[SIPForum-discussion] : Invite Cancel Response sequence

[David Benoit]

Hi,

This seems perfect to me.  Consider RFC 3261 9.2 para 4.{5,6}-5.1:

   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.

   Regardless of the method of the original request, as long as the CANCEL
   matched an existing transaction, the UAS answers the CANCEL request itself
   with a 200 (OK) response.

So, it seems like your UAS is processing properly.  Note, however, that even
if the UAS is responding properly, the responses (the 487 to the INVITE and
the 200 for the CANCEL) can arrive in the opposite order.  The UAC has to be
prepared to deal with that.

David

On Wed, Oct 07, 2009 at 07:40:35PM +0900, chethan prakash 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
> 
> 
> !DSPAM:4acd25c4322701802513419!

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