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RFC 8530

YANG Model for Logical Network Elements

Pages: 49
Proposed STD
Part 1 of 3 – Pages 1 to 16
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Internet Engineering Task Force (IETF)                         L. Berger
Request for Comments: 8530                                      C. Hopps
Category: Standards Track                        LabN Consulting, L.L.C.
ISSN: 2070-1721                                                A. Lindem
                                                           Cisco Systems
                                                           D. Bogdanovic
                                                                  X. Liu
                                                          Volta Networks
                                                              March 2019

                YANG Model for Logical Network Elements


   This document defines a logical network element (LNE) YANG module
   that is compliant with the Network Management Datastore Architecture
   (NMDA).  This module can be used to manage the logical resource
   partitioning that may be present on a network device.  Examples of
   common industry terms for logical resource partitioning are logical
   systems or logical routers.  The YANG model in this document conforms
   with NMDA as defined in RFC 8342.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
Top   ToC   Page 2
Copyright Notice

   Copyright (c) 2019 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
   ( 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Logical Network Elements  . . . . . . . . . . . . . . . . . .   5
     3.1.  LNE Instantiation and Resource Assignment . . . . . . . .   6
     3.2.  LNE Management -- LNE View  . . . . . . . . . . . . . . .   7
     3.3.  LNE Management -- Host Network Device View  . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Logical Network Element Model . . . . . . . . . . . . . . . .  10
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  17
     A.1.  Example: Host-Device-Managed LNE  . . . . . . . . . . . .  17
       A.1.1.  Configuration Data  . . . . . . . . . . . . . . . . .  21
       A.1.2.  State Data  . . . . . . . . . . . . . . . . . . . . .  25
     A.2.  Example: Self-Managed LNE . . . . . . . . . . . . . . . .  33
       A.2.1.  Configuration Data  . . . . . . . . . . . . . . . . .  36
       A.2.2.  State Data  . . . . . . . . . . . . . . . . . . . . .  39
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  49
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  49
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1.  Introduction

   This document defines an NMDA-compliant YANG module [RFC6020] to
   support the creation of logical network elements (LNEs) on a network
   device.  An LNE is an independently managed virtual device made up of
   resources allocated to it from the host or parent network device.  An
   LNE running on a host network device conceptually parallels a virtual
   machine running on a host system.  Using host-virtualization
   terminology, one could refer to an LNE as a "Guest" and the
   containing network device as the "Host".  While LNEs may be
   implemented via host-virtualization technologies, this is not a
   requirement.  The YANG model in this document conforms with the
   Network Management Datastore Architecture defined in [RFC8342].

   This document also defines the necessary augmentations for allocating
   host resources to a given LNE.  As the interface management model
   [RFC8343] is the only module that currently defines host resources,
   this document currently defines only a single augmentation to cover
   the assignment of interfaces to an LNE.  Future modules that define
   support for the control of host device resources are expected to,
   where appropriate, provide parallel support for the assignment of
   controlled resources to LNEs.

   As each LNE is an independently managed device, each will have its
   own set of YANG-modeled data that is independent of the host device
   and other LNEs.  For example, multiple LNEs may all have their own
   "Tunnel0" interface defined, which will not conflict with each other
   and will not exist in the host's interface model.  An LNE will have
   its own management interfaces, possibly including independent
   instances of NETCONF/RESTCONF/etc servers to support the
   configuration of their YANG models.  As an example of this
   independence, an implementation may choose to completely rename
   assigned interfaces; so, on the host, the assigned interface might be
   called "Ethernet0/1" while within the LNE it might be called "eth1".

   In addition to standard management interfaces, a host device
   implementation may support accessing LNE configuration and
   operational YANG models directly from the host system.  When
   supported, such access is accomplished through a yang-schema-mount
   mount point [RFC8528] under which the root-level LNE YANG models may
   be accessed.

   Examples of vendor terminology for an LNE include logical system or
   logical router and virtual switch, chassis, or fabric.
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1.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   Readers are expected to be familiar with terms and concepts of YANG
   [RFC7950] and YANG Schema Mount [RFC8528].

