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Keywords: DNS, Policy, Top-Level, TLD
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].
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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
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RFC 1591 Domain Name System Structure and Delegation March 1994
domains (see US Domain, below).
MIL - This domain is used by the US military.
Example country code Domain:
US - As an example of a country domain, the US domain provides for
the registration of all kinds of entities in the United States
on the basis of political geography, that is, a hierarchy of
<entity-name>.<locality>.<state-code>.US. For example,
"IBM.Armonk.NY.US". In addition, branches of the US domain are
provided within each state for schools (K12), community colleges
(CC), technical schools (TEC), state government agencies
(STATE), councils of governments (COG),libraries (LIB), museums
(MUS), and several other generic types of entities (see RFC 1480
for details [1]).
To find a contact for a TLD use the "whois" program to access the
database on the host rs.internic.net. Append "-dom" to the name of
TLD you are interested in. For example:
whois -h rs.internic.net us-dom
or
whois -h rs.internic.net edu-dom
3. The Administration of Delegated Domains
The Internet Assigned Numbers Authority (IANA) is responsible for the
overall coordination and management of the Domain Name System (DNS),
and especially the delegation of portions of the name space called
top-level domains. Most of these top-level domains are two-letter
country codes taken from the ISO standard 3166.
A central Internet Registry (IR) has been selected and designated to
handled the bulk of the day-to-day administration of the Domain Name
System. Applications for new top-level domains (for example, country
code domains) are handled by the IR with consultation with the IANA.
The central IR is INTERNIC.NET. Second level domains in COM, EDU,
ORG, NET, and GOV are registered by the Internet Registry at the
InterNIC. The second level domains in the MIL are registered by the
DDN registry at NIC.DDN.MIL. Second level names in INT are
registered by the PVM at ISI.EDU.
While all requests for new top-level domains must be sent to the
Internic (at hostmaster@internic.net), the regional registries are
often enlisted to assist in the administration of the DNS, especially
in solving problems with a country administration. Currently, the
RIPE NCC is the regional registry for Europe and the APNIC is the
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RFC 1591 Domain Name System Structure and Delegation March 1994
regional registry for the Asia-Pacific region, while the INTERNIC
administers the North America region, and all the as yet undelegated
regions.
The contact mailboxes for these regional registries are:
INTERNIC hostmaster@internic.net
APNIC hostmaster@apnic.net
RIPE NCC ncc@ripe.net
The policy concerns involved when a new top-level domain is
established are described in the following. Also mentioned are
concerns raised when it is necessary to change the delegation of an
established domain from one party to another.
A new top-level domain is usually created and its management
delegated to a "designated manager" all at once.
Most of these same concerns are relevant when a sub-domain is
delegated and in general the principles described here apply
recursively to all delegations of the Internet DNS name space.
The major concern in selecting a designated manager for a domain is
that it be able to carry out the necessary responsibilities, and have
the ability to do a equitable, just, honest, and competent job.
1) The key requirement is that for each domain there be a designated
manager for supervising that domain's name space. In the case of
top-level domains that are country codes this means that there is
a manager that supervises the domain names and operates the domain
name system in that country.
The manager must, of course, be on the Internet. There must be
Internet Protocol (IP) connectivity to the nameservers and email
connectivity to the management and staff of the manager.
There must be an administrative contact and a technical contact
for each domain. For top-level domains that are country codes at
least the administrative contact must reside in the country
involved.
2) These designated authorities are trustees for the delegated
domain, and have a duty to serve the community.
The designated manager is the trustee of the top-level domain for
both the nation, in the case of a country code, and the global
Internet community.
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RFC 1591 Domain Name System Structure and Delegation March 1994
Concerns about "rights" and "ownership" of domains are
inappropriate. It is appropriate to be concerned about
"responsibilities" and "service" to the community.
3) The designated manager must be equitable to all groups in the
domain that request domain names.
This means that the same rules are applied to all requests, all
requests must be processed in a non-discriminatory fashion, and
academic and commercial (and other) users are treated on an equal
basis. No bias shall be shown regarding requests that may come
from customers of some other business related to the manager --
e.g., no preferential service for customers of a particular data
network provider. There can be no requirement that a particular
mail system (or other application), protocol, or product be used.
