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DNS Catalog Zones

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 9432.
Authors Peter van Dijk , Libor Peltan , Ondřej Surý , Willem Toorop , Kees Monshouwer , Peter Thomassen , Aram Sargsyan
Last updated 2022-10-30 (Latest revision 2022-10-19)
Replaces draft-toorop-dnsop-dns-catalog-zones
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Tim Wicinski
Shepherd write-up Show Last changed 2022-10-13
IESG IESG state Became RFC 9432 (Proposed Standard)
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Warren "Ace" Kumari
Send notices to
DNSOP Working Group                                          P. van Dijk
Internet-Draft                                                  PowerDNS
Intended status: Standards Track                               L. Peltan
Expires: 22 April 2023                                            CZ.NIC
                                                                 O. Sury
                                             Internet Systems Consortium
                                                               W. Toorop
                                                              NLnet Labs
                                                           K. Monshouwer
                                                            P. Thomassen
                                 deSEC, SSE - Secure Systems Engineering
                                                             A. Sargsyan
                                             Internet Systems Consortium
                                                         19 October 2022

                           DNS Catalog Zones


   This document describes a method for automatic DNS zone provisioning
   among DNS primary and secondary nameservers by storing and
   transferring the catalog of zones to be provisioned as one or more
   regular DNS zones.

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

   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 22 April 2023.

Copyright Notice

   Copyright (c) 2022 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 (
   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Description . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Catalog Zone Structure  . . . . . . . . . . . . . . . . . . .   4
     4.1.  SOA and NS Records  . . . . . . . . . . . . . . . . . . .   4
     4.2.  Member Zones  . . . . . . . . . . . . . . . . . . . . . .   4
     4.3.  Properties  . . . . . . . . . . . . . . . . . . . . . . .   5
       4.3.1.  Schema Version (version property) . . . . . . . . . .   6
     4.4.  Member Zone Properties  . . . . . . . . . . . . . . . . .   6
       4.4.1.  Change of Ownership (coo property)  . . . . . . . . .   7
       4.4.2.  Groups (group property) . . . . . . . . . . . . . . .   7
     4.5.  Custom Properties (*.ext properties)  . . . . . . . . . .   8
   5.  Nameserver Behavior . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  General Requirements  . . . . . . . . . . . . . . . . . .   9
     5.2.  Member zone name clash  . . . . . . . . . . . . . . . . .  10
     5.3.  Member zone removal . . . . . . . . . . . . . . . . . . .  10
     5.4.  Member node name change . . . . . . . . . . . . . . . . .  11
     5.5.  Migrating member zones between catalogs . . . . . . . . .  11
     5.6.  Zone-associated state reset . . . . . . . . . . . . . . .  11
   6.  Implementation and operational Notes  . . . . . . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  14
   10. Informative References  . . . . . . . . . . . . . . . . . . .  15
   Appendix A.  Implementation Status  . . . . . . . . . . . . . . .  15
   Appendix B.  Change History . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The content of a DNS zone is synchronized amongst its primary and
   secondary nameservers using AXFR and IXFR.  However, the list of
   zones served by the primary (called a catalog in [RFC1035]) is not
   automatically synchronized with the secondaries.  To add or remove a
   zone, the administrator of a DNS nameserver farm not only has to add
   or remove the zone from the primary, they must also add/remove the
   zone from all secondaries, either manually or via an external

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   application.  This can be both inconvenient and error-prone; it is
   also dependent on the nameserver implementation.

   This document describes a method in which the catalog is represented
   as a regular DNS zone (called a "catalog zone" here), and transferred
   using DNS zone transfers.  As zones are added to or removed from the
   catalog zone, these changes are distributed to the secondary
   nameservers in the normal way.  The secondary nameservers then
   add/remove/modify the zones they serve in accordance with the changes
   to the catalog zone.  Other use-cases of nameserver remote
   configuration by catalog zones are possible, where the catalog
   consumer might not be a secondary.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

   Catalog zone  A DNS zone containing a DNS catalog, that is, a list of
      DNS zones and associated properties.

