The End-to-end Virtual Network System Design And Implementation

This thesis overall views the historical development * future trend and classification of virtual private network(VPN), and then discusses techniques which can realize virtual private network system and virtues of them. The article proposes the plan of the Point-To-Point VPN system and makes detailed design on the framework. After finished the plan of the system framework, the theories and techniques of VPN are lucubrated. Based on the plan and theories, the thesis mainly implemented a prototype of Windows client VPN software and gives some suggestions on future.In the VPN system framework design, the Point-To-Point VPN system plan was firstly presented, which was used to solve network security problem in LAN. After finished deeply studing pivotal techniques of Point-To-Point VPN system, IPSec protocols are advanced to implement the system on Linux operation system and Windows operation system, which can solve not only network security among different operation systems, but also universality and cooperation of the VPN system.During design and implementation of Windows client VPN software, the Windows NDIS device driver techniques and asynchronous I/O techniques were firstly used to implement IPSec kernel routines and full duplex communication between kernel routines and user routines. Using these techniques not only can overcome difficulties of kernel routines design under Windows operation system, but also can solve problem about use of IPSec in NAT environments.The prototype of Windows client VPN software was designed, made and functionally tested. The measured results are primarily satisfied the plan.