Protean: Adaptive Management of Shared-Memory in Datacenter Switches

Datacenters rely on high-bandwidth networks that use inexpensive, shared-buffer switches. The combination of high bandwidth, bursty traffic patterns, and shallow buffers imply that switch buffer is a heavily contended resource and intelligent management of shared buffers among competing traffic (ports, traffic classes) becomes an important challenge. Dynamic Threshold (DT), which is the current state-of-the-art in buffer management, provides either high bandwidth utilization with poor burst absorption or good burst absorption with inferior utilization, but not both. We present Protean, which dynamically identifies bursty traffic and allocates more buffer space accordingly—Protean provides more space to queues that experience transient load spikes by observing the gradient of queue length but does not cause persistent unfairness as the gradient cannot continue to remain high in shallow buffered switches for long periods of time. We implemented Protean in today’s programmable switches and demonstrate their high performance with negligible overhead. Our at-scale ns-3 simulations show that Protean reduces the tail latency by a factor of 5 over DT on average across varying loads with realistic workloads.