Research And Implementation Of NAT Protocol Based On Network Processor

Nowadays, with the rapid development of Internet, connecting to Internet becomes a popular trend. More and more LANs are connected with Internet, which causes the shortage of Internet IPv4 address. It is impossible to assign a unique IPv4 address for each workstation. To solve this problem, many technical innovations have been presented, among which NAT (Network Address Translation) technology is an outstanding solution. NAT is also an important security technology of network. But NAT implemented with pure software limits the throughput of Router seriously, and becomes the bottleneck of Router performance. To improve the performance of router, the key techniques of NAT protocol implemented on NP-based router are researched in this paper.First, we discuss the advantages and disadvantages of NAT protocol, current implementations of NAT protocol. Then with in-depth understanding of NAT principles, we analyse the process flow of network address translation in NAT protocol on various application scenarios. On the base of these analyses, we focus our study on the software structure of NP-based NAT and some key techniques in NAT protocol implementation. And we implement a basic NAT protocol with NP development platform. By actual test, our software can process packets with wire speed in fast Ethernet. Finally, the theoretic performance of this implementation is evaluated and the key techniques to broaden the use of our NAT implementation are presented.