Network Working Group R. Wilton, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track R. Rahman Expires: 6 January 2027 Equinix J. Clarke Cisco Systems, Inc. J. Sterne Nokia 5 July 2026 YANG Packages draft-ietf-netmod-yang-packages-08 Abstract This document defines YANG packages: versioned organizational structures used to manage the schema and conformance of a set of YANG modules as a cohesive unit. 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 6 January 2027. Copyright Notice Copyright (c) 2026 IETF Trust and the persons identified as the document authors. All rights reserved. Wilton, et al. Expires 6 January 2027 [Page 1] Internet-Draft YANG Packages July 2026 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Main Objectives . . . . . . . . . . . . . . . . . . . . . 4 1.2. Potential Alternative Mechanisms . . . . . . . . . . . . 5 1.3. Open Questions/Issues . . . . . . . . . . . . . . . . . . 6 2. Terminology and Conventions . . . . . . . . . . . . . . . . . 6 3. The YANG Package Definition . . . . . . . . . . . . . . . . . 8 3.1. Package definition rules . . . . . . . . . . . . . . . . 10 3.2. Schema referential completeness . . . . . . . . . . . . . 11 3.2.1. Incomplete package dependencies . . . . . . . . . . . 12 3.3. Submodule package considerations . . . . . . . . . . . . 12 3.4. Package Mount Points . . . . . . . . . . . . . . . . . . 12 3.5. Exclusions . . . . . . . . . . . . . . . . . . . . . . . 13 4. Package Resolution . . . . . . . . . . . . . . . . . . . . . 13 4.1. Automatic Module Version Resolution . . . . . . . . . . . 16 5. YANG Package Usage . . . . . . . . . . . . . . . . . . . . . 17 5.1. Achieving package name uniqueness . . . . . . . . . . . . 18 5.2. Specifying modules as implemented or import-only . . . . 18 5.3. Referential completeness and YANG packages . . . . . . . 19 5.4. Providing Package Definitions on a Server . . . . . . . . 19 5.4.1. Package List . . . . . . . . . . . . . . . . . . . . 20 5.4.2. Tree diagram . . . . . . . . . . . . . . . . . . . . 20 5.4.3. YANG Library Package Bindings . . . . . . . . . . . . 20 5.5. Package Instance Data Files . . . . . . . . . . . . . . . 21 5.6. YANG packages as schema for YANG instance data document . . . . . . . . . . . . . . . . . . . . . . . . 23 6. Package Evolution and Versioning . . . . . . . . . . . . . . 25 6.1. Package versioning . . . . . . . . . . . . . . . . . . . 25 6.1.1. Updating a package with a new version . . . . . . . . 26 6.1.1.1. Non-Backwards-compatible changes . . . . . . . . 26 6.1.1.2. Backwards-compatible changes . . . . . . . . . . 27 6.1.1.3. Editorial changes . . . . . . . . . . . . . . . . 28 6.1.2. Guidelines for Package Versions During Package Development . . . . . . . . . . . . . . . . . . . . . 28 7. Package Conformance . . . . . . . . . . . . . . . . . . . . . 28 7.1. Resolving conflicting module versions in included packages . . . . . . . . . . . . . . . . . . . . . . . . 29 7.2. Handling multiple included package versions . . . . . . . 29 Wilton, et al. Expires 6 January 2027 [Page 2] Internet-Draft YANG Packages July 2026 7.3. Exclusions and Deviations . . . . . . . . . . . . . . . . 30 7.4. Use of features in YANG modules and YANG packages . . . . 30 7.5. Use of YANG semantic versioning for YANG packages . . . . 31 7.6. Restrictions on the use of deviations in YANG packages . 31 7.7. The relationship between packages and datastores . . . . 32 7.8. Using package comparison tools . . . . . . . . . . . . . 33 8. YANG Modules . . . . . . . . . . . . . . . . . . . . . . . . 34 8.1. ietf-yang-package-types . . . . . . . . . . . . . . . . . 34 8.2. ietf-yang-package-instance . . . . . . . . . . . . . . . 48 8.3. ietf-yang-package . . . . . . . . . . . . . . . . . . . . 49 8.4. ietf-yl-packages . . . . . . . . . . . . . . . . . . . . 52 8.5. ietf-yang-inst-data-pkg . . . . . . . . . . . . . . . . . 55 9. YANG Package Instance Data Schema . . . . . . . . . . . . . . 58 10. Security Considerations . . . . . . . . . . . . . . . . . . . 60 10.1. YANG Module Security Considerations . . . . . . . . . . 60 11. Operational Considerations . . . . . . . . . . . . . . . . . 61 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 62 12.1. IANA YANG Module and Namespace Registrations . . . . . . 62 12.2. IETF YANG Package Registry . . . . . . . . . . . . . . . 63 12.3. Media Type Registration for application/ypkg . . . . . . 64 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 64 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 65 14.1. Normative References . . . . . . . . . . . . . . . . . . 65 14.2. Informative References . . . . . . . . . . . . . . . . . 67 Appendix A. Package Examples . . . . . . . . . . . . . . . . . . 68 A.1. Basic Package Examples . . . . . . . . . . . . . . . . . 68 A.1.1. Example Basic Types YANG package, version 1.0.0 . . . 69 A.1.2. Example Basic Types YANG package, version 1.1.0 . . . 70 A.1.3. Example Network Device YANG package . . . . . . . . . 72 A.1.4. Example Routing Types YANG package . . . . . . . . . 74 A.1.5. Example Basic Routing YANG package . . . . . . . . . 76 A.2. Device Implementation Examples . . . . . . . . . . . . . 79 A.2.1. device-routing YANG package . . . . . . . . . . . . . 79 A.2.2. YANG library advertisement for device-routing . . . . 81 A.2.3. Hotfix Package Example . . . . . . . . . . . . . . . 83 A.3. Package Versioning Examples . . . . . . . . . . . . . . . 85 A.3.1. Initial Package Version . . . . . . . . . . . . . . . 86 A.3.2. Backwards-compatible Update . . . . . . . . . . . . . 