Confucius: Achieving Consistent Low Latency with Practical Queue Management for Real-Time Communications

Abstract

Real-time communication applications require consistently low latency, which is often disrupted by latency spikes caused by competing flows, especially Web traffic. We identify the root cause of disruptions in such cases as the mismatch between the abrupt bandwidth allocation adjustment of queue scheduling and gradual congestion window adjustment of congestion control. For example, when a sudden burst of new Web flows arrives, queue schedulers abruptly shift bandwidth away from the existing real-time flow(s). The real-time flow will need several RTTs to converge to the new available bandwidth, during which severe stalls occur. In this paper, we present Confucius, a practical queue management scheme designed for offering real-time traffic with consistently low latency regardless of competing flows. Confucius slows down bandwidth adjustment to match the reaction of congestion control, such that the end host can reduce the sending rate without incurring latency spikes. Importantly, Confucius does not require the collaboration of end-hosts (e.g., labels on packets), nor manual parameter tuning to achieve good performance. Extensive experiments show that Confucius outperforms existing practical queueing schemes by reducing the stall duration by more than 50%, while the competing flows also fairly enjoy on-par performance.