Network Working Group C. Hopps
Internet-Draft Deutsche Telekom
Updates: rfc6087bis (if approved) L. Berger
Intended status: Standards Track LabN Consulting, L.L.C.
Expires: April 27, 2018 D. Bogdanovic
October 24, 2017
YANG Module Tags
draft-rtgyangdt-netmod-module-tags-02
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, as well as an augmentation to YANG library.
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 [I-D.ietf-netmod-rfc6087bis].
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 27, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Tag Locations . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Tag Prefixes . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. IETF Standard Tags . . . . . . . . . . . . . . . . . . . 3
4.2. Vendor Tags . . . . . . . . . . . . . . . . . . . . . . . 3
4.3. Local Tags . . . . . . . . . . . . . . . . . . . . . . . 4
4.4. Reserved Tags . . . . . . . . . . . . . . . . . . . . . . 4
5. Tag Management . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Module Definition Association . . . . . . . . . . . . . . 4
5.2. Implementation Association . . . . . . . . . . . . . . . 4
5.3. Administrative Tagging . . . . . . . . . . . . . . . . . 4
5.3.1. Resetting Tags . . . . . . . . . . . . . . . . . . . 5
6. Tags Module Structure . . . . . . . . . . . . . . . . . . . . 5
6.1. Tags Module Tree . . . . . . . . . . . . . . . . . . . . 5
6.2. Tags Module . . . . . . . . . . . . . . . . . . . . . . . 5
7. Library Augmentation . . . . . . . . . . . . . . . . . . . . 7
7.1. Library Augmentation Module . . . . . . . . . . . . . . . 8
8. Other Classifications . . . . . . . . . . . . . . . . . . . . 9
9. Guidelines to Model Writers . . . . . . . . . . . . . . . . . 9
9.1. Define Standard Tags . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10.1. YANG Module Tag Prefix Registry . . . . . . . . . . . . 10
10.2. YANG Module IETF Tag Registry . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
11.1. Normative References . . . . . . . . . . . . . . . . . . 12
11.2. Informative References . . . . . . . . . . . . . . . . . 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). Tags can be usefully standardized, but they can
also serve as a non-standardized mechanism available for users to
define themselves. Our solution provides for both cases allowing for
the most flexibility. 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 two modules. The first module defines a list
of module entries to allow for adding or removing of tags. It also
defines an RPC to reset a modules tags to the original values. The
second module defines an augmentation to YANG Library [RFC7895] to
allow for reading a modules tags.
This document also defines an IANA registry for tag prefixes as well
as a set of globally assigned tags.
Section 9 provides guidelines for authors of YANG data models. This
section updates [I-D.ietf-netmod-rfc6087bis].
2. Conventions Used in This Document
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 [RFC2119].
Note that lower case versions of these key words are used in section
Section 9 where guidance is provided to future document authors.
3. Tag Locations
Each module has only one logical tag list; however, that tag list may
be accessed from multiple locations.
We define two tag list locations. The first location is used for
configuration and is a top level list of module entries where each
entry contain the list of tags. The second read-only location is
through the yang library under the module entry.
4. Tag Prefixes
All tags have 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.
4.1. 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.
4.2. 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 consider
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including extra identification in the tag name to avoid collisions
(e.g., vendor:super-duper-company:...).
4.3. Local Tags
A local tag is any tag that has the prefix "local:". These tags are
defined by the local user/administrator and will never be
standardized.
4.4. Reserved Tags
Any tag not starting with the prefix "ietf:", "vendor:" or "local:"
is reserved for future standardization.
5. Tag Management
Tags can become associated with a module in a number of ways. Tags
may be defined and associated at model design time, at implementation
time, or via user administrative control. As the main consumer of
tags are users, users may also remove any tag, no matter how the tag
became associated with a module.
5.1. Module Definition Association
A module definition SHOULD indicate a set of tags to be automatically
added by the module implementer. These tags MUST be standard tags
(Section 4.1). This does imply that new modules may also drive the
addition of new standard tags to the IANA registry.
5.2. Implementation Association
An implementation MAY include additional tags associated with a
module. These tags may be standard or vendor specific tags.
5.3. Administrative Tagging
Tags of any kind can be assigned and removed with normal
configuration mechanisms. Additionally we define an RPC to reset a
module's tag list to the implementation default.
