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Encyclopedia > Domain name

The term domain name has multiple related meanings:

  • A name that identifies a computer or computers on the Internet. These names appear as a component of a Web site's URL, e.g. en.wikipedia.org. This type of domain name is also called a hostname.
  • The product that domain name registrars provide to their customers. These names are often called registered domain names.
  • Names used for other purposes in the Domain Name System (DNS), for example the special name which follows the @ sign in an email address, or the Top-level domain names like .com, or the names used by the Session Initiation Protocol (VoIP), or DomainKeys.
  • They are sometimes colloquially (and incorrectly) referred to by marketers as "web addresses".

This article will primarily discuss registered domain names. See the Domain Name System article for technical discussions about general domain names and the hostname article for further information about the most common type of domain name. A website, Web site or WWW site (often shortened to just site) is a collection of webpages, that is, HTML/XHTML documents accessible via HTTP on the Internet; all publicly accessible websites in existence comprise the World Wide Web. ... // Uniform Resource Locator (URL) formerly known as Universal Resource Locator, is a technical, Web-related term used in two distinct meanings: In popular usage and many technical documents, it is a synonym for Uniform Resource Identifier (URI); Strictly, the idea of a uniform syntax for global identifiers of network-retrievable... A hostname (occasionally also, a sitename) is the unique name by which a network attached device (which could consist of a computer, file server, network storage device, fax machine, copier, cable modem, etc. ... A domain name registrar is a company accredited, either by the Internet Corporation for Assigned Names and Numbers (ICANN), or by a national ccTLD authority or both, to register Internet domain names . ... The Domain Name System (DNS) associates various sorts of information with domain names; most importantly, it serves as the phone book for the Internet by translating human-readable computer hostnames, e. ... E-mail, or email, is short for electronic mail and is a method of composing, sending, and receiving messages over electronic communication systems. ... “TLD” redirects here. ... The Session Initiation Protocol (SIP) is an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants. ... IP Telephony, also called Internet telephony, is the technology that makes it possible to have a telephone conversation over the Internet or a dedicated Internet Protocol (IP) network instead of dedicated voice transmission lines. ... DomainKeys is an e-mail authentication system designed to verify the DNS domain of an E-mail sender and the message integrity. ... The Domain Name System (DNS) associates various sorts of information with domain names; most importantly, it serves as the phone book for the Internet by translating human-readable computer hostnames, e. ... A hostname (occasionally also, a sitename) is the unique name by which a network attached device (which could consist of a computer, file server, network storage device, fax machine, copier, cable modem, etc. ...

Contents

Overview

The most common types of domain names are hostnames that provide more recognizable names to stand in for numeric IP addresses. They allow for any website to move to a different location in the topology of the Internet (or an intranet), which would then have a different IP address. A hostname (occasionally also, a sitename) is the unique name by which a network attached device (which could consist of a computer, file server, network storage device, fax machine, copier, cable modem, etc. ... An IP address (or Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. ... An intranet is a private computer network that uses Internet protocols, network connectivity to securely share part of an organizations information or operations with its employees. ...


By allowing the use of unique alphabetical addresses instead of numeric ones, domain names allow Internet users to more easily find and communicate with web sites and other server-based services. The flexibility of the domain name system allows multiple IP addresses to be assigned to a single domain name, or multiple domain names to be assigned to a single IP address. This means that one server may have multiple roles (such as hosting multiple independent websites), or that one role can be spread among many servers. One IP address can also be assigned to several servers, as used in anycast and hijacked IP space. Routing Schemes anycast broadcast multicast unicast Anycast is a network addressing and routing scheme whereby data is routed to the nearest or best destination as viewed by the routing topology. ...


Hostnames are restricted to the ASCII letters a through z (case-insensitive), the digits 0 through 9, and the hyphen, with some other restrictions. Registrars restrict the domains to valid hostnames, because they otherwise would be useless. The Internationalized domain name (IDN) system has been developed to bypass the restrictions on character allowances in hostnames, making it easier for users of non-English alphabets to be used on the Internet. The underscore character is frequently used to ensure that a domain name is not recognized as a hostname, as with the use of SRV records, for example, although some older systems such as NetBIOS did allow it. To avoid confusion and for other reasons, domain names with underscores in them are sometimes used where hostnames are required. Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ... Example of Arabic IDN Example of Chinese IDN Example of Persian IDN Example of Greek IDN Example of Hebrew IDN Example of Ukrainian IDN An internationalized domain name (IDN) is an Internet domain name that (potentially) contains non-ASCII characters. ... An SRV record or Service record is a category of data in the Internet Domain Name System specifying information on available services. ... NetBEUI redirects here. ...


