Design And Implementation Of L2TP System Based On Router

Along with the opening and the scale that increased day-by-day of the network, the people's demands for the network had become even more diversified. Layer Two Tunneling Protocol (L2TP) just appeared in such condition, which can meet the demands for visiting the company's internal server from other place with a remote dial client over the Internet. It is just like a special and secure virtual tunnel established between the two ends. Then the remote client can visit the company's internal data across the Internet.The company's internal server is a access router which support the Layer Two Tunneling Protocol (L2TP), and it also be known as L2TP Network Server (LNS). The aim of this paper is to achieve the support of L2TP in the vanlink router, and then the vanlink router can work as LNS that support the application of the virtual tunneling. In this paper, the research work can be summarized in the following aspects:Firstly, the background of Virtual Private Dial-up Networks (VPDN) and L2TP is summarized. Then the reasons why choose L2TP to support VPDN are pointed out. The theory and establishment process of L2TP are mainly studied. And the message format of L2TP and the function of kinds of messages used for information exchange are analyzed in depth.Secondly, the L2TP system is designed and implemented. By analyzing the work theory and the process of each module, the key of the design and the frame flow of the program are indicated, which are the emphases of design and implement in each module. Then some key points of the each module are mainly introduced, and the pseudocode is also used to display how to implement each module.Thirdly, the key techniques related to the implementation of the L2TP system are analyzed and studied in detail, including the flow control and the mistake control, the encapsulation and analysis of the attribute, and the Encryption and decryption algorithm. They are the basis of the implementation, and also the key to the system's quality assurance.Finally, the L2TP system testing environment is set up. The L2TP system is tested from the functionality and the performance in detail. The testing process and the results are displayed by the screenshots of the running system and the coordinate graphes that are draw by testing data. The testing results indicate that the system reaches the anticipated effect.