Internet Engineering Task Force (IETF) C. Hopps

Internet Engineering Task Force (IETF) C. Hopps
Request for Comments: 8819 L. Berger
Updates: 8407 LabN Consulting, L.L.C.
Category: Standards Track D. Bogdanovic
ISSN: 2070-1721 Volta Networks
January 2021

YANG Module Tags

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
modules tags is provided. Tags may be registered and assigned during
module definition, assigned by implementations, or dynamically
defined and set by users. This document also provides guidance to
future model writers; as such, this document updates RFC 8407.

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
https://www.rfc-editor.org/info/rfc8819.

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
(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
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
1.1. Some Possible Use Cases for YANG Module Tags
1.2. Conventions Used in This Document
2. Tag Values
2.1. IETF Tags
2.2. Vendor Tags
2.3. User Tags
2.4. Reserved Tags
3. Tag Management
3.1. Module Definition Tagging
3.2. Implementation Tagging
3.3. User Tagging
4. Tags Module Structure
4.1. Tags Module Tree
4.2. YANG Module
5. Other Classifications
6. Guidelines to Model Writers
6.1. Define Standard Tags
7. IANA Considerations
7.1. YANG Module Tag Prefixes Registry
7.2. IETF YANG Module Tags Registry
7.3. Updates to the IETF XML Registry
7.4. Updates to the YANG Module Names Registry
8. Security Considerations
9. References
9.1. Normative References
9.2. Informative References
Appendix A. Examples
Appendix B. Non-NMDA State Module
Acknowledgements
Authors' Addresses

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
registered, but they can also serve as a non-registered 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 registered as well as
assigned during module definition, assigned by implementations, or
dynamically defined and set by users.

This document defines a YANG module [RFC7950] that provides a list of
module entries to allow for adding or removing tags as well as
viewing the set of tags associated with a module.

This document defines an extension statement 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 6 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 (NMDA) defined in [RFC8342].

1.1. Some Possible Use Cases for YANG Module Tags

During this document's development, 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. For example, 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. For
example, 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 (for example, return all operational state related to system
management).

1.2. 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
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

2. Tag Values

All tags SHOULD begin with a prefix indicating who owns their
definition. An IANA registry (Section 7.1) is used to support
registering tag prefixes. Currently, three prefixes are defined. No
further structure is imposed by this document on the value following
the registered prefix, and the value can contain any YANG type
'string' characters except carriage returns, newlines, and tabs.

Again, except for the conflict-avoiding prefix, this document is
purposefully not specifying any structure on (i.e., restricting) the
tag values. The intent is to avoid arbitrarily restricting the
values that designers, implementers, and users can use. As a result
of this choice, designers, implementers, and users are free to add or
not add any structure they may require to their own tag values.

2.1. IETF Tags

An IETF tag is a tag that has the prefix "ietf:". All IETF tags are
registered with IANA in a registry defined later in this document
(Section 7.2).

2.2. 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
registered; however, it is RECOMMENDED that the vendor include extra
identification in the tag to avoid collisions, such as using the
enterprise or organization name following the "vendor:" prefix (e.g.,
vendor:example.com:vendor-defined-classifier).

2.3. User Tags

A user tag is any tag that has the prefix "user:". These tags are
defined by the user/administrator and are not meant to be registered.
Users are not required to use the "user:" prefix; however, doing so
is RECOMMENDED as it helps avoid collisions.

2.4. Reserved Tags

Any tag not starting with the prefix "ietf:", "vendor:", or "user:"
is reserved for future use. These tag values are not invalid but
simply reserved in the context of specifications (e.g., RFCs).

3. 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
consumer of tags are users, users may also remove any tag, no matter
how the tag became associated with a module.

3.1. Module Definition Tagging

A module definition MAY 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 is defined in an IETF Standards Track document, the
tags MUST be IETF tags (Section 2.1). Thus, new modules can drive
the addition of new IETF tags to the IANA registry defined in
Section 7.2, and the IANA registry can serve as a check against
duplication.

