When you're on the Internet browsing web sites and sending emails you're using domain name servers without even realizing it. Domain name servers, or "DNS", are a seriously important but rather hidden part of the Internet, and they are fascinating! The DNS system makes up one of the largest and most active distributed databases on our planet. Without DNS, the Internet would shut down very quickly.

When you're typing a web-site name into your browser or sending an e-mail message, you're using a domain name. For example, the URL "http://www.dnshotbox.com" contains the domain name dnshotbox.com - So does the e-mail address "brian @ dnshotbox.com".

Names like "dnshotbox.com" are easy for us mere humans to remember, but computers don't like them too much. Machines prefer to use sets of numbers (rather like a ZIP or postal code) called IP addresses to talk to each other. As an example, this machine that the domain dnshotbox.com lives on has the IP address of 69.65.100.94. Every time you type in a domain name you use the Internet's Domain Name Servers to translate that name into the corresponding IP address that computers prefer. When you're browsing the web or sending emails, you're accessing domain name servers over and over again.

So, Domain Name Servers work in the background translating the domain names you use into IP  addresses. A simple enough job, except that there are now billions of IP addresses in use by computers around the world, hundreds of millions of people are using the internet making the same sorts of requests as you do, and domain names and IP addresses get created or changed daily.

On 3rd February 2006 (just an average day), there were a total of 63,340,462 domains in existence with extensions .COM .NET .ORG .INFO .BIZ and .US, with 1,857,007 new domains being added that day, 236,122 deleted and 81,787 transferred (data courtesy of dailychanges.com).

The DNS system is an enormous database, and no other database we know of gets so many requests for information, along with all the additions, deletions and transfers, all being made by millions of people around the planet - That's what makes the DNS system so unique, and your web-site vunerable when something goes wrong.

So, how does it work?

If we mere-mortals had to try to start remembering all the IP addresses of all of the web sites that we visit every day, we would all go quietly nuts. The same applies to email addresses. That's why we have bookmark folders and address books just to help us remember the names! We're just not that good at remembering bunches of strange numbers.

At the end of each domain name is a dot or period, followed by 2 or 3 letters. The 3-letter sets, like COM, EDU, GOV, MIL, NET, ORG and INT, are called top-level domains (TLDs) or first-level domains. There are several hundred top-level domain name extensions, as well as unique two-letter combinations for every country (US, CA, UK, DE, TV etc).

Within every top-level domain there is a huge list of second-level domains. For example, in the COM first-level domain, you've got yahoo, microsoft, aol, compuserve, and millions of others including dnshotbox (us!).

Every name in the .COM top level domain has to be unique, but there can be duplication across domains. For example, netnibble.net and netnibble.eu are completely different machines - They're not even in the same country!

To the left of the domain name is one more "word" like www, mail, ftp. This is the host name. It identifies the name of a specific machine (with its own specific IP address) within a domain. Any domain could potentially contain millions of host names as long as they are all unique within that domain.

Whilst it's important to have one central authority keeping track of the database of names in the COM (and other) top-level domain, you would not want to centralize the database of all of the information in the COM domain. As an example, The Microsoft Corporation has thousands of IP addresses and host names. Microsoft maintain their own domain name server for all of the microsoft.com domain. Similarly, countries do the same - The UK administers the UK top-level domain, Canada looks after the CA domain, Australia looks after AU, and so on. This is why the the DNS system is called a distributed database.

Each and every domain has a Domain Name Server somewhere in the world handling its requests - In essence Domain Name Servers spend all day accepting requests from programs to convert domain names into IP addresses and accepting requests from other name servers to convert domain names into IP addresses.

When a request comes in the Domain Name Server responds in one of four ways:

These question and answer sessions go on millions of times a day, with Domain Name Servers asking "up the line" for information and passing it back down when they find it.

Now that, hopefully, you understand a little more about the workings and complexities of DNS, take a look at our page on "The Yahoo Story".