DualPI2 Active Queue Management in ns-3: Implementation And Validation

2026-08-12

AI Summary

This work addresses the lack of a high-fidelity, standards-compliant DualPI2 active queue management (AQM) model in ns-3, which has hindered accurate simulation of coexisting scalable and classic flows under the L4S architecture. We present the first complete implementation of DualPI2 in ns-3 that aligns precisely with the Linux kernel, incorporating key features such as credit-based weighted round-robin (WRR) scheduling, stepwise ECN marking, and overload protection. Rigorously validated across 25 bandwidth-delay product scenarios, our implementation demonstrates close agreement with physical testbed measurements, effectively ensuring throughput fairness and queue delay isolation. This contribution fills a critical gap in high-fidelity simulation tools for L4S networks.

Abstract

The demand for ultra-low latency applications necessitates advanced network architectures like the Low Latency, Low Loss, and Scalable Throughput (L4S) standard. A core component of L4S is the DualPI2 Active Queue Management (AQM), which ensures the safe coexistence of scalable and classic traffic. Despite L4S's growing adoption, the ns-3 network simulator lacks a high-fidelity, up-to-date DualPI2 model. This paper presents a comprehensive implementation of the DualPI2 AQM in ns-3, while also mirroring the official Linux Kernel architecture. Our model incorporates representative mechanisms previously absent in simulation, such as credit-based Weighted Round Robin (WRR) scheduling, step-marking, and overload protection. To guarantee simulation accuracy, we validate our implementation against a physical Linux testbed across 25 diverse Bandwidth-Delay Product (BDP) scenarios. Results demonstrate that our ns-3 model replicates real-world behavior, ensuring strict throughput fairness and queue delay isolation. Ultimately, this validated model equips the research community with a robust tool to evaluate and advance L4S performance across diverse network topologies, ranging from data centers to wireless home and office environments.

Problem

• DualPI2
• Active Queue Management
• L4S
• ns-3
• network simulation

Innovation

• DualPI2
• Active Queue Management
• L4S
• ns-3 simulation
• step-marking