DNS catalog zonesInternet Systems Consortium950 Charter StreetRedwood City94063CAUSmuks@mukund.orghttp://www.isc.org/Internet Systems Consortium950 Charter StreetRedwood City94063CAUSstephen@isc.orghttp://www.isc.org/Internet Systems Consortium950 Charter StreetRedwood City94063CAUSray@isc.orghttp://www.isc.org/Internet Systems Consortium950 Charter StreetRedwood City94063CAUSwpk@isc.orghttp://www.isc.org/
Operations and Management Area
Internet Engineering Task ForceThis document describes a method for automatic zone catalog
provisioning and synchronization among DNS primary and secondary
nameservers by storing and transferring the catalogs as regular
DNS zones.DNS nameservers implement AXFR and IXFR for zone data
synchronization among a zone's primary and secondary nameservers,
but the list of zones served by the primary (called a catalog in
) is not automatically synchronized. The
administrator of a DNS nameserver farm has to synchronize such
zone catalogs among primaries and their secondary nameservers
manually or via an external application layer. This can be
inconvenient, error-prone and dependent on the nameserver
implementation.A method for automatic zone catalog provisioning and
synchronization is useful, so that the zone catalog can be
maintained in a reference location by an administrator, similar to
zone data.This document describes one such method, in which the catalog
is represented as a regular DNS zone called a "catalog zone", and
transferred using DNS zone transfers. The representation of
catalogs within DNS zones is specified and nameserver requirements
are listed so that DNS implementations can support catalog
zones.The contents and representation of catalog zones are described
in . Nameserver behavior is
described in . A glossary of some terms
used in this memo is provided in .The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in .A catalog zone is a specially crafted DNS zone that contains,
as DNS zone data, a list of DNS zones called member zones,
associated template zone configuration common to all its member
zones, and zone-specific configuration that applies to a
respective zone. An implementation of catalog zones MAY allow
catalog zones to include other catalog zones, but template zone
configuration present in a catalog zone only applies to its
immediate member zones. A catalog zone is meant to be used to
provision DNS catalogs to secondary nameservers via zone
transfers, for the purpose of setting up member zones to be
served from these secondary nameservers.A catalog zone uses some RR TYPEs such as PTR with alternate
semantics for its purposes. Although this may be controversial,
the situation is similar to other similar zone-based
representations such as response-policy zones . A design criterion of catalog zones is that none of the RR
TYPEs used therein may incur any additional section processing
during DNS QUERY.Member zones' configuration is specified as a map of zone
properties, represented as a subtree of a node in the domain name space inside a catalog
zone. This is described in . Each zone
property has a name and an associated value of a specific data
type. Zone property value data types are described in . A list of permitted zone property names
and their data types is given in .TBD: Transitive catalogsA catalog zone contains various resource records (RRs). They
have NAME, TYPE, CLASS, TTL, RDLENGTH and RDATA as fields .The NAME field contains the owner name of the respective
RR. As with all DNS zones, the owner name must be a child of the
catalog zone name.The TYPE field depends on the type of catalog zone property
value being represented. describes
how various zone property value types are represented.The CLASS field of the RR MUST be set to IN(1) . This is because some RR TYPEs such as APL
used by catalog zones are defined only for the IN CLASS.The TTL field's value is not specially defined by this
memo. Catalog zones are for nameserver management only and are
not intended for general querying. Operators should use
whatever value seems convenient for any management applications
that may query the catalog zone.The RDLENGTH field contains the length of the RDATA
field.The content of the RDATA field depends on the type of catalog
zone property value being represented. describes how various zone property value types are
represented.Similar to any other DNS zone, a catalog zone would be
expected to have a syntactically correct SOA record and one or
more NS records at its apex.The SOA record's SERIAL, REFRESH, RETRY and EXPIRE fields
are used during zone transfer. A
catalog zone's SOA SERIAL field SHOULD increase when an update
is made to the catalog zone's contents as per serial number
arithmetic defined in . Otherwise,
secondary nameservers may not notice updates to the catalog
zone's contents.The SOA record's MINIMUM field's value is not specially
defined by this memo. Although they are regular DNS zones,
catalog zones contain only information for the management of a
set of nameservers. For this reason, operators may want to
limit the systems able to query these zones.As catalog zones do not participate in the DNS, NS records at
the apex are not used but they are still required so that
catalog zones are syntactically correct DNS zones. No parent
delegation for the catalog zone is required. Any valid DNS name
can be used in the NSDNAME field of such NS records and they MUST be ignored. A single NS RR
with an NSDNAME field containing the absolute name "invalid."
