Abstract: In this paper, we present an embedded Markov chain to model the competition of flow that use TCP Reno and TCP Vegas. Our model precisely describes not only the Slow-Start, Congestion-Avoidance, and the Fast-Retransmit/Fast-Recovery phases, but also the effect of different response methods to various number of packet drops in one window of TCP Reno and TCP Vegas. Our model can also be adjusted to handle Delayed ACK and NewReno. A Monta-Carlo simulation algorithm was proposed for situations when the number of competition flows is very large. The results of NS-2 simulation demonstrate that our model is quite accurate, with average error less than 6% and less than 8% when Monta-Carlo simulation is used.

Key words: TCP Reno, TCP Vegas, Competition Analysis

摘要： 本文提出了一种对TCP Reno与TCP Vegas的竞争进行分析的嵌入式马尔科夫模型。我们的模型不但能对Reno和Vegas的慢启动阶段、拥塞避免阶段和快速重传/快速恢复阶段进行精确的描述，还能对在一个窗口内发生多次丢包对性能的影响进行区分。此外，我们的模型还能方便地扩展到延迟确认和NewReno的情况，以及多个流并存的情况。对于网络中流的规模较大时，我们提出了一种Monta-Carlo模拟算法。我们用NS-2仿真软件对模型的准确性进行了验证，结果表明我们的数学模型的平均误差不超过6%，使用Monta-Carlo模拟的平均误差不超过8%。

关键词: TCP Reno, TCP Vegas, 竞争性分析