



DNSOP                                                        D. Eastlake
Internet-Draft                                               Independent
Obsoletes: 6895 (if approved)                            9 December 2025
Updates: 1183, 2930, 3597, 8945 (if approved)                           
Intended status: Best Current Practice                                  
Expires: 12 June 2026


              Domain Name System (DNS) IANA Considerations
                draft-eastlake-dnsop-rfc6895bis-iana-02

Abstract

   This document specifies Internet Assigned Numbers Authority (IANA)
   parameter assignment considerations for the allocation of Domain Name
   System (DNS) resource record (RR) types, CLASSes, operation codes,
   error codes (RCODEs), DNS protocol message header bits, and AFSDB
   resource record subtypes.  It obsoletes RFC 6895 and updates RFCs
   1183, 2930, 3597, and 8945.

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 12 June 2026.

Copyright Notice

   Copyright (c) 2025 IETF Trust and the persons identified as the
   document authors.  All rights reserved.










Eastlake                  Expires 12 June 2026                  [Page 1]

Internet-Draft           DNS IANA Considerations           December 2025


   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
   2.  DNS Request/Response Headers  . . . . . . . . . . . . . . . .   3
     2.1.  OpCode Assignments  . . . . . . . . . . . . . . . . . . .   5
     2.2.  RCODE Assignment  . . . . . . . . . . . . . . . . . . . .   5
   3.  DNS Resource Records (RRs)  . . . . . . . . . . . . . . . . .   8
     3.1.  RRTYPE IANA Considerations  . . . . . . . . . . . . . . .   9
       3.1.1.  DNS RRTYPE Assignment Policy  . . . . . . . . . . . .  11
       3.1.2.  DNS RRTYPE Expert Guidelines  . . . . . . . . . . . .  13
       3.1.3.  Special Note on the OPT RR  . . . . . . . . . . . . .  13
       3.1.4.  The AFSDB RR Subtype Field  . . . . . . . . . . . . .  13
     3.2.  RR CLASS IANA Considerations  . . . . . . . . . . . . . .  14
     3.3.  Label Considerations  . . . . . . . . . . . . . . . . . .  16
       3.3.1.  Label Types . . . . . . . . . . . . . . . . . . . . .  16
       3.3.2.  Label Contents and Use  . . . . . . . . . . . . . . .  16
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  17
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  RRTYPE Assignment Template . . . . . . . . . . . . .  20
   Appendix B.  Changes from RFC6895 . . . . . . . . . . . . . . . .  22
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  22
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  22
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  23

1.  Introduction

   The Domain Name System (DNS) provides replicated distributed
   securable hierarchical databases that store "resource records" (RRs)
   under domain names.  DNS data is structured into CLASSes and zones
   that can be independently maintained.  Familiarity with [RFC1034],
   [RFC1035], [RFC2136], [RFC2181], [RFC4033], and DNS terminology
   [RFC9499] is assumed.

   This document provides, either directly or by reference, the general
   IANA parameter assignment considerations that apply across DNS
   request and response headers and all RRs.  There may be additional



Eastlake                  Expires 12 June 2026                  [Page 2]

Internet-Draft           DNS IANA Considerations           December 2025


   IANA considerations that apply to only a particular RRTYPE or
   request/response OpCode.  See the specific RFC defining that RRTYPE
   or request/response OpCode for such considerations if they have been
   defined, except for AFSDB RR considerations [RFC1183], which are
   included herein.  This document also covers IANA considerations for
   CLASSes, error codes (RCODEs), and DNS protocol message header bits.
   This RFC obsoletes [RFC6895] and updates RFCs [RFC1183], [RFC8945],
   [RFC2930], and [RFC3597].

   IANA currently maintains a web page of DNS parameters available from
   [IANADNS].

   "Standards Action", "IETF Review", "Specification Required",
   "Reserved", and "Private Use" are as defined in [RFC8126].

2.  DNS Request/Response Headers

   The header for DNS requests and responses contains field/bits as
   shown in the following diagrams taken from [RFC1035] and [RFC2136]:

                                            1  1  1  1  1  1
              0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                      ID                       |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |QR| OpCode!=5 |AA|TC|RD|RA| Z|AD|CD|   RCODE   |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    QDCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    ANCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    NSCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    ARCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

            Figure 1: DNS Message Header For Non-Update Messages














Eastlake                  Expires 12 June 2026                  [Page 3]

Internet-Draft           DNS IANA Considerations           December 2025


                                            1  1  1  1  1  1
              0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                      ID                       |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |QR| OpCode=5  |         Z          |   RCODE   |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    ZOCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    PRCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    UPCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    ARCOUNT                    |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

              Figure 2: DNS Message Header For Update Messages

   The ID field identifies the request and is echoed in the response so
   they can be matched.

   The QR (Query/Response) bit indicates whether the header is for a
   request (QR=0) or a response (QR=1).

   See Section 2.1 for the OpCode field.

   The AA (Authoritative Answer), TC (TrunCation), RD (Recursion
   Desired), RA (Recursion Available), and CD (Checking Disabled) bits
   are each specified as meaningful only in requests or only in
   responses, depending on the bit.  All except the CD bit are specified
   in [RFC1035] while the CD bit is specified in [RFC4035].  The AD bit
   was only meaningful in responses but is expected to have a separate
   but related meaning in queries (see Section 5.7 of [RFC6840]).  Only
   the RD and CD bits are expected to be copied from the request to the
   response; however, some DNS implementations copy all the request
   header as the initial value of the response header.  Thus, any
   attempt to use a "request" bit with a different meaning in a response
   or to define a request meaning for a "response" bit may be dangerous,
   given the existing implementation.  Meanings for these bits may only
   be assigned by a Standards Action.

