Research and Implementation of VPN Based on IPSec

On the base of introducing the concept of VPN and its critical techniques,this paper focuses on the study of the key technique to implement VPN——IPSec and its architecture,working mode and related protocols.It analyzes the important role of VPN gateway in detail,presents the method to implement IPSec function on Linux system by using FreeS/WAN software package and modifying Linux 2.4 kernel,and provides the specific procedure to configure the VPN gateway,finally implements a VPN based on IPSec in Linux system.