Domain name space is the architecture of organizing the human readable domain names that are associated with explicit numerical Internet Protocol (IP) addresses of servers using the Domain Name Service (DNS) system. Domain name space helps to associate higher-level domains with particular nations, uses or types of organizations.
History
The domain name system, and the initial domain name space, was defined in 1983 by RFC 882. However, common current top-level domains weren't defined until 1984 through RFC 920. Later RFCs defined more top-level domains, including national domains like .us, ca, .tw and .cn. Other newer top-level domains include .info and .name, among others.
Top-Level Domains
The basis of the domain name space is the top-level domain. Top-level domains are the right-most string of characters in a domain name. The most common top-level domain is .com, but .org, .net and .edu are among the earliest top-level domains. Initially, top-level domains were given according to the function of the organization. "Edu" was for educational organizations, .com for commercial entities, .org for non-profit organizations and .net for computing networks. Although the organizational type requirements are no longer enforced, most top-level domains indicate the purpose or location of the remainder of the domain name. For example, .gov indicates a governmental organization and .name indicates a personal website.
Second-Level Domains
With the initial seven top-level domains, the second-level domain is often the memorable company or organization name. For example, in barnesandnoble.com, the .com is the top-level domain, and barnesandnoble is the second level. In some cases, especially for sites that use a national top-level domain, the second-level domain may be similar to some top-level domains. For example, times.co.uk, the name space for the Times of London, uses .uk as the top-level domain. In the United Kingdom, commercial sites are given a .co second-level domain.
Third-Level Domains & Subdomains
Third-level domains are called sub-domains if they are associated with a .com, .org, .edu or one of the other original top-level domains. For example, a website with the name "website.com" can create sub-domains that point to different servers. Sub-domains might include catalog.website.com or payments.website.com. In places that use a second-level domain as part of the national domain structure, the third level of domain space, the "times" in times.co.uk, is the third-level domain. In those cases, a sub-domain might be editorials.times.co.uk, where "editorials" is the sub-domain.
Name Space Sorage
The domain name space creates usable domain names that are stored globally in many different DNS servers. When a computer wants to access a server associated with a domain, a request for the explicit IP address is made to one of these servers. The server sends the explicit address, and the requesting computer is able to connect to the server.