Network Working Group                                         A. Bierman
Internet-Draft                                                 YumaWorks
Obsoletes: rfc7895 7895 (if approved)                               M. Bjorklund
Intended status: Standards Track                          Tail-f Systems
Expires: July 21, August 2, 2018                                 J. Schoenwaelder
                                                       Jacobs University
                                                               K. Watsen
                                                        Juniper Networks
                                                               R. Wilton
                                                           Cisco Systems
                                                        January 17, 29, 2018

                              YANG Library
                    draft-ietf-netconf-rfc7895bis-03
                    draft-ietf-netconf-rfc7895bis-04

Abstract

   This document describes a YANG library that provides information
   about all the YANG modules modules, datastores, and datastores datastore schemas used by a
   network management server (e.g., a Network Configuration Protocol (NETCONF)
   server). 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 July 21, August 2, 2018.

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
     1.1.
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Tree Diagrams . . . . . . . . . . . . .   3
   3.  Objectives  . . . . . . . . .   4
     1.3.  Motivation for rfc7895bis . . . . . . . . . . . . . . . .   4
     1.4.  Summary of Changes from RFC 7895  . . . . . . . . . . . .   6
   2.
   4.  YANG Library  . . . . . Data Model . . . . . . . . . . . . . . . . . . .   6
     2.1.  yang-library  . . . . . . . . . . . . . . . . . . . . . .   7
       2.1.1.  yang-library/checksum . . . . . . . . . . . . . . . .   7
       2.1.2.  yang-library/datastore  . . . . . . . . . . . . . . .   8
       2.1.3.  yang-library/schema . . . . . . . . . . . . . .
   5.  YANG Library YANG Module  . . .   8
       2.1.4.  yang-library/module-set . . . . . . . . . . . . . . .   8
       2.1.5.  yang-library/module-set/module  . . . . . .
   6.  IANA Considerations . . . . .   9
       2.1.6.  yang-library/module-set/import-only-module . . . . .   9
     2.2.  YANG Library Module . . . . . . . . . . .  21
   7.  Security Considerations . . . . . . . .   9
   3.  IANA Considerations . . . . . . . . . . .  21
   8.  Acknowledgements  . . . . . . . . . .  21
     3.1.  YANG Module Registry . . . . . . . . . . . .  22
   9.  References  . . . . . .  21
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   5.  Acknowledgements  . . . .
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  22
   6.
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     6.1.  Normative References  . . . . . . . . .
   Appendix A.  Summary of Changes from RFC 7895 . . . . . . . . .  23
     6.2.  Informative References .  25
   Appendix B.  Example YANG Library Instance for a Basic Server . .  25
   Appendix C.  Example YANG Library Instance for an Advanced Server  28
   Authors' Addresses  . . . . . . . . . . . . . .  24
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .  24  32

1.  Introduction

   There is a need for a standard mechanisms mechanism to provide the operational
   state of a network management server.  This includes, for instance,
   identifying the expose which YANG modules and
   [RFC7950], datastores that and datastore schemas
   [I-D.ietf-netmod-revised-datastores] are in use by a
   server and how they relate to each other. network
   management server.

   This document defines a the YANG module "ietf-yang-library" that can be used to provide
   provides this
   informaton, informaton.  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 a way that [RFC7895], is not compatible with the NMDA
   [I-D.ietf-netmod-revised-datastores], but
   since it assumes that all datastores have exactly the same schema.
   This is also backwards
   compatible with not necessarily true in the "YANG Module Library" NMDA since dynamic configuration
   datastores may have their own datastore schema.  Furthermore, the
   operational state datastore may support non-configurable YANG module defined modules
   in
   [RFC7895].

   If a large number of addition to the YANG modules are utilized supported by the server, then
   the conventional
   configuration datastores.

   The old YANG library contents needed can definitions have been retained (for backwards
   compability reasons) but the definitions have been marked as
   deprecated.  For backwards compatability, an NMDA-supporting server
   SHOULD populate the deprecated "/modules-state" tree in a backwards-
   compatible manner.  The new "/yang-library" tree would be relatively large.  This
   information changes very infrequently, so it 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 important that
   clients be able to cache report the
   schema for YANG library contents modules that are configurable via conventional
   datastores and easily
   identify whether their cache is out of date. 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 the a server
   implements multiple network management protocols to access the YANG-
   defined data,
   server's datastores, then each such protocol has may have its own
   conceptual instantiation of the YANG library.

   The following information is needed by

   If a client application (for each large number of YANG module in the library) to fully utilize modules are utilized by a server, then the
   YANG data modeling
   language:

   o  identifier: a unique identifier for library contents can be relatively large.  Since the module YANG
   library contents changes very infrequently, it is important that includes
   clients be able to cache the
      module's name, revision, submodules, features, YANG library contents and deviations.

   o  name: The name easily
   identify whether their cache is out of the date.

