A YANG Network Data Model for Inventory Topology Mapping
draft-ietf-ivy-network-inventory-topology-12

Network Inventory YANG                                        B. Wu, Ed.
Internet-Draft                                                    Huawei
Intended status: Standards Track                            M. Boucadair
Expires: 26 April 2027                                            Orange
                                                                 C. Zhou
                                                            China Mobile
                                                                   Q. Wu
                                                                  Huawei
                                                         23 October 2026

        A YANG Network Data Model for Inventory Topology Mapping
              draft-ietf-ivy-network-inventory-topology-12

Abstract

   This document specifies a YANG data model that extends the network
   topology data model (RFC 8345) to map network topologies with
   inventories.  The data model introduces the "inventory-topology"
   network type and augmentations for physical entity mappings and
   capabilities, which may be used by any overlay network topology for
   service provisioning validation, network maintenance, and capacity
   planning.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Network Inventory YANG
   Working Group mailing list (ivy@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/ivy/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ietf-ivy-wg/network-inventory-topology.

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 https://datatracker.ietf.org/drafts/current/.

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   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 26 April 2027.

Copyright Notice

   Copyright (c) 2026 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Editorial Note (To be removed by RFC Editor)  . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  Sample Use Cases of the Data Model  . . . . . . . . . . . . .   4
     3.1.  Determine Available Resources of Service Attachment Points
           (SAPs)  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Multi-layer Network Navigation  . . . . . . . . . . . . .   5
     3.3.  "What-if" Scenarios . . . . . . . . . . . . . . . . . . .   6
   4.  Module Tree Structure . . . . . . . . . . . . . . . . . . . .   6
     4.1.  Link Extensions . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Port-Breakout Capability  . . . . . . . . . . . . . . . .   8
     4.3.  Semantics of Inventory Mappings . . . . . . . . . . . . .   9
   5.  Network Inventory Topology YANG Module  . . . . . . . . . . .   9
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .  16
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  18
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  'link-type' Usage Examples . . . . . . . . . . . . .  22
   Appendix B.  JSON Example of a Multi-fibre Push On (MPO)
           Breakout-Channel Port . . . . . . . . . . . . . . . . . .  24
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  25
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25

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1.  Introduction

   [I-D.ietf-ivy-network-inventory-yang] defines the base network
   inventory model to aggregate the inventory data of Network Elements
   (NEs).  This data includes identification of these NEs and their
   hardware, firmware, and software components.  Examples of inventory
   hardware components could be rack, shelf, slot, board, or physical
   port.  Examples of inventory software components could be platform
   Operating System (OS), software modules, BIOS, or bootloader
   [I-D.ietf-ivy-network-inventory-software].

   In order to ease navigation between inventory and network topologies,
   this document extends the network topology data model [RFC8345] for
   network inventory mapping: "ietf-network-inventory-topology"
   (Section 5).  The YANG data model in this document conforms to the
   YANG data modeling language [RFC7950].

   Similar to the base inventory data model
   [I-D.ietf-ivy-network-inventory-yang], the network inventory topology
   data model does not make any assumption about involved NEs and their
   roles in topologies.  As such, the mapping data model can be applied
   independent of the network type (optical local loops, access network,
   core network, etc.) and application.

   Therefore, this YANG data model can be used to represent a physical
   network instance at the lowest underlay abstraction level, as shown
   in Section 4.4.9 of [RFC8345].  Alternatively, it can be used in
   conjunction with existing network topology models, such as [RFC9408],
   [RFC8944], [RFC8346], [RFC8795], and [I-D.ietf-ccamp-otn-topo-yang],
   when they contain nodes, links, or termination points belonging to
   the lowest underlay level.

1.1.  Editorial Note (To be removed by RFC Editor)

      Note to the RFC Editor: This section is to be removed prior to
      publication.

   This document contains placeholder values that need to be replaced
   with finalized values at the time of publication.  This note
   summarizes all of the substitutions that are needed.

   Please apply the following replacements:

   *  XXXX --> the assigned RFC number for this I-D

   *  AAAA --> the assigned RFC number for
      [I-D.ietf-ivy-network-inventory-yang]

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   *  2026-09-11 --> the actual date of the publication of this document

2.  Conventions and Definitions

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

   The following terms are defined in [RFC7950] and are not redefined
   here:

   *  augment

   *  data model

   *  data node

   The meanings of the symbols in the YANG tree diagrams are defined in
   [RFC8340].