Implementations MUST ensure that a modules tag list is consistent
across any location from which the list is accessible. So if a user
adds a tag through configuration that tag should also be seen when
using the yang library augmentation.
Implementations that do not support the reset rpc statement (whether
at all, or just for a particular rpc or module) MUST respond with an
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YANG transport protocol-appropriate rpc layer error when such a
statement is received.
5.3.1. Resetting Tags
The "reset-tags" rpc statement is defined to reset a module's tag
list to the implementation default, i.e. the tags that are present
based on module definition and any that are added during
implementation time. This rpc statement takes module identification
information as input, and provides the list of tags that are present
after the reset.
6. Tags Module Structure
6.1. Tags Module Tree
The tree associated with the tags module is:
module: ietf-module-tags
rpcs:
+---x reset-tags
+---w input
| +---w name yang:yang-identifier
| +---w revision? union
+--ro output
+--ro tags* string
6.2. Tags Module
<CODE BEGINS> file "ietf-module-tags@2017-10-25.yang"
module ietf-module-tags {
yang-version "1";
namespace "urn:ietf:params:xml:ns:yang:ietf-module-tags";
prefix "mtags";
import ietf-yang-types {
prefix yang;
}
import ietf-yang-library {
prefix yanglib;
}
// meta
organization "IETF NetMod Working Group (NetMod)";
contact
"NetMod Working Group - <netmod@ietf.org>";
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description
"This module describes a tagging mechanism for yang module.
Tags may be IANA assigned or privately defined types.";
revision "2017-10-25" {
description
"Initial revision.";
reference "TBD";
}
grouping module-tags {
description
"A grouping that may be used to classify a module.";
leaf-list tags {
type string;
description
"The module associated tags. See the IANA 'YANG Module Tag
Prefix' registry for reserved prefixes and the IANA 'YANG
Module IETF Tag' registry for IETF standard tags";
}
}
grouping yanglib-common-leafs {
description
"Common parameters for YANG modules and submodules.
This definition extract from RFC7895 as it is defined as
a grouping within a grouping.
TBD is there a legal way to use a grouping defined within
another grouping without using the parent? If so, should change
to that.";
leaf name {
type yang:yang-identifier;
mandatory true;
description
"The YANG module or submodule name.";
}
leaf revision {
type union {
type yanglib:revision-identifier;
type string { length 0; }
}
mandatory true;
description
"The YANG module or submodule revision date.
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A zero-length string is used if no revision statement
is present in the YANG module or submodule.";
}
}
list module-tags {
key "name revision";
description
"A list of modules and their tags";
uses yanglib-common-leafs; // uses yanglib:common-leafs;
uses module-tags;
}
rpc reset-tags {
description
"Reset a list of tags for a given module to the list of module
and implementation time defiend tags. It provides the list of
tags associated with the module post reset.";
input {
uses yanglib-common-leafs; // uses yanglib:common-leafs;
}
output {
uses module-tags;
}
}
}
<CODE ENDS>
7. Library Augmentation
A modules tags can also be read using the yang library [RFC7895] if a
server supports both YANG library and the augmentation defined below.
If a server supports ietf-module-tags and the YANG library it SHOULD
also support the ietf-library-tags module.
The tree associated with the defined augmentation is:
module: ietf-library-tags
augment /yanglib:modules-state/yanglib:module:
+--ro tags* string
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7.1. Library Augmentation Module
<CODE BEGINS> file "ietf-library-tags@2017-08-12.yang"
module ietf-library-tags {
// namespace
namespace "urn:ietf:params:xml:ns:yang:ietf-library-tags";
prefix ylibtags;
import ietf-yang-library {
prefix yanglib;
}
import ietf-module-tags {
prefix mtags;
}
// meta
organization "IETF NetMod Working Group (NetMod)";
contact
"NetMod Working Group - <netmod@ietf.org>";
description
"This module augments ietf-yang-library with searchable
classfication tags. Tags may be IANA or privately defined
types.";
revision "2017-08-12" {
description
"Initial revision.";
reference "RFC TBD";
}
augment "/yanglib:modules-state/yanglib:module" {
description
"The yang library structure is augmented with a module tags
list. This allows operators to tag modules regardless of
whether the modules included tag support or not";
uses mtags:module-tags;
}
}
<CODE ENDS>
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8. Other Classifications
It's worth noting that a different yang module classification
document exists [RFC8199]. That document is classifying modules in
only a logical manner and does not define tagging or any other
mechanisms. It divides yang modules into 2 categories (service or
element) and then into one of 3 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.
