What Is Dns And What Does It Do?

DNS is the process by which URLs entered into a web browser may be converted to the IP numbers they signify.

DNS is an acronym signifying "Domain Name Server", "Domain Name Service" or (more rarely) "Domain Name System", depending upon who you ask. They all mean the same thing, naturally. Usually it is referred to more as a process than an actual individual server. You will hear it often in moderately technical reference to HTTP sites (that's what you probably know as the internet, for the uninitiated, though it could surely be said that the internet comprises much more than just websites). The DNS is what makes the internet sane, essentially--without it you'd need to know that www.whitehouse.gov (a URL) is really, which you almost certainly wouldn't.

That string of numbers is what's called an IP address, and it's the real location of a server on the internet. It's specific and it's generally static, and it's damned hard to remember. That's where our friend the DNS comes in. The process by which www.whitehouse.gov in your URL bar becomes is a little bit extensive, so let's see if we can't explain it systematically.

1. ) You type www.whitehouse.gov into your URL bar for whatever reason you might have (we don't ask questions, do we?).

2. ) Your browser does a quick check to see if you've been there before. If you have, you've got that IP address listed in a cache file on your machine as corresponding with the URL you just typed in, so it'll fill in the blanks and skip the rest of the steps. Let's assume you've never been there before.

3. ) If your cache doesn't know the IP, as we're assuming, your browser is going to have to check an external server for that information. The first server that gets queried is the "." nameserver, or the "root" nameserver. Root nameservers are the effective backbone of the DNS system--they exist so that everyone can find everyone else. These servers store IP information on all the .com, .net, .org domains, called "first level domains". Since we're interested in seeing a .org site, we're going to get back from the root nameserver an IP for the .org domain.

4. ) Now you've got this IP for .org. Your computer's going to query this IP for information concerning "whitehouse.gov" and it's going to (hopefully) get a response. Now, mind that this doesn't give you what you want yet. Whitehouse.gov probably has dozens of IPs connected to it, with names like applesauce.whitehouse.gov and deep-dark-secrets.whitehouse.gov. So you're going to have to talk to the head honcho of these IPs first, whitehouse.gov itself.

5. ) Now you're speaking to the boss, and he's telling your browser that www.whitehouse.gov is at IP This is what you want, and your browser will automatically point you here, using port 80 (which is the standard for HTTP communication). This will be the IP you contact for files like the ever-popular index.html, et cetera.

Convoluted as it may seem, much of the DNS system exists to keep you from wasting bandwidth, strangely enough. For instance, the caching system, described in the first step, tries to keep you from having to unnecessarily query nameservers when you might already have the DNS information on your hard drive. This is a process that takes milliseconds today, but which might've tied up modems for several seconds or longer in the earliest days of the internet. The system, despite its convolutions, does work quite well, and so long as all the nameservers stay up and running everything stays quite smooth, and any progression to a simpler system would require a great deal of redirecting and restructuring, one thing to which the basic infrastructure of the internet is hardly conducive at this point in time.

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