Research On Congestion Control Algorithm For High-Speed Networks

The development of network technology such as optical communication technol-ogy leads to the appearance of many high-speed networks with high bandwidth-delay product.High-speed network illustrates a great prospect of application. But as a widely adopted data transfer protocol in current Internet, TCP performs badly in high-speed networks because of its congestion control algorithm. Other than traditional methods, explicit congestion control mechanisms are designed for high speed networks to better adapt to the increasingly requirements. In explicit congestion control mechanisms, routers compute multi-bits congestion imformation based on the network status; the in-formation is then feed back to the sender carried in the packet header; on the arrival of ACK packet, end-users ajust their sending rate or congestion window size according to the multi-bits feedback. Explicit congestion control mechanisms perform better than standard TCP congestion control mechanism in experimental conditions.Explicit congestion control algorithms have gained great concern in recent years. However, it is lack of a unified evaluation architecture. In this thesis, we propose a sys-tematic evaluation system, which suggest explicit congestion control algorithms evalua-tion should contain implementation cost analysis and performance evaluation. We de-fine evaluation metic and simulation benchmark, and then compare and analysis some explicit congestion control algorithms based on NS2.EMKC is an explicit congestion control algorithm which is designed for high speed networks. Simulation results above show that EMKC has stationary packet loss in equilibrium state, and convergents slowly to fairness. In this thesis, we propose two al-gorithms, EMKC-EL and EMKC-FC, to solve these two problems respectively.In EMKC-EL, we set a packet loss threshold, and partition the control into three different phases. Mathematical analysis and simulation results show that EMKC-EL de-creases stationary packet loss successfully.In EMKC-FC, routers probe the fair rate in a heuristic way and then feed it back to the senders. We add a four bytes field to EMKC's congetion header to carry some es-sential information. Simulation results show that EMKC-FC not only speeds up the fairness convergence rate, but also eliminates stationary packet loss.