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A domain name is a string that identifies a realm of administrative autonomy, authority or control within the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, p ...
. Domain names are often used to identify services provided through the Internet, such as
website A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google, Facebook, Amazon, and W ...
s,
email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" mean ...
services and more. As of 2017, 330.6 million domain names had been registered. Domain names are used in various networking contexts and for application-specific naming and addressing purposes. In general, a domain name identifies a
network domain A network domain is an administrative grouping of multiple private computer networks or local hosts within the same infrastructure. Domains can be identified using a domain name; domains which need to be accessible from the public Internet can ...
or an
Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. ...
(IP) resource, such as a personal computer used to access the Internet, or a server computer. Domain names are formed by the rules and procedures of the
Domain Name System The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned t ...
(DNS). Any name registered in the DNS is a domain name. 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 A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
s (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains
com Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level d ...
, info, net, edu, and org, and the
country code top-level domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all ...
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 who wish to connect local area networks to the Internet, create other publicly accessible Internet resources or run web sites. The registration of a second- or third-level domain name is usually administered by a
domain name registrar A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) Domain name registry, registry or a country code top-level domain (ccTLD) ...
who sell its services to the public. A fully qualified domain name (FQDN) is a domain name that is completely specified with all labels in the hierarchy of the DNS, having no parts omitted. Traditionally a FQDN ends in a dot (.) to denote the top of the DNS tree. Labels in the Domain Name System are case-insensitive, and may therefore be written in any desired capitalization method, but most commonly domain names are written in lowercase in technical contexts.


Purpose

Domain names serve to identify Internet resources, such as computers, networks, and services, with a text-based label that is easier to memorize than the numerical addresses used in the Internet protocols. A domain name may represent entire collections of such resources or individual instances. Individual Internet host computers use domain names as host identifiers, also called hostnames. The term ''hostname'' is also used for the leaf labels in the domain name system, usually without further subordinate domain name space. Hostnames appear as a component in
Uniform Resource Locator A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identif ...
s (URLs) for Internet resources such as
websites A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google, Facebook, Amazon, and Wiki ...
(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 (SIP), the Domain Keys used to verify DNS domains in e-mail systems, and in many other
Uniform Resource Identifier A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...
s (URIs). An important function of domain names is to provide easily recognizable and memorizable names to numerically addressed 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 An intranet is a computer network for sharing information, easier communication, collaboration tools, operational systems, and other computing services within an organization, usually to the exclusion of access by outsiders. The term is used in c ...
. 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 used to establish a unique identity. Organizations can choose a domain name that corresponds to their name, helping Internet users to reach them easily. A generic domain is a name that defines a general category, rather than a specific or personal instance, for example, the name of an industry, rather than a company name. Some examples of generic names are ''books.com'', ''music.com'', and ''travel.info''. Companies have created brands based on generic names, and such generic domain names may be valuable. Domain names are often simply referred to 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 for a particular duration of time. The use of domain names in commerce may subject them to trademark law.


History

The practice of using a simple memorable abstraction of a host's numerical address on a computer network dates back to the
ARPANET The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...
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),RFC 3467, ''Role of the Domain Name System (DNS)'', J.C. Klensin, J. Klensin (February 2003) which mapped computer hostnames 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 The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements an ...
as RFC 882 and RFC 883. The following table shows the first five
.com The domain name .com is a top-level domain (TLD) in the Domain Name System (DNS) of the Internet. Added at the beginning of 1985, its name is derived from the word ''commercial'', indicating its original intended purpose for domains registere ...
domains with the dates of their registration: and the first five
.edu The domain name .edu is a sponsored top-level domain (sTLD) in the Domain Name System of the Internet. The domain was implemented in 1985 for the purpose of creating a domain name hierarchy for organizations with a focus on education, even abl ...
domains: at p. 869


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 A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) Domain name registry, registry or a country code top-level domain (ccTLD) ...
s, through which domain names may be registered and reassigned. The domain name space consists of a
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
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 The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet. Before October 1, 2016, the root zone had been overseen by the Internet Corporation for Assigned Names and Numbers (ICAN ...
.


