When you type a website into your browser, it’s easy to take the fully qualified domain name (FQDN) for granted. But behind that simple name lies a complex hierarchy of servers and domains that make up the internet. In this article, we’ll deconstruct an FQDN and explain what each part means.
Let’s start with an example: www.mypage.com. The FQDN consists of four parts: www (the host name), mypage (the domain name), com (the top-level domain), and the root domain. The root domain is represented by a hidden dot at the end of the FQDN, which is built into every DNS system on every computer.
At the top of the internet pyramid are the 13 root domain servers. While they used to be physical machines, today each of the 13 is a conglomeration of servers spread all over the world. Each computer has a list of those 13 root domains built into its DNS system.
The next level is the top-level domain, such as .com, .edu, or .mil. There are over 100 different top-level domains in use on the internet. These are second-level servers, with the root domain being the first.
The third level is the domain name, which is the name you or I might purchase. Finally, we have the host name, which is the name of the computer or server that hosts the website. In the case of www.mypage.com, “www” is the host name.
But the FQDN can go even further. For example, we can replace “www” with “finance” to get finance.mypage.com. This is the name of a computer or server that is hosting a specific part of the website. We can even add subdomains, such as charts.finance.mypage.com, to create a hierarchy of servers and domains.
In conclusion, a fully qualified domain name is a hierarchical system of servers and domains that make up the internet. Understanding how it works can help you troubleshoot DNS issues and better understand how websites are hosted.