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Understanding DNS Servers: How a Web Address (URL) becomes a Web Page

Suppose you want to visit the InformIT Web site. You, the Web surfer (S), type http://www.InformIT.com —more formally known as a Uniform Resource Locator or URL—into the Address or Location box of your browser (B) and then press the Enter key on your keyboard (step 1). If you typed the URL correctly, a (hopefully nicely formatted) Web page appears on your computer screen (step 2). Figure 1 shows this process.

Figure 1

How a URL becomes a Web page (naïve information activity map).

If you feel the map in Figure 1 is incomplete, you're right. The Web page doesn't magically appear. The browser has to request the page from the InformIT Web site (W) (see step 2 in Figure 2). The Web site sends the HTML within the file to your browser (step 3) and your browser formats the HTML into a nice page, which is what you see on your screen (step 4).

Figure 2

How a URL becomes a Web page (Web surfer's information activity map).

For a Web surfer, the information activity map in Figure 2 is sufficient; anything else is TMI (see my last article's hacker phrase). However, we Web entrepreneurs need an even more complete map—one that shows how the Domain Name Service server (DNS server) fits in.

The best offline analogy for a DNS server is a phone book. If you want to call someone on the phone, you need his or her phone number, which you typically get out of a phone book. Similarly, when your browser wants to talk to a Web site, it needs that Web site's numeric address, which is technically called the IP address; it's represented as four numbers in the range 0–255, separated by dots. So, for example, the IP address for www.informit.com is 64.29.203.103. Your browser actually understands IP addresses; typing http://64.29.203.103/ into your browser takes you to the same Web page as http://www.informit.com/ (go ahead and click on both links—just use your browser's Back button to come back here after clicking each link!).

Figure 3 shows the more complete map of what happens: you (S) type the address (URL) of a Web site (W) into your browser (B) and press Enter (see step 1). Your browser requests the IP address for W from a DNS server (D), as shown in step 2. D returns the IP address to B (step 3), which then requests the home page—or whatever page is specified in the URL—from W (step 4). W returns the raw HTML for this file to B (step 5), and B formats the HTML into the nice Web page you see on your screen (step 6).

Figure 3

How a URL becomes a Web page (Web entrepreneur's information activity map).

Of course, if you're a Web/network administrator, you need an even more complete map—one that shows how your browser knows the address of the DNS server in the first place. But for us Web entrepreneurs, the map in Figure 3 is sufficient.

As you can see, the DNS server (D) plays a key role in your users' (S) finding your Web site (W). You need to know the Web address—specifically, the fully qualified domain name—of your DNS server, as well as its IP address. Then go back to whatever Web site you used to register your domain name, and enter the information.

Just where do you get the address of your DNS server? The answer is from your Web hosting provider, which we'll examine next.

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