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''. * The right-most label conveys the
top-level domain A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
; 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 In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is a part of another (main) domain. For example, if a domain offered an online store as part of their website example.com, it might use the subdomain shop.example.com . ...
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''. Each label may contain from 1 to 63
octets Octet may refer to: Music * Octet (music), ensemble consisting of eight instruments or voices, or composition written for such an ensemble ** String octet, a piece of music written for eight string instruments *** Octet (Mendelssohn), 1825 compo ...
. The empty label is reserved for the root node and when fully qualified is expressed as the empty label terminated by a dot. The full domain name may not exceed a total length of 253 ASCII characters in its textual representation.RFC 1035, ''Domain names--Implementation and specification'', P. Mockapetris (Nov 1987) * A hostname 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 domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all ...
s, 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

When the Domain Name System was devised in the 1980s, the domain name space was divided into two main groups of domains. The
country code top-level domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all ...
s (ccTLD) were primarily based on the two-character territory codes of
ISO-3166 ISO 3166 is a standard published by the International Organization for Standardization (ISO) that defines codes for the names of countries, dependent territories, special areas of geographical interest, and their principal subdivisions (e.g., pr ...
country abbreviations. In addition, a group of seven generic top-level domains (gTLD) was implemented which represented a set of categories of names and multi-organizations. These were the domains gov, edu,
com Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level d ...
, mil, org, net, and int. These two types of
top-level domain A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
s (TLDs) are the highest level of domain names of the Internet. Top-level domains form the
DNS root zone The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet. Before October 1, 2016, the root zone had been overseen by the Internet Corporation for Assigned Names and Numbers (ICAN ...
of the hierarchical
Domain Name System The Domain Name System (DNS) is a hierarchical and distributed naming system for computers, services, and other resources in the Internet or other Internet Protocol (IP) networks. It associates various information with domain names assigned t ...
. Every domain name ends with a top-level domain label. During the growth of the Internet, it became desirable to create additional generic top-level domains. As of October 2009, 21 generic top-level domains and 250 two-letter country-code top-level domains existed. In addition, the ARPA 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 as a new application and implementation process. Observers believed that the new rules could result in hundreds of new top-level domains to be registered. In 2012, the program commenced, and received 1930 applications. By 2016, the milestone of 1000 live gTLD was reached. The
Internet Assigned Numbers Authority The Internet Assigned Numbers Authority (IANA) is a standards organization that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System (DNS), media types, and other Inte ...
(IANA) maintains an annotated list of top-level domains in the
DNS root zone The DNS root zone is the top-level DNS zone in the hierarchical namespace of the Domain Name System (DNS) of the Internet. Before October 1, 2016, the root zone had been overseen by the Internet Corporation for Assigned Names and Numbers (ICAN ...
database. For special purposes, such as network testing, documentation, and other applications, IANA also reserves a set of special-use domain names. This list contains domain names such as
example Example may refer to: * '' exempli gratia'' (e.g.), usually read out in English as "for example" * .example The name example is reserved by the Internet Engineering Task Force (IETF) as a domain name that may not be installed as a top-level ...
, local,
localhost In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses ...
, and
test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...
. Other top-level domain names containing trade marks are registered for corporate use. Cases include brands such as BMW,
Google Google LLC () is an American Multinational corporation, multinational technology company focusing on Search Engine, search engine technology, online advertising, cloud computing, software, computer software, quantum computing, e-commerce, ar ...
, and Canon.


Second-level and lower level domains

Below the top-level domains in the domain name hierarchy are the 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 ''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. Each label is separated by a
full stop The full stop (Commonwealth English), period (North American English), or full point , is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamatio ...
(dot). An example of an operational domain name with four levels of domain labels is ''sos.state.oh.us''. 'sos' is said to be a sub-domain of 'state.oh.us', and 'state' a sub-domain of 'oh.us', etc. In general,
subdomain In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is a part of another (main) domain. For example, if a domain offered an online store as part of their website example.com, it might use the subdomain shop.example.com . ...
s are domains subordinate to their parent domain. An example of very deep levels of subdomain ordering are the
IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communications protocol that provides an identification and location system for computers on networks and routes traffic across the Internet. I ...
reverse resolution DNS zones, 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 (also written loop-back) is the routing of electronic signals or digital data streams back to their source without intentional processing or modification. It is primarily a means of testing the communications infrastructure. There are m ...
interface, or the
localhost In computer networking, localhost is a hostname that refers to the current device used to access it. It is used to access the network services that are running on the host via the loopback network interface. Using the loopback interface bypasses ...
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. ''hotmail''.com). Below these levels, the next domain name component has been used to designate a particular host server. Therefore, ''ftp.example.com'' might be an FTP server, ''www.example.com'' would be a
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web ...
server, and ''mail.example.com'' 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) or even identical addresses (cf. anycast) 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 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 The full stop (Commonwealth English), period (North American English), or full point , is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamatio ...
(dot, ''.'').


