[SIPForum-discussion] Why CANCEL cannot be in Same trasaction like ACK for Non 2xx response

[Gottfried, Hal F]

I believe that he was speaking of this section ::

   The layer above the transaction layer is called the transaction user
   (TU).  Each of the SIP entities, except the stateless proxy, is a
   transaction user.  When a TU wishes to send a request, it creates a
   client transaction instance and passes it the request along with the
   destination IP address, port, and transport to which to send the
   request.  A TU that creates a client transaction can also cancel it.
   When a client cancels a transaction, it requests that the server stop
   further processing, revert to the state that existed before the
   transaction was initiated, and generate a specific error response to
   that transaction.  This is done with a CANCEL request, which
   constitutes its own transaction, but references the transaction to be
   cancelled (Section 9).




Hal


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Abhisek Acharya
Sent: Friday, January 11, 2013 2:09 AM
To: Vijay Kumar
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Why CANCEL cannot be in Same trasaction like ACK for Non 2xx response

Vijay,

We identify transactions from branch-ids and CANCEL also has the same branch id as INVITE ...So theoretically it should be part of the INVITE transactions.
Please correct me if I am wrong.Also i want to see the segment where it says that CANCEL is a different transaction in RFC 3261.Please let me know the excat segment.

Abhisek Acharya

On Thu, Jan 10, 2013 at 11:51 PM, Vijay Kumar <vj.tech776 at gmail.com<mailto:vj.tech776 at gmail.com>> wrote:
Hi all
Can any one throw light on this please.

Agreed that as per 3261 INVITE and ACK for 2xx response are in different transaction
Agreed that ACK for NON 2xx response and INVITE are in same transaction

Same Via branch as INVITE,Same Cseq(Only Numeric part Cseq=1 ACK)  in ACK for NON 2xx response .(Hence ACK is for Non 2xx reponse if in same transaction as of INVITE)

BUT
Why not CANCEL be in same transaction as INVITE because of
Same Via branch,Same Cseq(Only Numeric part like Cseq= 1 CANCEL)

(Agreed RFC 3261 says CANCEL and INVITE are different transactions)
Thanks in advance
Vijay

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