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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  Name Systems and TCP/IP Name Registration and Name Resolution
           9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)
                9  TCP/IP Domain Name System (DNS)
                     9  DNS Name Registration, Public Administration, Zones and Authorities

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DNS Hierarchical Authority Structure and the Distributed Name Database
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DNS Geopolitical (Country Code) Top Level Domains and Authorities
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DNS Organizational (Generic) Top Level Domains and Authorities
(Page 4 of 4)

Summary of Organizational (Generic) TLDs

Table 165 shows all the current generic TLDs and describes how they are used, and also lists the current central authority that manages each. The original TLDs are highlighted in italics (I am including .INT as an original TLD since it was created long before the “new” ones earlier this decade). Figure 239 shows the fifteen generic TLDs in graphical form.

Table 165: Internet DNS Organizational (Generic) Top-Level Domains

Generic TLD

Abbreviation For


Current Use / Description



Société Internationale de Télécommunications Aéronautiques (SITA)

Members of the aerospace industry, such as airlines and airports. (Yes, that is French!)


and Routing Parameter Area

Internet Assigned Numbers Authority (IANA) / Internet Corporation for Assigned Names and Numbers (ICANN)

First defined as a temporary domain for migration from the older host table system, the “ARPA” of course originally stood for the Advanced Research Projects Agency, creators of the predecessors of the Internet. Today, the .ARPA domain is used for internal Internet management purposes; the abbreviation at left was, I believe, “manufactured” to fit the letters “ARPA”. J The best-known use of this domain is for reverse DNS lookups.



NeuLevel, Inc.

Businesses. Intended as a competitor to .COM.


Commercial Organizations

VeriSign Global Registry Services

Originally intended for corporations and other commercial interests, .COM is also widely used for other purposes, including small businesses and even individuals who like the popularity of the .COM domain.


Cooperative Associations

Dot Cooperation LLC

Cooperative associations.




Originally intended for all types of educational organizations, now used only for degree-granting higher education institutions accredited in the United States. Other educational institutions such as public schools usually use the country code TLDs.



US General Services Administration

Reserved for the United States federal government.



Afilias Limited

A very generic TLD designed for information resources of various sorts. It is unrestricted, in that anyone can register any sort of organization in .INFO. Also positioned as an alternative to .COM.



IANA .int Domain Registry

Used only for large organizations established by international treaty.



US DoD Network Information Center

Reserved for the United States military.



Museum Domain Management Association

Take a guess. J



Global Name Registry

In the original generic hierarchy there was no place set aside for individuals to register names for themselves, so people would instead create domains like “”. This was non-ideal so .NAME was created as a place for individuals and families to register a domain for their names. .NAME also competes with the country code TLDs.



VeriSign Global Registry Services

This TLD was supposed to be used only for Internet service providers and other organizations working intimately with the Internet or networking. Due to the exhaustion of name space in .COM and .ORG, many .NET domains are registered to other organizations, however.



Public Interest Registry

Originally intended for organizations not fitting into the other generic TLDs, .ORG quickly became associated with professional and non-profit organizations. It is possible, however, to have a for-profit company use a .ORG name.




Reserved for credentialed professionals such as lawyers and doctors.

Figure 239: Internet DNS Organizational (Generic) Top-Level Domains (TLDs)

There are fifteen generic TLDs currently defined for the Internet. They have been shown here in alphabetical order, with the original TLDs shown in blue and the new ones added in 2001/2002 in green.


Key Concept: One of the two ways in which the Internet’s DNS name space is divided is using a set of generic top-level domains. These TLDs are intended to provide a place for all companies and organizations to be named based on their organization type. There were originally six such domains, but this has been expanded so that there are now fifteen.

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DNS Hierarchical Authority Structure and the Distributed Name Database
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Version 3.0 - Version Date: September 20, 2005

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