Domain name

Domain name

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Encyclopedia
A domain name is an identification string
String (computer science)
In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set or alphabet....

 that defines a realm of administrative autonomy, authority, or control in the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

. Domain names are formed by the rules and procedures of the Domain Name System
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

 (DNS).

Domain names are used in various networking contexts and application-specific naming and addressing purposes. In general, a domain name represents an Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...

 (IP) resource, such as a personal computer used to access the Internet, a server computer hosting a web site, or the web site itself or any other service communicated via the Internet.

Domain names are organized in subordinate levels (subdomains) of the DNS root domain, which is nameless. The first-level set of domain names are the top-level domain
Top-level domain
A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...

s (TLDs), including the generic top-level domain
Generic top-level domain
A generic top-level domain is one of the categories of top-level domains maintained by the Internet Assigned Numbers Authority for use in the Domain Name System of the Internet....

s (gTLDs), such as the prominent domains com
.com
The domain name com is a generic top-level domain in the Domain Name System of the Internet. Its name is derived from commercial, indicating its original intended purpose for domains registered by commercial organizations...

, net
.net
The domain name net is a generic top-level domain used in the Domain Name System of the Internet. The name is derived from network, indicating its originally intended purpose for organizations involved in networking technologies, such as Internet service providers and other infrastructure companies...

and org
.org
The domain name org is a generic top-level domain of the Domain Name System used in the Internet. The name is derived from organization....

, and the country code top-level domain
Country code top-level domain
A country code top-level domain is an Internet top-level domain generally used or reserved for a country, a sovereign state, or a dependent territory....

s (ccTLDs). Below these top-level domains in the DNS hierarchy are the second-level and third-level domain names that are typically open for reservation by end-users that wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites. The registration of these domain names is usually administered by domain name registrar
Domain name registrar
A domain name registrar is an organization or commercial entity, accredited by both ICANN and generic top-level domain registry to sell gTLDs and/or by a country code top-level domain registry to sell ccTLDs; to manage the reservation of Internet domain names in accordance with the guidelines of...

s who sell their services to the public.

Purpose


Domain names serve as humanly-memorable names for Internet participants, like computers, networks, and services. A domain name represents an Internet Protocol (IP) resource. Individual Internet host computers use domain names as host identifiers, or hostnames. Hostnames are the leaf labels in the domain name system usually without further subordinate domain name space. Hostnames appear as a component in Uniform Resource Locator
Uniform Resource Locator
In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....

s (URLs) for Internet resources such as web sites (e.g., en.wikipedia.org).

Domain names are also used as simple identification labels to indicate ownership or control of a resource. Such examples are the realm identifiers used in the Session Initiation Protocol
Session Initiation Protocol
The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...

 (SIP), the DomainKeys
DomainKeys
DomainKeys is an e-mail authentication system designed to verify the DNS domain of an e-mail sender and the message integrity. The DomainKeys specification has adopted aspects of Identified Internet Mail to create an enhanced protocol called DomainKeys Identified Mail...

 used to verify DNS domains in e-mail
E-mail
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

 systems, and in many other Uniform Resource Identifier
Uniform Resource Identifier
In computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...

s (URIs).

An important function of domain names is to provide easily recognizable and memorizable names to numerically addressed
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...

 Internet resources. This abstraction allows any resource to be moved to a different physical location in the address topology of the network, globally or locally in an intranet
Intranet
An intranet is a computer network that uses Internet Protocol technology to securely share any part of an organization's information or network operating system within that organization. The term is used in contrast to internet, a network between organizations, and instead refers to a network...

. Such a move usually requires changing the IP address of a resource and the corresponding translation of this IP address to and from its domain name.

Domain names are often referred to simply as domains and domain name registrants are frequently referred to as domain owners, although domain name registration with a registrar does not confer any legal ownership of the domain name, only an exclusive right of use.

The use of domain names in commerce may subject them to trademark law. In 2010, the number of active domains reached 196 million.

History


The practice of using a name as a simple memorable abstraction of a host's numerical address on a computer network dates back to the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...

 era, before the advent of today's commercial Internet. In the early network, each computer on the network retrieved the hosts file (host.txt) from a computer at SRI (now SRI International
SRI International
SRI International , founded as Stanford Research Institute, is one of the world's largest contract research institutes. Based in Menlo Park, California, the trustees of Stanford University established it in 1946 as a center of innovation to support economic development in the region. It was later...

