Study And Implementation Of NAT Gateway

With the fast expansion of Internet, an urgent problem came out: We have not enough IP addresses. According to the consuming speed of IP address, there will be no more IP address to assign within 10 years.NAT technology is an important method of overcoming this problem. NAT allows multiple computers to share one global IP address to visit Internet, thus economized precious IP address resources. So NAT is widely used in Internet.In order to solve the main problems of IPv4, IETF starts to developInternet protocol of new generation-IPv6. IPv6 may replace existingIPv4 protocol in the future. Before IPv6 could replace IPv4, there must be a long transition period. During the period, NAT-PT technology is an important means for pure IPv6 and IPv4 networks to visit each other.It is obvious, no matter whether IPv6 could replace IPv4, NAT technology has a wide application prospect.This thesis has studied the NAT technology. At first, it analysed the technological principle and technological method of IPv4 NAPT gateway, Secondly, the thesis analysed the technology of IPv4-IPv6 gateway. At last, NAPT software gateway prototype system was presented, and details of design and implementation of some key modules appeared in the remaining pages of this thesis.