Network Management Operations O. Havel Internet-Draft Huawei Intended status: Informational N. Davis Expires: 3 May 2027 Ciena O. G. D. Dios Telefonica T. Graf Swisscom 30 October 2026 A YANG Data Model for SIMAP Additional Features draft-havel-nmop-simap-features-yang-01 Abstract This document defines a YANG data model for Service & Infrastructure Maps (SIMAP) Additional Features, including optional graph navigation, lifecycle and external-link capabilities intended to be reusable with RFC 8345 topology models, including implementations using RFC 8795. 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/. 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 3 May 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 Havel, et al. Expires 3 May 2027 [Page 1] Internet-Draft SIMAP Additional Features YANG Model October 2026 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Requirements not supported by RFC8345 (Gaps) . . . . . . 3 2.1.1. Features for RFC8345 Gaps . . . . . . . . . . . . . . 4 3. API Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Solution Proposal for the RFC8345 Gaps . . . . . . . . . . . 6 4.1. SIMAP Features . . . . . . . . . . . . . . . . . . . . . 6 4.2. Feature simap-extensibility . . . . . . . . . . . . . . . 7 4.2.1. REQ-EXTENSIBLE: Extensible via metadata . . . . . . . 7 4.3. Feature simap-navigation . . . . . . . . . . . . . . . . 8 4.3.1. REQ-GRAPH-TRAVERSAL: Graph Traversal . . . . . . . . 8 4.4. Feature simap-lifecycle . . . . . . . . . . . . . . . . . 10 4.4.1. REQ-PROG-OPEN-MODEL: Open and Programmable . . . . . 11 4.4.2. REQ-SNAPSHOT: Different snapshots . . . . . . . . . . 11 4.4.3. REQ-POTENTIAL: Potential new network topology . . . . 14 4.4.4. REQ-INTENDED: Intended topology . . . . . . . . . . . 16 4.4.5. REQ-STATUS: Links and nodes down in topology . . . . 18 4.4.6. REQ-TEMPO-HISTORY: Geo-spatial, temporal, historical . . . . . . . . . . . . . . . . . . . . . 19 4.5. Feature simap-external . . . . . . . . . . . . . . . . . 20 4.5.1. REQ-STD-API-BASED: Standard based . . . . . . . . . . 20 4.5.2. REQ-PLUGG: Pluggable . . . . . . . . . . . . . . . . 20 5. Model Structure Details . . . . . . . . . . . . . . . . . . . 20 6. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 21 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 9. Normative References . . . . . . . . . . . . . . . . . . . . 26 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 1. Introduction [I-D.ietf-nmop-simap-concept] defines Service & Infrastructure Maps (SIMAP) as a data model that provides a view of the operator's networks and services, including how it is connected to other models (e.g., inventory), and data (e.g., observability data, operational knowledge). It specifically provides an approach to model multi- layered topology and an appropriate mechanism to navigate amongst layers and correlate between them. This includes layers from physical topology to service topology. This model is applicable to multiple domains (access, core, data center, etc.) and technologies Havel, et al. Expires 3 May 2027 [Page 2] Internet-Draft SIMAP Additional Features YANG Model October 2026 (Optical, IP, etc.). [I-D.ietf-nmop-simap-concept] defines the requirements for SIMAP, based on the Operator use cases. We split the requirements into the following features: * Core SIMAP topology * SIMAP graph navigation * SIMAP lifecycle * SIMAP external links * SIMAP extensibility / metadata * API / server / operational This document will address the SIMAP graph navigation, SIMAP lifecycle, SIMAP external links and SIMAP extensibility / metadata requirements. These requirements will be modelled in this document in the YANG module ietf-simap-features. The Core SIMAP Topology requirements will be addressed in the separate draft. 