Domain Naming System

- DNS is like a phone book for internet.

- DNS matches domain names to their respective IPs when requested.

- IP address, instead of domain name is used to access webpage, if there is no DNS.

How does DNS work?

- While accessing a website, computer follows a series of steps to obtain IP address.

Step1: Request information

CPU takes the request and looks at local DNS cache ,otherwise request goes to DNS server of ISD.

Step2: Asking recursive DNS server

Server of Internet Service Provider (Recursive servers) also have cache which store recent information.If not,then they query to root name servers.

Step3: Ask the root nameserver

Root server is a computer which redirects the query to one who know where to find the answer.

Step4: Ask the Top Level Domain Server

TLD servers dont have the information needed but redirects the request to server(Authoritative server) where information is stored.

Step5: Ask the Authorotative DNS Server

Authoritative server knows all information about specific domain in the form of DNS records and sends requested info to the host.

Step6: Retrieve the record

Recursive server retrives record and stores in cache for furture purpose and also sends to requested computer.

Step7: Receive the answer

CPU stores the record in cache and passes the IP address to browser.Then browser opens connection to webserver and retrieves the webpage.

This entire process from, from start to finish, takes only milliseconds to complete.


Brief video for working of DNS