   This document uses the graphical representation of data models
   defined in YANG Tree Diagrams [RFC8340].

2.  Overview

   In this document, we consider network devices that support protocols
   and functions defined within the IETF Routing Area, e.g., routers,
   firewalls, and hosts.  Such devices may be physical or virtual, e.g.,
   a classic router with custom hardware or one residing within a
   server-based virtual machine implementing a virtual network function
   (VNF).  Each device may subdivide their resources into LNEs, each of
   which provides a managed logical device.  Examples of vendor
   terminology for an LNE include logical system or logical router and
   virtual switch, chassis, or fabric.  Each LNE may also support VPN
   Routing and Forwarding (VRF) and Virtual Switching Instance (VSI)
   functions, which are referred to below as Network Instances (NIs).
   This breakdown is represented in Figure 1.

              |      Network Device (Physical or Virtual)     |
              | .....................   ..................... |
              | :  Logical Network  :   :  Logical Network  : |
              | :      Element      :   :      Element      : |
              | :+-----+-----+-----+:   :+-----+-----+-----+: |
              | :| Net | Net | Net |:   :| Net | Net | Net |: |
              | :|Inst.|Inst.|Inst.|:   :|Inst.|Inst.|Inst.|: |
              | :+-----+-----+-----+:   :+-----+-----+-----+: |
              | :  | |   | |   | |  :   :  | |   | |   | |  : |
              | :..|.|...|.|...|.|..:   :..|.|...|.|...|.|..: |
              |    | |   | |   | |         | |   | |   | |    |
                   | |   | |   | |         | |   | |   | |
                      Interfaces              Interfaces

                     Figure 1: Module Element Relationships
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   A model for LNEs is described in Section 3, and the model for NIs is
   covered in [RFC8529].

   The interface management model [RFC8343] is an existing model that is
   impacted by the definition of LNEs and NIs.  This document and
   [RFC8529] define augmentations to the interface model to support LNEs
   and NIs.  Similar elements, although perhaps only for LNEs, may also
   need to be included as part of the definition of the future hardware
   and QoS modules.

   Interfaces are a crucial part of any network device's configuration
   and operational state.  They generally include a combination of raw
   physical interfaces, link-layer interfaces, addressing configuration,
   and logical interfaces that may not be tied to any physical
   interface.  Several system services, and Layer 2 and Layer 3
   protocols, may also associate configuration or operational state data
   with different types of interfaces (these relationships are not shown
   for simplicity).  The interface management model is defined by
   [RFC8343].  The logical-network-element module augments existing
   interface management models by adding an identifier that is used on
   interfaces to identify an associated LNE.

   The interface-related augmentation is as follows:

       module: ietf-logical-network-element
         augment /if:interfaces/if:interface:
           +--rw bind-lne-name?   ->

   The interface model defined in [RFC8343] is structured to include all
   interfaces in a flat list, without regard to logical assignment of
   resources supported on the device.  The bind-lne-name and leaf
   provides the association between an interface and its associated LNE.
   Note that as currently defined, to assign an interface to both an LNE
   and NI, the interface would first be assigned to the LNE and then
   within that LNE's interface model, the LNE's representation of that
   interface would be assigned to an NI using the mechanisms defined in

3.  Logical Network Elements

   Logical network elements support the ability of some devices to
   partition resources into independent logical routers and/or switches.
   Device support for multiple logical network elements is
   implementation specific.  Systems without such capabilities need not
   include support for the logical-network-element module.  In physical
   devices, some hardware features are shared across partitions, but
   control-plane (e.g., routing) protocol instances, tables, and
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   configuration are managed separately.  For example, in logical
   routers or VNFs, this may correspond to establishing multiple logical
   instances using a single software installation.  The model supports
   configuration of multiple instances on a single device by creating a
   list of logical network elements, each with their own configuration
   and operational state related to routing and switching protocols.

