What are DNS Resolvers and How Do They Work?

This short post is about how a DNS resolver works. I also quickly cover the best way to obtain a DNS resolving service.

Please note that I am not going into the specifics on how to setup a DNS resolver. There are plenty of online tutorials for you to follow if you wish to pursue that option.

What is a DNS resolver? Simply put, a DNS resolver contacts a domain name’s DNS server and asks it for information.

A DNS resolver will also do something called caching. When a DNS resolver caches, it is “remembering” the information it previously obtained from a DNS server.

A DNS resolver that caches can save a lot of time that would be wasted looking up a domain name that had just been looked up earlier.

DNS caching is like writing down information on a sticky note, so you can quickly look at it later, instead of having to ask the person for the info all over again.

Here is a simplified example of how a DNS resolver works:

1.   Alex types into his web browser example.com

2.   Alex’s web browser then contacts the DNS resolver (that his computer is set to use).

3. The DNS resolver goes to a root server and get the IP address for the TLD (e.g., com, net, org, etc.) server it needs to access.

3.   The DNS resolver then goes to ns1.example.com (the DNS name-server that the TLD server provided), and asks the name-server for the IP address of example.com

4.   The DNS resolver then relays the information it receives to Alex’s computer. In addition, the DNS resolver caches the retrieved information for later use.

5.   Alex’s web browser now knows where example.com is located (the IP address), and starts retrieving the website.


Posted in Computers, Internet and Servers, Operating Systems