2. Terminology Terminology for SIMAP, SIMAP modelling, SIMAP data, topology, topology layer, multi-layered topology is defined in [RFC8345] 2.1. Requirements not supported by RFC8345 (Gaps) The core SIMAP topology requirements have been addressed in another document. The following are other additional features SIMAP requirements are not fully supported by the RFC8345 and require extensions or modifications: * Operator Requirements: - REQ-PROG-OPEN-MODEL: Open and programmable SIMAP.Gap: what-if and snapshots part. Analysis and solution presented in Section 4.4.1. - REQ-STD-API-BASED: Standard based SIMAP models and APIs, for multi-vendor support. Gap: link to external models. Analysis and solution presented in Section 4.5.1. Havel, et al. Expires 3 May 2027 [Page 3] Internet-Draft SIMAP Additional Features YANG Model October 2026 - REQ-GRAPH-TRAVERSAL: Graph Traversal. Gap: links are entities, adding linkedTo relations would help. Analysis and solution presented in Section 4.3.1. - REQ-SNAPSHOT: Network snapshot topology. Analysis and solution presented in Section 4.4.2. - REQ-POTENTIAL: Potential new network topology. Analysis and solution presented in Section 4.4.3. - REQ-INTENDED: Intended topology. Analysis and solution presented in Section 4.4.4. - REQ-EXTENSIBLE: Extensible via metadata. Analysis and solution presented in Section 4.2.1. - REQ-PLUGG: SIMAP must be pluggable. Analysis and solution presented in Section 4.5.2. - REQ-STATUS: Links and nodes that are down must appear in the topology. Gap: optionally if status is in SIMAP, we need to model it. Analysis and solution presented in Section 4.4.5. * Design Requirements: - REQ-TEMPO-HISTORY: Must support geo-spatial, temporal, and historical data. Analysis and solution presented in Section 4.4.6. 2.1.1. Features for RFC8345 Gaps Based on the initial analysis, we identified that the requirements can be grouped into the following features * SIMAP Navigation. These are the requirements for navigation of SIMAP * REQ-GRAPH-TRAVERSAL * SIMAP Lifecycle. These are the requirements for modelling the lifecycle of the topology, including intended topology, potential topology, historical snapshots and relations between them. * REQ- PROG-OPEN-MODEL * REQ-SNAPSHOT * REQ-POTENTIAL * REQ-INTENDED * REQ-STATUS * REQ-TEMPO-HISTO * SIMAP External Link. These are the requirements for linking the external models and data * REQ-STD-API-BASED * REQ-PLUGG Havel, et al. Expires 3 May 2027 [Page 4] Internet-Draft SIMAP Additional Features YANG Model October 2026 * SIMAP Extensibility / metadata. These are the requirements for extending and adding the meta data - REQ-EXTENSIBLE Please note that the SIMAP core feature may be further split during the further analysis and reviews of the SIMAP module. Analysis and solution presented in Section 4.1. 3. API Scope It has been identified from the use cases that there is need for the following: * read access to the live topology (REQ-LIVE) * read access to historical topology (REQ-SNAPSHOT) * read and write access for potential topology (REQ-POTENTIAL) * read and write access for intended topology (REQ-INTENDED) Traditionally, separate API endpoints are used for accessing the live network and potential network views. If we follow this approach, the following consequences apply: * The same topology model can be reused across live, potential, and intended network representations. * Distinct API endpoints are maintained for each of the three categories. * Access control (e.g., read-only for live and read/write for potential networks) can be managed externally via NACM access control rules as defined in [RFC8341], eliminating the need to use config true/false within the model itself. * The responsibility for tracking relationships between live, potential, intended networks, and historical snapshots is delegated to applications. These applications must orchestrate across multiple APIs to compute differences between snapshots. To support more advanced solutions and enable SIMAP to be positioned across various interfaces, as discussed in (Chapter 5 of [I-D.ietf-nmop-simap-concept], the current draft proposes the following enhancements: Havel, et al. Expires 3 May 2027 [Page 5] Internet-Draft SIMAP Additional Features YANG Model October 2026 * Define a default behavior that allows separation between live, potential, and intended topologies without embedding this semantic distinction in the model itself. Instead, semantics are determined by the selected API endpoint, and the model remains agnostic to the category of topology. * Optionally enable a unified API that introduces model-level semantics to distinguish between live, potential, and intended topologies. This unified model also captures relationships among live, potential, historical, and intended instances. Such an approach supports advanced use cases that require the model to explicitly represent these semantics. 