TCP BBR Performance over Wi-Fi~6: AQM Impacts and Cross-Layer Insights

TL;DR

This paper evaluates TCP BBRv3 performance over Wi-Fi 6, analyzing how different AQM schemes affect its stability, latency, and fairness, providing practical guidance for optimizing Wi-Fi networks.

Contribution

It offers new insights into the interaction between TCP BBRv3, Wi-Fi 6, and AQM schemes, highlighting the benefits of FQ-CoDel and CAKE over FIFO in home Wi-Fi environments.

Findings

FQ-CoDel restores fairness and controls latency in Wi-Fi 6 with BBRv3.

CAKE delivers the best overall performance by maintaining low delay and aligning rates.

FIFO destabilizes pacing and increases delay, often letting CUBIC dominate.

Abstract

We evaluate TCP BBRv3 on Wi-Fi 6 home networks under modern AQM schemes using a fully wireless testbed and a simple cross-layer model linking Wi-Fi scheduling, router queueing, and BBRv3's pacing dynamics. Comparing BBR Internet traffic with CUBIC across different AQMs (FIFO, FQ-CoDel, and CAKE) for uplink, downlink, and bidirectional traffic, we find that FIFO destabilizes pacing and raises delay, often letting CUBIC dominate; FQ-CoDel restores fairness and controls latency; and CAKE delivers the best overall performance by keeping delay low and aligning BBRv3's sending and delivered rates. We also identify a Wi-Fi-specific effect where CAKE's rapid queue draining, while improving pacing alignment, can trigger brief retransmission bursts during BBRv3's bandwidth probes. These results follow from the interaction of variable Wi-Fi service rates, AQM delay control, and BBRv3's inflight limits, leading to practical guidance to use FQ-CoDel or CAKE and avoid unmanaged FIFO in home Wi-Fi, with potential for Wi-Fi-aware tuning of BBRv3's probing.