What is a domain name?

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This is a non-technical guide to the domain name system (DNS.)

Domain name system (DNS) allows people to navigate their way throughout the Internet.  Every computer connected to the Internet has an address.  This address, which is much like a telephone number, consists of a relatively complicated string of digits, and is called an IP address.  IP is the abbreviation of Internet Protocol.

Remembering this address is difficult for people.  DNS solves this problem by enabling use of a series of characters instead of the IP address.  For example, instead of entering the IP address 66.218.71.91, you can use www.yahoo.com.  DNS is a tool which simplifies memorizing and remembering Internet addresses.

DNS aims to enable anyone from anywhere in the world to find a site's IP address using the domain name.  In addition, domain names are used for accessing email addresses, and other Internet-based services.

What does "registering" a domain name mean?

When you register a domain name, a new entry is created in the list of all the domain names.  This allows users from all over the world to access your Internet address using that name.

How long is a domain name registered for?  Is it renewable?

This is different for different domain name extensions, but is a multiple of one year.  The maximum for registering a domain name is ten years.

What are the Global Top Level Domains (gTLD's)?

What are the Country-Specific Top Level Domains (ccTLD's)?

See a list of all Country-Specific Top Level Domains.

What goes on behind the scenes?

What goes on behind the scenes is a little bit more complicated.

In a domain name, such as yahoo.com, the .com part is referred to as Top Level Domain (or TLD.)  Companies involved in registering top level domain names, maintain huge databases containing information on top level domains.  As an example, the database belonging to the company which manages the registration of the .com domain names, includes the yahoo.com domain name.  Therefore, in search of the Internet address for yahoo.com, your computer needs to find a path to the aforementioned company's database.  How does this take place?

At the heard of the domain name system are 13 special computers named root servers.  These are managed by the ICANN organization, and are distributed across the world.  All 13 computers contain the same information, and they are distributed for purposes of dividing the work load and supporting each other.

You may ask why are these root servers this important?  The reason is that these computers contain the Internet addresses for the top level domain companies, including those managing gTLD's (like .com) and 244 others managing ccTLD's (like .ir for Iran, .fr for France, etc.)  This is critical information.  If this information is not 100% accurate or has any ambiguity, it might not possible to find a key registration company on the Internet.  Let's see how this information is utilized.

There are thousands of computers distributed across the globe with the purpose of resolving the Internet addresses belonging to each name.  They constantly store information that they receive from requests to the root servers.  The goal in using them is answering users' requests to find Internet addresses for each domain name.

When a user tries to access yahoo.com, for example, this request is forwarded to one of these local computers.  That computer divides the domain name into its ingredients (separated by dots.)  The address of the .com registry is known to that computer, because it has already obtained it from the root servers.  So, this computer forwards the request to the .com registry database.  The response to this request is sent back to the user's computer.  This way, the domain name gets resolved.

These local computers and the root servers contain the same information.  So, why we use them instead of directly querying the root servers?  The answer lies in increasing the performance.  The root servers cannot process hundreds of billions of requests per day.

If you're still following the story, you might ask yourself how do more complicated names, such as www.yahoo.com, get resolved?  The DNS is implemented in a hierarchical structure.  First, the Internet address of the .com registry gets resolved, and then the computer sitting at that address is queried for the address belonging to yahoo.com, and next the computer at that second address is responsible for returning the Internet address for www.yahoo.com upon being queried.  This is the final address we've been looking for.

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