   This document uses terms defined in
   [I-D.ietf-ivy-network-inventory-yang].

   The document adheres to the folding conventions in [RFC8792].

3.  Sample Use Cases of the Data Model

3.1.  Determine Available Resources of Service Attachment Points (SAPs)

   The inventory topology data model provides a physical port reference
   (port-ref) that enables correlation between logical topology entities
   and physical inventory components.  During service provisioning, the
   SAP's parent-termination-point can be associated with the inventory
   topology's port-ref to locate the underlying physical resource.

   Figure 1 illustrates the query interactions.  During service
   provisioning, the orchestrator can issue a query using the SAP data
   model (e.g., obtaining a list of SAPs across multiple PEs as shown in
   Appendix A of [RFC9408]), and then uses the inventory topology data
   model to identify the physical port underlying each candidate SAP.
   Specifically, the "parent-termination-point" of a SAP is mapped to
   the corresponding "port-ref" in the inventory topology, allowing the
   orchestrator to locate the physical resource.  The orchestrator can
   then consult other relevant topology models (e.g., [RFC8795]) to
   verify whether the identified port has adequate capacity for the
   requested service.

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   If the physical port underlying a candidate SAP has insufficient
   resources (e.g., port speed fully utilized), the orchestrator can
   select an alternate SAP that maps to a different port with adequate
   capacity.  If no alternative SAP is available, the orchestrator flags
   the request for manual intervention, providing the operator with
   precise inventory information about the bottleneck (e.g., "Port
   GE0/6/1 on NE-PE1 is at 95% utilization").  The resource constraint
   can also feed into a "what-if" analysis (see Section 3.3) to evaluate
   hardware upgrades or alternative underlay paths.

                         .-----------------.
                         |     Customer    |
                         '--------+--------'
         Customer Service request |
            (e.g., L3SM and L2SM) v
                         .--------+--------.
                         |    Service      |
                         |  Orchestration  |
                         '------+---+------'
                (1a) Query SAPs |   | (1b) Map SAP to physical port
           via SAP Data Model   v   v      via Inventory Topology
                         .------+---+------.
                         |     Network     |
                         |   Controller    |
                         '--------+--------'
                                  |
            .---------------------+---------------------.
            |                  Network                  |
            '-------------------------------------------'

          Figure 1: An Example Usage of Network Inventory Topology

3.2.  Multi-layer Network Navigation

   A multi-layer network encompasses multiple layers (e.g., Layer 2 and
   Layer 3, or Optical Transport Network (OTN) and Wavelength Division
   Multiplexing (WDM) layers).

   A multi-layer network topology comprises nodes, links, and
   termination points that can belong to different layers.

   A multi-layer network can contain multiple types of topological
   elements: physical elements (associated with an inventory element) or
   logical elements (associated with topology elements in the underlay
   layer).

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   The topology models support navigation across the different layers,
   down to the physical layer, as defined in Section 4.4.9 of [RFC8345].
   The navigation between the physical layer and the network inventory
   is outside the scope of the topology models and is addressed in this
   document.

   This document augments both "ietf-network" (for nodes and network-
   types) and "ietf-network-topology" (for links and termination
   points), following the standard extension pattern described in
   Section 4.3 of [RFC8345].  This augmentation associates inventory
   data nodes with topology data nodes to support multi-layer navigation
   across physical and logical resources.

   To make this navigation operationally explicit, this module provides
   concrete YANG data nodes in the "inventory-mapping-attributes"
   container, where the leaf "ne-ref" links topology nodes to their
   corresponding network elements, and the leaf "port-ref" links
   termination points to their physical port components, thereby
   enabling direct correlation between the [RFC8345] topology and the
   underlying inventory.

3.3.  "What-if" Scenarios

   [I-D.irtf-nmrg-network-digital-twin-arch] defines Network Digital
   Twin (NDT) as a virtual representation of the physical network.  Such
   representation is meant to be used to analyze, diagnose, emulate, and
   then manage the physical network based on data, models, and
   interfaces.

