瓶颈网络TCP/主动队列管理模型及仿真

TCP/Active Queue Management Model and Simulation for Bottleneck Networks

提出了一种基于离散时间Markov链的时延闭环反馈TCP/AQM(Active Queue Management)模型,并得到其稳态分布。通过以环路时延为单位,将系统时间分割成长度不同的时隙,分析每个时隙内TCP发送端发送窗口模型和瓶颈路由器队列模型。通过结合相邻时隙的参数,提出了TCP/AQM整体分析模型。该模型可以估计路由器的队列平均长度和丢包率、TCP发送端的平均发送窗口值,因此可以用于分析AQM算法性能以及给新算法的设计提供理论支持。通过在Matlab实施该模型与NS2仿真结果作比较,证实了该模型在模拟时延闭环反馈的TCP/RED系统的有效性。

A novel delayed closed-loop feedback TCP/AQM analytical model was proposed by using discrete-time Markov chain, and the calculation method for equilibrium distribution was given. The system time was divided to time slots with the cycle of RTT （Round Trip Time） with different lengths. In each slot, the bottleneck router queue model and TCP window size model were analyzed. By combining adjacent slots, an integrated TCP/AQM analytical model was developed. The expectation values of packets dropping ratio and queue length in the bottleneck router and TCP senders ＂window size could be estimated, hence, it is a useful tool for the analysis of AQMs and supporting the development of new AQM schemes theoretically. By implementing this model on Matlab, its solutions were compared to NS2 simulated solutions, and the validity of the model to analyze the closed-loop feedback TCP/RED system was verified.