Research On The Delay-based Congestion Control Mechanism Of End Host

The research of congestion control mechanism is always the hot spot in computer network research. Benefited by the fruit of congestion control mechanism research, the application of Internet can develop fast and operate stably. Aim at solving the disadvantage of TCP exist in the area of network congestion control, such as periodical dropping packets, low utilization of bandwidth resource in high speed network and wireless network, researchers proposed lots of improvement schemes. These schemes help the network to achieve high throughput, low drop rate and short end to end delay. On the basis of reviewing and classifying the latest research work of congestion control, there are several main work in this dissertation, include:(1) Firstly, we introduce the reliability problem of congestion predication in delay-based congestion control, then analyze the implication and find that PERT, as a kind of delay-based congestion control protocol ,which emulates AQM at end hosts, can have better performance in reliability of congestion predication, compared to other delay-based protocols.(2) Then, we research the design idea of PERT and find that PERT, taking delay as congestion signal, can't compete fair bandwidth share when it coexists with loss-based protocol(such as TCP) in the network. So we propose an improved PERT version, named MPERT. Base on the analysis of flow's steady-state throughput model, we make the adjustment factors of standard AIMD windows adjustment algorithm from static to dynamic, enable MPERT adaptive to diversity of network environment.(3) Finally, Through a large number of NS2-based experiments and analysis, we prove that MPERT not only can make bandwidth share fairness when coexist with TCP, but also keep the merit of PERT when exist in homogeneous environment, such as high link utilization, short end to end delay, and low drop rate. Additionally, it can fully utilize the high speed network bandwidth resource and improve the tolerance to wireless channel errors.this dissertation mainly solves the bandwidth share unfairness when delay-based protocol coexists with loss-based protocol, and explores the congestion control in high speed network and wireless network. All of these make a important sense for delay-based protocol's incremental deployment in future.