[prev in list] [next in list] [prev in thread] [next in thread] 

List:       sip-implementors
Subject:    Re: [Sip-implementors] Call termination by UAC in state Calling
From:       "Worley, Dale R (Dale)" <dworley () avaya ! com>
Date:       2011-01-21 16:41:49
Message-ID: CD5674C3CD99574EBA7432465FC13C1B220A1767CD () DC-US1MBEX4 ! global ! avaya ! com
[Download RAW message or body]

> From: Peter Krebs [pkrebs@gmail.com]
> 
> I have a question regarding the termination of a call establishment by the
> UAC, when no response has been received for an ongoing UAC INVITE
> transaction, i. e. the transaction is still in state "Calling" and no dialog
> has been created. It seems to me, that this situation is not considered at
> all in RFC 3261 but it is simply assumed that the user who initiated the
> call has the patience to wait for termination of Timer B until a new call
> can be attempted (suppose only one call establishment is possible at the
> same time). Is there a rule(best practice for this "early call abortion" or
> is this simply a constraint for a given UI (to wait until the UAC INVITE
> transaction times out)?

As others have noted, the correct action is to put the call into a state where
any incoming 1xx responses are answered by a CANCEL, and any incoming 2xx
responses are answered by ACK followed by BYE.

Unfortunately, there are a number of situations in SIP where this sort of processing
must be done, that is, where some activity cannot be abandoned immediately,
but rather, an extended sequence of operations must be done to terminate
the state.

BTW, when dealing with tricky call-state situations, look at RFC 5407 in preference
to RFC 3261 -- it is much more detailed and clarifies many special cases.  Although
it doesn't speak to your question.

Dale


[prev in list] [next in list] [prev in thread] [next in thread]