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How Domain Names Work

"Is that hard to do?" Anita asked.

"The buying is easy, actually," I replied. "The hard part is finding the domain name in the first place. A few years ago, domain names were hot properties that sometimes sold for astronomical amounts. In 1999, for example, the business.com domain sold for $7.5 million, a huge price by any measure."

"Um, that's a bit out of my price range," Claude said quietly.

"Yeah, especially when you're a poor college student," Stef added.

"Don't worry," I assured them. "The dot-com boom fueled an incredible frenzy for high-visibility domain names, but the frenzy died when the boom went bust. You can actually buy a domain name for less than $10 these days. The problem is finding a name that somebody else doesn't already own. But we'll get to that later. First, we need to understand how domain names work."

What's a Domain Name?

Explaining IP Find a more detailed definition of the Internet Protocol address system, plus check your own IP address, at http://ipaddr.net/.

Every computer on the Internet has a numeric address called an IP address (Figure 4.1). IP stands for "Internet protocol." The Internet uses IP addresses to route data between computers. The routing can be done very efficiently because it's all based on numbers and computers excel at processing numbers.

Humans work better with names and symbols than numbers. While IP addresses are very practical and functional at the network level, they're not easily remembered. That's why domain names were created. As I explained to Claude before, a domain name is a public, human-readable name for a computer or a group of computers. When you type the name of a Web site into your browser, the browser uses the domain name to find the site's IP address. If I were to make an analogy to the public telephone system, I'd say that a domain name is like an entry in a telephone directory. The system for assigning and resolving domain names is called the Domain Name System, or DNS for short.

The Domain Name System delegates authority for managing domain names to different entities on the Internet. This delegation system is reflected in the domain names themselves, which are actually several names glued together (with periods) to form a complete address. In that sense, a full domain name (often referred to as a fully qualified domain name) works much the way a postal address works, except that domain names read left to right instead of top to bottom.

Internationalized Domains See [www.memwg.com/idn] for more information about the up- and downsides of using internationalized domain names.

Naming Rules

A valid domain name is almost any combination of English letters (A to Z), numerals, and hyphens. Each individual part of a domain name can be between 2 and 63 characters long. Uppercase and lowercase letters are equivalent, so [www.memwg.com] and [www.MEMWG.com] or even [www.MeMwG.com] all refer to the same domain (Figure 4.2).

Not too long ago, standards were developed to allow letters from non-English alphabets, such as accented French letters or Chinese glyphs, to appear in domain names. Such names are referred to as internationalized domain names. The software that runs the DNS cannot directly handle these names, however, and so Web browsers and other applications must encode the internationalized form into a machine-readable equivalent that uses only English characters. We'll stick to English-only domain names to keep things simple.

Top-Level Domains

The name on the extreme right in a full domain name is always a top-level domain, or TLD for short. The .com domain is the most famous, but today there are many top-level domains in existence.

List of Country Codes
Find a list of all the current country codes at [www.iana.org/cctld/cctld-whois].

Each country or territory has its own two-letter domain, for example, such as .ca for Canada and .fr for France. These are called country-code domains. Other top-level domains, like .info and .biz, are referred to as generic domains.

Each top-level domain-also known as a registry-is managed by an organization known as the registry operator. For country-code domains, the registry operator is often (but not always) a nonprofit organization or government agency. Registry operators for generic domains act under contract with the Internet Corporation for Assigned Names and Numbers (ICANN), the nonprofit corporation that manages the DNS on a worldwide basis (Figure 4.3). Only ICANN can authorize the creation of new TLDs.

Subdomains and Host Names

The registry operator maintains the official list of names that are associated with its top-level domain. These names are referred to as subdomains, because they are really subdivisions of the top-level domain (Figure 4.4). The subdomain is the name found immediately to the left of the top-level domain. (In fact, in a full domain address, any name to the left of another is a subdomain of the latter.) In the domain name peachpit.com, for example, peachpit is a subdomain of the top-level .com domain.

