SIP-based mobile VPN for real-time applications

A mobile virtual private network (VPN) has been developed to secure a mobile user's communication between entrusted external networks and the protected private internal network. IETF's solution, however, leads to some problems: where the external HA (home agent) should be put; how to trust the external HA; the overhead of three tunnels. We propose an alternative SIP-based mobile VPN. Because the proposed architecture is based on SIP (session initiation protocol), the problems inherited from Mobile IP are not problems in our architecture. In addition, there is no need to tunnel a packet three times, as in IETF's mobile VPN. Besides, by using SRTP, cRTP, MIKEY, Diameter SIP Application, and MIDCOM ALG, the proposed architecture can also provide VPN services for mobile users effectively. The proposed technique has been implemented in a mobile VPN testbed. Empirical experiments with a VoIP application were conducted to analyze the performance in terms of bandwidth consumption, end-to-end delay, and handoff latency.