How IP Addresses Work
To keep all of these machines straight, each machine on the Internet is assigned a unique
address called an IP Address. IP stands for Internet protocol, and these addresses are 32-bit numbers, normally expressed
as 4 "octets" in a "dotted decimal number." A typical IP address looks like this:
The four numbers in an IP address are called octets, because they
can have values between 0 and 255, which is 28
possibilities per octet.
Every machine on the Internet has a unique IP address. A server has a static
IP address that does not change very often. A home machine that is dialing up through a modem
often has an IP address that is assigned by the ISP when you dial in. That IP address
is unique for your session -- it may be different the next time you dial in. This way, an ISP only
needs one IP address for each modem it supports, rather than for each customer.
If you are
working on a Windows machine, you can view a lot of the Internet information for your machine, including your current IP address and hostname, with the command
IPCONFIG/ALL. On a UNIX machine, type nslookup at the command prompt, along with a machine name, like stuff.dewsoftoverseas.com
-- e.g. "nslookup stuff.dewsoftoverseas.com" -- to display the IP address of the machine, and you can use the command hostname to learn the name of your machine. [For more information on IP addresses
As far as the Internet's machines are concerned, an IP address is all you need to talk to a server. For
example, in your browser you can type the URL http://126.96.36.199 and you will arrive
at the machine that contains the Web server for Stuff.dewsoftoverseas.com. On some servers, the IP address alone is not
sufficient, but on most large servers it is -- see
How Name Servers Work
Because most people have trouble remembering the strings of numbers that make up IP addresses, and because IP addresses
sometimes need to change, all servers on the Internet also have human-readable names, called domain names.
For example, is a permanent, human-readable name.
It is easier
for most of us to remember than it is to remember 188.8.131.52.
The name stuff.dewsoftoverseas.com
actually has 3 parts:
Domain names are managed
by a company called Network Solutions.
Network Solutions' primary job is to create the top-level domain names, and to guarantee that all names within a top-level domain are unique. Network Solutions also maintains
contact information for each site and runs the "whois" database.
The host name is created by the company hosting the
domain. "www" is a very common host name, but many places now either omit it or replace it
with a different host name that indicates a specific area of the site. For example, in
encarta.msn.com, the domain name for Microsoft's
Encarta encyclopedia, "encarta" is designated as the host name instead of "www."
- The host name ("www")
- The domain name ("howstuffworks")
- The top-level domain name ("com")