DNS Catalog Zones
draft-ietf-dnsop-dns-catalog-zones-02

DNSOP Working Group                                          P. van Dijk
Internet-Draft                                                  PowerDNS
Intended status: Standards Track                               L. Peltan
Expires: 26 August 2021                                           CZ.NIC
                                                                 O. Sury
                                             Internet Systems Consortium
                                                               W. Toorop
                                                              NLnet Labs
                                                       L. Vandewoestijne
                                                        22 February 2021

                           DNS Catalog Zones
                 draft-ietf-dnsop-dns-catalog-zones-02

Abstract

   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
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   This Internet-Draft will expire on 26 August 2021.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights

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   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Description . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Catalog Zone Structure  . . . . . . . . . . . . . . . . . . .   4
     4.1.  SOA and NS Records  . . . . . . . . . . . . . . . . . . .   4
     4.2.  Catalog Zone Schema Version . . . . . . . . . . . . . . .   4
     4.3.  List of Member Zones  . . . . . . . . . . . . . . . . . .   5
   5.  Properties  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  The Group Property  . . . . . . . . . . . . . . . . . . .   6
     5.2.  Custom properties . . . . . . . . . . . . . . . . . . . .   6
     5.3.  The Epoch Property  . . . . . . . . . . . . . . . . . . .   6
       5.3.1.  The TIMESTAMP Resource Record . . . . . . . . . . . .   7
     5.4.  The Serial Property . . . . . . . . . . . . . . . . . . .   8
       5.4.1.  The SERIAL Resource Record  . . . . . . . . . . . . .   9
       5.4.2.  SERIAL RDATA Wire Format  . . . . . . . . . . . . . .   9
       5.4.3.  SERIAL Presentation Format  . . . . . . . . . . . . .   9
       5.4.4.  SERIAL RR Usage - option 1  . . . . . . . . . . . . .   9
       5.4.5.  SERIAL RR Usage - option 2  . . . . . . . . . . . . .  10
       5.4.6.  Serial property as TXT RR - option 3  . . . . . . . .  10
   6.  Nameserver Behavior . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  General Requirements  . . . . . . . . . . . . . . . . . .  11
   7.  Migrating zones between catalogs  . . . . . . . . . . . . . .  12
   8.  Updating Catalog Zones  . . . . . . . . . . . . . . . . . . .  13
     8.1.  Implementation Notes  . . . . . . . . . . . . . . . . . .  13
   9.  Implementation Status . . . . . . . . . . . . . . . . . . . .  13
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  14
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  14
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  14
   13. Normative References  . . . . . . . . . . . . . . . . . . . .  15
   14. Informative References  . . . . . . . . . . . . . . . . . . .  16
   Appendix A.  Change History (to be removed before final
           publication)  . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   *DISCLAIMER:* The authors wish to apologize for the current state of
   the document, which is in a bit of a rough and somewhat inconsistent
   shape.  It contains multiple different approaches for similar tasks,
   some of which are described spread out over the document.  We will
   work with the DNSOP working group to improve on this.

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   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
   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.

   The contents and representation of catalog zones are described in
   Section 3.  Nameserver behavior is described in Section 6.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   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.

   "$CATZ"  Used in examples as a placeholder to represent the domain
      name of the catalog zone itself (c.f. $ORIGIN).

   Member node  The DNS name of the DNS subtree representing a given
      member zone (two levels below "$CATZ").

3.  Description

   A catalog zone is a specially crafted DNS zone that contains, as DNS
   zone content:

   *  A list of DNS zones (called "member zones"), plus properties
      associated with those zones.

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   Implementations of catalog zones SHOULD ignore any RR in the catalog
   zone which is meaningless or useless to the implementation.

   Authoritative servers may be preconfigured with multiple catalog
   zones, each associated with a different set of configurations.  A
   member zone can as such be reconfigured with a different set of
   preconfigured settings by removing it as a member of one catalog zone
   and making it a member of another.

   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.  It is not expected that the content of
   catalog zones will 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 syntactically
   correct 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,
   secondary nameservers might not notice updates to the catalog zone's
   contents.

   There is no requirement to be able to query the catalog zone via
   recursive nameservers.  Implementations of catalog zones MUST ignore
   and MUST NOT assume or require NS records at the apex.  However, at
   least one is still required so that catalog zones are syntactically
   correct DNS zones.  A single NS RR with an NSDNAME field containing
   the absolute name "invalid." is RECOMMENDED [RFC2606].

