8.8 Connecting to the Internet
8.8.4 ISPs and Internet backbone providers
Services of an Internet Service Provider (ISP) are required in order to surf the Internet. An ISP is a company that connects computers to the Internet and World Wide Web. The actual connection to the Internet is tiered. This means that the ISP may link to a larger regional ISP, which in turn might connect to one of a number of nationwide computer centers. Therefore, by just sitting in front of a computer and browsing the Internet, one can benefit from hundreds or even thousands of computers that are networked. This enables access to all kinds of documents, music downloads, and videos from all over the world.

When connecting to an ISP, the computer becomes a remote client on the ISP local network. It is amazing how far the Internet has gone towards turning the entire world into one "global village". At the onset of the Internet era, a local computer or LAN had to have a direct connection to the Internet backbone, which was not affordable for individuals and smaller companies. Now, new technologies have led to easier and cheaper ways of building networks. ISPs now play a critical role in providing Internet access to most homes and businesses in this country. ISPs use the more expensive and complex equipment to establish a Point of Presence (POP), or access point, on the Internet. They either lease the dedicated high-speed lines from a telephone company or, in the case of large ISPs, actually install their own lines. Note that a very small, local ISP may not link directly to the Internet backbone. Instead, the small ISP might actually go through a larger regional ISP that is directly connected. Not all ISPs are created equal.

Internet Infrastructure Example
The current U.S. Internet infrastructure consists of a commercial backbone and a high-speed service known as the Very High-Speed Backbone Network Service (vBNS). The vBNS connects five supercomputer networks across the country and is used for scientific purposes. The commercial backbone is basically an internetwork of commercially operated networks. In the United States, for example, there are several companies that provide the commercial backbone:

  • UUNET - a division of WorldCom
  • Cable & Wireless USA
  • Sprint
  • AT&T
  • BBN Planet

ISPs connect to the commercial networks. Usually the backbone, providers, and ISPs enter into agreements (called peering agreements) that allow them to carry each other's network traffic. In the United States, much of the physical cabling is still owned by the Regional Bell Operating Companies (RBOCs). They then lease it out to the providers. The provider networks connect with T1, T3, OC-3 lines (North America) or E1 lines (Europe and the most other parts of the world).

The ISP that cannot connect directly to the national backbone is charged a fee to connect to a regional provider that links to the national backbone through a Network Access Point (NAP). A NAP, which provides data switching, is the point at which access providers are interconnected. However, not all the Internet traffic goes through NAPs. Some ISPs that are in the same geographic area make their own interconnections and peering agreements. A Metropolitan Area Exchange (MAE) is the point where ISPs connect to each other and traffic is switched between them. MAE EAST (located in the Washington D.C. area) and MAE WEST (located in Silicon Valley, California) are the first tier MAEs in the United States.

In other countries or regions of the world where the Internet infrastructure has fully developed and matured, the structural organization is similar to that of the United States. However, for smaller regions or countries having a smaller or developing infrastructure, there are fewer access layers than the United States.