[SIPForum-discussion] SIP subscription and notification mechanism questions

[mtsai at sunrisetelecom.com]

Hi,

I have several questions about SIP subscription and notification
mechanism(RFC3265 or others):

1. Where can I find good source of description about it? The articles that I can find on the Web are quite confusing. It seems it's all covered in RFC3265. However, there are some other RFC's also seem to relate to it.
2. What are their applications in real life? Is "presence" one of the applications?
3. Is there any free service or software which support this mechanism for both subscriber(client) and notifier(server)?
 
Please advice. Thanks in advance!
 
Matt