Domain names are often referred to simply as domains and domain name registrants are frequently referred to as domain owners, although domain names, technically, are leased from a registrar.


Examples

The following example illustrates the difference between a URL (Uniform Resource Locator) and a domain name: // Uniform Resource Locator (URL) formerly known as Universal Resource Locator, is a technical, Web-related term used in two distinct meanings: In popular usage and many technical documents, it is a synonym for Uniform Resource Identifier (URI); Strictly, the idea of a uniform syntax for global identifiers of network-retrievable...

URL: http://www.example.net/index.html
Domain name: www.example.net
Registered domain name: example.net

As a general rule, the IP address and the server name are interchangeable. For most Internet services, the server will not have any way to know which was used. However, the explosion of interest in the Web means that there are far more Web sites than servers. To accommodate this, the hypertext transfer protocol (HTTP) specifies that the client tells the server which name is being used. This way, one server with one IP address can provide different sites for different domain names. This feature goes under the name virtual hosting and is commonly used by Web hosts. HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ... In computing, a client is a system that accesses a (remote) service on another computer by some kind of network. ... It has been suggested that this article or section be merged into shared web hosting service. ... Web hosting is a service that provides individuals, organizations and users with online systems for storing information, images, video, or any content accessible via the Web. ...


For example, as referenced in RFC 2606 (Reserved Top Level DNS Names), the server at IP address 208.77.188.166 handles all of the following sites:

example.com
www.example.com
example.net
www.example.net
example.org
www.example.org

When a request is made, the data corresponding to the hostname requested is provided to the user.


Top-level domains

Every domain name ends in a top-level domain (TLD) name, which is always either one of a small list of generic names (three or more characters), or a two-character territory code based on ISO-3166 (there are few exceptions and new codes are integrated case by case). Top-level domains are sometimes also called first-level domains. “TLD” redirects here. ... ISO 3166-1 alpha-2 codes are two-letter country codes in the ISO 3166-1 standard to represent countries and dependent areas. ...


The generic top-level domain (gTLD) extensions are: A generic top-level domain (gTLD) is a top-level domain used (at least in theory) by a particular class of organization. ...

