This paper introduces the current state-of-the-art of SIP (Session Initiation Protocol) and the use of SIP in supporting P2P (peer-to-peer) applications on mobile phones. The use of SIP in All-IP mobile phones is a step toward achieving supernetworking, providing the user with powerful yet conceptually simple tools for sending and receiving multimedia content over a wireless network. The analysis includes an introduction of the application supernetworking concept in detail, with insight into the role of SIP in the current and future implementations.