[SIPForum-discussion] CANCEL with reliable response ...

[AMIT ANAND]

Hi,

For B it is fine to respond with 200OK for PRACK , as it seems to be a race
condition between PRACK and 487. But this Behavior of A is wrong it should
not send PRACK after sending CANCEL. It does not make any sense to send
PRACK after sending a request to cancel.
Although RFC does not mandates it but it says that UAC should wait for
provisional response to send Cancel. So ideally A should have sent PRACK
first then should Initiate CANCEL.

Cheers
Amit

On Thu, Jun 3, 2010 at 10:55 AM, Sumeetkumar Bhardwaj <
sumeet_bhardwaj at persistent.co.in> wrote:

>  Hello Murali,
>
>
>
> I think, If it gets the PRACK before terminating the call, it should
> respond to the 200 OK for that PRACK, but if it gets the PRACK after
> terminating the call, it should respond with the error “481 call leg
> /transaction does not exists”. So, it just a matter of arrival of PRACK
> before and after terminating the call. So, I think, PRACK means provisional
> response reliability, and if B got request to CANCEL the call, it has to
> CANCEL that INVITE transaction irrespective of reliability.
>
>
>
>
>
> Thanks,
>
> Sumeet
>
> * *
>
>
>
> *From:* discussion-bounces at sipforum.org [mailto:
> discussion-bounces at sipforum.org] *On Behalf Of *Murali Vuppandla
> *Sent:* Wednesday, June 02, 2010 6:33 PM
> *To:* discussion at sipforum.org
> *Subject:* [SIPForum-discussion] CANCEL with reliable response ...
>
>
>
> There are two SIP nodes A and B. A sends an INVITE with 100rel tag in
> Supported header. B sends 180 reliably with 100rel in Require header. A
> would like to CANCEL the call at this particular point of time.
>
>
>
> What should be the actual behavior of B now … Should it go-ahead and
> terminate the call immediately by responding to CANCEL or should it wait for
> PRACK and then terminate the call ??
>
>
>
> Here is the call flow observed in my lab.
>
>
>
> A                                        B
>
>         INVITE
>
>      ----------------------------------->
>
>         180 Ringing(reliable)
>
>     <------------------------------------
>
>          CANCEL
>
>    -------------------------------------->
>
>           200OK
>
>    <----------------------------------------
>
>             PRACK
>
>    ------------------------------------------>
>
>              200OK
>
>    <------------------------------------------
>
>               487
>
>    ß---------------------------------------
>
>                  ACK
>
>     ---------------------------------------à
>
>
>
> Please clarify me the  behaviour of B in this scenario.
>
>
>
> Regards,
>
> Murali.
>
>
>
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-- 
Thanks
Amit Anand
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