3.2. Implementation Tagging

An implementation MAY include additional tags associated with a
module. These tags SHOULD be IETF tags (i.e., registered) or vendor-
specific tags.

3.3. User Tagging

Tags of any kind, with or without a prefix, can be assigned and
removed by the user using normal configuration mechanisms. In order
to remove a tag from the operational datastore, the user adds a
matching "masked-tag" entry for a given module.

4. Tags Module Structure

4.1. 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

Figure 1: YANG Module Tags Tree Diagram

4.2. YANG Module

<CODE BEGINS> file "[email protected]"
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;
}

organization
"IETF NetMod Working Group (NetMod)";
contact
"WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:[email protected]>

Author: Christian Hopps
<mailto:[email protected]>

Author: Lou Berger
<mailto:[email protected]>

Author: Dean Bogdanovic
<mailto:[email protected]>";

description
"This module describes a mechanism associating tags with YANG
modules. Tags may be IANA assigned or privately defined.

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 is part of RFC 8819
(https://www.rfc-editor.org/info/rfc8819); see the RFC itself
for full legal notices.

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 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";

revision 2021-01-04 {
description
"Initial revision.";
reference
"RFC 8819: YANG Module Tags";
}

typedef tag {
type string {
length "1..max";
pattern '[\S ]+';
}
description
"A tag is a type of 'string' value that does not include
carriage return, newline, or tab characters. It SHOULD begin
with a registered prefix; however, tags without a registered
prefix SHOULD NOT be treated as invalid.";
}

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 predefined tags should be set to 'system'
[RFC8342].";
}

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 Prefixes' registry for reserved prefixes and
the IANA 'IETF YANG Module Tags' registry for IETF 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
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>

Figure 2: Module Tags Module

5. 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 IETF tags to support the classification style
described in [RFC8199].

6. Guidelines to Model Writers

This section updates [RFC8407].

6.1. 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 {
namespace "https://example.com/yang/example";
prefix "ex";
//...
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 IETF
standardized modules, new tags MUST be assigned in the IANA registry
defined below, see Section 7.2.

7. IANA Considerations

7.1. YANG Module Tag Prefixes Registry

IANA has created the "YANG Module Tag Prefixes" subregistry in the
"YANG Module Tags" registry.

This registry allocates tag prefixes. All YANG module tags SHOULD
begin with one of the prefixes in this registry.

Prefix entries in this registry should be short strings consisting of
lowercase ASCII alpha-numeric characters and a final ":" character.

The allocation policy for this registry is Specification Required
[RFC8126]. The Reference and Assignee values should be sufficient to
identify and contact the organization that has been allocated the
prefix.

The initial values for this registry are as follows.

+=========+========================+===========+==========+
| Prefix | Description | Reference | Assignee |
+=========+========================+===========+==========+
| ietf: | IETF tags allocated in | RFC 8819 | IETF |
| | the IANA "IETF YANG | | |
| | Module Tags" registry. | | |
+---------+------------------------+-----------+----------+
| vendor: | Non-registered tags | RFC 8819 | IETF |
| | allocated by the | | |
| | module implementer. | | |
+---------+------------------------+-----------+----------+
| user: | Non-registered tags | RFC 8819 | IETF |
| | allocated by and for | | |
| | the user. | | |
+---------+------------------------+-----------+----------+

Table 1

Other standards development organizations (SDOs) wishing to allocate
their own set of tags should allocate a prefix from this registry.

7.2. IETF YANG Module Tags Registry

IANA has created the "IETF YANG Module Tags" subregistry within the
"YANG Module Tags" registry . This registry appears below the "YANG
Module Tag Prefixes" registry.

This registry allocates tags that have the registered prefix "ietf:".
New values should be well considered and not achievable through a
combination of already existing IETF tags. IANA assigned tags must
conform to Net-Unicode as defined in [RFC5198], and they shall not
need normalization.

The allocation policy for this registry is IETF Review [RFC8126].

The initial values for this registry are as follows.