   Member zone  A DNS zone whose configuration is published inside a
      catalog zone.

   Member node  A DNS name in the Catalog zone representing a Member

   $CATZ  Used in examples as a placeholder to represent the domain name
      of the catalog zone itself. $OLDCATZ and $NEWCATZ are used to
      discuss migration of a member zone from one catalog zone $OLDCATZ
      to another catalog zone $NEWCATZ.

   Catalog producer  An entity that generates and is responsible for the
      contents of the catalog zone.

   Catalog consumer  An entity that extracts information from the
      catalog zone (such as a DNS server that configures itself
      according to the catalog zone's contents).

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3.  Description

   A catalog zone is a DNS zone whose contents are specially crafted.
   Its records primarily constitute a list of PTR records referencing
   other DNS zones (so-called "member zones").  The catalog zone may
   contain other records indicating additional metadata (so-called
   "properties") associated with these member zones.

   Catalog consumers MUST ignore any RR in the catalog zone which is
   meaningless or useless to the implementation.

   Authoritative servers may be pre-configured with multiple catalog
   zones, each associated with a different set of configurations.

   Although the contents of a catalog zone are interpreted and acted
   upon by nameservers, a catalog zone is a regular DNS zone and so must
   adhere to the standards for such zones.

   A catalog zone is primarily intended for the management of a farm of
   authoritative nameservers.  The content of catalog zones may not be
   accessible from any recursive nameserver.

4.  Catalog Zone Structure

4.1.  SOA and NS Records

   As with any other DNS zone, a catalog zone MUST have a SOA record and
   at least one NS record at its apex.

   The SOA record's SERIAL, REFRESH, RETRY and EXPIRE fields [RFC1035]
   are used during zone transfer.  A catalog zone's SOA SERIAL field
   MUST increase when an update is made to the catalog zone's contents
   as per serial number arithmetic defined in [RFC1982].  Otherwise,
   catalog consumers might not notice updates to the catalog zone's

   There is no requirement to be able to query the catalog zone via
   recursive nameservers.  However, at least one NS RR is still required
   so that catalog zone is a syntactically correct DNS zone.  A single
   NS RR with a NSDNAME field containing the absolute name "invalid." is
   RECOMMENDED [RFC2606][RFC6761].

4.2.  Member Zones

   The list of member zones is specified as a collection of member
   nodes, represented by domain names under the owner name "zones" where
   "zones" is a direct child domain of the catalog zone.

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   The names of member zones are represented on the RDATA side (instead
   of as a part of owner names) of a PTR record, so that all valid
   domain names may be represented regardless of their length [RFC1035].
   This PTR record MUST be the only record in the PTR RRset with the
   same name.  More than one record in the RRset denotes a broken
   catalog zone which MUST NOT be processed (see Section 5.1).

   For example, if a catalog zone lists three zones "",
   "" and "", the member node RRs would appear
   as follows:

   <unique-1>.zones.$CATZ 0 IN PTR
   <unique-2>.zones.$CATZ 0 IN PTR
   <unique-3>.zones.$CATZ 0 IN PTR

   where <unique-N> is a label that tags each record in the collection.
   <unique-N> has an unique value in the collection.  When different
   <unique-N> labels hold the same PTR value (i.e. point to the same
   member zone), the catalog zone is broken and MUST NOT be processed
   (see Section 5.1).

   Member node labels carry no informational meaning beyond labeling
   member zones.  A changed label may indicate that the state for a zone
   needs to be reset (see Section 5.6).

   Having the zones uniquely tagged with the <unique-N> label ensures
   that additional RRs can be added below the member node (see
   Section 4.3).

   The CLASS field of every RR in a catalog zone MUST be IN (1).

