YANG Types for DNS Classes and Resource Record TypesCZ.NICCzech Republicladislav.lhotka@nic.czInternet Systems ConsortiumCzech Republicpspacek@isc.org
Operations and Management
DNSOP Working GroupIANA registryDNA ParametersThis document introduces the YANG
module "iana-dns-class-rr-type", which contains derived types
reflecting two IANA registries: DNS CLASSes and Resource Record
(RR) TYPEs. These YANG types are intended as the minimum basis for
future data modeling work.Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
.
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
() in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
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warranty as described in the Simplified BSD License.
Table of Contents
. Introduction
. Terminology
. YANG Design Considerations
. IANA Considerations
. URI Registrations
. YANG Module Registrations
. Security Considerations
. References
. Normative References
. Informative References
. XSLT Stylesheet
Authors' Addresses
IntroductionYANG 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, and
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
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 compromise 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
version of the YANG module "iana-dns-class-rr-type", which
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
version 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.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
when, and only when, they appear in all capitals, as shown here.
The terminology for describing YANG data models can be found
in . DNS terminology used in this
document can be found in and .YANG Design ConsiderationsAt the time of writing, the "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 analogously 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
similarly. 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 reference 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.IANA ConsiderationsThis 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 version of the
YANG module is available from the "YANG Parameters" registry .With the publication of this document, IANA has created and posted the initial version
of the "iana-dns-class-rr-type" YANG module by applying the XSLT stylesheet from
to the XML version of .IANA has added 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. IANA "deprecated" maps to YANG status
"deprecated", and IANA "obsolete" maps to YANG status "obsolete".
"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 has added this 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 [RFC9108].
The "Reference" text in the "DNS CLASSes" registry has been
updated as follows:
OLD:
[RFC6895]
NEW:
[RFC6895][RFC9108]
The "Reference" text in the "Resource Record (RR) TYPEs"
registry has been updated as follows:
OLD:
[RFC6895][RFC1035]
NEW:
[RFC6895][RFC1035][RFC9108]
URI RegistrationsThis document registers a URI in the "IETF XML Registry"
. The following registration has been
made:
Security ConsiderationsThis document translates two IANA registries into YANG data
types and otherwise introduces no technology or
protocol. The definitions themselves have no security impact on
the Internet, but their use in concrete YANG modules might
have. The security considerations spelled out in the YANG
specification apply to this document
as well.ReferencesNormative ReferencesDomain Name System (DNS) ParametersIANAYANG ParametersIANAKey words for use in RFCs to Indicate Requirement LevelsIn 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 RegistryThis 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 LanguageYANG 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 WordsRFC 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 1.0Informative ReferencesDomain names - implementation and specificationThis RFC is the revised specification of the protocol and format used in the implementation of the Domain Name System. It obsoletes RFC-883. This memo documents the details of the domain name client - server communication.Handling of Unknown DNS Resource Record (RR) TypesExtending 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]Network Configuration Protocol (NETCONF)The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK]RESTCONF ProtocolThis document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF).DNS TerminologyThe Domain Name System (DNS) is defined in literally dozens of different RFCs. The terminology used by implementers and developers of DNS protocols, and by operators of DNS systems, has sometimes changed in the decades since the DNS was first defined. This document gives current definitions for many of the terms used in the DNS in a single document.This document obsoletes RFC 7719 and updates RFC 2308.XSLT StylesheetThis appendix contains an XSLT 1.0 stylesheet that is to be used to
generate 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 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="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
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094
Tel: +1 424 254 5300
<mailto:iana@iana.org>";
description
"This YANG module translates IANA registries 'DNS CLASSes' and
'Resource Record (RR) TYPEs' to YANG-derived types.
Copyright (c) 2021 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 version of this YANG module was generated from
the corresponding IANA registries using an XSLT stylesheet
from Appendix A of RFC 9108
(https://www.rfc-editor.org/info/rfc9108); 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 9108: 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 reference 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 reference 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>
Authors' AddressesCZ.NICCzech Republicladislav.lhotka@nic.czInternet Systems ConsortiumCzech Republicpspacek@isc.org