YANG Library
draft-ietf-netconf-rfc7895bis-05
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8525.
|
|
|---|---|---|---|
| Authors | Andy Bierman , Martin Björklund , Jürgen Schönwälder , Kent Watsen , Robert Wilton | ||
| Last updated | 2018-04-04 (Latest revision 2018-02-27) | ||
| Replaces | draft-nmdsdt-netconf-rfc7895bis | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Mahesh Jethanandani | ||
| IESG | IESG state | Became RFC 8525 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | Mahesh Jethanandani <mjethanandani@gmail.com> |
draft-ietf-netconf-rfc7895bis-05
Network Working Group A. Bierman
Internet-Draft YumaWorks
Obsoletes: 7895 (if approved) M. Bjorklund
Intended status: Standards Track Tail-f Systems
Expires: August 31, 2018 J. Schoenwaelder
Jacobs University
K. Watsen
Juniper Networks
R. Wilton
Cisco Systems
February 27, 2018
YANG Library
draft-ietf-netconf-rfc7895bis-05
Abstract
This document describes a YANG library that provides information
about the YANG modules, datastores, and datastore schemas used by a
network management server. Simple caching mechanisms are provided to
allow clients to minimize retrieval of this information. This
version of the YANG library supports the Network Management Datastore
Architecture by listing all datastores supported by a network
management server and the schema that is used by each of these
datastores.
This document obsoletes RFC 7895.
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 31, 2018.
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Copyright Notice
Copyright (c) 2018 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
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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. YANG Library Data Model . . . . . . . . . . . . . . . . . . . 6
5. YANG Library YANG Module . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
9.1. Normative References . . . . . . . . . . . . . . . . . . 22
9.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Summary of Changes from RFC 7895 . . . . . . . . . . 25
Appendix B. Example YANG Library Instance for a Basic Server . . 25
Appendix C. Example YANG Library Instance for an Advanced Server 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
There is a need for a standard mechanism to expose which YANG modules
[RFC7950], datastores and datastore schemas
[I-D.ietf-netmod-revised-datastores] are in use by a network
management server.
This document defines the YANG module "ietf-yang-library" that
provides this information. This version of the YANG library is
compatible with the Network Management Datastore Architecture (NMDA)
[I-D.ietf-netmod-revised-datastores]. The previous version of the
YANG library, defined in [RFC7895], is not compatible with the NMDA
since it assumes that all datastores have exactly the same schema.
This is not necessarily true in the NMDA since dynamic configuration
datastores may have their own datastore schema. Furthermore, the
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operational state datastore may support non-configurable YANG modules
in addition to the YANG modules supported by conventional
configuration datastores.
The old YANG library definitions have been retained (for backwards
compatibility reasons) but the definitions have been marked as
deprecated. For backwards compatibility, an NMDA-supporting server
SHOULD populate the deprecated "/modules-state" tree in a backwards-
compatible manner. The new "/yang-library" tree would be ignored by
legacy clients, while providing all the data needed for NMDA-aware
clients, which would themselves ignore the "/modules-state" tree.
The recommended approach to populate "/modules-state" is to report
the schema for YANG modules that are configurable via conventional
datastores and for which config false data nodes are returned via a
NETCONF <get> operation, or equivalent.
The YANG library information can be different on every server and it
can change at runtime or across a server reboot. If a server
implements multiple network management protocols to access the
server's datastores, then each such protocol may have its own
conceptual instantiation of the YANG library.
If a large number of YANG modules are utilized by a server, then the
YANG library contents can be relatively large. Since the YANG
library contents changes very infrequently, it is important that
clients be able to cache the YANG library contents and easily
identify whether their cache is out of date.
All NETCONF servers supporting YANG 1.1 [RFC7950] are required to
support YANG Library (see Section 5.6.4 of RFC 7950). NETCONF
servers implementing the NETCONF extensions to support the NMDA
[I-D.ietf-netconf-nmda-netconf] must implement at least the version
of the YANG library defined in this document. Similarly, all
RESTCONF servers are required to support YANG Library (see Section 10
of RFC 8040). RESTCONF servers implementing the RESTCONF extensions
to support the NMDA [I-D.ietf-netconf-nmda-restconf] must implement
at least the version of the YANG library defined in this document.
