How DNS works?

Introduction

Laymen explanation

When you type google.com in browser, your browser needs to find the address of this website. In computer world, IP address gives the location of website. So, there should a web server which should store mapping between domain name and corresponding IP address. Such servers are known as DNS (domain name server)

Technical explanation

An often-used analogy to explain the Domain Name System is that it serves as the phone book for the Internet by translating human-friendly computer hostnames into IP addresses. For example, the domain name www.example.com translates to the addresses 93.184.216.119 (IPv4).

In general, the DNS query process occurs in two parts:

• A name query begins at a client computer and is passed to a resolver, the DNS Client service, for resolution.

• When the query cannot be resolved locally, DNS servers can be queried as needed to resolve the name.

Types of DNS service

Authoritative DNS server

An authoritative DNS server stores the DNS request. So if you ask an authoritative DNS server for one of its IP addresses, it doesn’t have to ask anyone else. The authoritative name server is the final authority on those names and IP addresses.

Recursive DNS resolver

When the client queries a preferred DNS server, it first checks locally for cached answer. If answer not available, the query process can continue, using recursion to fully resolve the name. This involves assistance from other DNS servers to help resolve the name. By default, the DNS Client service asks the server to use a process of recursion to fully resolve names on behalf of the client before returning an answer.

Google public DNS is example of recursive DNS. Moreover, DNS server provided by ISP are recursive DNS.

Zones in DNS

Domains can be very large, so they are further organized into smaller books, called, “zones.”

DNS Servers type

DNS recursive server

Root name server

TLD name server

Reference

https://technet.microsoft.com/en-in/library/cc775637(v=ws.10).aspx

http://dyn.com/blog/recursive-dns-how-does-it-work/

https://en.wikipedia.org/wiki/Domain_Name_System

https://developers.google.com/speed/public-dns/docs/intro

https://images.app.goo.gl/qDQtYkKigrtH6MzP7

https://www.varonis.com/blog/what-is-dns/

https://images.app.goo.gl/CrKYj9MyRc2tnE63A

https://images.app.goo.gl/6DKbz1B1W89CMpJs8

https://images.app.goo.gl/1Mbc64hjXAiWtBKf9

https://images.app.goo.gl/XT5AMgLxNqtgPodZ7

https://images.app.goo.gl/J3mP6uFhQ46xrqXn7