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

[ayyanar.kalimuthu at wipro.com]

That depends on your implementation, 
 
1. if you are already in state CANCEL after receiving 180 ringing then there is no use of sending PRACK as the call is to be terminated.
 
2. If you have received 180 ringing and the construction of PRACK is already in progress, now if the call is cancelled, then PRACK can be sent first and then send CANCEL request when PRACK transaction gets completed.
 
Im not sure if this makes sense, let some experts comment on this.
 
Regards,
Ayyanar

________________________________

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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