YANG Types for DNS
Classes and Resource Record Types
CZ.NIC
Czech Republic
ladislav.lhotka@nic.cz
Internet Systems Consortium
Czech Republic
pspacek@isc.org
Operations and Management
DNSOP Working Group
This document introduces the YANG
module "iana-dns-class-rr-type" that contains derived types
reflecting two IANA registries: DNS CLASSes and Resource Record
(RR) TYPEs. These YANG types are intended as a minimum basis for
future data modeling work.
YANG has become a de facto standard
as a language for modeling configuration and state data, as well
as specifying management operations and asynchronous
notifications. It is reasonable to expect that the approach
based on utilizing such data models along with standard
management protocols such as NETCONF and RESTCONF can be
effectively used in DNS operations, too. In fact, several
efforts are currently underway that attempt to use NETCONF or
RESTCONF for configuring and managing
- authoritative servers
- resolvers
- zone data.
While it is possible to use the management protocols
mentioned above with ad hoc or proprietary data models, their
real potential can be realized only if there is a (completely or
partly) unified data model supported by multiple DNS software
implementations. Operators can then, for instance, run several
different DNS server implementations in parallel, and use a common
configuration and management interface and data for all of
them. Also, it becomes considerably easier to migrate to another
implementation.
Based on the previous experience from the IETF Routing Area,
it is to be expected that the development of unified data models
for DNS will be a lengthy and complicated process that will
require active cooperation and compromises from the vendors and
developers of major DNS server platforms. Nevertheless, it is
likely that any DNS-related data modeling effort will need to
use various DNS parameters and enumerations that are specified
in several IANA registries. For use with YANG, these parameters
and enumerations have to be translated into corresponding YANG
types or other structures. Such translations should be
straightforward and relatively uncontroversial.
This document provides a translation of two fundamental
DNS-related IANA registries to YANG. It contains the initial
revision of the YANG module "iana-dns-class-rr-type" that
defines derived types for the common parameters of DNS resource
records (RR): class and type. These YANG types, "dns-class" and
"rr-type", reflect the IANA registries "DNS CLASSes" and
"Resource Record (RR) TYPEs" .
contains an XSLT 1.0 stylesheet
that is intended to be used by IANA for generating the initial
revision of the "iana-dns-class-rr-type" YANG
module. Subsequently, whenever a new class or RR type is added
to the above registries, IANA will also update the
"iana-dns-class-rr-type" YANG module, following the instructions
in below.
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 when, and only when, they
appear in all capitals, as shown here.
The terminology for describing YANG data models is found in
.
The IANA document "Domain Name System (DNS) Parameters" contains altogether thirteen
registries. The YANG module "iana-dns-class-rr-type" defines
derived types corresponding to only two of the registries that
are essential for data models involving zone data, namely "DNS
CLASSes" and "Resource Record (RR) TYPEs". It is expected that
the remaining registries in , as well as other DNS-related
IANA registries, will be analogically reflected in future YANG
modules as necessary. This way, an appropriate combination of
YANG modules can be chosen depending on which YANG types are
needed for a given data modeling purpose.
The registries "DNS CLASSes" and "Resource Record (RR) TYPEs"
are transformed into YANG enumeration types "dns-class-name" and
"rr-type-name", respectively. This is the initial fragment of
the former:
typedef dns-class-name {
type enumeration {
enum IN {
value 1;
description
"Internet (IN)";
reference
"RFC 1035";
}
...
}
...
}
The other derived type, "rr-type-name", is defined
analogically.
introduced the option of specifying
a class or RR type via its assigned decimal number, as an
alternative to the mnemonic name. For example, the "IN" class
can be equivalently written as "CLASS1", and "AAAA" type can be
written as "TYPE28".
Accordingly, the derived types "dns-class" and "rr-type" are
defined in the YANG module as a union of two member types:
- 16-bit decimal integer ("uint16")
- mnemonic name belonging to the enumerations
"dns-class-name" and "rr-type-name", respectively.
For instance, the "rr-type" type is defined as follows:
typedef rr-type {
type union {
type uint16;
type rr-type-name;
}
description
"This type allows for referring to a DNS resource record type
using either the assigned mnemonic name or numeric value.";
}
As unassigned and reserved class and RR type values are not
included in the mnemonic name enumerations, they can only be specified
using their decimal values.
RFC Editor: In this section, replace all occurrences of "XXXX"
with the actual RFC number (and remove this note).
This section deals with actions and processes necessary for
IANA to undertake to maintain the "iana-dns-class-rr-type" YANG
module. This YANG module is intended to reflect the "DNS
CLASSes" and "Resource Record (RR) TYPEs" registries in . The most recent revision of the
YANG module is available from the "YANG Parameters" registry .
