What is DNS? A very basic primer

Queue the introduction.

As a 44-year-old nerd, I spent nearly 1/4 of my entire adult life working as a PHP programmer for large Internet registrar.  When things were slow or I was between projects, I also had the dubious honor of doubling as a third-level customer support guy who specialized in trying to resolve e-mail related issues.

Of all the millions of questions I ran across when dealing with the average mom or pop, one of the most common was “What in the heck is DNS?“.

DISCLAIMER OF THE WEEK: I’m not a DNS expert by any means, nor do I play one on TV, but in trying to help the thousands of customers who needed it over the years, I always found the following little analogy to be very helpful in getting the point across

In a sentence form…

“DNS is the wholly-automated Internet version of a telephone phone book.”

While summary statements like that are usually written at the end of an article, I thought it very important to get the idea of the phone book planted in your brain that from the get-go.

It’s the core little secret that high-paid techno-wizards want to complicate so that they can scare you into paying them more money.   Once you understand the analogy of DNS is like a phonebook for the Internet, the rest of this article will hopefully make a lot more sense.

By the way, DNS is just an easy way of saying “Domain Name Service“.

Ok, I’ll bite, how is DNS like a phone book?

Did you know that every time you connect to the Internet, the machine you are using — whether it’s an Apple, PC, iPad, netbook, notebook, or even Sony PS3 — is assigned a unique, one of a kind number to help identify it — and by extension, you?

That number, called an Internet Protocol address, or “IP number” for short. When you are on the internet, you are the only one on the entire planet with that number.

Just as a telephone number identifies your phone, that unique IP address identifies your computer to the world.

The only real differences are:

1. Unlike a telephone number, your computer’s IP Address might change each time you connect to the Internet,
2. Unlike a telephone number, you usually don’t even need to know what yours is.
3. You don’t have to give out your ip number to anyone for them to be able to find you on the web

Just for the record, an IP Address is made up of a series of up to 12 digits, spaced out between three decimal points.

It might look something like this;

192.168.000.001

IP numbers are also usuallly shortened to eliminate the extra zeroes, like 192.168.0.1, but hopefully you get the idea.

What the Domain Name System does — in essence — is match up a domain name (such as ebay.com) to the address of the physical machine which is hosting that web site.  On the Internet, there are literally tens of thousands of Domain Name Servers whose sole function it is to coordinate which machine has which domain names hosted on it.  I won’t get into the nitty gritty of how this is all done, because then we’d be into overtime and someone would have to buy me a donut.

Suffice to say that out of those tens of thousands of servers which are pretty irrelevant to this little confusing rant, there are only a handful of core DNS servers, called Root nameservers at the heart of the Internet.  This handful pretty much handles the entire Internet, which is really impressive if you consider how many computers, sites, people, and things to see that there are out there.

Getting back to the story…

In much the same way that you might call an operator, give her someone’s name and she give you that person’s telephone number in reply, the DNS system interacts with your computer to look up a site’s “number” without having to bother the nice lady.

It’s like this.  Let’s say you were wanting to do a little bit of shopping for your niece’s birthday and heard they had a sale on sweaters at Wal-Mart;

1. In your browser’s address window, you’d type in walmart.com
2. Your browser goes out to the root DNS servers on the internet and asks for (then receives) the IP address of the computer which serves (or easier said, “puts”) walmart.com out on the Internet.
3. Once your browser has that computer’s IP address, it opens up a direct connection to that address (like dialing the phone number) and says “hi, are you walmart.com?“
4. The server on the other end — if everything’s worked out the way it should — responds, “Why yes, don’t be silly, of course I’m walmart.com.  Here’s the page you’re looking for.”
5. walmart.com’s Web site is displayed on your screen.

If it’s so simple, what can possibly go wrong?

Hmm. That is an interesting question.  With tens of thousands of DNS servers out there, and redundant systems in place, you can never count out Murphy’s Law.

“Whatever can go wrong, will go wrong” - Murphy’s Law

95% of the time when you type in a site name and it won’t come up, it’s usually just that particular Web site’s server (or connection to the ‘net) is having trouble.

The other 5% could be anything from an idiot with a backhoe (a type of tractor that digs trenches) who cuts Internet cabling, to the server being too busy, to a mis-typed address on the keyboard.  When you consider the millions of Web sites out there which operate 99.999% of the time, you might begin to understand how miraculous it is that any of the Internet ever works at all.

I just wish the Postal Service was this reliable — Emmett Brown (aka “Doc”), “Back to the Future”

More nuts, then the elderly man exits, stage right..

In the proverbial nutshell, that’s both what DNS is, and how DNS really works.  The technical mumbo jumbo gets a little more tricky, but this isn’t an article for technoweenies.  It’s hopefully for the average mom and pop out there who get confused when their favorite site, or e-mail doesn’t work.

Below are several other articles written by people hopefully smarter than me if you’re really interested.

Otherwise, if you ARE said technoweenie and you see a mistake I’ve made in trying to explain this stuff, PLEASE let me know by comment below and I’ll make sure to include your comment to try and help the helpless.

Wayne Hunt
segwayne.com

BTW, This article was written over the course of a weekend, in it’s entirety, on my Apple iPad.
I used the Nuance “dictation” app to write most of it by translated voice, then the WordPress App (iPhone version)
to edit and post the article.  It wasn’t fun without a keyboard, but it was one of those things which
I felt NEEDED to be tried, at least once to prove a point.  Sorry for all the grammar and
other mistakes I’m sure.

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