Don't drop, detour!

Abstract

Today's data centers must support a range of workloads with different demands. While existing approaches handle routine traffic smoothly, ephemeral but intense hotspots cause excessive packet loss and severely degrade performance. This loss occurs even though the congestion is typically highly localized, with spare buffer capacity available at nearby switches. We argue that switches should share buffer capacity to effectively handle this spot congestion without the latency or monetary hit of deploying large buffers at individual switches. We present detour-induced buffer sharing (DIBS), a mechanism that achieves a near lossless network without requiring additional buffers. Using DIBS, a congested switch detours packets randomly to neighboring switches to avoid dropping the packets. We implement DIBS in hardware, on software routers in a testbed, and in simulation, and we demonstrate that it reduces the 99th percentile of query completion time by 85%, with very little impact on background traffic.