[SIPForum-discussion] Presence aggregation

[Szappanos Csaba]

Hi SIP forum members!

I've got another questions.

How to do Presence Aggregation? Last time I asked, how to handle more 
than one devices with the same SIP URI. Now I know that, but now I'm 
stuck again. I couldn't find any useful, for deciding, what to show to 
the others, if more clients has the same SIP URI and everyone of them 
has different presence status.
Should I show the weakest presence status (like available) as the 
aggregated presence, or should I show the strongest (like busy), or sort 
by priority? Or for example create a management web page, where users 
can change the priority or the policy? Or or or...
And if I got an aggregated presence status, which device should I ring 
in a click-to-call system? All availables, last changed to available, 
most prior available, most prior weakes etc. Is there an RFC or a 
standard for this?

I found 2 solutions for multiple devices with same SIP URIs:
1.) using SIP-Etag and SIP-If-Match headers in SIP messages
2.) using more tuple tags with different id, per PIDF XML document, like 
shown in RFC3863's examples. And if using PIDF with multiple tuple tags, 
can XLite decide the aggregated presence?
I can make somekind of an aggregated presence using 1.) and/or 2.), but 
I don't know will it be compatible with SIP clients.

Wow, thats a nice group of questions.
Thank you for your help, last time everyone was great!;)

Best regards,
Csaba Szappanos, Hungary