PI(proportional integral)主动队列管理机制是应用控制理论中的比例积分控制器设计的主动队列管理机制,其性能优于RED(random early detection)算法,能有效地消除稳态误差.但PI算法默认参数在目标队列长度较小情况下收敛速度较慢:而参数整定上的试凑法,无法同时保障系统的瞬态和稳态性能.研究拥塞产生的原因及其表现形式,提出一种基于报文到达速率的PI算法(Rate based Proportional and Integral,RPI).它根据报文到达速率和队列长度,即拥塞瞬间状况和持续状况计算出合适的丢弃率.通过NS2模拟表明,相对于PI,RPI具有更快的收敛速度和更小的队列抖动.
Proportional integral (PI) controller of control theory is introduced into AQM. Although the performance of PI AQM is su- perior to that of random early detection ( RED), its convergence speed is slow especially when the target length of queue is smaller. The testing method of choosing parameters can't guarantee transient and stability at the same time. This paper proposes a Rate based Proportional and Integral (RPI) according to the aggregate packet arrival rate in the router. RPI adopt appropriate dropping probability by the strictness degree and the trend of change. Verified by using NS-2 simulations, RPI can achieve faster convergence speed and smaller queue oscillation than PI.