On Designing Improved Controllers for AQIM Routers Supporting TCP Flows

In this paper we study a previously developed linearized model of TCP and AQM. We use classical control system techniques to develop controllers weU suited for the application. The controllers are shown to have better theoretical properties than the wetll known RED controller. We present gnidetines for designing stable controllers subject to network parameters tike load level, propagation delay etc. We also present simple implementation techniques wtdch 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.