). which mapped computer host names to numerical addresses. The rapid growth of the network made it impossible to maintain a centrally organized hostname registry and in 1983 the Domain Name System was introduced on the ARPANET and published by the Internet Engineering Task Force
Internet Engineering Task Force
The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...

 as RFC 882 and RFC 883.

Domain name space


Today, the Internet Corporation for Assigned Names and Numbers (ICANN) manages the top-level development and architecture of the Internet domain name space. It authorizes domain name registrar
Domain name registrar
A domain name registrar is an organization or commercial entity, accredited by both ICANN and generic top-level domain registry to sell gTLDs and/or by a country code top-level domain registry to sell ccTLDs; to manage the reservation of Internet domain names in accordance with the guidelines of...

s, through which domain names may be registered and reassigned.

The domain name space consists of a tree of domain names. Each node in the tree holds information associated with the domain name. The tree sub-divides into zones beginning at the DNS root zone
DNS root zone
A DNS root zone is the top-level DNS zone in a Domain Name System hierarchy. Most commonly it refers to the root zone of the largest global DNS, deployed for the Internet. Ultimate authority over the DNS root zone rests with the US Department of Commerce NTIA...

.

Domain name syntax


A domain name consists of one or more parts, technically called labels, that are conventionally concatenated, and delimited by dots, such as example.com
Example.com
Example.com, example.net, example.org, and example.edu are second-level domain names reserved for documentation purposes and examples of the use of domain names....

.
  • The right-most label conveys the top-level domain
    Top-level domain
    A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...

    ; for example, the domain name www.example.com belongs to the top-level domain com.
  • The hierarchy of domains descends from the right to the left label in the name; each label to the left specifies a subdivision, or subdomain
    Subdomain
    In the Domain Name System hierarchy, a subdomain is a domain that is part of a larger domain.- Overview :The Domain Name System has a tree structure or hierarchy, with each node on the tree being a domain name. A subdomain is a domain that is part of a larger domain, the only domain that is not...

     of the domain to the right. For example: the label example specifies a node example.com as a subdomain of the com domain, and www is a label to create www.example.com, a subdomain of example.com. This tree of labels may consist of 127 levels. Each label may contain from 1 to 63 octets. The empty label is reserved for the root node. The full domain name may not exceed a total length of 253 characters. In practice, some domain registries
    Domain name registry
    A domain name registry is a database of all domain names registered in a top-level domain. A registry operator, also called a network information center , is the part of the Domain Name System of the Internet that keeps the database of domain names, and generates the zone files which convert...

     may have shorter limits.
  • A hostname
    Hostname
    A hostname is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication such as the World Wide Web, e-mail or Usenet...

     is a domain name that has at least one associated IP address. For example, the domain names www.example.com and example.com are also hostnames, whereas the com domain is not. However, other top-level domains, particularly country code top-level domains, may indeed have an IP address, and if so, they are also hostnames.
  • Hostnames impose restrictions on the characters allowed in the corresponding domain name. A valid hostname is also a valid domain name, but a valid domain name may not necessarily be valid as a hostname.

Top-level domains


The top-level domain
Top-level domain
A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...

s (TLDs) are the highest level of domain names of the Internet. They form the DNS root zone
DNS root zone
A DNS root zone is the top-level DNS zone in a Domain Name System hierarchy. Most commonly it refers to the root zone of the largest global DNS, deployed for the Internet. Ultimate authority over the DNS root zone rests with the US Department of Commerce NTIA...

 of the hierarchical Domain Name System
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

. Every domain name ends in a top-level or first-level domain label.

When the Domain Name System was created in the 1980s, the domain name space was divided into two main groups of domains. The country code top-level domain
Country code top-level domain
A country code top-level domain is an Internet top-level domain generally used or reserved for a country, a sovereign state, or a dependent territory....

s (ccTLD) were primarily based on the two-character territory codes of ISO-3166
ISO 3166-1 alpha-2
ISO 3166-1 alpha-2 codes are two-letter country codes defined in ISO 3166-1, part of the ISO 3166 standard published by the International Organization for Standardization , to represent countries, dependent territories, and special areas of geographical interest...

 country abbreviations. In addition, a group of seven generic top-level domain
Generic top-level domain
A generic top-level domain is one of the categories of top-level domains maintained by the Internet Assigned Numbers Authority for use in the Domain Name System of the Internet....

s (gTLD) was implemented which represented a set of categories of names and multi-organizations. These were the domains GOV
.gov
The domain name gov is a sponsored top-level domain in the Domain Name System of the Internet. The name is derived from government, indicating its restricted use by government entities in the United States. The gov domain is administered by the General Services Administration , an independent...

