Better Never than Late: Meeting Deadlines in Datacenter Networks
The soft real-time nature of large scale web applications in today's datacenters, combined with their distributed work- flow, leads to deadlines being associated with the datacenter application traffic. A network flow is useful, and contributes to application throughput and operator revenue if, and only if, it completes within its deadline. Today's transport pro- tocols (TCP included), given their Internet origins, are ag- nostic to such flow deadlines. Instead, they strive to share network resources fairly. We show that this can hurt appli- cation performance. Motivated by these observations, and other (previously known) deficiencies of TCP in the datacenter environment, this paper presents the design and implementation of D3, a deadline-aware control protocol that is customized for the datacenter environment. D3 uses explicit rate control to apportion bandwidth according to flow deadlines. Evalua- tion from a 19-node, two-tier datacenter testbed shows that D3, even without any deadline information, easily outper- forms TCP in terms of short flow latency and burst toler- ance. Further, by utilizing deadline information, D3 effec- tively doubles the peak load that the datacenter network can support.