+============================+=======================+===========+
| Tag | Description | Reference |
+============================+=======================+===========+
| ietf:network-element-class | Network element as | [RFC8199] |
| | defined in [RFC8199]. | |
+----------------------------+-----------------------+-----------+
| ietf:network-service-class | Network service as | [RFC8199] |
| | defined in [RFC8199]. | |
+----------------------------+-----------------------+-----------+
| ietf:sdo-defined-class | Module is defined by | [RFC8199] |
| | a standards | |
| | organization. | |
+----------------------------+-----------------------+-----------+
| ietf:vendor-defined-class | Module is defined by | [RFC8199] |
| | a vendor. | |
+----------------------------+-----------------------+-----------+
| ietf:user-defined-class | Module is defined by | [RFC8199] |
| | the user. | |
+----------------------------+-----------------------+-----------+
| ietf:hardware | Relates to hardware | RFC 8819 |
| | (e.g., inventory). | |
+----------------------------+-----------------------+-----------+
| ietf:software | Relates to software | RFC 8819 |
| | (e.g., installed OS). | |
+----------------------------+-----------------------+-----------+
| ietf:protocol | Represents a protocol | RFC 8819 |
| | (often combined with | |
| | another tag to | |
| | refine). | |
+----------------------------+-----------------------+-----------+
| ietf:qos | Relates to quality of | RFC 8819 |
| | service. | |
+----------------------------+-----------------------+-----------+
| ietf:network-service-app | Relates to a network | RFC 8819 |
| | service application | |
| | (e.g., an NTP server, | |
| | DNS server, DHCP | |
| | server, etc.). | |
+----------------------------+-----------------------+-----------+
| ietf:system-management | Relates to system | RFC 8819 |
| | management (e.g., a | |
| | system management | |
| | protocol such as | |
| | syslog, TACAC+, SNMP, | |
| | NETCONF, etc.). | |
+----------------------------+-----------------------+-----------+
| ietf:oam | Relates to | RFC 8819 |
| | Operations, | |
| | Administration, and | |
| | Maintenance (e.g., | |
| | BFD). | |
+----------------------------+-----------------------+-----------+
| ietf:routing | Relates to routing. | RFC 8819 |
+----------------------------+-----------------------+-----------+
| ietf:security | Related to security. | RFC 8819 |
+----------------------------+-----------------------+-----------+
| ietf:signaling | Relates to control- | RFC 8819 |
| | plane signaling. | |
+----------------------------+-----------------------+-----------+
| ietf:link-management | Relates to link | RFC 8819 |
| | management. | |
+----------------------------+-----------------------+-----------+

Table 2

7.3. Updates to the IETF XML Registry

This document registers a URI in the "IETF XML Registry" [RFC3688].
Following the format in [RFC3688], the following registrations have
been made:

URI: urn:ietf:params:xml:ns:yang:ietf-module-tags
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.

URI: urn:ietf:params:xml:ns:yang:ietf-module-tags-state
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.

7.4. Updates to the YANG Module Names Registry

This document registers two YANG modules in the "YANG Module Names"
registry [RFC6020]. Following the format in [RFC6020], the following
registrations have been made:

name: ietf-module-tags
namespace: urn:ietf:params:xml:ns:yang:ietf-module-tags
prefix: tags
reference: RFC 8819

name: ietf-module-tags-state
namespace: urn:ietf:params:xml:ns:yang:ietf-module-tags-state
prefix: tags-s
reference: RFC 8819

8. Security Considerations

The YANG module defined in this memo is designed to be accessed via
the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the
secure transport layer and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242].

This document adds the ability to associate tag metadata with YANG
modules. This document does not define any actions based on these
associations, and none are yet defined; therefore, it does not by
itself introduce any new security considerations directly.

Users of the tag metadata may define various actions to be taken
based on the tag metadata. These actions and their definitions are
outside the scope of this document. Users will need to consider the
security implications of any actions they choose to define, including
the potential for a tag to get 'masked' by another user.

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>.

[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>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.

[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>.

