Fluid-flow analysis of TCP Westwood with RED

Abstract

This paper concerns TCP Westwood (TCPW), a recently developed modification of TCP, in combination with RED queue management. We develop a fluid-flow model of TCPW with RED and use it to study both equilibrium and dynamic features. On the equilibrium side, we identify the scaling of window with loss-probability, and compare it to TCP NewReno. We also use the model to find the boundary of stability, beyond which we see large oscillations; we find that the stable region of TCPW is enhanced with respect to TCP NewReno. Furthermore we show preliminary evidence that oscillations, when they occur, have a limited impact on network throughput. Fairness and friendliness of TCPW is also analyzed and compared with NewReno. Our results show that TCPW is more fair than NewReno for flows with heterogenous round trip time. We also found that TCPW friendliness to NewReno is dependent on the difference between equilibrium queue size and the product of bandwidth and delay.