The "_for-sale" Underscored and Globally Scoped DNS Node Name
draft-davids-forsalereg-09
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Marco Davids | ||
| Last updated | 2025-06-03 | ||
| RFC stream | Independent Submission | ||
| Intended RFC status | Informational | ||
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by James Gannon
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draft-davids-forsalereg-09
Internet Engineering Task Force (IETF) M. Davids
Internet-Draft SIDN Labs
Intended status: Best Current Practice 3 June 2025
Expires: 5 December 2025
The "_for-sale" Underscored and Globally Scoped DNS Node Name
draft-davids-forsalereg-09
Abstract
This document defines an operational convention for using the
reserved underscored DNS leaf node name "_for-sale" to indicate that
the parent domain name is available for purchase. This approach
offers the advantage of easy deployment without affecting ongoing
operations. As such, the method can be applied to a domain name that
is still in full use.
Note to the RFC Editor
This document contains several "Notes to the RFC Editor", including
this section. These should be reviewed and resolved prior to
publication.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 5 December 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. General Record Format . . . . . . . . . . . . . . . . . . 4
3.2. Content Tag Type Definitions . . . . . . . . . . . . . . 6
3.2.1. fcod . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2. ftxt . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2.3. furi . . . . . . . . . . . . . . . . . . . . . . . . 8
3.3. Content Limitations . . . . . . . . . . . . . . . . . . . 8
3.4. RRset Limitations . . . . . . . . . . . . . . . . . . . . 9
3.5. RR type Limitations . . . . . . . . . . . . . . . . . . . 9
3.6. Wildcard Limitation . . . . . . . . . . . . . . . . . . . 9
3.7. Placement of the Leaf Node Name . . . . . . . . . . . . . 9
4. Additional Examples . . . . . . . . . . . . . . . . . . . . . 10
4.1. Example 1: Code Format . . . . . . . . . . . . . . . . . 11
4.2. Example 2: Free Text Format . . . . . . . . . . . . . . . 11
4.3. Example 3: URI Format . . . . . . . . . . . . . . . . . . 11
4.4. Example 4: Combinations . . . . . . . . . . . . . . . . . 12
5. Operational Guidelines . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. Ethical Considerations . . . . . . . . . . . . . . . . . . . 15
10. Implementation Status . . . . . . . . . . . . . . . . . . . . 15
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
12.1. Normative References . . . . . . . . . . . . . . . . . . 16
12.2. Informative References . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
Well-established services [RFC3912][RFC9083] exist to determine
whether a domain name is registered. However, the fact that a domain
name exists does not necessarily mean it is unavailable; it may still
be for sale.
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Some registrars and other entities offer mediation services between
domain name holders and interested parties (often referred to as
brokers). For domain names that are not for sale, such services may
be of limited value, whereas they may be beneficial for domain names
that are clearly being offered for sale.
This specification defines a lightweight method to ascertain whether
a domain name, although registered, is available for purchase. It
enables a domain name holder to add a reserved underscored leaf node
name [RFC8552] in the zone, indicating that the domain name is for
sale.
The TXT RR type [RFC1035] created for this purpose MUST follow the
formal definition of Section 3. Its content MAY contain a pointer,
such as a Uniform Resource Identifier (URI) [RFC3986], or another
string, allowing interested parties to obtain information or contact
the domain name holder for further negotiations.
With due caution, such information can also be incorporated into
automated availability services. When checking a domain name for
availability, the service may indicate whether it is for sale and
provide a pointer to the seller's information.
Note: In this document, the term "for sale" is used in a broad sense
and MAY also refer to cases where the domain name is available for
lease, or where the contractual right to use the domain name is
offered to another party.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Rationale
There are undoubtedly more ways to address this problem space. The
reasons for the approach defined in this document are primarily
accessibility and simplicity. The indicator can be easily turned on
and off at will and moreover, it is immediately deployable and does
not require significant changes in existing services. This allows
for a smooth introduction of the concept.
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Furthermore, the chosen approach aligns with ethical considerations
by promoting a more equitable domain aftermarket and minimizing
potential for unintended commercial entanglements by registries, as
detailed in Section 9.
3. Conventions
3.1. General Record Format
Each "_for-sale" TXT record MUST begin with a version tag, optionally
followed by a string containing content that follows a simple
"tag=value" syntax.
