What is DNS and DNS hierarchy?

What is DNS?

For better understanding, everyone needs some background

Background: There are many servers all over the world. Every server has a unique IP Address and is identified by that IP Address.

Let's say if a site is hosted on a server with an IP Address of Don't you think, it is difficult to remember this IP Address for this site. If you even remember this IP Address. There are hundred of thousands of other websites for which you need to remember IP Address. That will be very difficult for a human to remember the IP Address of each and every website. So, the names (like www.dailywebsolutions.com) are introduced against IP Addresses in order to ease the process of remembering sites.

So, here comes the DNS (Domain Name System). DNS or this naming system holds the record of the domain and its corresponding IP Address. Domain Name System is a type of internet service that translates domain name into an IP Address.

What is Domain name?

A domain name is a unique name that identifies a website. E.g. webdevelopertuts.com is a unique name that identifies a single website.

What is nameserver?

Name server is a small part of a domain system (DNS). It is a type of server, which handles the requests to locate domain names. Mostly it holds the location of the domains hosted within its own local network.

What is authoritative nameserver?

There are many nameservers that can be used to locate a domain name but Authoritative nameserver is a server which holds the actual DNS records for a domain name.

What is authoritative answer?

When we request for the location of a domain name, we come up with an answer. If the query was answered by authoritative nameserver, then that answer will be know as authoritative answer.

What is Domain Name System (DNS) hierarchy?

DNS hierarchy has following elements:

  1. Root Level / zone servers
  2. Top Level Domains
  3. Second Level Domains
  4. Sub-Domain

Root Level / zone servers

It is the highest level in DNS hierarchy. The first step in resolving the domain name is root servers. It provides a list of authoritative name servers for top level domain (TLD). These servers have the list of all top level domains (TLDs). There are 13 root DNS servers all over the world. These root servers are named as A-root server, B-root server and so on upto K-root server. Root servers hold the information of each TLD that where is it located and what is its IP Address.

If you want more information about root servers that where are they located and who owns them or any other info, then you need to go http://www.root-servers.org.

Top Level Domains (TLD)

TLD is at the 2nd highest level domains in the hierarchical Domain Name System of the Internet. Top level domains are .com, .org, .edu etc. It will make more sense, if you take a look at DNS hierarchy diagram.

Second Level domains

It is 3rd level in the hierarchical Domain Name System of the internet. It is directly below the TLD. dailywebsolutions.com is an example of second level domains because it is directly below .com TLD.


Sub domain is considered as the part of the second level domains. Let's consider mail.dailywebsolutions.com, here mail is the sub domain of a 2nd level domain dailywebsolutions and .com is the TLD.