4. Border Gateway Protocol (BGP): a few reminders

4.1 BGP

The BGP protocol is the routing protocol used on the Internet to exchange routes between Autonomous Systems (AS). Typically, the Internet is broken down into tens of thousands of autonomous systems, each of which is operated by a specific administrative entity, typically a network operator.

BGP is also used for intra-operator purposes, such as exchanging routes between access and core infrastructures. The establishment of BGP sessions within an AS is in any case necessary to guarantee the consistency of the AS graphs maintained by each of the routers in the domain.