Thanks & Regards,
Nataraju A.B.
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Brett
Tate
Sent: Wednesday, February 25, 2004 10:57 PM
To: [EMAIL PROTECTED]
Subject: RE: [Sip-implementors] doubt in CANCEL/BYE operation
> I have one doubt in CANCEL/BYE operation.
> The scenario is as follows :-
>
> A B
> | |
> | INVITE |
> |-------------->|
> | 180 Ringing |
> |<--------------|
> | |
>
> User A invites user B. Now B responds with
> 180 Ringing with to tag and hence establishes
> early dialog. Now user A has decides that he
> does not want to continue the call. Hence he
> decides to terminate the dialog. Now according
> to my opinion, there are two possible ways to
> do so :-
>
> 1. A sends CANCEL to B. Then if B responds
> with 2xx response to INVITE, then A terminates
> the dialog by sending BYE. Else if B responds
> with non-2xx code, then dialog will be
> terminated and user A need to do any thing
> more other than sending ACK.
>
> 2. A sends BYE to B (BYE can be sent as early
> dialog is already established). B checks if
> he has sent final response to INVITE. If so
> he just reponds with 200 OK for BYE. Else if
> B has not yet sent final response for INVITE,
> then B sends a non-2xx error code for INVITE
> as soon as it sees BYE and then responds with
> 200 for BYE.
>
> I feel that option 2 is better to terminate
> dialog as it requires 2 messages less than
> the option 1.
>
> What is the procedure normally followed in the
> above scenario :- Option 1 or Option 2 ?
Option 1 should always be followed. During forking
situations, option 2 only releases individual
dialogs (call-legs) instead of communicating to
a proxy to try releasing all the associated
dialogs.
[ABN] This might be a glare situation which might happen because of
crossover (between 2xx-INV and CANCEL) in the network.
If A receives 2xx-INVITE after CANCEL sent out then it can expect
failure response (request terminated) to CANCEL request then A has to
initiate a BYE to terminate the call. But definitely A can't initiate
BYE before a final response for INVITE been received.
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