Mathematical Problems in Engineering
Volume 2007 (2007), Article ID 54683, 17 pages
Research Article

Suboptimal RED Feedback Control for Buffered TCP Flow Dynamics in Computer Network

N. U. Ahmed and X. H. Ouyang

School of Information Technology and Engineering (SITE), University of Ottawa, 161 Louis Pasteur, P.O. Box 450, Ottawa K1N 6N5, ON, Canada

Received 24 November 2006; Accepted 5 February 2007

Academic Editor: Semyon M. Meerkov

Copyright © 2007 N. U. Ahmed and X. H. Ouyang. 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 present an improved dynamic system that simulates the behavior of TCP flows and active queue management (AQM) system. This system can be modeled by a set of stochastic differential equations driven by a doubly stochastic point process with intensities being the controls. The feedback laws proposed monitor the status of buffers and multiplexor of the router, detect incipient congestion by sending warning signals to the sources. The simulation results show that the optimal feedback control law from the class of linear as well as quadratic polynomials can improve the system performance significantly in terms of maximizing the link utilization, minimizing congestion, packet losses, as well as global synchronization. The optimization process used is based on random recursive search technique known as RRS.