DNS on Windows Server 2003, 3rd Edition

Top-Level Domains

The original top-level domains divided the Internet domain namespace organizationally into seven domains:

com

Commercial organizations, such as Hewlett-Packard (hp.com), Sun Microsystems (sun.com), and IBM (ibm.com).

edu

Educational organizations, such as U.C. Berkeley (berkeley.edu) and Purdue University (purdue.edu).

gov

Government organizations, such as NASA (nasa.gov) and the National Science Foundation (nsf.gov).

mil

Military organizations, such as the U.S. Army (army.mil) and Navy (navy.mil).

net

Formerly organizations providing network infrastructure, such as NSFNET (nsf.net) and UUNET (uu.net). Since 1996, however, net has been open to any commercial organization, like com is.

org

Formerly noncommercial organizations, such as the Electronic Frontier Foundation (eff.org). Like net, though, restrictions on org were removed in 1996.

int

International organizations, such as NATO (nato.int).

Another top-level domain called arpa was originally used during the ARPAnet’s transition from host tables to DNS. All ARPAnet hosts originally had hostnames under arpa so they were easy to find. Later, they moved into various subdomains of the organizational top-level domains. However, the arpa domain remains in use in a way you’ll read about later.

You may notice a certain nationalistic prejudice in our examples: we’ve used primarily U.S.-based organizations. That’s easier to understand—and forgive—when you remember that the Internet began as the ARPAnet, a U.S.-funded research ...