RED算法的稳定性:基于非线性控制理论的分析

随机旱期检测（Radom Erly Detection,ERD)算法是主动队列管理（ActiveQueue Management,AQM)的有效实现算法，有关它性能的研究是近来网络研究的一个热点，在某些网络配置和负载状态下，RED存在稳定性问题，已有的关于RED稳定性的研究用不同的方法，从不同的角度定性或定量地揭示了可能的原因，并给出了稳定运行的工作区间，但没有对等幅振荡的队列行为给出一个合理的解释，在该文中，作者利用描述函这一非线性控制理论中经典的分析方法，分析了RED和getle-RED的工作特性，认为分组丢弃概率曲线中的非线性结构诱发的自激振荡是队列呈现周期运动的本质原因；虽然相比较而言，getle-RED比RED有更宽的稳定工作区间，但也是非常有限公司，解决AQM稳定性的理想途径是设计更为鲁棒的线性控制器。

Stability of RED Algorithm: Analysis Based on Nonlinear Control Theory

This paper analyzes the attributes of RED(Random Early Detection) and gentle-RED algorithms using the describing function approach, which is a classical analysis approach in nonlinear control theory. In fact, authors conclude that the essential reason that queue periodic motion is the self-oscillation caused by the nonlinear component in the packet dropping probability profile, this point is neglected by most of the existed schemes, and then deduce a more accurate criterion with which the stable operation region of RED scheme will be estimated, on the other hand, although gentle-RED is more powerful than RED to keep queues stable, this ability is very limited because it only extends the stable operation region with different nonlinear characteristic, but doesn't thoroughly eliminate it. The ideal solution should be to design more robust linear controller for AQM scheme.