Upon publication of this document, the initial revision of the
"iana-dns-class-rr-type" YANG module SHALL be created by applying
the XSLT stylesheet from to the XML
version of .
IANA SHALL add this note to the "iana-dns-class-rr-type" item
of the "YANG Module Names" registry :
Classes and types of DNS resource records must not be directly
added to the "iana-dns-class-rr-type" YANG module. They must
instead be added to the "DNS CLASSes" and "Resource Record
(RR) TYPEs" registries, respectively.
When a new DNS class or RR type is added to the "DNS CLASSes"
or "Resource Record (RR) TYPEs" registry, a new "enum" statement
SHALL be added to the "dns-class-name" or "rr-type-name" type,
respectively. The assigned name defined by the "enum" statement
SHALL be the same as the mnemonic name of the new class or
type. The following substatements to the "enum" statement SHALL
be defined:
- "value":
- Use the decimal value from the registry.
- "status":
- Include only if a class or type registration has been
deprecated or obsoleted. In both cases, use the value
"obsolete" as the argument of the "status" statement.
- "description":
- Replicate the corresponding information from the registry,
namely the full name of the new DNS class, or the meaning of
the new RR type, if any.
- "reference":
- Replicate the reference(s) from the registry.
Unassigned or reserved values SHALL NOT be included in the
"dns-class-name" and "rr-type-name" enumeration types.
Each time the "iana-dns-class-rr-type" YANG module is updated, a new
"revision" statement SHALL be added before the existing
"revision" statements.
IANA SHALL add this new note to the "DNS CLASSes" and
"Resource Record (RR) TYPEs" registries:
When this registry is modified, the YANG module
"iana-dns-class-rr-type" must be updated as defined in RFC
XXXX.
The "Reference" text in the "DNS CLASSes" registry SHALL be
updated as follows:
OLD:
[RFC6895]
NEW:
[RFC6895][RFCXXXX]
The "Reference" text in the "Resource Record (RR) TYPEs"
registry SHALL be updated as follows:
OLD:
[RFC6895][RFC1035]
NEW:
[RFC6895][RFC1035][RFCXXXX]
This document registers a URI in the "IETF XML Registry"
. The following registration has been
made:
URI: urn:ietf:params:xml:ns:yang:iana-dns-class-rr-type
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
This document registers a YANG module in the "YANG Module
Names" registry . The following
registration has been made:
name: iana-dns-class-rr-type
namespace: urn:ietf:params:xml:ns:yang:iana-dns-class-rr-type
prefix: dnsct
reference: RFC XXXX
This documents translates two IANA registries into YANG data
types and otherwise introduces no technology or
protocol. Consequently, there are no security issues to be
considered for this document.
Domain Name System (DNS) Parameters
Internet Assigned Numbers Authority
YANG Parameters
Internet Assigned Numbers Authority
Key words for use in RFCs to Indicate Requirement Levels
In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.
The IETF XML Registry
This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas.
YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)
YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK]
The YANG 1.1 Data Modeling Language
YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF).
Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words
RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.
XSL Transformations (XSLT) Version 1.0
Handling of Unknown DNS Resource Record (RR) Types
Extending the Domain Name System (DNS) with new Resource Record (RR) types currently requires changes to name server software. This document specifies the changes necessary to allow future DNS implementations to handle new RR types transparently. [STANDARDS-TRACK]
RFC Editor: In this section, replace all occurrences of "XXXX"
with the actual RFC number (and remove this note).
This appendix contains an XSLT 1.0 stylesheet that is intended to be used for
generating the initial revision of the "iana-dns-class-rr-type"
YANG module. This is achieved by applying the stylesheet to the
XML version of the IANA registry "Domain Name System (DNS)
Parameters" that was
current at the time when this document was published.
Using the ubiquitous xsltproc tool, the YANG module text can
be generated with this command:
$ xsltproc iana-dns-class-rr-type.xsl dns-parameters.xml
<?xml version="1.0" standalone="yes"?>
<stylesheet xmlns="http://www.w3.org/1999/XSL/Transform"
xmlns:iana="http://www.iana.org/assignments"
version="1.0">
<output method="text"/>
<strip-space elements="*"/>
<variable name="dq">"</variable>
<variable name="sq">'</variable>
<variable name="lf">
</variable>
<variable name="module-intro">
<text>module iana-dns-class-rr-type {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:iana-dns-class-rr-type";
prefix dnsct;
organization
"Internet Assigned Numbers Authority (IANA)";
contact
" Internet Assigned Numbers Authority
Postal: ICANN
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292
Tel: +1 310 823 9358
<mailto:iana@iana.org>";
description
"This YANG module translates IANA registries 'DNS CLASSes' and
'Resource Record (RR) TYPEs' to YANG derived types.