, EDU
.edu
The domain name edu is a sponsored top-level domain in the Domain Name System of the Internet. The "domain is intended for accredited post-secondary educational U.S. institutions" and this intention is strictly enforced....

, COM
.com
The domain name com is a generic top-level domain in the Domain Name System of the Internet. Its name is derived from commercial, indicating its original intended purpose for domains registered by commercial organizations...

, MIL
.mil
The domain name mil is the sponsored top-level domain in the Domain Name System of the Internet for the United States Department of Defense and its subsidiary or affiliated organizations. The name is derived from military. It was one of the first top-level domains, created in January 1985.The...

, ORG
.org
The domain name org is a generic top-level domain of the Domain Name System used in the Internet. The name is derived from organization....

, NET
.net
The domain name net is a generic top-level domain used in the Domain Name System of the Internet. The name is derived from network, indicating its originally intended purpose for organizations involved in networking technologies, such as Internet service providers and other infrastructure companies...

, and INT
.int
The domain name int is a sponsored top-level domain in the Domain Name System of the Internet. Its name is derived from the word international, characterizing its use for world-wide purposes....

.

During the growth of the Internet, it became desirable to create additional generic top-level domains. As of October 2009, there are 21 generic top-level domains and 250 two-letter country-code top-level domains. In addition, the ARPA
.arpa
The domain name arpa is a top-level domain in the Domain Name System of the Internet. It is used exclusively for technical infrastructure purposes...

domain serves technical purposes in the infrastructure of the Domain Name System.

During the 32nd International Public ICANN Meeting in Paris in 2008, ICANN started a new process of TLD naming policy to take a "significant step forward on the introduction of new generic top-level domains." This program envisions the availability of many new or already proposed domains, as well a new application and implementation process. Observers believed that the new rules could result in hundreds of new top-level domains to be registered.

An annotated list of top-level domains in the root zone database is published at the IANA website at http://www.iana.org/domains/root/db/ and a Wikipedia list exists.

Second-level and lower level domains


Below the top-level domains in the domain name hierarchy are the second-level domain
Second-level domain
In the Domain Name System hierarchy, a second-level domain is a domain that is directly below a top-level domain . For example, in example.com, example is the second-level domain of the .com TLD....

 (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 example.co.uk, co is the second-level domain.

Next are third-level domains, which are written immediately to the left of a second-level domain. There can be fourth- and fifth-level domains, and so on, with virtually no limitation. An example of an operational domain name with four levels of domain labels is www.sos.state.oh.us. The www preceding the domains is the host name of the World-Wide Web server. Each label is separated by a full stop
Full stop
A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...

 (dot). 'sos' is said to be a sub-domain of 'state.oh.us', and 'state' a sub-domain of 'oh.us', etc. In general, subdomain
Subdomain
In the Domain Name System hierarchy, a subdomain is a domain that is part of a larger domain.- Overview :The Domain Name System has a tree structure or hierarchy, with each node on the tree being a domain name. A subdomain is a domain that is part of a larger domain, the only domain that is not...

s are domains subordinate to their parent domain. An example of very deep levels of subdomain ordering are the IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

 reverse resolution DNS zone
DNS zone
A DNS zone is a portion of the global Domain Name System namespace for which administrative responsibility has been delegated.-Definition:...

s, e.g., 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa, which is the reverse DNS resolution domain name for the IP address of a loopback
Loopback
Loopback describes ways of routing electronic signals, digital data streams, or flows of items from their originating facility back to the source without intentional processing or modification...

 interface, or the localhost
Localhost
In computer networking, localhost is the standard hostname given to the address of the loopback network interface. The name is also a reserved top-level domain name In computer networking, localhost (meaning this computer) is the standard hostname given to the address of the loopback network...

 name.

Second-level (or lower-level, depending on the established parent hierarchy) domain names are often created based on the name of a company (e.g., bbc.co.uk), product or service (e.g., gmail.com). Below these levels, the next domain name component has been 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
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...

 server, and mail.wikipedia.org could be an email server, each intended to perform only the implied function. Modern technology allows multiple physical servers with either different (cf. load balancing
Load balancing (computing)
Load balancing is a computer networking methodology to distribute workload across multiple computers or a computer cluster, network links, central processing units, disk drives, or other resources, to achieve optimal resource utilization, maximize throughput, minimize response time, and avoid...

