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1.2. Talking the Internet Talk
Every computer connected to the Internet (even a beat-up old Apple II)
has a unique address: a number whose format is defined by the Inter-
net Protocol (IP), the standard that defines how messages are passed
from one machine to another on the Net. An IP address is made up of
four numbers, each less than 256, joined together by periods, such as and
While computers deal only with numbers, people prefer names. For this
reason, most computers also have names bestowed upon them. By cur-
rent estimates, there are hundreds of millions, if not billions, of devices
on the Net, so it would be very difficult to come up with that many unique
names, let alone keep track of them all. Instead, the Internet is a net-
work of networks, and is divided into groups known as domains , which
are further divided into one or more subdomains . So, while you might
choose a very common name for your computer, it becomes unique when
you append, like surnames, all of the machine's domain names as a
period-separated suffix, creating a fully qualified domain name.
This naming stuff is easier than it sounds. For example, the fully qualified
domain name translates to a machine named "www"
that's part of the domain known as "oreilly," which, in turn, is part of the
commercial (com) branch of the Internet. Other branches of the Inter-
net include educational institutions (edu), nonprofit organizations (org),
the U.S. government (gov), and Internet service providers (net). Com-
puters and networks outside the United States may have two-letter ab-
breviations at the end of their names: for example, "ca" for Canada, "jp"
for Japan, and "uk" for the United Kingdom.
Special computers, known as nameservers , keep tables of machine
names and associated IP addresses and translate one into the other for
us and for our machines. Domain names must be registered and paid for
through any one of the now many for-profit registrars. [*] Once a unique
domain name is registered, its owner makes it and its address available
to other domain nameservers around the world.
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