User location management for personal mobility in SIP-based VoIP services

Session Initial Protocol (SIP) is a signaling control protocol for creating, modifying, and terminating the multimedia sessions. SIP can provide personal mobility by addressing a single user located at different terminals according to a unique logical address. Moreover, user may register multiple contact addresses to VoIP servers and the server will fork the incoming request to these contact addresses. In this paper, we propose an improvement to reduce the traffic cost for sending INVITE requests by dividing the destination addresses into active and standby groups and phasing the forking processes. Furthermore, the numbers of miss calls and the repeated registrations will be bounded to balance performance and the accuracy of active group.