The
Internet
IP Addresses
Domains and Sub-domains
Servers
Resources
The Internet is not the world wide web - nor is it web browsing. This is a common misconception. Often people will say such things as, "OK, I am finished with email. Now I want to use the Internet." Email is something you can do over the Internet - as is web browsing with Netscape or Internet Explorer.
In other words, the Internet is a collection of computers, networked together throughout the world, and communicating with each other through a common language called TCP/IP (Transfer Control Protocol/Internet Protocol).
The various programs you use recognize TCP/IP, and if everything is set up correctly, and the computer is correctly connected to the Internet, all sorts of things can be done, including:
In order to identify all the computers and other devices (printers and other networked peripherals) on the Internet, each connected machine has a unique number, called an "IP address". IP stands for "Internet Protocol," the common language used by machines on the Internet to share information.
An IP address is written as a set of 4 numbers, separated by periods, as in
203.183.184.10
This representation is sometimes referred to as dotted-octet representation of an IP address.
Here is some simple mathematics you should know! Each number in this four-number address can range from 0 through 255. So there are 256 different possible numbers for each part.
Since there
are four parts, so there are a possible 256 X 256 X 256 X 256 =
256 to the 4th power = 4,294,967,296 different possible machine
numbers - over four billion different possible machine numbers.
This sounds like more than enough addresses to go around, but IP
addresses are beginning to run out.
One single network, for example, might typically have all the IP
addresses starting with 203.183.184 (203.183.184.0 through 203.183.184.255).
This has been a customary way of distributing IP numbers - in chunks
of 256 addresses. This is referred to as a "Class C" network. If
numbers are distributed as Class C networks it means there are only
a possible 256 to the 3rd power different networks - or just 16
million networks - in the whole world.
When you say it like that it doesn't sound like so many networks,
because every office and many offices within offices have their
separate network of computers.
To make
matters worse, many networks don't even use all the 256 IP addresses
available to them, which means that although the IP addresses are
reserved by them they are going to waste.
To help solve this problem, networks have started being assigned
with just 8 or 16 IP addresses. Some special techniques using local
IP addresses that aren't visible to the outside world are also helping
alleviate the strain.
But basically you should understand that you need a fixed, predefined IP address assigned to each machine that acts as a server to the outside world. You can get an IP address assignment from your network administrator, who receives them in turn from your network's Internet provider.
Domains & Sub-domains
Each machine having its own unique IP address is great for machines
communicating with each other, but quite difficult for humans to
remember.
For example, the mail server at Web Crossing Harbor has an IP address
210.226.166.200. You could send email to doug@210.226.166.200, but
it isn't very convenient for a lot of reasons. For one thing, it
is difficult to remember. For another, we might need to move the
mail server to a different machine (with a different IP address)
someday. Then we would have to tell everybody our new IP address
in order to receive mail.
To solve this problem a system of giving easy-to-remember names to IP addresses was created. This system is called the domain system. There are several top-level domains, and all other names fall under that in a hierarchy of sub-domains.
There are two basic kinds of top-level domains - those based on type of activity and those based on geographical location:
Some Activity Based Domains |
|
|
.com |
Perhaps the most well-known top-level domain. Originally it was designated for use by companies and commercial activities. Now it can be used by anybody for any purpose. |
|
.org |
Originally designated for use by nonprofit organizations and individuals, now it can be used for any purpose. |
|
.net |
Originally designated for use by network organizations (such as Internet providers). Now it can be used for any purpose. |
|
.gov |
For governmental organizations in the United States. |
|
.mil |
For military organizations in the United States. |
|
.edu |
For four-year degree-granting colleges and universities only. |
| Some Geographic Based Domains |
|
|
.jp |
The Japan domain |
|
.us |
The U.S. domain |
|
.ca |
The Canada domain |
|
.to |
The Tonga domain |
Some geographic domains, such as the .to (Tonga) domain, open up their domains and make them available to anybody in the world.
One common misconception is that ".com" is a domain for companies located in the U.S. It isn't - any company in the world can use a .com domain.
A "host" refers to a fully specified domain, specified completely down to the specific machine and complete IP address. For example, webxharbor.com is a sub-domain of the .com domain. www.webharbor.com is the name of the web server machine in the webxharbor.com domain. It has a corresponding IP address, but you do not need to know it because the domain name system keeps track of it for you.
When the Internet first started out there was just one big list with all the hosts in the world and their corresponding IP addresses. But the list quickly got too large and these days the same task is accomplished with the use of a distributed DNS (domain name server) system, components of which are located on most networks throughout the world (including the WebXHarbor office).
Servers
A server is just a host that serves something. Some examples are:
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