Internationalized domain names

The character set allowed in the Domain Name System is based on
ASCII ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because ...
and does not allow the representation of names and words of many languages in their native scripts or alphabets.
ICANN The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
approved the
Internationalized domain name An internationalized domain name (IDN) is an Internet domain name that contains at least one label displayed in software applications, in whole or in part, in non-latin script or alphabet, such as Arabic, Bengali, Chinese ( Mandarin, simplif ...
(IDNA) system, which maps
Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...
strings used in application user interfaces into the valid DNS character set by an encoding called
Punycode Punycode is a representation of Unicode with the limited ASCII character subset used for Internet hostnames. Using Punycode, host names containing Unicode characters are transcoded to a subset of ASCII consisting of letters, digits, and hyphens, wh ...
. For example, københavn.eu is mapped to xn--kbenhavn-54a.eu. Many registries have adopted IDNA.


Domain name registration


History

The first commercial Internet domain name, in the TLD ''com'', was registered on 15 March 1985 in the name
symbolics.com Symbolics was a computer manufacturer Symbolics, Inc., and a privately held company that acquired the assets of the former company and continues to sell and maintain the Open Genera Lisp system and the Macsyma computer algebra system.
by Symbolics Inc., a computer systems firm in Cambridge, Massachusetts. By 1992, fewer than 15,000 ''com'' domains had been registered. In the first quarter of 2015, 294 million domain names had been registered.Internet Grows to 294 Million Domain Names in the First Quarter of 2015
Jun 30, 2015.
A large fraction of them are in the ''com'' TLD, which as of December 21, 2014, had 115.6 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. As of July 2012 the ''com'' TLD had more registrations than all of the ccTLDs combined.


Administration

The right to use a domain name is delegated by
domain name registrar A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) Domain name registry, registry or a country code top-level domain (ccTLD) ...
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 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 The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
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 protocol. For most of the 250
country code top-level domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all ...
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. There are also a few other alternative DNS root providers that try to compete or complement ICANN's role of domain name administration, however, most of them failed to receive wide recognition, and thus domain names offered by those alternative roots cannot be used universally on most other internet-connecting machines without additional dedicated configurations.


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 A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) Domain name registry, registry or a country code top-level domain (ccTLD) ...
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. A domain name consists of one or more labels, each of which is formed from the set of ASCII letters, digits, and hyphens (a-z, A-Z, 0–9, -), but not starting or ending with a hyphen. The labels are case-insensitive; for example, 'label' is equivalent to 'Label' or 'LABEL'. In the textual representation of a domain name, the labels are separated by a
full stop The full stop (Commonwealth English), period (North American English), or full point , is a punctuation mark. It is used for several purposes, most often to mark the end of a declarative sentence (as distinguished from a question or exclamatio ...
(period).


Business models

Domain names are often seen in analogy to
real estate Real estate is 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 (also) an item of real property, (more genera ...
in that domain names are foundations on which a website can be built, and 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 (SEO) is the process of improving the quality and quantity of website traffic to a website or a web page from search engines. SEO targets unpaid traffic (known as "natural" or "organic" results) rather than dire ...
, and many other criteria. A few companies have offered low-cost, below-cost or even free domain registration 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 may provide an infinite number of
subdomain In the Domain Name System (DNS) hierarchy, a subdomain is a domain that is a part of another (main) domain. For example, if a domain offered an online store as part of their website example.com, it might use the subdomain shop.example.com . ...
s in their domain. For example, the owner of ''example.org'' could provide subdomains such as ''foo.example.org'' and ''foo.bar.example.org'' to interested parties. Many desirable domain names are already assigned and users must search for other acceptable names, using Web-based search features, or WHOIS and dig 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. Various factors influence the perceived value or market value of a domain name. Most of the high-prize domain sales are carried out privately.


Domain name confusion

Intercapping is often used to emphasize the meaning of a domain name, because DNS names are not case-sensitive. Some names may be misinterpreted in certain uses of capitalization. For example: ''Who Represents'', a database of artists and agents, chose ''whorepresents.com'', which can be misread. In such situations, the proper meaning may be clarified by placement of hyphens when registering a domain name. For instance, Experts Exchange, a programmers' discussion site, used ''expertsexchange.com'', but changed its domain name to ''experts-exchange.com''.