   The LNE model can be represented as:

   module: ietf-logical-network-element
     +--rw logical-network-elements
        +--rw logical-network-element* [name]
           +--rw name           string
           +--rw managed?       boolean
           +--rw description?   string
           +--mp root
     augment /if:interfaces/if:interface:
       +--rw bind-lne-name?
             -> /logical-network-elements/logical-network-element/name

       +---n bind-lne-name-failed
          +--ro name             -> /if:interfaces/interface/name
          +--ro bind-lne-name
          |       -> /if:interfaces/interface/lne:bind-lne-name
          +--ro error-info?      string

   'name' identifies the logical network element.  'managed' indicates
   if the server providing the host network device will provide the
   client LNE information via the 'root' structure.  The root of an
   LNE's specific data is the schema mount point 'root'.  bind-lne-name
   is used to associate an interface with an LNE, and bind-lne-name-
   failed is used in certain failure cases.

   An LNE root MUST contain at least the YANG library [RFC7895] and
   interface module [RFC8343].

3.1.  LNE Instantiation and Resource Assignment

   Logical network elements may be controlled by clients using existing
   list operations.  When list entries are created, a new LNE is
   instantiated.  The models mounted under an LNE root are expected to
   be dependent on the server implementation.  When a list entry is
   deleted, an existing LNE is destroyed.  For more information, see
   [RFC7950], Section 7.8.6.

   Once instantiated, host network device resources can be associated
   with the new LNE.  As previously mentioned, this document augments
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   ietf-interfaces with the bind-lne-name leaf to support such
   associations for interfaces.  When a bind-lne-name is set to a valid
   LNE name, an implementation MUST take whatever steps are internally
   necessary to assign the interface to the LNE or provide an error
   message (defined below) with an indication of why the assignment
   failed.  It is possible for the assignment to fail while processing
   the set, or after asynchronous processing.  Error notification in the
   latter case is supported via a notification.

   On a successful interface assignment to an LNE, an implementation
   MUST also make the resource available to the LNE by providing a
   system-created interface to the LNE.  The name of the system-created
   interface is a local matter and may be identical or completely
   different and mapped from and to the name used in the context of the
   host device.  The system-created interface SHOULD be exposed via the
   LNE-specific instance of the interface model [RFC8343].

3.2.  LNE Management -- LNE View

   Each LNE instance is expected to support management functions from
   within the context of the LNE root, via a server that provides
   information with the LNE's root exposed as the device root.
   Management functions operating within the context of an LNE are
   accessed through the LNE's standard management interfaces, e.g.,
   NETCONF and SNMP.  Initial configuration, much like the initial
   configuration of the host device, is a local implementation matter.

   When accessing an LNE via the LNE's management interface, a network
   device representation will be presented, but its scope will be
   limited to the specific LNE.  Normal YANG/NETCONF mechanisms,
   together with the required YANG library [RFC7895] instance, can be
   used to identify the available modules.  Each supported module will
   be presented as a top-level module.  Only LNE-associated resources
   will be reflected in resource-related modules, e.g., interfaces,
   hardware, and perhaps QoS.  From the management perspective, there
   will be no difference between the available LNE view (information)
   and a physical network device.

3.3.  LNE Management -- Host Network Device View

   There are multiple implementation approaches possible to enable a
   network device to support the logical-network-element module and
   multiple LNEs.  Some approaches will allow the management functions
   operating at the network device level to access LNE configuration and
   operational information, while others will not.  Similarly, even when
   LNE management from the network device is supported by the
   implementation, it may be prohibited by user policy.
Top   ToC   Page 8
   Independent of the method selected by an implementation, the
   'managed' boolean mentioned above is used to indicate when LNE
   management from the network device context is possible.  When the
   'managed' boolean is 'false', the LNE cannot be managed by the host
   system and can only be managed from within the context of the LNE as
   described in Section 3.2.  Attempts to access information below a
   root node whose associated 'managed' boolean is set to 'false' MUST
   result in the error message indicated below.  In some
   implementations, it may not be possible to change this value.  For
   example, when an LNE is implemented using virtual machine and
   traditional hypervisor technologies, it is likely that this value
   will be restricted to a 'false' value.

