[OpenSER-Devel] question on t_relay on CANCEL

[Dan Pascu]

On Friday 08 February 2008, Juha Heinanen wrote:
> also, i haven't found in rfc 3261 a clear statement if CANCEL sent
> after 180, for example, is considered an in-dialog request or an
> initial request.  at that point the dialog has been established
> already.

Not necessarily. You may have parallel forking and get multiple 180. Until 
you get a 200 OK, no dialog is really established. 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).

-- 
Dan