   [I-D.ietf-nmop-simap-concept] defines Service and Infrastructure Maps
   (SIMAP) as an abstraction model that provides a unified view of both
   service and infrastructure information, enabling correlation between
   service requirements and underlying resource capabilities.

   Both architectures require accurate mapping between logical network
   topology and physical inventory as a foundational data layer.  This
   model provides the essential physical resource information to such
   systems, enabling them to perform accurate "what-if" analysis (e.g.,
   impact prediction of hardware End-of-Life, path re-optimization under
   resource constraints, service availability assessment).

4.  Module Tree Structure

   An overview of the structure of the "ietf-network-inventory-topology"
   module is shown in Figure 2.

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      module: ietf-network-inventory-topology

        augment /nw:networks/nw:network/nw:network-types:
          +--rw inventory-topology!
        augment /nw:networks/nw:network/nw:node:
          +--rw inventory-mapping-attributes!
             +--rw ne-ref?   nwi:ne-ref
        augment /nw:networks/nw:network/nt:link:
          +--rw inventory-mapping-attributes!
             +--rw link-type?   identityref
        augment /nw:networks/nw:network/nw:node/nt:termination-point:
          +--rw inventory-mapping-attributes!
          |  +--rw ne-ref?     nwi:ne-ref
          |  +--rw port-ref?   leafref
          +--ro port-breakout!
             +--ro breakout-channel* [channel-id]
                +--ro channel-id    uint16

    Figure 2: The Structure of the Network Inventory Mapping Data Model

   The module augments the "ietf-network" and "ietf-network-topology"
   module as follows:

   Network types:  The "inventory-topology" container augments the
      "network-types" container.

   Inventory mapping attributes for nodes, links, and termination
   points:  The corresponding containers augment the topology modules
      with the references to the base network inventory.

   Port breakout capability:  The "port-breakout" container augments
      termination points to report the channel breakout capability of
      the underlying physical port.

4.1.  Link Extensions

   This document adds a lightweight "link-type" leaf to the topology
   link mapping to enable basic physical media classification.

   "link-type":  An identityref indicating the link media type.

      Examples of wired link types are "copper", "fiber", or "coax".
      For wireless media, values such as "microwave", or "wlan" may be
      used.  See also [RFC9656] for more detailed microwave radio
      attributes.

      The "link-type" serves as a lightweight discriminator that guides

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      to the appropriate specialized inventory model for detailed
      resource information.

      For example, wired media ("fiber" or "copper") typically
      references a passive network inventory model such as the one
      defined in [I-D.ietf-ivy-passive-network-inventory].

4.2.  Port-Breakout Capability

   High-density Ethernet ports (e.g., 400 Gb/s DR4) can be split into
   multiple independent lower-speed channels.  The breakout channels
   represent the intrinsic capability of the port to be partitioned,
   regardless of whether the port is currently configured as a trunk or
   as a breakout port.

   A trunk port is associated with exactly one physical interface.  A
   breakout port is a port that is decomposed into two or more physical
   interfaces; those interfaces may run at the same or different speeds
   and may consume the same or a different number of breakout channels.

   The container "port-breakout" is added under the termination-point
   augmentation.  It lists the logical channels into which the single
   physical port can be divided.  Only termination-points whose parent
   port is breakout-capable need to instantiate the container; otherwise
   the container is omitted, keeping the topology model minimal for the
   common non-breakout case.

   Breakout channel is an atomic resource element obtained by
   partitioning a breakout port.  One physical interface may be
   associated with one or more breakout channels; a breakout channel is
   associated with at most one physical interface.  Appendix B provides
   a JSON instance [RFC7951] example for a port with breakout
   capabilities.

   It is assumed that a port which supports breakout can be configured
   either as a trunk port or as a breakout port.  The "port-breakout"
   container serves as a capability advertisement for the termination-
   point of the parent physical port.  It does not provide direct
   references or pointers to the resulting lower-speed termination-
   points or interfaces.  The correlation between a specific "channel-
   id" and its corresponding lower-speed termination-point is outside
   the scope of this document and is expected to be provided by a future
   companion module.  Interface channelisation (e.g., VLAN sub-
   interfaces) is also outside the scope of this document and is
   addressed by the Layer 2 network topology model [RFC8944].

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4.3.  Semantics of Inventory Mappings

   The "inventory-topology" network type establishes a physical
   topology.  Nodes, TPs, and links within this topology represent
   physical entities, regardless of whether an inventory mapping is
   declared.

