Mathematical Problems in Engineering
Volume 2005 (2005), Issue 5, Pages 477-489

Suboptimal feedback control of TCP flows in computer network using random early discard (RED) mechanism

N. U. Ahmed and Cheng Li

School of Information Technology and Engineering, University of Ottawa, Ottawa K1N 6N5, ON, Canada

Received 8 February 2005

Copyright © 2005 N. U. Ahmed and Cheng Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We consider a dynamic model that simulates the interaction of TCP sources with active queue management system (AQM). We propose a modified version of an earlier dynamic model called RED. This is governed by a system of stochastic differential equations driven by a doubly stochastic point process with intensity as the control. The feedback control law proposed observes the router (queue) status and controls the intensity by sending congestion signals (warnings) to the sources for adjustment of their transmission rates. The (feedback) control laws used are of polynomial type (including linear) with adjustable coefficients. They are optimized by use of genetic algorithm (GA) and random recursive search (RRS) technique. The numerical results demonstrate that the proposed model and the method can improve the system performance significantly.