> -----Original Message-----
> From: A Venkatraman [mailto:[EMAIL PROTECTED]]
> Sent: Friday, July 27, 2001 7:42 PM
> To: [EMAIL PROTECTED]
> Subject: [Sip-implementors] CANCEL Questions on To Tag
>
> I have the following questions on CANCEL issued by a UAC (not a proxy
client)
>
> 1. If the UAC has received a provisional response with a TO
tag,
>should it use the tag in the TO of the CANCEL?
> This is what bis-04 has to say on this, in section 5.2 -
>
> The Request-URI, topmost Via, Call-ID, To, the numeric part
of CSeq
> and From header fields in the CANCEL request are identical to those
> in the original request being cancelled, including tags. This allows
> a CANCEL request to be matched with the request it cancels.
>
> The plural tags implies "FROM and TO tags", but the original request
may
>not have had a TO tag, if it is the request initiating the session.
Everything in the CANCEL matches the INVITE. If there were no tags in the
INVITE, there are none in the CANCEL. That is the intent of the above.
>
> 2. If the UAC has received provisional responses from
multiple
>UASes due to proxy forking, and then received a final response from one of
>them, can it send a CANCEL followed by BYE to each of the other call legs?
CANCEL is tag-less and thus cancels everything which has not generated a
final response. BYE is ideally "targeted" in the sense that it has the tags
for the specific call leg being hung up. So, I think it makes sense to be
able to BYE a call leg which has generated a provisional response with
tags/record-routes.
> The SIP spec specifies that a proxy SHOULD (not MUST) CANCEL
other
>branches if a 2xx or 6xx response is received. So, it is up to the UA to
>CANCEL other branches and reclaim its own resources associated with other
call
>legs since the other branches may have the phones ringing for a long while.
The point of the SHOULD is that the UA really isn't the one ideally suited
to do that. If the proxy forked, it really ought to be its job to reclaim
them. SHOULD is not an invitation to ignore something, its a statement that
the protocol will still function if you don't follow it, but you need a
really good reason not to.
>
> 3. If the UAC sends a CANCEL to the proxy with a TO
tag, what is
>the mandated behavior of the proxy? Is it to CANCEL just the branch which
is
>associated with that call leg?
If the request didn't contain a tag, the CANCEL doesn't contain a tag.
CANCELs cannot be directed towards specific call legs.
-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.jdrosen.net PHONE: (973) 952-5000
http://www.dynamicsoft.com
_______________________________________________
Sip-implementors mailing list
[EMAIL PROTECTED]
http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