   The unsigned integer fields query/request count (QDCOUNT), answer
   count (ANCOUNT), authority count (NSCOUNT), and additional
   information count (ARCOUNT) express the number of records in each
   section for all OpCodes except Update [RFC2136].  These fields have
   the same structure and data type for Update but are instead the
   counts for the zone (ZOCOUNT), prerequisite (PRCOUNT), update
   (UPCOUNT), and additional information (ARCOUNT) sections.



Eastlake                  Expires 12 June 2026                  [Page 4]

Internet-Draft           DNS IANA Considerations           December 2025


   The Z bits are sent as zero and ignored on receipt.

      |  There have been ancient DNS implementations for which the Z bit
      |  being on in a Query message meant that only a response from the
      |  primary server for a zone is acceptable.  It is believed that
      |  all current DNS implementations ignore this bit.

   Assigning a meaning to a Z bit requires a Standards Action.

2.1.  OpCode Assignments

   Currently, DNS OpCodes are assigned as follows:

         +========+==================================+===========+
         | OpCode | Name                             | Reference |
         +========+==================================+===========+
         | 0      | Query                            | [RFC1035] |
         +--------+----------------------------------+-----------+
         | 1      | IQuery (Inverse Query, OBSOLETE) | [RFC3425] |
         +--------+----------------------------------+-----------+
         | 2      | Status                           | [RFC1035] |
         +--------+----------------------------------+-----------+
         | 3      | Unassigned                       |           |
         +--------+----------------------------------+-----------+
         | 4      | Notify                           | [RFC1996] |
         +--------+----------------------------------+-----------+
         | 5      | Update                           | [RFC2136] |
         +--------+----------------------------------+-----------+
         | 6      | DSO (DNS Stateful Operations)    | [RFC8490] |
         +--------+----------------------------------+-----------+
         | 7-15   | Unassigned                       |           |
         +--------+----------------------------------+-----------+

                           Table 1: DNS Op Codes

   Although the Status OpCode is reserved in [RFC1035], its behavior has
   not been specified.  New OpCode assignments require a Standards
   Action with early allocation permitted as specified in [RFC7120].

2.2.  RCODE Assignment

   It would appear from the DNS header above that only four bits of
   RCODE, or response/error code, are available.  However, RCODEs can
   appear not only at the top level of a DNS response but also inside
   TSIG RRs [RFC8945], TKEY RRs [RFC2930], and extended by OPT RRs
   [RFC6891].  The OPT RR provides an 8-bit extension to the 4 header
   bits, resulting in a 12-bit RCODE field, and the TSIG and TKEY RRs
   have a separate 16-bit field designated in their RFCs as the "Error"



Eastlake                  Expires 12 June 2026                  [Page 5]

Internet-Draft           DNS IANA Considerations           December 2025


   field.

   Error codes appearing in the DNS header and in these other RR types
   all refer to the same error code space with the exception of error
   code 16, which has a different meaning in the OPT RR than in the TSIG
   RR, and error code 9, whose variations are described after the table
   below.  The duplicate assignment of 16 was accidental.  To the extent
   that any prior RFCs imply any sort of different error number space
   for the OPT, TSIG, or TKEY RRs, they are superseded by this unified
   DNS error number space.  (This paragraph is the reason this document
   updates [RFC8945] and [RFC2930].)  With the existing exceptions of
   error numbers 9 and 16, the same error number must not be assigned
   for different errors even if they would only occur in different RR
   types.  See table below.

       +========+===========+========================+============+
       | RCODE  | Name      | Description            | References |
       +========+===========+========================+============+
       | Decimal            |                                     |
       | Hexadecimal        |                                     |
       +--------+-----------+------------------------+------------+
       | 0      | NoError   | No Error               | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 1      | FormErr   | Format Error           | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 2      | ServFail  | Server Failure         | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 3      | NXDomain  | Non-Existent Domain    | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 4      | NotImp    | Not Implemented        | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 5      | Refused   | Request Refused        | [RFC1035]  |
       +--------+-----------+------------------------+------------+
       | 6      | YXDomain  | Name Exists when it    | [RFC2136]  |
       |        |           | should not             | [RFC6672]  |
       +--------+-----------+------------------------+------------+
       | 7      | YXRRSet   | RR Set Exists when it  | [RFC2136]  |
       |        |           | should not             |            |
       +--------+-----------+------------------------+------------+
       | 8      | NXRRSet   | RR Set that should     | [RFC2136]  |
       |        |           | exist does not         |            |
       +--------+-----------+------------------------+------------+
       | 9      | NotAuth   | Server Not             | [RFC2136]  |
       |        |           | Authoritative for zone |            |
       +--------+-----------+------------------------+------------+
       | 9      | NotAuth   | Not Authorized         | [RFC8945]  |
       +--------+-----------+------------------------+------------+
       | 10     | NotZone   | Name not contained in  | [RFC2136]  |



Eastlake                  Expires 12 June 2026                  [Page 6]

