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DNS Hierarchy 553
27
net
.
mil com
rsnetworks usmc novell
FIGURE 27.4 Viewing a sample DNS hierarchy.
For this example, take a look at the following three URLs:
. http://www.novell.com
. http://www.rsnetworks.net
. http://www.usmc.mil
You may see after you enter some of the URLs (www.usmc.mil, for example) that although
it works, it is replaced by a different URL in the Location field of your web browser. In
this example, www.usmc.mil has been redirected to a new, longer URL. Both URLs lead to
the home page, or index page, of the website; the URL is being redirected by the web
server??™s internal configuration.
In these examples, the highest level of the DNS hierarchy is Root. A single period (.)
represents the Root domain, as shown in the illustration.
You can also see that the TLD is .com, .net, and .mil. In the early 1980s, about a halfdozen
main TLDs were designated for use. Domain names may be registered in three of
the most commonly used TLDs, which are .com, .net, and .org. There are many others,
but most serve limited purposes.


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