Congestion Control Source Algorithms' Research

The existing congestion control mechanism can't satisfy the need of new Internet with the development of new network technology, especially the appearance of the High Bandwidth-Delay-Product Network. So, more and more scientists begin the research of this field and make it become a hot research field.Since Floyd has proposed that routers can become a part of congestion control mechanism, so the end node can get more nicety feedback about the network's congestion state. But this makes routers more busy and it is very difficult to come true. Then the research of source algorithms become greatly activity. In resent years, many new congestion control protocols have been proposed: HSTCP, STCP, BIC-TCP, CUBIC-TCP, H-TCP and Fast-TCP. These source algorithms based on different important points have the same aims: good congestion control ability, fast congestion response, good congestion deduction ability and excellent stability, fairness between flows, convergence and high bottleneck link utilization. These source algorithms use the same windows'adjustment(AIMD). Their difference lies on the value of the increase parameterαand the decrease parameterβ.The difference makes the performances of these source algorithms greatly different. This paper's purpose is looking for the best congestion control source algorithm and modifying it for better performance. Based on the purpose, we analyze and compare the most important source algorithms and find the best algorithm: H-TCP. With more research about this algorithm, we find there are two shortcomings in H-TCP, so we ameliorate this algorithm.We analyze capabilities of these algorithms based on the common AIMD model and response function of each algorithm. Then we point out the insufficiency of each algorithm. Then we use NS-2 to simulate these algorithms and validate the analyzing result. After comparing we find H-TCP has the best integration capability. But H-TCP protocol also has two shortcomings: bad RTT-Fairness and low TCP-Friendly. Finally based on H-TCP protocol, we propose RH-TCP protocol which mends the shortcomings of H-TCP and keeps the merits of H-TCP. The result of experiments prove that RH-TCP get good performances. The main work in this paper is :...