[SIPForum-discussion] : Invite Cancel Response sequence

[Venkata Ramesh B]

Hi Chethan,

RFC 3261. Section 9.2

   If the UAS did not find a matching transaction for the CANCEL
   according to the procedure above, it SHOULD respond to the CANCEL
   with a 481 (Call Leg/Transaction Does Not Exist).  If the transaction
   for the original request still exists, the behavior of the UAS on
   receiving a CANCEL request depends on whether it has already sent a
   final response for the original request.  If it has, the CANCEL
   request has no effect on the processing of the original request, no
   effect on any session state, and no effect on the responses generated
   for the original request.  If the UAS has not issued a final response
   for the original request, its behavior depends on the method of the
   original request.  If the original request was an INVITE, the UAS
   SHOULD immediately respond to the INVITE with a 487 (Request
   Terminated).  A CANCEL request has no impact on the processing of
   transactions with any other method defined in this specification.


Best Regards,
Ramesh.


On Wed, Oct 7, 2009 at 6:40 PM, chethan prakash <chethan.ps at gmail.com>wrote:

> Hello All,
>
> Can you please kindly clarify if there is anything wrong the below
> mentioned INVITE Cancel Response Sequence,
>
> UE 1                                    UE 2
>     --------------INVITE----------------->
>     <---------- 100 Trying---------------
>     <---------- 180 Ringing-------------
>     -------------CANCEL---------------->
> *    <---------- 487 (INVITE)------------*
> *    <---------- 200 OK (CANCEL)----*
>
> Please forward me the RFC Section where it is stated that on receiving
> cancel we should respond to Cancel Request first before we send final
> response to Invite Request.
>
>
> Regards,
> Chethan
>
>
>
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