is recommended .Member zones' configuration is specified as a map of zone
properties, represented as a subtree of a node in the domain name space inside a catalog
zone. A subtree of child nodes is used for a nested map,
occuping another label level. A map element's key (property
name) is represented in the label at that level. For example, if
a catalog zone is named "catalog1.example.org." and contains a
property with name "prop0", the corresponding owner name of the
node representing that property is
"prop0.catalog1.example.org."Zone property names are case-insensitive. Each zone property
may use only one data type for its values. A list of permitted
zone property names and their data types is given in .Many properties are single-valued, but some properties can be
collections with thousands of values. An example is the list of
member zones within a catalog zone, which can be larger than any
single RDATA instance can allow. Multiple RRs are used to
represent such properties.TBD: Currently a hashing method in owner names is used to
split the elements of such properties with multiple RRs into
individual RRsets, one per RR. This needs to be revisited as
IXFR and DNS UPDATE both allow individual RRs within an RRset to
be modified. The hashing method used is described in the
appropriate property value data types in .A property with a string value is specified using a single
TXT RR with owner name set to the
name of the property as a sub-domain of the catalog zone name,
and RDATA set to the property value.For example, if a catalog zone is named
"catalog1.example.org." and contains a property "prop0" with
string value "Example", the corresponding RR would appear as
follows:
prop0.catalog1.example.org. 3600 IN TXT "Example"
Here, "prop0" can contain multiple TXT RRs at that node of
the domain name space . The single
string property SHOULD be checked by the implementation.A property with a boolean value is specified using a single
TXT RR with owner name set to the name of the property as a
sub-domain of the catalog zone name, and RDATA set to "true"
for true condition and "false" for false condition. The RDATA
is case-insensitive.For example, if a catalog zone is named
"catalog1.example.org." and contains a property "active" with
boolean value false, the corresponding RR would appear as
follows:
active.catalog1.example.org. 3600 IN TXT "false"
Here, "active" can contain multiple TXT RRs at that node of
the domain name space . The single
boolean property SHOULD be checked by the implementation.A property with an integer value is specified using a
single TXT RR for signed integers or unsigned integers, with
owner name set to the name of the property as a sub-domain of
the catalog zone name, and RDATA set to the property
value.A signed integer's TXT RDATA uses the representation of an
unsuffixed "integer constant" as defined in the C programming
language standard (of the type
matching a 64-bit signed integer on that platform), with an
optional minus prefix. The representation MUST be specified
using a single <character-string> .An unsigned integer's TXT RDATA uses the representation of
an unsuffixed "integer constant" as defined in the C
programming language standard
(of the type matching a 64-bit unsigned integer on that
platform). The representation MUST be specified using a single
<character-string> .For example, if a catalog zone is named
"catalog1.example.org." and contains a property "min-ttl" with
unsigned integer value 300, the corresponding RR would appear
as follows:
min-ttl.catalog1.example.org. 3600 IN TXT "300"
Here, "min-ttl" can contain multiple TXT RRs at that node
of the domain name space . The single
integer property SHOULD be checked by the implementation.A property with a floating-point value is specified using a
single TXT RR with owner name set to the name of the property
as a sub-domain of the catalog zone name, and RDATA set to the
property value.A floating-point value's TXT RDATA uses the representation
of an unsuffixed "floating constant" as defined in the C
programming language standard . The representation MUST be specified using a single
<character-string> .For example, if a catalog zone is named
"catalog1.example.org." and contains a property "decay-rate"
with value 0.15, the corresponding RR may appear as
follows:
decay-rate.catalog1.example.org. 3600 IN TXT "15e-2"
Here, "decay-rate" can contain multiple TXT RRs at that
node of the domain name space . The
single floating-point property SHOULD be checked by the
implementation.A property with a single domain name as value is specified
using a PTR RR with owner name set
to the name of the property as a sub-domain of the catalog
zone name, and RDATA set to the property value.For example, if a catalog zone is named
"catalog1.example.org." and contains a property "prop1" with
value "val1.example.com.", the corresponding RR would appear
as follows:
prop1.catalog1.example.org. 3600 IN PTR val1.example.com.