The keywords "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].
2. Terminology
The following terms are defined in [RFC7950]:
o module
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o submodule
o data node
This document uses the phrase "implementing a module" as defined in
[RFC7950] Section 5.6.5.
The following terms are defined in
[I-D.ietf-netmod-revised-datastores]:
o datastore
o datastore schema
o configuration
o configuration datastore
o conventional configuration
o conventional configuration datastore
o operational state
o operational state datastore
o dynamic configuration datastore
o client and server
The following terms are used within this document:
o YANG library: A collection of YANG modules, submodules,
datastores, and datastore schemas used by a server.
o YANG library checksum: A server-generated checksum of the contents
of the YANG library.
Tree diagrams used in this document use the notation defined in
[I-D.ietf-netmod-yang-tree-diagrams].
3. Objectives
The following information is needed by a client application (for each
YANG module in the library) to fully utilize the YANG data modeling
language:
o name: The name of the YANG module.
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o revision: Each YANG module and submodule within the library SHOULD
have a revision. This is derived from the most recent revision
statement within the module or submodule.
o submodule list: The name, and if defined, revision of each
submodule used by the module MUST be identified.
o feature list: The name of each YANG feature supported by the
server, in a given datastore schema, MUST be identified.
o deviation list: The name of each YANG module with deviation
statements affecting a given YANG module, in a given datastore
schema, MUST be identified.
In addition, the following information is needed by a client
application for each datastore supported by a server:
o identity: The YANG identity for the datastore.
o schema: The schema (i.e., the set of modules) implemented by the
datastore.
In order to select one out of several possible data model designs,
the following criteria were used:
1. Efficient for a client to consume. Since the size of the YANG
library can be quite large, it should be possible for clients to
cache the YANG library information.
2. A dynamic configuration datastore must be able to implement a
module or feature that is not implemented in the conventional
configuration datastores.
3. It must be possible to NOT implement a module or feature in
<operational>, even if it is implemented in some other datastore.
This is required for transition purposes; a server that wants to
implement <operational> should not have to implement all modules
at once.
4. A given module can only be implemented in one revision in all
datastores. If a module is implemented in more than one
datastores, the same revision is implemented in all these
datastores.
5. Multiple revisions can be used for import, if import-by revision
is used.
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6. Make it possible to use the YANG library by schema mount
[I-D.ietf-netmod-schema-mount].
4. YANG Library Data Model
The "ietf-yang-library" YANG module provides information about the
modules, submodules, datastores, and datastore schemas supported by a
server. All data nodes in "ietf-yang-library" are "config false",
and thus only accessible in the operational state datastore.
+-----------+
| datastore |
+-----------+
|
| has a
V
+-----------+ +--------+ +------------+
| datastore | union of | module | consists of | modules + |
| schema |----------->| set |--------------->| submodules |
+-----------+ +--------+ +------------+
Figure 1
The conceptual model of the YANG library is depicted in Figure 1.
Following the NMDA, every datastore has an associated datastore
schema. A datastore schema is a union of module sets and every
module set is a collection of modules and submodules, including the
modules and submodules used for imports. Note that multiple
datastores may refer to the same datastore schema. Furthermore, it
is possible that individual datastore schemas share module sets. A
common use case is the operational state datastore schema which is a
superset of the schema used by conventional configuration datastores.