   All NETCONF servers supporting YANG module.

   o  revision: Each 1.1 [RFC7950] are required to
   support YANG module and submodule within Library (see Section 5.6.4 of RFC 7950).  NETCONF
   servers implementing the library SHOULD
      have a revision.  This is derived from NETCONF extensions to support the most recent revision
      statement within NMDA
   [I-D.ietf-netconf-nmda-netconf] must implement at least the module or submodule.

   o  submodule list: The name, and if defined, revision version
   of each
      submodule used by the module MUST be identified.

   o  feature list: The name of each YANG feature supported by the
      server, library defined in a given datastore schema, MUST be identified.

   o  deviation list: The name of each this document.  Similarly, all
   RESTCONF servers are required to support YANG module used for deviation
      statements, in a given datastore schema, MUST be identified.

   The following information is needed by a client application (for each
   datastore supported by Library (see Section 10
   of RFC 8040).  RESTCONF servers implementing the server) RESTCONF extensions
   to fully access all support the YANG-
   modelled data available on NMDA [I-D.ietf-netconf-nmda-restconf] must implement
   at least the server:

   o  identity: version of the YANG identity for the datastore.

   o  modules: modules supported by the datastore, including any
      features and deviations.

1.1.  Terminology 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
   o  submodule

   o  data node

   The following terms are defined in
   [I-D.ietf-netmod-revised-datastores]:

   o  conventional configuration  datastore

   o  operational state  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 schema

   o  client

   o and server

1.2.  Tree Diagrams

   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 follow use the notation defined in
   [I-D.ietf-netmod-yang-tree-diagrams].

1.3.  Motivation for rfc7895bis

   RFC Ed.: delete this section, including this note, at time of
   publication.

   All NETCONF servers supporting

3.  Objectives

   The following information is needed by a client application (for each
   YANG 1.1 [RFC7950] are required module in the library) to
   support fully utilize the YANG Library (see Section 5.6.4 data modeling
   language:

   o  name: The name of RFC 7950).  Similarly, all
   RESTCONF servers are required to support the YANG Library (see Section 10
   of RFC 8040).  These requirements are independent of if module.

   o  revision: Each YANG module and submodule within the server
   supports NMDA or not.

   RFC 7895 has a mandatory to implement "modules-state" tree that library SHOULD
      have a
   server uses to advertise all revision.  This is derived from the modules it supports.  However, this
   module was designed assuming most recent revision
      statement within the all modules would be in all
   datastores, module or submodule.

   o  submodule list: The name, and with if defined, revision of each
      submodule used by the same number module MUST be identified.

   o  feature list: The name of features and deviations.
   However, this is not each YANG feature supported by the case with NMDA-compatible servers that may
   have some modules that only appear in <operational> (e.g., ietf-
   network-topo) or only also appear
      server, in a dynamic given datastore (e.g., i2rs-
   ephemeral-rib).  It is also possible that a server only implements a
   module in <running>, as it hasn't yet coded support schema, MUST be identified.

   o  deviation list: The name of each YANG module used for returning the
   module's opstate yet.  Presumably, an NMDA-supporting server would
   return all modules implemented deviation
      statements, in every datastore, but this would a given datastore schema, MUST be
   misleading to existing clients and unhelpful to NMDA-aware clients. identified.

   In addition, the end, it appears that the "modules-state" node should be following information is needed by a client
   application for
   non-NMDA aware clients.  For backwards compatability, an NMDA-
   supporting server SHOULD populate "modules-state" in each datastore supported by a backwards-
   compatible manner. server:

   o  identity: The new "yang-library" node would be ignored YANG identity for the datastore.

   o  schema: The schema (i.e., the set of modules) implemented by
   legacy clients, while providing all the
      datastore.

   In order to select one out of several possible data needed for NMDA-aware
   clients, which would themselves ignore model designs,
   the "modules-state" tree.

   Design objectives: following criteria were used:

   1.  As efficient as possible  Efficient for a client to consume.  Since the size of the yang YANG
       library can be quite large, it should be possible for clients to
       cache the yang 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.

   6.  Nice to have: make  Make it possible to be used use the YANG library by schema mount
       [I-D.ietf-netmod-schema-mount].

4.  YANG Library Data Model

   The solution presented in this document is further motivated by "ietf-yang-library" YANG module provides information about the
   following desires:

   o  leverage Section 5.6.4 of RFC 7950
   modules, submodules, datastores, and Section 10 of RFC 8040.

   o  indicate which modules are supported by each datastore

   o  enable the features and deviations to vary schemas supported by datastore

   o  structure extensible to support schema-mount

   o  provide a top-level container for all server metadata

1.4.  Summary of Changes from RFC 7895

   This document updates [RFC7895]
   server.  All data nodes in "ietf-yang-library" are "config false",
   and thus only accessible in the following ways:

   o  Renames document title from "YANG Module Library" to "YANG
      Library".

   o  Adds operational state datastore.

