Vincent Luba wrote:

Hi,

I need some advices about a design issue. I'm trying to figure out how to manage my presence information notifications, using RFC 3856.

I have a situation in which end-to-end presence management wouldn't be suitable.

Still I'm wondering if server based presence management is a good idea. My thought is that it present a scalability issue.

The overall number of messages sent/received will be lower when using serverbased presence. Imagine a SIP client with modem connectin and 50 users on its buddylist:

end2end: 50xNOTIFY to the SIP proxy + 50xNOTIFY to the SIP clients + 50 responses (200 ok) + 50 responses

server based: 1xPUBLISH + 50xNOTIFY to the SIP clients +1 responses (200 ok) + 50 responses

This will lower the traffic on the SIP proxy and on the UAC side.

But of course, a presence server needs CPU power and has to store the presence locally in a database. Thus, as you see, this is a trade of.

simple server and high network traffic vs complicated server and low traffic and centralized features (buddy list...)

Additionally, you also have to consider SIP implementations. There are not thousands of SIP clients which supports all presence modes. Some clients supports end2end, some clients support server based. The same with SIP proxies.

Conlusion. Get some clients and implement both scenarios and find the one which fits your needs.

klaus

The point is that having the presence server would have to handle every single SUBSCRIBE & PUBLISH request then sends NOTIFY to every watchers.

Is it an efficient way to handle presence in a network with hundreds online users, everyone having tens of contact on their list.

Thank you for your comments

Luba Vincent

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