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What is DNS? How does Domain Name System work?

Without DNS, there is no Internet. It is the key ingredient that makes domain resolving possible. We use DNS to access sites, send and receive emails when we use applications. All-day, every day! 

Domain Name System – DNS

DNS or a Domain Name System is an amazing technology. You can see DNS as a hierarchy system of domains/hostnames and IP addresses. It helps us open internet addresses without a hustle. We easily write the domain name and the DNS has the job to find the IP of the domain we wrote. Just like the phone book on your mobile phone, you need to find Mike, so you write “Mike”, and you don’t need to remember his actual number, great isn’t it?

DNS is an essential part of the Internet. It manages to translate all the inquiries into IP addresses, and like this, it can identify different devices that are connected to the network.

Apart from translating hostnames to IP addresses (A and AAAA DNS records), DNS also has many different functions like defining port in use, connecting services to domains, authentication of emails, and many more. There are 50+ types of DNS records with different functionality.

DNS serves for 

  • Matching hostnames to IP addresses
  • Pointing services 
  • Directing messages to mail services
  • Authentication and validation of emails and different services
  • Creating VPN
  • Creating a content delivery network
  • Load balancing
  • Increase your uptime
  • And more. 

DNS history

Before the Internet, there were different networks like ARPANET, SATNET, and many packet radio ones. The problem was that there was not a single united network. There was a need to solve this problem, and the solution was the Domain Name System (DNS). 

The person who got the task to create it was Paul Mockapetris. His team needed to find a way to have IP addresses and hostnames aligned. 

A centralized file called HOSTS.TXT matched the first existing sites to IP addresses, but this was not a solution that could handle millions of sites.

After several years of work, in 1983, the DNS was created and joined the Internet Standards of Internet Engineering Task Force in 1986. The founding documents of it were RFC 1034 and the second RFC 1035. There you can find information about the protocol, its functionality, and data types. 

A later update of DNS allowed dynamic zone transfers (IXFR) and the use of NOTIFY. The NOTIFY mechanism gave the Primary DNS servers the power to “notify” the Secondary about the changes in the DNS records. 

Now the Secondary DNS servers could update when a change occurs in the Primary and get only the change.  

And another critical moment was the creation of the DNSSEC and its version from 1999 (RFC 2535). It is a security layer that defends the DNS from poison attacks. 

Here you can read more about the History of DNS.

Components of DNS. What does DNS include?

  • Domain namespace. It is a tree-like hierarchy structure that divides hostnames into smaller pieces called domains. They are further divided into more categories: top-level domains, second-level domains, and subdomains. 
  • Authoritative DNS servers. Such a server has the main information – the zone file. It has all the DNS records, and all the changes to the records happen inside it. It has the most accurate information for a hostname.
  • Recursive DNS servers. Those servers will have a temporary memory where they store DNS records. They have a mechanism for synchronizing with the authoritative nameserver and updating the information. The advantage is that they can be many, located in different regions, and provide redundancy and speed. 
  • DNS query. Each request comes from a device that demands a DNS record. It is a question that runs from one recursive server to another in search of the answer. 
  • DNS records. Domain name system keeps information in so-called DNS records. They are text documents with various purposes like A Record, SPF record, CNAME record, etc. 

How DNS query works? Example

1. Information request
You want to visit our website and you know the domain name. You write it in your browser, and the first thing it does is to check for local cache if you have visited it before, if not it will do a DNS query to find the answer.

2. Recursive DNS servers
If you haven’t visited the page before, your computer will search the answer with your internet provider’s recursive DNS servers. They have cache too so you can get the result from there. If they don’t, they will need to search the information for you in another place.

3. Root name servers
Your query can travel a long way. The next step is the name servers. They are like intermediates; they don’t know the answer, but they know where to find it.

4. Top-Level Domain (TLD) name servers
The name servers will read from right to left and direct you to the Top Top-Level Domain (TLD) name servers for the extension (.com or another). These TLD servers will lead you finally to the servers which have the right information.

5. Authoritative DNS servers
These DNS servers check the DNS records for the information. There are different records, for example, we want to know the IP address for a website, so our request is Address Record (A).

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6. Retrieve the record
The recursive server gets the A record for the website we want from the authoritative name servers and stores it on its local cache. If somebody else needs the host record for the same site, the information will be already there, and it won’t need to pass through all these steps. All this data has an expiration date. This way, the users will get up to date information.

7. The final answer
Now that the recursive server has the A record it sends it to your computer. The PC will save the record, read the IP and pass the information to your browser. The browser makes the connection to the web server, and it is finally possible for you to see the website.


It is a long process, but actually, it takes fractions of a second. It can be even faster if you use reliable DNS servers from ClouDNS. Check our DNS services and choose the one that best suits you.

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