Gone offline: how Cloudflare Radar detects Internet outages

What this post added

This post details the technical approach to detecting Internet outages and traffic anomalies for Cloudflare Radar. It introduces a new system for automatically identifying anomalous traffic events (primarily traffic drops) across countries and Autonomous Systems (ASes). The system uses time-series analysis of various data sources (DNS, HTTP, NetFlows, NEL) to detect deviations from expected patterns. It outlines the process of verifying these anomalies, categorizing them as 'Verified' or 'False Positive', and the challenges of modeling diverse traffic patterns, including seasonality, trends, and external events like holidays. The post also discusses the criteria for selecting entities for anomaly detection based on traffic signal strength.