CSeq contains sequence number and the method. CSeq header in the response to
the CANCEL request shall contain the token "CANCEL".

regards

On 30/04/07, Mushtaq Ilyas <[EMAIL PROTECTED]> wrote:
>
> RFC 3261
> "While a CANCEL request is handled in a stateful proxy by its own   server
> transaction, a new response context is not created for it.   Instead, the
> proxy layer searches its existing response contexts for   the server
> transaction handling the request associated with this   CANCEL.  If a
> matching response context is found, the element MUST   immediately return a
> 200 (OK) response to the CANCEL request.  In   this case, the element is
> acting as a user agent server as defined in   Section 8.2.  Furthermore,
> the element MUST generate CANCEL requests   for all pending client
> transactions in the context as described in    Section 16.7 step 10."
>
> Yes CANCEL is a distinct transaction but with same response context as the
> INVITE it is cancelling?
> The problem however is that using thesame response context causes an
> abnormality is the state-machine.
>
> UA Client         Proxy Server
> ================================
> ---->Invite
>                          <==180
> ---->Cancel
>                          <==200
>                          ---->Cancel
>                                                 <==200 or 487 (SIP Proxy
> Server or UA Server)
>
> How would one identify that the 200 is for the Invite or Cancel?
>
>
> Regards
> Mushtaq Ilyas
>
>
> ----- Original Message ----
> From: Ryan Mitchell <[EMAIL PROTECTED]>
> To: [email protected]
> Sent: Saturday, 28 April, 2007 11:34:34 PM
> Subject: Re: [Sip-implementors] Cancel part of Invite transaction?
>
> My mistake -- CANCEL is a distinct transaction (RFC 3261 sec 9.1).  The
> cseq
> value is used to match up on the INVITE that's being cancelled.
>
> For reverse compatibility with RFC 2543, the UAS may or may not send a 487
> (request terminated) response to the cancelled INVITE.  I suspect this may
> be the source of confusion -- with only a single 200 OK response for the
> cancel you might guess there's only 1 transaction.
>
> --
> Ryan Mitchell
> Telecom Logic, LLC
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