DNSOP Working Group P. van Dijk
Internet-Draft PowerDNS
Intended status: Standards Track L. Peltan
Expires: October 16, 2020 CZ.NIC
O. Sury
Internet Systems Consortium
W. Toorop
NLnet Labs
L. Vandewoestijne
April 14, 2020
DNS Catalog Zones
draft-toorop-dnsop-dns-catalog-zones-01
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
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 October 16, 2020.
Copyright Notice
Copyright (c) 2020 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
van Dijk, et al. Expires October 16, 2020 [Page 1]
Internet-Draft dns-catalog-zones April 2020
carefully, as they describe your rights 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 . . . . . . . . . . . . . . . . . . 4
5. Nameserver Behavior . . . . . . . . . . . . . . . . . . . . . 5
5.1. General Requirements . . . . . . . . . . . . . . . . . . 5
6. Updating Catalog Zones . . . . . . . . . . . . . . . . . . . 7
6.1. Implementation Notes . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 9
Appendix A. Change History (to be removed before final
publication) . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
The data in 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, the changes are propagated 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 zone.
van Dijk, et al. Expires October 16, 2020 [Page 2]
Internet-Draft dns-catalog-zones April 2020
The contents and representation of catalog zones are described in
Section 3. Nameserver behavior is described in Section 5.
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.
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).
3. Description
A catalog zone is a specially crafted DNS zone that contains, as DNS
zone data:
o A list of DNS zones (called "member zones").
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.
An implementation of catalog zones MAY allow the catalog to contain
other catalog zones as member zones.
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.
van Dijk, et al. Expires October 16, 2020 [Page 3]
Internet-Draft dns-catalog-zones April 2020
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.
Should the zone be made available for querying, the SOA record's
MINIMUM field's value is the negative cache time (as defined in
[RFC2308]). Since recursive nameservers are not expected to be able
to access (and subsequently cache) entries from a catalog zone a
value of zero (0) is RECOMMENDED.
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
embeded in a TXT RR named "version.$CATZ". All catalog zones MUST
have a TXT RRset named "version.$CATZ" with at least one RR. Primary
and secondary nameservers MUST NOT use catalog zones without the
expected value in one of the RRs in the "version.$CATZ" TXT RRset,
but they may be transferred as ordinary zones. For this memo, the
value of one of the RRs in the "version.$CATZ" TXT RRset MUST be set
to "2", i.e.
version.$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 domain names
under the owner name "zones" where "zones" is a direct child domain
of the catalog zone.
van Dijk, et al. Expires October 16, 2020 [Page 4]
Internet-Draft dns-catalog-zones April 2020
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 RRs would appear as follows:
<m-unique-1>.zones.$CATZ 0 IN PTR example.com.
<m-unique-2>.zones.$CATZ 0 IN PTR example.net.
<m-unique-3>.zones.$CATZ 0 IN PTR example.org.
where "<m-unique-N>" is a label that uniquely tags each record in the
collection.
Having a large number of member zones in a single RRset may cause the
RRset to be too large to be conveyed via DNS messages which make up a
zone transfer. Having the zones uniquely tagged with the "<m-unique-
N>" label ensures the list of member zones can be split over multiple
DNS messages in a zone transfer.
The "<m-unique-N>" label also enables the state for a zone to be
reset. (see Section 6) As long as no zone state needs to be reset at
the authoritative nameservers, the unique label associated with a
zone SHOULD remain the same.
The CLASS field of every RR in a catalog zone MUST be IN (1).
The TTL field's value is not specially defined by this memo. Catalog
zones are for authoritative nameserver management only and are not
intended for general querying via recursive resolvers and therefore a
value of zero (0) is RECOMMENDED.
It is an error for any single owner name within a catalog zone (other
than the apex of the zone itself) to have more than one RR associated
with it.
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.
