We already talked about the “central database” for domain names a little earlier. Now this database is stored on several very large computers that are scattered around the world. The central database is maintained by a company called InterNIC.
When you buy a domain name, your details (name, company name, address, etc.) are recorded in the database along with the domain name, the date that you purchased the name and the date you will be due to pay a “renewal fee” for the domain name. Depending on how and through which company you bought the name initially, you will own the right to use the name for between 1 year and 10 years before you have to pay this renewal fee (each company has slightly different policies, so read the small print carefully when you register a domain name!)
“Register” was in bold for a reason: when you buy a domain name, it is said that you are “registering” it (since in fact all your details are being registered, or recorded, in the central database). This is why the companies that let you buy domain names are called “registrars”.
This next part is the technical bit. You can skip down to the next box unless you are really keen to learn more about how the domain name system actually works.
One thing you may well come across when registering a domain name is a request for information about the name servers you will be using.
You remember we talked about domain names being a substitute for IP addresses? Well, there has to be somewhere where a computer can go to find out what IP address is associated with a particular domain name, since computers use IP addresses to locate data around the Internet. This association information between domain names and IP addresses is stored on a name server (or nameserver – both spellings are used!)
Think of a website as a store set well back from a road, behind some trees. To find the store, you’re going to need a sign. You can think of the domain name as that sign, and the IP address as the direction in which the sign is pointing. If the workmen who were hired to put up the sign don’t know where the store is, they will leave the sign pointing in a random direction. This is similar to why many domain names do not seem to lead anywhere: they do not have a particular IP address associated with them.
Now think of the name servers as foremen who tell the workmen in which direction to point the sign. Once the sign is pointed in the specified direction, it will not be moved unless the workmen give new instructions. Each name server is responsible for maintaining the master record of the information associated with certain domain names.
A domain name record requires two name servers: a primary name server (also known as a domain name server, or DNS for short) and a secondary name server. Name servers are scattered all over the Internet – there are thousands of them – and each one passes on requests for information (“where’s the store?”) until it reaches the primary name server, which replies (“it’s over there… see, where that sign is pointing to”) and maps the domain name to the IP address, letting your computer find the right website. If the primary name server is not accessible (broken, switched off, behind a slow connection, etc.) then the request for information will be sent to the secondary name server.
In practice, things are more complicated than the simplistic picture painted above. For instance, many name servers cache information about commonly requested mappings between domain names and IP addresses (= record that information locally so that it can be reused again for later requests). This is why, when you change the information on a particular domain name, such as the IP address it points at, it can take several days for people all over the Internet to find your site at its new address (since the information cached on their local name servers is out of date, and takes a while to get refreshed). This is know as propagating new domain name information.
Most domain name registrars (companies selling domain names) will set up your new domain name on their name servers, at least until you want to “move” it somewhere else. If you move a domain name, you are basically transferring the right to maintain the association between that domain name and its IP address to a different name server. This is often necessary, for instance, when changing web hosting companies. Again, the technical support staff at your web hosting company should be able to help you on this issue in more detail.