Research About Implementation Of IPv4/IPv6 NAT-PT

With the rapid developmeng of the Internet, more and more users can access Internet. However, as the increasing of Internet users, IPv4 address space cannot meet the requirement of Internet development. The next generation IP protocol - IPv6 extend address length from 32bit to 128 bit, which could close the IP addresses shortage issue. In additionally, IPv6 simplificated header format, and enhanced in security, mobility, QoS. But most applications in Internet are based on IPv4, IPv4-IPv6 trasition need to take a long time. It is need to communicate between IPv4 network and IPv6 network. Network Address Translation - Protocol Translation (NAT-PT) provide a solution for IPv4-IPv6 communication. Add a translator between IPv4 network and IPv6 network to impelement address translation and protocol translation. By using NAT-PT, IPv4 and IPv6 can communicate without any change in internal.This paper, have reseached NAT algorithm and how to impelemented NAT-PT circuit. To save IPv4 address, choose NAPT in address translation. To inpelement NAPT, it needs to record the addresses and ports in a address-map hash table. The efficiency of NAT is depended on the Hash collision. By traffic statistic at packet headers from NLANR, analysised the randomicity of each bit in address and port. Base on the reseach result, optimized the XOR_SHIFT algorithm. Also using the traffic analysis results, build a packet stimulus to compare the performance with IPSX, CRC16, BOB, XOR_SHIFT. The result indicates, the optimized algorithm has low collision and complexity. Further more, discussed some NAT issues: connection finish detection, fast insert map record, reuse of address and port etc. In protocol translation, analysised how to translate IP, ICMP etc. descripted architecture, defined the function of submodules and the relationship between submodules. Finally, Finished NAT-PT circuits design, and do some functional test. This paper provided some testcases and test results.