A VPN MODEL BASED ON IP ENCAPSULATION

This paper first introduces IPSec protocols,including AH（Authentication Header） Protocol and ESP（Encapsulation Security Protocol）,discusses the complexity to achieve IPSec ,and analyses the theory of IP in IP tunneling encapsulation in Linux based on two aspects of transferring and receiving. Then it presents a VPN solution based on Linux IP encapsulation, the extended IPIP packet structure and system process. Finally, the achievement of FreeS/WAN is analyzed, and it is concluded that the VPN model based on IP encapsulation is better than FreeS/WAN in achievement and performance.