DNS -Domain Name System

DNS is a network protocol used to translate hostnames into IP addresses. DNS is not required to establish a network connection, but it is much more user friendly for human users than the numeric addressing scheme. Consider this example. You can access the Google homepage by typing 74.125.227.99, but it’s much easier just to type www.google.com!

 

To use DNS, you must have a DNS server configured to handle the resolution process. A DNS server have a special-purpose application installed. The application maintains a table of dynamic or static hostname-to-IP address mappings. When a user request some network resource using a hostname, (for example by typing www.google.com in a browser), a DNS request is sent to the DNS server asking for the IP address of the hostname. The DNS server then replies with the IP address. The user’s browser can now use that IP address to access www.google.com.

 

The figure below explains the concept:

 

 

Suppose that the DNS Client wants to communicate with the server named Server1. Since the DNC Client doesn’t know the IP address of Server1, it sends a DNS Request to the DNS Server, asking for Server1′s IP address. The DNS Server replies with the IP address of Server1 (DNS Reply).

 

The picture below shows a sample DNS record:

 

Here you can see that the host with the hostname APP1 is using the IP address of 10.0.0.3.