87 A.3.3. Package Downref and Module Removal . . . . . . . . . 89 A.3.4. Adding a Deviations Module . . . . . . . . . . . . . 91 A.3.5. Mixed Backwards-compatible and NBC Changes . . . . . 93 A.3.6. Editorial Location Update . . . . . . . . . . . . . . 94 A.4. Package Resolution Examples . . . . . . . . . . . . . . . 95 A.4.1. Recursive Package Resolution . . . . . . . . . . . . 96 A.4.2. Local Entries and Exclusions . . . . . . . . . . . . 103 A.5. Package Exclusion Examples . . . . . . . . . . . . . . . 105 A.5.1. Example of excluding modules and an enabled feature . . . . . . . . . . . . . . . . . . . . . . . 106 Wilton, et al. Expires 6 January 2027 [Page 3] Internet-Draft YANG Packages July 2026 A.6. Mounted Package Examples . . . . . . . . . . . . . . . . 110 A.6.1. Example of package with a mounted package . . . . . . 110 A.6.2. Example of a package replacing the mounted schema . . 110 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 110 1. Introduction This document defines and describes the YANG [RFC7950] constructs that are used to define and use YANG packages. A YANG package is a versioned hierarchical organizational structure used to manage a set of YANG modules that collectively define a package schema. For example, a YANG package could define the set of YANG modules required to implement an L2VPN service on a network device. YANG packages can be: exported from a server, resolved into a YANG schema, augmented into YANG library [RFC8525], accessed as instance data files [RFC9195], with a dedicated .ypkg file suffix, used to define the schema of data in instance data files, and used by tooling to compare and manage YANG schema. Examples of YANG packages are provided in the appendices. 1.1. Main Objectives The main goals of YANG package definitions include, but are not restricted to: * Providing an alternative, simplified, YANG conformance mechanism. Rather than conformance being performed against a set of individual YANG module revisions, features, and deviations, conformance can be more simply stated in terms of YANG packages, with a set of modifications (e.g. additional modules, deviations, or features). * Allowing datastore schema to be specified concisely rather than having each server explicitly list all modules, deviations, and features. YANG package definitions can be defined in documents Wilton, et al. Expires 6 January 2027 [Page 4] Internet-Draft YANG Packages July 2026 that are available offline, and may be accessible via a URL rather than requiring explicit lists of modules to be shared between client and server. Hence, a YANG package must contain sufficient information to allow a client or server to precisely construct the schema associated with the package. * YANG packages should be able to represent the equivalent structure as YANG library, but making use of a hierarchical resolution mechanism. * YANG packages should be flexible enough to provide usable definitions representing collections of IETF YANG modules, OpenConfig YANG modules, and other bespoke sets of YANG modules, e.g., covering sets of vendor native YANG models. * YANG packages should be flexible enough to represent the conformance and server implementations of standard or industry defined YANG package definitions. E.g., it should be possible for a server implementation to indicate that it does not faithfully implement a package schema, e.g., by excluding modules, implementing different module versions/revisions, and/or having deviations applied. * Tooling should be able to easily work with YANG package definitions to compare YANG package versions and to compare server conformance against expected package definitions. Protocol mechanisms of how clients can negotiate which YANG packages or YANG package versions are to be used for NETCONF/RESTCONF communications are outside the scope of this document. One potential mechanism is defined in [I-D.ietf-netmod-yang-ver-selection]. Finally, the package definitions proposed by this document are intended to be relatively basic in their definition and the functionality that they support. As the industry gains experience using YANG packages, the standard YANG mechanisms of updating, or augmenting YANG modules could also be used to extend the functionality supported by YANG packages, if required. 1.2. Potential Alternative Mechanisms There are several alternative approaches to managing YANG schema. These include: * Using YANG library, along with YANG Instance Data files [RFC9195], * Using git tags and version labels for modules maintained on GitHub, Wilton, et al. Expires 6 January 2027 [Page 5] Internet-Draft YANG Packages July 2026 * As collections of YANG modules in a zip file or at a directory folder. E.g., at time of publication, this method is used to represent the set of YANG modules associated with a particular vendor release at the GitHub repository at https://github.com/YangModels/yang Although these methods are quite simple, there are some disadvantages with various aspects of these methods: They are verbose, they don't advertise supported features or support mounts, and they can be awkward to compare, particularly if YANG modules haven't been versioned correctly. 