Clarifications to the DNS Ranking Data
draft-fujiwara-dnsop-ranking-data-01
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) | |
|---|---|---|---|
| Authors | Kazunori Fujiwara , Willem Toorop | ||
| Last updated | 2026-03-02 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| 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-fujiwara-dnsop-ranking-data-01
Network Working Group K. Fujiwara
Internet-Draft JPRS
Updates: 2181 (if approved) W. Toorop
Intended status: Standards Track NLnet Labs
Expires: 3 September 2026 2 March 2026
Clarifications to the DNS Ranking Data
draft-fujiwara-dnsop-ranking-data-01
Abstract
This document obsoletes Section 5.4.1 (Ranking data) of RFC 2181, and
specifies directives whereby the source of the data determines for
what purposes it may be 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 3 September 2026.
Copyright Notice
Copyright (c) 2026 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.
Fujiwara & Toorop Expires 3 September 2026 [Page 1]
Internet-Draft ranking March 2026
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 2
4. Directives . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Additional Considerations . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The DNS server assumed in Section 5.4.1 (Ranking data) of [RFC2181]
is considered to be a model with a shared database described in
Section 2.2 (Common configurations) of [RFC1035] that has both
Authoritative server and Recursive Resolver functions. It is assumed
that information obtained from zone files, zone transfers, and name
resolution will be mixed together.
However, at the time of writing, this is no longer the practice of
name servers and resolvers. Zone transfers transfer the same data
from primaries to secondary servers without any modification. An
authoritative name server function does not mix and return
information obtained from name resolution.
2. 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.
Many of the specialized terms used in this document are defined in
DNS Terminology [RFC9499].
3. Problem Statement
In the past, recursive resolvers would return data from referral
responses, such as delegation information or glue, in the answer
section of responses; however, modern recursive resolvers complete
name resolution with an authoritative response from an authoritative
server that has authority through delegation. However, there is no
clear documentation of this.
Fujiwara & Toorop Expires 3 September 2026 [Page 2]
Internet-Draft ranking March 2026
"The Ranking Data" only indicates the priority among data, not its
validity. Attacks using responses that do not correspond to queries
and additional data that is not required have been considered and
reported, so unnecessary data should be discarded.
[RFC1034] already describes resolver's answer as follows.
"The ideal answer is one from a server authoritative for the query
which either gives the required data or a name error. The data is
passed back to the user and entered in the cache for future use if
its TTL is greater than zero." (Quoted from RFC 1034, Section 5.3.3)
"The simplest mode for the client is recursive, since in this mode
the name server acts in the role of a resolver and returns either an
error or the answer, but never referrals." (Quoted from RFC 1034,
Section 4.3.1)
Currently, responses from authoritative servers are considered to
include authoritative name resolution results (NXDOMAIN, NODATA, the
RRSet requested), non-authoritative delegation information,
unnecessary data, and other types of errors, and each of these is
considered to affect how resolvers handle the data. Therefore,
directives on how to handle the data are needed.
4. Directives
1. Authoritative servers MUST NOT merge zone data. (zone data should
be retrieved from a source (zone file, internal database, zone
transfer)
2. Name resolution results (Answer section, or NXDOMAIN, NODATA)
MUST be authoritative responses from authoritative servers that
has authority through delegation.
3. Non-authoritative responses (referral/delegation responses) from
authoritative servers MUST only be used to query the delegated
authoritative server during the name resolution.
4. Names and IP addresses of the authoritative name servers for
zones (such as the root zone) that are built-in or loaded from
"hints" files, MUST only be used for priming a resolver for those
zones [RFC9609].
5. Multi-function name server
Fujiwara & Toorop Expires 3 September 2026 [Page 3]
Internet-Draft ranking March 2026
Name servers with multiple functions will act as an
Authoritative, Recursive Resolver (Full-Service Resolver), or
Forwarder depending on the namespace to which the query name
belongs, the server IP address, the "Recursion Desired" bit, etc.
The data handled by each function MUST be separated.
5. Additional Considerations
[ Further directives could be made, they may be DNS software
implementation guidelines, which would be large in scale, so it is
necessary to consider whether to proceed with them. ]
* If a DNS server plays different roles for different namespaces
(authoritative server, recursive resolver, forwarder), it MUST NOT
merge DNS data for each role.
For example, a recursive resolver that returns a fixed zone as a
split-horizon DNS can be interpreted as acting as an authoritative
server below a certain domain name, but as a recursive resolver
otherwise.
* The Additional Section returned as the result of name resolution
MUST be exactly the same as the Additional Section that came from
the authoritative response from the authoritative server, or a
separate authoritative response resulting from name resolution.
* Full-service resolvers SHOULD only accept the following data from
authoritative servers:
- NS and DS RRSets (+RRSIG) in the Authority Section of the
delegation response and Glue A/AAAA in the Additional Section,
- SOA RRs (+RRSIG) in the Authority Section of authoritative
NXDOMAIN and NODATA responses in response to the query,
- the Answer Section (+RRSIG) of the authoritative response in
response to the query, and
- any additional sections allowed by type (delegated domain
name),
and SHOULD NOT accept any other information.
6. IANA Considerations
This document requests no IANA actions.
Fujiwara & Toorop Expires 3 September 2026 [Page 4]
Internet-Draft ranking March 2026
7. Security Considerations
8. Normative References
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/rfc/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/rfc/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/rfc/rfc2119>.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
<https://www.rfc-editor.org/rfc/rfc2181>.
[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/rfc/rfc8174>.
[RFC9499] Hoffman, P. and K. Fujiwara, "DNS Terminology", BCP 219,
RFC 9499, DOI 10.17487/RFC9499, March 2024,
<https://www.rfc-editor.org/rfc/rfc9499>.
[RFC9609] Koch, P., Larson, M., and P. Hoffman, "Initializing a DNS
Resolver with Priming Queries", BCP 209, RFC 9609,
DOI 10.17487/RFC9609, February 2025,
<https://www.rfc-editor.org/rfc/rfc9609>.
Authors' Addresses
Kazunori Fujiwara
Japan Registry Services Co., Ltd.
Japan
Email: fujiwara@jprs.co.jp
Willem Toorop
NLnet Labs
Science Park 400
1098 XH Amsterdam
Netherlands
Email: willem@nlnetlabs.nl
Fujiwara & Toorop Expires 3 September 2026 [Page 5]