I think, we will send CANCEL/BYE in the Refer-to header only to Terminate
other dialogs. If we have to Terminate the REFER dialog itself we don't have
to send it using another REFER Message. BYE is a Dialog Terminator so we can
send a BYE for the REFER Dialog. Like BYE, CANCEL is a transaction
Terminator.
Here is snipet from RFC3261 Section 5 about CANCEL
"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)."
AND from Section 9.
"The CANCEL request, as the name implies, is used to cancel a previous
request sent by a client. Specifically, it asks the UAS to cease processing
the request and to generate an error response to that request."
Here is the call flow in my mind.
3PCC
ALICE BOB
-----------
----------- -----------
|
| |
|------------REFER----------------------------------->|
|
|<-------------------202
---------------------------------|
|
|
| |
|
|------------INVITE------------------------>|
|-------------BYE(for REFER
Dialog)----------->| |
|
|------------CANCEL--------------------->|
|<-----------200 OK------------------------------------|<------------200
OK ----------------------|
|
| |
|
|<----------487-------------------------------|
|
| |
Likewise in Section 15 RFC talks about Termination of Session/Dialog which
is done by using BYE.
I read the RFC and it does not explicitly address this issue. The other
option is that REFER creates an implicit Subscription and we could terminate
the subscription which would cause and end of the dialog too. The only issue
with this solution is that we will have to deal with the transaction not
being terminated when the subscription is terminated.
Call flow using subscription to
3pCC Alice
--------- --------------
| |
|--------(OOD) REFER--------->|
| |
|----Subscribe(Expire=0)----->|
| |
|<----------200 OK-----------------|
|<----------487(REFER)----------|
Thanks
Ramesh
On 1/4/07, Sanjay Sinha (sanjsinh) <[EMAIL PROTECTED]> wrote:
>
> You can not send a CANCEL to cancel REFER. You can send another REFER
> with method CANCEL/BYE in Refer-To header to terminate the dialog
> created as a result of initial REFER. That also needs you to know the
> dialog identifiers of that dialog that you want to cancel or bye. You
> can get that by subscribing to "dialog" event package.
>
> Pl. see this: draft-mahy-sip-remote-cc-04.txt
>
> Sanjay
>
>
> >-----Original Message-----
> >From: [EMAIL PROTECTED]
> >[mailto:[EMAIL PROTECTED] On Behalf Of Ramesh
> >Sent: Thursday, January 04, 2007 6:28 PM
> >To: [email protected]
> >Subject: [Sip-implementors] OOD REFER Dialog Termination
> >
> >Hi,
> > Here is another question I have with regard to Usage of
> >REFER in 3pcc. If we have started a OOD-REFER and wish to
> >CANCEL the dialog; ie the originator of the dialog wishes the
> >cancel the Dialog. Can I send a CANCEL message if we have not
> >received a confirmation 2xx message and a BYE message if we
> >have received a dialog Confirmation. I haven't seen anything
> >in the RFC the explicitly forbids me from doing it.
> >
> >
> >--
> >cheers
> >ramesh
> >_______________________________________________
> >Sip-implementors mailing list
> >[email protected]
> >https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
> >
>
--
cheers
ramesh
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