On the Non-Linearity of the RED Drop Function
Erich Plasser, Thomas Ziegler, Peter Reichl · 2002
This paper discusses the shape of the RED drop function necessary to confirm the requirements for AQM design. A proper AQM design implies the avoidance of forced drops and link under-utilization as well as the applicability to a wide load range. With some examples from simulations we illustrate that the original linear RED drop function cannot cope with all of these requirements. For investigations in this paper, we use these examples to set conditions a proper drop function has to comply with. Bearing these conditions in mind, we propose two non-linear approaches for the drop function. At first, we establish a heuristic approach, where a class of functions originates, with one parameter free to define. A second approach is based on a mathematical model for the TCP window system as well as on one parameter yielded from measurements and estimations. With simulations we demonstrate that the eligible non-linear drop functions perform better in avoiding forced drops and link under-utilization and especially are applicable to a broader range of loads compared to the original linear RED function. Keywords: Active Queue Management, RED, TCP, Congestion Avoidance 1.