Ok, I got it.
Thanks for your support.

Thanks and Regards,
Amith

-----Original Message-----
From: Brett Tate [mailto:br...@broadsoft.com] 
Sent: Tuesday, July 05, 2011 5:05 PM
To: Amith R R; Sip-implementors@lists.cs.columbia.edu
Subject: RE: [Sip-implementors] Regarding Subscription Termination

> As per the below description, AS has to send NOTIFY 
> and Core network has to reject it in order to cancel 
> the subscription. 

Those are not the only ways to terminate the subscription.  

If the NOTIFY is to terminate the subscription, the transferor does not have
to reject the NOTIFY.  

If the NOTIFY is not to terminate the subscription, the transferor can 1)
reject the NOTIFY or 2) send a re-SUBSCRIBE to terminate the subscription.
Number 2 appears to be preferred by RFC 3515; although it does indicate the
potential for number 1.

RFC 4488 also provides a mechanism to avoid sending/receiving a useless
NOTIFY.

> If AS sends a BYE Message directly without NOTIFY, 
> whether subscription will be deleted? If No, How long 
> the subscription in Core Network will be active?

Draft-ietf-sipcore-rfc3265bis-02 defined Timer N for use when awaiting the
expected NOTIFY.  Timer N defaults to 64*T1.  However if the transferor
plans to reject the NOTIFY, the transferor typically does not need to really
maintain subscription state (especially after the call dialog usage has been
released) unless using such knowledge to produce a better NOTIFY response.

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