The formal definition of the record format, using ABNF
[RFC5234][RFC7405], is as follows:
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forsale-record = forsale-version forsale-content
; referred to as content or RDATA
; in a single character-string
forsale-version = %s"v=FORSALE1;"
; %x76.3D.46.4F.52.53.41.4C.45.31.3B
; version tag, case sensitive, no spaces
forsale-content = fcod-pair / ftxt-pair / furi-pair
; referred to as tag-value pairs
; only one tag-value pair per record
fcod-pair = fcod-tag fcod-value
ftxt-pair = ftxt-tag ftxt-value
furi-pair = furi-tag furi-value
; the tags are referred to as content tags
; the values are referred to as content values
fcod-tag = %s"fcod="
ftxt-tag = %s"ftxt="
furi-tag = %s"furi="
; case sensitive lowercase
fcod-value = 1*239OCTET
; must be at least 1 OCTET
ftxt-value = 1*239ftxt-char
ftxt-char = %x20-21 / %x23-5B / %x5D-7E
; excluding " and \ to avoid escape issues
furi-value = URI
; Only http, https, mailto and tel schemes
; exactly one URI
URI = <as defined in RFC3986, Appendix A>
See Section 3.2 for more detailed format definitions per content tag
type.
Each "_for-sale" TXT record MUST NOT contain more than one tag-value
pair.
See Section 3.4 for additional RRset limitations.
The content value provides information to interested parties as
explained in Section 1.
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If no tag-value pair is present but a valid version tag is,
processors MAY assume that the domain is for sale. In such cases,
processors SHOULD determine how to proceed. One possible approach is
to indicate that the domain is for sale and to use traditional
methods, such as WHOIS or RDAP, to obtain contact information:
_for-sale.example.com. IN TXT "v=FORSALE1;"
If a tag-value pair is present but invalid, this constitutes a syntax
error and SHOULD be treated as if it were absent.
In such cases, if the version tag itself is valid, processors MAY
assume that the domain is for sale. For example:
_for-sale.example.com. IN TXT "v=FORSALE1;lorumipsum"
_for-sale.example.com. IN TXT "v=FORSALE1;fcod="
_for-sale.example.com. IN TXT "v=FORSALE1;foo=bar"
TXT records in the same RRset, but without a version tag, MUST NOT be
interpreted or processed as a valid "_for-sale" indicator. However,
they may still offer some additional information for humans when
considered alongside a valid record. For example:
_for-sale.example.com. IN TXT "I am for sale"
_for-sale.example.com. IN TXT "v=FORSALE1;fcod=XX-NGYyYjEyZWY"
If no TXT records at a leaf node contain a valid version tag,
processors MUST consider the node name invalid and discard it.
See Section 3.3 for additional content limitations.
3.2. Content Tag Type Definitions
A new registry for known content tags is created in Section 6, with
this document registering the initial set. Implementations SHOULD
process only registered tags they support, and MAY ignore any others.
The following content tags are defined as the initial valid content
tags.
3.2.1. fcod
This content tag is intended to contain a code that is meaningful
only to processors that understand its semantics. The content value
MUST consist of at least one octet.
The manner in which the "fcod=" content tag is used is determined by
agreement among cooperating parties.
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For example, a registry may allow registrars to enter a "for sale"
URL into their system. From that URL, a unique code is generated.
This code is inserted as the value of the "fcod=" content tag of the
"_for-sale" TXT record of a domain name, as shown in the example
below.
When a user checks the availability of the domain name using a
registry-provided tool (e.g., a web interface), the registry may use
the code to redirect the user to the appropriate "for sale" URL,
which may include a query component containing the domain name, for
example:
https://forsale-url.example.com/acme?d=example.org
The rationale for this approach is that controlling parties retain
authority over redirection URLs and any other information derived
from the content tag, thereby preventing users from being sent to
unintended or malicious destinations or from being presented with
unintended content.
The following example shows a base64-encoded [RFC4648] string
preceded by the prefix "ACME-" as the value of the content tag:
_for-sale IN TXT "v=FORSALE1;fcod=ACME-S2lscm95IHdhcyBoZXJl"
Note: As an implementation consideration, when multiple parties are
involved in the domain sale process and use the same mechanism, it
may be difficult to identify the relevant content in an RRset.
Adding a recognizable prefix to the content (e.g., "ACME-") is one
possible approach. However, this is left to the implementor, as it
is not enforced in this document. In this case, ACME would recognize
its content tag and interpret it as intended. This example uses
base64 encoding to avoid escaping and ensure printable characters,
though this is also not required.
