Research On Congestion Control Protocol Of Transport Layer In A Localized OS

The congestion control mechanism is one of core technologies that the TCP protocol can provide efficient data transmission services.After years of development,there have been many versions of TCP congestion control protocol.However,with the continuous development of networks and applications,the emergence of new network structures and the introduction of different performance requirements in different network environments,traditional congestion control method is difficult to make it achieve good performance.Through analyzing the demand of a domestic operating system network protocol stack for the congestion control protocol,and shortcomings in the traditional congestion control algorithm TCP NewReno,combined with the available bandwidth estimation algorithm,this paper proposes an improved congestion control algorithm TCP NewRenoBw based on the available bandwidth estimation.The main research work is as follows:(1)Introduce bandwidth estimation method to obtain more congestion control information.Based on the analysis and research of congestion control algorithms TCP Westwood and TCP Vegas based on available bandwidth estimation,the granularity of available bandwidth is refined,and more information about congestion can be obtained through bandwidth estimation.It also helps design a more accurate control algorithm of congestion judgment and positioning improving network bandwidth utilization and competition fairness.(2)Use bandwidth estimation to optimize the slow-start threshold mechanism.The two conditions of bandwidth delay product and slow start threshold are used to determine whether to enter the congestion avoidance stage,which avoids the rapid increase of the congestion window in the late phase of the slow start stage,and can also avoid a requirement for a long time to reach an appropriate value in the congestion avoidance stage.Therefire,link utilization can be improved to a certain extent.(3)Improve mechanisms of fast retransmission and fast recovery mechanism.Available bandwidth is uesd to calculate the queue length of bottleneck link,and analyze reasons of the packet loss event,like whether it is caused by random error or congestion,so that the slow start threshold and congestion window can be set more reasonably.The design improves network performance partly.(4)Test software simulation design.This paper integrates improved measures into a new congestion control algorithm,designs a network scenario in the network simulation software NS3 to simulate,and analyzes it from three aspects including throughput,fairness and friendliness.The simulation results show that improved TCP NewRenoBw algorithm is better than traditional TCP NewReno algorithm in throughput,fairness,and friendliness.(5)Test in the protocol stack.The improved congestion control algorithm is implemented in the protocol stack,and the actual network environment is built and the throughput is tested.The experimental results show that the improved TCP NewRenoBw algorithm improves the throughput of the protocol stack.