SIP-based mobile VPN for real-time applications

Mobile Virtual Private Network (VPN) has been developed to secure mobile user's communication between untrusted external networks and the protected private internal network. The IETF solution, however, leads to some problems: where should we put the external HA, how could we trust the external HA, and overhead of three tunnels. In this paper, we propose an alternative SIP-based mobile VPN. Because the proposed architecture is based on SIP, 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 that in IETF's mobile VPN. Besides, by using SRTP, cRTP, MIKEY, Diameter SIP Application, and MIDCOM ALG, the proposed architecture could 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.