DNS on Windows Server 2003, 3rd Edition

Further Down

Within these top-level domains, the traditions and the extent to which they are followed vary. Some of the ISO 3166 top-level domains closely follow the U.S.’s original organizational scheme. For example, Australia’s top-level domain, au, has subdomains such as edu.au and com.au. Some other ISO 3166 top-level domains follow the uk domain’s lead and have organizationally oriented subdomains such as co.uk for corporations and ac.uk for the academic community. In most cases, however, even these geographically oriented top-level domains are divided up organizationally.

That wasn’t originally true of the us top-level domain, though. In the beginning, the us domain had 50 subdomains that correspond to—guess what?—the 50 U.S. states.^[5] Each was named according to the standard two-letter abbreviation for the state—the same abbreviation standardized by the U.S. Postal Service. Within each state’s domain, the organization was still largely geographical: most subdomains corresponded to individual cities. Beneath the cities, the subdomains usually corresponded to individual hosts.

As with so many namespace rules, though, this structure was abandoned when a new company, Neustar, began managing us in 2002. Now us—like com and net—is open to all comers.

^[5] Actually, there are a few more domains under us: one for Washington, D.C., one for Guam, and so on.