3.2.2. ftxt
This content tag is intended to contain human-readable text that
conveys information to interested parties. For example:
_for-sale IN TXT "v=FORSALE1;ftxt=price:$500,info[at]example.com"
While a single visible character is the minimum, it is RECOMMENDED to
provide more context.
While a URI in this field is not syntactically prohibited, its
interpretation as a URI is not guaranteed. Use of URIs in this field
SHOULD be avoided in favor of the furi content tag.
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3.2.3. furi
This content tag is intended to contain a human-readable and machine-
parseable URI that conveys information to interested parties.
While the syntax allows any URI scheme, only the following schemes
are RECOMMENDED for use: http and https [RFC9110], mailto [RFC6068],
and tel [RFC3966].
The content value MUST contain exactly one URI. For example:
_for-sale IN TXT "v=FORSALE1;furi=https://example.com/foo%20bar"
URIs MUST conform to the syntax and encoding requirements specified
in Section 2.1 of [RFC3986], including the percent-encoding of
characters not allowed unencoded (for example, spaces MUST be encoded
as %20 in a URL).
See the Security Considerations section for possible risks.
3.3. Content Limitations
The "_for-sale" TXT record [RFC8553] (Section 2.1) MUST contain
content deemed valid under this specification.
Any text that suggests that the domain is not for sale is invalid
content. If a domain name is not for sale, a "_for-sale" indicator
is pointless and any existence of a valid "_for-sale" TXT record MAY
therefore be regarded as an indication that the domain name is for
sale.
The existence of a "_for-sale" leaf node does not obligate the holder
to sell the domain name; it may have been published in error, or
withdrawn later for other reasons.
This specification does not dictate the exact use of any content
values in the "_for-sale" TXT record. Parties - such as registries
and registrars - MAY use it in their tools, perhaps even by defining
specific requirements that the content value must meet. Content
values can also be represented in a human-readable format for
individuals to interpret. See the Additional Examples section for
clarification.
Since the content value in the TXT record has no strictly defined
meaning, it is up to the processor of the content to decide how to
handle it.
See Section 5 for additional guidelines.
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3.4. RRset Limitations
This specification does not define restrictions on the number of TXT
records in the RRset, but limiting it to one per content tag is
RECOMMENDED.
If this is not the case, the processor SHOULD determine which content
to use.
The RDATA [RFC9499] of each TXT record MUST consist of a single
character-string [RFC1035] with a maximum length of 255 octets, in
order to avoid the need to concatenate multiple character-strings
during processing.
The following example illustrates an invalid TXT record due to the
presence of multiple character-strings:
_for-sale IN TXT "v=FORSALE1;" "ftxt=foo" "bar" "invalid"
When multiple content TXT records present, the processor MAY select
one or more of them.
For example, a registry might extract content from an RRset that
includes a recognizable "fcod=" content tag and use it to direct
visitors to a sales page as part of its services. An individual, on
the other hand, might extract a phone number (if present) from a
"furi=" tag in the same RRset and use it to contact a potential
seller.
An example of such a combined record is provided in Section 4.4.
3.5. RR type Limitations
Adding any resource record (RR) types under the "_for-sale" leaf,
other than TXT (such as AAAA or HINFO), is unnecessary for the
purposes of this document and therefore discouraged.
3.6. Wildcard Limitation
Wildcards are only interpreted as leaf names, so _for-sale.*.example
is not a valid wildcard and is non-conformant.
3.7. Placement of the Leaf Node Name
The "_for-sale" leaf node name is primarily intended to indicate that
a domain name is available for purchase.
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For that, the leaf node name is to be placed on the top-level domain,
or any domain directly below. It can also be placed at a lower
level, when that level is mentioned in the Public Suffix List [PSL].
When the "_for-sale" leaf node name is placed elsewhere, the intent
is ambiguous.
Table 1 illustrates this:
+================================+================+================+
| Name | Situation | Verdict |
+================================+================+================+
| _for-sale.example. | root zone | For sale |
+--------------------------------+----------------+----------------+
| _for-sale.aaa.example. | second level | For sale |
+--------------------------------+----------------+----------------+
| _for-sale.acme.bbb.example. | bbb.example in | For sale |
| | PSL | |
+--------------------------------+----------------+----------------+
| _for-sale.www.ccc.example. | ccc.example | See note 1 |
| | not in PSL | |
+--------------------------------+----------------+----------------+
| _for-sale.51.198.in-addr.arpa. | infrastructure | See note 2 |
| | TLD | |
+--------------------------------+----------------+----------------+
| xyz._for-sale.example. | Invalid | non-conformant |
| | placement | |
+--------------------------------+----------------+----------------+
Table 1: Placements of TXT record
Note 1: When the "_for-sale" leaf node name is placed in front of a
label of a domain that is not in the PSL, it suggests that this label
(and everything underneath) is for sale, and not the domain name as a
whole. There may be use cases for this, but this situation is
considered unusual in the context of this document. Processors MAY
ignore such records.
