What is DNS? Domain Name System Definition

What is DNS? DNS translates the IP addresses to domain names and vice versa. In this article, we will explain how this process works while providing the basics about it.

Updated: 19 Nov, 23 by Babak Nasiri 16 Min

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When the Internet began, it was simpler for users to associate IP addresses with particular machines. However, this didn't persist long as more hardware and users joined the expanding network. Users desired website names that would be simpler to remember, even if it is still feasible to access a specific website by entering its IP address into a browser. 

When it first launched, Elizabeth Feinler, a Stanford professor, individually issued names and addresses to each machine connected to the Internet. This text file was called “hosts.txt”. This was unsustainable as the number of domains on the Internet increased to millions. A USC researcher named Paul Mockapetris was charged with coming up with a solution in 1983.

His response was a brand-new system he called DNS, which continues to be built on Mockapetris' core ideas.

We all use the internet nowadays, meaning we must use the DNS or Domain Name System without realizing it. DNS or Domain Name System acts as the phone book of the internet. For computers, applications, or any resource connected to the Internet or a private network, Domain Name System (DNS) is a hierarchical naming system based on a distributed database. In short, it converts human-readable web addresses (domain names like www.monovm.com) to machine-readable numbers. (IP address like This system has been used for over 30 years and is still used today.  This seems very complicated and time-consuming, but it only takes less than 100th of seconds.

The ability to discover and connect devices everywhere in the globe is made possible, most importantly, by the translation of domain names readable by humans into the numerical identifiers associated with networking hardware. Like a network "phone book," DNS enables a browser to translate a domain name, such as "facebook.com," into the server's real IP address, which houses the data the browser seeks.

The computers, websites, and devices connected to the internet have a unique code known as the IP address. There are two types of IP addresses such as IPv4 (e.g., and IPv6 (e.g., FE80::0202:B3FF:FE1E:8329). Even though this looks very complicated, using the internet is very simple for everyone, thanks to the DNS server. The Domain Name System has a database of all the IP addresses, and it connects the domain names we provide with the respective IP address. There are four different servers which involve in loading a webpage:

  • DNS resolver: The DNS resolver acts like the delivery man responsible for taking the human-readable text (domain name) to be translated into the machine-readable text (IP). It takes all the user requests and delivers them to the Root name server. It is typically managed by the internet service provider (ISP).
  • Root name server: The root server (a root name server) initiates translating the readable texts into IP addresses. It also serves as a reference to other more specific locations. It can be thought of as telling the delivery guy in which store his product.
  • TLD name server: The top-level domain server (TLD) can be considered a specific aisle in the store. It is the next step in finding the requested IP address based on the top-level domain name (www.google.com; the top-level domain name is ‘com’)
  • Authoritative nameserver: This is the final step. It can be thought of as finding the product from the aisle and, if found, then returns to the user. If the authoritative nameserver has access to the requested record, it will return to the DNS resolver, sending the webpage to the user.

A computer known as a DNS server maintains a database on which all the public IP addresses associated with the names of the websites that an IP address sends a user to are stored.

DNS functions as an online phonebook. The DNS determines the correct IP address whenever users type domain names like Yahoo.com into the address bar of web browsers. The device is directed to the proper location to access the site's data by the IP address of the website.

When the DNS server discovers the right IP address, browsers transfer data to origin servers or edge servers of content delivery networks (CDNs). The user will then be able to access the website's information. Finding the corresponding IP address for a website's uniform resource locator is how the DNS server initiates the procedure (URL).

The function of a DNS server is to translate user input into a form that computers can use to locate a website. Alternatively, it converts a domain name, such as www.example.com, into a specific IP address, such as

DNS servers have eliminated the need for people to memorize lengthy IP addresses, such as, which is Google's IP address. They simply need to commit www.google.com to memory. Several hardware components are required for the translation process, which is referred to as DNS resolution. The primary DNS server is the most significant.

The primary DNS server is the first point of contact when a browser asks where to find a particular website. The so-called controlling zone file is present on the server. This file includes the IP address, contact details for the administrator, and Time to Live information for the DNS information for the requested domain. 