Internet-Draft           DNS IANA Considerations           December 2025


       |        |           | zone                   |            |
       +--------+-----------+------------------------+------------+
       | 11     | DSOTYPENI | DSO TYPE Not           | [RFC8490]  |
       |        |           | Implemented            |            |
       +--------+-----------+------------------------+------------+
       | 12-15              | Unassigned                          |
       | 0xB-0xF            |                                     |
       +--------+-----------+------------------------+------------+
       | 16     | BADVERS   | Bad OPT Version        | [RFC6891]  |
       +--------+-----------+------------------------+------------+
       | 16     | BADSIG    | TSIG Signature Failure | [RFC8945]  |
       +--------+-----------+------------------------+------------+
       | 17     | BADKEY    | Key not recognized     | [RFC8945]  |
       +--------+-----------+------------------------+------------+
       | 18     | BADTIME   | Signature out of time  | [RFC8945]  |
       |        |           | window                 |            |
       +--------+-----------+------------------------+------------+
       | 19     | BADMODE   | Bad TKEY Mode          | [RFC2930]  |
       +--------+-----------+------------------------+------------+
       | 20     | BADNAME   | Duplicate key name     | [RFC2930]  |
       +--------+-----------+------------------------+------------+
       | 21     | BADALG    | Algorithm not          | [RFC2930]  |
       |        |           | supported              |            |
       +--------+-----------+------------------------+------------+
       | 22     | BADTRUNC  | Bad Truncation         | [RFC8945]  |
       +--------+-----------+------------------------+------------+
       | 23     | BADCOOKE  | Bad/Missing Server     | [RFC7873]  |
       |        |           | Cookie                 |            |
       +--------+-----------+------------------------+------------+
       | 24-3,840           | Unassigned                          |
       | 0x0017-0x0F00      |                                     |
       +--------------------+-------------------------------------+
       | 3,841-4,095        | Private Use                         |
       | 0x0F01-0x0FFF      |                                     |
       +--------------------+-------------------------------------+
       | 4,096-65,534       | Unassigned                          |
       | 0x1000-0xFFFE      |                                     |
       +--------------------+-------------------------------------+
       | 65,535             | Reserved                            |
       | 0xFFFF             |                                     |
       +--------------------+-------------------------------------+

                         Table 2: DNS Error Codes

   |  Note on error number 9 (NotAuth): This error number means either
   |  "Not Authoritative" [RFC2136] or "Not Authorized" [RFC8945].  If 9
   |  appears as the RCODE in the header of a DNS response without a
   |  TSIG RR or with a TSIG RR having a zero error field, then it means



Eastlake                  Expires 12 June 2026                  [Page 7]

Internet-Draft           DNS IANA Considerations           December 2025


   |  "Not Authoritative".  If 9 appears as the RCODE in the header of a
   |  DNS response that includes a TSIG RR with a non-zero error field,
   |  then it means "Not Authorized".

   Since it is important that RCODEs be understood for interoperability,
   assignment of a new RCODE in the ranges listed above as "Unassigned"
   requires IETF Review.

3.  DNS Resource Records (RRs)

   All RRs have the same top-level format, shown in the figure below
   taken from [RFC1035].

                                             1  1  1  1  1  1
               0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                                               |
             /                                               /
             /                      NAME                     /
             /                                               /
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                      TYPE                     |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                     CLASS                     |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                      TTL                      |
             |                                               |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
             |                    RDLENGTH                   |
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
             /                     RDATA                     /
             /                                               /
             +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

                 Figure 3: DNS Resource Record (RR) Format

   NAME:  An owner name, i.e., the name of the node to which this RR
      pertains.  NAMEs are specific to a CLASS as described in
      Section 3.2.  NAMEs consist of an ordered sequence of one or more
      labels, each of which has a label type [RFC1035] [RFC6891].

   TYPE:  A 2-octet unsigned integer containing one of the RRTYPE codes.
      See Section 3.1.

   CLASS:  A 2-octet unsigned integer containing one of the RR CLASS
      codes.  See Section 3.2.

   TTL:  A 4-octet (32-bit) unsigned integer that specifies, for data



Eastlake                  Expires 12 June 2026                  [Page 8]

Internet-Draft           DNS IANA Considerations           December 2025


      TYPEs, the number of seconds that the resource record may be
      cached before the source of the information should again be
      consulted.  Zero is interpreted to mean that the RR can only be
      used for the transaction in progress.

   RDLENGTH:  An unsigned 16-bit integer that specifies the length in
      octets of the RDATA field.

   RDATA:  A variable-length string of octets that constitutes the
      resource.  The format of this information varies according to the
      TYPE and, in some cases, the CLASS of the resource record.

3.1.  RRTYPE IANA Considerations

   There are three subcategories of RRTYPE numbers: data TYPEs, QTYPEs,
   and Meta-TYPEs.

   Data TYPEs:  The means of storing data.  These are the RRs that are
      stored in zones.

   QTYPEs:  These can only be used in queries or other requests.  They
      are not stored in zones.

   Meta-TYPEs:  These designate transient data associated with a
      particular DNS message and, in some cases, can also be used in
      requests.  They are not stored in zones.  However, the special
      case of RRTYPE 128 can only validly "appear" as the corresponding
      bit in an NSEC type bit map [RFC4034].

