SIP+HTTP: "The values of asynchronous processing of requests in a converged HTTP/SIP application are tremendous. Having asynchronous processing in the game, there is no need to send an HTTP request in order for the UI to get updated, this can happen every time a new SIP message arrives.
Any action initiated by the sip endpoint will update the web application and vice versa. For example, when a new user registers, the REGISTER message will update the page to display the new user, and when the client clicks to call this new user, the sip endpoint will start ringing and so on.
A converged application will now be able to follow, present and react almost in real-time on every event that initiated from or destined to the HTTP/SIP Servlet container by any client, either a sip endpoint or a web browser." - from here.