[SIPForum-discussion] CANCEL for reinvite

[Stephen James]

1. The request is the original INVITE that you are cancelling.
2. Receiving a 200OK means you can't send CANCEL, but must send BYE as the 
INVITE transaction has completed.
3. You should wait for the provisional response before attempting to CANCEL.
Per 3261 the far end should send a 100 Trying if the reINVITE will take more 200 
ms.
 
Stephen James 
sjames_1958 at yahoo.com
 
We are not princes of the earth, we are the descendants of worms, and any 
nobility must be earned.





________________________________
From: AMIT ANAND <amiit.anand at gmail.com>
To: SIP FORUM <discussion at sipforum.org>
Sent: Tue, April 2, 2013 10:41:22 PM
Subject: [SIPForum-discussion] CANCEL for reinvite

Hi All,

>From RFC we could see that it says UAC shall not send CANCEL if it has not 
received provisional response of original request.

Once the CANCEL is constructed, the client SHOULD check whether it has  received 
any response (provisional or final) for the request being  cancelled (herein 
referred to as the "original request"). 

If no provisional response has been received, the CANCEL request  MUST NOT be 
sent; rather, the client MUST wait for the arrival of a  provisional response 
before sending the request.

Question is what does Original Request refers here? Transaction CANCEL going to 
cancel or initial request which started dialog, if transaction and not initial 
request then whats its use because CANCEL is to cancel a transaction its obvious 
its going to cancel a transaction, and  transaction has only one request? 


Do we need to wait for Provisional response for reinvite to send cancel? If yes 
what if far end does not sent any provisional response and straight sends 200OK, 
and we have cancel pending on another leg?

Thanks
Amit
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