) or even identical addresses (cf. anycast
Anycast
Anycast is a network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers all identified by the same destination address.-Addressing methodologies:...

) to serve a single hostname or domain name, or multiple domain names to be served by a single computer. The latter is very popular in Web hosting service
Web hosting service
A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own or lease for use by their clients as well as providing Internet...

 centers, where service providers host the websites of many organizations on just a few servers.

The hierarchical DNS labels or components of domain names are separated in a fully qualified name by the full stop
Full stop
A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...

 (dot, .).

Internationalized domain names



The character set allowed in the Domain Name System is based on ASCII
ASCII
The American Standard Code for Information Interchange is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text...

 and does not allow the representation of names and words of many languages in their native scripts or alphabets. ICANN
ICANN
The Internet Corporation for Assigned Names and Numbers is a non-profit corporation headquartered in Marina del Rey, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly...

 approved the Internationalized domain name
Internationalized domain name
An internationalized domain name is an Internet domain name that contains at least one label that is displayed in software applications, in whole or in part, in a language-specific script or alphabet, such as Arabic, Chinese, Russian, Hindi or the Latin alphabet-based characters with diacritics,...

 (IDNA) system, which maps Unicode
Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...

 strings used in application user interfaces into the valid DNS character set by an encoding called Punycode
Punycode
In computing, Punycode is an instance of a general encoding syntax by which a string of Unicode characters is transformed uniquely and reversibly into a smaller, restricted character set....

. For example, københavn.eu is mapped to xn--kbenhavn-54a.eu. Many registries
Domain name registry
A domain name registry is a database of all domain names registered in a top-level domain. A registry operator, also called a network information center , is the part of the Domain Name System of the Internet that keeps the database of domain names, and generates the zone files which convert...

 have adopted IDNA.

History


The first commercial Internet domain name, in the TLD com, was registered on 15 March 1985 in the name Symbolics.com by Symbolics Inc., a computer systems firm in Cambridge, Massachusetts.

By 1992 fewer than 15,000 com domains had been registered.

In December 2009 there were 192 million domain names. A large fraction of them are in the com TLD, which as of March 15, 2010 had 84 million domain names, including 11.9 million online business and e-commerce sites, 4.3 million entertainment sites, 3.1 million finance related sites, and 1.8 million sports sites.

Administration


The right to use a domain name is delegated by domain name registrar
Domain name registrar
A domain name registrar is an organization or commercial entity, accredited by both ICANN and generic top-level domain registry to sell gTLDs and/or by a country code top-level domain registry to sell ccTLDs; to manage the reservation of Internet domain names in accordance with the guidelines of...

s, which are accredited by the Internet Corporation for Assigned Names and Numbers (ICANN), the organization charged with overseeing the name and number systems of the Internet. In addition to ICANN, each top-level domain (TLD) is maintained and serviced technically by an administrative organization operating a registry. A registry is responsible for maintaining the database of names registered within the TLD it administers. The registry receives registration information from each domain name registrar authorized to assign names in the corresponding TLD and publishes the information using a special service, the whois
WHOIS
WHOIS is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system, but is also used for a wider range of other information. The protocol stores...

 protocol.

Registries and registrars usually charge an annual fee for the service of delegating a domain name to a user and providing a default set of name servers. Often, this transaction is termed a sale or lease of the domain name, and the registrant may sometimes be called an "owner", but no such legal relationship is actually associated with the transaction, only the exclusive right to use the domain name. More correctly, authorized users are known as "registrants" or as "domain holders".

ICANN
ICANN
The Internet Corporation for Assigned Names and Numbers is a non-profit corporation headquartered in Marina del Rey, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly...

 publishes the complete list of TLD registries and domain name registrars. Registrant information associated with domain names is maintained in an online database accessible with the WHOIS
WHOIS
WHOIS is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system, but is also used for a wider range of other information. The protocol stores...

 service. For most of the 250 country code top-level domain
Country code top-level domain
A country code top-level domain is an Internet top-level domain generally used or reserved for a country, a sovereign state, or a dependent territory....

s (ccTLDs), the domain registries maintain the WHOIS (Registrant, name servers, expiration dates, etc.) information.