Note 2: If a "_for-sale" leaf node were to appear under the .arpa
infrastructure top-level domain, it might be interpreted as an offer
to sell IP address space. However, such use is explicitly out of
scope for this document, and processors MUST ignore any such records.
4. Additional Examples
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4.1. Example 1: Code Format
A proprietary format, defined and used by agreement between parties -
for example, a registry and its registrars - without a clearly
specified meaning for third parties. For example, it may be used to
automatically redirect visitors to a web page, as described in
Section 3.2.1:
_for-sale IN TXT "v=FORSALE1;fcod=XX-aHR0cHM...wbGUuY29t"
4.2. Example 2: Free Text Format
Free format text, with some additional unstructured information,
aimed at being human-readable:
_for-sale IN TXT "v=FORSALE1;ftxt=price:EU500, call for info"
The content in the following example could be malicious, but it is
not in violation of this specification (see the Security
Considerations):
_for-sale IN TXT "v=FORSALE1;ftxt=<script>...</script>"
4.3. Example 3: URI Format
The holder of "example.com" wishes to signal that the domain is for
sale and adds this record to the "example.com" zone:
_for-sale IN TXT "v=FORSALE1;furi=https://example.com/fs?d=eHl6"
An interested party notices this signal and can visit the URI
mentioned for further information. The TXT record may also be
processed by automated tools, but see the Security Considerations
section for possible risks.
As an alternative, a mailto: URI could also be used:
_for-sale IN TXT "v=FORSALE1;furi=mailto:seller@example.com"
Or a telephone URI:
_for-sale IN TXT "v=FORSALE1;furi=tel:+1-201-555-0123"
There can be a use case for these URIs, especially since WHOIS (or
RDAP) often has privacy restrictions. But see the Privacy
Considerations section for possible downsides.
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4.4. Example 4: Combinations
An example of multiple valid TXT records from which a processor can
choose:
_for-sale IN TXT "v=FORSALE1;furi=https://fs.example.com/"
IN TXT "v=FORSALE1;ftxt=starting price:EU500"
IN TXT "v=FORSALE1;fcod=ACME-ZGVhZGJlZWYx"
IN TXT "v=FORSALE1;fcod=XYZ1-MTExLTIyMi0zMzMtNDQ0"
5. Operational Guidelines
DNS wildcards interact poorly with underscored names, and their use
is NOT RECOMMENDED with this mechanism. However, wildcards may still
be encountered in practice, especially with operators who are not
implementing this mechanism. This is why the version tag is a
REQUIRED element: it allows processors to distinguish valid "_for-
sale" records from unrelated TXT records.
Nonetheless, any assumptions about the content of "_for-sale" TXT
records SHOULD be made with caution, particularly in edge cases where
wildcard expansion - possibly combined with DNS aliases (e.g.,
CNAMEs) or redirections (e.g., DNAMEs [RFC6672]) - might result in
misleading listings or unintended references to third-party domains.
It is also RECOMMENDED that the content value be limited to visible
US-ASCII characters, excluding the double quote (") and backslash
(\).
In ABNF syntax, this would be:
forsale-content = 0*244recommended-char
recommended-char = %x20-21 / %x23-5B / %x5D-7E
Long TTLs [RFC1035] (Section 3.2.1) are discouraged as they increase
the risk of outdated data misleading buyers into thinking the domain
is still available.
Ambiguous constructs in content values SHOULD be avoided, as
illustrated by the following example:
_for-sale IN TXT "v=FORSALE1;fcod=TRIP-confusing;ftxt=dont-do-this"
The above example is a valid "fcod=" content tag that includes the
string ";ftxt=" in the content value, which may be confusing, as it
does not actually represent an "ftxt=" content tag.
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Because the format of the content part is not strictly defined in
this document, processors MAY apply the robustness principle of being
liberal in what they accept. This also applies to space characters
(%x20) immediately following the version tag. Alternatively, parties
may mutually agree on a more strictly defined proprietary format for
the content value to mitigate ambiguity.
