The Domain Name Service or DNS is a system that converts human-readable domain names to the IP addresses used by other networking protocols. The Domain Name System has played an essential role in the functionality of the internet since 1985 by providing a worldwide distributed service. Every intent user is connected to DNS servers that map domain names to IP addresses through a procedure called DNS name resolution.

DNS servers make it easy for you to get the information when they retrieve these pieces of data from their database, which is organized hierarchically through a domain name tree that subdivides into different categories.

What will we learn?

  1. Domain Name
  2. Third Level Domain
  3. Second Level Domain
  4. Top Level Domain
  5. DNS Resolution
  6. DNS recursor
  7. Root name server
  8. Top-level domain (TLD) name server
  9. Authoritative nameserver
  10. Types of DNS Queries
  11. Recursive Query
  12. Iterative Query
  13. Types of DNS records
  14. History

Domain Name

Websites are not public until there has been an effort to make them so. In order to go live, a website must be hosted and then made accessible on the internet. Usually, this is done via DNS resolution and by obtaining IP addresses for your site based on parts of the domain name consisting of 3 different elements which are:

Third Level Domain

It pertains to the subdomain of a domain. It appears prior to the second level domain; Example: www.

Second Level Domain

The second label in a site’s Domain name is a specific designation. This separates the site from other sites with domains that are the same or similar to it.

Top-Level Domain

A top-level domain, also alluded to as TLD, pertains to the highest organization level on the internet. Based on that organization, TLD servers hold authoritative servers . There are two types of these domains:

Generic - .org, .net, .com

Country Code - .au, .de, .uk

DNS Resolution

DNS resolution is also based on four components. These are the domain name system, root servers, registrars and registrants.

DNS recursor

It is a device that responds to queries from a client computer. The recursor functions as an intermediary for the internet browser, with queries routed through it by the web server, and supplies answers to requests made of any domain on the Internet.

Root name server

Across the world, there are thirteen root servers. These help to redirect a resolver to locate the domain name server for a sites internet protocol address. Think of it as your index, which directs you to where you would find something in a book so that you may know how page numbers correspond with specific words and phrases.

Top-level domain (TLD) Nameserver

It distinguishes websites with .org, .net, and .com at the end of their addresses. Afterwards, the TLD name server redirects the request to the name server which is authoritative.

Authoritative Nameserver

The TLD nameservers can give out the source IP address of a domain name for those looking to learn more.

After typing in a websites name, a user is able to access different components of the DNS resolution process by clicking on links.

  • A user types the website address into the search engine.
  • The device queries a DNS recursor to find the IP address of a given site.
  • The DNS root servers are queried with a request for the IP address of the web server, if this information is not yet in their system. This produces a list of TLD servers (such as .com) and redirects them to the appropriate domain name server depending on what was requested.
  • Every top level domain (TLD) has its own set of spelled-out records for the authoritative nameservers. Based on the second-level domain, and whether your recursing system is customizable or not, it pertains to which actual authoritative name server youll be querying.
  • The DNS server routes queries from your computer to the appropriate hostname or IP address. If a query has already been made in some iteration, it will be cached and provide the response.
  • Your web browser can access the website.

Types of DNS Queries

Two primary queries that take place at the time of DNS resolution are as follows:

Recursive Query

A recursive query is a computer or devices initial DNS lookup of an IP address when accessing a website. If the computer or device has not previously cached the web domains IP, it then queries its own cache system (or local DNS server) for any relevant name and address, which in turn searches other DNS servers to retrieve the best answer.

Iterative Query

A recursive query asking for the IP address of a hostname is sent to a DNS server when it can’t be found locally. The recursive query will only return the information necessary to identify and send an iterative query, in order to prevent overburdening itself or other servers with responsibility for resolving unknown requests.

Types of DNS Records

Type of DNS RecordDefinitionAcronym
A RecordThe IP address of the domain is stored in a record.
Quad-A RecordThis stores the IPv6 address and hostname for a computer.
Alias RecordIt is to change the domain name and redirect it somewhere else.CName
Mail Exchanger RecordRefer how email messages should be routed according to the SMTP
Service Location RecordSpecifies the program that hosts different types of services, like VoIP or instant messaging.
Name Server RecordIt indicates which server has the authority for that domain.
Start of AuthorityKeep a record of important information about a site, such as administrative contact info.
Reverse-lookup Pointer RecordIt offers a domain name in reverse-lookups.
Certificate RecordRecord and keep the credentials for encryption certificates, like PGP, PKIX, SPKICERT
Text RecordIt allows a domain administrator to enter text into the DNS.TXT


The Domain Name System (DNS) was a response by ARPANET to make its data and information more available. It is the best procedure of transferring information between research centres in America, with more than 300 computers joined with the system. Hostnames are incorporated into the system alphabetically, which removes the need to memorize their IP addresses.

As the technology grows, it becomes more important to develop a centralized management system. Paul Mockapetris introduces a new procedure of naming websites with help from colleagues Zaw-Sing Su and Jon Postel.

This method uses a category name and the specific site name. The top-level domain refers to the category, whereas the second level domain refers to the specific site. The creation of a method that could translate the websites domain name to the IP address it needed eliminated users need to be aware of the servers IP address. In 2013, over 270 million URLs were served from this organized database.