Network Working Group C. Hopps
Internet-Draft L. Berger
Updates: RFC8407 (if approved) LabN Consulting, L.L.C.
Intended status: Standards Track D. Bogdanovic
Expires: August 19, 2019 Volta Networks
February 15, 2019
YANG Module Tags
draft-ietf-netmod-module-tags-05
Abstract
This document provides for the association of tags with YANG modules.
The expectation is for such tags to be used to help classify and
organize modules. A method for defining, reading and writing a
modules tags is provided. Tags may be standardized and assigned
during module definition; assigned by implementations; or dynamically
defined and set by users. This document provides guidance to future
model writers and, as such, this document updates [RFC8407].
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 August 19, 2019.
Copyright Notice
Copyright (c) 2019 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 and restrictions with respect
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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
1.1. Some possible use cases of YANG module tags . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
3. Tag Values . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. IETF Standard Tags . . . . . . . . . . . . . . . . . . . 4
3.2. Vendor Tags . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. User Tags . . . . . . . . . . . . . . . . . . . . . . . . 4
3.4. Reserved Tags . . . . . . . . . . . . . . . . . . . . . . 4
4. Tag Management . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Module Definition Association . . . . . . . . . . . . . . 5
4.2. Implementation Association . . . . . . . . . . . . . . . 5
4.3. Administrative Tagging . . . . . . . . . . . . . . . . . 5
5. Tags Module Structure . . . . . . . . . . . . . . . . . . . . 5
5.1. Tags Module Tree . . . . . . . . . . . . . . . . . . . . 5
5.2. Tags Module . . . . . . . . . . . . . . . . . . . . . . . 5
6. Other Classifications . . . . . . . . . . . . . . . . . . . . 8
7. Guidelines to Model Writers . . . . . . . . . . . . . . . . . 8
7.1. Define Standard Tags . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8.1. YANG Module Tag Prefix Registry . . . . . . . . . . . . . 9
8.2. YANG Module IETF Tag Registry . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11
Appendix B. Example . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
The use of tags for classification and organization is fairly
ubiquitous not only within IETF protocols, but in the internet itself
(e.g., #hashtags). One benefit of using tags for organization over a
rigid structure is that it is more flexible and can more easily adapt
over time as technologies evolve. Tags can be usefully standardized,
but they can also serve as a non-standardized mechanism available for
users to define themselves. This document provides a mechanism to
define tags and associate them with YANG modules in a flexible
manner. In particular, tags may be standardized as well as assigned
during module definition; assigned by implementations; or dynamically
defined and set by users.
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This document defines a YANG module [RFC7950] which provides a list
of module entries to allow for adding or removing of tags as well as
viewing the set of tags associated with a module.
This document defines an extension statement to be used to indicate
tags that SHOULD be added by the module implementation automatically
(i.e., outside of configuration).
This document also defines an IANA registry for tag prefixes as well
as a set of globally assigned tags.
Section 7 provides guidelines for authors of YANG data models. This
document updates [RFC8407].
The YANG data model in this document conforms to the Network
Management Datastore Architecture defined in [RFC8342].
1.1. Some possible use cases of YANG module tags
During this documents progression there were requests for example
uses of module tags. The following are a few example use cases for
tags. This list is certainly not exhaustive.
One example use of tags would be to help filter different discrete
categories of YANG modules supported by a device. E.g., if modules
are suitably tagged, then an XPath query can be used to list all of
the vendor modules supported by a device.
Tags can also be used to help coordination when multiple semi-
independent clients are interacting with the same devices. E.g., one
management client could mark that some modules should not be used
because they have not been verified to behave correctly, so that
other management clients avoid querying the data associated with
those modules.
Tag classification is useful for users searching module repositories
(e.g. YANG catalog). A query restricted to the 'ietf:routing'
module tag could be used to return only the IETF YANG modules
associated with routing. Without tags, a user would need to know the
name of all the IETF routing protocol YANG modules.
Future management protocol extensions could allow for filtering
queries of configuration or operational state on a server based on
tags. E.g., return all operational state related to system-
management.
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2. Conventions Used in This Document
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
[RFC2119] [RFC8174] when, and only when, they appear in all capitals,
as shown here.
3. Tag Values
All tags SHOULD begin with a prefix indicating who owns their
definition. An IANA registry is used to support standardizing tag
prefixes. Currently 3 prefixes are defined with all others reserved.
No further structure is imposed by this document on the value
following the standard prefix, and the value can contain any yang
type 'string' characters except carriage-returns, newlines and tabs.
3.1. IETF Standard Tags
An IETF standard tag is a tag that has the prefix "ietf:". All IETF
standard tags are registered with IANA in a registry defined later in
this document.
