[OpenSER-Devel] question on t_relay on CANCEL
Dan Pascu
dan at ag-projects.com
Fri Feb 8 11:36:18 CET 2008
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
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