   The TTL field's value is not defined by this memo.  Catalog zones are
   for authoritative nameserver management only and are not intended for
   general querying via recursive resolvers.

4.3.  Properties

   Catalog zone information is stored in the form of "properties".

   Properties are identified by their name, which is used as an owner
   name prefix for one or more record sets underneath a member node,
   with type(s) as appropriate for the respective property.

   Known properties with the correct RR type, but which are for some
   reason invalid (for example because of an impossible value or because
   of an illegal number of RRs in the RRset), denote a broken catalog
   zone which MUST NOT be processed (see Section 5.1).

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   This specification defines a number of so-called properties, as well
   as a mechanism to allow implementers to store additional information
   in the catalog zone with Custom properties, see Section 4.5.  The
   meaning of such custom properties is determined by the implementation
   in question.

   Some properties are defined at the global level; others are scoped to
   apply only to a specific member zone.  This document defines a single
   mandatory global property in Section 4.3.1.  Member-specific
   properties are described in Section 4.3.

   More properties may be defined in future documents.

4.3.1.  Schema Version (version property)

   The catalog zone schema version is specified by an integer value
   embedded in a TXT RR named version.$CATZ.  All catalog zones MUST
   have a TXT RRset named version.$CATZ with exactly one RR.

   Catalog consumers MUST NOT apply catalog zone processing to

   *  zones without the version property

   *  zones with a version property with more than one RR in the RRset

   *  zones with a version property without an expected value in the
      version.$CATZ TXT RR

   These conditions signify a broken catalog zone which MUST NOT be
   processed (see Section 5.1).

   For this memo, the value of the version.$CATZ TXT RR MUST be set to
   "2", i.e.:

   version.$CATZ 0 IN TXT "2"

   NB: Version 1 was used in a draft version of this memo and reflected
   the implementation first found in BIND 9.11.

4.4.  Member Zone Properties

   Each member zone MAY have one or more additional properties,
   described in this chapter.  The member properties described in this
   document are all optional and implementations MAY choose to implement
   one, all or none of them.  Member zone properties are represented by
   RRsets below the corresponding member node.

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4.4.1.  Change of Ownership (coo property)

   The coo property facilitates controlled migration of a member zone
   from one catalog to another.

   A Change Of Ownership is signaled by the coo property in the catalog
   zone currently "owning" the zone.  The name of the new catalog is the
   value of a PTR record in the relevant coo property in the old
   catalog.  For example if member "" will migrate from
   catalog zone $OLDCATZ to catalog zone $NEWCATZ, this appears in the
   $OLDCATZ catalog zone as follows:

   <unique-N>.zones.$OLDCATZ 0 IN PTR
   coo.<unique-N>.zones.$OLDCATZ 0 IN PTR $NEWCATZ

   The PTR RRset MUST consist of a single PTR record.  More than one
   record in the RRset denotes a broken catalog zone which MUST NOT be
   processed (see Section 5.1).

   When a consumer of a catalog zone $OLDCATZ receives an update which
   adds or changes a coo property for a member zone in $OLDCATZ, it does
   _not_ migrate the member zone immediately.  The migration has to wait
   for an update of $NEWCATZ. in which the member zone is present.  The
   consumer MUST verify, before the actual migration, that coo property
   pointing to $NEWCATZ is still present in $OLDCATZ.

   Unless the member node label (i.e. <unique-N>) for the member is the
   same in $NEWCATZ, all its associated state for a just migrated zone
   MUST be reset (see Section 5.6).  Note that the owner of $OLDCATZ
   allows for the zone associated state to be taken over by the owner of
   $NEWCATZ by default.  To prevent the takeover of state, the owner of
   $OLDCATZ must remove this state by updating the associated properties
   or by performing a zone state reset (see Section 5.6) before or
   simultaneous with adding the coo property. (see also Section 7)

   The old owner may remove the member zone containing the coo property
   from $OLDCATZ once it has been established that all its consumers
   have processed the Change of Ownership.

