BGP Explained with analogy (Post office)

The Border Gateway Protocol (BGP) is a crucial part of the Internet’s routing infrastructure, responsible for exchanging information between different networks, known as Autonomous Systems (ASes). To explain BGP with an analogy, let’s imagine the Internet as a large, complex city with many neighborhoods, and BGP as the postal service responsible for delivering mail between these neighborhoods.

First let’s figure out the terminologies in BGP.

Autonomous Systems (ASes): The neighborhoods in our city. Each neighborhood has its own internal road network and traffic rules. In the Internet, ASes are large networks operated by organizations like Internet Service Providers (ISPs), universities, or large companies.

BGP routers: The post offices in each neighborhood. They’re responsible for receiving and forwarding mail to other post offices in their neighborhood or other neighbourhoods.

BGP messages: The letters exchanged between post offices. These messages communicate routing information, which helps post offices decide how to send mail to different neighborhoods.

Prefixes: The street addresses on the envelopes. In the Internet, prefixes represent blocks of IP addresses assigned to different ASes.

BGP peering: The agreement between two post offices to exchange mail. In the Internet, BGP routers establish connections with each other to exchange routing information.