Below is the YANG Tree Diagram for the "ietf-yang-library" module,
excluding the deprecated "modules-state" tree:
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module: ietf-yang-library
+--ro yang-library
+--ro module-set* [name]
| +--ro name string
| +--ro module* [name]
| | +--ro name yang:yang-identifier
| | +--ro revision? revision-identifier
| | +--ro namespace inet:uri
| | +--ro location* inet:uri
| | +--ro submodule* [name]
| | | +--ro name yang:yang-identifier
| | | +--ro revision? revision-identifier
| | | +--ro location* inet:uri
| | +--ro feature* yang:yang-identifier
| | +--ro deviation* -> ../../module/name
| +--ro import-only-module* [name revision]
| +--ro name yang:yang-identifier
| +--ro revision union
| +--ro namespace inet:uri
| +--ro location* inet:uri
| +--ro submodule* [name]
| +--ro name yang:yang-identifier
| +--ro revision? revision-identifier
| +--ro location* inet:uri
+--ro schema* [name]
| +--ro name string
| +--ro module-set* -> ../../module-set/name
+--ro datastore* [name]
| +--ro name ds:datastore-ref
| +--ro schema -> ../../schema/name
+--ro checksum string
notifications:
+---n yang-library-update
+--ro checksum -> /yang-library/checksum
The "/yang-library" container holds the entire YANG library. The
container has the following child nodes:
o The "/yang-library/module-set" contains entries representing
module sets. The list "/yang-library/module-set/module"
enumerates the modules that belong to the module set. A module is
listed together with its submodules (if any), a set of features,
and any deviation modules. The list "/yang-library/module-set/
import-only-module" lists all modules (and their submodules) used
only for imports.
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o The "/yang-library/schema" list contains an entry for each
datastore schema supported by the server. All conventional
configuration datastores use the same "schema" list entry. A
dynamic configuration datastore may use a different datastore
schema from the conventional configuration datastores, and hence
may require a separate "schema" entry. A "schema" entry has a
leaf-list of references to entries in the "module-set" list. The
schema consists of the union of all modules in all referenced
module sets.
o The "/yang-library/datastore" list contains one entry for each
datastore supported by the server, and it identifies the datastore
schema associated with a datastore via a reference to an entry in
the "schema" list. Each supported conventional configuration
datastore has a separate entry, pointing to the same "schema" list
element.
o The "/yang-library/checksum" leaf contains the YANG library
checksum, which is a unique implementation-specific identifier
representing the current information in the YANG library on a
specific server. The value of this leaf MUST change whenever the
information in the YANG library changes. There is no requirement
that the same information always results in the same "checksum"
value. This leaf allows a client to fetch all schema information
once, cache it, and only refetch it if the value of this leaf has
been changed. If the value of this leaf changes, the server also
generates a "yang-library-update" notification.
Note that for a NETCONF server implementing the NETCONF extensions to
support the NMDA [I-D.ietf-netconf-nmda-netconf], a change of the
YANG library checksum results in a new value for the :yang-
library:1.1 capability defined in [I-D.ietf-netconf-nmda-netconf].
Thus, if such a server implements NETCONF notifications [RFC5277],
and the notification "netconf-capability-change" [RFC6470], a
"netconf-capability-change" notification is generated whenever the
YANG library checksum changes.
5. YANG Library YANG Module
The "ietf-yang-library" YANG module imports definitions from
"ietf-yang-types" and "ietf-inet-types" defined in [RFC6991] and from
"ietf-datastores" defined in [I-D.ietf-netmod-revised-datastores].
While the YANG module is defined using YANG version 1.1, the YANG
library supports the YANG modules written in any version of YANG.
RFC Ed.: update the date below with the date of RFC publication and
remove this note.
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<CODE BEGINS> file "ietf-yang-library@2018-02-21.yang"
module ietf-yang-library {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library";
prefix "yanglib";
import ietf-yang-types {
prefix yang;
reference "RFC 6991: Common YANG Data Types.";
}
import ietf-inet-types {
prefix inet;
reference "RFC 6991: Common YANG Data Types.";
}
import ietf-datastores {
prefix ds;
// RFC Ed.: update the reference below with the actual RFC number
reference "RFC XXXX: Network Management Datastore Architecture.";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Andy Bierman
<mailto:andy@yumaworks.com>
Author: Martin Bjorklund
<mailto:mbj@tail-f.com>
Author: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>
Author: Rob Wilton
<rwilton@cisco.com>";
description
"This module provides information about the YANG modules,
datastores, and datastore schemas used by a network
management server.
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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
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
// RFC Ed.: update the date below with the date of RFC publication
// and remove this note.