Time to Live, or TTL, describes how long (in seconds) a DNS record for a particular site will be valid in a local cache. The query is answered once the principal DNS server gives the browser the IP address of the requested domain.

The browser queries a backup DNS server if the primary server is down due to a power outage, hacking, hardware issue, or any other issue. A current version of the same DNS record will be stored on this server. Although secondary DNS servers are unnecessary for a DNS system to function, they are advised — and in some cases, required by domain registrars — because of this.

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There are three types of queries in DNS servers, and you can use the combination of these three queries to reduce the distance traveled for optimized processes in DNS resolutions. So here are the complete details on DNS queries: 

  • Recursive query: A DNS client needs the DNS server to respond to the client according to the error messages or requested resource record in case a resolver cannot find a record.
  • Iterative query: A DNS client administers the DNS server to return the best answer possible. If the queried DNS server doesn't have an appropriate match for a query name, it will return the referral to the DNS server authoritative for the domain namespace's lower level. A DNS client then makes a specific query to a referral address, and this process continues with the additional DNS server down that query chain until a timeout or error occurs. 
  • Non-recursive query:  This DNS query occurs when the DNS resolver client queries a specific DNS server for the record it can access if it's authoritative for a specific record or a record in its cache. Particularly, the DNS server will easily Cache the DNS record to prevent additional bandwidth usage and load on the upstream server. 

DNS resource record is a basic information element for any Domain Name system, so they are entries in a DNS database that offers information regarding hosts. All records are stored in the Zone Files at a DNS server, so these are some common DNS records: 

  • IP Version 6 Address records (AAAA): This type of record holds a specific hostname and corresponding IPv6 address.
  • Address Mapping records (A): These records hold a specific hostname and corresponding IPv4 address.
  • Canonical Name records (CNAME): These types of records are used for creating aliases of the domain name, and these can be used to alias the domain to the other domain.
  • Mail exchanger record (MX): These records specify a particular mail exchange server for a domain name and are used for the SMTP protocol to route emails to the correct email server.
  • Reverse-lookup Pointer records (PTR): These types of records are used for looking up domain names based on the IP address.
  • Name Server records (NS): These records delegate a DNS Zone for using a particular Authoritative Name Server.
  • Certificate record (CERT): These types of records work to store encryption certificates like PKIX, PGP, etc.

To check your domain DNS records, you can use DNS Lookup tools.

The DNS is in charge of translating the hostname, the domain name, the website, or the web page name into the IP address. A DNS query is the act of inputting the domain name, while DNS resolution is the process of determining the appropriate IP address.

Recursive, iterative, and non-recursive DNS requests are the three types that can be made.

  1. Recursive requests need the DNS server to provide the desired resource record in response. The DNS client must be informed of an error if a record cannot be located.
  2. Iterative queries are those for which the DNS client repeatedly asks several DNS servers for a response until the best answer is discovered, an error occurs, or a timeout occurs. A DNS server is authoritative for a lower level of the domain namespace and will be referred to if the DNS server cannot match the query. The DNS client then queries this referral address, which is repeated with further DNS servers.
  3. Non-recursive requests are those that a DNS resolver answers when the resource is present, either because the server is authoritative or because the resource is already cached.

The use of a DNS server has a lot of advantages. The most significant are as follows:

  • DNS servers enable you to search for websites by entering their domain rather than their IP address.
  • They provide your network with an additional degree of security.
  • Online transactions would be impossible without DNS servers.
  • The DNS server will detect changes to a website's IP address and automatically update its database, keeping users unaffected.
  • Because DNS servers are quick at what they do, consumers experience minimal downtime.

Without involvement from the end user, a DNS query is sent via several separate data center servers before being resolved.

1. Recursive DNS 

This server was created primarily to answer inquiries from client computers. It locates the DNS record and issues further requests to respond to the client's DNS requests. When the requested resources are returned to the precursor early in the query process, DNS caching can reduce the number of queries.

This DNS server receives a URL that users type into their web browser. The IP address for the URL is then checked to see if the recursive DNS server has already saved it by looking through its cache memory. The recursive DNS server will provide the IP address to the browser if the IP address data is already available. The user can then access the website they entered the URL for.

