Low-complexity Flow Scheduling for Commodity Switches in Data Center Networks

Recently proposed approaches to minimize the Flow Completion Time (FCT) in data centers do not require any apriory information about the flow size, thus appearing to be both practical and efficient. These solutions are based on a system of multiple priority queues (PQs) at both the servers and theswitches and they may require to solve a complex algorithm to optimally split the traffic across the different PQs. However, the actual availability of priority queues at the switches is typically limited, thus restricting the applicability of these approaches. In this paper, we propose a novel approach, named NOS2, which requires only 2 PQs at the switches while maintaining multiple PQs at the servers, and leverages a central controller that optimally coordinates the traffic split among the different priority levels. We show by simulation that NOS2 is able to achieve performance close to state-of-art solutions with significantly smaller implementation complexity. Thus, NOS2 is expected to provide a better trade-off between performance and implementation complexity.