[OpenSER-Devel] question on t_relay on CANCEL

Dan Pascu dan at ag-projects.com
Fri Feb 8 12:19:44 CET 2008


On Friday 08 February 2008, Iñaki Baz Castillo wrote:
> On Friday 08 February 2008 11:36:18 Dan Pascu wrote:
> > I've even seen devices
> > that send a CANCEL after a 200 OK, but before the ACK, as they
> > consider that the dialog is not established until confirmed by the
> > ACK. Which makes sense because is cleaner to cancel a call setup with
> > a CANCEL before it is confirmed, than to send an ACK and then a BYE
> > (for example if I do not want to accept the session because the 200
> > OK contains something I do not agree on or is badly formatted, then I
> > don't want to confirm the session with an ACK and then close it with
> > a BYE).
>
> But AFAIK sending a BYE after an ACK is the way specified in RFC 3261.
> Is it RFC compliant to send a CANCEL after a 200 OK is received? will
> most of UAS accept it and terminate the dialog?

I think I just explained that above if you read carefully. If I do not 
understand the 200 OK or do not agree with it and I don't want to send an 
ACK to confirm it, then how am I supposed to end the session?
By confirming something I do not understand or accept and then closing a 
session I do not want? I don't think so.

IMO, CANCEL is valid to be sent until the session is confirmed, and that 
doesn't happen until the ACK is sent.

-- 
Dan



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