4. Solution Proposal for the RFC8345 Gaps 4.1. SIMAP Features We are introducing a set of SIMAP features that will be used to group requirements and optionally include them in the SIMAP module if the feature is implemented. Definitions will be tagged with the feature name and are only valid on a SIMAP server that supports that feature. The following is the initial set of SIMAP features: Havel, et al. Expires 3 May 2027 [Page 6] Internet-Draft SIMAP Additional Features YANG Model October 2026 module ietf-simap-features { /* … other statements … */ feature simap-navigation { description "This feature indicates that the SIMAP server supports those SIMAP requirements not supported by RFC8345, but related to connecting SIMAP navigation"; } feature simap-lifecycle { description "This feature indicates that the SIMAP server supports those SIMAP requirements not supported by RFC8345, but related to the overall SIMAP lifecycle, including intent, potential (for what-if) and historical snapshots"; } feature simap-external { description "This feature indicates that the SIMAP server supports those SIMAP requirements not supported by RFC8345, but related to connecting SIMAP to external models and data"; } feature simap-extensibility { description "This feature indicates that the SIMAP server supports those SIMAP requirements not supported by RFC8345, but related to extensing the model and adding meta data"; } /* … other statements … */ } Figure 1: The SIMAP Features 4.2. Feature simap-extensibility The solution is proposed for the following requirements: * REQ- EXTENSIBLE The changes to the RFC8345 model for these requirements would be specified inside: if-feature simap-extensibility. 4.2.1. REQ-EXTENSIBLE: Extensible via metadata Havel, et al. Expires 3 May 2027 [Page 7] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.2.1.1. Analysis SIMAP must be extensible with metadata. This metadata can be added via augmentation, but the model could also allow the approach of adding the metadata via the core topology model. This approach can be used for adding any semantics not explicitely implemented in the model. 4.2.1.2. Implementation Proposal Add the following to network, node, termination-point and link, and to supporting relations: grouping simap-common { description "A reusable set of optional extensions for network, node, termination point and link"; anydata extension { if-feature simap-extensibility; config false; description "The extension point for any other meta info or data or any unknown extensions. Proposed solution for SIMAP requirement REQ-EXTENSIBLE. Any additional info that is topologically significant can also be added this way for requirement REQ-SEMANTIC or REQ-PROPERTIES."; } } Figure 2: The proposal for extensions for meta data 4.3. Feature simap-navigation The solution is proposed for the following requirements: * REQ-GRAPH- TRAVERSAL The changes to the RFC8345 model for these requirements would be specified inside: if-feature simap-navigation. 4.3.1. REQ-GRAPH-TRAVERSAL: Graph Traversal 4.3.1.1. Analysis RFC8345 states that one of the reasons for modelling only unidirectional and point to point links is to allows the model to be very easily subjected to applications that make use of graph algorithms. Havel, et al. Expires 3 May 2027 [Page 8] Internet-Draft SIMAP Additional Features YANG Model October 2026 If we add support for bidirectional and multipoint links, this will make the graph traversal more difficult according to RFC8345. But based on the discussions with some Operators, having links as nodes and not direct relations is not graph traversal friendly for paths in any case and having the capability to have the direct link relations between the termination points or nodes is needed. The declarative graph queries will require the graph query language like Cypher or SPARQL. The current IETF modelling and protocols can only provide the limited graph navigation. 