HyLine: a Simple and Practical Flow Scheduling for Commodity Datacenters

TL;DR

HyLine is a simple, hybrid flow scheduling scheme for commodity datacenter networks that effectively balances load and reduces flow completion times without requiring fabric modifications.

Contribution

It introduces a hybrid approach combining centralized and distributed techniques for flow scheduling in multipath datacenter networks, avoiding fabric changes.

Findings

HyLine significantly outperforms existing schemes in simulations.

It reduces average flow completion time by up to 68%.

It lowers 99th percentile FCT by up to 31%.

Abstract

Today's datacenter networks (DCNs) have been built upon multipath topologies where each path contains multiple links. However, flow scheduling schemes proposed to minimize flow completion times (FCT) in DCNs are based on algorithms which are optimum or close-to-optimum only over single link. Moreover, most of these scheduling schemes seek either fully centralized approaches having overhead of communicating to a central entity or fully distributed approaches requiring changes in the fabric. Motivated by these shortcomings, we present HyLine a simple scheduling design for commodity DCNs which is equipped with a joint load-balancing and flow scheduling (path-aware) design exploiting the multipath nature of DCNs. HyLine takes a hybrid approach and uses the global-awareness of centralized and agility of distributed techniques without requiring any changes in the fabric. To that end, it determines a threshold margin identifying flows for which using centralized approach is beneficial. We have shown through extensive ns2 simulations that despite HyLine's simplicity, it significantly outperforms existing schemes and achieves lower average and 99th percentile FCTs. For instance, compared to Qjump-state-of-the-art practical scheme-and pFabric-one of the best performing flow scheduling schemes-HyLine reduces average FCT up to 68% and 31%, respectively, under a production datacenter workload.