The country code top-level domain (ccTLD) extensions are: A generic top-level domain (gTLD) is a top-level domain used (at least in theory) by a particular class of organization. ... .biz is a generic top-level domain (TLD) intended for domains to be used by businesses; the name is a phonetic spelling of the first syllable of business. ... This article is about the generic top-level domain . ... .edu (education) is the generic top-level domain for educational institutions, primarily those in the United States. ... .gov is the generic top-level domain used by the United States federal government. ... .info is a generic top-level domain intended for informative websites, although its use is not restricted. ... .int is a generic top-level domain (gTLD) used on the Internets Domain Name System. ... .mil is the generic top-level domain for the United States Department of Defense and its subsidiary organizations. ... .name is a generic top-level domain (gTLD) intended for the use of individuals. ... This article is about the top-level domain . ... .org (organization) is a generic top-level domain (gTLD) used in the Internets Domain Name System. ... A sponsored top-level domain is a generic top-level domain proposed by an independent agency, with that agency establishing and enforcing rules restricting the eligibility of registrants to use the TLD. For example, the . ... .aero is a generic top-level domain (gTLD) used on the Internets Domain Name System. ... .asia is a generic top-level domain proposed by the DotAsia Organization, with the back-end registry to be operated by Afilias. ... .cat is a top-level domain submitted to ICANN for approval as a sponsored TLD. It would be used to highlight Catalan language and culture. ... .coop is a generic top-level domain intended for the use of cooperatives. ... .jobs is a top-level domain approved by ICANN on April 8, 2005 as a sponsored TLD as part of the second group of new TLD applications submitted in 2004. ... .mobi (also known as DotMobi) is a top-level domain approved by ICANN and managed by the mTLD global registry dedicated to delivering the Internet to mobile devices via the Mobile Web. ... .museum is a generic top-level domain (gTLD) used exclusively by museums, museum associations, and individual members of the museum profession, as these groups are defined by the International Council of Museums (ICOM). ... .pro (professional) is a generic top-level domain. ... .tel is a top-level domain submitted to ICANN for approval as a sponsored TLD. It would be restricted to internet communication services, and provide a supplement to the traditional numeric namespace for telecommunication services (i. ... .travel is a top-level domain approved by ICANN as a sponsored TLD in the second group of new TLD applications evaluated in 2004. ... .arpa is an Internet top-level domain (TLD) used exclusively for Internet-infrastructure purposes. ... . The initial letter is shown capitalized due to technical restrictions. ... There are several proposed top-level domains which have not yet been approved by ICANN, as of 2007: .berlin . ... .berlin (dotBERLIN) is a proposed new top level domain (TLD). ... . ... This article or section does not cite its references or sources. ... .bzh (dotBZH) is a proposed top-level domain for sites about the Breton culture and language. ... .cym (dotCYM) is a proposed top-level domain for sites written in the Welsh language. ... .gal is a proposed top-level domain for sites from Galicia, or related to this Spanish nationality. ... .sco (dotSCO) is a proposed top-level domain. ... .geo is a generic top-level domain proposed by SRI International to be used to associate Internet resources with geographical locations, via a system of georegistrars and georegistries with hierarchical addresses representing locations in a grid encircling the Earth. ... .mail is a generic top-level domain proposed by Spamhaus, but unapproved by ICANN. It would attempt to reduce the spam problem by creating addresses which have been authenticated as not belonging to spammers, and with verified contact information, paralleling the actual addresses (in other TLDs) of servers used to... .web is a generic top-level domain operated as an alternative registry, not in the official root, by Image Online Design since 1995. ... .post is Top-level domain submitted to ICANN for approval as a sponsored TLD. It would be restricted to the use of national and regional postal services, and private businesses that provide similar services. ... .xxx is a proposed top-level domain (TLD) intended as a voluntary option for sexually explicit sites on the Internet. ... .kids is a proposed top-level domain that its supporters hope would deter the spread of pornography to minors. ... .nato is a former Internet top-level domain. ... “TLD” redirects here. ... .example is a reserved top-level domain not intended for real use in the global DNS. It was defined in June 1999 by RFC 2606, along with . ... jhjhjh ... .localhost is a Reserved top-level domain never intended for actual use in the global DNS. Its reservation is to avoid misuse with the common localhost See also Reserved top-level domains RFC2606 - Reserved domains list and information Generic top-level domains .aero . ... .test is a Reserved top-level domain never intended for actual use in the global DNS. It was not one of the original top-level domains established in 1985. ... .bitnet was a pseudo-domain-style suffix used in the late 1980s when identifying a hostname not connected directly to the Internet but possibly reachable through inter-network gateways. ... .csnet was a pseudo-domain-style suffix used in the late 1980s when identifying a hostname not connected directly to the Internet but possibly reachable through inter-network gateways. ... .ip is a Pseudo top-level domain which is used to indicate that the rest of the hostname is either an IP address or a masked IP address. ... .local is a domain used by Apple Computers Bonjour protocol. ... .onion is a pseudo-domain-style address suffix (similar in concept to such endings as . ... .uucp was a pseudo-domain-style suffix used in the late 1980s when identifying a hostname not connected directly to the Internet but possibly reachable through inter-network gateways. ... In addition to the Internets main DNS root (currently consisting of 13 nominal root nameservers working in agreement with ICANN), several organizations operate alternative DNS roots (often referred to as alt roots). ... A country code top-level domain (ccTLD) is a top-level domain used and reserved for a country or a dependent territory. ... A country code top-level domain (ccTLD) is a top-level domain used and reserved for a country or a dependent territory. ...

A generic top-level domain (gTLD) is a top-level domain used (at least in theory) by a particular class of organization. ...

Other-level domains

In addition to the top-level, or root, domains, there are second-level domain (SLD) names. These are the names directly to the left of .com, .net, and the other top-level domains. As an example, in the domain en.wikipedia.org, wikipedia is the second-level domain. In the Domain Name System (DNS) hierarchy, a second-level domain is a domain that is directly below a top-level domain (TLD). ...


