基于Petri网的Internet拥塞控制慢启动改进算法

An improved slow-start algorithm of Internet congestion control based on Petri net

针对Internet拥塞控制策略的慢启动过程中不同RTT的TCP流间在竞争带宽时的不公平性及慢启动后期拥塞窗口增长速度过快两个问题,建立基于Petri网的慢启动算法模型.通过对该模型的分析,发现导致这两个问题的原因是拥塞窗口的增长与RTT的大小成负指数增长关系,由此提出一种改进算法,在慢启动后期将拥塞窗口的增长与RTT的大小改为成正比关系,并用NS2仿真器进行仿真实验,结果表明改进算法有效解决了这两个问题.

In order to solve the two the competition of bandwidth in the problems （one is the unfairness of packages with different RTT values in source algorithm＇s slow-start phase of the Internet congestion control st.rategy,another is the increasing rate of the congestion window too fast in the slow-start phase＇s later stage）, a Petri net model for the behaviors of the slow-start algorithm is built. According to the analysis of the model, the solution for the problems is constructed, for example, increasing rate of the congestion window is in negative exponent to the values of the RTT. A improved slow-start algorithm is presented. The increasing rate of the congestion window should be direct proportion to the value of the RTT in the later stage of the slow-start phase. And the algorithm is implemented in the NS2. The simulation results indicate that the improved Slow-Start algorithm can reduce the aggression of the TCP flow, which has smaller RTT in the competition of bandwidth and decrease the increasing rate of the congestion.