   +-----------+
   | datastore |
   +-----------+
        |
        | has a new top-level "yang-library" container to hold many types
        V
   +-----------+            +--------+                +------------+
   | datastore |  union of server metadata:  | module |  consists of   | modules supported, datastores supported,
      relationships between datastores and modules, etc.

   o  Adds a +  |
   |  schema   |----------->|  set of new groupings as replacements for the deprecated
      "module-list" grouping.

   o  Adds a "yang-library-update" notification as a replacement for the
      deprecated "yang-library-change" notification.

   o  Deprecates the "modules-state" tree.

   o  Deprecates the "module-list" grouping.

   o  Deprecates   |--------------->| submodules |
   +-----------+            +--------+                +------------+

                                 Figure 1

   The conceptual model of the "yang-library-change" notification.

2. YANG Library

   The "ietf-yang-library" module provides information about library is depicted in Figure 1.
   Following the modules
   and datastores supported by NMDA, every datastore has an associated datastore
   schema.  A datastore schema is a server.  This union of module sets and every
   module set is defined using
   YANG version 1.1, but it supports the description a collection of YANG modules
   written in any revision of YANG.

   All data nodes in "ietf-yang-library" are "config false", and thus
   accessible in 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 schema share module sets.  A
   common use case is the operational state datastore.

   Following 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:

   module: ietf-yang-library
     +--ro yang-library
        +--ro module-set* [name]
        |  +--ro name                  string
        |  +--ro checksum              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* [name]
        |  |  |  +--ro name    yang:yang-identifier
        |  |  +--ro deviation* [module]
        |  |     +--ro module    -> ../../name ../../../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 checksum      string
        |  +--ro module-set*   -> ../../module-set/name
        +--ro datastore* [name]
        |  +--ro name      identityref      ds:datastore-ref
        |  +--ro schema    -> ../../schema/name
        +--ro checksum      string

     notifications:
       +---n yang-library-update

2.1.  yang-library

   This
          +--ro checksum    -> /yang-library/checksum

   The "/yang-library" container holds all of the server's metadata.

2.1.1.  yang-library/checksum

   This mandatory leaf entire YANG library.  The
   container has the following child nodes:

   o  The "/yang-library/module-set" contains a unique implementation-specific
   identifier entries representing
      module sets.  The list "/yang-library/module-set/module"
      enumerates the current information in modules that belong to the YANG library
   on module set.  A module is
      listed together with its submodules (if any), a specific server.  The value set of this leaf MUST change whenever
   the the information in features,
      and any deviation modules.  The list "/yang-library/module-set/
      import-only-module" lists all modules (and their submodules) used
      only for imports.

   o  The "/yang-library/schema" list contains an entry for each
      datastore schema supported by the YANG library changes.  There is no
   requirement that 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 that implements YANG 1.1 [RFC7950], implementing the NETCONF extensions to
   support the NMDA [I-D.ietf-netconf-nmda-netconf], a change of the "checksum" value
   YANG library checksum results in a new value for the :yang-
   library
   library:1.1 capability defined in [RFC7950]. [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 "checksum"
   YANG library checksum changes.

2.1.2.  yang-library/datastore

   This list contains one entry for each datastore supported by the
   server,

5.  YANG Library YANG Module

   The "ietf-yang-library" YANG module imports definitions from
   "ietf-yang-types" and identifies the datastore schema associated with a
   datastore via a reference to an entry "ietf-inet-types" defined in [RFC6991] and from
   "ietf-datastores" defined in [I-D.ietf-netmod-revised-datastores].
   While the "schema" list.  Each
   supported conventional configuration datastore has a separate entry.

2.1.3.  yang-library/schema

   An entry 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 "schema" list represents the datastore schema that is
   used by one or more datastores.

   This list contains one entry for each schema in use by the server
   (e.g., presented by a datastore).

   All conventional configuration datastores and the operational state
   datastore use the same "schema" 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 has a leaf-list with references to entries in the
   "module-set" list.  The schema consists of the sum of all modules in
   all referenced module sets.

2.1.4.  yang-library/module-set
2.1.5.  yang-library/module-set/module

2.1.6.  yang-library/module-set/import-only-module

2.2.  YANG Library Module

   The "ietf-yang-library" module defines monitoring information for the
   YANG modules used by a server.

   The modules "ietf-yang-types" and "ietf-inet-types" from [RFC6991]
   and the module "ietf-datastores" from
   [I-D.ietf-netmod-revised-datastores] are used by this module for some
   type definitions.

   RFC Ed.: update the date below with date below with the date of RFC publication and
   remove this note.

