中文摘要：

目前只有Teredo协议是专为NAT用户设计的一种IPv6隧道技术．但是，该协议不能为用户分配固定的IPv6地址，不支持对称类型的NAT用户，并且不能有效防御源地址欺骗攻击．针对这些不足，文章基于客户端一服务器隧道模式和服务器的有状态特性，提出一种新的IPv6隧道技术Silkroad．Silkroad协议在网络中引入隧道服务器，负责为NAT用户分配IPv6地址，然后作为中继器转发用户和IPv6网络之间的数据流．针对客户端一服务器隧道模式的不足，对NAT用户之间的通信进行优化，有效降低了通信开销．Silkroad协议支持所有类型的NAT用户和IPv6网络进行互连，能为用户分配固定不变的IPv6地址，并且具有更高的安全性．

英文摘要：

Teredo is the only one tunnel mechanism designed for NAT users. However, Teredo does not support symmetric NAT users and cannot allocate stable IPv6 addresses for the users, and also has security problems. Based on client-server tunnel mode and servers＇ statefule characteristic, a new tunnel mechanism named Silkroad is proposed to resolve Teredo＇s problems. The mechanism makes use of tunnel servers, which assign IPv6 addresses to users and then act as relays to transmit the packets between NAT users and IPv6 networks. In addition, an adaptive communication optimization scheme is presented to reduce the time cost of communication between two clients. Silkroad supports all types of NAT users to connect with IPv6 networks, can assign stable IPv6 addresses to the users and has high security.