Some domain name registries, often called network information centers (NIC), also function as registrars to end-users. The major generic top-level domain registries, such as for the COM, NET, ORG, INFO domains and others, use a registry-registrar model consisting of hundreds of domain name registrars (see lists at ICANN or VeriSign). In this method of management, the registry only manages the domain name database and the relationship with the registrars. The registrants (users of a domain name) are customers of the registrar, in some cases through additional layers of resellers.

Technical requirements and process


In the process of registering a domain name and maintaining authority over the new name space created, registrars use several key pieces of information connected with a domain:
  • Administrative contact. A registrant usually designates an administrative contact to manage the domain name. The administrative contact usually has the highest level of control over a domain. Management functions delegated to the administrative contacts may include management of all business information, such as name of record, postal address, and contact information of the official registrant of the domain and the obligation to conform to the requirements of the domain registry in order to retain the right to use a domain name. Furthermore the administrative contact installs additional contact information for technical and billing functions.
  • Technical contact. The technical contact manages the name servers of a domain name. The functions of a technical contact include assuring conformance of the configurations of the domain name with the requirements of the domain registry, maintaining the domain zone records, and providing continuous functionality of the name servers (that leads to the accessibility of the domain name).
  • Billing contact. The party responsible for receiving billing invoices from the domain name registrar
    Domain name registrar
    A domain name registrar is an organization or commercial entity, accredited by both ICANN and generic top-level domain registry to sell gTLDs and/or by a country code top-level domain registry to sell ccTLDs; to manage the reservation of Internet domain names in accordance with the guidelines of...

     and paying applicable fees.
  • Name servers. Most registrars provide two or more name servers as part of the registration service. However, a registrant may specify its own authoritative name servers to host a domain's resource records. The registrar's policies govern the number of servers and the type of server information required. Some providers require a hostname and the corresponding IP address or just the hostname, which must be resolvable either in the new domain, or exist elsewhere. Based on traditional requirements (RFC 1034), typically a minimum of two servers is required.


Domain names may be formed from the set of alphanumeric ASCII characters (a-z, A-Z, 0-9), but characters are case-insensitive. In addition the hyphen is permitted if it is surrounded by a characters or digits, i.e. it is not the start or end of a label. Labels are always separated by the full stop
Full stop
A full stop is the punctuation mark commonly placed at the end of sentences. In American English, the term used for this punctuation is period. In the 21st century, it is often also called a dot by young people...

 (period) character in the textual name representation.

Business models


Domain names are often seen in analogy to real estate
Real estate
In general use, esp. North American, 'real estate' is taken to mean "Property consisting of land and the buildings on it, along with its natural resources such as crops, minerals, or water; immovable property of this nature; an interest vested in this; an item of real property; buildings or...

 in that (1) domain names are foundations 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
Search engine optimization
Search engine optimization is the process of improving the visibility of a website or a web page in search engines via the "natural" or un-paid search results...

, and many other criteria.

A few companies have offered low-cost, below-cost or even cost-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 can give away or sell infinite number of subdomain
Subdomain
In the Domain Name System hierarchy, a subdomain is a domain that is part of a larger domain.- Overview :The Domain Name System has a tree structure or hierarchy, with each node on the tree being a domain name. A subdomain is a domain that is part of a larger domain, the only domain that is not...

s under their domain name. For example, the owner of example.org could provide subdomains such as foo.example.org and foo.bar.example.org to interested parties.
Because of the popularity of the Internet, many desirable domain names are already assigned and users must search for other acceptable names, using Web-based search features, or WHOIS
WHOIS
WHOIS is a query and response protocol that is widely used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system, but is also used for a wider range of other information. The protocol stores...

 and dig
Domain Information Groper
Domain Information Groper is a network administration command-line tool for querying Domain Name System name servers for any desired DNS records....

 operating system tools. Many registrars have implemented Domain name suggestion tools which search domain name databases and suggest available alternative domain names related to keywords provided by the user.

Resale of domain names


The business of resale of registered domain names is known as the domain aftermarket
Domain aftermarket
The domain aftermarket is the secondary market for Internet domain names in which a party interested in acquiring a domain that is already registered bids or negotiates a price to effect the transfer of registration from the registered holder of that domain name.The professional pursuit of...

. Various factors influence the perceived value or market value of a domain name.

