Demystifying DNS

Telephone switchboard operators from the 1950's.

DNS—or Domain Name System—is one of those geeky terms that usually flies above the heads of people who aren’t entrenched in the world of websites and the Internet. Mostly because, for the most part, it’s invisible. It’s one of those crucial pieces of Internet infrastructure that usually just works without you noticing it, let alone thinking about it. But when it doesn’t work, bad things happen, or rather, good things don’t happen, like people finding your website. And if you’re about ready to launch your brand-new website, chances are you’ll have to make some DNS changes in order to get things working.


To explain how DNS works, I’m going to use an increasingly antiquated metaphor: that of a phone book. Just like you have a name, if people want to reach you (by telephone, that is), they need to know your telephone number. Just dialing your name into the phone doesn’t work. When I was a kid, we found out this information by using a telephone book: I would look up the name of my friend, and the book provided the number I could use to call her.

This won’t work.

DNS works in much the same way. Every website you want to visit has a name, but behind that name is one or more numbers that are the true location of where that name leads to. These numbers are called IP (Internet protocol) addresses, and consist of four groups of numbers that range from 0 to 255 and are separated by dots. (That’s IPv4, the most common standard. There’s also IPv6, but let’s ignore that today.)

So let’s go back to our phone book analogy. Looking up my friend’s phone number was easy since we lived in the same town. But what if I needed to look up somebody who lived in another state? Chances are, I didn’t have that phone book just lying around. I’d either have to call information, or go to the library and hope they had a copy of the appropriate book. And how did the library have it? By sending away to various cities to get them.

And that’s a bit how DNS works, too. There is one place per URL, called the “name server,” on all the Internet that holds the key numbers for any particular name on the Internet. Who the name server for a particular URL is is so important that it’s provided along with other basic information such as the URL’s owner and registration service (or registrar). But then that information propagates to Internet providers (your Verizons, your Comcasts, your Time Warners, etc.) all around the world. Any time there’s a change, the change has to work its way throughout the Internet in a process that could take a little as one hour or as long as five days.

Time to Live

Why the difference in time? Along with the information regarding what URL has what number, the name server also tells other servers around the world how often to check back for new information. This is called the “Time to Live” (or TTL), and the shorter the TTL, the more frequently Internet providers and other servers check back to see if any information has changed.

So when you’re getting ready to launch a website and know you’re going to need to change the DNS, you need to do some planning ahead of time. You can usually change the TTL to something shorter than the default, and so it’s best to do so at least a week ahead of time. Then, when you’re ready to launch, make the change, and once the change has made its way throughout the Internet, you can change it back to the longer TTL value.

Changing the DNS Information

How do you change the DNS? Good question, but there’s no one answer. Often, you manage DNS settings on the same site where you registered your URL. But sometimes, it’s with your web host. Which could be the same provider, or could be different. Sometimes the interface to update your DNS is very simple, but the provider will try and upsell you on a bunch of stuff you don’t need. Other services have complex interfaces that you practically need a computer science degree to edit. In short, if DNS changes are required to launch your site, it’s best to have a professional handle it.

Hopefully I’ve been able to shed a little light on DNS. Have more questions on this or how other parts of the Internet work together, let me know in the comments or send me feedback!

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