// RFC Ed.: replace XXXX with actual RFC number and remove this
// note.
revision 2018-02-21 {
description
"Added support for multiple datastores according to the
Network Management Datastore Architecture (NMDA).";
reference
"RFC XXXX: YANG Library.";
}
revision 2016-04-09 {
description
"Initial revision.";
reference
"RFC 7895: YANG Module Library.";
}
/*
* Typedefs
*/
typedef revision-identifier {
type string {
pattern '\d{4}-\d{2}-\d{2}';
}
description
"Represents a specific date in YYYY-MM-DD format.";
}
/*
* Groupings
*/
grouping module-identification-leafs {
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description
"Parameters for identifying YANG modules and submodules.";
leaf name {
type yang:yang-identifier;
mandatory true;
description
"The YANG module or submodule name.";
}
leaf revision {
type revision-identifier;
description
"The YANG module or submodule revision date. If no revision
statement is present in the YANG module or submodule, this
leaf is not instantiated.";
}
}
grouping location-leaf-list {
description
"Common location leaf list parameter for modules and
submodules.";
leaf-list location {
type inet:uri;
description
"Contains a URL that represents the YANG schema
resource for this module or submodule.
This leaf will only be present if there is a URL
available for retrieval of the schema for this entry.";
}
}
grouping implementation-parameters {
description
"Parameters for describing the implementation of a module.";
leaf-list feature {
type yang:yang-identifier;
description
"List of YANG feature names from this module that are
supported by the server, regardless whether they are defined
in the module or any included submodule.";
}
leaf-list deviation {
type leafref {
path "../../module/name";
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}
description
"List of YANG deviation modules used by this server to modify
the conformance of the module associated with this entry.
Note that the same module can be used for deviations for
multiple modules, so the same entry MAY appear within
multiple 'module' entries.
This reference MUST NOT (directly or indirectly)
refer to the module being deviated.
Robust clients may want to make sure that they handle a
situation where a module deviates itself (directly or
indirectly) gracefully.";
}
}
grouping module-set-parameters {
description
"A set of parameters that describe a module set.";
leaf name {
type string;
description
"An arbitrary name of the module set.";
}
list module {
key "name";
description
"An entry in this list represents a module implemented by the
server, as per RFC 7950 section 5.6.5, with a particular set
of supported features and deviations.";
reference
"RFC 7950: The YANG 1.1 Data Modeling Language.";
uses module-identification-leafs;
leaf namespace {
type inet:uri;
mandatory true;
description
"The XML namespace identifier for this module.";
}
uses location-leaf-list;
list submodule {
key "name";
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description
"Each entry represents one submodule within the
parent module.";
uses module-identification-leafs;
uses location-leaf-list;
}
uses implementation-parameters;
}
list import-only-module {
key "name revision";
description
"An entry in this list indicates that the server imports
reusable definitions from the specified revision of the
module, but does not implement any protocol accessible
objects from this revision.
Multiple entries for the same module name MAY exist. This
can occur if multiple modules import the same module, but
specify different revision-dates in the import statements.";
leaf name {
type yang:yang-identifier;
description
"The YANG module name.";
}
leaf revision {
type union {
type revision-identifier;
type string {
length 0;
}
}
description
"The YANG module revision date.
A zero-length string is used if no revision statement
is present in the YANG module.";
}
leaf namespace {
type inet:uri;
mandatory true;
description
"The XML namespace identifier for this module.";
}
uses location-leaf-list;
list submodule {
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key "name";
description
"Each entry represents one submodule within the
parent module.";
uses module-identification-leafs;
uses location-leaf-list;
}
}
}
grouping yang-library-parameters {
description
"The YANG library data structure is represented as a grouping
so it can be reused in configuration or another monitoring
data structure.";
list module-set {
key name;
description
"A set of modules that may be used by one or more schemas.
A module set does not have to be referentially complete,
i.e., it may define modules that contain import statements
for other modules not included in the module set.";
uses module-set-parameters;
}
list schema {
key "name";
description
"A datastore schema that may be used by one or more
datastores.
The schema must be valid and referentially complete, i.e.,
it must contain modules to satisfy all used import
statements for all modules specified in the schema.";
leaf name {
type string;
description
"An arbitrary name of the schema.";
}
leaf-list module-set {
type leafref {
path "../../module-set/name";
}
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description
"A set of module-sets that are included in this schema.
If a non import-only module appears in multiple module
sets, then the module revision and the associated features
and deviations must be identical.";
}
}
list datastore {
key "name";
description
"A datastore supported by this server.
