Hi 168.148.25.55 there is a message for you from 192.160.13.1

Things are different however when users have to send message. It is easier to remember names.  For example, the address for Microsoft is 175.152.207.123 but it would be easier to use the alphabetic name of Microsoft.com.

Each computer on a network thus has an address which is used to send and receive information from that computer. But how are these addresses generated? How are these addresses maintained? Just as your house unique, each host must have a unique address. If there is more then one address, there would be absolute confusion, since TCP/IP would not know which address to send it to. 

The domain name service (DNS) is the method is used to administer the internet system names. When you use names instead of a number, the internet and the TCP/IP utilities such as telnet, FTP, and SMTP access DNS to locate the address you have specified and resolve them into network addresses. When the name is received by DNS, it is translated in to a numeric address. This address is inserted into the message that has to be transported. And important feature of DNS is that it follows heirarchical structure to store address information. The information is stored in several places along the hierarchy rather that at one central location. Each site has a domain name server that maintains the information about the local nodes. 

Below figure illustrates the hierarchical structure of the internet. There is a top level, also called root level of the hierarchy. This is divided into major divisions called domains. 

 Some of the top level domains are as –

.com    :    commercial

.org    :    organizations

.edu    :    educational institutions

.gov    :    government agencies

.net    :    network service providers

.mil    :    military