance with *just this section* of 3264, it
> would need all sorts of changes...

I'm not familiar with the details of JSEP, but on general
architectural principles, my suspicion is that the key regarding
interworking with SIP is not whether a JSEP-using application can send
offers at times that the 3264 offer/answer model forbids it, but
rather whether JSEP/WebRTC can *reject* an offer.

Certainly in SIP, a new offer presented in a re-INVITE or UPDATE
request can be rejected by the other UA by returning a failure
response.  Any WebRTC protocol that can interwork smoothly with SIP
will require this capability.

Given that, if the JSEP model permits an application to send offers at
times when SIP does not, the WebRTC/SIP gateway/server can immediately
send rejection of such offers back to the client, without sending a
SIP request containing the offer.

This approach tolerates considerable difference between the rules
enforced by JSEP and the rules enforced by SIP, which may be
convenient.

Dale