As of 2011, the most expensive domain name sales on record were:
  1. Insure.com 2009 $16 million
  2. Sex.com
    Sex.com
    Sex.com is an Internet domain name and web portal currently owned by Clover Holdings LTD. The domain name was the focus of one of the most publicized legal actions about ownership of domain names...

     for $14 million in October 2010
  3. Fund.com 2008 £9.99 million
  4. Porn.com 2007 $9.5 million
  5. Fb.com
    Facebook
    Facebook is a social networking service and website launched in February 2004, operated and privately owned by Facebook, Inc. , Facebook has more than 800 million active users. Users must register before using the site, after which they may create a personal profile, add other users as...

     for $8.5 million in November 2010
  6. Business.com for $7.5 million in December 1999
  7. Diamond.com 2006 $7.5 million
  8. Beer.com 2004 $7 million
  9. Israel.com 2008 $5.88 million
  10. Casino.com 2003 $5.5 million
  11. Toys.com: Toys 'R' Us by auction for $5.1 million in 2009
  12. AsSeenOnTv.com for $5.1 million in January 2000
  13. iCloud.com by Apple for $4.5 million in April 2011
  14. Altavista.com for $3.3 million in August 1998
  15. Candy.com for $3.0 million in June 2009
  16. Wine.com for $2.9 million in September 1999
  17. CreditCards.com for $2.75 million in July 2004
  18. Autos.com for $2.2 million in December 1999
  19. Casino.tt for $2.0 million in May 2011

Domain name confusion


Intercapping is often used to emphasize the meaning of a domain name. However, DNS names are case-insensitive, and some names may be misinterpreted in certain uses of capitalization, creating slurl
Slurl
A slurl is a website domain name that has a double meaning, often crude or sexual, that was not intended by the individual or organisation running the website. Domain names are conventionally shown in all lower-case and cannot contain spaces, so to determine the meaning readers must themselves...

s. For example: Who Represents, a database of artists and agents, chose whorepresents.com, which can be misread as whore presents. Similarly, a therapists' network is named therapistfinder.com. In such situations, the proper meaning may be clarified by use of hyphens in the domain name. For instance, Experts Exchange
Experts-Exchange
Experts-Exchange.com is a membership-based online "ask an expert" site for computer and IT related questions that was founded in 1996....

, a programmers' discussion site, for a long time used expertsexchange.com, but ultimately changed the name to experts-exchange.com.

Intellectual property entrepreneur Leo Stoller
Leo Stoller
Leo D. Stoller is an American self-styled "intellectual property entrepreneur" based in suburban Chicago, Illinois. Stoller controversially claimed rights to a large inventory of "famous" trademarks and engaged in the assertive enforcement of those alleged trademark rights, threatening...

 threatened to sue the owners of StealThisEmail.com on the basis that, when read as stealthisemail.com, it infringed on claimed (but invalid) trademark rights to the word "stealth".

Use in web site hosting


The domain name is a component of a Uniform Resource Locator
Uniform Resource Locator
In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....

 (URL) used to access web sites, for example:
  • URL: http://www.example.net/index.html
  • Top-level domain name: example.net
  • Second-level domain name: example.net
  • Host name: www.example.net


A domain name may point to multiple IP addresses in order to provide server redundancy for the cybernetic services to be delivered; such multi-address capability is used to manage the traffic of large, popular web sites. More commonly, however, one server computer, at a given IP address, may also host web sites in different domains. Such address overloading enables virtual web hosting
Virtual hosting
Virtual hosting is a method for hosting multiple domain names on a server using a single IP address. This allows one server to share its resources, such as memory and processor cycles, in order to use its resources more efficiently....

, commonly used by large web hosting service
Web hosting service
A web hosting service is a type of Internet hosting service that allows individuals and organizations to make their own website accessible via the World Wide Web. Web hosts are companies that provide space on a server they own or lease for use by their clients as well as providing Internet...

s to conserve IP address space. IP-address overloading is possible through a feature in the HTTP version 1.1 protocol, but not in the HTTP version 1.0 protocol, which requires that a request identify the domain name being referred for connection.

Abuse and regulation


Critics often claim abuse of administrative power over domain names. Particularly noteworthy was the VeriSign
VeriSign
Verisign, Inc. is an American company based in Dulles, Virginia that operates a diverse array of network infrastructure, including two of the Internet's thirteen root nameservers, the authoritative registry for the .com, .net, and .name generic top-level domains and the .cc and .tv country-code...

