Domain name

In general, a domain name represents an Internet Protocol (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.

A website is a collection of related web pages, including multimedia content, typically identified with a common domain name, and published on at least one web server.

The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs). This was a significant issue in the attempt to create a .xxx top-level domain and sparked greater interest in alternative DNS roots that would be beyond the control of any single country.

A top-level domain (TLD) is one of the domains at the highest level in the hierarchical Domain Name System of the Internet.

A domain name is an identification string that defines a realm of administrative autonomy, authority or control within the Internet.

ICANN coordinates the assignment of unique identifiers for use on the Internet, including domain names, Internet Protocol (IP) addresses, application port numbers in the transport protocols, and many other parameters.

The registration of these domain names is usually administered by domain name registrars who sell their services to the public.

A domain name registrar is a company that manages the reservation of Internet domain names.

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.

A fully qualified domain name (FQDN), sometimes also referred to as an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS).

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 Identifiers (URIs).

2) The MSA determines the destination address provided in the SMTP protocol (not from the message header), in this case bob@b.org which is a fully qualified domain address (FQDA). The part before the @ sign is the local part of the address, often the username of the recipient, and the part after the @ sign is a domain name. The MSA resolves a domain name to determine the fully qualified domain name of the mail server in the Domain Name System (DNS).

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 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. 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. Thus, when using a single character per label, the limit is 127 levels: 127 characters plus 126 dots have a total length of 253. In practice, some domain registries may have shorter limits.

In the Domain Name System (DNS) hierarchy, a subdomain is a domain, that is a part of a main domain.

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.net, example.org, and example.edu are second-level domain names reserved for documentation purposes and examples of the use of domain names.

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 Identifiers (URIs).

For example, the URL refers to a resource identified as whose representation, in the form of HTML and related code, is obtainable via the Hypertext Transfer Protocol (http:) from a network host whose domain name is.

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 Identifiers (URIs).

DomainKeys (informally DK) is a deprecated e-mail authentication system designed by Yahoo to verify the domain name of an e-mail sender and the message integrity.

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 domains, may indeed have an IP address, and if so, they are also hostnames.

In the latter form, a hostname is also called a domain name.

Domain names are formed by the rules and procedures of the Domain Name System (DNS).

It associates various information with domain names assigned to each of the participating entities.

Therefore, ftp.example.com might be an FTP server, www.example.com would be a World Wide Web server, and mail.example.com could be an email server, each intended to perform only the implied function.

Multiple web pages with a common theme, a common domain name, or both, make up a website.

ICANN approved the Internationalized domain name (IDNA) system, which maps Unicode strings used in application user interfaces into the valid DNS character set by an encoding called Punycode.

An internationalized domain name (IDN) 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, Cyrillic, Tamil, Hebrew or the Latin alphabet-based characters with diacritics or ligatures, such as French.

The Internet Assigned Numbers Authority (IANA) maintains an annotated list of top-level domains in the DNS root zone database.

In the case of the two major Internet namespaces, namely IP addresses and domain names, extra administrative policy and delegation to subordinate administrations is required because of the multi-layered distributed use of these resources.

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.

WHOIS (pronounced as the phrase "who is") 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.

Intercapping is often used to emphasize the meaning of a domain name.

It is also sometimes used in online usernames such as "johnSmith", and to make multi-word domain names more legible, for example in advertisements.

load balancing) or even identical addresses (cf.

In this technique, multiple IP addresses are associated with a single domain name; clients are given IP in round robin fashion.

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.

The most important function of DNS servers is the translation (resolution) of human-memorable domain names and hostnames into the corresponding numeric Internet Protocol (IP) addresses, the second principal name space of the Internet which is used to identify and locate computer systems and resources on the Internet.

The first-level set of domain names are the top-level domains (TLDs), including the generic top-level domains (gTLDs), such as the prominent domains com, info, net, edu, and org, and the country code top-level domains (ccTLDs).

World Intellectual Property Organization (WIPO) Domain name dispute resolution

An example of very deep levels of subdomain ordering are the IPv6 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 interface, or the localhost name.

At this lowest level, in the end-nodes or leaves of the tree, the term DNS zone becomes essentially synonymous with the term "domain", both in terms of use and administration.

An example of very deep levels of subdomain ordering are the IPv6 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 interface, or the localhost name. This list contains domain names such as example, local, localhost, and test.

In the Domain Name System, the name localhost is reserved as a top-level domain name, originally set aside to avoid confusion with the hostname used for loopback purposes.

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.

The Anticybersquatting Consumer Protection Act (ACPA), 15 U.S.C. § 1125(d), is a U.S. law enacted in 1999 that 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.

This was a significant issue in the attempt to create a .xxx top-level domain and sparked greater interest in alternative DNS roots that would be beyond the control of any single country.

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.

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 spoke the name while ad-libbing on his show.

Cybersquatting (also known as domain squatting), according to the United States federal law known as the Anticybersquatting Consumer Protection Act, is registering, trafficking in, or using an Internet domain name with bad faith intent to profit from the goodwill of a trademark belonging to someone else.