3.2. Vendor Tags
A vendor tag is a tag that has the prefix "vendor:". These tags are
defined by the vendor that implements the module, and are not
standardized; however, it is RECOMMENDED that the vendor include
extra identification in the tag to avoid collisions such as using the
enterpise or organization name follwing the "vendor:" prefix (e.g.,
vendor:example.com:vendor-defined-classifier).
3.3. User Tags
A user tag is any tag that has the prefix "user:". These tags are
defined by the user/administrator and will never be standardized.
3.4. Reserved Tags
Any tag not starting with the prefix "ietf:", "vendor:" or "user:" is
reserved for future standardization.
4. Tag Management
Tags can become associated with a module in a number of ways. Tags
may be defined and associated at module design time, at
implementation time, or via user administrative control. As the main
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consumer of tags are users, users may also remove any tag, no matter
how the tag became associated with a module.
4.1. Module Definition Association
A module definition can indicate a set of tags to be added by the
module implementer. These design time tags are indicated using the
module-tag extension statement. If the module definition is IETF
standards track, the tags MUST also be IETF standard tags
(Section 3.1). Thus, new modules can drive the addition of new
standard tags to the IANA registry, and the IANA registry can serve
as a check against duplication.
4.2. Implementation Association
An implementation MAY include additional tags associated with a
module. These tags may be standard or vendor specific tags.
4.3. Administrative Tagging
Tags of any kind can be assigned and removed using normal
configuration mechanisms.
5. Tags Module Structure
5.1. Tags Module Tree
The tree associated with the "ietf-module-tags" module follows. The
meaning of the symbols can be found in [RFC8340].
module: ietf-module-tags
+--rw module-tags
+--rw module* [name]
+--rw name yang:yang-identifier
+--rw tag* tag
+--rw masked-tag* tag
5.2. Tags Module
<CODE BEGINS> file "ietf-module-tags@2019-02-15.yang"
module ietf-module-tags {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-module-tags";
prefix tags;
import ietf-yang-types {
prefix yang;
}
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organization
"IETF NetMod Working Group (NetMod)";
contact
"NetMod Working Group - <netmod@ietf.org>";
// RFC Ed.: replace XXXX with actual RFC number and
// remove this note.
description
"This module describes a mechanism associating tags with YANG
modules. Tags may be IANA assigned or privately defined.
Copyright (c) 2018 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).
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.
This version of this YANG module is part of RFC XXXX
(https://tools.ietf.org/html/rfcXXXX); see the RFC itself for
full legal notices.";
// RFC Ed.: update the date below with the date of RFC publication
// and RFC number and remove this note.
revision 2018-10-17 {
description
"Initial revision.";
reference "RFC XXXX: YANG Module Tags";
}
typedef tag {
type string {
length "1..max";
pattern '[a-zA-Z_][a-zA-Z0-9\-_]*:[\S ]+';
}
description
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"A tag value is composed of a standard prefix followed by any
type 'string' value that does not include carriage return,
newline or tab characters.";
}
extension module-tag {
argument tag;
description
"The argument 'tag' is of type 'tag'. This extension statement
is used by module authors to indicate the tags that SHOULD be
added automatically by the system. As such the origin of the
value for the pre-defined tags should be set to 'system'.";
}
container module-tags {
description
"Contains the list of modules and their associated tags";
list module {
key "name";
description
"A list of modules and their associated tags";
leaf name {
type yang:yang-identifier;
mandatory true;
description
"The YANG module name.";
}
leaf-list tag {
type tag;
description
"Tags associated with the module. See the IANA 'YANG Module
Tag Prefix' registry for reserved prefixes and the IANA
'YANG Module IETF Tag' registry for IETF standard tags.
The 'operational' state [RFC8342] view of this list is
constructed using the following steps:
1) System tags (i.e., tags of 'system' origin) are added.
2) User configured tags (i.e., tags of 'intended' origin)
are added.
3) Any tag that is equal to a masked-tag is removed.";
}
leaf-list masked-tag {
type tag;
description
"The list of tags that should not be associated with this
module. The user can remove (mask) tags from the
operational state datastore [RFC8342] by adding them to
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this list. It is not an error to add tags to this list
that are not associated with the module, but they have no
operational effect.";
}
}
}
}
<CODE ENDS>
6. Other Classifications
It is worth noting that a different YANG module classification
document exists [RFC8199]. That document only classifies modules in
a logical manner and does not define tagging or any other mechanisms.
It divides YANG modules into two categories (service or element) and
then into one of three origins: standard, vendor or user. It does
provide a good way to discuss and identify modules in general. This
document defines standard tags to support [RFC8199] style
classification.
7. Guidelines to Model Writers
This section updates [RFC8407].
