[rtcweb] Forking -Re: SDP Offer/Answer draft-jennings-rtcweb-signaling

Cullen Jennings <fluffy@cisco.com> Tue, 18 October 2011 18:42 UTC

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From: Cullen Jennings <fluffy@cisco.com>
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Date: Tue, 18 Oct 2011 11:42:02 -0700
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To: Roman Shpount <roman@telurix.com>
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Cc: Jonathan Rosenberg <jonathan.rosenberg@skype.net>, rtcweb@ietf.org, public-webrtc@w3.org
Subject: [rtcweb] Forking -Re: SDP Offer/Answer draft-jennings-rtcweb-signaling
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On Oct 17, 2011, at 17:58 , Roman Shpount wrote:

> Cullen,
> Did we decide to explicitly not support forking which generates multiple final answers? If this is not the case, how is this supposed to be implemented using your model?

I think that it is critical that we support what is needed to make a call that goes to 1-800-go-fedex work. So 
consider the following use case: A browser calls through a signaling GW to a sip that forks the call to an SIP to PSTN gateway and also to a voicemail server. The PSTN gateway generates an 180 with ringback tone but the SIP call is eventually answered by the voicemail server that sends a 200. 
So 3264 supports forking by an single offer may result in say two answers. In the case above, an single offer resulted in two different answers. Roap would support this type of transaction by allowing two answers to be received. There are two ways this can happen - one is with different answererSessionId in the the answers. Another is the use of the More-coming flag. We think with these, one can support the range of what 3264 allows for offer/ answer. 

> _____________
> Roman Shpount
> On Fri, Oct 14, 2011 at 11:09 PM, Cullen Jennings <fluffy@cisco.com> wrote:
> Jonathan and I submitted a new draft on setting up media based on the SDP Offer/Answer model. The ASCII flows are a bit hard to read so until I update them, I recommend reading the PDF version at
> http://tools.ietf.org/pdf/draft-jennings-rtcweb-signaling-00.pdf
> Clearly the draft is an early stage but we plan to revise it before the deadline for the IETF 82. Love to get input - particularly on if this looks like generally the right direction to go.
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