________________________________________
From: [email protected] 
[[email protected]] On Behalf Of SungWoo Lee 
[[email protected]]

Could any body let me know when REFER subscription should be terminated at 
REFER sender UA?
When transfering, a SIP UA sends REFER request and an implicit subscription is 
created at the SIP UA. My question is whehter it has to receive NOTIFY request 
which explicitly specify the subscription-state as 'terminated' in order to 
terminate the subscription.
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The rules are in RFC 3265, which will be updated by 
draft-ietf-sipcore-rfc3265bis-02.  The draft clarifies that a subscription is 
terminated only when a NOTIFY is received with subscription-state 'terminated', 
and the notifier is responsible for sending such a NOTIFY.  Of course, the 
subscriber can always force such a NOTIFY to be sent by sending a SUBSCRIBE 
with "Expires:0".  Also, if the current time is significantly after the 
established termination time of the subscription, even if the subscriber has 
not received a NOTIFY with subscription-state 'terminated', it can assume the 
subscription has been terminated.

If the question is, "May the notifier omit sending the terminating NOTIFY?", 
the answer is, "No."  See draft-ietf-sipcore-rfc3265bis-02 section 4.2.1.4:

   If no refresh for a notification address is received before its
   expiration time, the subscription [record at the notifier] is removed.  When 
removing a
   subscription, the notifier SHOULD send a NOTIFY message with a
   "Subscription-State" value of "terminated" to inform it that the
   subscription is being removed.  If such a message is sent, the
   "Subscription-State" header field SHOULD contain a "reason=timeout"
   parameter.

Dale

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