TOD: Trend-Oriented Delay-Based Congestion Control in Lossless Datacenter Network

In current high-speed data center networks, congestion control is crucial for ensuring consistent high performance. Over the past decade, researchers and developers have explored several congestion signals such as ECN, RTT, and INT. However, most of the existing congestion control algorithms suffer from either imprecise congestion detection due to ambiguous signals or excessive bandwidth loss due to aggressive rate decrease. This paper proposes a novel congestion control mechanism called TOD, which is a trend-oriented delay-based approach designed for lossless data center networks. TOD leverages the change in RTT to learn the congestion trend and adjusts the sending rate accordingly. By analyzing the congestion trend, the sender reacts by adjusting the sending rate to a reasonable level, while still maintaining high bandwidth utilization to dismiss congestion. The sender uses a reference rate, which is calculated by the receiver and communicated back to the sender, to achieve this target. Therefore, TOD is a sender-receiver cooperative congestion control mechanism. We evaluate TOD extensively in NS-3 simulations using both microbenchmark and macrobenchmark. Our experiments demonstrate that TOD outperforms DCQCN and Timely in terms of FCT and convergence speed.