   Thus far, data TYPEs have been assigned from the ranges 1 - 127 and
   256 - 61,439, while Q and Meta-TYPEs have been assigned from 255
   downward except for the OPT Meta-RR, which is assigned TYPE 41.
   There is also a range of TYPES from 129 to 144 reserved for Private
   Use Q or Meta-RRs.  There have been DNS implementations that made
   caching decisions based on the top bit of the bottom byte of the
   RRTYPE.

   There are currently four Meta-TYPEs and five QTYPEs assigned and a
   range of TYPES assigned for Private Use as listed in the table below.












Eastlake                  Expires 12 June 2026                  [Page 9]

Internet-Draft           DNS IANA Considerations           December 2025


    +=======+==========+=================================+===========+
    | Value | Mnemonic | Description                     | Reference |
    +=======+==========+=================================+===========+
    | 41    | OPT      | Meta-TYPE: Extension Mechanisms | [RFC6891] |
    +-------+----------+---------------------------------+-----------+
    | 128   | NXNAME   | Meta-TYPE: Compact Denial of    | [RFC9824] |
    |       |          | Existence NXDOMAIN indicator    |           |
    +-------+----------+---------------------------------+-----------+
    | 129-144          | Private Use Q or Meta-TYPEs     | [this     |
    |                  |                                 | document] |
    +-------+----------+---------------------------------+-----------+
    | 249   | TKEY     | Meta-TYPE: Transaction Key      | [RFC2930] |
    +-------+----------+---------------------------------+-----------+
    | 250   | TSIG     | Meta-TYPE: Transaction          | [RFC8945] |
    |       |          | Signature                       |           |
    +-------+----------+---------------------------------+-----------+
    | 251   | IXFR     | QTYPE: Incremental Zone         | [RFC1995] |
    |       |          | Transfer                        |           |
    +-------+----------+---------------------------------+-----------+
    | 252   | AXFR     | QTYPE: Entire Zone Transfer     | [RFC1035] |
    |       |          |                                 | [RFC5936] |
    +-------+----------+---------------------------------+-----------+
    | 253   | MAILB    | QTYPE: Mailbox-related RRs      | [RFC1035] |
    +-------+----------+---------------------------------+-----------+
    | 254   | MAILA    | QTYPE: Mail agent RRs (Obsolete | [RFC1035] |
    |       |          | - see the MX RR)                |           |
    +-------+----------+---------------------------------+-----------+
    | 255   | *        | QTYPE: ANY/ALL                  | [RFC1035] |
    |       |          |                                 | [RFC8482] |
    +-------+----------+---------------------------------+-----------+

           Table 3: Currently Assigned QTYPE and Meta-TYPE RRs

   Assigned RRTYPEs have mnemonics that must be completely disjoint from
   the mnemonics used for CLASSes and that must match the regular
   expression below.  In addition, the generic CLASS and RRTYPE names
   specified in Section 5 of [RFC3597] cannot be assigned as RRTYPE
   mnemonics.

                         [A-Z][A-Z0-9\-]*[A-Z0-9]
                                 but not
                            (TYPE|CLASS)[0-9]*

   Considerations for the assignment of new RRTYPEs are as follows:







Eastlake                  Expires 12 June 2026                 [Page 10]

Internet-Draft           DNS IANA Considerations           December 2025


   +===============+===================================================+
   | Decimal       | Assignment Policy                                 |
   | Hexadecimal   |                                                   |
   +===============+===================================================+
   | 0             | RRTYPE zero is used as a special                  |
   | 0x0000        | indicator for the SIG(0) RR [RFC2931]             |
   |               | [RFC4034] and in other circumstances.  It         |
   |               | must never be assigned for ordinary use.          |
   +---------------+---------------------------------------------------+
   | 1-127         | Unassigned RRTYPEs in this range are              |
   | 0x0001-0x007F | assigned for data TYPEs by the DNS RRTYPE         |
   |               | Assignment Policy as specified in                 |
   |               | Section 3.1.1.                                    |
   +---------------+---------------------------------------------------+
   | 128-255       | Unassigned RRTYPEs in this range are              |
   | 0x0080-0x00FF | assigned for QTYPEs and Meta-TYPEs by the         |
   |               | DNS RRTYPE Assignment Policy as specified         |
   |               | in Section 3.1.1.                                 |
   +---------------+---------------------------------------------------+
   | 256-61,439    | Unassigned RRTYPEs in this range are              |
   | 0x0100-0xEFFF | assigned for data RRTYPEs by the DNS              |
   |               | RRTYPE Assignment Policy as specified in          |
   |               | Section 3.1.1.  (32,768 and 32,769                |
   |               | (0x8000 and 0x8001) have been assigned.)          |
   +---------------+---------------------------------------------------+
   | 61,440-65,279 | Reserved for future use.  IETF Review             |
   | 0xF000-0xFEFF | required to define use                            |
   +---------------+---------------------------------------------------+
   | 65,280-65,534 | Reserved for Private Use data RRs.                |
   | 0xFF00-0xFFFE |                                                   |
   +---------------+---------------------------------------------------+
   | 65,535        | Reserved (Standards Action)                       |
   | 0xFFFF        |                                                   |
   +---------------+---------------------------------------------------+

                  Table 4: DNS Resource Record Type Codes

3.1.1.  DNS RRTYPE Assignment Policy

   Parameter values specified in Section 3.1 above, as assigned based on
   DNS RRTYPE Assignment Policy, are allocated by Expert Review if they
   meet the two requirements listed below.  There will be a pool of a
   small number of Experts appointed by the IESG.  Each application will
   be judged by an Expert selected by IANA.  In any case where the
   selected Expert is unavailable or states they have a conflict of
   interest, IANA may select another Expert from the pool.  Some
   guidelines for the Experts are given in Section 3.1.2.




