The Research Of Network Congestion Performance Analysis Base On Highspeed TCP

In these years, with the popularization of the computer network and the rapidly increasing of network users, the research of network congestion control algorithm becomes more and more important. TCP/IP is a network technology which comes from practices and is developed in practices. TCP/IP also is the most popular end-to-end transmission protocol in the Internet now, and the stability of the Internet has the close relationship with TCP's successful congestion control algorithm.But along with the 1000 Mbps above high-speed networks going out of the lab and going into practice, regular TCP do not achieve good performance when running on such networks. So Floyd gives a algorithm named High-speed TCP(HSTCP) aimed to achieve better performance in high-speed network.Firstly, this paper analyzed the network architecture and pointed out that network congestion closely related to Internet design. At the same time some related subject such as cause of congestion, difficult of algorithm design and evaluation criteria have been illustrated.Secondly, base on thorough study the current TCP source algorithms, this paper analyzes the slow-start of TCP congestion control which has been one of hotspots in TCP source algorithm study and its problem. A new variant slow-start scheme is presented which approaches the slow-start threshold more gradually and resolve the problem of burstiness between the slow-start and congestion avoidance phases through introducing a proportional factor. The comparison of NS simulation results show that this new slow-start scheme can significantly reduce both packet losses and traffic burstiness.At last, current TCP congestion control cannot achieve enough bandwidth in high-speed networks, HSTCP has been proposed as one of the possible waysto solve this problem. Experiments revealed that HSTCP can use the bandwidth more sufficient than current TCP, but it has severe RTT unfairness. In this paper, we first investigate the RTT unfairness through mathematical analysis and simulation studies, and then we add a fair factor to the HSTCP to decrease the difference of window increase caused by different RTT. Experiments show that the modified algorithm can guarantee the bandwidth fairness of HSTCP flows and reduce the packets loss rate.