Domain Name System Structure and Delegation
RFC 1591
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RFC - Informational
(March 1994; No errata)
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Jon Postel
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2013-03-02
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Legacy
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IESG |
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RFC 1591 (Informational)
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Network Working Group J. Postel
Request for Comments: 1591 ISI
Category: Informational March 1994
Domain Name System Structure and Delegation
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
1. Introduction
This memo provides some information on the structure of the names in
the Domain Name System (DNS), specifically the top-level domain
names; and on the administration of domains. The Internet Assigned
Numbers Authority (IANA) is the overall authority for the IP
Addresses, the Domain Names, and many other parameters, used in the
Internet. The day-to-day responsibility for the assignment of IP
Addresses, Autonomous System Numbers, and most top and second level
Domain Names are handled by the Internet Registry (IR) and regional
registries.
2. The Top Level Structure of the Domain Names
In the Domain Name System (DNS) naming of computers there is a
hierarchy of names. The root of system is unnamed. There are a set
of what are called "top-level domain names" (TLDs). These are the
generic TLDs (EDU, COM, NET, ORG, GOV, MIL, and INT), and the two
letter country codes from ISO-3166. It is extremely unlikely that
any other TLDs will be created.
Under each TLD may be created a hierarchy of names. Generally, under
the generic TLDs the structure is very flat. That is, many
organizations are registered directly under the TLD, and any further
structure is up to the individual organizations.
In the country TLDs, there is a wide variation in the structure, in
some countries the structure is very flat, in others there is
substantial structural organization. In some country domains the
second levels are generic categories (such as, AC, CO, GO, and RE),
in others they are based on political geography, and in still others,
organization names are listed directly under the country code. The
organization for the US country domain is described in RFC 1480 [1].
Postel [Page 1]
RFC 1591 Domain Name System Structure and Delegation March 1994
Each of the generic TLDs was created for a general category of
organizations. The country code domains (for example, FR, NL, KR,
US) are each organized by an administrator for that country. These
administrators may further delegate the management of portions of the
naming tree. These administrators are performing a public service on
behalf of the Internet community. Descriptions of the generic
domains and the US country domain follow.
Of these generic domains, five are international in nature, and two
are restricted to use by entities in the United States.
World Wide Generic Domains:
COM - This domain is intended for commercial entities, that is
companies. This domain has grown very large and there is
concern about the administrative load and system performance if
the current growth pattern is continued. Consideration is
being taken to subdivide the COM domain and only allow future
commercial registrations in the subdomains.
EDU - This domain was originally intended for all educational
institutions. Many Universities, colleges, schools,
educational service organizations, and educational consortia
have registered here. More recently a decision has been taken
to limit further registrations to 4 year colleges and
universities. Schools and 2-year colleges will be registered
in the country domains (see US Domain, especially K12 and CC,
below).
NET - This domain is intended to hold only the computers of network
providers, that is the NIC and NOC computers, the
administrative computers, and the network node computers. The
customers of the network provider would have domain names of
their own (not in the NET TLD).
ORG - This domain is intended as the miscellaneous TLD for
organizations that didn't fit anywhere else. Some non-
government organizations may fit here.
INT - This domain is for organizations established by international
treaties, or international databases.
United States Only Generic Domains:
GOV - This domain was originally intended for any kind of government
office or agency. More recently a decision was taken to
register only agencies of the US Federal government in this
domain. State and local agencies are registered in the country
Postel [Page 2]
RFC 1591 Domain Name System Structure and Delegation March 1994
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