1.3. Open Questions/Issues RFC Editor, please remove this section before publication. All issues, along with the draft text, are currently being tracked at https://github.com/rgwilton/YANG-Packages-Draft/issues/ 2. Terminology and Conventions 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. This document uses the following terminology introduced in YANG Semantic Versioning [I-D.ietf-netmod-yang-semver]: * YANG Semver This document uses the following terminology introduced in the Network Management Datastore Architecture [RFC8342]: * datastore schema This document uses the following terminology introduced in the YANG 1.1 Data Modeling Language [RFC7950]: * data node * schema node Tree diagrams used in this document follow the notation defined in [RFC8340]. In addition, this document defines the following terminology: Wilton, et al. Expires 6 January 2027 [Page 6] Internet-Draft YANG Packages July 2026 * version (module): In the context of a YANG module, it is used as shorthand to reference a particular revision of a YANG module, potentially identified by a YANG Semver version label or a revision-date. * version (package): In the context of a YANG package, it refers to a particular version of a YANG package definition, identified by the package version field. * YANG schema: The combined set of schema nodes for a set of modules taking into account implemented modules, import-only modules, deviations, features and mount-points. A more complete definition is provided in Section 4. * YANG package: The versioned organizational structure defined in Section 3. Depending on context, the term 'YANG package' is often used to refer to a specific version of a YANG package rather than all versions of a package definition. * package: An alternative term for 'YANG package'. * backwards-compatible (BC) change: When used in the context of a YANG module, it follows the definition in Section 3.1.1 of [I-D.ietf-netmod-yang-module-versioning]. When used in the context of a YANG package, it follows the definition in Section 6.1.1.2. * non-backwards-compatible (NBC) change: When used in the context of a YANG module, it follows the definition in Section 3.1.2 of [I-D.ietf-netmod-yang-module-versioning]. When used in the context of a YANG package, it follows the definition in Section 6.1.1.1. * editorial change: When used in the context of a YANG module, it follows the definition of an 'editorial change' in 4.4 of [I-D.ietf-netmod-yang-semver]. When used in the context of a YANG package, it follows the definition in Section 6.1.1.3. * resolved package schema: The resolved package schema is the YANG schema defined by a package after package resolution has been performed, as defined in Section 4. The resolved package schema identifies the implemented modules (with any deviations applied), import-only modules, enabled features, and schema mount points. * package schema: An alternative term for 'resolved package schema'. Wilton, et al. Expires 6 January 2027 [Page 7] Internet-Draft YANG Packages July 2026 * enabled feature: A YANG module feature that a resolved package schema identifies as mandatory to enable for all implementations that conform to the package definition. 3. The YANG Package Definition A YANG package is a versioned hierarchical organizational structure used to manage a set of YANG modules that collectively define a package schema. Each YANG package defines: * YANG package meta-data, such as "name", "version", "organization", "description", "complete" flag, etc. * An "includes" container holding a list of included packages. It also contains lists of any implemented modules and import-only modules that are used in addition to, or with different version to, the modules defined in the included packages. Finally, it lists enabled features in addition to those defined in included packages. * An "excludes" container comprising modules and features that are included via the resolved packages of entries in the "includes/ package" list, but that are excluded from this package definition. It is not possible to exclude packages. * Lists of YANG packages that will be found at particular mount points by any server implementing this package, used in conjunction with mount points defined by any included packages. The ietf-yang-package-types.yang module defines a grouping to specify the core elements of the YANG package structure that is used within YANG package instance data files (ietf-yang-package-instance.yang) and also on the server (ietf-yang-packages.yang). The "yang-pkg-instance" grouping in the "ietf-yang-package-types" YANG module has the following structure: module: ietf-yang-package-types grouping yang-pkg-instance: +-- name pkg-name +-- version pkg-version +-- version-description? string +-- timestamp? yang:date-and-time +-- organization? string +-- contact? string Wilton, et al. Expires 6 January 2027 [Page 8] Internet-Draft YANG Packages July 2026 +-- description? string +-- reference? string +-- complete? boolean +-- includes | +-- package* [name version] | | +-- name pkg-name | | +-- version pkg-version | | +-- location* inet:uri | +-- module* [name] | | +-- name module-name | | +-- version version-or-rev-date | | +-- location* inet:uri | | +-- submodule* [name] | | +-- name module-name | | +-- version version-or-rev-date | | +-- location* inet:uri | +-- import-only-module* [name version] | | +-- name module-name | | +-- version version-or-rev-date | | +-- location* inet:uri | | +-- submodule* [name] | | +-- name module-name | | +-- version version-or-rev-date | | +-- location* inet:uri | +-- feature* scoped-feature +-- excludes | +-- module* module-name | +-- import-only-module* [name] | | +-- name module-name | | +-- version* version-or-rev-date | +-- feature* scoped-feature +-- depends-on | +-- package* [name version] | +-- name pkg-name | +-- version pkg-version | +-- location* inet:uri +-- mount* [mount-path] +-- mount-path mount-ypath +-- inherit-packages? boolean +-- package* [name version] | +-- name pkg-name | +-- version pkg-version | +-- location* inet:uri +-- additional-feature* scoped-feature +-- parent-reference* mount-ypath Wilton, et al. Expires 6 January 2027 [Page 9] Internet-Draft YANG Packages July 2026 3.1. Package definition rules For a YANG package to be valid, it MUST conform to all the following rules: 1. Each (package name, version) pairing MUST define a globally unique version of that package definition. 