DNS : The Domain Name System

Why we use DNS? To know this follow the link http://t4test.com/blog/etchosts-the-host-file/

Because of sheer numbers of hosts on the Internet, we can’t use host’s file (/etc/hosts) them. The ineternet has centralized file in its teens, but its maintenance because so painful that Berkeley had to step in with the Domain Name System (DNS). DNS is a distributed system that is scalable, easy, It introduces three key concepts:

1. A hierarchical organization of host names
2. A distributed database for performing the name-address mappings.
3. Delegation of authority to individual levels of hierarchy.

In the Internet namespace, hosts belongs to domains, which in turn could belong to sub domains, and so fourth.

Like in the file system, these domains and sub domains form a hierarchy with the root domain as the top, signified by a . (dot).  The root domain has immediately below it a number of top level domains (TLDs) or generic domains like edu and com. These in turn have number of sub domains or second level domains under them in the same way folder has sub folders under it.