All telephones are associated with a number. Anyone entering a certain number will be connected to a particular phone. Can we think of the telephone number as the phone address, that it is unique, and no other phone has the same number?
In the same way that telephones have a unique address, computers connecting to the Internet must also have a unique address. The addressing scheme on the Internet is IP (Internet Protocol). Unlike telephone numbers, IP addresses are long binary numbers that are easy for computers to manage but difficult for people to use.
Compare computer IP addressing to the system of phone numbers. When someone needs to make a call and the phone number is unknown they often turn to a phone book to find the number. What does a computer turn to?
It turns to the Domain Name System, the system that brings two main features to the Web. First it provides order to the naming scheme of Internet hosts while also providing the means in which to find a particular host, say Google, by specifying the name. DNS is the phonebook of the Web. It works automatically through the Web browser to look up the IP address of a particular Web address.
Keeping with the Google example, when the user enters www.google.com into the address bar the PC may not immediately go straight to the Google Web site. It may first send a DNS request asking for the IP address of www.google.com. Somewhere, a DNS server responds with Google's IP address which, when armed with the actual address, allows the original PC to send a Web page request to Google.
Internet Service Providers often maintain DNS servers for customers while DNS servers at the top are administered by ICANN - see www.icann.org for more information.
Ron Poland is a professor in the Computer Information Systems AAS program at Clinton Community College. Poland is certified in company repair and networking by the Computer Technology Industry Association (CompTIA). He is also a Cisco certified network assistant. Questions may be sent to him via e-mail at email@example.com.