Regarding Re-INVITE/CANCEL,
Re-INVITE is a mid-call transaction (which happens after the
dialog is setup), CANCEL for a mid-call transaction is allowed including Re-INVITES.
Other mid-call transaction can be INFO (2-way handshake) which again can be CANCEL'ed.
The reason that Re-INVITE/INVITE are 3 way handshake is because it is assumed that
they take longer time to complete (b'coz of possible human intervention).
Also Re-INVITE can be used for other purposes than session parameter change - for
example in refershing the session (Session Timer, where no SDP change happens).
-AD.
Robert Sparks <[EMAIL PROTECTED]> wrote:
On Thu, 2002-07-18 at 19:26, Ranjit Avasarala wrote:
> Hi
>
> But u use re-invite to change the session parameters of an existing call.
> So how can u send CANCEL then?
The session parameters don't change until the re-INVITE is accepted.
If the UAS hasn't sent a 200 OK (or some other final response) to
that re-INVITE before the CANCEL arrives, the reINVITE is cancelled.
The session stays just like it was - from the session's perspective
it will be as if the re-INVITE had never been sent
RjS
>
> Ranjit
> ----- Original Message -----
> From: Robert Sparks <[EMAIL PROTECTED]>
> To: Ranjit Avasarala <[EMAIL PROTECTED]>
> Cc: Suresh Arora <[EMAIL PROTECTED]>; Medhavi Bhatia
> <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> Sent: Thursday, July 18, 2002 3:12 PM
> Subject: [Sip-implementors] Re: [Sip] CANCEL FAQs
>
>
> >
> > On Thu, 2002-07-18 at 13:34, Ranjit Avasarala wrote:
> > > u cannot send CANCEL for re-invite as u won't be getting any ringing
> tone as
> > > response
> >
> > This is not correct.
> >
> > If you have received a provisional response, you can, in fact, send
> > a CANCEL to a re-INVITE. However, the nature of re-INVITE is such
> > that it is not likely to pend for long, so the chances that the CANCEL
> > won't arrive in time to affect the re-INVITE are higher than they are
> > for an initial INVITE.
> >
> >
> > >
> > > Ranjit
> > > ----- Original Message -----
> > > From: Suresh Arora <[EMAIL PROTECTED]>
> > > To: Medhavi Bhatia <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> > > Sent: Wednesday, July 17, 2002 6:14 PM
> > > Subject: RE: [Sip] CANCEL FAQs
> > >
> > >
> > > > I think UAS can send CANCEL to UAC for a re-INVITE (if requested
> session
> > > > characteristics are not supported by Server).
> >
> > As Ajit already pointed out, if the UAS doesn't like an INVITE request
> > it sends a response, not another request. CANCEL works like this:
> >
> > INVITE
> > -------->
> > CANCEL
> > -------->
> >
> > NOT like this:
> >
> > INVITE
> > -------->
> > CANCEL
> > <--------
> >
> > For the case you call out (unsupported session characteristics) the
> > UAS will return a 488 (or possibly a 606). Thus:
> >
> > INVITE
> > -------->
> > 488
> > <--------
> >
> > > >
> > > > -Suresh
> > > >
> > > > -----Original Message-----
> > > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> Medhavi
> > > > Bhatia
> > > > Sent: Wednesday, July 17, 2002 9:21 AM
> > > > To: [EMAIL PROTECTED]
> > > > Subject: Re: [Sip] CANCEL FAQs
> > > >
> > > >
> > > > This stuff generally belongs to the implementor's list:
> sip-implementors
> > > > <[EMAIL PROTECTED]>
> > > >
> > > > Generally CANCEL should not be used for transactions which are bound
> to
> > > > complete
> > > > quickly, and never for transactions for which you havent received a
> > > > provisional (1xx)
> > > > response. So the answer for (1) would be: probably not. Also the UAS
> > > cannot
> > > > cancel
> > > > a transaction started by the UAC (I guess that's what you meant), so
> it
> > > > cannot generate
> > > > the CANCEL ever.
> > > >
> > > > ----- Original Message -----
> > > > From: "Sp.Raja" <[EMAIL PROTECTED]>
> > > > To: <[EMAIL PROTECTED]>
> > > > Sent: Tuesday, July 16, 2002 6:25 AM
> > > > Subject: [Sip] CANCEL FAQs
> > > >
> > > >
> > > > > Please help me out by answering these questions.
> > > > >
> > > > > 1. Can CANCEL be used to cancel a bye ?
> > > > >
> > > > > 2. Can CANCEL be send by the called entity (UAS) ? If yes then under
> > > what
> > > > > circumstances
> >
> > The answers above probably address what you meant, but to be
> > complete:
> >
> > The "called entity" plays the role of a UAS for the transaction
> > processing the INVITE it received. It cannot CANCEL that transaction,
> > it can only send responses in it.
> >
> > If that INVITE is accepted, the called entity can later send
> > its own requests (such as (re-)INVITE). It is playing the roal
> > of a UAC for those request transactions, and once it recieves
> > a provisional response, it can send CANCELs.
> >
> > RjS
> > > > >
> > > > > - Sp.Raja
> > > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> > > > This list is for NEW development of the core SIP Protocol
> > > > Use [EMAIL PROTECTED] for questions on current sip
> > > > Use [EMAIL PROTECTED] for new developments on the application of sip
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> > > > This list is for NEW development of the core SIP Protocol
> > > > Use [EMAIL PROTECTED] for questions on current sip
> > > > Use [EMAIL PROTECTED] for new developments on the application of sip
> > >
> > >
> > > _______________________________________________
> > > Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
> > > This list is for NEW development of the core SIP Protocol
> > > Use [EMAIL PROTECTED] for questions on current sip
> > > Use [EMAIL PROTECTED] for new developments on the application of sip
> >
> >
> > _______________________________________________
> > Sip-implementors mailing list
> > [EMAIL PROTECTED]
> > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
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