4.3.1.2. Implementation Proposal Add read only linked-termination-point and linked-node for optimizing path graph traversal at single layer, keep them optional for backward compatibility. Havel, et al. Expires 3 May 2027 [Page 9] Internet-Draft SIMAP Additional Features YANG Model October 2026 augment "/nw:networks/nw:network/nw:node/nt:termination-point" { description "Adding optional read only link relations between connected termination points for optimized graph traversal for paths"; list linked-termination-point { if-feature simap-navigation; config false; key "network-ref node-ref tp-ref"; description "This list identifies any linked termination points, added optionally for read only for optimized path graph traversal"; uses nt:tp-ref; } augment "/nw:networks/nw:network/nw:node" { description "Adding optional read only link relations between connected nodes for optimized graph traversal for paths"; list linked-node { if-feature simap-navigation; config false; key "network-ref node-ref"; description "This list identifies any linked nodes, added optionally for read only for optimized path graph traversal"; uses nw:node-ref; } Figure 3: The proposal for optimized path graph traversal 4.4. Feature simap-lifecycle The solution is proposed for the following requirements: * REQ-PROG- OPEN-MODEL * REQ-SNAPSHOT * REQ-POTENTIAL * REQ-INTENDED * REQ-STATUS * REQ-TEMPO-HISTO The changes to the RFC8345 model for these requirements would be specified inside: if-feature simap-lifecycle Havel, et al. Expires 3 May 2027 [Page 10] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.4.1. REQ-PROG-OPEN-MODEL: Open and Programmable 4.4.1.1. Analysis RFC8345 already supports the open and programmable API, but this requirements also mentions the what-if scenarios and different snapshots that may have some modelling implications (e.g. the need to switch between different snapshots, relation to the real network that the snapshot is for). 4.4.1.2. Implementation Proposal The implementation for the model changes for this requirement will be covered by the implementation proposals for: * REQ-POTENTIAL in Section 4.4.3 for write access to the potential new topology. * REQ-INTENDED in Section 4.4.4 for write access for intended topologies. 4.4.2. REQ-SNAPSHOT: Different snapshots 4.4.2.1. Analysis SIMAP must enable retrieval of multi-layered topology of different historical snapshots, where a snapshot is the view of the network at any given point in time. This requires the implementation proposal to take into account the following: * how to retrieve historical snapshot for the network using time stamp (recorder time and/or validity time) * how to retrieve historical snapshots for the current topology * how to model and retrieve historical topology: either full topology or only changes from another snapshot * how to retrieve the external models via links in the historical context * is this SIMAP requirement or generic requirement for any YANG retrieval via NETCONF/RESTCONF. The [RFC8342] defines different datastores: configuration datastores (startup, candidate, running, intended) and operational datastore. It does not support the historical datastores. Havel, et al. Expires 3 May 2027 [Page 11] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.4.2.2. Implementation Proposal The following are the identified implementation candidates: * Candidate 1 - Generic Solution: - this is generic requirement, not just for SIMAP, therefore implementation should not be implemented by SIMAP but by the NETCONF/RESTCONF (in NMDA?) for historical system state + conf. For conf changes via API there is history of transactions, but nothing we are aware of for historical of any data model. * Candidate 2- SIMAP Specific Solution via historical files (currently proposed in the YANG module): - implemented via some historical files retrieval of the historical files for specified snapshot-id, network-id and timestamp, and the file itself can have the same structure as a member of the list network: container networks-history { if-feature simap-lifecycle; config false; list network-history { key "live-network-ref timestamp"; description "Historical network. Snapshot is generated for each historical instance, network-ref is the reference for the live network"; leaf live-network-ref { type leafref { path "/nw:networks/nw:network/nw:network-id"; } leaf timestamp { type yang:date-and-time; } leaf file-id { type inet:uri; } } } Figure 4: The candidate 2 for snapshots * Candidate 3 - SIMAP Specific Solution via separate containers" - implemented via separate container, for read only. Instead of referencing the file, the whole yang structure for the network from the list-network is duplicated, except that all supporting Havel, et al. Expires 3 May 2027 [Page 12] Internet-Draft SIMAP Additional Features YANG Model October 2026 references must also point to snapshot id as well. This implementation is not proposed in the yang file in this draft version. container networks-history { if-feature simap-lifecycle; config false; list network-history-snapshot { key "network-ref snapshot-id" uses nt:network-ref; leaf snapshot-id { type inet:uri; } leaf timestamp { type yang:date-and-time; } container network-types { } list supporting-network { key "network-ref snapshot-id" leaf network-ref {} leaf snapshot-id {} } list node { leaf node-id {..