Subject: [Simple] Misunderstanding of Presence Service with SIP

From: Hélène Montarou <[email-masked]>
Date: Tue, 29 Jan 2002 13:25:03 -0500

Dear Sir,

 I am studying SIP and the presence service.
 There is some points I misunderstand concerning the model proposed in
 RFC 2778 and the analogy between PUA's addresses and
 presentities'addresses.

 A. Concerning the model :

 So, if I understand well:
 - A principal can manipulate zero or more presentities,
 - A principal interacts with the system via one or several user agents
 so one or several Presence User Agent (PUA),
 - A PUA can not have several presentities due to an addressing problem
 but several PUAs can send their presence information to the same
 presentity.

 Finally, the configuration in the document attached (configuration.ps)
are allowed.

  Is it correct from now?

 - We supposed all the entities are colocalised.
 In the second case, PUAs share the same address so that the presentity
 can be reach via this same address, is not it ??
 In this case, we could say that the address identify uniquely the
 principal.
 In the first case, presentities have different addresses. Only PUAs of
 the Principal can be identify uniquely through presentities. A watcher
 which would like to know the principal presence information (state of
 all devices and services on devices of this principal) has to know the
 PUAs ' presentities addresses, is not it ??
 As an example , PUAs could be different programs/applications.. so
 services on the same computer like email, phone, conference.. etc.. is
 that correct ?   could you give me some more example ?

 -  When PUAs and presentities are delocalised, they can have different
 addresses.
 If we consider both configuration above, how is it possible to identify

 a PUA uniquely for a watcher ? and principal uniquely ?
 What should be the presentity address in particular in the second case
?

 As an example, PUAs could be programs/applications/several devices
 (mobile phone, fixe phone and PC ) with three different addresses. For
 this example, is the second configuration still allowed?

 B.  Concerning the CPIM format:

 - The presence information contained  in a tuple concern a PUA.
 - A list of tuples for the same presentity means that several PUAs send

 information at the same presentity.

 Is it correct ?

 Here the example from the Internet Draft "CPIM Presence Information
Data
 Format":

  <presence xmlns="urn:ietf:params:cpim-presence:">
      <presentity id="pres:[email-masked]"/>
         <tuple id="mobile-im">
             <status>
                 <value>OPEN</value>
                 <value

type="urn:ietf:params:cpim-presence:status-type:im">BUSY</value>
                 <value
                   type="urn:example-com:cpim-status-type:location"

schema="http://www.example.com/impp/location.dtd">HOME</value>
              </status>
              <contact
priority="2">im:[email-masked]</contact>
              <note>Don't Disturb Please!</note>
              <timestamp>2001-10-27T16:49:29Z</timestamp>
         </tuple>
         <tuple id="email">
             <status>
             <value>OPEN</value>
             </status>
            <contact priority="1">mailto:[email-masked]</contact>

         </tuple>
         <note>I'll be in Tokyo tomorrow</note>
   </presence>

 Could you explain it in terms of Principal, PUA, Presentity, devices,
services and
 addresses ?

 Waiting for your answer, I thank you very much in advance.
 This would help me a lot in my understanding of SIP and presence.

 Regards,

Hélène Montarou.

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