What Is BGP? A Developer-Friendly Guide to Internet Routing

The Border Gateway Protocol (BGP) is the routing protocol that makes the internet a network of networks. It exchanges route information between Autonomous Systems (AS).

Core ideas

• ASN — Autonomous System Number identifies a network
• Prefixes — blocks of IPs announced via BGP
• Path selection — BGP chooses routes based on policies, path length, and attributes

Operators must secure BGP with RPKI and filtering to reduce the risk of hijacks.