Re: [rtcweb] SDP Offer/Answer draft-jennings-rtcweb-signaling - More-coming and final answer (Section 5.2.3)

Cullen Jennings <> Fri, 04 November 2011 15:43 UTC

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From: Cullen Jennings <>
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Date: Fri, 04 Nov 2011 08:43:58 -0700
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To: Christer Holmberg <>
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Subject: Re: [rtcweb] SDP Offer/Answer draft-jennings-rtcweb-signaling - More-coming and final answer (Section 5.2.3)
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On Nov 3, 2011, at 12:33 , Christer Holmberg wrote:

> Hi, 
>>> Q2. Are there restrictions when it comes to changing information in a non-final 
>>> answer and a final answer? Or, can the final answer be completely different from 
>>> previously sent non-final ANSWERS? In "legacy" O/A there are restrictions.
>> Any answer has to be a valid answer for the offer but other than that, no restrictions, 
>> so the final answer can change everything from an earlier one. 
> Is there a reason/use-case/requirement why we need to allow that? As far as I know, the reason behind this is ICE.

There a bunch of use cases but to mention two: In the browser to browser case, imagine that you start sending audio in the first answer but need to wait for user feedback to find out if video can be added or not in the final answer. In a browser to SIP use case, the early media for 1-800-go-fedex.


PS - Sorry for slow replies but we had the week before the -00 drafts, then the week before the -01 drafts, now I am at the W3C TPAC meeting for a week, then reading drafts weeks, then IETF so I suspect a bunch of this I won't really get to till after IETF but ….