LossPass: Absorbing Microbursts by Packet Eviction for Data Center Networks

A bursty traffic pattern, called the microburst, is a key hurdle to achieve low latency for user-facing applications because it causes excessive packet losses in shallow buffered switches. Explicit Congestion Notification (ECN) can absorb microbursts by reserving buffer headroom, but the existence of headroom results in a fundamental trade-off between latency and throughput. To this end, we present LossPass, a buffer sharing mechanism that absorbs microbursts as many as possible while maintaining line-rate throughput. Specifically, LossPass evicts buffered large flow packets to make free buffer space on demand for arriving small flow packets. Our solution is inexpensive to implement on hardware. We implement a LossPass prototype and evaluate its performance through extensive testbed experiments and large-scale simulations. Our evaluation results show that LossPass reduces the FCT of small flows while maintaining line-rate throughput. For example, in testbed experiments, LossPass outperforms ECN by up to
$3.20\times$
in the 99th percentile FCT of small flows.