Research And Realization Of NAT Traversal Solutions In VoIP System Based On SIP Protocol

In recent years, along with the rapidly development of Internet and information industry, the data and the multimedia service become more and more important. The demand to combine network and the service is also urgent. Unfortunately, present network, regardless PSTN or the Internet is difficult to satisfy the demand. This brings forward the notion of Next Generation Networks based on the Softswitch and VoIP technology.In the process of VoIP improvement, many problems are came up and not allowed to neglect. Due to IP address as well as stemming from security and other reasons, the enterprise's network mostly used NAT(Network Address Translator) technology. But most NAT only supports few application protocols to transversal, such as HTTP/FTP. However, SIP took an important role to in the VoIP system. This article is focus on the NAT traversal's solution and realization for VoIP communication based on SIP.Firstly, the paper introduced the SIP protocol systemically, and analyzed the mechanism of NAT, presented the in-depth study of the SIP traversal of NAT, and many categories of solutions for SIP traversal of NAT are investigated.Based on the investigation,it is decided to use STUN to resolve the problem of SIP traversal. On this foundation, this paper proposed a novel NAT traversal solution based on P2P model, combining STUN and TURN.