BGP

BGP (Border Gateway Protocol) is a standardized exterior gateway protocol used to exchange routing information between different autonomous systems (AS) on the internet. An autonomous system is a collection of IP networks and routers under the control of a single organization that shares a common routing policy. BGP is fundamental to the operation of the global internet, enabling the routing of data across different networks and ensuring that traffic reaches its correct destination.

BGP is classified as a path vector protocol and is designed to be highly scalable, supporting the complex routing requirements of large networks such as the internet. It operates at the application layer and is responsible for determining the most efficient path for data based on a variety of factors, including network policies, path attributes, and the number of hops. BGP makes decisions based on the AS path, which is a list of ASes that a particular route has traversed.

There are two main types of BGP:

• eBGP (External BGP): Used for routing between different autonomous systems. This is the type of BGP that operates between internet service providers (ISPs) or large networks.
• iBGP (Internal BGP): Used within an autonomous system to ensure that all routers within the same AS have consistent routing information.

BGP is also used to enforce policies for traffic routing, allowing network operators to control the flow of data based on various criteria such as cost, performance, or reliability. The protocol’s ability to handle complex and large-scale routing makes it an essential part of the infrastructure that keeps the internet functioning.

Because of its importance in global routing and its role in internet stability, BGP must be carefully managed to avoid issues like route hijacking or misconfigurations that could lead to traffic diversion or network outages.