IPv6 Tunnel Broker is one of important mechanisms of transition from IPv4 to IPv6. However
This mechanism does not support NAT users
also not specific a way to balance the load of tunnel servers. The function of Broker Server and Tunnel Server is modified to support NAT users. Meanwhile
a new dispatching method is proposed for balancing the load between tunnel servers.Simulation result shows that the method has better performance than other general dispatching methods have.