   The "inventory-mapping-attributes" container expresses whether an
   inventory mapping is declared for a physical object.

   When the container is present, the mapping is complete if it contains
   all attributes needed to identify the mapped object: "ne-ref" for
   nodes, "link-type" for links, and both "ne-ref" and "port-ref" for
   TPs.  A TP with only 'ne-ref' has a partial mapping: the NE is known
   but the port is unresolved (e.g., CPE with limited discovery
   capability).  A partial mapping is a valid state, not an error.
   Consumers MUST NOT use a partial mapping for port-level resource
   validation, but MAY use it for NE-level correlation.

   The "port-breakout" container is independent of inventory mapping.
   It reports a physical capability of the port and may be present
   without an inventory mapping.

5.  Network Inventory Topology YANG Module

   This module augments the Network Topology module defined in
   [RFC8345].

   This module imports the base network inventory
   [I-D.ietf-ivy-network-inventory-yang].

   <CODE BEGINS> file "ietf-network-inventory-topology@2026-10-19.yang"
   module ietf-network-inventory-topology {
     yang-version 1.1;
     namespace
       "urn:ietf:params:xml:ns:yang:ietf-network-inventory-topology";
     prefix nwit;

     import ietf-network {
       prefix nw;
       reference
         "RFC 8345: A YANG Data Model for Network Topologies,
                    Section 4.1";
     }
     import ietf-network-topology {
       prefix nt;
       reference
         "RFC 8345: A YANG Data Model for Network Topologies,

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                    Section 4.2";
     }
     import ietf-network-inventory {
       prefix nwi;
       reference
         "RFC AAAA: A Base YANG Data Model for Network Inventory";
     }

     organization
       "IETF Network Inventory YANG (ivy) Working Group";
     contact
       "WG Web:   https://datatracker.ietf.org/wg/ivy
        WG List:  IVY <mailto:ivy@ietf.org>

        Editor: Bo Wu
                <lana.wubo@huawei.com>
        Editor: Mohamed Boucadair
                <mohamed.boucadair@orange.com>
        Author: Cheng Zhou
                <zhouchengyjy@chinamobile.com>
        Author: Qin Wu
                <bill.wu@huawei.com>";
     description
       "This module defines a YANG module for network
        topology and inventory mapping.

        Copyright (c) 2026 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 Revised
        BSD License set forth in Section 4.c of the IETF Trust's
        Legal Provisions Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

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

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.";

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     revision 2026-10-19 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Network Data Model for Inventory Topology
                    Mapping";
     }

     identity link-type {
       description
         "Base identity for classifying the physical media type of a
          link at the inventory topology layer. Additional identities
          may be defined to cover other media types.";
     }

     identity copper {
       base link-type;
       description
         "Copper-based physical link.";
     }

     identity fiber {
       base link-type;
       description
         "Fiber-based physical link.";
     }

     identity coax {
       base link-type;
       description
         "Coaxial cable-based physical link.";
     }

     identity microwave {
       base link-type;
       description
         "Microwave-based wireless link.

          Detailed microwave radio attributes are defined in the
          microwave topology data model.";
       reference
         "RFC 9656: A YANG Data Model for Microwave Topology";
     }

     identity wlan {
       base link-type;
       description
         "IEEE 802.11 wireless link.";

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     }

     identity unknown {
       base link-type;
       description
         "The link media type is unknown or could not be determined.

          This identity is used as a fallback when the physical medium
          cannot be classified into any of the other defined types.

          When a discovery system is unable to determine the media
          type, it SHOULD use this identity rather than leaving the
          leaf unset. An unset leaf indicates that the link type has
          not been assessed, whereas unknown explicitly records that
          the medium could not be classified.";
     }

     identity leased-fiber {
       base fiber;
       description
         "Leased fiber link.  The physical medium is fiber, but the link
          is provided by a third-party operator.  Detailed physical
          attributes are typically not visible to the lessee.";
     }

     augment "/nw:networks/nw:network/nw:network-types" {
       description
         "Introduces a new network type for inventory topology
          mapping.";
       container inventory-topology {
         presence
           "Indicates a physical network topology, containing
            physical-layer attributes including inventory mapping, port
            breakout capabilities, and link media types.";
         description
           "Container for the inventory-topology network type.

