Revisiting Old Friends: Is CoDel Really Achieving What RED Cannot?

Abstract

We use ns-2 simulations to compare RED's gentle mode to CoDel in terms of their ability to reduce the latency for various TCP variants. We use a common dumbbell topology with Pareto background traffic, and measure the packet delays and transmission time of a 10MB FTP transfer. In our scenarios, we find that CoDel reduces the latency by 87%, but RED still manages to reduce it by 75%. However, the use of CoDel results in a transmission time 42% longer than when using RED. In light of its maturity, we therefore argue that RED could be considered as a good candidate to tackle Bufferbloat.