Eastlake                  Expires 12 June 2026                 [Page 11]

Internet-Draft           DNS IANA Considerations           December 2025


   RRTYPEs that do not meet the requirements below may nonetheless be
   assignment by a Standards Action with early allocation permitted as
   specified in [RFC7120].

   1.  A complete template as specified in Appendix A has been posted to
       the dns-rrtype-applications@ietf.org mailing list and received by
       the Expert.

       Note that the posting of partially completed, draft, or formally
       submitted templates to dnsop@ietf.org by the applicant or Expert
       for comment and discussion is highly encouraged.  Before formal
       submission of an RRTYPE template, we recommend submitting it for
       community review and considering the responses in order to reduce
       the probability of initial rejection and the need for
       modification and resubmission.

   2.  The RR for which an RRTYPE code is being requested is either (a)
       a data TYPE that can be handled as an Unknown RR as described in
       [RFC3597] or (b) a Meta-TYPE whose processing is optional, i.e.,
       it is safe to simply discard RRs with that Meta-TYPE in queries
       or responses.

       Note that such RRs may include additional section processing,
       provided such processing is optional.

   After the applicant submits their formal application to IANA by
   sending the completed template specified in Appendix A to the dns-
   rrtype-applications@ietf.org mailing list, IANA appoints an Expert
   and sends the completed template to the Expert, copying the
   applicant.  No more than two weeks after receiving the application,
   the Expert shall explicitly approve or reject the application,
   informing IANA, the applicant, and the dnsop@ietf.org mailing list.
   A rejection should include the reason for rejection and may include
   suggestions for improvement.  The Expert should consult with other
   technical experts and the dnsop@ietf.org mailing list as necessary.
   If the Expert does not approve the application within this period, it
   is considered rejected.  IANA should report non-responsive Experts to
   the IESG.

   IANA shall maintain a public archive of approved templates.  In
   addition, if the required description of the RRTYPE applied for is
   referenced by URL, a copy of the document so referenced should be
   included in the archive.








Eastlake                  Expires 12 June 2026                 [Page 12]

Internet-Draft           DNS IANA Considerations           December 2025


3.1.2.  DNS RRTYPE Expert Guidelines

   The Designated Expert should normally be lenient, preferring to
   approve most requests.  However, the Expert should usually reject any
   RRTYPE assignment request that meets one or more of the following
   criteria:

   1.  The request was documented in a manner that was not sufficiently
       clear or complete to evaluate or implement.  (Additional
       documentation can be provided during the Expert Review period.)

   2.  The proposed RRTYPE or RRTYPEs affect DNS processing and do not
       meet the criteria in point 2 of Section 3.1.1 above.

   3.  Application use as documented makes incorrect assumptions about
       DNS protocol behavior, such as wildcards, CNAME, DNAME, etc.

   4.  An excessive number of RRTYPE values is being requested when the
       purpose could be met with a smaller number of values or with
       Private Use values.

3.1.3.  Special Note on the OPT RR

   The OPT (OPTion) RR (RRTYPE 41) and its IANA considerations are
   specified in [RFC6891].  Its primary purpose is to extend the
   effective field size of various DNS fields, including RCODE, label
   type, OpCode, flag bits, and RDATA size.  In particular, for
   resolvers and servers that recognize it, it extends the RCODE field
   from 4 to 12 bits.

3.1.4.  The AFSDB RR Subtype Field

   The AFSDB RR [RFC1183] is a CLASS-insensitive RR that has the same
   RDATA field structure as the MX RR [RFC1035], but the 16-bit unsigned
   integer field at the beginning of the RDATA is interpreted as a
   subtype as shown below.  Use of the AFSDB RR to locate AFS cell
   database servers was deprecated by [RFC5864].  This subtype registry
   is closed, and assignment of new subtypes is not permitted.













Eastlake                  Expires 12 June 2026                 [Page 13]

Internet-Draft           DNS IANA Considerations           December 2025


               +===============+==========================+
               | Decimal       | Assignment Policy        |
               | Hexadecimal   |                          |
               +===============+==========================+
               | 0             | Reserved; registry       |
               | 0x0000        | closed                   |
               +---------------+--------------------------+
               | 1             | AFS v3.0 Location        |
               | 0x0001        | Service [RFC1183]        |
               +---------------+--------------------------+
               | 2             | DCE/NCA root cell        |
               | 0x0002        | directory node [RFC1183] |
               +---------------+--------------------------+
               | 3-65,279      | Not assigned; registry   |
               | 0x0003-0xFEFF | closed                   |
               +---------------+--------------------------+
               | 65,280-65,534 | Private Use              |
               | 0xFF00-0xFFFE |                          |
               +---------------+--------------------------+
               | 65,535        | Reserved; registry       |
               | 0xFFFF        | closed                   |
               +---------------+--------------------------+

                       Table 5: AFSDB Subtype Codes

3.2.  RR CLASS IANA Considerations

   There are currently two subcategories of DNS CLASSes: normal, data-
   containing classes; and QCLASSes that are only meaningful in queries
   or updates.

