Border Gateway Protocol (BGP)

The Border Gateway Protocol, or BGP, is the core routing protocol of the internet and governs the exchange of routing information between autonomous systems. BGP operates as a path vector protocol and evaluates routes not only by distance but also by attributes such as AS path, local preference, MED and next hop. This allows traffic paths to be controlled according to both technical and commercial criteria. A distinction is made between external BGP, used between different autonomous systems, and internal BGP, used within a single system. The protocol is deployed by internet service providers, data centres and enterprises connected to multiple providers to achieve resilience and load distribution. BGP runs over TCP port 179. Misconfigurations and route hijacking make filtering, prefix lists and RPKI important safeguards.