Here, "prop1" can contain multiple PTR RRs at that node of
the domain name space . The single
domain name property SHOULD be checked by the
implementation.Let N be an absolute name formed by concatenating the RDATA
hash (see ), the name of the
property, and the catalog zone name in that order, such that N
is a unique owner name in the catalog zone.Then, a property containing an unordered list of domain
names as value is specified using multiple PTR RRs with owner name set to N, and each RR's
RDATA set to each domain name in the list of the property's
value respectively.For example, if a catalog zone is named
"catalog1.example.org." and contains a property "prop2" with
its value being an unordered list of two names
"a.example.com." and "b.example.com.", the corresponding RRs
would appear as follows:
<hash1>.prop2.catalog1.example.org. 3600 IN PTR a.example.com.
<hash2>.prop2.catalog1.example.org. 3600 IN PTR b.example.com.
Here, "prop2"'s subtree child nodes (in the domain name
space ) can contain multiple PTR RRs
at each child. For example, <hash1>.prop2 may contain
multiple PTR RRs at that node. The single domain name property
SHOULD be checked by the implementation.A property with a list of network addresses as value is
specified using a single APL RR with
owner name set to the name of the property as a sub-domain of
the catalog zone name, and RDATA set to the property value. In
its presentation format, the "!" character (corresponding to
the negation flag) is used to negate a network element. The
exact meaning of a negated network element is left to be
described by the property that APL is used for. Note that the
AFL RR TYPE is defined only for the IN(1) RR CLASS.For example, if a catalog zone is named
"catalog1.example.org." and contains a property "allow-query"
with value [192.0.2.0/24, 198.51.100.0/24] as the list of
networks, the corresponding RR would appear as follows:
allow-query.catalog1.example.org. 3600 IN APL (
1:192.0.2.0/24 2:2001:db8::/32)
Here, "allow-query" can contain multiple APL RRs at that
node of the domain name space . The
single APL RR property SHOULD be checked by the
implementation.A single host address is represented using the list of
network addresses data type (see ) with a suitable network and prefix to result in a single
host address.Comments may be added anywhere in a catalog zone using a
scheme such as NOTE RRs . This memo does not depend on NOTE RRs and it is only
suggested here as an informative reference.The catalog zone schema version is specified by an unsigned
integer property with the property name "version". All catalog
zones MUST have this property present. Primary and secondary
nameservers MUST NOT use catalog zones with an unexpected value
value in this property, but they may be transferred as ordinary
zones. For this memo, the "version" property value MUST be set
to 1.For example, if a catalog zone is named
"catalog1.example.org.", the corresponding RR MUST look as
follows:
version.catalog1.example.org. 3600 IN TXT "1"
Here, "version" can contain multiple TXT RRs at that node of
the domain name space . The single TXT
RR property SHOULD be checked by the implementation.The list of member zones are specified as an unordered list
(see ) of domain names under the
owner name "zones" where "zones" is a sub-domain of the catalog
zone.The names of member zones are represented on the RDATA side
instead of as part of owner names so that all valid domain names
may be represented regardless of their length. For example, if a catalog zone is named
"catalog1.example.org." and lists 3 zones "example.com.",
"example.net." and "example.org.", the RRs would appear as
follows:
<hash>.zones.catalog1.example.org. 3600 IN PTR example.com.
<hash>.zones.catalog1.example.org. 3600 IN PTR example.net.
<hash>.zones.catalog1.example.org. 3600 IN PTR example.org.
TBD: Prepare a list of zone configuration properties that are
common to DNS implementations. This is so that a company may
manage a catalog zone using a Windows DNS server as the primary,
and a secondary nameserver hosting service may pick up the
common properties and may use a different nameserver
implementation such as BIND or NSD on a POSIX operating system
to serve it.TBD: We may specify that unrecognized zone property names
must be ignored, or that nameserver specific properties must be
specified using the "x-" prefix similar to MIME type naming.TBD: Any list of zone properties is ideally maintained as a
registry rather than within this memo.TBD.TBD.Member zones in a catalog zone share template zone
configuration that is common to all member zones in that
catalog. This section describes the syntax that can be used to
specify zone properties specific to single member zones.Let N be an absolute name formed by concatenating the member
zone name hash as a label (see ),
the label "zones", and the catalog zone name in that order, such
that N is a unique owner name in the catalog zone.Zone properties specific to a particular member zone are
specified under the respective sub-domain N.For example, if a catalog zone is named
"catalog1.example.org." and a member zone "example.com."
contains a property "prop0" with string (see ) value "Example", the corresponding RR
would appear as follows:
prop0.<m-hash>.zones.catalog1.example.org. 3600 IN TXT "Example"
As another example, if a catalog zone is named
"cat1.example.org." and a member zone "example.com." contains a
property "prop2" with its value being an unordered list (see
) of two domain names
"a.example.com." and "b.example.com.", the corresponding RRs
would appear as follows:
(<hash>.prop2.<m-hash>.zones.cat1.example.org.