   DNS CLASSes have been little used but constitute another dimension of
   the DNS distributed database.  In particular, there is no necessary
   relationship between the namespace or root servers for one data CLASS
   and those for another data CLASS.  The same DNS NAME can have
   completely different meanings in different CLASSes.  The label types
   are the same, and the null label is usable only as root in every
   CLASS.  As global networking and DNS have evolved, the IN, or
   Internet, CLASS has dominated DNS use.

   As yet, there has not been a requirement for "Meta-CLASSes".  That
   would be a CLASS to designate transient data associated with a
   particular DNS message, which might be usable in queries.  However,
   it is possible that there might be a future requirement for one or
   more "Meta-CLASSes".






Eastlake                  Expires 12 June 2026                 [Page 14]

Internet-Draft           DNS IANA Considerations           December 2025


   Assigned CLASSes have mnemonics that must be completely disjoint from
   the mnemonics used for RRTYPEs and that must match the regular
   expression below.  In addition, the generic CLASS and RRTYPE names
   specified in Section 5 of [RFC3597] cannot be assigned as new CLASS
   mnemonics.

                         [A-Z][A-Z0-9\-]*[A-Z0-9]
                                 but not
                            (CLASS|TYPE)[0-9]*

   The current CLASS assignments and considerations for future
   assignments are as follows:

      +===============+============================================+
      | Decimal       | Assignment Policy                          |
      | Hexadecimal   |                                            |
      +===============+============================================+
      | 0             | Reserved; assignment requires a Standards  |
      | 0x0000        | Action.                                    |
      +---------------+--------------------------------------------+
      | 1             | Internet (IN) [RFC1035]                    |
      | 0x0001        |                                            |
      +---------------+--------------------------------------------+
      | 2             | Available for assignment by IETF Review as |
      | 0x0002        | a data CLASS.                              |
      +---------------+--------------------------------------------+
      | 3             | Chaos (CH) [Moon1981]                      |
      | 0x0003        |                                            |
      +---------------+--------------------------------------------+
      | 4             | Hesiod (HS) [Dyer1987]                     |
      | 0x0004        |                                            |
      +---------------+--------------------------------------------+
      | 5-127         | Available for assignment by IETF Review    |
      | 0x0005-0x007F | for data CLASSes only.                     |
      +---------------+--------------------------------------------+
      | 128-253       | Available for assignment by IETF Review    |
      | 0x0080-0x00FD | for QCLASSes and Meta-CLASSes only.        |
      +---------------+--------------------------------------------+
      | 254           | QCLASS NONE [RFC2136]                      |
      | 0x00FE        |                                            |
      +---------------+--------------------------------------------+
      | 255           | QCLASS * (ANY) [RFC1035]                   |
      | 0x00FF        |                                            |
      +---------------+--------------------------------------------+
      | 256-32,767    | Available for assignment by IETF Review.   |
      | 0x0100-0x7FFF |                                            |
      +---------------+--------------------------------------------+
      | 32,768-57,343 | Available for assignment to data CLASSes   |



Eastlake                  Expires 12 June 2026                 [Page 15]

Internet-Draft           DNS IANA Considerations           December 2025


      | 0x8000-0xDFFF | only; Specification Required.              |
      +---------------+--------------------------------------------+
      | 57,344-65,279 | Available for assignment to QCLASSes and   |
      | 0xE000-0xFEFF | Meta-CLASSes only; Specification Required. |
      +---------------+--------------------------------------------+
      | 65,280-65,534 | Private Use                                |
      | 0xFF00-0xFFFE |                                            |
      +---------------+--------------------------------------------+
      | 65,535        | Reserved; can only be assigned by a        |
      | 0xFFFF        | Standards Action.                          |
      +---------------+--------------------------------------------+

                         Table 6: DNs CLASS Codes

3.3.  Label Considerations

   DNS NAMEs are sequences of labels [RFC1035].

3.3.1.  Label Types

   At the present time, there are two categories of label types: data
   labels and compression labels.  Compression labels are pointers to
   data labels elsewhere within an RR or DNS message and are intended to
   shorten the wire encoding of NAMEs.

   The two existing data label types are sometimes referred to as Text
   and Binary.  Text labels can, in fact, include any octet value
   including zero-value octets, but many current uses involve only
   printing ASCII characters [RFC0020].  For retrieval, Text labels are
   defined to treat ASCII uppercase and lowercase letter codes as
   matching [RFC4343].  Binary labels were bit sequences; they have been
   declared Historic [RFC6891].

3.3.2.  Label Contents and Use

   The last label in each NAME is "ROOT", which is the zero-length
   label.  By definition, the null or ROOT label cannot be used for any
   other NAME purpose.

   NAMEs are local to a CLASS.  The Hesiod [Dyer1987] and Chaos
   [Moon1981] CLASSes are for essentially local use.  The IN, or
   Internet, CLASS is thus the only DNS CLASS in global use on the
   Internet at this time.

   A somewhat out-of-date description of name assignment in the IN CLASS
   is given in [RFC1591].  Some information on reserved top-level domain
   names is in BCP 32 [RFC2606].




