BGP (Border Gateway Protocol) is the internet's routing protocol — routing between autonomous systems (AS). Uses path vector routing with AS-path attribute to prevent loops.
BGP is the protocol that makes the internet work. BGP hijacking = advertising routes you don't own → traffic misdirection. RPKI (Resource Public Key Infrastructure) adds cryptographic validation to BGP route origins. Default route: 0.0.0.0/0 in BGP.