} list supporting-node { key "network-ref snapshot-id node-ref"; ... } list termination-point { leaf tp-id {} list supporting-termination-point { key "network-ref snapshot-id node-ref tp-ref"; ... } } } list link { leaf link-id {..} list supporting-link { key "network-ref snapshot-id link-ref"; ... } } } Figure 5: The candidate 3 for snapshots Havel, et al. Expires 3 May 2027 [Page 13] Internet-Draft SIMAP Additional Features YANG Model October 2026 The candidate 2 with file reference is currently implemented in the YANG module, but our preference would be to use a generic mechanism for historical retrieval, as this is not SIMAP only requirement but also applicable to inventory and other modules. 4.4.3. REQ-POTENTIAL: Potential new network topology 4.4.3.1. Analysis SIMAP must enable both retrieval and write access to the potential new network. A potential new network is the view at a given point with modifications from the snapshot. This view may contain either the full topology or just differences from the snapshot. Running a "what-if" analysis requires the ability to take snapshots and to switch easily between them. This requires the implementation proposal to take into account the following: * SIMAP write is used for either what-if or intended scenarios, but we have to ensure that we can create multiple snapshots for what- if scenario * how to retrieve different what-if network instances * how to connect what-if snapshot with the historical snapshot, as the current topology may change and what-if snapshot was created based on the historical context * how to connect to the current network instance * how to model and retrieve potential network: either full topology or only changes from the snapshot * how to retrieve the external models via links in the what-if context * is this SIMAP requirement or generic requirement for any YANG retrieval via NETCONF/RESTCONF. The [RFC8342] defines different datastores: configuration datastores (startup, candidate, running, intended) and operational datastore. It can potentially be used for one candidate, but it does not support multiple candidates with links to different running. We have private candidates that can be potentially used. Please refer to Section 3 for analysis of multiple endpoints (sematics determined by the selection of the endpoint) versus single endpoint (semantics in the model). Havel, et al. Expires 3 May 2027 [Page 14] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.4.3.2. Implementation Proposal The following is the initial proposal: * provide a solution that would allow the live versus potential to be modeled via different endpoints(please see Section 3) * optionally, provide the solution for adding the semantics to the model: - use list network for potential as well - network-id is generated for each potential candidate - additional info needed: category (potential), timestamp, relation to the live network network-id - relation to historical snapshot may be determined based on the live network-id and timestamp Preferably, the generic solution with private candidates would be used, but for now we have the following modelled. identity network-category { description "Base identity for the network category"; } identity network-category-none { description "This is used when endpoint selection identifies if live, potential or intended. This is the default"; } identity network-category-potential { base "st:network-category"; description "Potential topology. There may be optionally one or multiple instances of the potential network, related to the current network. Timestamp determines what historical snapshot has been used when creating the potential network instance"; } augment "/nw:networks/nw:network" { if-feature simap-lifecycle; description "Adding optional capability for modelling of potential and intended network"; Havel, et al. Expires 3 May 2027 [Page 15] Internet-Draft SIMAP Additional Features YANG Model October 2026 leaf network-category { type identityref { base st:network-category; } description "The network category: none, live, potential, intended. Default is none."; } leaf live-network-ref { description "Required for potential and intended only to connect to the live network instance"; type leafref { path "/nw:networks/nw:network/nw:network-id"; require-instance false; } leaf timestamp { description "Required for potential only to connect to the historical snapshot"; type yang:date-and-time; } } Figure 6: The proposal for potential snapshots Check if this proposal has an issue with backward compatibility, as the read would return potential instances as well. Alternative is to have a separate list networks-potential. 