chieve interoperability; and finally, the Forum of Incident Response and Security Teams, which coor- dinates CERTs in various countries. Together these organizations ensure that the Internet operates as a single, coordinated "organism." Remarkable, isn't it? The least managed network in the world (and arguably the largest) is also the best run! Naming Conventions on the Internet The Internet is based on a system of domains, that is, a hierarchy of names that uniquely identify the "operating regions" on the Internet. For example, "IBM.com" is a domain, as are "Verizon.net," "fcc.gov," and "ShepardComm.com." The domains help to guide traffic from one user to another by following a hierarchical addressing scheme that includes a top-level domain, one or more subdomains, and a host name. The postal service relies on a hierarchical addressing scheme, and it serves as a good analogy to understand how Internet addressing works. Consider the following address: John Hardy 1237 Sunnyside Court Matanuska, Alaska In reality the address is upside down because a package addressed to John must be read from the bottom-up if it is to be delivered properly. 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 Let's assume that the package was mailed from Zemlya Graham Bell² in Franz Josef Land. To begin the routing process, the postal service will start at the bottom with USA, which narrows it down to a country. They will then go to Alaska, then on to Matanuska, then to the address in Matanuska, and finally to John. Messages routed through the Internet are handled in much the same way; routing arbiters deliver them first to a domain, then to a subdomain, then on to a hostname, where they are ultimately delivered to the proper account. The assignment of Internet IP addresses was historically handled by the Internet Assigned Numbers A