4.2.  Catalog Zone Schema Version

   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 at least one RR.  Primary
   and secondary nameservers MUST NOT apply catalog zone processing to
   zones without the expected value in one of the RRs in the
   "version.$CATZ" TXT RRset, but they may be transferred as ordinary
   zones.  For this memo, the value of one of the RRs in the
   "version.CATZ" TXT RRset MUST be set to "2", i.e.

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   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.

4.3.  List of 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.

   The names of member zones are represented on the RDATA side (instead
   of as a part of owner names) so that all valid domain names may be
   represented regardless of their length [RFC1035].

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

   <unique-1>.zones.$CATZ 0 IN PTR example.com.
   <unique-2>.zones.$CATZ 0 IN PTR example.net.
   <unique-3>.zones.$CATZ 0 IN PTR example.org.

   where "<unique-N>" is a label that tags each record in the
   collection. "<unique-N>" has a unique value in the collection.

   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 6.1, Paragraph 8).

   Having the zones uniquely tagged with the "<unique-N>" label ensures
   that additional RRs can be added at or below the member node, for
   signifying member-zone-specific information (described below).
   Further, if member zones do not share a PTR RRset, the list of member
   zones can be split over multiple DNS messages in a zone transfer.

   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.

5.  Properties

   Member zones may optionally be assigned additional properties
   represented by RRsets below the corresponding member node.  This
   document suggests a few properties which are all optional to
   implement.

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5.1.  The Group Property

   The group property allows to add at most one tag per member zone.
   The consumer might handle/configure member zones differently based on
   the tag.  The group property is represented by a TXT Resource Record,
   for example:

   <unique-1>.zones.$CATZ        0 IN PTR    example.com.
   group.<unique-1>.zones.$CATZ  0 IN TXT    sign-with-nsec3
   <unique-2>.zones.$CATZ        0 IN PTR    example.net.
   group.<unique-2>.zones.$CATZ  0 IN TXT    nodnssec

5.2.  Custom properties

   Implementations and operators of catalog zones may choose to provide
   their own properties below the label "private-extension.<unique-
   N>.zones.$CATZ". "private-extension" is not a placeholder, so a
   custom property would have the domain name "<your-label>.private-
   extension.<unique-N>.zones.$CATZ"

5.3.  The Epoch Property

   The epoch property is represented by a the "TIMESTAMP" Resource
   Record (see Section 5.3.1).

   *  "epoch.<unique-N>.zones.$CATZ 0 IN TIMESTAMP ..."

   When a member zone's epoch changes, the secondary server resets the
   member zone's state.  The secondary can detect a member zone epoch
   change as follows:

   *  When the epoch changes, the primary will set the TIMESTAMP RR of
      the member zone's epoch property to the current time.

   *  When the secondary processes a member node with an epoch property
      that is larger than the point in time when the member zone itself
      was last retrieved, then a new epoch has begun.

   The steps entailed in the process of resetting the zone state depend
   on the operational context of the secondary (e.g. regenerate DNSSEC
   keys).

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5.3.1.  The TIMESTAMP Resource Record

   Epoch values (both for the catalog zone and for member zones) are
   provided with a TIMESTAMP Resource Record.  The Type value for the
   TIMESTAMP RR is TBD.  The TIMESTAMP RR is class independent [FIXME:
   Should it?].  The RDATA of the resource record consist of a single
   field: Timestamp.

5.3.1.1.  TIMESTAMP RDATA Wire Format

   The TIMESTAMP RDATA wire format is encoded as follows:

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           Timestamp                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The wire format is identical to the wire format of the Signature
   Expiration and Inception Fields of the RRSIG RR ([RFC4034] section
   3.1.5) and follows the same rules with respect to wrapping.

   [FIXME: Should it be 64 bit?  I did it this way because a) RRSIG
   implementations already exist, b) for 64-bit, we also need to discuss
   timestamp precision (float?)]