            When present, it signals that the network contains
            physical-layer augmentations as defined in this module.
            This network type is typically discovered by the network
            controller to identify a physical underlay network; it may
            be configured manually when discovery is not available.

            This network type is intended to serve as the underlay
            for logical network topologies (Layer 2, Layer 3,
            Traffic Engineering (TE), etc.).";
       }
     }

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     augment "/nw:networks/nw:network/nw:node" {
       when '../nw:network-types/nwit:inventory-topology';
       description
         "Augments the network topology node with inventory mapping
          attributes. This enables correlation between the physical node
          and its corresponding network element in the inventory.";
       container inventory-mapping-attributes {
         must 'ne-ref' {
           error-message
             "A physical node must include ne-ref to identify the
              corresponding network element.";
         }
         presence
           "If present, an inventory mapping is declared for this node.
            If absent, no inventory mapping is declared.";
         description
           "Container for inventory mapping attributes of a node.

            In typical deployments, the ne-ref leaf SHOULD be populated
            through automatic discovery.  It SHOULD NOT be configured
            manually except where discovery is not possible (e.g.,
            Customer Premises Equipment (CPE) outside the operator's
            management domain).";
         leaf ne-ref {
           type nwi:ne-ref;
           description
             "Reference to the NE in the inventory that corresponds to
              this topology node.

              When the container inventory-mapping-attributes
              is present, this reference identifies the NE that the
              topology node maps to.";
         }
       }
     }

     augment "/nw:networks/nw:network/nt:link" {
       when '../nw:network-types/nwit:inventory-topology';
       description
         "Augments the physical network topology link with
          inventory-related attributes.";
       container inventory-mapping-attributes {
         must 'link-type' {
           error-message
             "A physical link must include link-type to classify the
              link media type.";
         }
         presence

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           "If present, an inventory mapping is declared for this link.
            If absent, no inventory mapping is declared.";
         description
           "Container for inventory-related attributes of a link.

            This container provides lightweight media classification.
            The link-type indicates which specialized inventory model
            contains detailed resource information:

            - Wired media (fiber, copper): passive network inventory
            - Wireless media (microwave, wlan): wireless-specific
              inventory

              Detailed inventory references may be added in future
              modules.

              In typical deployments, the link-type leaf SHOULD be
              populated through automatic discovery.  It SHOULD NOT be
              configured manually except where discovery is not possible
              (e.g., leased lines).";
         leaf link-type {
           type identityref {
             base link-type;
           }
           description
             "Classification of the link media type at the topology
              layer.

              The base identity 'link-type' is extensible. Examples
              of derived identities include 'copper', 'fiber',
              'coax', 'microwave', and 'wlan'.

              This leaf serves as a lightweight discriminator.  When
              the value is 'microwave', detailed microwave link
              attributes are defined in the microwave topology data
              model. Wired media (e.g., fiber, copper, or coax) may
              be detailed in a passive network inventory data
              model.";
         }
       }
     }

     augment "/nw:networks/nw:network/nw:node/nt:termination-point" {
       when '../../nw:network-types/nwit:inventory-topology';
       description
         "Augments the termination point (TP) with inventory mapping
          and port breakout.";
       container inventory-mapping-attributes {

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         must "nwit:ne-ref =
               ../../nwit:inventory-mapping-attributes/nwit:ne-ref" {
           error-message
             "A physical TP must have a ne-ref that matches the
              ne-ref of its parent node, so that port-ref is
              resolved within a single unambiguous network element
              scope.";
         }
         presence
           "If present, an inventory mapping is declared for this TP.
            If absent, no inventory mapping is declared.";
         description
           "Container for inventory mapping attributes of a TP.

            In typical deployments, the port-ref leaves SHOULD be
            populated through automatic discovery.  They SHOULD NOT
            be configured manually except where discovery is not
            possible (e.g., CPE outside the operator's management
            domain, leased lines).";
         uses nwi:port-ref {
           refine "port-ref" {
             description
               "Reference to the physical port component in the
                network inventory.