Use in web site hosting

The domain name is a component of a
uniform resource locator A Uniform Resource Locator (URL), colloquially termed as a web address, is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identif ...
(URL) used to access
web site A website (also written as a web site) is a collection of web pages and related content that is identified by a common domain name and published on at least one web server. Examples of notable websites are Google, Facebook, Amazon, and W ...
s, for example: *URL: http://www.example.net/index.html *Top-level domain: net *Second-level domain: example *Hostname: www A domain name may point to multiple
IP addresses An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...
to provide server redundancy for the services offered, a feature that is used to manage the traffic of large, popular web sites. Web hosting services, on the other hand, run servers that are typically assigned only one or a few addresses while serving websites for many domains, a technique referred to as virtual web hosting. Such IP address overloading requires that each request identifies the domain name being referenced, for instance by using the HTTP request header field ''Host:'', or Server Name Indication.


Abuse and regulation

Critics often claim abuse of administrative power over domain names. Particularly noteworthy was the VeriSign 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 The Internet Engineering Task Force (IETF) is a standards organization for the Internet and is responsible for the technical standards that make up the Internet protocol suite (TCP/IP). It has no formal membership roster or requirements an ...
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 Government's political influence over ICANN. This was a significant issue in the attempt to create a
.xxx .xxx (pronounced "dot triple- ecks" or "dot ecks ecks ecks") is a sponsored top-level domain (sTLD) intended as a voluntary option for pornographic sites on the Internet. The sponsoring organization is the International Foundation for Online R ...
top-level domain A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
and sparked greater interest in alternative DNS roots that would be beyond the control of any single country. Additionally, there are numerous accusations of
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, th ...
, 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 The PROTECT Act of 2003 (, 117 Stat. 650, S. 151, enacted April 30, 2003) is a United States law with the stated intent of preventing child abuse as well as investigating and prosecuting violent crimes against children. "PROTECT" is a contrived ...
of 2003, in combination with the
PROTECT Act of 2003 The PROTECT Act of 2003 (, 117 Stat. 650, S. 151, enacted April 30, 2003) is a United States law with the stated intent of preventing child abuse as well as investigating and prosecuting violent crimes against children. "PROTECT" is a contrived a ...
, forbids the use of a misleading domain name with the intention of attracting Internet users into visiting
Internet pornography Internet pornography is any pornography that is accessible over the internet, primarily via websites, FTP servers peer-to-peer file sharing, or Usenet newsgroups. The availability of widespread public access to the World Wide Web in late 1990s ...
sites. The Truth in Domain Names Act follows the more general Anticybersquatting Consumer Protection Act passed in 1999 aimed at preventing typosquatting and deceptive use of names and trademarks in domain names.


Seizures

File:Absolutepoker.png, absolutepoker.com File:Website seizure notice.jpg, channelsurfing.net File:Liberty Reserve seizure notice.png, libertyreserve.com In the early 21st century, the US Department of Justice (DOJ) pursued the
seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with lo ...
of domain names, based on the legal theory that domain names constitute property used to engage in criminal activity, and thus are subject to forfeiture. For example, in the seizure of the domain name of a gambling website, the DOJ referenced and .
In 2013 the US government seized Liberty Reserve, citing . The U.S. Congress passed the Combating Online Infringement and Counterfeits Act in 2010. Consumer Electronics Association vice president Michael Petricone was worried that seizure was a ''blunt instrument'' that could harm legitimate businesses. After a joint operation on February 15, 2011, the DOJ and the Department of Homeland Security claimed to have seized ten domains of websites involved in advertising and distributing child pornography, but also mistakenly seized the domain name of a large DNS provider, temporarily replacing 84,000 websites with seizure notices. In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and ...
, the Police Intellectual Property Crime Unit has been attempting to seize domain names from registrars without court orders.


Suspensions

PIPCU and other UK law enforcement organisations make domain suspension requests to
Nominet Nominet UK is currently delegated by IANA to be the manager of the .uk domain name. Nominet directly manages registrations directly under .uk, and some of the second level domains .co.uk, .org.uk, .sch.uk, .me.uk, .net.uk, .ltd.uk and .plc.uk. ...
which they process on the basis of breach of terms and conditions. Around 16,000 domains are suspended annually, and about 80% of the requests originate from PIPCU.


