Chapter 5. How
Internet Addresses and Domains Work
The heart of how the Internet works is the
Domain
Name
System (DNS), the way in which computers can contact
each other and do things such as exchange email or display web
pages. When someone on the Internet wants to contact a locationfor
example, to visit a websitehe types in an address, such as
www.metahouse.com. (A specific location on the Internet is also
referred to as a
uniform resource locator,
or
URL
.) The DNS
translates
the plain
English address, www.metahouse.com, into a series of
numbers
called
an IP (for Internet Protocol) address. An IP address, such as
123.23.43.121, marks the location of a computer on the Internet
similar to the way a house number and street mark the location of
where you live.
In this example, metahouse.com is called a
domain
. To work most
efficiently
, the Internet has been
organized into a number of major domains.
Major domains
refer to the
letters
at the end
of a plain English address, such as .com. A number of common
domains are .com (commercial), .edu (education), .gov (government),
.mil (military), .net (Internet service providers and
networkscompanies and groups
concerned
with the organization of the
Internet), and .org (organization).
Domains are organized in a hierarchical manner,
so that
beneath
major domains are many minor domains. As an example
of how the DNS and domains work, look at NASA's SPACElink Internet
address: spacelink.nasa.gov. The top domain is .gov, which stands
for government. The domain just below that is .nasa, which is the
NASA domain. Then, spacelink identifies the NASA computer that runs
the SPACElink program. SPACElink's numeric IP address has changed
through the
years
, but its Internet address has stayed the
same.
Computers called
name servers
are
responsible for keeping track of such changes and translating them
between IP addresses and domain addresses. The Internet can't
understand alphanumeric Internet addresses, such as ziffdavis.com,
so name servers translate those addresses into their proper numeric
IP addresses, such as 163.52.128.72. Name servers contain tables
that match
alphanumeric
Internet addresses to numeric IP
addresses.
When you connect your computer to the Internet,
your computer needs to have an IP address assigned to it to do
common things, such as browsing the Web. Depending on how your
computer is set up and how your service provider operates, you
might have a static address or a dynamic address. A
static
IP address never changes, so if you have one, you will have the
same IP address every time you connect to the Internet. However,
because the Internet has only a limited number of IP addresses,
many ISPs use dynamic addresses. With a
dynamic
IP address, you are given an IP
address from a limited block of IP addresses every time you
connect. In this way, ISPs don't have to have an individual address
for every subscriber. Instead, they can share their pool of
addresses among all subscribers.
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