[SIPForum-discussion] Basic questions about Presence Event Package (RFC 3856)

[Kaushik.V.Shah]

Here is my take on these questions.

Regards,
Kaushik

> Hi.
>
>
>
> I had redden the IETF RFC 3263 (Locating SIP Servers), the RFC 3680 (Event
> Package for Registrations) and the RFC 3856 (Presence Event Package)
>
>
>
> Now, I have some questions. Any hint about the following questions will
> help
> me a lot.
>
>
>
> 1)      The FRC 3856 says that a watcher can subscribe to a kind of
> server,
> to get information about the presence of some user. The presence of the
> user
> is updated with the PUA action, like following shown.
>
>
>
>
>
>    Watcher             Server                 PUA (Presence User Agent)
>       | F1 SUBSCRIBE      |                    |
>       |------------------>|                    |
>       | F2 200 OK         |                    |
>       |<------------------|                    |
>       | F3 NOTIFY         |                    |
>       |<------------------|                    |
>       | F4 200 OK         |                    |
>       |------------------>|                    |
>       |                   |                    |
>       |                   |   Update presence  |
>       |                   |<------------------ |
>       |                   |                    |
>       | F5 NOTIFY         |                    |
>       |<------------------|                    |
>       | F6 200 OK         |                    |
>       |------------------>|                    |
>
>
>       If the user turns off your device (Ex: turning off his SIP Phone),
> the
> PUA will update the user's presence with the Server. Then, the watcher can
> know the user is no more present in some device. However, if the same user
> turns on another device, but in some place completely out off the
> PUA/Server
> domain, how can the Server be updated correctly?
>

Servers have to be connected via some kind of "roaming" agreeement
between service providers or if it is same service provider, it can
be assumed to uniquely identify the user within its network and
update records accordingly.

>
> 2)      Where the Server must be running?

Typically where registrar server is running.

> 3)      How many PUA does exist for a user?

PUA is an integral part of SIP UA.

> 4)      How many Servers do exist for a user?

Typically servers serve # of users. So # of servers should
depend upon capacity being served.

> 5)      Where the PUAs must be running?

Same as #3.

> 6)      Does a SIP Phone have a PUA? If yes, how can it know where is the
> Server? If not, is it possible putting a PUA inside of a SIP Phone?

This should be configured in the SIP phone. I am not aware if locating
SIP server functionality has been extended to locate presence server or
not.

> 7)      How can the watcher and the user(PUA)  know that they are using a
> same Server?

They need not know.

> 8)      If the Server is a service, who should serve it? A private
> company?
> A public one?
>
>
>
>
> Thanks.
>
>
>
> Rodrigo Pimenta Carvalho.
>
> Brazil.
>
>
>
>
>
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