Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP

Cullen Jennings <fluffy@iii.ca> Thu, 10 May 2012 22:29 UTC

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From: Cullen Jennings <fluffy@iii.ca>
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Date: Thu, 10 May 2012 16:29:21 -0600
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To: Roman Shpount <roman@telurix.com>
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Cc: Randell Jesup <randell-ietf@jesup.org>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] SDP_PRANSWER followed by SDP_OFFER scenario in JSEP
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On May 10, 2012, at 3:23 PM, Roman Shpount wrote:

> 
> On Thu, May 10, 2012 at 4:55 PM, Cullen Jennings <fluffy@iii.ca> wrote:
> > One use case is interop with SIP with parallel forking, reliable provisioning responses, UPDATE, and ICE. The big question regarding this use case is availability of anything that supports parallel forking, reliable provisioning and UPDATE. I actually think ICE makes implementation of this use case easier, not harder.
> 
> So let me try and make sure I understand this uses case. The web browser sends some signaling to a server that convert it to a sip call to the fork@example.com address. This sends it to theexample.com sip server that parallel forks it to two SIP UASs  that are so two phones ring at the same time. Now both theses phones are going to negotiate ICE by using reliably provisional responses.
> 
> What products actually do parallel forking like this and return provisional reliable responses with ICE. I'm sort of questioning this is a common use case. The Nortel, Cisco, Avaya, Siemens etc enterprises PBX systems I have seen that support ringing multiple phones at the same time don't seem to do this way. They manage to hide the parallel forking with a B2BUA model and make it look like sequential forking.
> 
> 
> Let's say a standard SIP proxy (call it opensips for specificity) placing a forked call to two ICE enabled IP phones. Both phones answer with 200 OK.

With a standard SIP proxy, only one of the 200 would be sent back to the web browser.