Research Of Explicit Congestion Control Protocol In Wired/Wireless Networks

With rapid advances in the deployment of very high speed links in the wired core network and growing requirements of high speed wireless access over wired/wireless hybrid networks, the traditional congestion control (TCP) mechanisms suffers great inefficiency, unfairness, oscillation and long queuing delay. Various transport protocols have been suggested to address these problems in recent years. This thesis mainly discusses congestion control protocols based on ECN (Explicit Congestion Notification). The source uses the load information from the inner routers to update its congestion window. Therefore, ECN-based protocols can control the network behavior more accurately and obtain better performance.Firstly, the thesis reviews the researches of TCP in recent years, mainly focuses on ECN-based protocols over wired/wireless hybrid networks including one IEEE 802.11 hop. Based on this study, the thesis emphatically analyzes the influence of RTT, bandwidth of the bottleneck link, router buffer size and the number of flows on the performance of explicit feedback protocols XCP and XCP-B.In the following, this thesis presents a fast transport protocol based on explicit congestion notification over wired/wireless networks ARROW-WTCP (AcceleRate tRansmission towards Optical window size TCP for Wireless network), which provides a joint design of source and router algorithms. They form a closed feedback control system. ARROW-WTCP enables feasible deployment of ARROW-TCP from wired to wireless networks. Simulation results demonstrate that ARROW-WTCP outperforms XCP-B in terms of stability, fairness, convergence and utilization under highly dynamic wireless networks.Finally, the thesis summarizes the current existing open issues, and provides some further interesting directions on explicit feedback congestion control protocols over high-speed wired networks and multi-hop wireless networks.