Top-level Domains for Private Internets
Independent Submission R. Arends
Intended status: Best Current Practice J. Abley
Expires: April 11, 2021 Public Interest Registry
October 08, 2020
Top-level Domains for Private Internets
There are no defined private-use namespaces in the Domain Name System
(DNS). For a domain name to be considered private-use, it needs to
be future-proof in that its top-level domain will never be delegated
from the root zone. The lack of a private-use namespace has led to
locally configured namespaces with a top-level domain that is not
The DNS needs an equivalent of the facilities provided by BCP 5 (RFC
1918) for private internets, i.e. a range of short, semantic-free
top-level domains that can be used in private internets without the
risk of being globally delegated from the root zone.
The ISO 3166 standard is used for the definition of eligible
designations for country-code top-level Domains. This standard is
maintained by the ISO 3166 Maintenance Agency. The ISO 3166 standard
includes a set of user-assigned code elements that can be used by
those who need to add further names to their local applications.
Because of the rules set out by ISO in their standard, it is
extremely unlikely that these user-assigned code elements would ever
conflict with delegations in the root zone under current practices.
This document explicitly reserves these code elements to be safely
used as top-level domains for private DNS resolution.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 11, 2021.
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Table of Contents
2. The ISO 3166-1 alpha-2 and Two-Letter Top-Level Domains
3. ISO 3166-1 alpha-2 User-assigned Code Elements
4. Examples of Current Uses of the User-assigned Code Elements.
5. Private-use top-level Domains
6. IANA Considerations
7. Security Considerations
9. Informative References
In private networks where a hostname has no utility in the global
namespace, it is convenient to have a private-use namespace. Such
deployments could theoretically use sub-domains of a domain
registered for the specific hosting entity, though not all such
configurations have such a domain available. When the hostname is
solely used in a private network, it is not necessary that it
Another situation is where applications use identifiers that are
similar in appearance to domain names, and may be interpreted by
software as domain names, but are not intended to use the global DNS
resolution service. Using a private-use namespace helps guard
against conflicts with the global DNS resolution system.
Note that a private-use namespace is not a subset of a registered
special use namespace [IANA-Special]. There is no facility to
register a specific label using the process defined in [RFC6761].
The process in RFC 6761 requires that a label has some kind of
special handling in order to be considered special. A private-use
namespace can be considered special on a policy level, but not on a
technical or protocol level.
Many protocols outside the DNS have a defined set of elements for
private use, or an identifier that indicates private use, such as
"X-headers" MIME types [RFC2045], addresses for private internets
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