Hi,

Regarding a subscription with a zero expiration (out of a dialog, else 
it's an unsubscription), it is considered polling the resource, you 
should get in return a notification with a subscription state terminated 
and with the event information in the body.

I insist on should, because when tested with different phone brands you 
always get a notification but unfortunately one doesn't include a body. 
(so you don't get the information required)

Since the one is a Polycom which is popular among sipXecs users, I 
suspect this is why sipXecs uses an expiration of 1 to make it work.

Unfortunately other brands don't like a small expiration time of 1 and 
rejects it. (to protect against too many/quick refresh, exactly like 
registration does reject too small expiration)

In fact to make it work with every phones the best would be to use no 
expiration time (to let the phone decide) and unsubscribe after the 
first notification.

This would work with every phones as long as they support RFC4235 
subscription of course.

Now regarding looking at the consolidated RLS to find the information to 
   avoid that subscription, it would indeed require that such a list 
exists and has been set up (through speed dials) at the sipXecs server, 
but it worth the shot checking it before launching that costly subscription.

I'm pretty confident that such RLS will exist with many installation to 
provide (and centralize) extension monitoring to different phones.

Regards.

----
Do we have consensus among the experts that an expiration value of zero 
is the right thing?


Also, does the RLS server establish a subscription to all the phones in 
the system automatically or only to the ones for which a user requested
monitoring?  I.e. for VOP do you manually create a resource list that
includes all the phones a receptionist might want to monitor or is that
already there?
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