2. Each YANG package name MUST be globally unique to avoid issues with tools and caching, e.g., using the mechanisms specified in Section 5.1. 3. YANG packages MUST be versioned using YANG Semver, [I-D.ietf-netmod-yang-semver]. Versioning YANG packages is further described in Section 6.1. 4. A YANG package MAY represent a referentially complete set of modules or MAY represent a set of modules with some module import dependencies missing, as described in Section 3.2. 5. Package definitions are hierarchical because a package can include other packages. There MUST NOT be any circular package include dependencies, i.e., packages cannot, directly or indirectly, include themselves. 6. A package definition MAY directly include multiple versions of the same package in the "includes/package" list, but normally only a single package version is expected. Multiple package versions can be listed, for example, to update location information for package versions included through other packages. 7. If the same package version, module version, import-only module version, or submodule version is referenced via multiple included packages, then the referenced content and metadata are expected to be equivalent. Location information MAY differ and is merged as defined by the package resolution rules in Section 4. 8. When a location leaf-list is provided for a package, implemented module, import-only module, or submodule, the first entry MUST be the canonical location used to retrieve that package, module, import-only module, or submodule. Wilton, et al. Expires 6 January 2027 [Page 10] Internet-Draft YANG Packages July 2026 9. For each module implemented by a package, only a single version/ revision of that module MUST be implemented. Conflicting module versions (e.g. from package includes) MAY be resolved explicitly (via "includes/module") or using automatic module version resolution, as described in Section 4.1. 10. Multiple versions/revisions of an import-only module MAY be listed, but any extraneous import-only module versions SHOULD be removed. 11. A package definition MUST NOT include the same module name in both the 'includes/module' and 'excludes/module' lists. 12. A package definition MUST NOT include and exclude the same import-only module version. If an 'excludes/import-only-module' entry does not list any versions, then it excludes all versions of that import-only module and MUST NOT be used with any 'includes/import-only-module' entry for the same module name. 13. A package definition MUST NOT include the same feature name in both the 'includes/feature' and 'excludes/feature' lists. 14. A package definition MUST NOT exclude a module and list features defined by that module in the 'includes/feature' list. 15. A package definition MAY include redundant information, e.g., including a module or package version that is already present by an included package, or excluding a module that is not included by any included package. However, such redundant information might be confusing to readers. Although the resolved package schema is unambiguous, it is best to minimize redundant information where possible. 16. Finally, standard rules for YANG instance data apply. E.g., entries in the various lists MUST be unique by any list key. 3.2. Schema referential completeness A YANG package may represent a schema that is 'referentially complete', or 'referentially incomplete', indicated in the package definition by the 'complete' flag. Wilton, et al. Expires 6 January 2027 [Page 11] Internet-Draft YANG Packages July 2026 If all import statements in all YANG modules included in the package (either directly, or through included packages) can be resolved to a module version defined with the YANG package definition, then the package is classified as being referentially complete. Conversely, if one or more import statements cannot be resolved to a module specified as part of the package definition, then the package is classified as being referentially incomplete. Also see Section 5.3 for details on cases when referentially incomplete packages are helpful. 3.2.1. Incomplete package dependencies When a package is referentially incomplete, the "depends-on/package" list can identify other package versions that are expected to be resolved along with the incomplete package to produce a complete schema. This provides a machine-readable indication of the packages that supply missing import dependencies or other schema context needed by the incomplete package. The "depends-on/package" list is not equivalent to the "includes/ package" list. Packages listed in "depends-on/package" are not included as part of the incomplete package definition itself and do not, by themselves, change the resolved schema represented by that package. Instead, they identify additional package definitions that a server or client can use when constructing a complete schema from the incomplete package. 