5.3.1.2.  TIMESTAMP RDATA Presentation Format

   The presentation format is identical to that of the Signature
   Expiration and Inception Fields of the RRSIG RR ([RFC4034] section
   3.2).  Example:

   epoch.$CATZ                   0 IN TIMESTAMP    20210304124652
   epoch.<unique-1>.zones.$CATZ  0 IN TIMESTAMP    20201231235959

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5.4.  The Serial Property

   The current default mechanism for prompting notifications of zone
   changes from a primary nameserver to the secondaries via DNS NOTIFY
   [RFC1996], can be unreliable due to packet loss, or secondary
   nameservers temporarily not being reachable.  In such cases the
   secondary might pick up the change only after the refresh timer runs
   out, which might take long time and be out of the control of the
   primary nameserver operator.  Low refresh values in the zones being
   served can alleviate update delays, but burden both the primary and
   secondary nameservers with more refresh queries, especially with
   larger numbers of secondary nameservers serving large numbers of
   zones.  To mitigate this, updates of zones MAY be signalled via
   catalog zones with the help of a "serial" property.

   The serial number in the SOA record of the most recent version of a
   member zone MAY be provided by a "serial" property.  When a "serial"
   property is present for a member zone, implementations of catalog
   zones MAY assume this number to be the current serial number in the
   SOA record of the most recent version of the member zone.

   Nameservers that are secondary for that member zone, MAY compare the
   "serial" property with the SOA serial since the last time the zone
   was fetched.  When the "serial" property is larger, the secondary MAY
   initiate a zone transfer immediately without doing a SOA query first.
   The SOA query may be omitted, because the SOA serial has been
   obtained reliably via the catalog zone already.

   When a "serial" property is present for a member zone and it matches
   the SOA serial of that member zone, implementations of catalog zones
   which are secondary for that member zone MAY ignore the refresh time
   in the SOA record of the member zone and rely on updates via the
   "serial" property of the member zone.  A refresh timer of a catalog
   zone MUST not be ignored.

   Primary nameservers MAY be configured to omit sending DNS NOTIFY
   messages to secondary nameservers which are known to process the
   "serial" property of the member zones in that catalog.  However they
   MAY also combine signalling of zone changes with the "serial"
   property of a member zone, as well as sending DNS NOTIFY messages, to
   anticipate slow updates of the catalog zone (due to packet loss or
   other reasons) and to cater for secondaries that do not process the
   "serial" property.

   All comparisons of serial numbers MUST use "Serial number
   arithmetic", as defined in [RFC1982]

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   *Note to the DNSOP Working Group*: In this section we present three
   ways to provide a "serial" property with a member zone.  The first
   two ways make use of a new Resource Record type: SERIAL as described
   in Section 5.4.1, Section 5.4.2 and Section 5.4.3.  The two different
   ways to provide a "serial" property with the SERIAL RR are described
   in Section 5.4.4 and Section 5.4.5 respectively.  The third way is
   with a TXT RR and is described in Section 5.4.6.  Additionally,
   https://mailarchive.ietf.org/arch/msg/dnsop/
   DcdnwolVVpMjQzR4gtlrLyXsYtk/
   (https://mailarchive.ietf.org/arch/msg/dnsop/
   DcdnwolVVpMjQzR4gtlrLyXsYtk/) suggests reusing CSYNC instead of
   creating a new SERIAL rrtype.  (That message also contains other
   ideas not yet fully considered by the authors.)

5.4.1.  The SERIAL Resource Record

   The "serial" property value is provided with a SERIAL Resource
   Record.  The Type value for the SERIAL RR is TBD.  The SERIAL RR is
   class independent.  The RDATA of the resource record consist of a
   single field: Serial.

5.4.2.  SERIAL RDATA Wire Format

   The SERIAL RDATA wire format is encoded as follows:

                        1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Serial                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

5.4.2.1.  The Serial Field

   The Serial field is a 32-bit unsigned integer in network byte order.
   It is the serial number of the member zone's SOA record ([RFC1035]
   section 3.3.13).

5.4.3.  SERIAL Presentation Format

   The presentation format of the RDATA portion is as follows:

   The Serial fields is represented as an unsigned decimal integer.

5.4.4.  SERIAL RR Usage - option 1

   The "serial" property of a member zone is provided by a SERIAL RRset
   with a single SERIAL RR named "serial.<unique-N>.zones.$CATZ".

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   For example, if a catalog zone lists three zones "example.com.",
   "example.net." and "example.org.", and a "serial" property is
   provided for each of them, the RRs would appear as follows:

   <unique-1>.zones.$CATZ        0 IN PTR    example.com.
   serial.<unique-1>.zones.$CATZ 0 IN SERIAL 2020111712
   <unique-2>.zones.$CATZ        0 IN PTR    example.net.
   serial.<unique-2>.zones.$CATZ 0 IN SERIAL 2020111709
   <unique-3>.zones.$CATZ        0 IN PTR    example.org.
   serial.<unique-3>.zones.$CATZ 0 IN SERIAL 2020112405

5.4.5.  SERIAL RR Usage - option 2

   The "serial" property of a member zone is provided by a SERIAL RRset
   on the same owner name as the PTR RR of the member zone.

