Fair Work-Conserving Bandwidth Guarantees in Datacenters Using MPTCP

Datacenters should provide bandwidth guarantees to tenants for performance predictability. Ideally, this process should attain three important characteristics: work conservation, fairness, and simplicity. The first one indicates that tenants can utilize unused bandwidths effectively without harming the bandwidth guarantee. The second one means that tenants share the unused bandwidth following a certain fairness policy. The last one requires that the developed scheme can be easily deployed with commodity software and hardware. However, achieving all requirements at the same time is challenging considering the distributed nature of bandwidth usage in datacenters. In this paper, we present our practical approach that can solve the aforementioned challenges using multipath TCP (MPTCP). With MPTCP, we split each TCP flow into one bandwidth guarantee (BG) subflow and one work conservation (WC) subflow. We treat all BG subflows and UDP flows as BG traffic and WC subflows as WC traffic. We let BG traffic go through a high priority queue on switches to guarantee allocated bandwidth. WC traffic goes through a low priority queue to grab unused bandwidths without harming bandwidth guarantee. We tune the aggressiveness of WC subflows to achieve the fairness policy. The overall scheme can be easily deployed on commodity servers and switches. We implement our approach along with the Linux kernel MPTCP implementation. Extensive testbed experiments show that our scheme achieves all the three goals with design simplicity compared to prior work.