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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