Re: [rtcweb] Clarification on offer/answer in jsep-01

> The next sentence just after this one
> " The answerer can send back zero or more
>    provisional answers, and finally end the offer-answer exchange by
>    sending a final answer."
> does not describe quite well either, right?
>
> AFAIK , the answerer can send back zero or more provisional answers, but they are not all SDP answers,

If we look the Section 12.1.1 of RFC5245 (ICE),

  "If an offer is received in an INVITE request, the answerer SHOULD
   begin to gather its candidates on receipt of the offer and then
   generate an answer in a provisional response once it has completed
   that process.  ICE requires that a provisional response with an SDP
   be transmitted reliably.  This can be done through the existing
   Provisional Response Acknowledgment (PRACK) mechanism [RFC3262] or
   through an optimization that is specific to ICE ..."

Here provisional response carriers answer, but the offer/answer
exchange is completed. Offerer can send PRACK with SDP to updates the
offer, and the answerer replies answer in 200 of PRACK, but this is a
new round of offer/answer exchange.

Also from the RFC 6337 (Session Initiation Protocol (SIP) Usage of the
Offer/Answer Model
), we can't find the case where the answerer sends multiple different
answers for one offer.

So it seems that we also need clarification on the following,

"The answerer can send back zero or more provisional answers, and
finally end the offer-answer exchange by
  sending a final answer."

/Kaiduan

On Tue, Aug 28, 2012 at 10:50 PM, Lishitao <lishitao@huawei.com> wrote:
>
>
>> -----Original Message-----
>> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On Behalf
>> Of Cullen Jennings
>> Sent: Tuesday, August 28, 2012 8:58 PM
>> To: Francois Audet
>> Cc: rtcweb@ietf.org
>> Subject: Re: [rtcweb] Clarification on offer/answer in jsep-01
>>
>>
>> On Aug 27, 2012, at 10:48 PM, Francois Audet <francois.audet@skype.net>
>> wrote:
>>
>> >> "As in [RFC3264], an offerer can send an offer, and update it as long
>> >> as it has not been answered."
>>
>> yah that won't work or all the reasons mentioned before and in my opinion does
>> not represent the WG consensus. BTW - that was added in the -01 version of
>> the draft and submitted without me ever seeing it - I'd be happy to fix it but I
>> don't have the source for the draft. Chairs?
>>
>
> The next sentence just after this one
> " The answerer can send back zero or more
>    provisional answers, and finally end the offer-answer exchange by
>    sending a final answer."
> does not describe quite well either, right?
>
> AFAIK , the answerer can send back zero or more provisional answers, but they are not all SDP answers,
>
> and I don't find any place in RFC 3264 has the definition about "final answer".
>
> shitao
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