Accurate Congestion Control for RDMA Transfers

High-performance interconnects need congestion control to deal with traffic bursts. In this paper, we propose ACCurate, a congestion control protocol that assigns exact max-min fair rates to flows, without relying on costly per-flow state inside the network. ACCurate keeps the backlogs outside of the network, protects innocent flows, and promptly recovers the flows' rates after congestive episodes. Comparisons with TCP and PAUSE-only RDMA under datacenter-resembling workloads further show that ACCurate provides up to 10× faster flow completion times. ACCurate relies on simple hardware that can be readily implemented inside switches. In our implementation, the additional circuitry needed in a 16×16 switch occupies less than 2% of FPGA resources.