   It is an implementation choice if the information can be accessed and
   modified from within the context of the LNE, or even the context of
   the host device.  When the 'managed' boolean is 'true', LNE
   information SHALL be accessible from the context of the host device.
   When the associated schema-mount definition has the 'config' leaf set
   to 'true', then LNE information SHALL also be modifiable from the
   context of the host device.  When LNE information is available from
   both the host device and from within the context of the LNE, the same
   information MUST be made available via the 'root' element, with paths
   modified as described in [RFC8528].

   An implementation MAY represent an LNE's schema using either the
   'inline' or the 'shared-schema' approaches defined in [RFC8528].  The
   choice of which to use is completely an implementation choice.  The
   inline approach is anticipated to be generally used in the cases
   where the 'managed' boolean will always be 'false'.  The 'shared-
   schema' approach is expected to be most useful in the case where all
   LNEs share the same schema.  When 'shared-schema' is used with an LNE
   mount point, the YANG library rooted in the LNE's mount point MUST
   match the associated schema defined according to the ietf-yang-
   schema-mount module.

   Beyond the two modules that will always be present for an LNE, as an
   LNE is a network device itself, all modules that may be present at
   the top-level network device MAY also be present for the LNE.  The
   list of available modules is expected to be implementation dependent,
   as is the method used by an implementation to support LNEs.
   Appendix A provides example uses of LNEs.
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4.  Security Considerations

   The YANG modules specified in this document define a schema for data
   that is designed to be accessed via 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

   The Network Configuration Access Control Model (NACM) [RFC8341]
   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.

   LNE information represents device and network configuration
   information.  As such, the security of this information is important,
   but it is fundamentally no different than any other interface or
   device configuration information that has already been covered in
   other documents such as [RFC8343], [RFC7317], and [RFC8349].

   The vulnerable "config true" parameters and subtrees are the

   /logical-network-elements/logical-network-element:  This list
      specifies the logical network element and the related logical
      device configuration.

   /logical-network-elements/logical-network-element/managed:  While
      this leaf is contained in the previous list, it is worth
      particular attention as it controls whether information under the
      LNE mount point is accessible by both the host device and within
      the LNE context.  There may be extra sensitivity to this leaf in
      environments where an LNE is managed by a different party than the
      host device, and that party does not wish to share LNE information
      with the operator of the host device.

   /if:interfaces/if:interface/bind-lne-name:  This leaf indicates the
      LNE instance to which an interface is assigned.  Implementations
      should pay particular attention to when changes to this leaf are
      permitted as removal of an interface from an LNE can have a major
      impact on the LNE's operation as it is similar to physically
      removing an interface from the device.  Implementations can reject
      a reassignment using the previously described error message
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   Unauthorized access to any of these lists can adversely affect the
   security of both the local device and the network.  This may lead to
   network malfunctions, delivery of packets to inappropriate
   destinations, and other problems.

5.  IANA Considerations

   This document registers a URI in the "IETF XML Registry" [RFC3688].

        URI: urn:ietf:params:xml:ns:yang:ietf-logical-network-element
        Registrant Contact: The IESG.
        XML: N/A, the requested URI is an XML namespace.

   This document registers a YANG module in the "YANG Module Names"
   registry [RFC6020].

   name:        ietf-logical-network-element
   namespace:   urn:ietf:params:xml:ns:yang:ietf-logical-network-element
   prefix:      lne
   reference:   RFC 8530

6.  Logical Network Element Model

   The structure of the model defined in this document is described by
   the YANG module below.

 <CODE BEGINS> file "ietf-logical-network-element@2019-01-25.yang"
 module ietf-logical-network-element {
   yang-version 1.1;

   // namespace

   namespace "urn:ietf:params:xml:ns:yang:ietf-logical-network-element";
   prefix lne;

   // import some basic types

   import ietf-interfaces {
     prefix if;
       "RFC 8343: A YANG Data Model for Interface Management";
   import ietf-yang-schema-mount {
     prefix yangmnt;
       "RFC 8528: YANG Schema Mount";
Top   ToC   Page 11
     "IETF Routing Area (rtgwg) Working Group";
     "WG Web:   <>
      WG List:  <>

      Author:   Lou Berger

      Author:   Christian Hopps

      Author:   Acee Lindem

      Author:   Dean Bogdanovic
     "This module is used to support multiple logical network
      elements on a single physical or virtual system.