Eastlake                  Expires 12 June 2026                 [Page 16]

Internet-Draft           DNS IANA Considerations           December 2025


4.  Security Considerations

   This document addresses IANA considerations in the assignment of
   general DNS parameters, not security.  See [RFC4033], [RFC4034], and
   [RFC4035] for secure DNS considerations.

5.  IANA Considerations

   This document consists of DNS IANA considerations.

   IANA has established a process for accepting Appendix A templates and
   selecting an Expert from those appointed to review such template form
   applications.  IANA forwards the template to the Expert, copying the
   applicant.  IANA archives and makes available all approved RRTYPE
   assignment templates and referred documentation (unless it is readily
   available at a stable URI).  It is the duty of the applicant to post
   the formal application template to the dns-rrtype-
   applications@ietf.org mailing list, which IANA will monitor.  The
   dnsop@ietf.org mailing list is for community discussion and comment.
   See Section 3.1 and Appendix A for more details.

   IANA is requested to replace all occurrences of [RFC6895] as a
   reference in IANA registries are updated to refer to [this document].

6.  References

6.1.  Normative References

   [RFC0020]  Cerf, V., "ASCII format for network interchange", STD 80,
              RFC 20, DOI 10.17487/RFC0020, October 1969,
              <https://www.rfc-editor.org/info/rfc20>.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
              <https://www.rfc-editor.org/info/rfc1034>.

   [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>.

   [RFC1995]  Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
              DOI 10.17487/RFC1995, August 1996,
              <https://www.rfc-editor.org/info/rfc1995>.

   [RFC1996]  Vixie, P., "A Mechanism for Prompt Notification of Zone
              Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
              August 1996, <https://www.rfc-editor.org/info/rfc1996>.




Eastlake                  Expires 12 June 2026                 [Page 17]

Internet-Draft           DNS IANA Considerations           December 2025


   [RFC2136]  Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, DOI 10.17487/RFC2136, April 1997,
              <https://www.rfc-editor.org/info/rfc2136>.

   [RFC2181]  Elz, R. and R. Bush, "Clarifications to the DNS
              Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
              <https://www.rfc-editor.org/info/rfc2181>.

   [RFC2930]  Eastlake 3rd, D., "Secret Key Establishment for DNS (TKEY
              RR)", RFC 2930, DOI 10.17487/RFC2930, September 2000,
              <https://www.rfc-editor.org/info/rfc2930>.

   [RFC3425]  Lawrence, D., "Obsoleting IQUERY", RFC 3425,
              DOI 10.17487/RFC3425, November 2002,
              <https://www.rfc-editor.org/info/rfc3425>.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, DOI 10.17487/RFC3597, September
              2003, <https://www.rfc-editor.org/info/rfc3597>.

   [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/info/rfc4033>.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, DOI 10.17487/RFC4034, March 2005,
              <https://www.rfc-editor.org/info/rfc4034>.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
              <https://www.rfc-editor.org/info/rfc4035>.

   [RFC5936]  Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
              (AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
              <https://www.rfc-editor.org/info/rfc5936>.

   [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>.

   [RFC6840]  Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
              Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
              DOI 10.17487/RFC6840, February 2013,
              <https://www.rfc-editor.org/info/rfc6840>.



Eastlake                  Expires 12 June 2026                 [Page 18]

Internet-Draft           DNS IANA Considerations           December 2025


   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891,
              DOI 10.17487/RFC6891, April 2013,
              <https://www.rfc-editor.org/info/rfc6891>.

   [RFC7120]  Cotton, M., "Early IANA Allocation of Standards Track Code
              Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
              2014, <https://www.rfc-editor.org/info/rfc7120>.

   [RFC7873]  Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
              Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
              <https://www.rfc-editor.org/info/rfc7873>.

   [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>.

   [RFC8482]  Abley, J., Gudmundsson, O., Majkowski, M., and E. Hunt,
              "Providing Minimal-Sized Responses to DNS Queries That
              Have QTYPE=ANY", RFC 8482, DOI 10.17487/RFC8482, January
              2019, <https://www.rfc-editor.org/info/rfc8482>.

   [RFC8490]  Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
              Lemon, T., and T. Pusateri, "DNS Stateful Operations",
              RFC 8490, DOI 10.17487/RFC8490, March 2019,
              <https://www.rfc-editor.org/info/rfc8490>.

   [RFC8945]  Dupont, F., Morris, S., Vixie, P., Eastlake 3rd, D.,
              Gudmundsson, O., and B. Wellington, "Secret Key
              Transaction Authentication for DNS (TSIG)", STD 93,
              RFC 8945, DOI 10.17487/RFC8945, November 2020,
              <https://www.rfc-editor.org/info/rfc8945>.

   [RFC9824]  Huque, S., Elmerot, C., and O. Gudmundsson, "Compact
              Denial of Existence in DNSSEC", RFC 9824,
              DOI 10.17487/RFC9824, September 2025,
              <https://www.rfc-editor.org/info/rfc9824>.

6.2.  Informative References

   [Dyer1987] Dyer, S. and F. Hsu, "Hesiod", Project Athena Technical
              Plan Name Service, April 1987.

   [IANADNS]  IANA, "DNS Parameters", <https://www.iana.org/assignments/
              dns-parameters/dns-parameters.xhtml>.





Eastlake                  Expires 12 June 2026                 [Page 19]

Internet-Draft           DNS IANA Considerations           December 2025


   [Moon1981] Moon, D., "Chaosnet", Massachusetts Institute of
              Technology, Artificial Intelligence Laboratory, A. I.
              Memo 628, June 1981.

