What is a domain?

The term domain can refer either to a local subnetwork or to descriptors for sites on the Internet (e.g., www.indiana.edu).

Local subnetwork domains

On a local area network (LAN), a domain is a subnetwork made up of a group of clients and servers under the control of one central security database. Within a domain, users authenticate once to a centralized server known as a domain controller, rather than repeatedly authenticating to individual servers and services. Within a domain, individual servers and services accept the user based on the approval of the domain controller.

Indiana University's domain is ADS or ads.iu.edu. To be precise, IU runs an Active Directory, the most advanced type of domain for domain controllers running Windows 2000 or later. There are many administrative differences between Active Directories and earlier domain types, but for the user the experience is mostly the same.

Internet domains

On the Internet, a domain is part of every network address, including web site addresses, email addresses, and addresses for other Internet protocols such as FTP, IRC, and SSH. All devices sharing a common part of an address, or URL, are said to be in the same domain. In the address www.indiana.edu/people/address.shtml, indiana is the domain, people is a directory in that domain, and address.shtml is a file in the directory.

To obtain a domain, you must purchase it from a domain registrar. You can choose a registrar from the list of accredited registrars.

Internet domains are organized by level. Most people are familiar with the Top Level Domains (TLDs) of .com, .edu, .net, and .org. TLDs are the most general and basic part of the URL. There are actually many top level domains. Every country is assigned one; see the complete list of country code Top Level Domains (ccTLDs). Click the ccTLDs link in the top row of links.

Category domains called generic TLDs (gTLDs) are also available. These domains are described on the Internet Assigned Numbers Authority gTLD page. Click the gTLDs link in the top row of links.

The governing body for domain names is called ICANN (Internet Corporation For Assigned Names and Numbers), a non-profit corporation charged with overseeing the creation and distribution of TLDs.

Also see:

• In Active Directory, what are the differences between universal, global, and domain local groups?
• What is the purpose of the iu.edu domain?
• What is a fully qualified domain name (FQDN)?
• At IU, what is the Active Directory Services (ADS) Domain?