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Authoritative DNS Servers vs. Recursive DNS Servers

If you aren’t sure what DNS is, you must start at the beginning.

This article: What is DNS will help you understand the basics. Read it over and then come back. That will help give you a basic understanding of DNS before we dive into the more technical stuff.

What is a Recursive DNS Server?

Every website is assigned a unique IP address. As you already know, DNS translates the websites domain into the corresponding IP address, but HOW does it do it?

When you type a website address into your browser, like google.com, your browser needs to be able to translate that URL into the correct IP address of the website in order to access that website. To do this, your web browser sends out a DNS query.dns meme Your browser sends the query to a recursive DNS server. The recursive DNS server could be hosted at your ISP (Internet Service Provider, or if you are using a 3rd party DNS provider, it will be directed there)

The designated recursive DNS server then queries the Root DNS server for the Top Level Domain (TLD) of the domain you are trying to reach in this case, google.com, .com is the TLD. Since it is .com, it asks the .com TLD root DNS servers for the Authoritative name servers. In response, the authoritative name servers resolve the domain.

The Root DNS servers then send the recursive DNS server to the Authoritative DNS server that is responsible for that domain and then returns the corresponding IP address of the website. You are then able to access the requested site. This entire process happens within a fraction of a second.

This is assuming that the domain or hostname isn’t cached. The hostname or domain can be cached in a few spots along the way on your browser, your computer’s DNS resolver, or from your recursive DNS provider.

What is an Authoritative DNS Server?
Authoritative DNS servers are the servers that give answers to the recursive DNS servers. The answer they give is the essential DNS information for each website (corresponding IP addresses, a list of mail servers and other necessary DNS records.) The authoritative DNS servers are often where the website is hosted, if the website is using a managed DNS provider, the DNS provider is the authoritative DNS server. So, in short, authoritative DNS servers are the servers that give the recursive DNS servers the correct answers in order for the recursive DNS servers to allow you to access the website you are trying to access.

Why does this matter?
If Recursive DNS servers and Authoritative DNS servers didn’t exist, you would need to know the IP address of every single website that you would like to visit. Currently, most websites are still hosted on IPv4 addresses, which are 32-bit, but are quickly being replaced by IPv6 addresses which are 128-bit. Remebering the IP address of every website that you would like to visit could prove to be extremely difficult.

So in short, DNS makes the Internet easy. I love DNS! Share with your friends and family if you love DNS and how easy it makes the Internet to navigate.

One Comment.
  1. Paul

    I think you got it wrong man. A root server DOES NOT respond win a recursive manner but iterative.

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