dBFC: Destination-based Backpressure Flow Control for Incast

Incast happens in data center networks (DCNs) when many senders simultaneously send flows to one receiver. Incast occurs frequently and compromises flow performance severely. However, widely deployed end-to-end congestion control (CC) protocols are inefficient at handling incast, as they rely on delayed congestion signals and can not isolate incast flows. Recently, researchers have favored per-hop flow control protocols since they could achieve fast reaction and incast isolation. Nevertheless, these impressive advantages are impractical because of hardware resource limitations.In this paper, we present a new per-hop flow control protocol dBFC (Destination-based Backpressure Flow Control), which achieves these advantages within limited hardware resources. Our key insight is that the number of destinations reached by queued packets in a port is minuscule. dBFC is compatible with existing CC protocols. We use large-scale NS3 simulations to evaluate dBFC. In our evaluation, compared with deployed CC protocols and the state-of-the-art per-hop flow control protocol, dBFC reduces the maximum buffer occupancy by 5 − 23× and thus provides up to 21× lower flow completion time of small flows in limited hardware resources.