   [RFC1183]  Everhart, C., Mamakos, L., Ullmann, R., and P.
              Mockapetris, Ed., "New DNS RR Definitions", RFC 1183,
              DOI 10.17487/RFC1183, October 1990,
              <https://www.rfc-editor.org/info/rfc1183>.

   [RFC1591]  Postel, J., "Domain Name System Structure and Delegation",
              RFC 1591, DOI 10.17487/RFC1591, March 1994,
              <https://www.rfc-editor.org/info/rfc1591>.

   [RFC2606]  Eastlake 3rd, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, DOI 10.17487/RFC2606, June 1999,
              <https://www.rfc-editor.org/info/rfc2606>.

   [RFC2931]  Eastlake 3rd, D., "DNS Request and Transaction Signatures
              ( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
              2000, <https://www.rfc-editor.org/info/rfc2931>.

   [RFC4343]  Eastlake 3rd, D., "Domain Name System (DNS) Case
              Insensitivity Clarification", RFC 4343,
              DOI 10.17487/RFC4343, January 2006,
              <https://www.rfc-editor.org/info/rfc4343>.

   [RFC5864]  Allbery, R., "DNS SRV Resource Records for AFS", RFC 5864,
              DOI 10.17487/RFC5864, April 2010,
              <https://www.rfc-editor.org/info/rfc5864>.

   [RFC6895]  Eastlake 3rd, D., "Domain Name System (DNS) IANA
              Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
              April 2013, <https://www.rfc-editor.org/info/rfc6895>.

   [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>.

Appendix A.  RRTYPE Assignment Template












Eastlake                  Expires 12 June 2026                 [Page 20]

Internet-Draft           DNS IANA Considerations           December 2025


                 DNS RRTYPE PARAMETER ASSIGNMENT TEMPLATE

   When ready for formal consideration, this template is to be submitted
   to IANA for processing by emailing the template to dns-rrtype-
   applications@ietf.org.

   A. Submission Date:

   B.1 Submission Type:  [ ] New RRTYPE  [ ] Modification to RRTYPE
   B.2 Kind of RR:  [ ] Data RR  [ ] Meta-RR

   C. Contact Information for submitter (will be publicly posted):
      Name:                            Email Address:
      International telephone number:
      Other contact handles:

   D. Motivation for the new RRTYPE application.
      Please keep this part at a high level to inform the Expert and
      reviewers about uses of the RRTYPE.  Most reviewers will be DNS
      experts that may have limited knowledge of your application space.

   E. Description of the proposed RR type.
      This description can be provided in-line in the template, as an
      attachment, or with a publicly available URL.

   F. What existing RRTYPE or RRTYPEs come closest to filling that need
      and why are they unsatisfactory?

   G. What mnemonic is requested for the new RRTYPE (optional)?

      Note: If a mnemonic is not supplied, not allowed, or duplicates an
      existing RRTYPE or CLASS mnemonic, the Expert will assign a
      mnemonic.

   H. Does the requested RRTYPE make use of any existing IANA registry
      or require the creation of a new IANA subregistry in DNS
      Parameters?  If so, please indicate which registry is to be used
      or created.  If a new subregistry is needed, specify the
      assignment policy for it and its initial contents.  Also include
      what the modification procedures will be.

   I. Does the proposal require/expect any changes in DNS
      servers/resolvers that prevent the new type from being processed
      as an unknown RRTYPE (see RFC 3597)?

   J. Comments:





Eastlake                  Expires 12 June 2026                 [Page 21]

Internet-Draft           DNS IANA Considerations           December 2025


Appendix B.  Changes from [RFC6895]

   1.   Reserve RR types 129-144 for Private Use Q and Meta-Types as
        contributed by Shumon Huque.  Add a Table of Q and Meta-Types.

   2.   Update references to dnsext@ietf.org to dnsop@ietf.org.

   3.   Drop list of updates from RFC 6195 as those were already
        incorporated into [RFC6895].  Add this list of changes from
        [RFC6895].

   4.   Convert source to XMLv3.

   5.   Update numerous references to point to the latest RFCs.

   6.   Update Introduction to list all RFC Updates and to cover all
        topics covered in the Abstract and to not have a subsection.

   7.   Add reference to DNS Terminology [RFC9499].

   8.   Generally, replace most uses of "query" to be "request".

   9.   Add captions to all Figures and Tables.

   10.  Update DNS Op Codes Table and DNS Error Codes Table to list
        additional values assigned.

   11.  Numerous editorial changes.

Acknowledgements

   TBD

   [RFC6895] acknowledgements: Alfred Hoenes' contributions are
   gratefully acknowledged as are those by Mark Andrews, Dick Franks,
   and Michael Sheldon.

   Yet earlier versions acknowledgements: Eric Brunner-Williams and Bill
   Manning.

Contributors

   Shumon Huque
   Salesforce
   Email: shuque@gmail.com






Eastlake                  Expires 12 June 2026                 [Page 22]

Internet-Draft           DNS IANA Considerations           December 2025


Author's Address

   Donald Eastlake
   Independent
   2386 Panoramic Circle
   Apopka, FL 32703
   United States of America
   Phone: +1-508-333-2270
   Email: d3e3e3@gmail.com










































Eastlake                  Expires 12 June 2026                 [Page 23]
