On packet dropping schemes of active queue management mechanism for realizing robustness against network status changes

摘要

Recently, several gateway-based congestion control mechanisms have been proposed to support the end-to-end congestion control mechanism of TCP (Transmission Control Protocol). In this paper, we focus on RED (Random Early Detection), which is one of promising gateway-based congestion control mechanisms. RED randomly drops the arriving packet with a probability being proportional to its average queue length (i.e., the number of packets in the buffer). However, it is unclear whether the packet marking function of RED is optimal or not. In this paper, we investigate what type of packet marking function, which determines the packet dropping probability from the average queue length, is suitable from the viewpoint of steady state performance and transient behavior. By presenting several numerical examples, we investigate advantages and disadvantages of three packet marking functions: linear, concave, and convex. We show that although the average queue length in steady state becomes larger, use of the concave function makes the transient behavior of RED and the robustness against network status changes better.