2. Root name server

This service handles the task of converting human-friendly hostnames into computer-friendly IP addresses. Depending on the domain name found in the query, the root server approves the precursor's request and sends it to the TLD nameservers in the following stage.

3. Top Level Domain (TLD) nameserver

The information regarding the domain names is kept up to date by the TLD name servers. They might include details about websites with ".com" or ".org" extensions or those with country-specific domain names like "www.example.com.uk," "www.example.com.us," and others. 

The TLD nameserver will receive the query from the root server and direct it to the appropriate authoritative DNS nameserver for the domain in question.

Authoritative nameserver

You can only receive an accurate response to a DNS query from an authoritative nameserver. A master server, also known as the primary nameserver, and a slave server, also known as the secondary nameserver, are examples of authoritative nameservers. 

The slave server is an exact replica of the master server, but the master server retains the original copies of the zone records. If the primary DNS server malfunctions, it serves as a backup. Authoritative DNS servers handle regions like a state, an organization, or a locality. 

Any region covered by an authoritative DNS server performs two crucial tasks. First, the server maintains lists of domain names and associated IP addresses. The server then answers queries from the recursive DNS server asking for the IP address with a certain domain name.

DNS queries can also be answered by recursive resolvers using cached information. After obtaining the proper IP address for a specific website, the resolver will then save that data in its cache for a finite period. 

If additional clients request that domain name during this time, the resolver can respond to the client with the IP address stored in the cache rather than performing the usual DNS query. The resolver must obtain the IP address again after the caching time limit has passed to add a fresh entry to its cache. 

The DNS records for each site expressly define this time restriction, often known as the time-to-live (TTL). The TTL typically ranges from 24 to 48 hours. Web servers frequently change their IP addresses. Therefore resolvers cannot continuously serve the same IP from the cache, necessitating a TTL.

Some of the most popular DNS servers are listed below:


This is an easy-to-use DNS service with instructions for all of the most well-liked operating systems, including Mac, Windows, Android, iOS, and Linux. Adult content can potentially be blocked by users using Cloudflare's service.

Google Public DNS

In contrast to Cloudflare, Google Public DNS is geared toward people who are more technically savvy. But if you need them, you can locate tutorials.


The DNS solution from Quad9 is well known for its quick response times. A further claim is that it uses threat intelligence data to block harmful websites.

You could notice a message telling you that your DNS server is not responding from time to time since DNS servers occasionally run into issues.

This could be caused by several things, such as a slow internet connection, an out-of-date browser, a server-side power loss, or even incorrect DNS settings. The good news is that there are numerous approaches you can take to address this.

  1. Change your browser. Try Firefox or Opera instead of Google Chrome if the issue persists.
  2. Turn your firewall off momentarily. While firewalls are crucial for defending your computer from malicious DNS assaults, they do tend to impede your network connection. After turning it off, please return to the page you had trouble connecting to. You know the firewall settings must be adjusted if the website loads without issues.
  3. Reset your DNS configuration. To resolve DNS server difficulties, try clearing your DNS cache as a last resort.

Browsers can access websites and other internet resources using their IP addresses, which are translated into domain names by a Domain Name System (DNS). Every internet-connected device has an IP address that other devices can use to find it. 

People don't need to memorize a long list of IP numbers because they can type in the website's name, and the DNS will determine their IP address. The Domain Name System is like the white pages of the internet. Like how a phonebook links people to their particular phone numbers, the DNS connects a website name to its corresponding IP address.

To ensure the quickest and most dependable web browsing experiences, learning how to resolve DNS server issues and your best service options is critical.

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Babak Nasiri

Babak Nasiri

I am Babak Nasiri, the co-founder and CTO of Monovm. With a strong background in computer engineering, I have guided our company's technical direction and led the development of advanced virtualization solutions. I am committed to making a positive impact on society and have received recognition for my contributions to the virtualization and cloud computing sectors. Together with our team, we strive to revolutionize technology and provide high-performance virtual machines as a trusted technology provider.