Flash: Joint Flow Scheduling and Congestion Control in Data Center Networks

Flow scheduling and congestion control are two important techniques to reduce flow completion time in data center networks. While existing works largely treat them independently, the interactions between flow scheduling and congestion control are in general overlooked which leads to sub-optimal solutions, especially given that the link capacity is increasing faster than the switch port buffer size. In this paper, we present Flash, a simple yet effective scheme that integrates scheduling and congestion control. Specifically, Flash puts forward a congestion-aware scheduling scheme to determine the priority of flows based on the latest network congestion extent and the flow's bytes sent. Besides, Flash proposes a priority-based packet dropping scheme in switch port buffers and implements a priority-aware congestion control scheme. Experiment results show that Flash has superior performance: (1) it has 35.8% lower tail latency than PIAS and performs similar with pFabric in a 10G network without knowing the flow size, (2) in 100G networks with shallow buffers, the information agnostic Flash has 6.8% lower average FCT than the information-aware pFabric, (3) it outperforms pFabric by 13.5% in FCT if flow size is also known to Flash.