Description: External BGP, or External Border Gateway Protocol (BGP), refers to BGP sessions established between routers belonging to different autonomous systems (AS). An autonomous system is a set of IP addresses and networks managed by a single entity or organization. BGP is a routing protocol that allows these autonomous systems to exchange information about network accessibility and available routes. This protocol is fundamental to the functioning of the Internet, as it enables different networks to communicate with each other efficiently and reliably. External BGP is characterized by its ability to handle complex routing policies, allowing network administrators to define how routes should be selected and which routes should be preferred. Additionally, BGP uses an attribute system to determine the best route, which includes factors such as path length, local preference, and routing policy. The robustness and flexibility of External BGP make it an essential tool for large-scale network interconnection, ensuring that data is transmitted optimally between different Internet service providers and organizations.
History: BGP was developed in the 1980s as a solution for routing between different autonomous systems on the Internet. The first version, BGP-1, was specified in 1989 by Yakov Rekhter and others. Over the years, BGP has evolved, and the most widely used version today is BGP-4, which was standardized in 1994. This evolution has allowed for improvements in the efficiency and security of routing on the Internet.
Uses: External BGP is primarily used for exchanging routing information between different Internet service providers (ISPs) and organizations. It allows networks to manage their routes efficiently, optimizing traffic and ensuring connectivity. It is also used in implementing specific routing policies, such as selecting preferred routes and managing traffic load.
Examples: An example of External BGP is the connection between two ISPs exchanging routes to ensure their customers can access the Internet efficiently. Another example is the use of External BGP by large companies operating multiple data centers in different geographical locations, allowing for the interconnection of their networks.
