Subject: RE: [Simple] Migration and client PA as a definitive authority.

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 2 Oct 2001 11:01:13 -0400

-----Original Message-----
From: Robert Brown [mailto:[email-masked]]
Sent: Saturday, September 29, 2001 9:12 PM
To: Brian Stucker; simple
Subject: RE: [Simple] Migration and client PA as a definitive authority.

>Actually, I think REGISTER is only meant to be an example of one way an
implementer might 
>want to publish presence to the PA.  You've hit on one of the examples of
why this isn't 
>a great idea (and I agree).  A few other reasons I don't like using
REGISTER to publish 
>presence:

REGISTER is not a good way to publish general presence docs, I agree.
However, its an excellent INPUT to the PA process of generating a presence
doc, since it naturally conveys information about a user. A registration
tells the server whether the user is connected to receive invitations to
sessions, and that is presence data.

> 1) REGISTER is something you'll want to send pretty frequently unless you
have 
>a very stable and static network, but you only need to send new presence
status when you 
>actually have some new state; 2) there are only so many ways you can
overload REGISTER 
>and complicate its semantics - it's better IMHO just to invent a different
method or do 
>something out of band; or do something tricky like have the PA subscribe to
the PUA; 3) 
>why should I be registered in order to publish presence?

All of these are good reasons why REGISTER is not the right way for a client
to push presence specific data to a server. Its for that reason that Steve
Donovan wrote up some requirements on a more appropriate publication
protocol:

http://www.ietf.org/internet-drafts/draft-donovan-publish-requirements-00.tx
t

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

---

From: Paul Kyzivat <[email-masked]>
Date: Tue, 02 Oct 2001 11:31:41 -0400

I agree with Jonathan that REGISTER is a good way to convey information
that can be used to create a presence document, but perhaps is not a
good way to transmit a presence document.

But I will go further - I don't see the advantage in any kind of
presence document other than the one that can be created from
registration information. If you create a presence document some other
way, then it runs the risk of being inconsistent with registrations.
This will simply lead to surprises when a presence client takes action
based on the presence document.

Of course the presence document can carry nuances to presence that
aren't available from registrations, but most of those probably indicate
limitations in the registration mechanism. Most of the nuances that I
imagine could be useful can be expressed using callerprefs. What is
needed is an agreement on how that information will be represented in
the presence document.

If PUAs have some added nuance to state about their presence, I think it
would be better to convey a document in their REGISTER message that is
incorporated (in a well defined way) as an extra section in the presence
document that the registrar syntasizes. 

	Paul Kyzivat

Jonathan Rosenberg wrote:
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