On designing improved controllers for AQM routers supporting TCP flows

TLDR

The paper studies a linearized TCP/AQM model and presents guidelines for designing stable controllers under varying network parameters. Classical control techniques are applied to design controllers, with simple implementation changes to RED, and their performance is verified through ns simulations. The proposed controllers exhibit superior theoretical properties to RED, and the PI design outperforms RED significantly.

Abstract

In this paper we study a previously developed linearized model of TCP and active queue management (AQM). We use classical control system techniques to develop controllers well suited for the application. The controllers are shown to have better theoretical properties than the well known RED controller. We present guidelines for designing stable controllers subject to network parameters like load level propagation delay etc. We also present simple implementation techniques which require a minimal change to RED implementations. The performance of the controllers are verified and compared with RED using ns simulations. The second of our designs, the proportional integral (PI) controller is shown to outperform RED significantly.