Research On Westwood Enhanced Congestion Control Algorithm And Implementation In Linux Network

With the rapid development of wireless network, people begin to enter the era ofmobile Internet. By Mobile terminals, people can access to the Internet anytime andanywhere. Also they can communicate with others and share valuable informationconveniently. The wireless network is gradually changing people’s lives. However,compared with the traditional wired network, the relatively of wireless network ispoor for its low bandwidth, high rate of random errors and mobile switching. Sowireless network often has a large number of packet loss.Generally speaking, the packet loss is caused by the poor reliability of thewireless network. In this case, it simply requires the retransmission of lost packets,without the need to invoke congestion control mechanism to reduce the transmissionrate. However, traditional TCP congestion control algorithm can not distinguishbetween the reasons of packet loss and it frequently reduces the TCP sending rate,which makes the performance of TCP significantly decreased in the wireless network.Therefore, it has become a hot topic of current research that how to effectivelyimprove the performance of the TCP in wireless network environment.Firstly, with a detailed analysis of westwood algorithm bandwidth estimationmechanism and the existing problems, an improved algorithm is proposed namedwestwood-c. The improved algorithm can distinguish between packet loss and delaythe emergence of TCP congestion by adding the loss differentiation mechanism andimproving the growth mechanism. In this way we can achieve higher networkresources utilization.Secondly, the network simulation software NS-2is used to evaluate thewestwood and westwood-c algorithm with a series of experiments, which to observethe throughput in a variety of environment, the friendliness of co-existing with thetraditional reno algorithm and the fairness of itself. The simulation results show thatwestwood-c algorithm is able to distinguish between the reasons of the packet lossand delay the emergence of TCP congestion. And the simulation results also show thatit can not only improve the throughput and bandwidth utilization of the wirelessnetwork, but also be able to maintain good TCP-friendliness and fairness. Finally, the expansion of the wireless network test bed in the laboratory isintroduced. Also westwood-c algorithm was dynamically inserted into the kernelmodule of the linux system. Then we do a number of experiments of which results demonstrates that the algorithm embedded in the actual wireless network environmentis successful.The major innovations of this paper are the followings:(1) An improved algorithm was proposed named westwood-c, which improvesthe growth mechanism of westwood algorithm and adds the loss differentiationmechanism.(2) The expansion of the wireless network test bed in the laboratory has beendone and westwood-c algorithm is dynamically inserted into the kernel module ofLinux system.Westwood-c algorithm can not only achieve higher bandwidth utilization andthroughput, but also be able to maintain the TCP-friendliness and fairness. It’s easy tobe realized that just the TCP sender being modified is enough, therefore it’s worthfurther researching on its value of reference and being applied to the actual network.