3.3. Submodule package considerations As defined in [RFC7950] and [I-D.ietf-netmod-yang-semver], YANG conformance and versioning is specified in terms of particular versions of YANG modules rather than for individual submodules. However, YANG package definitions also include the list of submodules included by a module, primarily to provide user-ordered locations where each submodule definition can be obtained from. If multiple locations are provided, the canonical location of where the submodule definition can be obtained SHOULD be listed first. 3.4. Package Mount Points YANG Schema Mount [RFC8528] defines a mechanism for YANG modules to be mounted at specific mount points in the schema tree. This mechanism is required to instantiate the full schema for some common networking use cases, e.g., [RFC8529] defines a YANG Model for Network Instances, that uses YANG mount points to mount IETF routing protocol YANG modules within the network instance list. Wilton, et al. Expires 6 January 2027 [Page 12] Internet-Draft YANG Packages July 2026 [RFC8528] declares that it provides support for mounted schema at "Implementation time" and "Run time", but does not cover mounting schema at "Design time". YANG package definitions do not give YANG language level "Design time" guarantees, but they are able to give a stronger "Implementation time" guarantee through the use of offline YANG package definitions. They can also be used to report "Run time" mounted schema behavior, if the server is able to report the packages implemented by the device. Each YANG package definition defines the package schema, additional features, and parent-references found at a particular mount point, via two mechanisms: * Mounted packages, additional features, and parent-references that are exported from any included packages are also exported at the same mount point for this specific package, unless package inheritance is explicitly disabled by a 'mount' list entry for the same mount point with 'inherit-packages' set to 'false'. * A package definition can add mounted packages, additional features, and parent-references to a mount point by listing them in the 'mount' list entry. These entries are additive, like entries in the 'includes/package' list. If the same package name is listed with a different version, then both package versions are retained. I.e., a package definition can remove inherited mounted packages, modules, enabled features, or parent-references only by setting 'inherit-packages' to 'false' and explicitly listing the packages, features, and parent-references that define the complete mounted schema. Examples of this are given in Appendix A.6.2. If a server implements the YANG library package bindings defined in Section 5.4.3 for a mounted schema, then the YANG library data provided at the mount point MUST include the 'package' list, and any applicable 'additional-feature' leaf-list entries, defined by the "ietf-yl-packages" module, Section 5.4.3. 3.5. Exclusions A package definition may exclude modules or enabled features. The mechanism for this is described in Section 4, and the conformance implications are described in Section 7. 4. Package Resolution Package resolution is the process of taking a YANG package definition and converting it to a specification for a YANG schema, e.g., as may be implemented by a device for a particular datastore. A YANG schema can be thought of as comprising: Wilton, et al. Expires 6 January 2027 [Page 13] Internet-Draft YANG Packages July 2026 A set of implemented modules at specific versions, A set of import-only modules, potentially with multiple versions of a given module, A set of enabled features, A set of mount points, each with its own YANG schema, that can be collectively compiled into a YANG schema tree. The YANG schema generated by a package definition can be converted into an equivalent instance in YANG library [RFC8525], with Schema Mount [RFC8528] if mount points are used. E.g., see Section 5.4.3. The following process defines how a YANG package definition is resolved, using two explicit steps: 1. Step 1: recursively resolve each package in the "includes/ package" list using this same two-step process. 2. Step 2: merge the resolved package schemas from those included packages with the local entries defined directly by this package. The local entries are the contents of the "includes", "excludes", and "mount" containers in this package. The merge is performed using the following rules: * included-packages: The set of included package references is the union of all included package references in the resolved included packages, then overwritten, including location information, by any entries in the local "includes/package" list with the same package name and version. Location leaf- lists for duplicate inherited package references are merged using the location-lists rule. * implemented-modules: The set of implemented modules is the union of all implemented modules in the resolved included packages. Conflicting module versions can be resolved automatically as per Section 4.1, then overwritten (including submodule and location information) by any entries in the "includes/module" list, and finally filtered by any entries in "excludes/module" list. Location leaf-lists for duplicate inherited module references are merged using the location- lists rule. * import-only-modules: The set of import-only modules is the union of all import-only modules in the resolved included packages. Location leaf-lists for duplicate inherited import- Wilton, et al. Expires 6 January 2027 [Page 14] Internet-Draft YANG Packages July 2026 only module references are merged using the location-lists rule. The set is then overwritten (including submodule and