An ALG-Based NAT Traversal Solution for SIP-Based VoIP

Voice over the Internet Protocol (VoIP) is a very popular application nowadays. As an evolving technology, VoIP still faces several problems, one of which is referred as the NAT traversal problem. This problem exists because the commonly used VoIP protocol and NAT are not friendly to each other. Since SIP is the most relevant signaling protocol for VoIP today, this paper focuses on the SIP NAT traversal problem, and proposes an ALG-based SIP NAT traversal solution. A prototype system is also implemented and tested, and the experimental results show the validity of our solution.