Skyline: A Cloud Centric Internet Monitoring Engine

Cloud providers depend on the public Internet to connect tenants and their clients, yet Internet faults are a leading cause of cloud outages: in our organization, more than 60% of network incidents happen in the Internet and account for close to 80% of user-impacting events. Effectively monitoring the Internet is challenging for cloud providers because they lack direct control and visibility into Internet internals. Our key insight is to treat coverage as a first-class goal and decompose the monitoring requirements into three coverage dimensions—traffic direction, incident lifecycle, and tenant granularity—then resolve each independently. We present Skyline, a cloud-centric Internet monitoring system that addresses all coverage dimensions at scale by combining purpose-built dataplane hooks with lightweight software control to minimize resource overhead, shorten reaction time, and preserve non-intrusiveness. Skyline has been deployed for more than two years. In 2025, it identified over 2,000 incidents with very high precision and recall over confirmed issues, thereby significantly improving the reliability of our cloud network.