Note that this mechanism only functions when the domain name is
active in the DNS, which is typically not the case, for example,
during a redemption period or while in pending delete status [STD69].
6. IANA Considerations
IANA has established the "Underscored and Globally Scoped DNS Node
Names" registry [RFC8552][IANA]. The underscored leaf node name
defined in this specification should be added as follows:
+=========+============+=============+
| RR Type | _NODE NAME | Reference |
+=========+============+=============+
| TXT | _for-sale | <this memo> |
+---------+------------+-------------+
Table 2: Entry for the
"Underscored and Globally Scoped
DNS Node Names" registry
<NOTE TO RFC EDITOR: Adjust the text in the table above before
publication with a citation for the (this) document making the
addition as per RFC8552.>
A registry group called "The '_for-sale' Underscored and Globally
Scoped DNS Node Name" [FORSALEREG] is to be created, along with a
registry called "Content Tags" within it. This registry group will
be maintained independently of IANA.
The registry is publicly accessible at:
https://forsalereg.sidnlabs.nl/
The registry entries consist of content tags as defined in
Section 3.2.
The initial set of entries in this registry is as follows:
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+==========+===========+========+===========================+
| Tag Name | Reference | Status | Description |
+==========+===========+========+===========================+
| fcod | RFCXXXX | active | For Sale Proprietary Code |
+----------+-----------+--------+---------------------------+
| ftxt | RFCXXXX | active | For Sale Free Format Text |
+----------+-----------+--------+---------------------------+
| furi | RFCXXXX | active | For Sale URI |
+----------+-----------+--------+---------------------------+
Table 3: Initial set of entries in the "Content Tags"
registry
<NOTE TO RFC EDITOR: Adjust the text in the table above before
publication with a citation for the (this) document making the
addition as per RFC8552.>
Future updates will be managed by the Designated Expert.
Entries are assigned only for values that have been documented in a
manner consistent with the "Specification Required" registration
policy defined in [RFC8126].
Newly defined content tags MUST NOT alter the semantics of existing
content tags.
The addition of a new content tag to the registered list does not
require the definition of a new version tag. However, any
modification to existing content tags does.
The "status" column can have one of the following values:
* active - the tag is in use in current implementations.
* historic - the tag is deprecated and not expected to be used in
current implementations.
This registry group is not maintained by IANA as per [RFC8726].
7. Privacy Considerations
The use of the "_for-sale" leaf node name publicly indicates the
intent to sell a domain name. Domain holders should be aware that
this information is accessible to anyone querying the DNS and may
have privacy implications.
There is a risk of data scraping, such as email addresses and phone
numbers.
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8. Security Considerations
One use of the TXT record type defined in this document is to parse
the content it contains and to automatically publish certain
information from it on a website or elsewhere. However, there is a
risk if the domain name holder publishes a malicious URI or one that
points to improper content. This may result in reputational damage
for the party parsing the record.
An even more serious scenario arises when the content of the TXT
record is insufficiently validated and sanitized, potentially
enabling attacks such as XSS or SQL injection.
Therefore, it is RECOMMENDED that any parsing and publishing is
conducted with the utmost care.
There is also a risk that this method will be abused as a marketing
tool, or to lure individuals into visiting certain sites or making
contact by other means, without there being any intention to actually
sell the domain name. Therefore, this method is best suited for use
by professionals.
9. Ethical Considerations
Although not specifically designed for this purpose, the mechanisms
described in this document may also facilitate domain name
transactions by professional speculators, often referred to as
domainers, and those commonly referred to as domain drop catchers.
Some may view this as controversial.
However, by enabling domain holders to more explicitly signal their
intent to sell, the proposed approach aims to introduce greater
clarity and predictability into the domain lifecycle. This
potentially reduces the advantage currently held by these
professionals, and fosters a more equitable environment for all.
Furthermore, this mechanism avoids creating unnecessary dependencies
on registries for market transactions, which could otherwise
introduce complexities and potential for unintended commercial
entanglements.
10. Implementation Status
The concept described in this document is in use with the .nl ccTLD
registry. See for example:
https://www.sidn.nl/en/whois?q=example.nl
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The Dutch registry SIDN offers registrars the option to register a
sales landing page via its registrar dashboard following the "fcod="
method. When this option is used, a unique code is generated, which
can be included in the "_for-sale" record. If such a domain name is
entered on the domain finder page of SIDN, a "for sale" button is
displayed accordingly.
