Concept of DNS Server

What is Technical Defination of DNS ?

The DNS translates Internet domain and host names to IP adresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.

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What is DNS Concepts & How to Implementation

The Internet's Domain Name Service (DNS) is just a specific implementation of the Name Server concept optimized for the prevailing conditions on the Internet.

DNS Overview

From our brief history of Name Servers we saw how three needs emerged:

1. The need for a hierarchy of names
   
2. The need to spread the operational loads on our name servers
   
3. The need to delegate the administration of our Name servers
   

The Internet Domain Name System elegantly solves all these problems at the single stroke of a pen (well actually the whole of RFC 1034 to be precise).
Domains and Delegation
The Domain Name System uses a tree (or hierarchical) name structure. At the top of the tree is the root followed by the Top Level Domains (TLDs) then the domain-name and any number of lower levels each separated with a dot.
NOTE: The root of the tree is represented most of the time as a silent dot ('.') but there are times as we shall see later when it VERY important.
Top Level Domains (TLDs) are split into two types:

1. Generic Top Level Domains (gTLD) .com, .edu, .net, .org, .mil etc.
   
2. Country Code Top Level Domain (ccTLD) e.g. .us, .ca, .tv , .uk etc.
   

Country Code TLDs (ccTLDs) use a standard two letter sequence defined by ISO 3166. Since 2004 gTLDs now have a sub-category known as sTLDs (Sponsored TLDs) which implies they have limited registration, examples of sTLDs include .aero, .museum, .travel, and .jobs whereas the normal gTLDs typically have open registration requirements.