4.4.2.  Groups (group property)

   With a group property, consumer(s) can be signaled to treat some
   member zones within the catalog zone differently.

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   The consumer MAY apply different configuration options when
   processing member zones, based on the value of the group property.
   The exact handling of configuration referred to by the group property
   value is left to the consumer's implementation and configuration.
   The property is defined by a TXT record in the sub-node labeled

   The producer MAY assign a group property to all, some, or none of the
   member zones within a catalog zone.  The producer MAY assign more
   than one group property to one member zone.  This will make it
   possible to transfer group information for different consumer
   operators in a single catalog zone.  Consumer operators SHOULD
   namespace their group properties to limit risk of clashes.

   The consumer MUST ignore group property values it does not

   When a consumer sees multiple values in a group property of a single
   member zone that it _does_ understand, it MAY choose to process
   multiple, any one or none of them.  This is left to the
   implementation.  Example

   <unique-1>.zones.$CATZ        0 IN PTR
   group.<unique-1>.zones.$CATZ  0 IN TXT    nodnssec
   <unique-2>.zones.$CATZ        0 IN PTR
   group.<unique-2>.zones.$CATZ  0 IN TXT    operator-x-sign-with-nsec3
   group.<unique-2>.zones.$CATZ  0 IN TXT    operator-y-nsec3

   The catalog zone (snippet) above is an example where the producer
   signals how the consumer(s) shall treat DNSSEC for the zones
   "" and ""

   For "", the consumer might be implemented and configured
   in the way that the member zone will not be signed with DNSSEC.  For
   "", the consumers, at two different operators, might be
   implemented and configured in the way that the member zone will be
   signed with a NSEC3 chain.

4.5.  Custom Properties (*.ext properties)

   Implementations and operators of catalog zones may choose to provide
   their own properties.  Custom properties can occur both globally, or
   for a specific member zone.  To prevent a name clash with future
   properties, such properties MUST be represented below the label ext.

   ext is not a placeholder.  A custom property is named as follows:

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   ; a global custom property:

   ; a member zone custom property:

   <your-property> may consist of one or more labels.

   Implementations SHOULD namespace their custom properties to limit
   risk of clashes with other implementations of catalog zones.  For
   example by including the name of the implementation in the property,
   e.g. like: <property-name>.<implementation-name>.ext.$CATZ.

   Implementations MAY use such properties on the member zone level to
   store additional information about member zones, for example to flag
   them for specific treatment.

   Further, implementations MAY use custom properties on the global
   level to store additional information about the catalog zone itself.
   While there may be many use cases for this, a plausible one is to
   store default values for custom properties on the global level, then
   overriding them using a property of the same name on the member level
   (= under the ext label of the member node) if so desired.  A property
   description should clearly say what semantics apply, and whether a
   property is global, member, or both.

   The meaning of the custom properties described in this section is
   determined by the implementation alone, without expectation of

5.  Nameserver Behavior

5.1.  General Requirements

   As it is a regular DNS zone, a catalog zone can be transferred using
   DNS zone transfers among nameservers.

   Catalog updates should be automatic, i.e., when a nameserver that
   supports catalog zones completes a zone transfer for a catalog zone,
   it SHOULD apply changes to the catalog within the running nameserver
   automatically without any manual intervention.

   Nameservers MAY allow loading and transfer of broken zones with
   incorrect catalog zone syntax (as they are treated as regular zones).
   The reason a catalog zone is considered broken SHOULD be communicated
   clearly to the operator (e.g. through a log message).

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   When a previously correct catalog zone becomes a broken catalog zone,
   because of an update through an incremental transfer or otherwise, it
   loses its catalog meaning.  No special processing occurs.  Member
   zones previously configured by this catalog MUST NOT be removed or
   reconfigured in any way.