4.4.4. REQ-INTENDED: Intended topology 4.4.4.1. Analysis SIMAP must enable both retrieval and write access to the intended network topology that cannot be discovered from the real network (for example target L2 Topology, L3 Topology, passive topology that cannot be discovered). This requires the implementation proposal to take into account the following: * how to connect intended to the current network instance Please refer to Section 3 for analysis of multiple endpoints (sematics determined by the selection of the endpoint) versus single endpoint (semantics in the model). Havel, et al. Expires 3 May 2027 [Page 16] Internet-Draft SIMAP Additional Features YANG Model October 2026 Preferably we would use NMDA and one of the datastores if possible, needs further analysis. 4.4.4.2. Implementation Proposal The following is the initial proposal: * provide a solution that would allow the live versus intended to be modeled via different endpoint (please see Section 3) * optionally, provide the solution for adding the semantics to the model: - use list network for intended as well - network-id is generated for intended network, different network-id from the live network - additional info needed: type: intended, relation to the live network network-id Preferably, the generic solution with standard datastored would be used if possible, but for now we have the following modelled. Havel, et al. Expires 3 May 2027 [Page 17] Internet-Draft SIMAP Additional Features YANG Model October 2026 identity network-category-none { description "This is used when endpoint selection identifies if live, potential or intended. This is the default"; } identity network-category-intended { base "st:network-category"; description "Intended topology, there is optionally 1 instance of intended network related to the live network instance"; } augment "/nw:networks/nw:network" { if-feature simap-lifecycle; description "Adding optional capability for modelling of potential and intended network"; leaf network-category { type identityref { base st:network-category; } description "The network category: live, potential, intended. Default is live."; } leaf live-network-ref { description "Required for potential and intended only to connect to the live network instance"; type leafref { path "/nw:networks/nw:network/nw:network-id"; require-instance false; } } : : } Figure 7: The proposal for intended snapshots Check if this proposal has an issue with backward compatibility, as the read would return potential instances as well. Alternative is to have a separate list networks-intended. 4.4.5. REQ-STATUS: Links and nodes down in topology Havel, et al. Expires 3 May 2027 [Page 18] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.4.5.1. Analysis Links and nodes that are down must appear in the topology. The status of the nodes and links must be either implemented in the SIMAP or accessible from the SIMAP. Whether the status is included as part of the SIMAP or accessible from the SIMAP is left to the solutions. Therefore, based on this requirement we must optionally support the status in SIMAP. 4.4.5.2. Implementation Proposal Options for showing links in the topology: * rely on the intended network for the target and the live network only shows the current topology * real network should include both intended network and the state that reflects the current status This draft proposes to use intended for the target state and that application can retrieve live and intended and compute the diff and merge them if needed. The draft also proposes to add status, if required, via REQ- EXTENSIBLE in Section 4.2.1. 