How a Tiny Error Caused Internet Outages Across the US

The misconfiguration was a “route leak,” according to Roland Dobbins, a principal engineer at the DDoS and network-security firm Arbor Networks, which monitors global internet operations. ISPs use “Autonomous Systems,” also known as ASes, to keep track of what IP addresses are on which networks, and route packets of data between them. They use the Border Gateway Protocol (BGP) to establish and communicate routes. For example, packets can route between networks A and B, but network A can also route packets to network C through network B, and so on. This is how internet service providers interoperate to let you browse the whole internet, not just the IP addresses on their own networks. – Lily Hay Newman, WIRED