Sip-based Network Address Through Design

The indelible advancement of IPv4 is known by all. Today's Internet is just build on it. But the address space of IPv4 will be used up in the near future.The shortage of address space has been a hindrance of the development of the Internet. To expand the address space, IPv6 had been puted forward.Rome was not build in one day. Concerning the cost and other problems, it will be a long time we see both IPv4 and IPv6 exist in our life. A lot of NAT equipment had been disposed to solve the problem of shortage of addresses of IPv4. This equipment can also provide the shield and protection of the private LANs.SIP protocol has good expansibility, tight combination with Internet and preeminent opening. It can support mobile equipment like mobile phone and PDA and multimedia application like the transmission of audio and video data. So, SIP protocol plays a very important roll in the implement of NGN and in KSZH too. To solve the problem of SIP's NAT traversal is very urgent.Firstly, this thesis briefly describes the foundation, network architecture and message format of SIP protocol. Then we investigate the development of NAT, and research the existent methods and status in quo of NAT Traversal at home and abroad. In chapter 4 and chapter 5, we talked about how UDP protocol and TCP ptotocol traverse NAT to build a foundation for SIP's NAT traversal. Further more, we discuss the problem concern with SIP's NAT traversal and provide the solution to solve it.