Aletheia: A Lightweight Tool for WiFi Medium Analysis on the Edge

With the plethora of wireless devices in limited spaces running multiple WiFi standards (802.11 a/b/g/n/ac), gaining an understanding of network latency, loss, and medium utilization becomes extremely challenging. Microsecond timing fidelity with protocols is critical for network performance evaluation and design; such fine-grained timing offers insights that simulations cannot deliver (e.g., precise timing through hardware and software implementations). However, currently there is no suitable efficient, lightweight tool for such purposes. This paper introduces Aletheia, an open-source tool that enables users to select their interested attributes in WiFi frames, quantify and visualize microsecond granularity medium utilization using low-cost commodity edge devices for easy deployment. Aletheia uses selective attribute extraction to filter frame fields; it reduces data storage and CPU overhead by 1 and 2 orders of magnitude, respectively, compared to existing tools (e.g., Wireshark, tshark). It provides flexible tagging and visualization features to examine the medium and perform different analysis to understand protocol behavior under different environments. We use Aletheia to capture and analyze 120M frames in 24 hours at 4 locations to demonstrate its value in production and research network performance evaluation and troubleshooting. We find that WiFi management beacons can consume medium heavily (up to 40%); the common practice of categorizing networks based on environment types (e.g., office vs. home) is problematic, calling for a different evaluation methodology and new designs.