A DualPI2 Module for Mahimahi: Behavioral Characterization and Cross-Platform Analysis

2026-03-04

AI Summary

This work addresses behavioral inconsistencies between Linux kernel implementations and userspace simulators of the L4S (Low Latency, Low Loss, Scalable throughput) mechanism, which hinder experimental reproducibility and parameter portability. We present the first scalable implementation of the DualPI2 active queue management algorithm in Mahimahi and conduct a systematic comparison against its kernel counterpart across diverse traffic patterns and network conditions. Through comprehensive behavioral characterization and parameter sensitivity analysis, we identify the bandwidth-delay product (BDP) as a critical factor governing cross-platform discrepancies. Our findings reveal specific parameter configurations that improve alignment under low-BDP scenarios, while also exposing persistent structural deviations under high load. This study provides both a practical simulation tool and empirical guidance for accurate L4S experimentation and deployment.

Technology Category

• Multiagent Systems: Agent-Based Simulation and Emergent Behavior
• Search and Optimization: Sampling/Simulation-based Search
• Planning, Routing, and Scheduling: Plan Execution and Monitoring

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: User modeling and simulation for interactive and conversational systems

Abstract

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.

Problem

• DualPI2
• L4S
• cross-platform analysis
• active queue management
• behavioral characterization

Innovation

• DualPI2
• Mahimahi
• L4S
• cross-platform analysis
• active queue management