PABO: A Link-Layer Congestion Mitigation Mechanism Based on Packet Bounce.

In today's data center, a diverse mix of throughput-sensitive long flows anddelay-sensitive short flows are commonly presented in shallow-bufferedswitches. Long flows could potentially block the transmission ofdelay-sensitive short flows, leading to degraded performance. Congestion canalso be caused by the synchronization of multiple TCP connections for shortflows, as typically seen in the partition/aggregate traffic pattern. Whilemultiple end-to-end transport-layer solutions have been proposed, none of themhave tackled the real challenge: reliable transmission in the network. In thispaper, we fill this gap by presenting PABO -- a novel link-layer design thatcan mitigate congestion by temporarily bouncing packets to upstream switches.PABO's design fulfills the following goals: i) providing per-flow based flowcontrol on the link layer, ii) handling transient congestion without theintervention of end devices, and iii) gradually back propagating the congestionsignal to the source when the network is not capable to handle thecongestion.Experiment results show that PABO can provide prominent advantage ofmitigating transient congestions and can achieve significant gain on end-to-enddelay.