DNS resolution: Explained step by step

DNS resolution – What is it?

DNS resolution is triggered when you type a domain name into your browser. It is a process of translating the domain name into its corresponding IP address. 

There are some situations when a domain is possible to have many IP addresses, for instance, one IPv4 and one IPv6. Through the DNS resolution, both of them are going to be requested. On the other hand, it is enough to receive just one of the addresses if there are several to connect with the domain.

The necessity for quick translation appeared long ago. Previously every of the IP addresses was stored in a manually updated Host file. When at some point, the number of devices wanting to join the Internet increased, and this way of searching was not practical anymore.

Thankfully the Domain Name System (DNS) was established, and the Internet is simple to use as we know it now. The IP addresses are how machines communicate, and users just have to write the domain name and the website loads. We don’t even realize how fast it happens.  

How does it work, step by step?

DNS resolution has several operations, and what triggers this process is a user who wants to visit a web page, a domain name that was not visited before.

  1. The DNS query is made when the user writes a domain name inside the browser. Then, the DNS lookup process for finding the corresponding IP address begins.
  2. The DNS recursive server receives the query. The IP address could be its cache memory if the website was previously requested. Still, when it is not, the DNS recursive server is going to seek the answer through the rest of the DNS servers and finally supply the needed data. The Root server is the first place it will search.
  3. In the DNS hierarchy, the Root server is on the highest level. It provides information about the Top Level Domain (TLD), such as .com, .net, .info, .eu. and directs the query to the exact TLD server. 
  4. Next, the TLD server gives the DNS recursive server information about the proper nameserver for the searched domain name.
  5. The DNS recursive server questions the authoritative nameserver for the domain name’s IP address and successfully receives an answer.
  6. The recursive DNS server goes back to the user with the requested data. Additionally, it saves the IP address in its cache memory for later use.
  7. Finally, the browser loads the desired website, and the user is able to explore it.

The DNS resolution takes a lot of steps. Also, the DNS query has to go through several servers on the way. Yet, the user experiences all of it in just a short moment of waiting.

Why do we care about DNS resolution?

The DNS resolution matters for two reasons:

  • Speed. The first step when a user visits your website is the DNS resolution. If it takes a lot of time to load and access it, the user will probably leave your page. That is the reason why this process has to be quick.
  • Availability. The nameserver that is accountable for your domain name needs to be reliable. An additional DNS service is a great choice to make sure your domain will always be available for your customers.

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