 Site Finder
Site Finder
Site Finder was a wildcard DNS record for all .com and .net unregistered domain names, run by .com and .net top-level domain operator VeriSign between 15 September 2003 and 4 October 2003.-Site Finder:...

 system which redirected all unregistered .com and .net domains to a VeriSign webpage. For example, at a public meeting with VeriSign to air technical concerns about SiteFinder, numerous people, active in the IETF
Internet Engineering Task Force
The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite...

 and other technical bodies, explained how they were surprised by VeriSign's changing the fundamental behavior of a major component of Internet infrastructure, not having obtained the customary consensus. SiteFinder, at first, assumed every Internet query was for a website, and it monetized queries for incorrect domain names, taking the user to VeriSign's search site. Unfortunately, other applications, such as many implementations of email, treat a lack of response to a domain name query as an indication that the domain does not exist, and that the message can be treated as undeliverable. The original VeriSign implementation broke this assumption for mail, because it would always resolve an erroneous domain name to that of SiteFinder. While VeriSign later changed SiteFinder's behaviour with regard to email, there was still widespread protest about VeriSign's action being more in its financial interest than in the interest of the Internet infrastructure component for which VeriSign was the steward.

Despite widespread criticism, VeriSign only reluctantly removed it after the Internet Corporation for Assigned Names and Numbers (ICANN) threatened to revoke its contract to administer the root name servers. ICANN published the extensive set of letters exchanged, committee reports, and ICANN decisions.

There is also significant disquiet regarding the United States' political influence over ICANN. This was a significant issue in the attempt to create a .xxx
.xxx
.xxx is a sponsored top-level domain intended as a voluntary option for pornographic sites on the Internet. The sponsoring organization is the International Foundation for Online Responsibility . The registry is operated by ICM Registry LLC. The ICANN Board voted to approve the sTLD on March 18,...

 top-level domain
Top-level domain
A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...

 and sparked greater interest in alternative DNS root
Alternative DNS root
The Internet uses the Domain Name System to associate the names of computers with their numeric IP addresses and with other information. The top level of the domain name hierarchy, the DNS root, contains the top-level domains that appear as the suffixes of all Internet domain names. The official...

s that would be beyond the control of any single country.

Additionally, there are numerous accusations of domain name front running
Domain name front running
Domain name front running is the practice whereby a domain name registrar uses insider information to register domains for the purpose of re-selling them or earning revenue via ads placed on the domain's landing page. By registering the domains, the registrar locks out other potential registrars...

, whereby registrars, when given whois queries, automatically register the domain name for themselves. Network Solutions has been accused of this.

Truth in Domain Names Act


In the United States, the Truth in Domain Names Act of 2003, in combination with the PROTECT Act of 2003
PROTECT Act of 2003
The PROTECT Act of 2003 is a United States law with the stated intent of preventing child abuse. "PROTECT" is a "backronym" which stands for "Prosecutorial Remedies and Other Tools to end the Exploitation of Children Today"....

, forbids the use of a misleading domain name with the intention of attracting Internet users into visiting Internet pornography
Internet pornography
Internet pornography is pornography that is distributed by means of various sectors of the Internet, primarily via websites, peer-to-peer file sharing, or Usenet newsgroups...

 sites.

The Truth in Domain Names Act follows the more general Anticybersquatting Consumer Protection Act
Anticybersquatting Consumer Protection Act
The Anticybersquatting Consumer Protection Act ', 15 U.S.C. § 1125, is an American law enacted in 1999 and established a cause of action for registering, trafficking in, or using a domain name confusingly similar to, or dilutive of, a trademark or personal name...

 passed in 1999 aimed at preventing typosquatting
Typosquatting
Typosquatting, also called URL hijacking, is a form of cybersquatting, and possibly brandjacking which relies on mistakes such as typographical errors made by Internet users when inputting a website address into a web browser...

 and deceptive use of names and trademarks in domain names.

Seizures



In the early 21st century, the US Department of Justice began using a tactic of seizing
Search and seizure
Search and seizure is a legal procedure used in many civil law and common law legal systems whereby police or other authorities and their agents, who suspect that a crime has been committed, do a search of a person's property and confiscate any relevant evidence to the crime.Some countries have...

 domain names, based on the legal theory that domain names are part of the property used by defendants to allegedly engage in criminal activities, and thus subject to forfeiture
Forfeiture (law)
Forfeiture is deprivation or destruction of a right in consequence of the non-performance of some obligation or condition. It can be accidental, and therefore is distinguished from waiver; see waiver and forfeiture....