4.4.6. REQ-TEMPO-HISTORY: Geo-spatial, temporal, historical 4.4.6.1. Analysis Move any relevant text from draft-havel-nmop-digital-map. TODO: Do we need to add timestamps here for temporal. Proposal for historical is done in REQ-SNAPSHOT. In regards to geo-spatial, there are 2 options: * refer to existing YANG module * implement here This draft proposes to link to the external 4.4.6.2. Implementation Proposal Proposal for historical is done via REQ-SNAPSHOT Proposal for geo- spacial is done via REQ-PLUGG TODO: Proposal for temporal requires further analysis Havel, et al. Expires 3 May 2027 [Page 19] Internet-Draft SIMAP Additional Features YANG Model October 2026 4.5. Feature simap-external The solution is proposed for the following requirements: * REQ-STD- API-BASED * REQ-PLUGG 4.5.1. REQ-STD-API-BASED: Standard based 4.5.1.1. Analysis RFC8345 already supports the standard model and API for the SIMAP requirements supported by RFC8345. We also need a standard model and API for the SIMAP requirements identified as RFC8345 gaps. This requirement also mentions that these APIs must also provide the capability to retrieve the links to external data/models. 4.5.1.2. Implementation Proposal The implementation for the model changes for this requirement will be covered by the implementation proposal for REQ-PLUGG in Section 4.5.2. 4.5.2. REQ-PLUGG: Pluggable 4.5.2.1. Analysis This requirement states that SIMAP must be pluggable and connect to other YANG modules and other nodelling mechanisms. 4.5.2.2. Implementation Proposal The solution for the external links is proposed in a separate draft [I-D.vivek-simap-external-relationship]. TODO - Check if there is alternative proposal with some simple references 5. Model Structure Details The SIMAP data model is defined in the "ietf-simap-feature" module. Its structure is shown in Figure 1. The notation syntax follows the syntax used in [RFC8340]. Havel, et al. Expires 3 May 2027 [Page 20] Internet-Draft SIMAP Additional Features YANG Model October 2026 module: ietf-simap-topology +--ro networks-history +--ro network-history* [live-network-ref timestamp] +--ro live-network-ref -> /nw:networks/network/network-id +--ro timestamp yang:date-and-time +--ro file-id? inet:uri augment /nw:networks/nw:network: +--ro extension? augment /nw:networks/nw:network/nw:node: +--ro extension? augment /nw:networks/nw:network/nw:node/nt:termination-point: +--ro extension? augment /nw:networks/nw:network/nt:link: +--ro extension? augment /nw:networks/nw:network: +--rw network-category? identityref +--rw live-network-ref? -> /nw:networks/network/network-id +--rw timestamp? yang:date-and-time Figure 8: The Structure of the SIMAP Data Model 6. YANG Module module ietf-simap-features { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-simap-features"; prefix st; import ietf-network { prefix nw; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-network-topology { prefix nt; reference "RFC 8345: A YANG Data Model for Network Topologies"; } organization "Network Management Operations (NMOP) Working Group"; contact "WG Web: WG List: Havel, et al. Expires 3 May 2027 [Page 21] Internet-Draft SIMAP Additional Features YANG Model October 2026 Editor: Olga Havel Editor: Nigel Davis Editor: TODO "; description "This module defines the SIMAP features model based on the requirements defined in https://datatracker.ietf.org/doc/draft-ietf-nmop-simap-concept/. Copyright (c) 2025 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices. "; revision 2025-27-10 { description "Initial revision."; reference "XXX: A YANG Data Model for SIMAP Features"; } /* * Common SIMAP groupings for optional RFC8345 extensions * Addressing requirements REQ-PROPERTIES as name, label and * description may be important properties that * clarify the topological roles for different layers and * technologies */ grouping simap-common { description "A reusable set of optional extensions for network, Havel, et al. Expires 3 May 2027 [Page 22] Internet-Draft SIMAP Additional Features YANG Model October 2026 node, termination point and link"; anydata extension { config false; description "The extension point for any other meta info or data or any unknown extensions. Proposed solution for SIMAP requirement REQ-EXTENSIBLE. Any additional info that is topologically significant can also be added this way for requirement REQ-TOPO-ONLY or REQ-PROPERTIES."; } } augment "/nw:networks/nw:network" { description "Adding optional common simap extensions"; uses st:simap-common; } augment "/nw:networks/nw:network/nw:node" { description "Adding optional common simap extensions"; uses st:simap-common; } augment "/nw:networks/nw:network/nw:node/nt:termination-point" { description "Adding optional common