Property rights

Because of the economic value it represents, the
European Court of Human Rights The European Court of Human Rights (ECHR or ECtHR), also known as the Strasbourg Court, is an international court of the Council of Europe which interprets the European Convention on Human Rights. The court hears applications alleging that ...
has ruled that the exclusive right to a domain name is protected as property under article 1 of Protocol 1 to the
European Convention on Human Rights The European Convention on Human Rights (ECHR; formally the Convention for the Protection of Human Rights and Fundamental Freedoms) is an international convention to protect human rights and political freedoms in Europe. Drafted in 1950 by ...
.


IDN variants

ICANN The Internet Corporation for Assigned Names and Numbers (ICANN ) is an American multistakeholder group and nonprofit organization responsible for coordinating the maintenance and procedures of several databases related to the namespaces ...
Business Constituency (BC) has spent decades trying to make IDN variants work at the second level, and in the last several years at the top level. Domain name variants are domain names recognized in different character encodings, like a single domain presented in
traditional Chinese A tradition is a belief or behavior (folk custom) passed down within a group or society with symbolic meaning or special significance with origins in the past. A component of cultural expressions and folklore, common examples include holidays ...
and
simplified Chinese Simplification, Simplify, or Simplified may refer to: Mathematics Simplification is the process of replacing a mathematical expression by an equivalent one, that is simpler (usually shorter), for example * Simplification of algebraic expressions ...
. It is an
Internationalization and localization In computing, internationalization and localization (American) or internationalisation and localisation (British English), often abbreviated i18n and L10n, are means of adapting computer software to different languages, regional peculiarities and ...
problem. Under Domain Name Variants, the different encodings of the domain name (in simplified and traditional Chinese) would resolve to the same host. According to
John Levine John R. Levine is an Internet author and consultant specializing in email infrastructure, spam filtering, and software patents. He chaired the Anti-Spam Research Group ( ASRG) of the Internet Research Task Force (IRTF), is president of CAUCE ...
, an expert on Internet related topics, ''"Unfortunately, variants don't work. The problem isn't putting them in the DNS, it's that once they're in the DNS, they don't work anywhere else."''


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 A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
s such as " .web", a usage exactly analogous to the dummy 555 telephone number prefix used in film and other media. The canonical fictitious domain name is " example.com", specifically set aside by IANA in RFC 2606 for such use, along with the ''.example'' TLD. Domain names used in works of fiction have often been registered in the DNS, either by their creators or by cybersquatters attempting to profit from it. This phenomenon prompted NBC to purchase the domain name Hornymanatee.com after talk-show host
Conan O'Brien Conan Christopher O'Brien (born April 18, 1963) is an American television host, comedian, writer, and producer. He is best known for having hosted late-night talk shows for almost 28 years, beginning with '' Late Night with Conan O'Brien'' ( ...
spoke the name while ad-libbing on his show. O'Brien subsequently created a website based on the concept and used it as a running gag on the show.


Misspelled domain names

Misspelled domain names, also known as typosquatting or URL hijacking, are domain names that are intentionally or unintentionally misspelled versions of popular or well-known domain names. The goal of misspelled domain names is to capitalize on internet users who accidentally type in a misspelled domain name, and are then redirected to a different website. Misspelled domain names are often used for malicious purposes, such as phishing scams or distributing
malware Malware (a portmanteau for ''malicious software'') is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, depr ...
. In some cases, the owners of misspelled domain names may also attempt to sell the domain names to the owners of the legitimate domain names, or to individuals or organizations who are interested in capitalizing on the traffic generated by internet users who accidentally type in the misspelled domain names. To avoid being caught by a misspelled domain name, internet users should be careful to type in domain names correctly, and should avoid clicking on links that appear suspicious or unfamiliar. Additionally, individuals and organizations who own popular or well-known domain names should consider registering common misspellings of their domain names in order to prevent others from using them for malicious purposes.


Domain name spoofing

The term Domain name spoofing (or simply though less accurately, Domain spoofing) is used generically to describe one or more of a class of phishing attacks that depend on falsifying or misrepresenting an internet domain name. These are designed to persuade unsuspecting users into visiting a web site other than that intended, or opening an email that is not in reality from the address shown (or apparently shown). Although website and email spoofing attacks are more widely known, any service that relies on domain name resolution may be compromised.


