VCP协议公平性算法的仿真分析与改进研究

Simulation study of VCP fairness algorithm and its improvement

变结构控制协议(variable-structure congestion control protocol,VCP)是一种高带宽时延网络环境下良好的拥塞控制机制,但当各数据流之间往返时延差异较大时,系统表现出不公平。结合NS2仿真实验,分析了在VCP同步数据流和异步数据流作用下系统的公平性。建立了VCP数据流稳态吞吐量的一个简单模型,指出了数据流稳态吞吐量与其公平性算法乘减参数的实际均值有关。通过在端系统自适应调整公平性算法加性参数的权值,有效提高了异步数据流作用下系统的公平性。最后通过仿真实验验证了改进算法的有效性。

Variable-structure congestion control protocol （VCP） is an effective congestion control mecha- nism for high bandwidth-delay product networks, but the fairness of VCP asynchronous flows with large round trip time （RTT） variance become worse. To address this problem, the fairness of synchronous and asyn- chronous flows is analyzed based on the NS2 system respectively, and then a simple steady state throughput model is proposed. The state throughput of VCP flows is associated with the mean of multiplicative decrease factor of the VCP fairness algorithm. By adaptively adjusting the weight of addictive increase factor of the VCP fairness algorithm in end systems, the fairness of asynchronous flows is improved effectively. Finally, the improved algorithm is verified with the NS2 system.