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: August 12, 2017 D. Bogdanovic
February 8, 2017
YANG Module Tags
draft-rtgyangdt-netmod-module-tags-00
Abstract
This document defines two modules that support the association of
tags with modules. Tags may be included in a module or associated
with a module through the use of an augmentation to YANG library that
is defined in this document. The expectation is for such tags to be
used to help classify and organize modules. 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
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://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 12, 2017.
Copyright Notice
Copyright (c) 2017 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
(http://trustee.ietf.org/license-info) in effect on the date of
Hopps, et al. Expires August 12, 2017 [Page 1]
Internet-Draft YANG Module Tags February 2017
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 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
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Tag Locations . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Tag Prefixes . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. IETF Standard Tags . . . . . . . . . . . . . . . . . . . 4
4.2. Vendor Tags . . . . . . . . . . . . . . . . . . . . . . . 4
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. Adding Tags . . . . . . . . . . . . . . . . . . . . . 5
5.3.2. Removing Tags . . . . . . . . . . . . . . . . . . . . 5
5.3.3. Resetting Tags . . . . . . . . . . . . . . . . . . . 5
6. Tags Module Structure . . . . . . . . . . . . . . . . . . . . 6
6.1. Tags Module Tree . . . . . . . . . . . . . . . . . . . . 6
6.2. Tags Module . . . . . . . . . . . . . . . . . . . . . . . 6
7. Library Augmentation . . . . . . . . . . . . . . . . . . . . 8
7.1. Library Augmentation Module . . . . . . . . . . . . . . . 9
8. Other Classifications . . . . . . . . . . . . . . . . . . . . 10
9. Guidelines to Model Writers . . . . . . . . . . . . . . . . . 11
9.1. Include Module Tags . . . . . . . . . . . . . . . . . . . 11
9.2. Define Standard Tags . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10.1. YANG Module Tag Prefix Registry . . . . . . . . . . . . 12
10.2. YANG Module IETF Tag Registry . . . . . . . . . . . . . 12
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
The use of tags for classification and organization is fairly
ubiquitous not only within IETF protocols, but in the internet itself
(see #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
Hopps, et al. Expires August 12, 2017 [Page 2]
Internet-Draft YANG Module Tags February 2017
the most flexibility. In particular, tags may be standardized and
assigned during module definition; assigned by implementations; or
dynamically defined and set by users.
This document defines two modules that support the association of
tags with modules. The first module defines a grouping which
contains a list of tags as well as rpc statements for changing the
contents of the list. Tags are strings that are structured to enable
the differentiation of globally assigned and non-assigned tags based
on a fixed prefix. This document also defines an initial set of
globally assigned tags.
The second module defined in this document defines an augmentation to
YANG Library [RFC7895]. It uses (imports) the first module to
provide a well known location for 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
Two tag list locations are defined. One location is within the
module itself, and the other location is in the yang library under
the modules entry. When a module includes tags, the same tag list
may also be presented in yang library.
To add tags to a module, the module definition includes a tag list
using the 'module-tags' grouping defined in this document. This list
MUST be added by a module author under container named "module-tags"
at the root of their module.
4. Tag Prefixes
All tags have a prefix indicating who owns their definition. An IANA
registry is used to support standardizing tag prefixes. Currently 2
prefixes are defined with all others reserved.
Hopps, et al. Expires August 12, 2017 [Page 3]
Internet-Draft YANG Module Tags February 2017
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.
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 as associated at model design time, at implementation
time, or via user administrative control. As the main consumer of
tags are users, users may 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 standard 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
RPC statements are defined in this document to enable administrative
addition and removal of tags from a module by a user. An additional
Hopps, et al. Expires August 12, 2017 [Page 4]
Internet-Draft YANG Module Tags February 2017
rpc is defined to reset a module's tag list to the implementation
default.
Each rpc identifies the module on which the tag operation is to be
performed. This identifications reuses the format of the common-
leafs (sub) grouping defined in [RFC7895]. The grouping itself is
refined in Section 6 so that it is a stand-alone grouping.
Implementations that support the rpc statements defined in this
document MUST ensure that a specific module's tags leaf list is
consistent across any location from which the list is available.
Specifically this includes in the module itself, per Section 9.1, or
in yang library, per Section 7.
