Accurate and Scalable Rate Limiter for RDMA NICs

Rate limiter is required by RDMA NIC (RNIC) to enforce the rate limits calculated by congestion control. RNIC expects the rate limiter to be accurate and scalable: to precisely shape the traffic for numerous flows with minimized resource consumption, thereby mitigating the incasts and congestions and improving the network performance. Previous works, however, fail to meet the performance requirements of RNIC while achieving accuracy and scalability. In this paper, we present Tassel, an accurate and scalable rate limiter for RNICs, including the algorithm and architecture design. Tassel first extends the classical WF2Q + algorithm to support rate limiting in the context of the RNIC scenario. Then Tassel designs a high-precision and resource-friendly rate limiter and integrates it into classical RNIC architecture. Preliminary simulation results show that Tassel precisely enforces the rate limits ranging from 100 Kbps to 100 Gbps among 1 K concurrent flows while the resource consumption is limited.