Each datastore indicates which schema it supports.
The server MUST instantiate one entry in this list per
specific datastore it supports.
Each datstore entry with the same datastore schema SHOULD
reference the same schema.";
leaf name {
type ds:datastore-ref;
description
"The identity of the datastore.";
}
leaf schema {
type leafref {
path "../../schema/name";
}
mandatory true;
description
"A reference to the schema supported by this datastore.
All non import-only modules of the schema are implemented
with their associated features and deviations.";
}
}
}
/*
* Top-level container
*/
container yang-library {
config false;
description
"Container holding the entire YANG library of this server.";
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uses yang-library-parameters;
leaf checksum {
type string;
mandatory true;
description
"A server-generated checksum of the contents of the
'yang-library' tree. The server MUST change the value of
this leaf if the information represented by the
'yang-library' tree, except 'yang-library/checksum', has
changed.";
}
}
/*
* Notifications
*/
notification yang-library-update {
description
"Generated when any YANG library information on the
server has changed.";
leaf checksum {
type leafref {
path "/yanglib:yang-library/yanglib:checksum";
}
mandatory true;
description
"Contains the YANG library checksum for the updated YANG
library at the time the notification is generated.";
}
}
/*
* Legacy groupings
*/
grouping module-list {
status deprecated;
description
"The module data structure is represented as a grouping
so it can be reused in configuration or another monitoring
data structure.";
grouping common-leafs {
status deprecated;
description
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"Common parameters for YANG modules and submodules.";
leaf name {
type yang:yang-identifier;
status deprecated;
description
"The YANG module or submodule name.";
}
leaf revision {
type union {
type revision-identifier;
type string {
length 0;
}
}
status deprecated;
description
"The YANG module or submodule revision date.
A zero-length string is used if no revision statement
is present in the YANG module or submodule.";
}
}
grouping schema-leaf {
status deprecated;
description
"Common schema leaf parameter for modules and submodules.";
leaf schema {
type inet:uri;
description
"Contains a URL that represents the YANG schema
resource for this module or submodule.
This leaf will only be present if there is a URL
available for retrieval of the schema for this entry.";
}
}
list module {
key "name revision";
status deprecated;
description
"Each entry represents one revision of one module
currently supported by the server.";
uses common-leafs {
status deprecated;
}
uses schema-leaf {
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status deprecated;
}
leaf namespace {
type inet:uri;
mandatory true;
status deprecated;
description
"The XML namespace identifier for this module.";
}
leaf-list feature {
type yang:yang-identifier;
status deprecated;
description
"List of YANG feature names from this module that are
supported by the server, regardless whether they are
defined in the module or any included submodule.";
}
list deviation {
key "name revision";
status deprecated;
description
"List of YANG deviation module names and revisions
used by this server to modify the conformance of
the module associated with this entry. Note that
the same module can be used for deviations for
multiple modules, so the same entry MAY appear
within multiple 'module' entries.
The deviation module MUST be present in the 'module'
list, with the same name and revision values.
The 'conformance-type' value will be 'implement' for
the deviation module.";
uses common-leafs {
status deprecated;
}
}
leaf conformance-type {
type enumeration {
enum implement {
description
"Indicates that the server implements one or more
protocol-accessible objects defined in the YANG module
identified in this entry. This includes deviation
statements defined in the module.
For YANG version 1.1 modules, there is at most one
module entry with conformance type 'implement' for a
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particular module name, since YANG 1.1 requires that
at most one revision of a module is implemented.
For YANG version 1 modules, there SHOULD NOT be more
than one module entry for a particular module name.";
}
enum import {
description
"Indicates that the server imports reusable definitions
from the specified revision of the module, but does
not implement any protocol accessible objects from
this revision.
