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Glossary of WHOIS Terms

The following terms are excerpted from the ICANN Glossary for their application to the WHOIS service. For the full Glossary of ICANN terms.

AAO - Adjacency Attestation

An AAO is a digitally signed object that verifies that an AS has made an attestation that it has an inter-domain adjacency with one or more other ASes.


See Routing Advertisement.

Advisory Committee

An Advisory Committee is a formal advisory body made up of representatives from the Internet community to advise ICANN on a particular issue or policy area. Several are mandated by the ICANN Bylaws and others may be created as needed. Advisory committees have no legal authority to act for ICANN, but report their findings and make recommendations to the ICANN Board.


African Network Information Center (AfriNIC) is the Regional Internet Registry for the African Region.

ALAC - At-Large Advisory Committee

ICANN's At-Large Advisory Committee (ALAC) is responsible for considering and providing advice on the activities of the ICANN, as they relate to the interests of individual Internet users (the "At-Large" community). ICANN, as a private sector, non-profit corporation with technical management responsibilities for the Internet's domain name and address system, will rely on the ALAC and its supporting infrastructure to involve and represent in ICANN a broad set of individual user interests.


Address space allocated by APNIC or NIRs to LIRs for the purpose of subsequent distribution by LIRs to their customers.

APNIC - Asia Pacific Network Information Center

Asia Pacific Network Information Center (APNIC) is the Regional Internet Registry for the Asia Pacific Region.

ARIN - American Registry for Internet Numbers

ARIN is a Regional Internet Registry (RIR), and is a non-profit membership organization established for the purpose of the administration and registration of Internet Protocol (IP) addresses in North America, parts of the Caribbean, and sub-Saharan Africa.

ARPA (or ".ARPA")

The Address and Routing Parameters Area top level domain, used for network infrastructure.

AS - Autonomous System

An AS is a group of IP networks run by one or more network operators with a single clearly defined routing policy.

ASN - Autonomous System Number

ASNs are globally unique identifiers for Autonomous Systems and are used as identifiers to allow the ASNs to exchange dynamic routing information. An Autonomous system (AS) is a group of IP networks having a single clearly defined routing policy run by one or more network operators.

ASO - Address Supporting Organization

The ASO advises the ICANN Board of Directors on policy issues relating to the allocation and management of Internet Protocol (IP) addresses. The ASO selects two Directors for the ICANN Board.


Address space assigned for specific use within the Internet infrastructure of a network. Assignments can be made by LIRs to their customer's network infrastructure or to the LIR's own infrastructure.

Assignment of a number

The process for providing an international numbering resource to an eligible applicant (when used in the formal sense as defined in Section 5.4 of ITU-T Rec. E.190 (05/97))

ccNSO - The Country-Code Names Supporting Organization

A Supporting Organization responsible for developing and recommending to ICANN’s Board global policies relating to country code top-level domains. It provides a forum for country code top-level domain managers to meet and discuss issues of concern from a global perspective. The ccNSO selects one person to serve on the board.

ccTLD - Country Code Top Level Domain

Two letter domains, such as .UK (United Kingdom), .DE (Germany) and .JP (Japan) (for example), are called country code top level domains (ccTLDs) and correspond to a country, territory, or other geographic location. The rules and policies for registering domain names in the ccTLDs vary significantly and ccTLD registries limit use of the ccTLD to citizens of the corresponding country.

Some ICANN-accredited registrars provide registration services in the ccTLDs in addition to registering names in .BIZ, .COM, .INFO, .NAME, .NET and .ORG, however, ICANN does not specifically accredit registrars to provide ccTLD registration services.

For more information regarding registering names in ccTLDs, including a complete database of designated ccTLDs and managers, please refer to

DNRD - Domain Name Registration Data

Refers to the information that registrants provide when registering a domain name and that registrars or registries collect. Some of this information is made available to the public. For interactions between ICANN Accredited Generic Top Level Domain (gTLD) registrars and registrants, the data elements are specified in the current RAA. For country code Top Level Domains (ccTLDs), the operators of these TLDs set their own or follow their government’s policy regarding the request and display of registration information.

DNRD-AP - Domain Name Registration Data Access Protocol

Refers to the elements of a (standard) communications exchange—queries and responses—that make access to registration data possible. For example, the WHOIS protocol (RFC 3912) and Hypertext Transfer Protocol (HTTP) (RFC 2616 and its updates) are commonly used to provide public access to DNRD.

DNRD-DS - Domain Name Registration Data Directory Service

Refers to the service(s) offered by registries and registrars to provide access to (potentially a subset of) the DNRD.


