BigPi: Sharing Link Pools in Cloud Networks

In cloud networks, sharing network resources among different VMs is critical to performance isolation. A sharing scheme aims to fully utilize the network resource, and effectively prevent performance interference and even malicious attacks such as Denial-of-Service (DoS) attacks. Existing bandwidth allocation schemes like Seawall attempt to achieve performance isolation on a per-link basis. However, due to unbalanced congestion created by single-path routes, that level of isolation is suboptimal for multi-rooted trees widely used in todays datacenters. In BigPi, we define a link pool as a set of parallel links from the same rack or pod, and find that if we evenly split each flow into all paths, we can share the bandwidth on the per-link-pool basis. Sharing at the granularity of link pools achieves higher network utilization and per-source fairness, by leveraging all potential paths. Through rigorous analysis and extensive simulation, we show that BigPi is highly scalable, and achieves both stronger isolation and higher overall throughput than that feasible when sharing at a per-link basis. In addition, within a VM, BigPi’s bandwidth allocation achieves higher tail throughput.