Internet Backbones

The LANs and WANs that make up the Internet are connected to the Internet backbone. Some backbones are regional, connecting towns and cities in a region such as southern California or New England. Others are continental, or even transcontinental, in scope. Whatever their scope, backbones are designed to carry huge amounts of data traffic. Cross-country Internet backbones, for example, can handle nearly 5.5GBps, and much higher speeds are on the way. A current federally funded research project is constructing a backbone network that will operate at speeds of 17GBps to 18.4GBps. To understand how data travel over a WAN, it helps to understand how data travel over the Internet. This journey can be compared with an interstate car trip. When you connect to the Internet and request access to a Web page, your request travels by local connections-the city streets-to your ISP’s local POP. From there, your ISP relays your request to the regional backbone-a high-way. Your request then goes to network access point-highway on-ramp-where regional backbones connects with national backbone networks. And from there, the message gets on the national backbone network-the interstate. When your request nears its destination, your message gets off the national backbone network and travels regional and local networks until it reaches its destination.