tional ISPs that have a national presence and connect to at least three of the original four NAPs. National ISPs include AT&T, Cable & Wireless, MCI, and Sprint. Tier 2 refers to regional ISPs, which primarily have a regional presence and connect to Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Transport Technologies Chapter 7 less than three of the original four NAPs. Regional ISPs include Adel- phia.net, Verizon.net, and BellSouth.net. Finally, Tier 3 refers to local ISPs, or those that do not connect to a NAP but offer services via the con- nections of another ISP. Managing the Internet The Internet is really a network of networks, all interconnected by high- bandwidth circuits leased (for the most part) from various telephone com- panies. It is something of an erroneous conclusion to think of the Internet as a stand-alone network; in fact, it is made up of the same network com- ponents that make up corporate networks and public telephone networks. It's just a collection of leased lines that interconnect the routers that pro- vide the sophisticated routing functions that make the Internet SO pow- erful. As such, it is owned by no one and owned by everyone, but more importantly it is managed by no one and managed by everyone! There is no single authority that governs the Internet, because the Internet is not a single monolithic entity but rather a collection of entities. Yet, it runs well, perhaps better than other more centrally managed services! That being said, there are certainly a number of organizations that provide oversight, guidance, and a certain degree of management for the Internet community. These organizations, described in some detail in this section, help to guide the developmental direction of the Internet with regard to such functions as communications standards, universal addressing systems, domain naming, protocol evol