Q: How does a DNS server work?
- Ben
A: The domain name system is a global network of servers that translate host names like www.hotwired.com into numerical IP (Internet Protocol) addresses, like 204.62.131.129, which computers on the Net use to communicate with each other. Without DNS, we'd all be memorizing long numbers instead of intuitive URLs or email addresses. And that wouldn't be much fun, would it?
As you might guess, the domain name system is fairly complicated; in fact, there are entire books on the subject. I can give you a simple overview, but if you want to learn more, there are several good resources on the Web.
First, a little history
Paul Mockapetris designed DNS in 1984 to solve escalating problems with the old name-to-address mapping system. The old system consisted of a single file, known as the host table, maintained by the Stanford Research Institute's Network Information Center (SRI-NIC). As new host names trickled in, SRI-NIC would add them to the table - a couple times a week. Systems administrators would grab the newest version (via FTP) and update their domain name servers.
But as the Net grew, the host table became unwieldy. Though it worked fine for name-to-address mapping, it wasn't the most practical or effective way to update and distribute the information. And since the stability of the rapidly growing Internet was at stake, Mockapetris and some other folks decided to find a better way.
Enter DNS. The great thing about the domain name system is that no single organization is responsible for updating it. It's what's known as a distributed database; it exists on many different name servers around the world, with no one server storing all the information. Because of this, DNS allows for almost unlimited growth.
The domain name space
In order to understand how a DNS server works, you should be familiar with what is called the domain name space. It sounds a little ominous, I know, but really it's quite simple. In fact, you've probably seen it at one time or another represented by an inverted tree that looks something like this:
![[Tree]](/geektalk/97/03/stuff/dns.gif)
Each node on the tree represents a domain. Everything below a node falls into its domain. One domain can be part of another domain. For example, the machine chichi is part of the .us domain as well as the .com domain. You'll see why this is important in just a minute.
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