      Copyright (c) 2019 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

      This version of this YANG module is part of RFC 8530; see
      the RFC itself for full legal notices.";

   revision 2019-01-25 {
       "Initial revision.";
       "RFC 8530: YANG Model for Logical Network Elements";

   // top level device definition statements

   container logical-network-elements {
       "Allows a network device to support multiple logical
        network element (device) instances.";
     list logical-network-element {
Top   ToC   Page 12
       key "name";
         "List of logical network elements.";
       leaf name {
         type string;
           "Device-wide unique identifier for the
            logical network element.";
       leaf managed {
         type boolean;
         default "true";
           "True if the host can access LNE information
            using the root mount point.  This value
            may not be modifiable in all implementations.";
       leaf description {
         type string;
           "Description of the logical network element.";
       container root {
           "Container for mount point.";
         yangmnt:mount-point "root" {
             "Root for models supported per logical
              network element.  This mount point may or may not
              be inline based on the server implementation.  It
              SHALL always contain a YANG library and interfaces

              When the associated 'managed' leaf is 'false', any
              operation that attempts to access information below
              the root SHALL fail with an error-tag of
              'access-denied' and an error-app-tag of

   // augment statements

   augment "/if:interfaces/if:interface" {
       "Add a node for the identification of the logical network
Top   ToC   Page 13
        element associated with an interface.  Applies to
        interfaces that can be assigned per logical network

        Note that a standard error will be returned if the
        identified leafref isn't present.  If an interface
        cannot be assigned for any other reason, the operation
        SHALL fail with an error-tag of 'operation-failed' and an
        error-app-tag of 'lne-assignment-failed'.  A meaningful
        error-info that indicates the source of the assignment
        failure SHOULD also be provided.";
     leaf bind-lne-name {
       type leafref {
         path "/logical-network-elements/logical-network-element/name";
         "Logical network element ID to which the interface is

   // notification statements

   notification bind-lne-name-failed {
       "Indicates an error in the association of an interface to an
        LNE.  Only generated after success is initially returned
        when bind-lne-name is set.";
     leaf name {
       type leafref {
         path "/if:interfaces/if:interface/if:name";
       mandatory true;
         "Contains the interface name associated with the
     leaf bind-lne-name {
       type leafref {
         path "/if:interfaces/if:interface/lne:bind-lne-name";
       mandatory true;
         "Contains the bind-lne-name associated with the
     leaf error-info {
       type string;
Top   ToC   Page 14
         "Optionally, indicates the source of the assignment


7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,

   [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,

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
Top   ToC   Page 15
   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,

   [RFC8528]  Bjorklund, M. and L. Lhotka, "YANG Schema Mount",
              RFC 8528, DOI 10.17487/RFC8528, March 2019,

7.2.  Informative References

              Lindem, A., Berger, L., Bogdanovic, D., and C. Hopps,
              "Network Device YANG Logical Organization", Work in
              Progress, draft-ietf-rtgwg-device-model-02, March 2017.

              Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem,
              "YANG Data Model for OSPF Protocol", Work in Progress,
              draft-ietf-ospf-yang-21, January 2019.

   [RFC7317]  Bierman, A. and M. Bjorklund, "A YANG Data Model for
              System Management", RFC 7317, DOI 10.17487/RFC7317, August
              2014, <>.

   [RFC7895]  Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module
              Library", RFC 7895, DOI 10.17487/RFC7895, June 2016,

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
Top   ToC   Page 16
   [RFC8348]  Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
              YANG Data Model for Hardware Management", RFC 8348,
              DOI 10.17487/RFC8348, March 2018,

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,

   [RFC8529]  Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and
              X. Liu, "YANG Data Model for Network Instances", RFC 8529,
              DOI 10.17487/RFC8529, March 2019,

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