Week 12: Clear

Domain Name Service

Have you ever wondered about how it works that when you type in a name or link of a website into the search field of your internet browser, the website you wanted to look at, turns up?

The answer to this question is with the help of Domain name service or shortly called DNS. The DNS is a database that looks up the host and domain names that are entered and returns the actual IP address. You can think of it like a huge collection of phone books being called nameservers which are able to find e-mail servers and web-servers.

Graphic 1: Illustration of how DNS functions

 

Let’s look at an example to get the real underlying sense and procedure.

Imagine you want to surf on www.google.com. First of all you type this address into the search field of your browser. The DNS resolver helps your computer to find this website address, as your computer alone is not able to find it. The DNS resolver looks into the DNS (the “phonebooks”) listing host/domain name combinations, to find the matching IP address. However, it alone is not able to find the IP address, so it contacts root nameserver. These root nameservers cannot provide the IP address, but they are a good starting place for searching, as they will point to a .com nameserver, because of the “.com” ending. These .com nameserver won’t know the right IP-address itself, but will point at a google.com nameserver. Finally, the google.com nameserver knows the IP address and can respond to the query of the DNS resolver. Then the DNS resolver receives the IP address from the google.com nameserver and will provide that information to your computer.  As soon as your computer knows the IP address it will be able to communicate directly with www.google.com and you are able to serve on www.google.com.

Whenever you have visited one website your computer stores that information, so the IP-addresses, in a storage called “cache”. The cache makes it possible to speed up your searches if you search for websites you have already been to. You can think of it as bookmarks in the telephone books. You know where to look for the information much faster. So the whole procedure explained above just takes place if you visit a website for the first time.

Original graphic by Everaldo Coelho on Wikimedia.org:

http://commons.wikimedia.org/wiki/File:Computer_n_screen.svg

Original graphic by George Shuklin on Wikimedia.org:

http://commons.wikimedia.org/wiki/File:Server-tower.svg

Original graphic by GNOME icon artists on Wikimedia.org:

http://commons.wikimedia.org/wiki/File:Gnome-network-server.svg

Modified by Nina Maria Scherl.