| It is hard for IPv4 to satisfiy the future nework requirements due to its inherent limits such as small address space. Next Generation Internet protocol, called IPv6, is designed to address the issues of IPv4. However, the migration of IPv4 to IPv6 will not happen overnight. Rather, there will be a period of transition when both protocols are in use over the same infrastructure. It is important to research IPv4/IPv6 coexistence and migration technologies, which will promote the transition from IPv4 to IPv6.NAT is an effective technology designed for overcoming address shortage or protecting inner networks, it is widely adopted while constructing networks of enterprises, schools and government departments. Especially in China, NAT is used at large due to the short of address. So, connecting NAT users to IPv6 networks during IPv4/IPv6 transition period is very important. Tunneling is one of the main migration technologies. However, nowaday tunnel mechanisms either do not support NAT users or support not well. This dissertation focuses on problems of these mechanisms. The main work and innovation of the dissertation are listed as follows.1. A new NAT users-orinted IPv6 tunnel mechanism named Silkroad is proposed. By far, Microsoft's Teredo is the only tunnel mechanism that supports NAT users in a certain extent, but meanwhile has many limits such as not supporting symmetric NAT, not being able to provide bidirectional IPv6 connections, having poor security, etc. Silkroad exploits the client-server tunnel mode and makes use of the stateful characteristic of tunnel servers to resolve the Teredo's problems. Silkroad can provide bidirectional IPv6 connections for all type of NAT users and that has high security.2. The client-server tunnel mode has limits: packet exchange between NAT users must traverse a trigonal route from the source to the tunnel server and then the destination. The dissertation proposes an adaptive route optimization method to resolve the problem. If length of the session... |
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