By Dr. Philip Baczewski, Associate Director of Academic Computing
This is the second in a series of "Back to Basics" articles. The first can be found here: "Back to Basics: DNS." - Ed.
Back to the Basics: Domain Names
Over the last five years, the term "dot-com" has entered into the common vocabulary. It is a designation for businesses which provide services or offer products for sale exclusively via the Internet. In the last year, the phrase "bankrupt dot-com startup" has become equally as common. The "dot-com" we say is derived from the ".com" suffix that is the end of most commercial sites' E-mail or Web addresses, that is, the very top level of their fully-qualified domain name (FQDN).
Domain names have been around since the early days of the Internet. The early standards were .mil -- military sites, .edu -- educational institutions, .gov -- government sites, .org -- non-profit organizations, and .com -- commercial entities. A bit later, .net came into being to indicate networks and network organizations and .int was created for organizations established by international treaties between governments. A domain name applies a human language appellation to an address on the Internet and also provides a way to categorize the function of that address.
Fully qualified domain names
To make a fully qualified domain name, you start with the top level suffix, such as .edu, and prepend qualifiers as you need them. For example, the primary domain for the University of North Texas is "unt.edu". Prepend an additional descriptor and you've got an FQDN -- www.unt.edu is UNT's Web server address, ftp.unt.edu is UNT's ftp server address, and eaglemail.unt.edu is the address of UNT's EagleMail student E-mail service. An FQDN can be a simple way to indicate the what, the where, and the why of a particular online service.
An FQDN always maps to a specific numeric address that represents a computer on the Internet (see last month's column for more on how this actually happens). In large networks like UNT's, FQDNs are usually hierarchically organized to match the organization of the institution: cc.unt.edu is used for network addresses in the Computing Center, while cas.unt.edu is used for addresses in the College of Arts and Sciences, etc.
FQDNs usually include no more than four parts. They can have more, but beyond four, it gets harder to keep track of all the pieces. Also, since numeric addresses have four parts, there is a tendency for FQDNs to match that level of hierarchy (this is a human rather than technical tendency). For example, sol.acs.unt.edu matches 184.108.40.206. Since the numeric address hierarchy is the reverse of the FQDN, we can see that unt.edu maps to 129.120, acs maps to 220, and 42 is specifically the computer named "sol."
The number of domains has dramatically increased since the inception of the Internet. For one thing, as the Internet became international, country Top-Level Domains (TLDs) were created. These correspond to the name of the country and are two-letter designations like .us for United States, .ca for Canada, .uk for the United Kingdom, .de for Germany, etc. The small south Pacific island country of Tuvalu has increased it's coffers by selling the rights to it's country TLD which happens to be ".tv".
In addition to the country TLDs, several new general domains have been either proposed or already implemented: .aero, .biz, .coop, .info, .museum, .name, and .pro are all in various stages in the approval process. The newest domains which are already available are .biz and .info. As you might expect, .biz is specifically for businesses, but .info can be for any site which is intended to provide information (which is a pretty wide category). The other TLDs are fairly obvious, except maybe for .aero, which is specifically for the air travel industry, and .pro, which is intended for professions such as doctors, lawyers, accountants, etc. The .name domain may become one of the most popular. It is specifically for individuals to obtain an address which is your name, such as john.smith.name.
With all of these new and old domains around the Internet, you know that somebody's got to be in charge of it all. Generally, that responsibility falls upon the Internet Corporation for Assigned Names and Numbers, otherwise known as ICANN. ICANN is a non-profit organization that took over the name and address management functions of the Internet from the U.S. Government and its contracted organizations. ICANN has oversight of the approval of new TLDs, provides an accreditation service for domain registrars, and runs the root-level servers which ultimately can point to where to find what FQDN goes with what numeric Internet address.
If you want an address to use exclusively for your business, organization, or even your personal use, you must register a name that is unique within your desired domain. There are a number of accredited registrars which can be found on the ICANN Web site (www.icann.org) and for a small fee (usually $25-$35 per year), they will verify that the name is available and register it on their site along with the appropriate contact information and Internet addresses. Usually, you will only register a domain name if you have an Internet address that it can point to. Some Internet Service providers will sell this to you as a package along with Web space and other services. On the other hand, if you have acquire a fixed Internet address from a service provider, you can register a name to point to that address, and assuming it's OK with your provider, you can set up your own network and servers using the domain name.
One of the more annoying "businesses" which have appeared in recent years has been "virtual real estate" or perhaps more accurately, "cybersquatting." Essentially, someone or some organization will register names which it thinks will be popular or which are similar to known products or organizations. They will then offer to register it or give up the name for a fee. Most accredited registrars have name dispute resolution procedures in place to ensure that someone else cannot use a name which is copyrighted by someone else, however, in some cases it may be necessary to go to court to prove such name ownership. ICANN has created a Domain-Name dispute resolution policy (http://www.icann.org/udrp/udrp.htm) which most accredited registrars must follow when a conflict exists.
The privatization of domain name management via the creation of ICANN and other organizations has resulted in the expansion of the domain name space with an increasing number of top-level domains from which to choose. It has also provided for competition in registration services which has resulted in a slight lowering of the average cost of a registered domain. You may never need a domain name for yourself, but the trend is now to make domain names even more descriptive by adding TLDs like .biz or .info. I am guessing, however, that just like Herseys (tm) bar or Kleenex (tm), it will be a long while before "dot-com" disappears from our language.