3600 IN PTR a.example.com.)
(<hash>.prop2.<m-hash>.zones.cat1.example.org.
3600 IN PTR b.example.com.)
$ORIGIN catalog.example.org.
@ IN SOA . . 1 3600 3600 86400 3600
IN NS invalid.
version IN TXT "1"
(5960775ba382e7a4e09263fc06e7c00569b6a05c.zones
IN PTR domain1.example.com.)
TBD: Explain nameserver behavior in a more detailed way
here. It is under-specified.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 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 ).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.TBD: Transitive primary-secondary relationshipsTBD: Explain updating catalog zones using DNS UPDATE.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 would want to look at data inside a catalog
zone. Typical queries may 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
syntax of catalog zones, it may not be possible to perform these
queries intuitively, or in some cases, at all, using DNS
QUERY. The list of member zones may not fit in a single DNS
message. The set of present properties for a zone cannot be
queried using a single DNS QUERY.Implementations are advised to provide a tool that uses
either the output of AXFR or an out-of-band method to perform
queries on catalog zones.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, it is a requirement
that catalog zone transfers SHOULD be authenticated using TSIG . 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.DNS UPDATE to catalog zones similarly
SHOULD be authenticated using TSIG.Zone transfers of member zones SHOULD similarly be
authenticated using TSIG . 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.This document has no IANA actions.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.We later discovered that Paul Vixie's earlier 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, Evan Hunt, and Victoria Risk for
reviewing draft proposals and providing support, comments and
suggestions.Thanks to BIND users who reviewed draft proposals and offered
comments and suggestions.Secure Hash StandardNational Institute of Standards and TechnologyDNS Response Policy Zones (DNS RPZ)Federated Domain Name Service Using DNS MetazonesA DNS zone containing a DNS
catalog, that is, a list of DNS zones and associated template
zone configuration common to all member zones.A DNS zone whose configuration is
published inside a catalog zone.An authoritative server
configured to be the source of zone transfer to one or more
[secondary] nameservers. Also see .The hexadecimal format 40-digit
SHA-1 digest, of the RDATA
of the corresponding RR. For RDATA containing DNS names, no
name compression must be in use, i.e., the name must be in its
full expanded wire data format when it is hashed.The hexadecimal format
40-digit SHA-1 digest, of a
zone name in uncompressed wire format.An authoritative server
which uses zone transfer to retrieve the zone. Also see .A configuration parameter of a
zone, sometimes also called a zone option.Config options
We want catalog zones to be adopted by multiple DNS
implementations. Towards this, we have to generalize zone
config options and adopt a minimal set that we can expect
most implementations to support.
Catalog zone and member zones on different primary
nameservers
Will it be possible to setup a catalog zone on one nameserver as
primary, and allow its member zones to be served by different
primary namesservers?
Transitive relationships
For a catalog zone, a secondary nameserver may be a primary
nameserver to a different set of nameservers in a nameserver
farm. In these transitive relationships, zone configuration
options (such as also-notify and allow-transfer) may differ
based on the location of the primary in the hierarchy. It may
not be possible to specify this within a catalog zone.
Templates
Are support for config and zone data templates useful at this
level? They would add complexity across implementations. If
added, it would be better to restrict templates at the primary
nameserver and let the secondary receive regular expanded zones.
Overriding controls
A way to override zone config options (as prescribed by the
catalog zones) on secondary nameservers was requested. As this
would be configured outside catalog zones, it may be better to
leave this to implementations.
Use of hashing
Should use of hashing be completely removed, and replaced with
the same common owner name for all property RRs in a collection?
Both IXFR and DNS UPDATE allow changing individual RRs in a
RRset.
Choice of hash function
Should a different faster hash function be chosen to replace
SHA-1 when computing catalog member zone name hashes?
Overriding existing RR types
This memo currently overrides only the PTR RR TYPE's meaning as
PTR is currently used for reverse lookups. But such overridden
use seems like a non-issue as PTR is defined to be a pointer to
any name in .
APL limits
APL can only support as many networks as can fit in its
RDATA. Though a very large number of networks can be listed in a
single RDATA field, it is still limited in size. Will this
limitation become a problem for any users?
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.