   If a name server restarts with a broken catalog zone, the broken
   catalog SHOULD NOT prevent the name server from starting up and
   serving the member zones in the last valid version of the catalog

   Processing of a broken catalog SHALL start (or resume) when the
   catalog turns into a correct catalog zone, for example by an
   additional update (through zone transfer or updates) fixing the
   catalog zone.

   Similarly, when a catalog zone expires, it loses its catalog meaning
   and MUST no longer be processed as such.  No special processing
   occurs until the zone becomes fresh again.

5.2.  Member zone name clash

   If there is a clash between an existing zone's name (either from an
   existing member zone or otherwise configured zone) and an incoming
   member zone's name (via transfer or update), the new instance of the
   zone MUST be ignored and an error SHOULD be logged.

   A clash between an existing member zone's name and an incoming member
   zone's name (via transfer or update), may be an attempt to migrate a
   zone to a different catalog, but should not be treated as one except
   as described in Section 4.4.1.

5.3.  Member zone removal

   When a member zone is removed from a specific catalog zone, an
   authoritative server MUST NOT remove the zone and associated state
   data if the zone was not configured from that specific catalog zone.
   Only when the zone was configured from a specific catalog zone, and
   the zone is removed as a member from that specific catalog zone, the
   zone and associated state (such as zone data and DNSSEC keys) MUST be

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5.4.  Member node name change

   When via a single update or transfer, the member node's label value
   (<unique-N>) changes, catalog consumers MUST process this as a member
   zone removal including all the zone's associated state (as described
   in Section 5.3), immediately followed by processing the member as a
   newly to be configured zone in the same catalog.

5.5.  Migrating member zones between catalogs

   If all consumers of the catalog zones involved support the coo
   property, it is RECOMMENDED to perform migration of a member zone by
   following the procedure described in Section 4.4.1.  Otherwise a
   migration of a member zone from a catalog zone $OLDCATZ to a catalog
   zone $NEWCATZ has to be done by: first removing the member zone from
   $OLDCATZ; second adding the member zone to $NEWCATZ.

   If in the process of a migration some consumers of the involved
   catalog zones did not catch the removal of the member zone from
   $OLDCATZ yet (because of a lost packet or down time or otherwise),
   but did already see the update of $NEWCATZ, they may consider the
   update adding the member zone in $NEWCATZ to be a name clash (see
   Section 5.2) and as a consequence the member is not migrated to
   $NEWCATZ.  This possibility needs to be anticipated with a member
   zone migration.  Recovery from such a situation is out of the scope
   of this document.  It may for example entail a manually forced
   retransfer of $NEWCATZ to consumers after they have been detected to
   have received and processed the removal of the member zone from

5.6.  Zone-associated state reset

   It may be desirable to reset state (such as zone data and DNSSEC
   keys) associated with a member zone.

   A zone state reset may be performed by a change of the member node's
   name (see Section 5.4).

6.  Implementation and operational Notes

   Although any valid domain name can be used for the catalog name
   $CATZ, it is RECOMMENDED to use either a domain name owned by the
   catalog producer, or to use a name under a suitable Special-Use
   Domain Name [RFC6761].

   Catalog zones on secondary nameservers would have to be set up
   manually, perhaps as static configuration, similar to how ordinary
   DNS zones are configured when catalog zones or another automatic

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   configuration mechanism is not in place.  The secondary additionally
   needs to be configured as a catalog consumer for the catalog zone to
   enable processing of the member zones in the catalog, such as
   automatic synchronization of the member zones for secondary service.

   Operators of catalog consumers should note that secondary name
   servers may receive DNS NOTIFY messages [RFC1996] for zones before
   they are seen as newly added member zones to the catalog from which
   that secondary is provisioned.

   Although they are regular DNS zones, catalog zones contain only
   information for the management of a set of authoritative nameservers.
   For this reason, operators may want to limit the systems able to
   query these zones.

