OBF-SFP: Service-Rate Based AQM with BDP Gating and Stochastic Binning for BBR-CUBIC Fairness in Single-Queue Networks

Abstract

Fairness between model-based TCP BBR and loss-based TCP CUBIC remains difficult when both protocols share a dynamic single bottleneck. This paper proposes OBF-SFP, a lightweight single-queue AQM mechanism that combines stochastic virtual binning, dequeue-rate shadow accounting, BDPgated activation, persistence scoring, and probabilistic penalties to reduce persistent service-share dominance. Unlike per-flow queueing, OBF-SFP estimates dominance through virtual-bin service shares while maintaining $O(1)$ per-packet processing and $O(N)$ memory cost. Evaluation in ns-3.42 uses a dynamic dumbbell topology, 2, 4, and 8 competing flows, and five random seeds. Results show that DropTail, CoDel, and PIE allow strong BBR dominance in the 8-flow case, with BBR shares around 0.889-0.892 and JFI around 0.619-0.623. OBF-SFP reduces the BBR share to 0.554 and improves JFI to 0.988, approaching FQ-CoDel fairness while retaining a single-queue design. The improvement comes with a measurable BBR-side loss trade-off, indicating that further loss reduction and ECN-capable validation remain important directions for future work.