一种基于正态分布函数的新TCP拥塞控制机制

A NEW TCP CONGESTION CONTROL MECHANISM BASED ON NORMAL DISTRIBUTED FUNCTION

目前,拥塞控制已成为确保互联网稳定性与鲁棒性的极其重要因素。然而,目前的TCP拥塞控制机制使用AIMD(Additive Increase Multipli-cative Decrease)算法,其加性增加乘性减小的合理性与稳定性存在着现实问题。为此,我们改进了原有的AIMD算法,提供了一种基于正态分布函数的新TCP拥塞控制机制。并把整个拥塞避免、快速重传与恢复阶段分为轻载、过载和拥塞三种状态,根据调控触发值,区别选用不同算法实现。最后还从数学角度对新机制及其算法的合理性和可行性进行了分析与证明。同时,NS3的仿真结果显示,新的TCP拥塞控制机制可明显降低丢包率、平缓突发流量冲击,并可增加带宽的有效利用率、提高系统吞吐量。

So far the congestion control has become the most important factor to ensure the stabi l ity and robustness of the Internet. However, the AIMD algorithm used in TCP congestion control mechanism currently is unstable and insufficient. There exist practical problems in the rationality and stability of the additive increase and the multiplicative reduction. To solve these problems, we provide a new TCP congestion control mechanism, based on normal distributed function, instead of the AIMD algorithm. And the whole congestion avoidance, fast retransmit and recovery phase are divided into three states l ight load, overload and congestion, according to the regulation of the difference between the trigger value use different algorithms. Finally, the rationality and feasibility of the new algorithm have been verified by using mathematical analysis. Furthermore, the simulation results from NS3 demonstrate that the new TCP congestion control mechanism can obviously reduce packet losses and the impact of network burst transmission, improve the bandwidth utilization ratio and the network throughput.