What Exactly is DNS and What Does It Do?

[WHB - Tyler]

The Domain Name System (DNS) is an essential element of the Internet, responsible for tying a domain name to the IP address where that domain resides. Since humans can only memorize so many twelve digit IP addresses (for example: 127.243.238.123), DNS was created as a way to take that IP address and create a unique human-identifiable name to be related with it. Because of DNS, you can type “google.com” into your browser and it magically finds the Google server.

It comes in handy to thoroughly understand the DNS system because you use it constantly as a web developer or server owner, so let’s take a moment to see how this process works.

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[Alan B]

Tyler:

Good article. Just one paragraph that you may want to expand and clarify.

myth among internet users is that DNS has to magically “propogate” from one server to another, populating all across the world, which can take hours.

Propagation is, of course, not a myth. Your point may be that DNS Zones don't need to propagate to every server. Also, it's true that servers cache DNS lookups in order to minimize lookups and respond to DNS requests more quickly.

However, DNS data cannot be cached if it did not previously exist. A newly-registered domain must propagate. Also, caches may contain outdated data if changes have since been made to a DNS Zone. Major changes to an existing DNS Zone, such as changing nameservers or IP address of the A record when moving to a new host or new server, must propagate. That propagation can take hours or days, depending upon the SOA values previously set in the DNS Zone, the frequency with which resolver servers refresh their caches, and other factors.

Propagation delays are a major source of confusion and frustration amongst hosting clients, because many clients do not understand that DNS changes and registration are not instant. We often see clients in these forums complaining that their domain is not resolving to their brand new WHB hosting account, because they don't realize that they must allow for propagation. Your article would benefit from an explanation of this fact.

[WHB - Tyler]

I will do some additional research into this and revise the article to reflect your suggestions