Next are third-level domains, which are shown immediately to the left of a second-level domain. In the en.wikipedia.org example, en is a third-level domain. There can be fourth- and fifth-level domains, and so on, with virtually no limitation. An example of a working domain with five levels is www.sos.state.oh.us. Each level is separated by a dot, or period symbol.


Domains of third or higher levels are also known as subdomains, though this term technically applies to a domain of any level because even a top-level domain is a "subdomain" of the "root" domain (a "zeroth-level" domain that is designated by a dot alone). In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is part of a larger domain. ...


Traditionally, the second-level domain has been chosen based on the name of a company (e.g., microsoft.com), product or service (e.g., gmail.com). The third level was commonly used to designate a particular host server. Therefore, ftp.wikipedia.org might be an FTP server, www.wikipedia.org would be a World Wide Web server, and mail.wikipedia.org could be an email server. Modern technology allows multiple servers to serve a single subdomain, or multiple protocols or domains to be served by a single computer. Therefore subdomains may or may not serve any real purpose.


Official assignment

ICANN (Internet Corporation for Assigned Names and Numbers) has overall responsibility for managing the DNS. It controls the root domain, delegating control over each TLD to a domain name registry. For ccTLDs, the domain registry is typically controlled by the government of that country. ICANN has a consultation role in these domain registries but cannot regulate the terms and conditions of how a domain name is allocated or who allocates it in each of these country-level domain registries. On the other hand, generic top-level domains (gTLDs) are governed directly under ICANN, which means all terms and conditions are defined by ICANN with the cooperation of each gTLD registry. ICANN headquarters ICANN (IPA /aɪkæn/) is the Internet Corporation for Assigned Names and Numbers. ... The AMS-IX mirror of the K root-server. ... A domain name registry, also called Network Information Centre (NIC), is part of the Domain Name System (DNS) of the Internet which converts domain names to IP addresses. ... A country code top-level domain (ccTLD) is a top-level domain used and reserved for a country or a dependent territory. ... A generic top-level domain (gTLD) is a top-level domain used (at least in theory) by a particular class of organization. ...


Domain names are often seen as being similar to real estate in that (1) domain names are virtual properties on which a website (like a house or commercial building) can be built and (2) the highest quality domain names, like sought-after real estate, tend to carry significant value, usually due to their online brand-building potential, use in advertising, search engine optimization, etc. Real estate is a legal term that encompasses land along with anything permanently affixed to the land, such as buildings. ... A typical search results page Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via natural (organic or algorithmic) search results for targeted keywords. ...


A few companies have offered low-cost, below-cost or even free domain registrations with a variety of models adopted to recoup the costs to the provider. These usually require that domains be hosted on their website within a framework or portal that includes advertising wrapped around the domain holder's content, revenue from which allows the provider to recoup the costs. Domain registrations were free of charge when the DNS was new. A domain holder (often referred to as a domain owner) can generally give away or sell infinite subdomains on their domain name. For example, the owner of example.edu could provide subdomains such as foo.example.edu and foo.bar.example.edu to interested parties. In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is part of a larger domain. ...


Abuses

As domain names became attractive to marketers, rather than just the technical audience for which they were originally intended, they began to be used in manners that in many cases did not fit in their intended structure. As originally planned, the structure of domain names followed a strict hierarchy in which the TLD indicated the type of organization (commercial, governmental, etc.), and addresses would be nested down to third, fourth, or further levels to express complex structures, where, for instance, branches, departments and subsidiaries of a parent organization would have addresses that were subdomains of the parent domain. Also, hostnames were originally intended to correspond to actual physical machines on the network, generally with only one name per machine.


However, once the World Wide Web became popular, site operators frequently wished to have memorable addresses, regardless of whether they fit properly into the structure; thus, because the .com domain was the most popular and memorable, even noncommercial sites began to obtain domains in that gTLD, and sites of all sorts wished to have second-level domain registrations even if they were parts of a larger entity where a subdomain would have been logical (e.g., abcnews.com instead of news.abc.com). A website found at ''http://www.example.org'' will often be advertised without the http:// and, in most cases, can be reached by just entering example.org into a web browser. In the case of a .com, the website can sometimes be reached by just entering example (depending on browser versions and configuration settings, which vary in how they interpret incomplete addresses). This article is about the generic top-level domain . ...


The popularity of domain names also led to uses which were regarded as abusive by established companies with trademark rights; this has become known as cybersquatting, in which a person registers a domain name that resembles a trademark in order to pr