. For example, in the seizure of a gambling website, the DOJ referenced and .

The congress encouraged this by passing the Combating Online Infringement and Counterfeits Act in 2010. Consumer Electronics Association VP Petricone was worried seizure was a 'blunt instrument' that could harm legitimate businesses.

Fictitious domain name


A fictitious domain name is a domain name used in a work of fiction or popular culture to refer to a domain that does not actually exist, often with invalid or unofficial top-level domain
Top-level domain
A top-level domain is one of the domains at the highest level in the hierarchical Domain Name System of the Internet. The top-level domain names are installed in the root zone of the name space. For all domains in lower levels, it is the last part of the domain name, that is, the last label of a...

s, such as ".web
.web
.web is a generic top-level domain operated as a prospective registry, not in the official root, by Image Online Design since 1995. It originated when Jon Postel, then running the top level of the Domain Name System basically single-handedly, proposed the addition of new top-level domains to be...

".

Domain names used in works of fiction have often been registered in the DNS, either by their creators or by cybersquatters
Cybersquatting
Cybersquatting , according to the United States federal law known as the Anticybersquatting Consumer Protection Act, is registering, trafficking in, or using a domain name with bad faith intent to profit from the goodwill of a trademark belonging to someone else...

 attempting to profit from it. This phenomenon prompted NBC
NBC
The National Broadcasting Company is an American commercial broadcasting television network and former radio network headquartered in the GE Building in New York City's Rockefeller Center with additional major offices near Los Angeles and in Chicago...

 to purchase the domain name Hornymanatee.com after talk-show host Conan O'Brien
Conan O'Brien
Conan Christopher O'Brien is an American television host, comedian, writer, producer and performer. Since November 2010 he has hosted Conan, a late-night talk show that airs on the American cable television station TBS....

 spoke the name while ad-libbing on his show
Late Night with Conan O'Brien
Late Night with Conan O'Brien is an American late-night talk show hosted by Conan O'Brien that aired 2,725 episodes on NBC between 1993 and 2009. The show featured varied comedic material, celebrity interviews, and musical and comedy performances. Late Night aired weeknights at 12:37 am...

. O'Brien subsequently created a website based on the concept and used it as a running gag
Running gag
A running gag, or running joke, is a literary device that takes the form of an amusing joke or a comical reference and appears repeatedly throughout a work of literature or other form of storytelling....

 on the show.

See also


  • Domain hack
    Domain hack
    A domain hack is an unconventional domain name that combines domain levels, especially the top-level domain , to spell out the full "name" or title of the domain. Examples include del.icio.us , goo.gl and fold.it...

  • Domain hijacking
    Domain hijacking
    Domain hijacking or domain theft is the act of changing the registration of a domain name without the permission of its original registrant....

  • Domain name warehousing
    Domain name warehousing
    Domain name warehousing is the common practice of registrars obtaining control of domain names with the intent to hold or “warehouse” names for their use and/or profit...

  • Domain tasting
    Domain tasting
    Domain tasting is the practice of a domain name registrant using the five-day "grace period" at the beginning of the registration of an ICANN-regulated second-level domain to test the marketability of the domain...

  • Domain transfer
  • Domaining
  • Fully qualified domain name
  • Geodomain
    Geodomain
    The term geodomain refers to domain names that are the same as those of geographic entities, such as cities and countries. It is unrelated to the geographic subdomains of the .us country domain. Examples of geodomains are Atlanta.com, LosAngeles.com, Texas.com and Memphis.org...

  • ICANN
    ICANN
    The Internet Corporation for Assigned Names and Numbers is a non-profit corporation headquartered in Marina del Rey, California, United States, that was created on September 18, 1998, and incorporated on September 30, 1998 to oversee a number of Internet-related tasks previously performed directly...

  • Name generator
  • Public domain issues of domain names
  • Public Suffix List
    Public Suffix List
    The Public Suffix List is a catalog of certain Internet domain name suffixes. A "public suffix" is also known by the older term effective top level domain...

  • Uniform Resource Locator
    Uniform Resource Locator
    In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....

  • Web page
    Web page
    A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...



External links