   <CODE BEGINS> file "ietf-yang-library@2018-01-17.yang" "ietf-yang-library@2018-01-26.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;
      reference "I-D.ietf-revised-datastores:
                 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 contains provides information about the YANG server instance,
        including the modules and datastores the server supports, modules,
       datastores, and
        which modules are present in which datastores. datastore schemas used by a network
       management server.

       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 2018-01-17 2018-01-26 {
      description
        "Added support for multiple datastores."; 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 {
      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.";

      list feature {
        key "name";
        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 name {
          type yang:yang-identifier;
          description
            "A feature supported by the server.";

        }
      }
      list deviation {
        key "module";
        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.";

        leaf module {
          type leafref {
            path "../../name"; "../../../module/name";
          }
          description
            "A module that deviates the module associated with this
              entry.";
             entry.

             While this reference MUST NOT be directly or indirectly
             self-referential, clients must make sure that they
             handle such a situation 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.";
      }
       leaf checksum {
         type string;
         config false;
         mandatory true;
         description
           "A server-generated checksum of the contents of the module
            set.  The server MUST change the value of this leaf if the
            information represented by the module set, except
            'checksum', has changed.";
       }
      list module {
        key "name";
        description
          "An entry in this list represents a module implemented by the
           server with a particular set of supported features and
           deviations.

           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.";

        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";
          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 or 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 {
          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."; 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.";

         leaf name {
           type string;
           description
             "An arbitrary name of
           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.";
         } schema";

        leaf checksum name {
          type string;
           config false;
           mandatory true;
          description
             "A server-generated checksum of the contents of the schema.
              The server MUST change the value
            "An arbitrary name of this leaf if the
              information represented by the schema, except 'checksum',
              has changed."; schema.";
        }
        leaf-list module-set {
          type leafref {
            path "../../module-set/name";
          }
          description
            "A set of module-sets that are included in this schema."; schema.
             If a non-import 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 identityref {
             base ds:datastore;
           } 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."; datastore.
             All non-import modules of the schema are implemented
             with their associated features and deviations.";
        }
      }

    }

    /*
     * Top-level container
     */

    container yang-library {
      config false;
      description
        "Container providing all holding the entire YANG meta information the
          server possesses."; library of this server.";

      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
          "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 {
          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
                 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;
      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>

3.

6.  IANA Considerations

3.1.  YANG Module Registry

   RFC 7895 previously registered one URI in the IETF XML registry
   [RFC3688].  Following the format in  This document takes over this registration entry made by
   RFC 3688, 7895 and changes the following
   registration was made: Registrant to the IESG according to
   Section 4 in [RFC3688].

     URI: urn:ietf:params:xml:ns:yang:ietf-yang-library

     Registrant Contact: The NETCONF WG of the IETF. IESG.

     XML: N/A, the requested URI is an XML namespace.

   This document takes over this registration entry made by RFC 7895.

   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.

4.

7.  Security Considerations

   The YANG module defined specified in this document defines a schema for data
   that is designed to be accessed
   via 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:

   o  /yang-library/schema:

   The schema list used in a server
      implementation "/yang-library" subtree of the YANG library may help an attacker
   identify the server capabilities and server implementations with
   known bugs. bugs since the set of YANG modules supported by a server may
   reveal the kind of device and the manufacturer of the device.
   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.  This
      information is included in each module entry.  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 denial-of-
   service attack on the device.

5.

8.  Acknowledgements

   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).

6.

9.  References

6.1.

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>.

   [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>.

6.2.

9.2.  Informative References

   [I-D.ietf-netmod-yang-tree-diagrams]
              Bjorklund, M.

   [I-D.ietf-i2rs-yang-network-topo]
              Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and L. Berger, "YANG Tree Diagrams", draft-
              ietf-netmod-yang-tree-diagrams-04 X. Liu, "A Data Model for Network
              Topologies", draft-ietf-i2rs-yang-network-topo-20 (work in
              progress), December 2017.

   [RFC5277]  Chisholm, S. and H. Trevino, "NETCONF Event

   [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-02 (work in progress), January 2018.

   [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-05 (work in progress),
              January 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>.

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 -->
         <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
         </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 Libary
   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
      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
         </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>
       <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>
       </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>
           <name>multiple-ribs</name>
         </feature>
         <feature>
           <name>router-id</name>
         </feature>
       </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>

     <module-set>
       <name>state-only-vendor-deviation-modules</name>
       <module>
         <name>example-vendor-hardware-deviations</name>
         <revision>2018-01-31</revision> <!-- RFC Ed. update this -->
         <namespace>
           urn:example:example-vendor-hardware-deviations
         </namespace>
       </module>
     </module-set>

     <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>
       <module-set>state-only-vendor-deviation-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

   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