Subject: [Simple] Hand over of subscriptions handling from server to PUA

From: Nicolas Dramais <[email-masked]>
Date: Tue, 06 Feb 2001 10:37:58 +0100

Just a question for my good understanding of the
draft-rosenberg-impp-presence-00.txt :
imagine the following scenario:
1)Principal A registers and uploads to his/her proxy/presence server a
list of pre-granted watchers to his/her presentity's presence service.
2)A's registration expires. (A went off-line).
3)Principal B sends a SUBSCRIBE to sip:[email-masked]
proxyA knows that A is not currently registered and decides to act as
A's Presence Agent.
proxyA checks the list of pre-granted watchers for A and finds in it B's
sip uri.
B's subscription request is directly accepted by the server in the name
of A and a subscription is instantiated at server level for a duration
specified in the header field of the 200 OK response sent by the server
to B.
4)Principal C sends a SUBSCRIBE to sip:[email-masked]
proxyA knows that A is not currently registered and decides to act as
A's Presence Agent.
proxyA checks the list of pre-granted watchers for A but doesn't find
C's sip uri.
C's subscription request is temporarily accepted (202 OK) and the
subscription request is stored at server level as 'pending
authorization' to be submitted (with a QAUTH method) to Principal A's
approval as soon as A becomes available.
5)Principal A registers again and is available for communications. Via
his/her REGISTER request, the server is signified that A is willing to
handle SUBSCRIBE and QAUTH methods (along with INVITE and MESSAGE
methods).
C's pending subscription request is submitted (with a QAUTH method) by
the server to principal A and A approves it.
A's presentity sends a 200 OK directly to C and a subscription for C is
instantiated at PUA level.

At this current time, there are thus 2 subscriptions active for A's
presentity presence service :
one granted for B and instantiated at server level and one granted for C
and instantiated at PUA level.
Suppose principal A changes his/her communications status
(description="open" for INVITE methods changes to description="inuse").

Question:
Q1)Does the draft imply that A has to send two NOTIFY : one directly to
C (subscription handled at PUA level) and one to proxyA which relays it
to B (subscription handled at server level) ?
This statement implies thus that proxyA has to subscribe to principal
A's presentity presence service.
Q2)Or is it so that when principal A becomes available again, a kind of
subscription transfer mechanism has to take place between the server and
A's PUA so that A's PUA repatriates all subscriptions instantiated at
server level.
That case would mean that if principal A changes its communications
status, his/her presentity would know all of the subscribed watchers and
would be capable of sending all NOTIFY directly to every watcher.

It might be interesting to clarify this issue in the draft.

Thanks in advance for your review,
N.D.
--
Nicolas DRAMAIS
Communications Software Engineering
Indigo Software
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