Relative Labels in the Domain Name System
draft-yocto-dns-relative-label-02
This document is an Internet-Draft (I-D).
Anyone may submit an I-D to the IETF.
This I-D is not endorsed by the IETF and has no formal standing in the
IETF standards process.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Ben van Hartingsveldt | ||
| Last updated | 2024-07-26 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources |
GitHub Repository
|
||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-yocto-dns-relative-label-02
Network Working Group B.J. van Hartingsveldt
Internet-Draft Yocto
Intended status: Informational 26 July 2024
Expires: 27 January 2025
Relative Labels in the Domain Name System
draft-yocto-dns-relative-label-02
Abstract
This document defines a new DNS Label Type using the Extension
Mechanisms for DNS to indicate when a relative domain name is used.
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 27 January 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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.
van Hartingsveldt Expires 27 January 2025 [Page 1]
Internet-Draft DNS Relative Labels July 2024
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Label Format . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. Wire format . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Representation format . . . . . . . . . . . . . . . . . . 3
4.3. Examples . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Canonical Representation . . . . . . . . . . . . . . . . . . 3
6. Implementation . . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8. Security Considerations . . . . . . . . . . . . . . . . . . . 4
9. Normative References . . . . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
This document defines a "Relative Label" which may appear within
domain names. This new label type enables resource records to be
used with their relative form (e.g. "www" instead of
"www.example.com.").
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Motivation
Relative labels are intended to efficiently solve the problem of
using FQDNs when a relative label is wanted. For example, when
someone wants to add the MX resource record "0 mx" instead of "0
mx.example.com." to a zone using DNS UPDATE [RFC2136]. It is also
useful for DNS providers that store all the records in binary format.
Saving data in binary requires less space and the data is already in
wire format, but at the moment there is no way to save relative
domains in their binary form.
van Hartingsveldt Expires 27 January 2025 [Page 2]
Internet-Draft DNS Relative Labels July 2024
4. Label Format
Relative labels can only appear in the end of a relative FQDN, like
the zero octet only appears in the end of an absolute FQDN. [TODO:
MOVE -->] Message compression is possible when also using the
relative label, but because the relative label already gives the
possibility to leave out the zone name, message compression will
likely have less effect.
4.1. Wire format
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|0 1| ELT |
+-+-+-+-+-+-+-+-+
Figure 1
ELT 000000 binary, the six-bit extended label type [RFC6891]
assigned to the Relative Label.
4.2. Representation format
As described in [RFC1035], relative domain names are domain names
that don't end with a dot.
4.3. Examples
When an absolute domain name like "www.example.com." is converted to
binary, its hexadecimal representation would be: "<03> 77 77 77 <07>
65 78 61 6D 70 6C 65 <03> 63 6F 6D <00>". The square brackets
indicate the label lengths.
When converting a relative domain name like "www.subdomain" to
binary, its hexadecimal representation becomes: "<03> 77 77 77 <09>
73 75 62 64 6F 6D 61 69 6E <40>". The square brackets also indicate
the labels lengths here, except for "<40>", which is the extended
label type defined by this specification.
5. Canonical Representation
Relative domain names do not contain the zone they belong to. For
the resource records, in order to be queried with the QUERY opcode or
sorted for DNSSEC [RFC4033], at some moment the records should be
converted to their canonical form. To be able to do that, the
absolute form of the domain name should be known.
van Hartingsveldt Expires 27 January 2025 [Page 3]
Internet-Draft DNS Relative Labels July 2024
To retrieve the absolute domain name from a relative domain name, the
containing zone MUST be known from context. In DNS UPDATE [RFC2136],
the zone is sent in the zone section, which a renaming of the
question section. When using binary zone files, the zone will likely
be encoded in the file header or the file name.
On binary level, to get the absolute form of the domain name, the
last byte of the relative domain name, 0x40, MUST be removed. Then,
the binary form of the zone name MUST be appended. For example,
"<03> 77 77 77 <40>" (www) and "<07> 65 78 61 6D 70 6C 65 <03> 63 6F
6D <00>" (example.com.), will become "<03> 77 77 77 <07> 65 78 61 6D
70 6C 65 <03> 63 6F 6D <00>" (www.example.com.).
Relative labels should be avoided in QUERY results, because clients
MAY not support it. Also, for supporting clients, it is impossible
know which zone the resource records belong to. For AXFR and IXFR,
it is possible to know the zone, so using the relative label for
those queries MAY be considered.
6. Implementation
Implementation is OPTIONAL, so clients SHOULD NOT expect every server
to support this feature. An indicator MAY BE added in the future for
servers to indicate that they support relative labels and for which
resource record types.
7. IANA Considerations
This document defines one Extended Label Type, termed the Relative
Label, and requests registration of the code point 000000 binary in
the space defined by [RFC6891].
8. Security Considerations
All security considerations which apply to traditional ASCII DNS
labels apply equally to binary labels. The canonicalization and
sorting rules of section 3.3 allow these to be addressed by DNS
Security [RFC4033].
9. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", RFC 1035, DOI 10.17487/RFC1035, November
1987, <https://www.rfc-editor.org/rfc/rfc1035>.
van Hartingsveldt Expires 27 January 2025 [Page 4]
Internet-Draft DNS Relative Labels July 2024
[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/rfc/rfc2119>.
[RFC2136] Vixie, P., "Dynamic Updates in the Domain Name System (DNS
UPDATE)", RFC 2136, DOI 10.17487/RFC2136, April 1997,
<https://www.rfc-editor.org/rfc/rfc2136>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005,
<https://www.rfc-editor.org/rfc/rfc4033>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", RFC 6891, DOI 10.17487/6891, April
2013, <https://www.rfc-editor.org/rfc/rfc6891>.
Appendix A. Acknowledgements
The author gratefully acknowledges the contributions and feedback of
Alexander Robohm, Edward Lewis, Joe Abley, Mukund Sivaraman, Ondřej
Surý, Tim Wicinski, Peter Thomassen, and Marco Davids.
As well as all of those in the IETF community and on GitHub to who
contributed to the discussions that resulted in this document.
Author's Address
B.J. van Hartingsveldt
Yocto
Email: ben.vanhartingsveldt@yocto.com
van Hartingsveldt Expires 27 January 2025 [Page 5]