   Querying/serving catalog zone contents may be inconvenient via DNS
   due to the nature of their representation.  An administrator may
   therefore want to use a different method for looking at data inside
   the catalog zone.  Typical queries might include dumping the list of
   member zones, dumping a member zone's effective configuration,
   querying a specific property value of a member zone, etc.  Because of
   the structure of catalog zones, it may not be possible to perform
   these queries intuitively, or in some cases, at all, using DNS QUERY.
   For example, it is not possible to enumerate the contents of a multi-
   valued property (such as the list of member zones) with a single
   QUERY.  Implementations are therefore advised to provide a tool that
   uses either the output of AXFR or an out-of-band method to perform
   queries on catalog zones.

   Great power comes with great responsibility: Catalog zones simplify
   zone provisioning by orchestrating zones on secondary name servers
   from a single data source - the catalog.  Hence, the catalog producer
   has great power and changes must be treated carefully.  For example
   if the catalog is generated by some script and this script for
   whatever reason generates an empty catalog, millions of member zones
   may get deleted from their secondaries within seconds and all the
   affected domains may be offline in a blink.

7.  Security Considerations

   As catalog zones are transmitted using DNS zone transfers, it is
   RECOMMENDED that catalog zone transfer are protected from unexpected
   modifications by way of authentication, for example by using TSIG
   [RFC8945], or Strict or Mutual TLS authentication with DNS Zone
   transfer over TLS [RFC9103].

   Use of DNS UPDATE [RFC2136] to modify the content of catalog zones
   SHOULD similarly be authenticated.

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   Zone transfers of member zones SHOULD similarly be authenticated.
   TSIG shared secrets used for member zones SHOULD NOT be mentioned in
   the catalog zone data.  However, key identifiers may be shared within
   catalog zones.

   Catalog zones reveal the zones served by the consumers of the catalog
   zone.  It is RECOMMENDED to limit the systems able to query these
   zones.  It is RECOMMENDED to transfer catalog zones confidentially

   As with regular zones, primary and secondary nameservers for a
   catalog zone may be operated by different administrators.  The
   secondary nameservers may be configured as a catalog consumer to
   synchronize catalog zones from the primary, but the primary's
   administrators may not have any administrative access to the

   Administrative control over what zones are served from the configured
   name servers shifts completely from the server operator (consumer) to
   the "owner" (producer) of the catalog zone content.

   With migration of member zones between catalogs using the coo
   property, it is possible for the owner of the target catalog (i.e.
   $NEWCATZ) to take over all its associated state with the zone from
   the original owner (i.e. $OLDCATZ) by maintaining the same member
   node label (i.e. <unique-N>).  To prevent the takeover of the zone
   associated state, the original owner has to enforce a zone state
   reset by changing the member node label (see Section 5.6) before or
   simultaneously with adding the coo property.

8.  Acknowledgements

   Our deepest thanks and appreciation go to Stephen Morris, Ray Bellis
   and Witold Krecicki who initiated this draft and did the bulk of the

   Catalog zones originated as the chosen method among various proposals
   that were evaluated at ISC for easy zone management.  The chosen
   method of storing the catalog as a regular DNS zone was proposed by
   Stephen Morris.

   The initial authors discovered that Paul Vixie's earlier [Metazones]
   proposal implemented a similar approach and reviewed it.  Catalog
   zones borrow some syntax ideas from Metazones, as both share this
   scheme of representing the catalog as a regular DNS zone.

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   Thanks to Leo Vandewoestijne.  Leo's presentation in the DNS devroom
   at the FOSDEM'20 [FOSDEM20] was one of the motivations to take up and
   continue the effort of standardizing catalog zones.