A subdomain can be further divided, but the registry operator isn't responsible for tracking those subdivisions-it delegates that responsibility to the organization (or individual) that registered the subdomain. A global corporation might subdivide its domain by geography or function, for example, in order to create domain names like us.somebigcompany.com or eng.someothergroup.com. Each subdomain is listed immediately to the left of its parent domain.

The final part of the full domain name, to the extreme left, is the host name, which identifies a specific computer (by IP address) within a domain or subdomain. Web sites conventionally use www as the host name, though any name that follows DNS naming rules is possible. The owner of the domain has complete control over the host names within the domain and over how IP addresses are assigned. Most domains define a default host for the domain, which allows you to drop the host name when browsing-this is why the Web address [http://peachpit.com] gets you to the same site as [http://www.peachpit.com]. The domain owner makes all of this information publicly available on computer systems that the parent domain can access.

DNS for Dummies Learn all about DNS rules and regs at [www.yellowclouds.com]/DNS.

In other words, finding the IP address that corresponds to a domain name is a lot like looking through the white pages for a phone number. First you find the right phone book (the top-level domain), then the right city (the subdomain), and then the name of the person or business you want to contact (the host name). This process is called domain name resolution, and your computer does it automatically whenever you ask it connect to another computer.

Accredited Registrars A list of ICANN-accredited registrars is at [www.icann.org/registrars/accredited-lis90]. Also see [www.memwg.com/registrars] for links to popular registrars.

Domain Name Registrars

In DNS parlance, a registrar is an organization that can make changes to a domain registry. Its primary function is to register names within a registry. This is a separate role from that of the registry operator, which is charged with running the registry. Sometimes the same organization performs both roles-this was certainly the case in the early years of the Internet-but these days registrars are usually separate companies. It's actually a more competitive model, because multiple registrars can be authorized to register names with the same registry. Registrars for generic TLDs are accredited by ICANN, while each national government holds the rights to the accredited registrars for country-code TLDs.

Registrars are businesses. They charge their users-the registrants-a fee for each name registered. The fees are charged on an annual basis: Registrants only rent the names they register, they don't get perpetual rights to them. Parts of these fees go to the registry operator for the maintenance of the registry. The rest is used by the registrar to support itself. The fees charged for domain registrations can vary widely from registrar to registrar, so it pays to shop around to find the best price and the best level of service you're comfortable with.

Name Expiration and Renewal

Names are registered for specific time periods like one or two years. At the end of that period, the name is said to expire and it returns to the registry's pool of unregistered names. You must renew a domain registration before it expires in order to guarantee continued rights to the name. Tracking the expiration date isn't usually a problem, because a good registrar will send you a reminder when a domain is about to expire-just don't ignore the reminders!

Unrestricted TLDs The .com, .info, .net, and .org generic TLDs have no restrictions on who can register names.

WHOIS Use dedicated sites like [http://whois.net] or [http://checkdomain.com] to look up registration data.

Note that, at some registries, registrants have to meet certain requirements before they can register a name. The .name registry, for example, is restricted to individuals, while the .pro registry is restricted to licensed professionals like doctors and lawyers. Country-code TLDs sometimes limit registrations to citizens or organizations of the country in question. Registrars are responsible for enforcing these rules, so be sure to check the rules for the TLDs you're interested in before spending too much time searching for a good name.

WHOIS and Privacy

All information contained in the DNS is public knowledge, including the names and contact information (including email addresses) of domain registrants. An application called WHOIS (a concatenation of "who is") can be used to query this information. Most registrars offer a WHOIS service on their sites (Figure 4.5).

If you value your privacy, you may want to take steps to protect or hide your identity when you register a domain name. Spammers monitor new domain registrations to find new email addresses to spam. I've even had hosting services phone me, after I registered a domain, to try to sign me up as a customer.

Protecting Your Privacy

Stef was especially concerned about the privacy aspect of registering a domain. "Too many weirdos out there, you know," is how she phrased it. I told her there are steps you can take to protect your privacy:

You can use a different address-Stef could use her father's address, for example.

You can give fake contact information, though the email address needs to be valid.

You can use a privacy service where someone acts as a middleman for you-many domain registrars offer this service.

Just be sure you understand the privacy ramifications of registering a domain name before you register.