Research And Implementation Of L2TP Technology In VPN

Currently, VPN has increasingly wide range of applications and broad market prospects. VPN provides secure and reliable access to Internet, and ensures that data is transmitted securely under public infrastructure. And we don’t need to pay high fees for VPN, so various organizations prefer to use VPN technology to build their own private network. The main VPN technology includes GRE, IPSec, MPLS VPN, L2TP, etc. They have their own advantages and disadvantages, and are suitable for different occasions.L2TP, which is the same as L2F and PPTP, was designed to transmit PPP frame through tunnel and construct the VPDN network. In order to expand the application range of L2TP, IETF modified the protocol and proposed L2TPv3. L2TPv3 can be used to transmit many types of layer 2 frame data through tunnel, such as Ethernet, Frame Relay, ATM and other frame data. Compared with the previous version, the security of L2TPv3 has been greatly improved.L2TPv3 is researched in this paper. There is few research and literature about L2TPv3 in domestic currently. Most researches are mainly concentrated in the theoretical study, and rarely discuss the design and implementation of L2TPv3. In this paper, the principles of L2TPv3 are described in detail. The netwok topology of L2TPv3 and the management of control connection and session are analyzed. The calculation method of control message digest and hidden AVP are researched. In progress of project research, the software implementation of L2TPv3 and a new method of path MTU discovery which is applicable to L2TPv3 and can be used to get path MTU more quickly are proposed. The overall design, interface design, data structure design and program flow chart of internal module is given in the text. Finally, the software module is tested on the router. An implementation reference is provided for applications of L2TPv3 by this article.