RFC 1591 (rfc1591) - Page 1 of 7
Domain Name System Structure and Delegation
Alternative Format: Original Text Document
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
