Congestion Control for Datacenter Networks: A Control-Theoretic Approach

In this article, we present RoCC , a robust congestion control approach for datacenter networks based on RDMA. RoCC leverages switch queue size as an input to a PI controller, which computes the fair data rate of flows in the queue. The PI parameters are self-tuning to guarantee stability, rapid convergence, and fair and near-optimal throughput in a wide range of congestion scenarios. Our simulation and DPDK implementation results show that RoCC can achieve up to $7\times$ reduction in PFC frames generated under high load levels, compared to DCQCN. At the same time, RoCC can achieve $1.7-4.5\times$ and $1.4-3.9\times$ lower tail latency for long flows and $2.1-7\times$ and $3.5-8.2\times$ lower tail latency for short flows, compared to DCQCN and HPCC, respectively. We also find that RoCC does not require PFC. The functional components of RoCC can be efficiently implemented in P4 and FPGA-based switch hardware.