The Research And Design Of VPN Gateway Applied By Small To Medium Business

With popularization of internet application, VPN become important more and more because it provides a way to, security, flexible, economical, build network for enterprise. There are two types of VPN, VPDN and VPN gateway. VPDN is used to protect data communication between remote or portable employee and corporation of interior network. VPN gateway is used to link filiales of local network and headquarters of local network by means of internet in security.Now mostly solutions of VPN gateway are found on IPSec protocol. The VPN gateway base on these solutions is transparent to upper network application. These solutions are very complex for implement. Development of high cost results in costly VPN gateway, so these solutions are misfit to internal small to medium businesses.In order to simplify the implement and reduce the development cost, this paper analyses the classic solution of IPSec based VPN gateway. According to IPSec protocol, with combination to internal small to medium businesses' application platform and their services (Web service, FTP service, email service, ERP and OA etc.), this paper proposes a new design of encrypting the transmitting IP packet on application layer using WinPcap, raw socket and CryptoAPI.This VPN gateway has been used successfully in wireless network's control system as a module. It provides opaque support to upper layer business application. Also it provides private protect and validates the integrity and authenticity to the IP packet which is transmitted among different LAN. At last, it implements the automated distribute and substitution of session key. As a result, this VPN gateway has worked well in practice.