   For example, if a catalog zone lists three zones "example.com.",
   "example.net." and "example.org.", and a "serial" property is
   provided for each of them, the RRs would appear as follows:

   <unique-1>.zones.$CATZ 0 IN PTR    example.com.
   <unique-1>.zones.$CATZ 0 IN SERIAL 2020111712
   <unique-2>.zones.$CATZ 0 IN PTR    example.net.
   <unique-2>.zones.$CATZ 0 IN SERIAL 2020111709
   <unique-3>.zones.$CATZ 0 IN PTR    example.org.
   <unique-3>.zones.$CATZ 0 IN SERIAL 2020112405

5.4.6.  Serial property as TXT RR - option 3

   The "serial" property of a member zone is provided by a TXT RRset
   with a single TXT RR named "serial.<unique-N>.zones.$CATZ".  The TXT
   RR contains a single RDATA field consisting of the textual
   representation of the SOA serial number.

   For example, if a catalog zone lists three zones "example.com.",
   "example.net." and "example.org.", and a "serial" property is
   provided for each of them, the RRs would appear as follows:

   <unique-1>.zones.$CATZ        0 IN PTR example.com.
   serial.<unique-1>.zones.$CATZ 0 IN TXT 2020111712
   <unique-2>.zones.$CATZ        0 IN PTR example.net.
   serial.<unique-2>.zones.$CATZ 0 IN TXT 2020111709
   <unique-3>.zones.$CATZ        0 IN PTR example.org.
   serial.<unique-3>.zones.$CATZ 0 IN TXT 2020112405

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6.  Nameserver Behavior

6.1.  General Requirements

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

   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.  It may be inconvenient to serve some contents of
   catalog zones via DNS queries anyway due to the nature of their
   representation.  A separate method of querying entries inside the
   catalog zone may be made available by nameserver implementations (see
   Section 8.1).

   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.

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

   A catalog zone can be updated via DNS UPDATE on a reference primary
   nameserver, or via zone transfers.  Nameservers MAY allow loading and
   transfer of broken zones with incorrect catalog zone syntax (as they
   are treated as regular zones), but nameservers MUST NOT process such
   broken zones as catalog zones.  For the purpose of catalog
   processing, the broken catalogs MUST be ignored.

   [FIXME: reword this if we do coo, or the CSYNC immediate flag, or
   something else] If there is a clash between an existing member zone's
   name 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.

   When zones are deleted from a catalog zone, a primary MAY delete the
   member zone immediately.  It is up to the secondary nameserver to
   handle this condition correctly.

   [FIXME: we now have two mechanisms to reset zones and we should bring
   that back to one at some point.]

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   When the "<unique-N>" label of a member zone changes and the zone
   does not have an epoch property (see Section 5.3), all its associated
   state MUST be reset, including the zone itself.  This can be relevant
   for example when zone ownership is changed.  In that case one does
   not want the new owner to inherit the metadata.  Other situations
   might be resetting DNSSEC state, or forcing a new zone transfer.
   This reset is tied to "<unique-N" because A simple removal followed
   by an addition of the member zone would be insufficient for this
   purpose because it is infeasible for secondaries to track, due to
   missed notifies or being offline during the removal/addition.

   If an epoch property is present, the steps in Section 5.3 describe
   how to signal a zone reset.

7.  Migrating zones between catalogs

   [FIXME: clarify 2119 status of this and other properties and
   features.  MUST?  SHOULD?  MAY?  Because this one has security
   implications, also clearly note how ownership changes work without
   coo - namely, removing a member zone from catz A will cause catz B or
   C or D to pick up the zone on their next refresh. ]

   If there is a clash between an existing member zone's name and an
   incoming member zone's name (via transfer or update), this may be an
   attempt to do a Change Of Ownership.

   A Change Of Ownership is signaled by the 'coo' property in the
   catalog zone currently owning the zone.  The 'coo' property looks
   like "coo.<unique-N>.old.catalog PTR new.catalog".

   If there is no 'coo' property that resolves the clash, the zone
   remains owned by its current catalog and an error may be logged.

