A Control Theoretic Analysis of RED Chris Hollot Vishal Misra Don Towsley Wei-Bo Gong Department of ECE, Department of Computer Science University of Massachusetts, Amherst MA 01003 hollot,gong @ecs.umass.edu, misra,towsley @cs.umass.edu CMPSCI Technical Report TR 00-41 July 2000 Abstract In this report we use a previously developed nonlinear dynamic model of TCP to analyze and design Active Queue Management (AQM) Control Systems using RED. First, we linearize the interconnection of TCP and a bottlenecked queue and discuss its feedback properties in terms of net- work parameters such as link capacity, load and round-trip time. Using this model, we next design an AQM control system using the random early de- tection (RED) scheme by relating its free parameters such as the low-pass filter break point and loss probability profile to the network parameters. We present guidelines for designing linearly stable systems subject to network parameters like propogation delay and load level. Robustness to variations in system loads is a prime objective. We present ns simulations to support our analysis. This work is supported in part by the National Science Foundation under Grants ANI-9873328 and by DARPA under Contract DOD F30602-00-0554. Corresponding author 1