Implementations that do not support the defined rpc statements
(whether at all, or just for a particular rpc or module) MUST respond
with an YANG transport protocol-appropriate rpc layer error when such
a statement is received.
5.3.1. Adding Tags
The "add-tags" rpc statement is defined to support the addition of
tags. This rpc statement takes as input module identification
information and the list of tags to add.
No restriction is placed on the tag values to add.
5.3.2. Removing Tags
The "remove-tags" rpc statement is defined to remove tags. This rpc
statement takes as input module identification information and the
list of tags to remove.
No restriction is placed on the tag values to remove. This means
that tags associated based on a module's definition or implementation
MUST be removable.
5.3.3. 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 list of tags that are
present after the reset.
Hopps, et al. Expires August 12, 2017 [Page 5]
Internet-Draft YANG Module Tags February 2017
6. Tags Module Structure
6.1. Tags Module Tree
The tree associated with the tags module is:
module: ietf-module-tags
rpcs:
+---x add-tags
| +---w input
| +---w name yang:yang-identifier
| +---w revision? union
| +---w tags* string
+---x remove-tags
| +---w input
| +---w name yang:yang-identifier
| +---w revision? union
| +---w tags* string
+---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@2017-02-08.yang"
module ietf-module-tags {
yang-version "1.1";
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>";
description
Hopps, et al. Expires August 12, 2017 [Page 6]
Internet-Draft YANG Module Tags February 2017
"This module describes a tagging mechanism for yang module.
Tags may be IANA assigned or privately defined types.";
revision "2017-02-08" {
description
"Initial revision.";
reference "TBD";
}
grouping module-tags {
description
"A grouping that may be used to classify a module.";
leaf-list tags {
type string;
config false;
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 wuthin
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; }
}
description
"The YANG module or submodule revision date.
Hopps, et al. Expires August 12, 2017 [Page 7]
Internet-Draft YANG Module Tags February 2017
A zero-length string is used if no revision statement
is present in the YANG module or submodule.";
}
}
rpc add-tags {
description
"Add a list of tags to a given module.";
input {
uses yanglib-common-leafs;
uses module-tags;
}
}
rpc remove-tags {
description
"Remove a list of tags, if present, from a given module.";
input {
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;
}
output {
uses module-tags;
}
}
}
<CODE ENDS>
7. Library Augmentation
Tags can also be associated with a module using the yang library
[RFC7895]. When a server supports both yang library and the
augmentation defined below, a user can add, remove and search for
tags for any module on the server regardless of whether the specific
Hopps, et al. Expires August 12, 2017 [Page 8]
Internet-Draft YANG Module Tags February 2017
module included tag support in its definition or not. 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
7.1. Library Augmentation Module
Hopps, et al. Expires August 12, 2017 [Page 9]
Internet-Draft YANG Module Tags February 2017
<CODE BEGINS> file "ietf-library-tags@2017-02-08.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 "2017-02-06" {
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>
8. Other Classifications
It's worth noting that a different yang module classification
document exists [I-D.ietf-netmod-yang-model-classification]. That
document is classifying modules in only a logical manner and does not
Hopps, et al. Expires August 12, 2017 [Page 10]
Internet-Draft YANG Module Tags February 2017
define tagging or any other mechanisms. It divides yang modules into
2 categories (service or entity) 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 [I-D.ietf-netmod-yang-model-classification] style
classification.
9. Guidelines to Model Writers
This section updates [I-D.ietf-netmod-rfc6087bis]. This document
makes two recommendations to model writers,
9.1. Include Module Tags
The correct way to use the module-tags grouping is to include it in a
standard location at the top level of your module, specifically
contained within a container named "module-tags". This standard
location allows searching module using a well-known xpath wilcard
path. For example:
module sample-module {
...
import ietf-module-tags {
prefix mtags;
}
...
container module-tags {
description
"A list of classification tags associated with this
module. The following predefined tags <MUST|SHOULD|MAY>
be included by an implementation:
- ietf:foo
- ietf:bar
- ...
";
uses mtags:module-tags;
}
...
}
The associated tree will look like:
Hopps, et al. Expires August 12, 2017 [Page 11]
Internet-Draft YANG Module Tags February 2017
module: sample-module
+--rw module-tags
| +--ro tags* string
+--...