7.1. Define Standard Tags
A module MAY indicate, using module-tag extension statements, a set
of tags that are to be automatically associated with it (i.e., not
added through configuration).
module example-module {
...
import module-tags { prefix tags; }
tags:module-tag "ietf:some-new-tag";
tags:module-tag "ietf:some-other-tag";
...
}
The module writer can use existing standard tags, or use new tags
defined in the model definition, as appropriate. For standardized
modules new tags MUST be assigned in the IANA registry defined below,
see Section 8.2 below.
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8. IANA Considerations
8.1. YANG Module Tag Prefix Registry
This registry allocates tag prefixes. All YANG module tags SHOULD
begin with one of the prefixes in this registry.
The allocation policy for this registry is Specification Required
[RFC5226].
The initial values for this registry are as follows.
prefix description
-------- ---------------------------------------------------
ietf: IETF Standard Tag allocated in the IANA YANG Module
IETF Tag Registry.
vendor: Non-standardized tags allocated by the module implementer.
user: Non-standardized tags allocated by and for the user.
Other SDOs (standard organizations) wishing to standardize their own
set of tags could allocate a top level prefix from this registry.
8.2. YANG Module IETF Tag Registry
This registry allocates prefixes that have the standard prefix
"ietf:". New values should be well considered and not achievable
through a combination of already existing standard tags.
The allocation policy for this registry is IETF Review [RFC5226].
The initial values for this registry are as follows.
+----------------------------+--------------------------+-----------+
| Tag | Description | Reference |
+----------------------------+--------------------------+-----------+
| ietf:network-element-class | A module for a network | [RFC8199] |
| | element. | |
| | | |
| ietf:network-service-class | A module for a network | [RFC8199] |
| | service. | |
| | | |
| ietf:sdo-defined-class | A module defined by a | [RFC8199] |
| | standards organization. | |
| | | |
| ietf:vendor-defined-class | A module defined by a | [RFC8199] |
| | vendor. | |
| | | |
| ietf:user-defined-class | A module defined by the | [RFC8199] |
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| | user. | |
| | | |
| ietf:hardware | A module relating to | [This |
| | hardware (e.g., | document] |
| | inventory). | |
| | | |
| ietf:software | A module relating to | [This |
| | software (e.g., | document] |
| | installed OS). | |
| | | |
| ietf:qos | A module for managing | [This |
| | quality of service. | document] |
| | | |
| ietf:protocol | A module representing a | [This |
| | protocol. | document] |
| | | |
| ietf:system-management | A module relating to | [This |
| | system management (e.g., | document] |
| | a system management | |
| | protocol such as syslog, | |
| | TACAC+, SNMP, netconf, | |
| | ...). | |
| | | |
| ietf:network-service | A module relating to | [This |
| | network service (e.g., a | document] |
| | network service protocol | |
| | such as an NTP server, | |
| | DNS server, DHCP server, | |
| | etc). | |
| | | |
| ietf:oam | A module representing | [This |
| | Operations, | document] |
| | Administration, and | |
| | Maintenance (e.g., BFD). | |
| | | |
| ietf:routing | A module related to | [This |
| | routing. | document] |
| | | |
| ietf:signaling | A module representing | [This |
| | control plane signaling. | document] |
| | | |
| ietf:lmp | A module representing a | [This |
| | link management | document] |
| | protocol. | |
+----------------------------+--------------------------+-----------+
Table 1: IETF Module Tag Registry
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9. References
9.1. Normative References
[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>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[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>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
9.2. Informative References
[RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", RFC 8199, DOI 10.17487/RFC8199, July
2017, <https://www.rfc-editor.org/info/rfc8199>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
Appendix A. Acknowledgements
Special thanks to Robert Wilton for his help improving the
introduction and providing the example use cases.
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Appendix B. Example
The following is a fictional example result from a query of the
module tags list. For the sake of brevity only a few module results
are imagined.
{
"ietf-module-tags:module-tags": {
"module": [
{
"name": "ietf-bfd",
"tag": [
"ietf:network-element-class",
"ietf:oam",
"ietf:protocol",
"ietf:sdo-defined-class"
]
},
{
"name": "ietf-isis",
"tag": [
"ietf:network-element-class",
"ietf:protocol",
"ietf:routing"
"ietf:sdo-defined-class",
]
},
{
"name": "ietf-ssh-server",
"tag": [
"ietf:network-element-class",
"ietf:protocol",
"ietf:sdo-defined-class",
"ietf:system-management"
]
}
]
}
}
Authors' Addresses
Christan Hopps
LabN Consulting, L.L.C.
Email: chopps@chopps.org
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Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Dean Bogdanovic
Volta Networks
Email: ivandean@gmail.com
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