                When the container inventory-mapping-attributes
                is present, this reference identifies the port
                component that the TP maps to. The ne-ref leaf must
                also be present, as component identifiers are scoped
                to a network element.";
           }
         }
       }
       container port-breakout {
         presence
           "Indicates the physical port supports channel breakout.";
         config false;
         description
           "Breakout capability of the physical port represented by
            this TP. One TP maps to one physical port; channels are
            listed here. This container is present only when the
            underlying hardware supports partitioning the port into
            multiple independent channels (e.g., 400G to 4x100G).

            This container is read-only (config false) as it reflects
            hardware-determined state.";
         list breakout-channel {
           key "channel-id";

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           description
             "Indicates the list of breakout channels available
              on this port. Each entry represents an independent lane
              or sub-port that can be used for channelized
              interfaces.";
           leaf channel-id {
             type uint16;
             description
               "Records a unique identifier for the breakout channel
                within the scope of the parent port.";
           }
         }
       }
     }
   }
   <CODE ENDS>

6.  Operational Considerations

   The "ietf-network-inventory-topology" YANG module enables a network
   controller to report discovered network topology and inventory
   information.  Automatic discovery serves as the primary mechanism,
   with selective configuration capabilities provided for scenarios
   where discovery is not feasible.

   For typical operations such as service provisioning and network
   planning, the model offers read-only query access to authoritative
   mappings between topology view of physical objects and their
   inventory entities.  The inventory-mapping-attributes containers are
   defined as read-write (config true) to accommodate cases where
   automatic discovery is not possible, including:

   *  Customer Premises Equipment (CPE) outside the operator's
      management domain

   *  Leased lines and third-party transport resources

   *  Planned or hypothetical resources for future deployment

   In these cases, the operator manually configures the mapping to
   maintain accurate topology-to-inventory correlation.

   The following nodes are read-only (config false) as they represent
   hardware-determined state:

   port-breakout:  Hardware capability determined by physical port
      characteristics

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7.  Security Considerations

   This section is modeled after the template described in Section 3.7.1
   of [RFC9907].

   The "ietf-network-inventory-topology" YANG module defines a data
   model that is designed to be accessed via YANG-based management
   protocols, such as Network Configuration (NETCONF) [RFC6241] and
   RESTCONF [RFC8040].  These YANG-based management protocols (1) have
   to use a secure transport layer (e.g., Secure Shell (SSH) [RFC4252],
   TLS [RFC9846], and QUIC [RFC9000]) and (2) have to use mutual
   authentication.

   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.

   There are a number of data nodes defined in this YANG module that are
   writable/creatable/deletable (i.e., "config true", which is the
   default).  All writable data nodes are likely to be sensitive or
   vulnerable in some network environments.  Write operations (e.g.,
   edit-config) and delete operations to these data nodes without proper
   protection or authentication can have a negative effect on network
   operations.  The following subtrees and data nodes have particular
   sensitivities/vulnerabilities:

      'ne-ref', 'port-ref', and 'link-type':  These nodes are sensitive
         as they establish the mapping between logical topology and
         physical inventory.  Incorrect inventory mapping (e.g., stale
         or manually misconfigured 'ne-ref' or 'port-ref' values) may
         lead to mis-provisioning of services or misinterpretation of
         physical resource availability, which can result in failed
         service activation, unexpected traffic paths, or inaccurate
         capacity planning.

   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.  Specifically, the following
   subtrees and data nodes have particular sensitivities/
   vulnerabilities:

      'ne-ref', 'port-ref', and 'link-type':  These nodes are sensitive

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         as they reveal network infrastructure details. 'ne-ref' may be
         used to track the set of network elements; 'port-ref' discloses
         internal port and component naming; 'link-type' can reveal
         infrastructure ownership (e.g., the 'leased-fiber' identity
         distinguishes third-party transport from owned infrastructure).

      'port-breakout':  This node exposes hardware capabilities.

   There are no sensitive RPC or action operations defined in this
   module.

   As this module augments the network topology model defined in
   [RFC8345], the module also inherits the security considerations
   discussed in Section 8 of [RFC8345] for the underlying network
   topology data model.

