Hi,
Ideally both should have same answer. If different then UAC should
consider first offer received as answer.
Refer 3261 :
If the initial offer is in an INVITE, the answer MUST be in a
reliable non-failure message from UAS back to UAC which is
correlated to that INVITE. For this specification, that is
only the final 2xx response to that INVITE. That same exact
answer MAY also be placed in any provisional responses sent
prior to the answer. The UAC MUST treat the first session
description it receives as the answer, and MUST ignore any
session descriptions in subsequent responses to the initial
INVITE.
Thanks and Regards,
Vivek Talwar
On Fri, Jul 27, 2012 at 4:58 PM, <kumar.ramad...@wipro.com> wrote:
> I hope this holds good, even if there is change of offer/answer in between
> (18X reliable & 200 ok). My doubt is that, the UAS can still send the same
> session description in 200 ok (of Invite) as in 18x (reliable).
> This session description could be different from what was exchanged
> previously using PRACK/UPDATE. Or there should not be any session
> description at all in 200 ok (of Invite) in this case? Or if present, the
> UAC should ignore it?
>
> Thanks,
> kumar
>
>
> From: Vivek Talwar [mailto:vivek.tal...@globallogic.com]
> Sent: Friday, July 27, 2012 4:51 PM
> To: Kumar Ramadoss (WT01 - GMT-Telecom Equipment)
> Cc: sip-implementors@lists.cs.columbia.edu
> Subject: Re: [Sip-implementors] Offer/Answer model query
>
>
> Hi Kumar,
>
>
> Yes you are correct. The UAS can not initiate subsequent offer if it
> has already sent or received answer of offer in initial transaction.
> Reference Refer RFC 3261:
>
> Once the UAS has sent or received an answer to the initial
>
>
>
>
>
> offer, it MUST NOT generate subsequent offers in any responses
>
> to the initial INVITE. This means that a UAS based on this
>
> specification alone can never generate subsequent offers until
>
>
>
>
>
> completion of the initial transaction.
> Thanks and Regards,
> Vivek Talwar
>
> On Fri, Jul 27, 2012 at 4:41 PM, <kumar.ramad...@wipro.com<mailto:
> kumar.ramad...@wipro.com>> wrote:
> Hi *,
>
> Whether below mentioned scenarios correct from Offer/Answer model point of
> view ?
>
>
> 1. INVITE/18x (Reliable) for Offer/Answer1.
>
> 200 OK (INVITE)/ACK for Offer/Answer2.
>
> 2. INVITE/18x (Reliable) for Offer/Answer1.
>
> PRACK/200 OK (PRACK) for Offer/Answer2.
> 200 OK (INVITE)/ACK for Offer/Answer3.
>
> 3. INVITE/18x (Reliable) for Offer/Answer1.
>
> UDPATE/200 OK (UPDATE) for Offer/Answer2.
>
> 200 OK (INVITE)/ACK for Offer/Answer3.
>
> 4. INVITE/18x (Reliable) for Offer/Answer1.
>
> PRACK/200 OK (PRACK) for Offer/Answer2.
>
> UDPATE/200 OK (UPDATE) for Offer/Answer3.
>
> 200 OK (INVITE)/ACK for Offer/Answer4.
>
> My doubt is mainly for the case, where Offer is received in 200 OK (of
> INVITE) (later Answer in ACK), as already the offer/answer exchange has
> happened for that SIP transaction via INVITE/18x(reliable).
> I have read somewhere, that there should be only one offer/answer exchange
> for a SIP transaction.
> Please clarify.
>
> Thanks,
> kumar
>
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