A simple demonstration of a validator is present at:
https://forsalereg.sidnlabs.nl/demo
<NOTE TO RFC EDITOR: Please remove this section before publication as
per RFC7942.>
11. Acknowledgements
The author would like to thank Thijs van den Hout, Caspar Schutijser,
Melvin Elderman, Paul Bakker, Ben van Hartingsveldt, Jesse Davids,
Juan Stelling and the ISE Editor for their valuable feedback.
12. References
12.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
RFC 7405, DOI 10.17487/RFC7405, December 2014,
<https://www.rfc-editor.org/info/rfc7405>.
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[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8552] Crocker, D., "Scoped Interpretation of DNS Resource
Records through "Underscored" Naming of Attribute Leaves",
BCP 222, RFC 8552, DOI 10.17487/RFC8552, March 2019,
<https://www.rfc-editor.org/info/rfc8552>.
12.2. Informative References
[FORSALEREG]
SIDN Labs, "The "_for-sale" Underscored and Globally
Scoped DNS Node Name",
<https://forsalereg.sidnlabs.nl/forsale-parameters>.
[IANA] IANA, "Underscored and Globally Scoped DNS Node Names",
<https://www.iana.org/assignments/dns-parameters/dns-
parameters.xml#underscored-globally-scoped-dns-node-
names>.
[PSL] Mozilla Foundation, "Public Suffix List",
<https://publicsuffix.org/>.
[RFC3912] Daigle, L., "WHOIS Protocol Specification", RFC 3912,
DOI 10.17487/RFC3912, September 2004,
<https://www.rfc-editor.org/info/rfc3912>.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, DOI 10.17487/RFC3966, December 2004,
<https://www.rfc-editor.org/info/rfc3966>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
URI Scheme", RFC 6068, DOI 10.17487/RFC6068, October 2010,
<https://www.rfc-editor.org/info/rfc6068>.
[RFC6672] Rose, S. and W. Wijngaards, "DNAME Redirection in the
DNS", RFC 6672, DOI 10.17487/RFC6672, June 2012,
<https://www.rfc-editor.org/info/rfc6672>.
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[RFC8553] Crocker, D., "DNS Attrleaf Changes: Fixing Specifications
That Use Underscored Node Names", BCP 222, RFC 8553,
DOI 10.17487/RFC8553, March 2019,
<https://www.rfc-editor.org/info/rfc8553>.
[RFC8726] Farrel, A., "How Requests for IANA Action Will Be Handled
on the Independent Stream", RFC 8726,
DOI 10.17487/RFC8726, November 2020,
<https://www.rfc-editor.org/info/rfc8726>.
[RFC9083] Hollenbeck, S. and A. Newton, "JSON Responses for the
Registration Data Access Protocol (RDAP)", STD 95,
RFC 9083, DOI 10.17487/RFC9083, June 2021,
<https://www.rfc-editor.org/info/rfc9083>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
[RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219,
RFC 9499, DOI 10.17487/RFC9499, March 2024,
<https://www.rfc-editor.org/info/rfc9499>.
[STD69] Internet Standard 69,
<https://www.rfc-editor.org/info/std69>.
At the time of writing, this STD comprises the following:
Hollenbeck, S., "Extensible Provisioning Protocol (EPP)",
STD 69, RFC 5730, DOI 10.17487/RFC5730, August 2009,
<https://www.rfc-editor.org/info/rfc5730>.
Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Domain Name Mapping", STD 69, RFC 5731,
DOI 10.17487/RFC5731, August 2009,
<https://www.rfc-editor.org/info/rfc5731>.
Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Host Mapping", STD 69, RFC 5732, DOI 10.17487/RFC5732,
August 2009, <https://www.rfc-editor.org/info/rfc5732>.
Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Contact Mapping", STD 69, RFC 5733, DOI 10.17487/RFC5733,
August 2009, <https://www.rfc-editor.org/info/rfc5733>.
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Hollenbeck, S., "Extensible Provisioning Protocol (EPP)
Transport over TCP", STD 69, RFC 5734,
DOI 10.17487/RFC5734, August 2009,
<https://www.rfc-editor.org/info/rfc5734>.
Author's Address
Marco Davids
SIDN Labs
Meander 501
6825 MD Arnhem
Netherlands
Phone: +31 26 352 5500
Email: marco.davids@sidn.nl
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