Study Of VPDN Technology Based On L2TP And Applications To BRAS

In broadband networks, broadband remote access server is a core equipment used to manage the networks. The virtual private dial-up network(VPDN), as an important job of a Broadband remote access server, is making more and more applications for virtual private network. The research of VPDN technology is important for the development of Broadband networks.The broadband remote access server BRAS designed in this paper provides VPDN function supported by layer 2 tunnel protocol, while traditional ones do not. In this paper, the system components and the operating principle of a VPDN are studyed. Besides, the business types and realization methods of a VPDN are analysed. And also, the structure and the form of layer 2 transport protocol packets are introduced in detail. The research of building a VPDN based on L2TP protocol is the mainly work of this project.The actual demand of the project is concerned while ascertaining the design scheme of this VPDN module. It is divided into Network processing module, Protocol processing module, Message processing module, PPP processing module by functional demand. And we design the state machine by its business process. There are some key technologys such as the Init of L2TP, Timer and Debug in this paper. In the end, we achieved all functions of this VPDN module in BRAS as a LAC.