NetHint: White-Box Networking for Multi-Tenant Data Centers

A cloud provider today provides its network resources to its tenants as a black box, such that cloud tenants have little knowledge of the underlying network characteristics. Meanwhile, data-intensive applications have increasingly migrated to the cloud, and these applications have both the ability and the incentive to adapt their data transfer schedules based on the cloud network characteristics. We find that the black-box networking abstraction and the adaptiveness of data-intensive applications together create a mismatch, leading to sub-optimal application performance. This paper explores a white-box approach to resolving this mismatch. We propose NetHint, an interactive mechanism between a cloud tenant and a cloud provider to jointly enhance application performance. With NetHint, the provider provides a hint - an indirect indication of the underlying network characteristics (e.g., link-layer network topologies for a tenant's virtual machines, number of co-locating tenants, network bandwidth utilization), and the tenant's applications then adapt their transfer schedules accordingly. The NetHint design provides abundant network information for cloud tenants to compute their optimal transfer schedules, while introducing little overhead for the cloud provider to collect and expose this information. Evaluation results show that NetHint improves the average performance of allreduce completion time, broadcast completion time, and MapReduce shuffle completion time by 2.7x, 1.5x, and 1.2x, respectively.