Multiple module entries for the same module name MAY
exist. This can occur if multiple modules import the
same module, but specify different revision-dates in
the import statements.";
}
}
mandatory true;
status deprecated;
description
"Indicates the type of conformance the server is claiming
for the YANG module identified by this entry.";
}
list submodule {
key "name revision";
status deprecated;
description
"Each entry represents one submodule within the
parent module.";
uses common-leafs {
status deprecated;
}
uses schema-leaf {
status deprecated;
}
}
}
}
/*
* Legacy operational state data nodes
*/
container modules-state {
config false;
status deprecated;
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description
"Contains YANG module monitoring information.";
leaf module-set-id {
type string;
mandatory true;
status deprecated;
description
"Contains a server-specific identifier representing
the current set of modules and submodules. The
server MUST change the value of this leaf if the
information represented by the 'module' list instances
has changed.";
}
uses module-list {
status deprecated;
}
}
/*
* Legacy notifications
*/
notification yang-library-change {
status deprecated;
description
"Generated when the set of modules and submodules supported
by the server has changed.";
leaf module-set-id {
type leafref {
path "/yanglib:modules-state/yanglib:module-set-id";
}
mandatory true;
status deprecated;
description
"Contains the module-set-id value representing the
set of modules and submodules supported at the server
at the time the notification is generated.";
}
}
}
<CODE ENDS>
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6. IANA Considerations
RFC 7895 previously registered one URI in the IETF XML registry
[RFC3688]. This document takes over this registration entry made by
RFC 7895 and changes the Registrant to the IESG according to
Section 4 in [RFC3688].
URI: urn:ietf:params:xml:ns:yang:ietf-yang-library
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
RFC 7895 previously registered one YANG module in the "YANG Module
Names" registry [RFC6020] as follows:
name: ietf-yang-library
namespace: urn:ietf:params:xml:ns:yang:ietf-yang-library
prefix: yanglib
reference: RFC 7895
This document takes over this registration entry made by RFC 7895.
7. Security Considerations
The YANG module specified in this document defines a schema for data
that is accessed by network management protocols such as NETCONF
[RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the
secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC5246].
The NETCONF access control model [RFC6536] provides the means to
restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.
Some of the readable data nodes in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or
notification) to these data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability:
The "/yang-library" subtree of the YANG library may help an attacker
identify the server capabilities and server implementations with
known bugs since the set of YANG modules supported by a server may
reveal the kind of device and the manufacturer of the device.
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Although some of this information may be available to all NETCONF
users via the NETCONF <hello> message (or similar messages in other
management protocols), this YANG module potentially exposes
additional details that could be of some assistance to an attacker.
Server vulnerabilities may be specific to particular modules, module
revisions, module features, or even module deviations. For example,
if a particular operation on a particular data node is known to cause
a server to crash or significantly degrade device performance, then
the module list information will help an attacker identify server
implementations with such a defect, in order to launch a denial-of-
service attack on the device.
8. Acknowledgments
Contributions to this material by Andy Bierman are based upon work
supported by the The Space & Terrestrial Communications Directorate
(S&TCD) under Contract No. W15P7T-13-C-A616. Any opinions, findings
and conclusions or recommendations expressed in this material are
those of the author(s) and do not necessarily reflect the views of
The Space & Terrestrial Communications Directorate (S&TCD).
9. References
9.1. Normative References
[I-D.ietf-netmod-revised-datastores]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore
Architecture", draft-ietf-netmod-revised-datastores-10
(work in progress), January 2018.
[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>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004, <https://www.rfc-
editor.org/info/rfc3688>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008, <https://www.rfc-editor.org/info/
rfc5246>.
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[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>.
[RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration
Protocol (NETCONF) Access Control Model", RFC 6536, DOI
10.17487/RFC6536, March 2012, <https://www.rfc-
editor.org/info/rfc6536>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC
6991, DOI 10.17487/RFC6991, July 2013, <https://www.rfc-
editor.org/info/rfc6991>.
[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>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
9.2. Informative References
[I-D.ietf-i2rs-yang-network-topo]
Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A Data Model for Network
Topologies", draft-ietf-i2rs-yang-network-topo-20 (work in
progress), December 2017.
[I-D.ietf-netconf-nmda-netconf]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "NETCONF Extensions to Support the Network
Management Datastore Architecture", draft-ietf-netconf-
nmda-netconf-03 (work in progress), February 2018.
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[I-D.ietf-netconf-nmda-restconf]
Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "RESTCONF Extensions to Support the Network
Management Datastore Architecture", draft-ietf-netconf-
nmda-restconf-02 (work in progress), January 2018.
