“Look, Ma, no probes!” — Characterizing CDNs’ latencies with passive measurement

This post introduces a novel method for passively measuring and predicting CDN latencies. It details a two-step process: first, predicting Anycast catchments by compiling CDN network footprints from various data sources (ISPs, PeeringDB, IXP databases, BGP data) to infer routing paths and data center usage. Second, estimating CDN path latencies by utilizing Cloudflare's own passive RTT measurements as a proxy. This approach aims to overcome the limitations of active measurements by inferring performance characteristics that cannot be directly observed, thereby enabling better understanding of CDN performance and validation of network models.