Thursday, 6 March 2014

Domain Name System



DNS stands for Domain Name System, or Domain Name Server.


DNS resolves an IP address to a hostname or vice versa.
DNS is basically a large database which resides on various computers that contains the names and IP addresses of various hosts/domains. Other than ip-address DNS also associates various information with the domain names.

Structure of a DNS

DNS uses a hierarchical tree based name structure. At top of the tree is the “root” ( represented as a dot (.) ) followed by the TLD ( Top Level Domain ), then by the domain-name and any number of lower level sob-domains separated by a dot.
The Top Level Domains are divided into 2 categories:
  • 1. Generic TLD (gTLD)
  • 2. Country Code TLD (ccTLD)
Below are some of the common Generic Top Level Domains:
  • .com – comercial web sites
  • .org – non profit organizations web sites
  • .edu – restricted to schools and institutions.
  • .net – originally for network infrastructures, now unrestricted