Server Operating as a SIP Redirect

The SIP proxy can operate in the SIP redirect mode. In this mode the SIP server is very scalable, because it doesn't keep the state of transactions. Just after the initial INVITE, it replies to the UAC with a "302 Moved Temporarily" and gets off the SIP dialog. In this mode a SIP proxy, even with very few resources, can forward millions of calls per hour. It is normally used when you need high scalability, but don't need to bill the calls.