Border Gateway Protocol (BGP)

BGP is the de facto standard routing protocol for interconnecting autonomous systems (ASs) on the Internet. Since its introduction in 1989, BGP has scaled the Internet to millions of routers and trillions of destinations. BGP is path-vector-based, using a flexible policy system to control route propagation and selection. While BGP convergence can be slow and policies complex, it remains the only viable protocol for Internet-scale inter-domain routing.