CWC: Simple and Stateless AQM Capable of Handling High Priority Thin Flows to Prevent Bufferbloat

Abstract

Bufferbloat is a serious problem where a router increases its queueing delay with the result that time-critical applications do not work properly. To overcome this problem, many researchers focus on AQM (Active Queue Management) and numerous methods have been proposed for implementing AQM. For example, in CoDel, routers may delete a packet in the queue based on the queueing delay as a metric. FQ-CoDel extends CoDel by introducing multiple queues to support priority control for high priority thin flows, but the complexity of queue management becomes higher. This paper proposes stateless and simple AQM referred to as CWC (CoDel with CHOKe), which combines two drop schemes, CoDel and CHOKe, to provide FQ-CoDel's performance using simpler control. Two methods called Packets CWC and Bytes CWC are proposed. In the simulation experiments, the average total throughput, sojourn time, bufferbloat occupancy, fairness index, and packet loss rate are compared. The results show that, for example, even when high priority thin UDP flows exist with many TCP flows, CWC decreases the average sojourn time by more than 50% compared with those of CoDel and FQ-CoDel, while it achieves a low average loss rate for thin UDP flows like FQ-CoDel and the same average total throughput compared with those of CoDel and FQ-CoDel. In addition, the above results are achieved under a TCP transient situation caused by TCP slow start.