Types

There are a number of better-known types of domain spoofing: * Typosquatting also called "URL hijacking", a "sting site", or a "fake URL", is a form of cybersquatting, and possibly
brandjacking Brandjacking is an activity whereby someone acquires or otherwise assumes the online identity of another entity for the purposes of acquiring that person's or business's brand equity. The term combines the notions of 'branding' and ' hijacking', a ...
which relies on mistakes such as
typos A typographical error (often shortened to typo), also called a misprint, is a mistake (such as a spelling mistake) made in the typing of printed (or electronic) material. Historically, this referred to mistakes in manual type-setting (typography). ...
made by Internet users when inputting a website address into a
web browser A web browser is application software for accessing websites. When a user requests a web page from a particular website, the browser retrieves its files from a web server and then displays the page on the user's screen. Browsers are used o ...
or composing an email address. Should a user accidentally enter an incorrect domain name, they may be led to any URL (including an alternative website owned by a cybersquatter). :The typosquatter's URL will usually be one of five kinds, all ''similar to'' the victim site address: :*A common misspelling, or foreign language spelling, of the intended site :*A misspelling based on a typographical error :*A plural of a singular domain name :*A different
top-level domain A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet after the root domain. The top-level domain names are installed in the root zone of the name space. For all domains in ...
: (i.e. .com instead of .org) :*An abuse of the
Country Code Top-Level Domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and all ...
(ccTLD) (.cm, .co, or .om instead of .com) * Internationalised domain name homograph attack. This type of attack depends on registering a domain name that is similar to the 'target' domain, differing from it only because its spelling includes one or more characters that come from a different alphabet but look the same to the naked eye. For example, the
Cyrillic The Cyrillic script ( ), Slavonic script or the Slavic script, is a writing system used for various languages across Eurasia. It is the designated national script in various Slavic, Turkic, Mongolic, Uralic, Caucasian and Iranic-speaking co ...
,
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
, and Greek alphabets each have their own letter , each of which has its own binary code point. Turkish has a dotless letter i () that may not be perceived as different from the ASCII letter . Most web browsers warn of 'mixed alphabet' domain names, Other services, such as email applications, may not provide the same protection. Reputable top level domain and
country code domain A country code top-level domain (ccTLD) is an Internet top-level domain generally used or reserved for a country, sovereign state, or dependent territory identified with a country code. All ASCII ccTLD identifiers are two letters long, and al ...
registrars will not accept applications to register a deceptive name but this policy cannot be presumed to be infallible. * * *


Risk mitigation

* * * ("Domain-based Message Authentication, Reporting and Conformance") * * (SSL certificate)


Legitimate technologies that may be subverted

* *


See also

* Domain hack *
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, or by abuse of privileges on domain hosting and registrar software systems. This can be devastating to ...
*
Domain name registrar A domain name registrar is a company that manages the reservation of Internet domain names. A domain name registrar must be accredited by a generic top-level domain (gTLD) Domain name registry, registry or a country code top-level domain (ccTLD) ...
* Domain name speculation *
Domain name warehousing Domain name warehousing is the practice of registrars obtaining control of expired domain names already under their management, with the intent to hold or "warehouse" names for their own use and/or profit. Typically this practice occurs after a d ...
* Domain registration *
Domain tasting Domain tasting is the practice of temporarily registering a domain under the five-day Add Grace Period at the beginning of the registration of an ICANN-regulated second-level domain. During this period, a registration must be fully refunded by the ...
* Geodomain * List of Internet top-level domains *
Reverse domain hijacking Reverse domain name hijacking (also known as reverse cybersquatting or commonly abbreviated as 'RDNH'), occurs where a rightful trademark owner attempts to secure a domain name by making cybersquatting claims against a domain name’s "cybersquatte ...
*
Reverse domain name notation Reverse domain name notation (or reverse-DNS) is a naming convention for components, packages, types or file names used by a programming language, system or framework. Reverse-DNS strings are based on registered domain names, with the order of the ...


References


External links


(domain bias in web search) a research by Microsoft Top Level Domain Bias in Search Engine Indexing and Rankings
*
Icann New gTLD Program Factsheet - October 2009
(PDF)
IANA Two letter Country Code TLD

ICANN
- Internet Corporation for Assigned Names and Numbers
Internic.net
public information regarding Internet domain name registration services
Internet Domain Names: Background and Policy Issues
Congressional Research Service The Congressional Research Service (CRS) is a public policy research institute of the United States Congress. Operating within the Library of Congress, it works primarily and directly for members of Congress and their committees and staff on a ...
* , Domain Names — Concepts and Facilities, an Internet Protocol Standard * , Domain Names — Implementation and Specification, an Internet Protocol Standard
UDRP
Uniform Domain-Name Dispute-Resolution Policy
Special use domain names
{{Authority control * Identifiers