   Thanks to Brian Conry, Klaus Darilion, Brian Dickson, Tony Finch,
   Evan Hunt, Shane Kerr, Patrik Lundin, Matthijs Mekking, Victoria
   Risk, Josh Soref, Petr Spacek, Michael StJohns, Carsten Strotmann and
   Tim Wicinski for reviewing draft proposals and offering comments and

9.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <>.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              DOI 10.17487/RFC1982, August 1996,

   [RFC1996]  Vixie, P., "A Mechanism for Prompt Notification of Zone
              Changes (DNS NOTIFY)", RFC 1996, DOI 10.17487/RFC1996,
              August 1996, <>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [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,

   [RFC2606]  Eastlake 3rd, D. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, DOI 10.17487/RFC2606, June 1999,

   [RFC6761]  Cheshire, S. and M. Krochmal, "Special-Use Domain Names",
              RFC 6761, DOI 10.17487/RFC6761, February 2013,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

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   [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,

   [RFC9103]  Toorop, W., Dickinson, S., Sahib, S., Aras, P., and A.
              Mankin, "DNS Zone Transfer over TLS", RFC 9103,
              DOI 10.17487/RFC9103, August 2021,

10.  Informative References

   [FOSDEM20] Vandewoestijne, L., "Extending Catalog zones - another
              approach in automating maintenance", 2020,

              Vixie, P., "Federated Domain Name Service Using DNS
              Metazones", 2005,

Appendix A.  Implementation Status

   *Note to the RFC Editor*: please remove this entire appendix before

   In the following implementation status descriptions, "DNS Catalog
   Zones" refers to DNS Catalog Zones as described in this document.

   *  Knot DNS 3.1 (released August 2, 2021) supports both producing and
      consuming of catalog zones, including the group property.

   *  PowerDNS from version 4.7 (released October 3, 2022) supports both
      producing and consuming of catalog zones.

   *  Proof of concept python scripts (
      Hackathon/NSDCatZ) that can be used for both generating and
      consuming DNS Catalog Zones with NSD have been developed during
      the hackathon at the IETF-109.

   *  BIND 9.18.3+ supports version 2 catalog zones as described in this

   Interoperability between the above implementations has been tested
   during the hackathon at the IETF-109.

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Appendix B.  Change History

   *Note to the RFC Editor*: please remove this entire appendix before

   *  draft-muks-dnsop-dns-catalog-zones-00

   |  Initial public draft.

   *  draft-muks-dnsop-dns-catalog-zones-01

   |  Added Witold, Ray as authors.  Fixed typos, consistency issues.
   |  Fixed references.  Updated Area.  Removed newly introduced custom
   |  RR TYPEs.  Changed schema version to 1.  Changed TSIG requirement
   |  from MUST to SHOULD.  Removed restrictive language about use of
   |  DNS QUERY.  When zones are introduced into a catalog zone, a
   |  primary SHOULD first make the new zones available for transfers
   |  first (instead of MUST).  Updated examples, esp. use IPv6 in
   |  examples per Fred Baker.  Add catalog zone example.

   *  draft-muks-dnsop-dns-catalog-zones-02

   |  Addressed some review comments by Patrik Lundin.

   *  draft-muks-dnsop-dns-catalog-zones-03

   |  Revision bump.

   *  draft-muks-dnsop-dns-catalog-zones-04

   |  Reordering of sections into more logical order.  Separation of
   |  multi-valued properties into their own category.

   *  draft-toorop-dnsop-dns-catalog-zones-00

   |  New authors to pickup the editor pen on this draft
   |  Remove data type definitions for zone properties Removing
   |  configuration of member zones through zone properties altogether
   |  Remove Open issues and discussion Appendix, which was about zone
   |  options (including primary/secondary relationships) only.

   *  draft-toorop-dnsop-dns-catalog-zones-01

   |  Added a new section "The Serial Property", introducing a new
   |  mechanism which can help with disseminating zones from the primary
   |  to the secondary nameservers in a timely fashion more reliably.

