Confucius: Adapting Home Routers to Congestion Control's Reactions for Consistent Low Latency

Abstract

Emerging high-quality real-time applications require consistently low latency, which is often disrupted by latency spikes. We identify the reason as the mismatch between the abrupt bandwidth reallocation on routers and gradual sending rate reaction of congestion control. For example, when a burst of new flows arrives, queue schedulers such as fair queueing immediately reallocate the bandwidth for existing and new flows. However, the flow's sending rate, determined by the congestion control algorithm (CCA), needs several RTTs to converge to the new available bandwidth, during which severe stalls occur. This has been increasingly critical with the demand on consistent low latency. In this paper, we present Confucius, a practical queue management scheme that reallocate the bandwidth for flows following CCA's reaction. Confucius slows down bandwidth adjustment to match the reaction of congestion control, so that the end host can reduce the sending rate without overshooting the network. Confucius is designed for offering real-time flows with consistently low latency regardless of uncertain competition. Experiments show that Confucius reduces the stall duration by more than 50% against existing practical schemes, while competing flows also fairly enjoy on-par performance.Available at: https://github.com/hkust-spark/confucius-qdisc