Nimble: Scalable TCP-Friendly Programmable In-Network Rate-Limiting

ABSTRACTThere is an emerging need for scalable high-performance in-networkrate-limiting because rate-limiters can be used to provide performance isolation. However, existing approaches to in-network rate-limiting are not scalable or TCP-friendly. This paper presents the design of Nimble, a new approach to in-network rate-limiting that is scalable, high performance, and TCP-friendly. Nimble uses meters to scalably provide hardware rate-limiting without any dedicated queuing or buffering resources, and Nimble uses ECN-Shaping for TCP-friendly rate-limit enforcement. Nimble also introduces the first algorithm for configuring in-network rate-limiters to enforce network-wide isolation policies. Through a P4 implementation and experiments with a 100Gbps Barefoot Tofino switch, we find that Nimble is immediately usable and can operate even with high bandwidth rate-limits without needing to recirculate packets or rely on hardware packet generators to generate token refill packets. This overcomes the scalability limitations of prior approaches. Experiments with Apache and Redis show that Nimble can reduce application-level latency by an order of magnitude when compared to not using in-network rate-limiting, and ns-3 simulations demonstrate that Nimble behaves well in larger clusters. We find that Nimble can scale to 100K rate-limiters perswitch when implemented on a Barefoot Tofino switch, and our new rate allocation algorithm reduces rate-limiter updates by a factor of 10x-24x and improves network utilization by 24%.