location information) by any entries in the "includes/import- only-module" list with the same module name and version, and finally filtered by any entries in the "excludes/import-only- module" list. * enabled-features: The set of enabled features is the union of the enabled features from the resolved included packages, with any "includes/feature" entries added, and any "excludes/ feature" entries removed. If a module is excluded by "excludes/module" then all features associated with that module are also implicitly removed. * mounts: The set of mounts is the union of the mounts in the resolved included packages, where for a given mount-path that is present in more than one included package (exact same path and bound list keys) then it takes the union of the mounted packages, "mount/additional-feature" entries, and mount parent-references. The mounts are then updated by processing any entries in the package's "mount" list. If "inherit- packages" is true, or absent, the local "mount/package", "mount/additional-feature", and "mount/parent-reference" entries are added to the inherited mounted schema for that mount point. If the same package version is present in both the inherited and local "mount/package" entries, then the local entry overwrites the inherited entry, including location information. If the same package name is present with different package versions, then all package versions are retained. If "inherit-packages" is false, the inherited mounted packages, additional features, and parent-references for that mount point are discarded, and the local "mount" entry defines the mounted schema for that mount point. * submodules: Submodules are ignored for resolution purposes, only the module version is considered and compared. For duplicate inherited references to the same submodule version, location leaf-lists are merged using the location-lists rule. * location-lists: This rule applies when duplicate inherited package, module, import-only module, or submodule references identify the same version but have different location leaf- list values. The referenced content and metadata are expected to be equivalent. The location leaf-lists are merged pairwise in the order that the included package entries are listed. For each pairwise merge, values from the second location leaf- list are appended to the first location leaf-list, except that values already present in the first location leaf-list are Wilton, et al. Expires 6 January 2027 [Page 15] Internet-Draft YANG Packages July 2026 ignored. Hence, the first occurrence of each location is retained and the relative order of non-duplicate locations is preserved. 4.1. Automatic Module Version Resolution A resolved package schema can only include a single version of a module, and hence when conflicting module versions arise from included packages that resolve to different versions of a given module then a single version has to be chosen. The following rules are used, in the order given, to automatically select the chosen version by performing a pairwise comparison of the module versions from the resolved included packages, by comparing the version leaves: 1. If both version leaves match the YANG Semver format, then they are compared using only the MAJOR, MINOR, and PATCH version components, as described in Section 4.3 of [I-D.ietf-netmod-yang-semver] and Section 4.4 of [I-D.ietf-netmod-yang-semver]. Any "_compatible" or "_non_compatible" modifier, pre-release metadata, and build metadata are ignored for this comparison: i The module with the highest MAJOR version component is chosen. ii Otherwise, if the MAJOR version components are the same, then the module with the highest MINOR version component is chosen. iii Otherwise, the module with the highest PATCH version component is chosen. 2. If one module has a version statement that matches the YANG Semver format but the other does not, then the module with the version statement matching the YANG Semver format is chosen. 3. If neither module has a version statement that matches the YANG Semver format, then the module with the most recent revision-date is chosen. 4. If there is no difference in version or revision-dates to distinguish between two modules then: i Submodule information, if present, for both module definitions is assumed to be equivalent and hence either can be used. Wilton, et al. Expires 6 January 2027 [Page 16] Internet-Draft YANG Packages July 2026 ii the location leaf-lists for the module definitions are merged using the location-lists rule. 5. YANG Package Usage This section provides information and guidance on how YANG packages can be used. YANG packages can be defined and used for different purposes: * By standards development organizations and industry organizations - to specify common sets of YANG data models that can be used together to manage network devices, or even just particular functionality on network devices (e.g., L3VPN services). Since package definitions can be defined hierarchically, packages defining different functionalities can be combined into larger package definitions that define more complex and complete behavior and YANG schema. These package definitions may be published by the organizations as package files. * For devices: - to describe the YANG schema associated with the device or a datastore schema on the device. These package schemas can be made available both from the device and also in offline package files. - to define different optional YANG schemas that can be used by the device and where clients can select which YANG schema can be