Research And Application Of Virtual Private Network Over UTCP

Virtual Private Network(VPN)is a secure technology for network communication.A lot of companies and governments use VPN to build internal private networks over the public networks,which allows people to access their working network in different regions and satisfies the variable needs of data encryption,private resource access and management for staff member.Because of the diversity of network environment,the optimization of protocol's adaption and transmission performance becomes a crucial key for improving client's experience.GRE,TCP and UDP are commonly used in the implementation of VPN and different protocols have different advantages and disadvantages.In the current network environment,the middle box or firewall may limit the usage of UDP port for security and resource control reason,which cause the VPN over UDP model fails to work,hence many implementation of VPN choose TCP as their backup option under this situation.However,because of the ordered delivery and re-transmission policy of TCP,the performance of VPN over TCP may incurs a significant loss.Taken the network ossification into consideration,it is a feasible way to make optimization on TCP.After doing a wide range of researches of VPN transmission technologies including it's model and base protocol,the main works of this paper are as follows:(1)Designed and implemented an out-of-order TCP protocol(uTCP).The solution is aimed at the VPN transmission model.The semantics of the original TCP protocol is modified and the re-transmission mechanism and the characteristics of in-order delivery are removed.The protocol stack delivers data packets in the buffer to the application layer in a FIFO manner.(2)The congestion control algorithm is designed based on the uTCP transmission model.In order to ensure the fairness of the protocol,this paper implements the BBR algorithm and makes some corresponding improvements.By introducing the packet loss-rate calculation model,the protocol is able to exchange loss-rate information dynamically.(3)Applying uTCP to virtual private networks and did corresponding performance tests in order to compare the fairness among VPNs flow under different protocols and the throughput under the network environment with packet loss.The experimental testing shows that the uTCP protocol designed in this paper can not only meets the requirement of traversing firewalls,but also solves the problem of performance impacts under the transmission of TCP in an environment with packet loss.In addition,this paper implemented a BBR congestion control algorithm with a packet loss rate feedback model on the basis of the uTCP protocol to ensure the fairness of VPN traffic,which also helps to maintain low latency in high bandwidth utilization and improve the transmission performance of VPN.