8.  IANA Considerations

   IANA is requested to register the following URI in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

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

   IANA is requested to register the following YANG module in the "YANG
   Module Names" registry [RFC6020] within the "YANG Parameters"
   registry group:

      Name:  ietf-network-inventory-topology
      Maintained by IANA?  N
      Namespace:
        urn:ietf:params:xml:ns:yang:ietf-network-inventory-topology
      Prefix:  nwit
      Reference:  RFC XXXX

9.  References

9.1.  Normative References

   [I-D.ietf-ivy-network-inventory-yang]
              Yu, C., Belotti, S., Bouquier, J., Peruzzini, F., and P.
              Bedard, "A Base YANG Data Model for Network Inventory",
              Work in Progress, Internet-Draft, draft-ietf-ivy-network-
              inventory-yang-20, 29 September 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ivy-
              network-inventory-yang-20>.

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   [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/rfc/rfc2119>.

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

   [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/rfc/rfc6020>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/rfc/rfc7950>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8341>.

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/rfc/rfc8345>.

9.2.  Informative References

   [I-D.ietf-ccamp-otn-topo-yang]
              Zheng, H., Busi, I., Liu, X., Belotti, S., and O. G. de
              Dios, "A YANG Data Model for Optical Transport Network
              Topology", Work in Progress, Internet-Draft, draft-ietf-
              ccamp-otn-topo-yang-21, 16 June 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ccamp-
              otn-topo-yang-21>.

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   [I-D.ietf-ivy-network-inventory-software]
              Wu, B., Zhou, C., Wu, Q., and M. Boucadair, "A YANG
              Network Data Model of Network Inventory Software
              Extensions", Work in Progress, Internet-Draft, draft-ietf-
              ivy-network-inventory-software-04, 6 July 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ivy-
              network-inventory-software-04>.

   [I-D.ietf-ivy-passive-network-inventory]
              Guo, A., van caenegem, T., Davis, N., Tilocca, M., and B.
              Peters, "A YANG Data Model for Passive Network Inventory",
              Work in Progress, Internet-Draft, draft-ietf-ivy-passive-
              network-inventory-01, 10 September 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ivy-
              passive-network-inventory-01>.

   [I-D.ietf-nmop-simap-concept]
              Havel, O., Claise, B., de Dios, O. G., and T. Graf,
              "SIMAP: Concept, Requirements, and Use Cases", Work in
              Progress, Internet-Draft, draft-ietf-nmop-simap-concept-
              14, 2 October 2026,
              <https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
              simap-concept-14>.

   [I-D.irtf-nmrg-network-digital-twin-arch]
              Zhou, C., Yang, H., Duan, X., Lopez, D., Pastor, A., Wu,
              Q., Boucadair, M., and C. Jacquenet, "Network Digital Twin
              (NDT): Concepts and Reference Architecture", Work in
              Progress, Internet-Draft, draft-irtf-nmrg-network-digital-
              twin-arch-13, 1 July 2026,
              <https://datatracker.ietf.org/doc/html/draft-irtf-nmrg-
              network-digital-twin-arch-13>.

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/rfc/rfc4252>.

   [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/rfc/rfc6241>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/rfc/rfc7951>.

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   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8040>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8340>.

   [RFC8346]  Clemm, A., Medved, J., Varga, R., Liu, X.,
              Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
              for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346,
              March 2018, <https://www.rfc-editor.org/rfc/rfc8346>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/rfc/rfc8792>.

   [RFC8795]  Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Gonzalez de Dios, "YANG Data Model for Traffic
              Engineering (TE) Topologies", RFC 8795,
              DOI 10.17487/RFC8795, August 2020,
              <https://www.rfc-editor.org/rfc/rfc8795>.

   [RFC8944]  Dong, J., Wei, X., Wu, Q., Boucadair, M., and A. Liu, "A
              YANG Data Model for Layer 2 Network Topologies", RFC 8944,
              DOI 10.17487/RFC8944, November 2020,
              <https://www.rfc-editor.org/rfc/rfc8944>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9000>.

   [RFC9408]  Boucadair, M., Ed., Gonzalez de Dios, O., Barguil, S., Wu,
              Q., and V. Lopez, "A YANG Network Data Model for Service
              Attachment Points (SAPs)", RFC 9408, DOI 10.17487/RFC9408,
              June 2023, <https://www.rfc-editor.org/rfc/rfc9408>.

   [RFC9656]  Mansfield, S., Ed., Ahlberg, J., Ye, M., Li, X., and D.
              Spreafico, "A YANG Data Model for Microwave Topology",
              RFC 9656, DOI 10.17487/RFC9656, September 2024,
              <https://www.rfc-editor.org/rfc/rfc9656>.

