Research and implementation of Layer Two Tunneling Protocol (L2TP) on carrier network

As IPv4 addresses are being exhausted, researches on how to implement IPv6 [1] on carrier network are becoming valuable. IETF Softwire Group has proposed many useful methods, such as the Layer Two Tunneling Protocol (L2TP), towards this end. This paper firstly explains L2TP [2] tunnel technology in detail and then proposes the deployments of gateway mode and host mode in 6in4 and 4in6 scenarios. At last, the deployments of these different solutions in practical carrier network are described.