________________________________________
From: [email protected] 
[[email protected]] On Behalf Of Jean-Hugues Royer 
[[email protected]]

When a resource (extension) is restarted, the RLS re-subscribe to the
extension which is good, but instead of replacing its dead subscription
(due to the restart) it stills provides both subscriptions notifications
(the old/dead one and the new one) as two different instances (both
active) for the same resources.

The old/dead instance having the higher version number, the new one is
being ignored.

To overcome this problem the RLS server should only provide one
instance/notification per resource.
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The situation is harder to to deal with than that.  The underlying problem is 
that if a phone restarts (and does not terminate its registration(s) or 
subscription(s) in the process), it is impossible for sipXecs to tell that it 
is the same phone as before, rather than a different phone registering to the 
same user-name.  So until the old registration/subscription times out, there 
will appear to be two "instances" of the resource, each with its own state.  
(The state of the old, "ghost", instance will not change, of course.)

Better-quality phones reduce this problem by terminating their subscriptions 
and registrations when they reboot in a controlled manner.

If the RLS were to provide only one instance per resource, it would be unable 
to report the status of two different phones with appearances of the same 
extension.

However, the RLS should be faithfully reporting the status of the new phone 
registration and the "ghost" registration separately; if it is not, there is a 
bug (please provide a snapshot showing the failure).

We have been considering a heuristic to reduce this problem:  When a new 
registration is seen for a user, the RLS will force resubscriptions for all the 
subscriptions that go to instances of that user.  A "ghost" registration will 
not accept the resubscription, indeed in most cases will respond with a 481, 
which will cause the RLS to delete the saved state of the ghost registration 
much faster than it would otherwise.

Dale
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