Steady State Analysis of the RED Gateway: Stability, Transient Behavior, and Parameter Setting
Hiroyuki Ohsaki, Masayuki Murata, Hideo Miyahara · 2000
Several gateway-based congestion control mechanisms have been proposed to support an end-to-end congestion control mechanism of TCP (Transmission Control Protocol) . One of promising gateway-based congestion control mechanisms is a RED (Random Early Detection) gateway. Although effectiveness of the RED gateway is fully dependent on a choice of control parameters, it has not been fully investigated how to configure its control parameters. In this paper, we analyze the steady state behavior of the RED gateway by explicitly modeling the congestion control mechanism of TCP. We first derive the equilibrium values of the TCP window size and the buffer occupancy of the RED gateway. Also derived are the stability condition and the transient performance index of the network by using a control theoretic approach. Numerical examples as well as simulation results are presented to clearly show relations between control parameters and the steady state behavior. Our findings are: (1) max p (maximum packet marking probability) mostly affects the RED's buffer occupancy, (2) the network becomes more stable as the number of TCP connections or the bandwidth--delay product increases, and (3) min th (minimum threshold) is a key parameter for optimizing the transient performance. We finally discuss how control parameters of the RED gateway should be configured for achieving better performance.