[I-D.ietf-netmod-entity]
Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
YANG Data Model for Hardware Management", draft-ietf-
netmod-entity-08 (work in progress), January 2018.
[I-D.ietf-netmod-rfc7223bis]
Bjorklund, M., "A YANG Data Model for Interface
Management", draft-ietf-netmod-rfc7223bis-03 (work in
progress), January 2018.
[I-D.ietf-netmod-rfc7277bis]
Bjorklund, M., "A YANG Data Model for IP Management",
draft-ietf-netmod-rfc7277bis-03 (work in progress),
January 2018.
[I-D.ietf-netmod-rfc8022bis]
Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", draft-ietf-netmod-
rfc8022bis-11 (work in progress), January 2018.
[I-D.ietf-netmod-schema-mount]
Bjorklund, M. and L. Lhotka, "YANG Schema Mount", draft-
ietf-netmod-schema-mount-08 (work in progress), October
2017.
[I-D.ietf-netmod-yang-tree-diagrams]
Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft-
ietf-netmod-yang-tree-diagrams-06 (work in progress),
February 2018.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF)
Base Notifications", RFC 6470, DOI 10.17487/RFC6470,
February 2012, <https://www.rfc-editor.org/info/rfc6470>.
[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>.
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Appendix A. Summary of Changes from RFC 7895
This document updates [RFC7895] in the following ways:
o Renamed document title from "YANG Module Library" to "YANG
Library".
o Added a new top-level "/yang-library" container to hold the entire
YANG library providing information about module sets, schemas, and
datastores.
o Refactored the "/modules-state" container into a new
"/yang-library/module-set" list.
o Added a new "/yang-library/schema" list and a new "/yang-library/
datastore" list.
o Added a set of new groupings as replacements for the deprecated
groupings.
o Added a "yang-library-update" notification as a replacement for
the deprecated "yang-library-change" notification.
o Deprecated the "/modules-state" tree.
o Deprecated the "/module-list" grouping.
o Deprecated the "/yang-library-change" notification.
Appendix B. Example YANG Library Instance for a Basic Server
The following example shows the YANG Library of a basic server
implementing the "ietf-interfaces" [I-D.ietf-netmod-rfc7223bis] and
"ietf-ip" [I-D.ietf-netmod-rfc7277bis] modules in the <running>,
<startup>, and <operational> datastores and the "ietf-hardware"
[I-D.ietf-netmod-entity] module in the <operational> datastore.
Newlines in leaf values are added for formatting reasons.
<yang-library
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<module-set>
<name>config-modules</name>
<module>
<name>ietf-interfaces</name>
<revision>2018-01-09</revision> <!-- RFC Ed. update this -->
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<namespace>
urn:ietf:params:xml:ns:yang:ietf-interfaces
</namespace>
</module>
<module>
<name>ietf-ip</name>
<revision>2018-01-09</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-ip
</namespace>
</module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-yang-types
</namespace>
</import-only-module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-inet-types
</namespace>
</import-only-module>
</module-set>
<module-set>
<name>state-modules</name>
<module>
<name>ietf-hardware</name>
<revision>2018-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-hardware
</namespace>
</module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-inet-types
</namespace>
</import-only-module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-yang-types
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</namespace>
</import-only-module>
<import-only-module>
<name>iana-hardware</name>
<revision>2017-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:iana-hardware
</namespace>
</import-only-module>
</module-set>
<schema>
<name>config-schema</name>
<module-set>config-modules</module-set>
</schema>
<schema>
<name>state-schema</name>
<module-set>config-modules</module-set>
<module-set>state-modules</module-set>
</schema>
<datastore>
<name>ds:startup</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:running</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:operational</name>
<schema>state-schema</schema>
</datastore>
<checksum>75a43df9bd56b92aacc156a2958fbe12312fb285</checksum>
</yang-library>
Appendix C. Example YANG Library Instance for an Advanced Server
The following example extends the preceding Basic Server YANG Library
example, by using modules from [I-D.ietf-netmod-rfc8022bis] and
[I-D.ietf-i2rs-yang-network-topo], to illustrate a slightly more
advanced server that:
o Has a module with features only enabled in <operational>; the
"ietf-routing module" is supported in <running>, <startup>, and
<operational>, but the "multiple-ribs" and "router-id" features
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are only enabled in <operational>. Hence the "router-id" leaf may
be read but not configured.
o Supports a dynamic configuration datastore "example-ds-ephemeral",
with only the "ietf-network" and "ietf-network-topology" modules
configurable via a notional dynamic configuration protocol.
o Shows an example of datastore specific deviations. The module
"example-vendor-hardware-deviations" is included in the schema for
<operational> to remove data nodes that cannot be supported by the
server.
o Shows how module-sets can be used to organize related modules
together.