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
van Dijk, et al. Expires October 16, 2020 [Page 5]
Internet-Draft dns-catalog-zones April 2020
representation. A separate method of querying entries inside the
catalog zone may be made available by nameserver implementations (see
Section 6.1).
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. If a broken catalog
zone was transferred, the newly transferred catalog zone MUST be
ignored (but the older copy of the catalog zone SHOULD be left
running subject to values in SOA fields).
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 introduced into a catalog zone, a primary SHOULD first
make the new zones available for transfers before making the updated
catalog zone available for transfer, or sending NOTIFY for the
catalog zone to secondaries. Note that secondary nameservers may
attempt to transfer the catalog zone upon refresh timeout, so care
must be taken to make the member zones available before any update to
the list of member zones is visible in the catalog zone.
When zones are deleted from a catalog zone, a primary MAY delete the
member zone immediately after notifying secondaries. It is up to the
secondary nameserver to handle this condition correctly.
When the "<m-unique-N>" label of a member zone changes, 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. A simple removal followed by an addition of the member
zone would be insufficient for this purpose because it is infeasible
van Dijk, et al. Expires October 16, 2020 [Page 6]
Internet-Draft dns-catalog-zones April 2020
for secondaries to track, due to missed notifies or being offline
during the removal/addition.
6. Updating Catalog Zones
TBD: Explain updating catalog zones using DNS UPDATE.
6.1. 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.
7. Security Considerations
As catalog zones are transmitted using DNS zone transfers, it is
absolutely essential for these transfers to be protected from
unexpected modifications on the route. So, catalog zone transfers
SHOULD be authenticated using TSIG [RFC2845]. 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 [RFC2845]. 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
van Dijk, et al. Expires October 16, 2020 [Page 7]
Internet-Draft dns-catalog-zones April 2020
normally by nameservers, and their contents MUST NOT be DNSSEC-
validated.
8. IANA Considerations
This document has no IANA actions.
9. 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.
Thanks to Brian Conry, Tony Finch, Evan Hunt, Patrik Lundin, Victoria
Risk and Carsten Strettman for reviewing draft proposals and offering
comments and suggestions.
10. References
10.1. 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>.
[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>.
van Dijk, et al. Expires October 16, 2020 [Page 8]
Internet-Draft dns-catalog-zones April 2020
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, DOI 10.17487/RFC2308, March 1998,
<https://www.rfc-editor.org/info/rfc2308>.
[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>.
[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
<https://www.rfc-editor.org/info/rfc2845>.
[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>.
10.2. 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)
o draft-muks-dnsop-dns-catalog-zones-00
Initial public draft.
o 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.
o draft-muks-dnsop-dns-catalog-zones-02
Addressed some review comments by Patrik Lundin.
o draft-muks-dnsop-dns-catalog-zones-03
Revision bump.
van Dijk, et al. Expires October 16, 2020 [Page 9]
Internet-Draft dns-catalog-zones April 2020
o draft-muks-dnsop-dns-catalog-zones-04
Reordering of sections into more logical order. Separation of
multi-valued properties into their own category.
o draft-toorop-dnsop-dns-catalog-zones-00
New authors to pickup the editor pen on this draft
o draft-toorop-dnsop-dns-catalog-zones-01
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.
Authors' Addresses
Peter van Dijk
PowerDNS
Den Haag
Netherlands
Email: peter.van.dijk@powerdns.com
Libor Peltan
CZ.NIC
CZ
Email: libor.peltan@nic.cz
Ondrej Sury
Internet Systems Consortium
CZ
Email: ondrej@isc.org
Willem Toorop
NLnet Labs
Science Park 400
Amsterdam 1098 XH
Netherlands
Email: willem@nlnetlabs.nl
van Dijk, et al. Expires October 16, 2020 [Page 10]
Internet-Draft dns-catalog-zones April 2020
Leo Vandewoestijne
Netherlands
Email: leo@dns.company
van Dijk, et al. Expires October 16, 2020 [Page 11]