There are no requirements on subdomains of top-level domains
beyond the requirements on higher-level domains themselves. That
is, the requirements in this memo are applied recursively. In
particular, all subdomains shall be allowed to operate their own
domain name servers, providing in them whatever information the
subdomain manager sees fit (as long as it is true and correct).
4) Significantly interested parties in the domain should agree that
the designated manager is the appropriate party.
The IANA tries to have any contending parties reach agreement
among themselves, and generally takes no action to change things
unless all the contending parties agree; only in cases where the
designated manager has substantially mis-behaved would the IANA
step in.
However, it is also appropriate for interested parties to have
some voice in selecting the designated manager.
There are two cases where the IANA and the central IR may
establish a new top-level domain and delegate only a portion of
it: (1) there are contending parties that cannot agree, or (2) the
applying party may not be able to represent or serve the whole
country. The later case sometimes arises when a party outside a
country is trying to be helpful in getting networking started in a
country -- this is sometimes called a "proxy" DNS service.
The Internet DNS Names Review Board (IDNB), a committee
established by the IANA, will act as a review panel for cases in
which the parties can not reach agreement among themselves. The
IDNB's decisions will be binding.
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RFC 1591 Domain Name System Structure and Delegation March 1994
5) The designated manager must do a satisfactory job of operating the
DNS service for the domain.
That is, the actual management of the assigning of domain names,
delegating subdomains and operating nameservers must be done with
technical competence. This includes keeping the central IR (in
the case of top-level domains) or other higher-level domain
manager advised of the status of the domain, responding to
requests in a timely manner, and operating the database with
accuracy, robustness, and resilience.
There must be a primary and a secondary nameserver that have IP
connectivity to the Internet and can be easily checked for
operational status and database accuracy by the IR and the IANA.
In cases when there are persistent problems with the proper
operation of a domain, the delegation may be revoked, and possibly
delegated to another designated manager.
6) For any transfer of the designated manager trusteeship from one
organization to another, the higher-level domain manager (the IANA
in the case of top-level domains) must receive communications from
both the old organization and the new organization that assure the
IANA that the transfer in mutually agreed, and that the new
organization understands its responsibilities.
It is also very helpful for the IANA to receive communications
from other parties that may be concerned or affected by the
transfer.
4. Rights to Names
1) Names and Trademarks
In case of a dispute between domain name registrants as to the
rights to a particular name, the registration authority shall have
no role or responsibility other than to provide the contact
information to both parties.
The registration of a domain name does not have any Trademark
status. It is up to the requestor to be sure he is not violating
anyone else's Trademark.
2) Country Codes
The IANA is not in the business of deciding what is and what is
not a country.
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RFC 1591 Domain Name System Structure and Delegation March 1994
The selection of the ISO 3166 list as a basis for country code
top-level domain names was made with the knowledge that ISO has a
procedure for determining which entities should be and should not
be on that list.
5. Security Considerations
Security issues are not discussed in this memo.
6. Acknowledgements
Many people have made comments on draft version of these descriptions
and procedures. Steve Goldstein and John Klensin have been
particularly helpful.
7. Author's Address
Jon Postel
USC/Information Sciences Institute
4676 Admiralty Way
Marina del Rey, CA 90292
Phone: 310-822-1511
Fax: 310-823-6714
EMail: Postel@ISI.EDU
7. References
[1] Cooper, A., and J. Postel, "The US Domain", RFC 1480,
USC/Information Sciences Institute, June 1993.
[2] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC 1340,
USC/Information Sciences Institute, July 1992.
[3] Mockapetris, P., "Domain Names - Concepts and Facilities", STD
13, RFC 1034, USC/Information Sciences Institute, November 1987.
[4] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, USC/Information Sciences
Institute, November 1987.
[6] Partridge, C., "Mail Routing and the Domain System", STD 14, RFC
974, CSNET CIC BBN, January 1986.
[7] Braden, R., Editor, "Requirements for Internet Hosts --
Application and Support", STD 3, RFC 1123, Internet Engineering
Task Force, October 1989.
Postel [Page 7]