Low Latency, Low Loss, and Scalable Throughput (L4S) is an emerging paradigm for latency control based on DualPI2 active queue management and scalable congestion control. While a Linux kernel implementation of DualPI2 is available, controlled and reproducible experimentation on L4S mechanisms can be facilitated by a modular, user-space alternative. In this paper, we present a DualPI2 module for the Mahimahi network emulator, designed to support extensible, component-level experimentation without kernel modification. We conduct a statistical behavioral characterization of the Mahimahi implementation by examining key metrics across diverse traffic patterns and network conditions, using the Linux kernel implementation as a reference baseline. Our analysis shows that behavioral alignment across execution environments is not automatic: identical DualPI2 parameterization does not guarantee identical dynamics. Instead, key control parameters exhibit environment-dependent sensitivity, leading to regime-dependent discrepancies across bandwidth-delay product (BDP) conditions. Through targeted parameter exploration, we identify configurations that improve cross-platform alignment in low BDP regimes, while revealing structural differences that persist under higher load. This work provides both a practical tool for experimental L4S research and empirical insight into cross-platform behavioral differences, highlighting the importance of systematic characterization and environment-aware parameter selection in emulation-based AQM studies.

翻译：低延迟、低丢包与可扩展吞吐量（L4S）是一种基于DualPI2主动队列管理和可扩展拥塞控制的新兴延迟控制范式。虽然Linux内核已提供DualPI2实现，但通过模块化的用户空间替代方案可以促进对L4S机制的可控且可复现的实验研究。本文提出面向Mahimahi网络仿真器的DualPI2模块，该模块无需修改内核即可支持可扩展的组件级实验。我们以Linux内核实现为参考基准，通过考察不同流量模式与网络条件下的关键指标，对Mahimahi实现进行了统计行为表征。分析表明：跨执行环境的行为一致性并非自动达成——相同的DualPI2参数配置并不能保证相同的动态特性。关键控制参数表现出环境依赖性敏感度，导致在带宽延迟积（BDP）条件变化时出现机制依赖的差异。通过定向参数探索，我们确定了在低BDP区间能改善跨平台一致性的配置方案，同时揭示了在高负载条件下持续存在的结构差异。本研究不仅为实验性L4S研究提供了实用工具，还通过实证揭示了跨平台行为差异，强调了在基于仿真的AQM研究中系统化表征与环境感知参数选择的重要性。