The internet doesn’t have a map. Individual routers exchange information about reachability using protocols — RIP, OSPF, BGP — and build their own local picture of the network topology, forwarding packets based on whatever their current table says. BGP, the Border Gateway Protocol, handles routing between autonomous systems — the large networks operated by ISPs, cloud providers, and major institutions — and is held together partly by technical mechanisms and partly by the cooperative goodwill of network operators who have agreed not to announce routes they don’t own. This agreement is honoured imperfectly: BGP route hijacking events, in which a network accidentally or deliberately announces routes for addresses it doesn’t control, redirect significant chunks of internet traffic with some regularity. In 2010, a Chinese ISP briefly announced routes that redirected about 15% of global internet traffic through its network. For eighteen minutes, a substantial portion of the internet took an unscheduled detour through Beijing.