simap extensions"; uses st:simap-common; } augment "/nw:networks/nw:network/nt:link" { description "Adding optional common simap extensions"; uses st:simap-common; } /* * Candidate for potential (REQ-POTENTIAL) and intended * (REQ-INTENDED) topology requirement */ /* * Identities related to type of the network: * live, potential, intended */ identity network-category { description "Base identity for the network category"; } Havel, et al. Expires 3 May 2027 [Page 23] Internet-Draft SIMAP Additional Features YANG Model October 2026 identity network-category-none { description "This is used when endpoint selection identifies if live, potential or intended. This is the default"; } identity network-category-live { base "st:network-category"; description "Live topology, there is only 1 instance of the live network"; } identity network-category-potential { base "st:network-category"; description "Potential topology. There may be optionally one or multiple instances of the potential network, related to the current network"; } identity network-category-intended { base "st:network-category"; description "Intended topology, there is optionally 1 instance of intended network related to the live network instance"; } augment "/nw:networks/nw:network" { description "Adding optional capability for modelling of potential and intended network"; leaf network-category { type identityref { base st:network-category; } description "The network category: live, potential, intended. Default is live."; } leaf live-network-ref { description "Required for potential and intended only to connect to the live network instance"; type leafref { path "/nw:networks/nw:network/nw:network-id"; require-instance false; } } Havel, et al. Expires 3 May 2027 [Page 24] Internet-Draft SIMAP Additional Features YANG Model October 2026 leaf timestamp { description "Required for potential only to find related historical snapshot"; type yang:date-and-time; } } /* * Candidate for graph traversal (REQ-GRAPH-TRAVERSAL) * topology requirement (tp->tp, node->node) */ augment "/nw:networks/nw:network/nw:node/nt:termination-point" { description "Adding optional read only link relations between connected termination points for optimized graph traversal for paths"; list linked-termination-point { config false; key "network-ref node-ref tp-ref"; description "This list identifies any linked termination points, added optionally for read only for optimized path graph traversal"; uses nt:tp-ref; } augment "/nw:networks/nw:network/nw:node" { description "Adding optional read only link relations between connected nodes for optimized graph traversal for paths"; list linked-node { config false; key "network-ref node-ref"; description "This list identifies any linked nodes, added optionally for read only for optimized path graph traversal"; uses nw:node-ref; } /* * Networks history, requirement REQ-SNAPSHOT */ Havel, et al. Expires 3 May 2027 [Page 25] Internet-Draft SIMAP Additional Features YANG Model October 2026 container networks-history { config false; list network-history { key "live-network-ref timestamp"; description "Historical network. Snapshot is generated for each historical instance, network-ref is the reference for the live network"; leaf live-network-ref { type leafref { path "/nw:networks/nw:network/nw:network-id"; } } leaf timestamp { type yang:date-and-time; } leaf file-id { type inet:uri; } } } } Figure 9: The YANG Data Model for SIMAP Features 7. Security Considerations 8. IANA Considerations This document has no actions for IANA. 9. Normative References [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- 15, 23 October 2026, . [I-D.vivek-simap-external-relationship] Boudia, V., Francois, P., and S. Mostafa, "External Relationship model for SIMAP", Work in Progress, Internet- Draft, draft-vivek-simap-external-relationship-00, 7 July 2025, . Havel, et al. Expires 3 May 2027 [Page 26] Internet-Draft SIMAP Additional Features YANG Model October 2026 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [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, . [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, . Acknowledgments Authors' Addresses Olga Havel Huawei Email: olga.havel@huawei.com Nigel Davis Ciena Email: ndavis@ciena.com Oscar Gonzalez de Dios Telefonica Email: oscar.gonzalezdedios@telefonica.com Thomas Graf Swisscom Email: thomas.graf@swisscom.com Havel, et al. Expires 3 May 2027 [Page 27]