9. Guidelines to Model Writers
This section updates [I-D.ietf-netmod-rfc6087bis].
9.1. Define Standard Tags
A module SHOULD indicate, in the description statement of the module,
a set of tags that are to be associated with it. This description
should also include the appropriate conformance statement or
statements, using [RFC2119] language for each tag.
module sample-module {
...
description
"[Text describing the module...]
RFC<this document> TAGS:
The following tags MUST be included by an implementation:
- ietf:some-required-tag:foo
- ...
The following tags SHOULD be included by an implementation:
- ietf:some-recommended-tag:bar
- ...
The following tags MAY be included by an implementation:
- ietf:some-optional-tag:baz
- ...
";
...
}
One SHOULD only include conformance text if there will be tags listed
(i.e., there's no need to indicate an empty set).
The module writer may use existing standard tags, or use new tags
defined in the model definition, as appropriate. New tags should be
assigned in the IANA registry defined below, see Section 10.2 below.
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10. IANA Considerations
10.1. 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.
local: 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.
10.2. 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.
[Editor's note: many of these tags may move to
[I-D.ietf-rtgwg-device-model] if/when that document is refactored to
use tags.]
+------------------------+------------------------------+-----------+
| Tag | Description | Reference |
+------------------------+------------------------------+-----------+
| ietf:rfc8199:element | A module for a network | [RFC8199] |
| | element. | |
| | | |
| ietf:rfc8199:service | A module for a network | [RFC8199] |
| | service. | |
| | | |
| ietf:rfc8199:standard | A module defined by a | [RFC8199] |
| | standards organization. | |
| | | |
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| ietf:rfc8199:vendor | A module defined by a | [RFC8199] |
| | vendor. | |
| | | |
| ietf:rfc8199:user | A module defined by the | [RFC8199] |
| | user. | |
| | | |
| ietf:device:hardware | A module relating to device | [This |
| | hardware (e.g., inventory). | document] |
| | | |
| ietf:device:software | A module relating to device | [This |
| | software (e.g., installed | document] |
| | OS). | |
| | | |
| ietf:device: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 system | [This |
| | management (e.g., a system | document] |
| | management protocol). | |
| | | |
| ietf:network-service | A module relating to network | [This |
| | service (e.g., a network | document] |
| | service protocol). | |
| | | |
| ietf:oam | A module representing | [This |
| | Operations, Administration, | document] |
| | and Maintenance. | |
| | | |
| ietf:routing | A module related to routing. | [This |
| | | document] |
| | | |
| ietf:routing:rib | A module related to routing | [This |
| | information bases. | document] |
| | | |
| ietf:routing:igp | An interior gateway protocol | [This |
| | module. | document] |
| | | |
| ietf:routing:egp | An exterior gateway protocol | [This |
| | module. | document] |
| | | |
| ietf:signaling | A module representing | [This |
| | control plane signaling. | document] |
| | | |
| ietf:lmp | A module representing a link | [This |
| | management protocol. | document] |
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+------------------------+------------------------------+-----------+
Table 1: IETF Module Tag Registry
11. References
11.1. Normative References
[I-D.ietf-netmod-rfc6087bis]
Bierman, A., "Guidelines for Authors and Reviewers of YANG
Data Model Documents", draft-ietf-netmod-rfc6087bis-14
(work in progress), September 2017.
[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>.
[RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,
<https://www.rfc-editor.org/info/rfc7895>.
[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>.
11.2. Informative References
[I-D.ietf-rtgwg-device-model]
Lindem, A., Berger, L., Bogdanovic, D., and C. Hopps,
"Network Device YANG Logical Organization", draft-ietf-
rtgwg-device-model-02 (work in progress), March 2017.
Authors' Addresses
Christan Hopps
Deutsche Telekom
Email: chopps@chopps.org
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Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Dean Bogdanovic
Email: ivandean@gmail.com
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