[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>.

[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>.

[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

[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.

[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<https://www.rfc-editor.org/info/rfc5198>.

[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.

[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.

[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.

[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>.

Appendix A. Examples

The following is a fictional NETCONF example result from a query of
the module tags list. For the sake of brevity, only a few module
results are shown.

<ns0:data xmlns:ns0="urn:ietf:params:xml:ns:netconf:base:1.0">
<t:module-tags
xmlns:t="urn:ietf:params:xml:ns:yang:ietf-module-tags">
<t:module>
<t:name>ietf-bfd</t:name>
<t:tag>ietf:network-element-class</t:tag>
<t:tag>ietf:oam</t:tag>
<t:tag>ietf:protocol</t:tag>
<t:tag>ietf:sdo-defined-class</t:tag>
</t:module>
<t:module>
<t:name>ietf-isis</t:name>
<t:tag>ietf:network-element-class</t:tag>
<t:tag>ietf:protocol</t:tag>
<t:tag>ietf:sdo-defined-class</t:tag>
<t:tag>ietf:routing</t:tag>
</t:module>
<t:module>
<t:name>ietf-ssh-server</t:name>
<t:tag>ietf:network-element-class</t:tag>
<t:tag>ietf:protocol</t:tag>
<t:tag>ietf:sdo-defined-class</t:tag>
<t:tag>ietf:system-management</t:tag>
</t:module>
</t:module-tags>
</ns0:data>

Figure 3: Example NETCONF Query Output

Appendix B. Non-NMDA State Module

As per [RFC8407], the following is a non-NMDA module to support
viewing the operational state for non-NMDA compliant servers.

<CODE BEGINS> file "[email protected]"
module ietf-module-tags-state {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-module-tags-state";
prefix tags-s;

import ietf-yang-types {
prefix yang;
}
import ietf-module-tags {
prefix tags;
}

organization
"IETF NetMod Working Group (NetMod)";
contact
"WG Web: <https://datatracker.ietf.org/wg/netmod/>
WG List: <mailto:[email protected]>

Author: Christian Hopps
<mailto:[email protected]>

Author: Lou Berger
<mailto:[email protected]>

Author: Dean Bogdanovic
<mailto:[email protected]>";

description
"This module describes a mechanism associating tags with YANG
modules. Tags may be IANA assigned or privately defined.

This is a temporary non-NMDA module that is for use by
implementations that don't yet support NMDA.

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 is part of RFC 8819
(https://www.rfc-editor.org/info/rfc8819); see the RFC itself
for full legal notices.";

revision 2021-01-04 {
description
"Initial revision.";
reference
"RFC 8819: YANG Module Tags";
}

container module-tags-state {
config false;
status deprecated;
description
"Contains the list of modules and their associated tags.";
list module {
key "name";
status deprecated;
description
"A list of modules and their associated tags.";
leaf name {
type yang:yang-identifier;
mandatory true;
status deprecated;
description
"The YANG module name.";
}
leaf-list tag {
type tags:tag;
status deprecated;
description
"Tags associated with the module. See the IANA 'YANG
Module Tag Prefixes' registry for reserved prefixes and
the IANA 'IETF YANG Module Tags' registry for IETF tags.

The contents of this list is constructed using the
following steps:

1) System tags (i.e., tags of added by the system) are
added.
2) User-configured tags (i.e., tags added by
configuration) are added.
3) Any tag that is equal to a masked-tag present in the
corresponding ietf-module-tags:module-tags:module-tag leaf
list for this module is removed.";
}
}
}
}
<CODE ENDS>

Figure 4: Non-NMDA Module Tags State Module

Acknowledgements

Special thanks to Robert Wilton for his help improving the
introduction and providing the example use cases, as well as
generating the non-NMDA module.

Authors' Addresses

Christian Hopps
LabN Consulting, L.L.C.

Email: [email protected]

Lou Berger
LabN Consulting, L.L.C.

Email: [email protected]

Dean Bogdanovic
Volta Networks

Email: [email protected]