used via configuration. - to refine standards based and industry packages to accurately report how the device does not fully conform to the package schema definition. * To manage and report the schema available at YANG schema mounts points. It is RECOMMENDED that organizations publishing YANG modules also publish YANG package definition that group and version those modules into units of related functionality. This increases interoperability by encouraging different implementations to coalesce around use the same collections of YANG modules versions. Using packages also makes it easier to understand relationship between modules, and enables functionality to be described on a more abstract level than individual modules. Wilton, et al. Expires 6 January 2027 [Page 17] Internet-Draft YANG Packages July 2026 Where possible, package definitions SHOULD be made available offline in Package Instance Data files, see Section 5.5, but also on the device as a list of known packages and relationships between YANG library datastore schema and equivalent YANG package definitions, e.g., see Section 5.4. 5.1. Achieving package name uniqueness As per Section 3.1, YANG package names are globally unique, since two different package definitions with the same name, but different content, cannot both be used together within the same package definition. There are a couple of ways of achieving this uniqueness requirement: * For package definitions that define a public API, or that could apply to multiple servers exposing the same management API, then an organization prefix, and perhaps device family name, should be included in the package name, i.e., following a similar naming convention as for modules. * For package definitions that are entirely local to a particular server or device, then the sysName of the device, a MAC address, or a UUID should be used as a suffix to the package name to ensure uniqueness. 5.2. Specifying modules as implemented or import-only Some YANG modules do not define any implementable data nodes, RPCs, Actions, or Notifications. These YANG modules often may include 'types' in the name of the YANG Module. For YANG package definitions, there is a choice whether to include these types modules in the packages list of implemented modules, or as import-only modules. This document does not specify how these should be declared, but instead gives some points of consideration that may be helpful when choosing. These are: Listing a "types-only" module as implemented allows for simpler automatic module version selection between different packages, as per Section 4.1. As per [RFC7950] section 9.10.2, identities are only available for use by the server for implemented modules. Wilton, et al. Expires 6 January 2027 [Page 18] Internet-Draft YANG Packages July 2026 If a module defines data nodes and types and the server only wants to use the types but not implement any data nodes from the module then listing the module as import-only is clearer and simpler than marking it as implemented with a separate deviation file that deviates all data nodes as not-supported. If a module imports a module at an exact revision (which, as per [I-D.ietf-netmod-yang-module-versioning], is not recommended) then it may be helpful to list that module in the import-only module list (even if implemented) to ensure that the import dependency is always satisfied. 5.3. Referential completeness and YANG packages Referentially incomplete packages can be used, along with locally scoped packages, to represent an update to a device's datastore schema as part of an optional software hot fix. E.g., the base software is made available as a complete globally scoped package. The hot fix is made available as an incomplete globally scoped package. A device's datastore schema can define a local package that implements the base software package updated with the hot fix package. An example is provided in Appendix A.2.3. Referentially incomplete packages could also be used to group sets of logically related modules together, but without requiring a fixed dependency on all imported 'types' modules (e.g., iana-if- types.yang), instead leaving the choice of specific versions of 'types' modules to be resolved when the package definition is used. 5.4. Providing Package Definitions on a Server A client discovers the package definitions for a datastore schema by first retrieving YANG Library. For each YANG Library schema entry, the augmented 'package' list, if present, identifies the top-level package name/version pairs that define that datastore schema. Those package references identify entries in the server's top-level '/packages/package' list. A client can use the package definition advertised by the server, retrieve a package instance data file from one of the advertised 'location' URIs, or use a cached package instance data file for the same package name and version. The client then resolves the listed packages, together with any 'additional- feature' entries to construct the complete datastore schema, as described in Section 5.4.3. Wilton, et al. Expires 6 January 2027 [Page 19] Internet-Draft YANG Packages July 2026 5.4.1. Package List A top level 'packages' container holds the list of all versions of all packages known to the server. Entries in this list do not necessarily mean that the package is implemented by the server or currently active for any datastore. Instead, the YANG Library package bindings in Section 5.4.3 are used to indicate which of the advertised packages are supported by each datastore schema. The '/packages/package' list MAY include multiple versions of a particular package. E.g. if the server is capable of allowing clients to select which package versions should be used by the server, or if package versions have been changed via applying different software packages or hot fixes. 