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   |  Three different ways to provide a "serial" property with a member
   |  zone are offered to or the workgroup for discussion.
   |  Added a new section "Implementation Status", listing production
   |  ready, upcoming and Proof of Concept implementations, and
   |  reporting on interoperability of the different implementations.

   *  draft-toorop-dnsop-dns-catalog-zones-02

   |  Adding the coo property for zone migration in a controlled fashion
   |  Adding the group property for reconfigure settings of member zones
   |  in an atomic update
   |  Adding the epoch property to reset zone associated state in a
   |  controlled fashion

   *  draft-toorop-dnsop-dns-catalog-zones-03

   |  Big cleanup!
   |  Introducing the terms catalog consumer and catalog producer
   |  Reorganized topics to create a more coherent whole
   |  Properties all have consistent format now
   |  Try to assume the least possible from implementations w.r.t.:
   |  1) Predictability of the <unique-N> IDs of member zones
   |  2) Whether or not fallback catalog zones can be found for a member
   |  3) Whether or not a catalog consumer can maintain state

   *  draft-toorop-dnsop-dns-catalog-zones-04

   |  Move Implementation status to appendix
   |  Miscellaneous textual improvements
   |  coo property points to $NEWCATZ (and not zones.$NEWCATZ)
   |  Remove suggestion to increase serial and remove member zone from
   |  $OLDCATZ after migration

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   |  More consistent usage of the terms catalog consumer and catalog
   |  producer throughout the document
   |  Better (safer) description of resetting refresh timers of member
   |  zones with the serial property
   |  Removing a member MUST remove zone associated state
   |  Make authentication requirements a bit less prescriptive in
   |  security considerations
   |  Updated implementation status for KnotDNS
   |  Describe member node name changes and update "Zone associated
   |  state reset" to use that as the mechanism for it.
   |  Add Peter Thomassen as co-author
   |  Complete removal of the epoch property.  We consider consumer
   |  optimizations with predictable member node labels (for example
   |  based on a hash) out of the scope of this document.
   |  Miscellaneous editorial improvements

   *  draft-toorop-dnsop-dns-catalog-zones-05

   |  Add Kees Monshouwer as co-author
   |  Removed the "serial" property
   |  Allow custom properties on the global level

   *  draft-toorop-dnsop-dns-catalog-zones-06

   |  Move administrative control explanation to Security Considerations
   |  Move comment on query methods to Implementation Notes
   |  Clarify what happens on expiry
   |  Clarify catalog consumer behavior when MUST condition is violated
   |  Better text on ordering of operations for Change of Ownership
   |  Suggest to namespace custom properties
   |  Clarify how to handle property record with wrong type

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   |  Cover the case of multiple different <unique-N>'s having the same
   |  value
   |  Recommendations for naming catalog zones
   |  Add and operational note about notifies for not yet existing zones
   |  Add text about name server restarts with broken zones
   |  Great power comes with great responsibility (Thanks Klaus!)
   |  Mention the new BIND implementation
   |  All invalid properties cause a broken catalog zone, including
   |  invalid group and version properties.
   |  Add Aram Sargsyan as author (he did the BIND9 implementation)
   |  group properties can have more than one value

   *  draft-toorop-dnsop-dns-catalog-zones-07

   |  Some spelling fixes from Tim Wicinski and Josh Soref
   |  Replace SHOULDs with MUSTs for ignoring things that are
   |  meaningless to a catalog consumer (Thanks Michael StJohns)
   |  Update the list of people to thank in the Acknowledgements section
   |  Mention PowerDNS support of catalog zones from version 4.7.0
   |  onwards

Authors' Addresses

   Peter van Dijk
   Den Haag

   Libor Peltan

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   Ondrej Sury
   Internet Systems Consortium

   Willem Toorop
   NLnet Labs
   Science Park 400
   1098 XH Amsterdam

   Kees Monshouwer

   Peter Thomassen
   deSEC, SSE - Secure Systems Engineering

   Aram Sargsyan
   Internet Systems Consortium

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