9.2. Define Standard Tags
A module should indicate, in the description of the "module-tags"
container, the set of tags that are to be populated in the leaf-list
for any implementation of the module. This description should also
include the appropriate conformance statement or statements, using
[RFC2119] language, for each tag.
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.
10. IANA Considerations
10.1. YANG Module Tag Prefix Registry
This registry allocates tag prefixes. All YANG module tags must
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.
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.
Hopps, et al. Expires August 12, 2017 [Page 12]
Internet-Draft YANG Module Tags February 2017
[Editor's note: some of these tags are expected to move to
[I-D.ietf-rtgwg-device-model] if/when this document becomes a WG
document and that document is refactored to use tags.]
+---------------------------------+---------------------+-----------+
| Tag | Description | Reference |
+---------------------------------+---------------------+-----------+
| ietf:area:art | Applications and | [This |
| | Real-Time Area | document] |
| | module. | |
| | | |
| ietf:area:gen | General Area | [This |
| | module. | document] |
| | | |
| ietf:area:int | Internet Area | [This |
| | module. | document] |
| | | |
| ietf:area:ops | Operations and | [This |
| | Management Area | document] |
| | module. | |
| | | |
| ietf:area:rtg | Routing Area | [This |
| | module. | document] |
| | | |
| ietf:area:sec | Security Area | [This |
| | module. | document] |
| | | |
| ietf:area:tsv | Transport Area | [This |
| | module. | document] |
| | | |
| ietf:entity | A module for an | [This |
| | entity (*). | document] |
| | | |
| ietf:service | A module for a | [This |
| | service (*). | document] |
| | | |
| ietf:hardware | A module for | [This |
| | hardware. | document] |
| | | |
| ietf:software | A module for | [This |
| | software. | document] |
| | | |
| ietf:protocol | A module | [This |
| | representing a | document] |
| | protocol. | |
| | | |
| ietf:protocol:system-management | A module | [This |
| | representing a | document] |
Hopps, et al. Expires August 12, 2017 [Page 13]
Internet-Draft YANG Module Tags February 2017
| | system management | |
| | protocol. | |
| | | |
| ietf:protocol:network-service | A module | [This |
| | representing a | document] |
| | network service | |
| | protocol. | |
| | | |
| ietf:protocol:routing | A module | [This |
| | representing a | document] |
| | control plane | |
| | routing protocol. | |
| | | |
| ietf:protocol:signaling | A module | [This |
| | representing a | document] |
| | control plane | |
| | signaling protocol. | |
| | | |
| ietf:protocol:oam | A module | [This |
| | representing a | document] |
| | Operations, | |
| | Administration, and | |
| | Maintenance | |
| | protocol. | |
| | | |
| ietf:protocol:lmp | A module | [This |
| | representing a link | document] |
| | management | |
| | protocol. | |
| | | |
| ietf:protocol:routing:igp | An IGP protocol | [This |
| | module. | document] |
| | | |
| ietf:protocol:routing:egp | An EGP protocol | [This |
| | module. | document] |
+---------------------------------+---------------------+-----------+
(*) - see [I-D.ietf-netmod-yang-model-classification]
Table 1: IETF Module Tag Registry
11. References
11.1. Normative References
Hopps, et al. Expires August 12, 2017 [Page 14]
Internet-Draft YANG Module Tags February 2017
[I-D.ietf-netmod-rfc6087bis]
Bierman, A., "Guidelines for Authors and Reviewers of YANG
Data Model Documents", draft-ietf-netmod-rfc6087bis-10
(work in progress), January 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://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,
<http://www.rfc-editor.org/info/rfc7895>.
11.2. Informative References
[I-D.ietf-netmod-yang-model-classification]
Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", draft-ietf-netmod-yang-model-
classification-04 (work in progress), October 2016.
[I-D.ietf-rtgwg-device-model]
Lindem, A., Berger, L., Bogdanovic, D., and C. Hopps,
"Network Device YANG Organizational Models", draft-ietf-
rtgwg-device-model-01 (work in progress), October 2016.
Authors' Addresses
Christan Hopps
Deutsche Telekom
Email: chopps@chopps.org
Lou Berger
LabN Consulting, L.L.C.
Email: lberger@labn.net
Dean Bogdanovic
Email: ivandean@gmail.com
Hopps, et al. Expires August 12, 2017 [Page 15]