A set of host names consisting of a single domain name and all the domain names below it.

Domain Name

As part of the Domain Name System, domain names identify IP resources, such as an Internet website.

DNS - Domain Name System

The Domain Name System (DNS) helps users to find their way around the Internet. Every computer on the Internet has a unique address - just like a telephone number - which is a rather complicated string of numbers. It is called its "IP address" (IP stands for "Internet Protocol"). IP Addresses are hard to remember. The DNS makes using the Internet easier by allowing a familiar string of letters (the "domain name") to be used instead of the arcane IP address. So instead of typing, you can type It is a "mnemonic" device that makes addresses easier to remember.

GAC - Governmental Advisory Committee

The GAC is an advisory committee comprising appointed representatives of national governments, multi-national governmental organizations and treaty organizations, and distinct economies. Its function is to advise the ICANN Board on matters of concern to governments. The GAC will operate as a forum for the discussion of government interests and concerns, including consumer interests. As an advisory committee, the GAC has no legal authority to act for ICANN, but will report its findings and recommendations to the ICANN Board.

GNSO - Generic Names Supporting Organization

The supporting organization responsible for developing and recommending to the ICANN Board substantive policies relating to generic top-level domains. Its members include representatives from gTLD registries, gTLD registrars, intellectual property interests, Internet service providers, businesses and non-commercial interests. 

gTLD - Generic Top Level Domain

Most TLDs with three or more characters are referred to as "generic" TLDs, or "gTLDs", such as .COM, .NET, and .ORG.


Hypertext transfer protocol

IANA - Internet Assigned Numbers Authority

The authority originally responsible for the oversight of IP address allocation, the coordination of the assignment of protocol parameters provided for within Internet technical standards, and the management of the domain name system, including the delegation of top-level domains and oversight of the root name server system. Under ICANN, the IANA continues to distribute addresses to the Regional Internet Registries, coordinate with the IETF and others to assign protocol parameters, and oversee the operation of the DNS.

ICANN - The Internet Corporation for Assigned Names and Numbers

The Internet Corporation for Assigned Names and Numbers (ICANN) is an internationally organized, non-profit corporation that has responsibility for Internet Protocol (IP) address space allocation, protocol identifier assignment, generic (gTLD) and country code (ccTLD) Top-Level Domain name system management, and root server system management functions. Originally, the Internet Assigned Numbers Authority (IANA) and other entities performed these services under U.S. Government contract. ICANN now performs the IANA function. As a private-public partnership, ICANN is dedicated to preserving the operational stability of the Internet; to promoting competition; to achieving broad representation of global Internet communities; and to developing policy appropriate to its mission through bottom-up, consensus-based processes.

IDNs - Internationalized Domain Names

IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet "a-z". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European "0-9". The basic Latin alphabet, together with the European-Arabic digits, is for the purpose of domain names, termed "ASCII characters" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of "Unicode characters" that provides the basis for IDNs.

The "hostname rule" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen "-". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS.

The following terminology is used when distinguishing between these forms:

A domain name consists of a series of "labels" (separated by "dots"). The ASCII form of an IDN label is termed an "A-label". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a "U-label". The difference may be illustrated with the Hindi word for "test" - appearing here as a U-label would (in the Devanagari script). A special form of "ASCII compatible encoding" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn-- 11b5bs1di.

A domain name that only includes ASCII letters, digits, and hyphens is termed an "LDH label". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"" is not an IDN.

IETF - Internet Engineering Task Force

The IETF is a large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture and the smooth operation of the Internet. It is open to any interested individual.

IP - Internet Protocol

The communications protocol underlying the Internet, IP allows large, geographically diverse networks of computers to communicate with each other quickly and economically over a variety of physical links. An Internet Protocol Address is the numerical address by which a location in the Internet is identified. Computers on the Internet use IP addresses to route traffic and establish connections among themselves; people generally use the human- friendly names made possible by the Domain Name System.

ISP - Internet Service Provider

An ISP is a company, which provides access to the Internet to organizations and/or individuals. Access services provided by ISPs may include web hosting, email, VoIP (voice over IP), and support for many other applications.

LIR - Local Internet Registry

A LIR is an Internet Registry (IR) that primarily assigns address space to the users of the network services that it provides. LIRs are generally ISPs, whose customers are primarily end users and possibly other ISPs.

Name Server

A DNS component that stores information about one zone (or more) of the DNS name space.

Name Space

The structure of the DNS database.