   [RFC9846]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 9846, DOI 10.17487/RFC9846, July 2026,
              <https://www.rfc-editor.org/rfc/rfc9846>.

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   [RFC9907]  Bierman, A., Boucadair, M., Ed., and Q. Wu, "Guidelines
              for Authors and Reviewers of Documents Containing YANG
              Data Models", BCP 216, RFC 9907, DOI 10.17487/RFC9907,
              March 2026, <https://www.rfc-editor.org/rfc/rfc9907>.

Appendix A.  'link-type' Usage Examples

   This appendix provides examples illustrating the usage of the "link-
   type" data node.

   Scenario: Device "SW-1" and device "SW-2" are directly connected by a
   fiber.

   Physical topology:

   .--------.                                    .--------.
   |        |                                    |        |
   |  SW-1  +========= fiber link ===============+  SW-2  |
   |        |                                    |        |
   '--------'                                    '--------'

   Key parts of the JSON example are as follows:

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-id": "example:campus-topology",
           "network-types": {
             "ietf-network-inventory-topology:inventory-topology": {}
           },
           "node": [
             {
               "node-id": "example:SW-1",
               "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                 "ne-ref": "example:NE-SW1"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:TP-SW1-P1",
                   "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                     "ne-ref": "example:NE-SW1",
                     "port-ref": "example:eth-port-1"
                   }

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                 }
               ]
             },
             {
               "node-id": "example:SW-2",
               "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                 "ne-ref": "example:NE-SW2"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:TP-SW2-P2",
                   "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                     "ne-ref": "example:NE-SW2",
                     "port-ref": "example:eth-port-2"
                   }
                 }
               ]
             }
           ],
           "ietf-network-topology:link": [
             {
               "link-id": "example:Link-SW1-SW2",
               "source": {
                 "source-node": "example:SW-1",
                 "source-tp": "example:TP-SW1-P1"
               },
               "destination": {
                 "dest-node": "example:SW-2",
                 "dest-tp": "example:TP-SW2-P2"
               },
               "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                 "link-type": "ietf-network-inventory-topology:fiber"
               }
             }
           ]
         }
       ]
     }
   }

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Appendix B.  JSON Example of a Multi-fibre Push On (MPO) Breakout-
             Channel Port

   This appendix provides an example of a 400 Gb/s DR4 port that is
   physically implemented as four independent 100 Gb/s lanes (an MPO
   breakout).  The lanes are exposed as breakout-channel entries so that
   the port can later be configured as either a single 400G trunk or
   four 100G breakout interfaces.  The instance data below shows the
   minimal JSON encoding [RFC7951] of the "port-breakout" container for
   this port.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-id": "example:underlay-topology-400g",
           "network-types": {
             "ietf-network-inventory-topology:inventory-topology": {}
           },
           "node": [
             {
               "node-id": "example:n1",
               "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                 "ne-ref": "example:NE-1"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:400g-1/0/1",
                   "ietf-network-inventory-topology:inventory-mapping-\
                                                          attributes": {
                     "ne-ref": "example:NE-1",
                     "port-ref": "example:port-1"
                   },
                   "ietf-network-inventory-topology:port-breakout": {
                     "breakout-channel": [
                       {
                         "channel-id": 1
                       },
                       {
                         "channel-id": 2
                       },
                       {
                         "channel-id": 3
                       },
                       {

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                         "channel-id": 4
                       }
                     ]
                   }
                 }
               ]
             }
           ]
         }
       ]
     }
   }

Acknowledgments

   The authors wish to thank Italo Busi, Olga Havel, Aihua Guo, Oscar
   Gonzalez de Dios, and many others for their helpful comments and
   suggestions.

   Thanks to Olga Havel for the detailed shepherd review.

Contributors

   Chaode Yu
   Huawei
   Email: yuchaode@huawei.com

Authors' Addresses

   Bo Wu (editor)
   Huawei
   Email: lana.wubo@huawei.com

   Mohamed Boucadair
   Orange
   Email: mohamed.boucadair@orange.com

   Cheng Zhou
   China Mobile
   Email: zhouchengyjy@chinamobile.com

   Qin Wu
   Huawei
   Email: bill.wu@huawei.com

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