Support ECN in Multi-Queue Datacenter Networks via Per-Port Marking with Selective Blindness

ECN is a powerful tool that can achieve low latency and high throughput simultaneously. Support ECN for multiqueue scenarios is an industry trend in datacenter networks. However, ECN schemes developed for per-port marking cannot be applied directly to the multi-queue scenarios. It hurts at least one metric among latency, throughput, and the scheduling policy. State-of-the-art multi-queue ECN marking schemes each has its own limitations. In this paper, we present per-Port Marking with Selective Blindness (PMSB). The intuition is that: if a flow is found to be a victim of per-port marking, we can either revoke the marking or cancel the flow back-off even if its packets qualify the per-port threshold (i.e., selective blindness). By breaking the fixed causal relationship between ECN marking and flow backoff, flows from un-congested queues can be protected. We evaluate PMSB with large-scale NS-3 simulations. Our results demonstrate that PMSB can preserve a given scheduling policy. Compared with the current practice, PMSB can reduce the average/99% completion time for small flows by 64.49%/72.89% respectively while delivering a slightly better performance for large flows.