Every computer on the Internet has a number, called the "IP Address".
An IP address has four numbers connected by three dots and looks like this:
16.245.23.14
The four numbers are each in the range of 0-255. There must be four of these numbers. It's pretty easy to see if an IP addres fits the pattern. Four number, three periods, each number in the right range.
The IP adress is like a phone number on the telephone system.
If you want to reach someone on the telephone, you need their number.
To communicate with someone in the intenet, you need the IP address of their computer. Every computer on the internet has one, though often we aren't aware of them.
If you look at a telephone number, you can tell what area it is in by looking at the "area code". There's a similar idea on IP numbers.
On telephone numbers, the number breaks up like this:
country code - area code - local number - number
For example, the number 1-310-395-5500 breaks down like this
Country code = 1 (US)
Area code = 310 (Western Los Angeles)
Local area = 395 (one of several local codes in Santa Monica)
Number = 5500 (the actual number)
If we had a different country code, we could have a number in Germany (49) or France (33) or Mexico (52). America invented the telephone so I guess that's why America has country code = 1.
IP addresses break down in a similar manner, but it's a little more flexible and the numbers are more logically thought out. Each of the four numbers in an IP address has the range 0 to 255. IP addresses generally belong to Intenet services. You can tell what service, what country, and often what area an ip address is, if you have a table showing available IP addresses.
You can find that ip addresses that start out the same are usually in the same country and often the same internet provider. Each provider is assigned a group of addresses, and they can manage those addresses among their customers however they like.
There are certain IP addresses tha are reserved for local networks. The addresses start with either 10 or 192. If you see an address like this it means the computer is connected to a router. In that case the router will have a real IP address. Tech people call this kind of IP address a "Bogus Address". They aren't invalid, but they aren't public addresses. It just means they are behind a firewall or router of some kind.
Addresses that start with 169 are invalid addresses and mean there is some kind of error.
For example, if you are connecting your computer to a router, like a wireless router at home or at school, you will be assigned an ip address when you connect. If your connection is ok you will generally get an address that starts with 192.168; for example 192.168.2.1. I'm using a mac laptop right now, and here's my address:
So, the address starts with 192. Excellent. I'm online.
But in this next image we see a problem:
If you are assigned an address that starts with 169 it means your connection failed. This is useful information and worth remembering.
A domain name is a way to address computers using a name instead of numbers.
You may remember that phone numbers used to have name equivalents to make them easier to remember. For example, my parents used to have the phone number 747-3739. They called that number "Sherwood 7" instead of "747" because it was easier to remember.
There is a similar idea for IP addresses, which is the system of domain names.
If you don't want to call a server 68.183.106.122, you could call it www.brandx.net.
An example will help. Open your web browser and open this address: http://68.183.106.122
Now try this one: http://www.brandx.net.
They both take you to the same site, right?
So what you can see is that the same server can be reached by using an IP address or the associated domain name.
URL stands for "Uniform Resource Locator" which is a fancy way of saying a web address.
Here's a sample URL that will tell us how to locate a specific file on the internet:
http://www.brandx.net/lacc/caot97/index.html
Here are the different parts of that URL
http:// <-- this means you should load this address with a web browser. This part is optional since it's usually pretty obvious.
www <-- this is the name of the server. All computers have names.
brandx.net <-- this is the domain, or network name. "brandx.net" is a domain that belongs to Brandx X Internet. The top level domain here is .net.
/lacc/caot9/ <-- this is the folder where our file will be found.
index.html <-- this is the name of the file.
So this url says that the file we want will be found on the server www in the network brandx.net, in the folder /lacc/caot97, and the name of the file is index.html.
Many of the parts of the URL are optional. If you don't fill them in then the system will make a best guess. If you don't put the filename, it will assume index.html. If you don't put a folder, it will assume the main folder. If you don't put the server name it will usually assume www.
The domain name is the part of the URL that ends in .com or .net or .org. There are many other possible domain name types. A domain name is a single word with no space and usually ends in .com (such as yahoo.com) or .net (such as brandx.net). Names that end in .org are organizations, such as sierraclub.org. Names that end in .edu are schools such as lacitycollege.edu. Names that end in .gov are government agencies such as whitehouse.gov.
A domain name can be a URL but the reverse is not true. A URL could have a folder and a filename and a servername, while a domain can't.
This is a domain name: brandx.net
This is not a domain name: www.brandx.net
There is a nice article about domain names on Wikipedia if you click here.
If you want to start your own network, you can buy a domain name.
This is called "domain name registration". The process is pretty simple. You just go to one of the domain name registration companies, pick the name, pay your money, and the domain is yours.
Originally domain registration was done by an organization called the "InterNIC" which was paid for by the National Science Foundation as part of the Internet project. Domain registration was free. For example, I registered the domains "leonardo.net" and "brandx.net" in 1994 and 1997 and I don't think I paid anything for either one. At that time the Internet was mostly University people and Researchers and it wasn't very commercial.
The InterNIC itself is an interesting animal. It was run by a company called "Network Solutions" which in turn is owned by SAIC.
When conspiracy theorists talk about the "Military Industrial Complex" and secret backdoor deals and government military contracts, they are talking about companies like SAIC and Network solutions. They are involved in all kinds of secret CIA and military contracts that never see the light of day. Their primary area of expertise is getting these consulting contracts. Most of the contracts involved in the Internet have never been put up for bid, and there have been plenty of abuses by Network Solutions.
The charge for domain names is typical. Originally Network Solutions was paid by the government to register domains. They realized there was nothing in their contract to prevent them from charging for domain names, so they decided to go ahead and start charging. The fees were not based on expenses (because they were already getting paid by the NSF) but on waht they thought people were willing to pay, which at that time was $100. A lot of people were pretty unhappy about this, but there wasn't much they could do.
These charges were pure profit for Network Solutions, and they became a multi billion dollar company as a result. Taxpayers really got robbed. It seems since taxpayers paid for the Internet and the registration, taxpayers should profit, but instead a private company has figured out how to take all the money for themselves. Nice.
Eventually there were lawsuits over this and a number of other abuses by Network Solutions, and registration was opened up to other competitors. Companies like name.com and godaddy.com offer domains now for under $10 a year.
Excercise
Which of the following are valid IP addresses? Which are valid domains? Which are URL's (web addresses)? Which are emails? Which don't fit any of these categories?