What is DNS?

Domain Name System (DNS) is a database system that translates a computer's fully qualified domain name into an IP address.

If you want to interconnect two or more computers in a network, each computer needs to have a unique identification number, and this number is called IP address. Its of form 209.131.36.159. Its difficult for human being to remember this number. Hence we alias this number into user friendly domain name. For example yahoo.com is a domain name of ip address 209.131.36.159. 

How it Works?

Before we analyze how it works, we need to understand that networking is of

• Connecting computers within the organization
• Connecting computers outside the organization which are at remote places

So whenever DNS request is generated it goes through following steps

1. If requested IP lies with the organization, it is send to local DNS server which has list of all the computers names and their address.
   
2. If requested IP lies outside of organization, it is searched in the cache of local server, if found given back to requesting system. If not found then it is resolved using remote DNS servers, sometimes 2 to 3 remote servers. This process is explained in next section

The domain name may have serveral name components eg. swift.maruti.com or forum.swift.maruti.com. For querying purposes, software interprets the name segment by segment, from right to left. At each step along the way, the program queries a corresponding DNS server to provide a pointer to the next server which it should consult.
In the above example first address of com is resolved then address of maruti. This process is continued till the last segment.

To find the IP address of another computer, follow these steps:

1. From the Start menu, select Run... .
   
   
2. In the "Open:" field, type cmd and press the Enter key.
   
   
3. At the command prompt, type nslookup plus the domain name of the computer you want to look up, and then press Enter. For example, to find the IP address for www.yahoo.com, you would type: nslookup www.yahoo.com

   This command will return the following information:

C:\Users\Joe>nslookup yahoo.com