Border Gateway Protocol

The last important protocol we'll discuss is BGP, BGP is basically how the Internet runs. It's used to collect and exchange routing information among autonomous systems. Think of an autonomous system as an Internet service provider, a company, university, any organization, etc. Without BGP, these systems would not know how to talk to each other, they would just be siloed off. Instead of routing inside these autonomous systems, BGP routes between them.

Let's say you were on your home network and I'm working from Starbucks, I want to be able to communicate with you, so I send an email and the network packet travels through Starbuck's network, it bounces around there and goes through the routing tables in Starbuck's network until it finally reaches a point at the border of the Starbucks network and passes it to a Border Gateway router. This router contains the information for my packet to leave the Starbucks network and traverse other networks.

It is worth being honest about the depth here. BGP is the protocol by which every network on the internet tells every other network how to reach it, it runs on trust between operators, and a single mistyped announcement has taken large parts of the internet offline more than once. People spend careers on it. Seven lessons give you the words and the shape of the problem, which is all this course is trying to do. Computer Networks: A Systems Approach is the place to go if the shape of it interested you.