<yang-library
xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-library"
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"
xmlns:ex-ds-eph="urn:example:ds-ephemeral">
<module-set>
<name>config-state-modules</name>
<module>
<name>ietf-interfaces</name>
<revision>2018-01-09</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-interfaces
</namespace>
</module>
<module>
<name>ietf-ip</name>
<revision>2018-01-09</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-ip
</namespace>
</module>
<module>
<name>ietf-routing</name>
<revision>2018-01-25</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-routing
</namespace>
</module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-yang-types
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</namespace>
</import-only-module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-inet-types
</namespace>
</import-only-module>
</module-set>
<module-set>
<name>config-only-modules</name>
<module>
<name>ietf-routing</name>
<revision>2018-01-25</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-routing
</namespace>
</module>
</module-set>
<module-set>
<name>dynamic-config-state-modules</name>
<module>
<name>ietf-network</name>
<revision>2017-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-network
</namespace>
</module>
<module>
<name>ietf-network-topology</name>
<revision>2017-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-network-topology
</namespace>
</module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-inet-types
</namespace>
</import-only-module>
</module-set>
<module-set>
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<name>state-only-modules</name>
<module>
<name>ietf-hardware</name>
<revision>2018-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-hardware
</namespace>
<deviation>example-vendor-hardware-deviations</deviation>
</module>
<module>
<name>ietf-routing</name>
<revision>2018-01-25</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:ietf-routing
</namespace>
<feature>multiple-ribs</feature>
<feature>router-id</feature>
</module>
<module>
<name>example-vendor-hardware-deviations</name>
<revision>2018-01-31</revision>
<namespace>
urn:example:example-vendor-hardware-deviations
</namespace>
</module>
<import-only-module>
<name>ietf-inet-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-inet-types
</namespace>
</import-only-module>
<import-only-module>
<name>ietf-yang-types</name>
<revision>2013-07-15</revision>
<namespace>
urn:ietf:params:xml:ns:yang:ietf-yang-types
</namespace>
</import-only-module>
<import-only-module>
<name>iana-hardware</name>
<revision>2017-12-18</revision> <!-- RFC Ed. update this -->
<namespace>
urn:ietf:params:xml:ns:yang:iana-hardware
</namespace>
</import-only-module>
</module-set>
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<schema>
<name>config-schema</name>
<module-set>config-state-modules</module-set>
<module-set>config-only-modules</module-set>
</schema>
<schema>
<name>dynamic-config-schema</name>
<module-set>dynamic-config-state-modules</module-set>
</schema>
<schema>
<name>state-schema</name>
<module-set>config-state-modules</module-set>
<module-set>dynamic-config-state-modules</module-set>
<module-set>state-only-modules</module-set>
</schema>
<datastore>
<name>ds:startup</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ds:running</name>
<schema>config-schema</schema>
</datastore>
<datastore>
<name>ex-ds-eph:ds-ephemeral</name>
<schema>dynamic-config-schema</schema>
</datastore>
<datastore>
<name>ds:operational</name>
<schema>state-schema</schema>
</datastore>
<checksum>14782ab9bd56b92aacc156a2958fbe12312fb285</checksum>
</yang-library>
Authors' Addresses
Andy Bierman
YumaWorks
Email: andy@yumaworks.com
Martin Bjorklund
Tail-f Systems
Email: mbj@tail-f.com
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Juergen Schoenwaelder
Jacobs University
Email: j.schoenwaelder@jacobs-university.de
Kent Watsen
Juniper Networks
Email: kwatsen@juniper.net
Robert Wilton
Cisco Systems
Email: rwilton@cisco.com
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