Implementation Of Gateway Netfilter-based Ipv6/ipv4 Translation

IPv6 is the abbreviation of "The sixth version of Internet Protocol", which is the next generation of Internet Protocol designed by IETF with the destination to replace the current fourth version of Internet Protocol(IPv4). IPv4 has got brilliant achievement in past application, but now, many problems have appeared. Of all these problems, which is required to be urgent to be resolved is the absence of addresses. IPv6 can resolve many problems that IPv4 can't resolve by itself. And at the same time, many new protocol and technology has been added to IPv6, such as security, the auto-configuration of addresses, the mobility of IPv6 and better performance etc., so the trend that IPv6 will replace IPv4 won't change. But in the process of transferring, we must noticed one important problem that IPv4 protocol is not compatible with IPv6, furthermore, we may not upgrade the hosts, network equipments in Internet to IPv6 in one night, because it is not realistic. So we believe that before using IPv6 in large scale, there will undoubtedly exits a transition phase from IPv4 to IPv6. The duration of this phase depends on the growth speed of Internet. Obviously during the course of this phase IPv4 must co-exists with IPv6.This thesis first discussed the basic theory and knowledge of IPv6 and Netfilter under Linux and introduced the three mechanisms that IPv4 can co-exist with IPv6, that is dual protocol stack, tunneling and translation gateway. Then emphasized the translation gateway's realization which mainly resolved the problem that pure IPv6 node communicates with pure IPv4 node. On the base of it, we stressed the translation of protocols. The whole architecture based on the Linux Netfilter module which transferred the disposal of packets from kernel to user space which greatly improved the portability, extension, and simplicity of the system. It also made the network application program smoothly run between IPv4 network and IPv6 network.Finally, the thesis offered the test results and pointed the next work in the future.