Airfoil: A Topology Aware Distributed Load Balancing Service

Load balancing is one of the most basic services needed by cloud applications. While today's clouds and load balancers provide highly customizable load distribution policies, they are forced out of necessity to ignore the impact of load balancing on the network. However, such network agnostic behavior can lead to inefficient utilization of cloud resources and poor performance, especially for upcoming network centric applications such as network function virtualization (NFV). But can network topology, a cloud property that is hidden from tenants, be made to effectively influence load balancing, a function that is intimately tied to per-tenant application structure that is largely invisible to the cloud? We answer that question in this paper by presenting Airfoil, a novel topology-aware distributed load balancer as a service (LBaaS) that takes network topology into consideration while providing cloud tenants with application-specific load balancing policies. By finding the best communication pattern with linear programming, the most efficient load balancing strategy is calculated without using any heuristics or approximations. We evaluate Airfoil over a range of scenarios from classical web applications to NFV pipelines, and show that it can decrease the network utilization of the most highly loaded network links by over 50%. For network constrained applications, such reductions imply a doubling of application capacity without any additional infrastructure.