PDP - Policy Development Process

A set of formal steps, as defined in the ICANN bylaws, to guide the initiation, internal and external review, timing and approval of policies needed to coordinate the global Internet’s system of unique identifiers.


Phishing attacks use both social engineering and technical subterfuge to steal consumers' personal identity data and financial account credentials. Social engineering schemes use spoofed emails to lead consumers to counterfeit websites designed to trick recipients into divulging financial data such as credit card numbers, account usernames, passwords and social security numbers.

Hijacking brand names of banks, e-retailers and credit card companies, phishers often convince recipients to respond. Technical subterfuge schemes plant crimeware onto PCs to steal credentials directly, often using Trojan keylogger spyware. Pharming crimeware misdirects users to fraudulent sites or proxy servers, typically through DNS hijacking or poisoning.


Domain names can be registered through many different companies (known as "registrars") that compete with one another. A listing of these companies appears in the Accredited Registrar Directory.

The registrar you choose will ask you to provide various contact and technical information that makes up the registration. The registrar will then keep records of the contact information and submit the technical information to a central directory known as the "registry." This registry provides other computers on the Internet the information necessary to send you e-mail or to find your web site. You will also be required to enter a registration contract with the registrar, which sets forth the terms under which your registration is accepted and will be maintained.


The "Registry" is the authoritative, master database of all domain names registered in each Top Level Domain. The registry operator keeps the master database and also generates the "zone file" which allows computers to route Internet traffic to and from top-level domains anywhere in the world. Internet users don't interact directly with the registry operator; users can register names in TLDs including .biz, .com, .info, .net, .name, .org by using an ICANN-Accredited Registrar.

RIPE and RIPE NCC - Réseaux IP Européens

RIPE is an open and voluntary organization, which consists of European Internet service providers. The RIPE NCC acts as the Regional Internet Registry (RIR) for Europe and surrounding areas, performs coordination activities for the organizations participating in RIPE, and allocates blocks of IP address space to its Local Internet Registries (LIRs), which then assign the addresses to end-users.

Root Servers

The root servers contain the IP addresses of all the TLD registries - both the global registries such as .com, .org, etc. and the 244 country-specific registries such as .fr (France), .cn (China), etc. This is critical information. If the information is not 100% correct or if it is ambiguous, it might not be possible to locate a key registry on the Internet. In DNS parlance, the information must be unique and authentic.

SO - Supporting Organizations

The SOs are the three specialized advisory bodies that advise the ICANN Board of Directors on issues relating to domain names (GNSO and CCNSO) and, IP addresses (ASO).

SSAC - Security and Stability Advisory Committee

An advisory committee to the ICANN Board comprised of technical experts from industry and academia as well as operators of Internet root servers, registrars and TLD registries.

TLD - Top-level Domain

TLDs are the names at the top of the DNS naming hierarchy. They appear in domain names as the string of letters following the last (rightmost) ".", such as "net" in "". The administrator for a TLD controls what second-level names are recognized in that TLD. The administrators of the "root domain" or "root zone" control what TLDs are recognized by the DNS. Commonly used TLDs include .COM, .NET, .EDU, .JP, .DE, etc.

UDRP - Uniform Dispute Resolution Policy

All ICANN-accredited registrars follow a Uniform Dispute Resolution Policy. Under that policy, disputes over entitlement to a domain-name registration are ordinarily resolved by court litigation between the parties claiming rights to the registration. Once the courts rule who is entitled to the registration, the registrar will implement that ruling. In disputes arising from registrations allegedly made abusively (such as "cybersquatting" and cyberpiracy"), the uniform policy provides an expedited administrative procedure to allow the dispute to be resolved without the cost and delays often encountered in court litigation. In these cases, you can invoke the administrative procedure by filing a complaint with one of the dispute- resolution service providers.

For more details on the UDRP, see the ICANN UDRP page and the Q/As.


WHOIS protocol (pronounced "who is"; not an acronym) An Internet protocol that is used to query databases to obtain information about the registration of a domain name (or IP address). The WHOIS protocol was originally specified in RFC 954, published in 1985. The current specification is documented in RFC 3912. ICANN's gTLD agreements require registries and registrars to offer an interactive web page and a port 43 WHOIS service providing free public access to data on registered names. Such data is commonly referred to as "WHOIS data," and includes elements such as the domain registration creation and expiration dates, nameservers, and contact information for the registrant and designated administrative and technical contacts.

WHOIS services are typically used to identify domain holders for business purposes and to identify parties who are able to correct technical problems associated with the registered domain.