Thus now you know how packets travel from one computer to another computer over the Internet. however what's in-between? What in fact makes up the Internet infrastructure or backbone?

Figure : Internet Backbone

The Internet backbone is made up of many large networks, which interconnect with each other. These large networks are known as Network Service Providers or NSPs. These networks peer with each other to exchange packet traffic. Each of the NSP is needed to link to Network Access Points or NAPs. At the NAPs, packet traffic might jump from one NSP's backbone to another. NSPs interconnect also at Metropolitan Area Exchanges or MAEs. MAEs serve the same reason as the NAPs however are privately owned. NAPs were the original Internet interconnects points. Both NAPs & MAEs are referred to as Internet Exchange Points or IXs. NSPs also sell bandwidth to smaller networks, like ISPs & smaller bandwidth providers. Below is a picture illustrating this hierarchical infrastructure.

It is not a true representation of real piece of the Internet. The above figure is meant to demonstrate only how the NSPs could interconnect to each other and smaller ISPs. None of the physical network components are illustrated in this figure. It is because a single NSP's backbone infrastructure is a complicated drawing by itself.

Most of the NSPs publish maps of their network infrastructure on their web sites & can be easily found. To draw an real map of the Internet would be closely impossible because of it's size, complexity, and ever changing structure.