   If there is a 'coo' property that resolves the clash, member zone
   ownership is transferred to 'new.catalog'.

   [FIXME: remove this after we agree on what IDs even mean and how zone
   resets work within and between catalog zones] If "<unique-N>" for the
   member zone is different in the new catalog zone, associated state is
   reset as described earlier, including existing zone data.

   The new owner is advised to increase the serial of the member zone
   after the ownership change, so that the old owner can detect that the
   transition is done.  The old owner then removes the member zone from
   "old.catalog".

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8.  Updating Catalog Zones

   TBD: Explain updating catalog zones using DNS UPDATE.

8.1.  Implementation Notes

   Catalog zones on secondary nameservers would have to be setup
   manually, perhaps as static configuration, similar to how ordinary
   DNS zones are configured.  Members of such catalog zones will be
   automatically synchronized by the secondary after the catalog zone is
   configured.

   An administrator may want to look at data inside a 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.

9.  Implementation Status

   *Note to the RFC Editor*: please remove this entire section before
   publication.

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

   *  Knot DNS has processing of DNS Catalog Zones since Knot DNS
      Version 3.0.0, which was released on September 9, 2020.

   *  Knot DNS has generation of DNS Catalog Zones on a development
      branch (https://gitlab.nic.cz/knot/knot-dns/-/tree/
      catalog_generate).

   *  PowerDNS has a proof of concept external program called PowerCATZ
      (https://github.com/PowerDNS/powercatz/), that can process DNS
      Catalog Zones.

   *  Proof of concept python scripts (https://github.com/IETF-
      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.

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

10.  Security Considerations

   As catalog zones are transmitted using DNS zone transfers, it is key
   for these transfers to be protected from unexpected modifications on
   the route.  So, catalog zone transfers SHOULD be authenticated using
   TSIG [RFC8945].  A primary nameserver SHOULD NOT serve a catalog zone
   for transfer without using TSIG and a secondary nameserver SHOULD
   abandon an update to a catalog zone that was received without using
   TSIG.

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

   Zone transfers of member zones SHOULD similarly be authenticated
   using TSIG [RFC8945].  The TSIG shared secrets used for member zones
   MUST NOT be mentioned anywhere in the catalog zone data.  However,
   key identifiers may be shared within catalog zones.

   Catalog zones do not need to be signed using DNSSEC, their zone
   transfers being authenticated by TSIG.  Signed zones MUST be handled
   normally by nameservers, and their contents MUST NOT be DNSSEC-
   validated.

11.  IANA Considerations

   This document has no IANA actions.

   #

12.  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
   work.

   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 borrows 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 Brian Conry, Tony Finch, Evan Hunt, Patrik Lundin, Victoria
   Risk, Carsten Strotmann, Peter Thomassen and Kees Monshouwer for
   reviewing draft proposals and offering comments and suggestions.

   Thanks to Klaus Darilion who came up with the idea for the "serial"
   property during the hackathon at the IETF-109.  Thanks also to Shane
   Kerr, Petr Spacek, Brian Dickson for further brainstorming and
   discussing the "serial" property and how it would work best with
   catalog zones.

13.  Normative References

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
              November 1987, <https://www.rfc-editor.org/info/rfc1035>.

   [RFC1982]  Elz, R. and R. Bush, "Serial Number Arithmetic", RFC 1982,
              DOI 10.17487/RFC1982, August 1996,
              <https://www.rfc-editor.org/info/rfc1982>.

   [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>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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>.

   [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>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

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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,
              <https://www.rfc-editor.org/info/rfc8945>.

14.  Informative References

   [Metazones]
              Vixie, P., "Federated Domain Name Service Using DNS
              Metazones", 2005, <http://ss.vix.su/~vixie/mz.pdf>.

Appendix A.  Change History (to be removed before final publication)

   *  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

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   |  
   |  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.
   |  
   |  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.

Authors' Addresses

   Peter van Dijk
   PowerDNS
   Den Haag
   Netherlands

   Email: peter.van.dijk@powerdns.com

   Libor Peltan
   CZ.NIC
   Czechia

   Email: libor.peltan@nic.cz

   Ondrej Sury
   Internet Systems Consortium
   Czechia

   Email: ondrej@isc.org

   Willem Toorop
   NLnet Labs
   Science Park 400
   1098 XH Amsterdam
   Netherlands

   Email: willem@nlnetlabs.nl

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   Leo Vandewoestijne
   Netherlands

   Email: leo@dns.company

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