ABSTRACT
The Border Gateway Protocol (BGP) is the primary Exterior Gateway Protocol (EGP) used in today’s internetworks for distributing routing information between autonomous systems while enforcing policy decisions, and guaranteeing loop-free exchange of routing information. Each route in a BGP is described by a network IP address prefix, a list of autonomous systems the routing information has passed through (also called the autonomous system path), and a variable list of path attributes. An autonomous system represents a group of routers and network address prefixes that share a common routing policy and are managed by a single administrative entity. The autonomous system may run a single or multiple Interior Gateway Protocols (IGPs) but the entire autonomous system is viewed by the outside world as a single entity.
