Step 2 is inconsistent with the RFC. The UAC MUST wait for a 100 trying
before sending a CANCEL.

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Chacoo
Sent: Monday, January 08, 2007 4:55 PM
To: [email protected]
Subject: [Sip-implementors] Question on CANCEL

Hi
I have some question on following scenario.
1. Alice send INVITE to Bob.
2. Before receiving any message, Alice terminated the call. In the other
word, it send CANCEL to Bob.


3. Because of using UDP or some other reasons, Bob receives CANCEL before
INVITE.
4. Bob send 481 for CANCEL, and then process INVITE, 180 or 200 will be
sent.
5. Alice receive 481, then cease retransmission of CANCEL. After that Alice
receive 180 or 200.

Q1. Now what should be taken to inform Bob to cease the retransmission, or
just let it be?

Q2. The other reason in 3 may be that the retransmission of INVITE cannot
ceased by sending CANCEL. So can the INVITE transaction be ceased by sending
CANCEL?
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