Copyright (c) 2020 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This initial version of this YANG module was generated from
the corresponding IANA registries using a XSLT stylesheet
from Appendix A of RFC XXXX
(https://tools.ietf.org/html/rfcXXXX); see the RFC itself for
full legal notices.";
reference
"IANA 'Domain Name System (DNS) Parameters' registry
https://www.iana.org/assignments/dns-parameters";</text>
<text>

</text>
</variable>
<template name="enum">
<param name="id"/>
<value-of select="concat(' enum ', $id)"/>
<text> {
 value </text>
<value-of select="concat(iana:value, ';
')"/>
<if test="contains(iana:description, 'OBSOLETE')">
<text> status obsolete;
</text>
</if>
<apply-templates select="iana:description"/>
<variable name="xrefs" select="iana:xref[@type!='note']"/>
<if test="$xrefs">
<text> reference
 "</text>
<if test="count($xrefs)>1">- </if>
<apply-templates select="iana:xref[@type!='note']"/>
</if>
<text> }
</text>
</template>
<template match="/">
<value-of select="$module-intro"/>
<apply-templates select="iana:registry[@id='dns-parameters']"/>
<text>}
</text>
</template>
<template match="iana:registry[@id='dns-parameters']">
<apply-templates select="iana:updated"/>
<apply-templates
select="iana:registry[@id='dns-parameters-2']"/>
<apply-templates
select="iana:registry[@id='dns-parameters-4']"/>
</template>
<template match="iana:updated">
<value-of select="concat(' revision ', ., ' {')"/>
<text>
description
"Initial revision.";
reference
"RFC XXXX: YANG Types for DNS Classes and Resource Record
Types";
}
/* Typedefs */

</text>
</template>
<template match="iana:registry[@id='dns-parameters-2']">
<text> typedef dns-class-name {
</text>
<text> type enumeration {
</text>
<apply-templates
select="iana:record[not(iana:description='Unassigned' or
starts-with(iana:description,'Reserved'))]"
mode="class"/>
<text> }
description
"This enumeration type defines mnemonic names and corresponding
numeric values of DNS classes.";
reference
"RFC 6895: Domain Name System (DNS) IANA Considerations";
}
typedef dns-class {
type union {
type uint16;
type dns-class-name;
}
description
"This type allows for referring to a DNS class using either the
assigned mnemonic name or numeric value.";
}

</text>
</template>
<template match="iana:registry[@id='dns-parameters-4']">
<text> typedef rr-type-name {
</text>
<text> type enumeration {
</text>
<apply-templates
select="iana:record[iana:type!='Unassigned' and
iana:type!='Private use' and iana:type!='Reserved']"
mode="rr-type"/>
<text> }
description
"This enumeration type defines mnemonic names and corresponding
numeric values of DNS resource record types.";
reference
"- RFC 6895: Domain Name System (DNS) IANA Considerations
- RFC 1035: Domain Names - Implementation and Specification";
}
typedef rr-type {
type union {
type uint16;
type rr-type-name;
}
description
"This type allows for referring to a DNS resource record type
using either the assigned mnemonic name or numeric value.";
}
</text>
</template>
<template match="iana:record" mode="class">
<call-template name="enum">
<with-param name="id">
<choose>
<when test="contains(iana:description,'(')">
<value-of select="substring-before(substring-after(
iana:description, '('), ')')"/>
</when>
<otherwise>
<value-of
select="substring-after(iana:description, ' ')"/>
</otherwise>
</choose>
</with-param>
</call-template>
</template>
<template match="iana:record" mode="rr-type">
<call-template name="enum">
<with-param name="id" select="iana:type"/>
</call-template>
</template>
<template match="iana:description">
<text> description
 </text>
<value-of select="concat($dq, ., $dq, ';
')"/>
</template>
<template match="iana:xref">
<choose>
<when test="@type='rfc'">
<value-of
select="concat('RFC ', substring-after(@data, 'rfc'))"/>
</when>
<when test="@type='person'">
<apply-templates
select="/iana:registry/iana:people/iana:person[
@id=current()/@data]"/>
</when>
<when test="@type='text'">
<value-of select="translate(., $dq, $sq)"/>
</when>
<otherwise>
<value-of select="@data"/>
</otherwise>
</choose>
<choose>
<when test="position()=last()">
<text>";
</text>
</when>
<otherwise>
<text>
 - </text>
</otherwise>
</choose>
</template>
<template match="iana:person">
<value-of select="concat(iana:name, ' <', iana:uri, '>')"/>
</template>
</stylesheet>