Subject: Re: [Simple] watcher info problem in PA/Proxy/Registrar model

From: "Li Hua Tang" <[email-masked]>
Date: Tue, 5 Mar 2002 09:51:25 +0800

Jonathan Rosenberg wrote:

>The PS wouldn't terminate the subscriptions for watcher information; it
>would proxy them, just as it did the original presence information. The
>server that handles the subscriptions for some package foo needs to
>handle foo.winfo. This is much clearer in the next rev of the
>specification.

Then who can terminate the subscriptions for watcher information? Let us
detail two cases. These two cases have been described in
draft-ietf-simple-winfo-format-01.

One is a user, A, subscribes to the presence of another user, B. A would
like to find out about the status of their subscription. If no PS, the
subscriptions for watcher information is sent directly to B and it's easy
to do handle it. If there is a PS existing between A and B, my first
question is what will the To header be in SUBSCRIBE request? If it's a
registered SIP address and the request may be forked, another question
comes out. There is no clear definition in winfo-package-00 about how to
handle this forked SUBSCRIBE requests. If the request is proxying and not
forked, B will terminate this subscription.

The other case is a user B, wishes to learn the set of people who have
subscribed to B's presence. What is the To header of this SUBSCRIBE
request? More, if the PS can't terminate this subscription, are they the
set of watchers who return their watcher information to B independently?
It's difficult to understand this way.

Best regards,

Tang Lihua
Email:  [email-masked]

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 04 Mar 2002 20:57:00 -0500

Li Hua Tang wrote:
> Then who can terminate the subscriptions for watcher information?

Whatever element is terminating the presence subscriptions.

> Let us
> question is what will the To header be in SUBSCRIBE request?

Same as it was for the SUBSCRIBE for presence state.

> If it's a

winfo-package-01 talks about this case. It recommends that the
watcherinfo subscription be sent on the same dialog as the presence
subscription. THis guarantees that the same server handling presence, is
also handling watcherinfo.

> request?

Same as it was for the presence subscription.

> More, if the PS can't terminate this subscription, are they the

There are two solutions for this case. Both are docuented in -01. In the
first case, the PS will fork the watcherinfo subscription, and the
result is that multiple subscriptions are installed. In the second case,
the PS can direct the watcherinfo subscription to a server that the
network has explicitly designated as the winfo server, and it knows
about all watchers. 

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
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