Congestion Control for High-speed Extremely Shallow-buffered Datacenter Networks

Abstract

The link speed in datacenters is growing fast, from 1Gbps to 100Gbps. However, the buffer size of commodity switches increases slowly, thus significantly outpaced by the link speed. In such extremely shallow-buffered datacenter networks, prior TCP/ECN solutions suffer from either excessive packet losses or significant throughput degradation. Motivated by this, we introduce BCC, a simple yet effective solution with only one more configuration (shared buffer ECN/RED) at commodity switches. BCC operates based on real-time shared buffer utilization. When the buffer is abundant, BCC delivers both high throughput and low packet loss rate. When it becomes scarce, BCC triggers shared buffer ECN/RED to prevent packet losses at the cost of sacrificing a small amount of throughput. Our preliminary results show that BCC maintains low packet loss rate persistently while only slightly degrading throughput when the buffer becomes insufficient. Compared to current practice, BCC achieves up to 94.4% lower 99th percentile completion time for small flows while only degrading large flows by up to 2.8%.