To be charitable, we should assume that the UAC is trying to do the
right thing. So presumably it *sent* the PRACK (which was then lost or
delayed), and then sent the UPDATE without awaiting the reply to the prack.
The UAS can infer from the UPDATE with offer that the 183 was received,
and that the PRACK could not have contained an offer. So I think it is
justified in "being liberal" and responding to the UPDATE as if things
were fine. The fact that the UAC didn't wait for the response to the
prack, and yet is upset with receiving the response to the UPDATE before
the response to the PRACK is then presumably its problem.
An alternative approach that the UAS could take to this case is to
simply ignore (lose) the UPDATE. That will cause it to be retransmitted.
In the meantime the PRACK will hopefully show up.
Thanks,
Paul
vijaya yadav wrote:
> Hi Kinnu,
>
> Yes, UAC is at fault here but in this case what should do UAS if PRACK is
> droped on network or not send from UAC and UAS receive the Update message
> with SDP.
>
> Regards
> VYADAV
>
> On Thu, Dec 3, 2009 at 12:52 PM, Kanta C <sip_on_...@yahoo.com> wrote:
>
>> I think the UAC is at fault here. It should have responded with a PRACK for
>> the 183 and then 200 OK for UPDATE.
>>
>>
>> Regards,
>> Kinnu
>>
>>
>> ------------------------------
>> *From:* vijaya yadav <vijaya.m...@gmail.com>
>> *To:* sip-implementors@lists.cs.columbia.edu
>> *Sent:* Thu, December 3, 2009 12:30:00 PM
>> *Subject:* [Sip-implementors] UPDATE recieve with SDP without completeing
>> provisional response.
>>
>> Hi
>>
>>
>>
>> <----- INVITE (SDP)
>>
>> ------>183(SDP) (100rel)
>>
>> PRACK not received from the UAC
>>
>> <-----UPDATE(SDP)
>>
>> ------>200OK(SDP) [Is this correct message or UAS send any 4xx message]
>>
>> ------>183 retransmitted
>>
>> ----->500 Internal server error
>>
>>
>>
>>
>>
>> What is the behaviour of UAS if not recievd the PRACK of 183 and recieve a
>> UPDATE message with new offer
>>
>>
>>
>>
>> ~Vijaya
>> _______________________________________________
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>> Sip-implementors@lists.cs.columbia.edu
>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>>
>>
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