5.4.2. Tree diagram The "ietf-yang-packages" YANG module has the following structure: module: ietf-yang-packages +--ro packages +--ro package* [name version] // Uses the yang-package-instance grouping defined in // ietf-yang-package-types.yang. +--ro name pkg-name +--ro version pkg-version ... remainder of yang-package-instance grouping ... 5.4.3. YANG Library Package Bindings The ietf-yl-packages module augments YANG library to provide a concise alternative approach of using hierarchical packages to define datastore schema compared to constructing the schema using a union of more verbose module definitions defined in module-sets. Since packages can be made available offline in instance data files, and cached, it may be sufficient for a client to only fetch the names/versions of the top level packages, along with the list of additional-feature entries to construct the full datastore schema. If multiple packages are listed for a datastore schema then they are resolved as if the packages were all directly included in a single package definition, including all additional-feature entries, and following the standard package resolution rules in Section 4. This means that conflicting module versions between the listed packages are resolved using the automatic module version resolution rules in Section 4.1. As a result, the version that wins those rules Wilton, et al. Expires 6 January 2027 [Page 20] Internet-Draft YANG Packages July 2026 is selected in the resolved package schema. This allows an extra 'bugfix' package to be added to the list of packages defining a schema to provide a later module version, but it cannot be used to select an older module version. Instead, a package that explicitly includes and refines the referenced packages would need to be defined to select the older module version (see Section 7.1). If populated, the set of packages listed for a datastore schema combined with the leaf-list of additional-feature entries MUST resolve to a schema that exactly matches the schema defined by the YANG library 'schema/module-set' leaf-list, and the resolved package schema MUST be referentially complete. Since these nodes augment into YANG library, then as per [RFC8525], the "/yang-library/content-id" leaf is updated if the packages or additional-feature entries change. The "ietf-yl-packages" YANG module has the following structure: module: ietf-yl-packages augment /yanglib:yang-library/yanglib:schema: +--ro package* [name version] | +--ro name -> /pkgs:packages/package/name | +--ro version leafref | +--ro location* inet:uri +--ro additional-feature* pkg-types:scoped-feature 5.5. Package Instance Data Files YANG packages SHOULD be made available offline from the server, defined as YANG instance data files [RFC9195] using the schema below to define the package data. Package instance data files MUST use the ".ypkg" file extension and the "application/ypkg" media type as defined in Section 12.3. The following rules apply to the format of the YANG package instance files: 1. The file MUST be encoded in JSON. 2. The name of the file MUST follow the format "@.ypkg", and the package-name and version MUST match the values specified in the package container's 'name' and 'version' leafs. Wilton, et al. Expires 6 January 2027 [Page 21] Internet-Draft YANG Packages July 2026 3. The 'format' version leaf for in the instance-data-set for .ypkg files MUST NOT be set if it uses the default value of "2022-01-20" but MUST be set if a newer revision is used. 4. The 'include-defaults' leaf in the instance-data-set for .ypkg files MUST NOT be set, but defaults to the 'trim' mode. I.e., default values if the YANG package definition MUST NOT be included in the instance-data-set content-data. 5. The instance-data file can specify a schema: * The default schema for .ypkg files is "ietf-inst-data-pkg- schema.ypkg", defined in Section 9. When used, it SHOULD NOT be specified in the instance-data file. * If a different, e.g., newer or augmented, schema is used then it is RECOMMENDED to specify the YANG instance data file schema using a package definition. E.g., see Section 9 and Section 5.6. 6. The 'name', 'description', 'timestamp', 'organization', and 'contact' fields are defined both in the instance-data-set meta- data and the YANG package meta-data. To avoid redundant information, package definitions MUST only define these fields as part of the package definition. They MUST be left unset as part of the instance-data-set meta-data. 7. If the package definition applies only to a specific datastore then the 'datastore' leaf in the instance-data-set meta-data MUST be set. If the package definition applies to multiple datastores, then the 'datastore' leaf MUST NOT be set. 8. The 'revision' list in the instance data file MUST NOT be used, since versioning is handled by the package definition. 9. The instance data file for each version of a YANG package SHOULD be made available at one or more locations accessible via URLs. If one of the listed locations defines the canonical location for the package definition then it MUST be listed as the first entry in the user-ordered list, so that it remains first when locations are merged during package resolution. Note, the stricter rules for YANG packages in instance data files are intended to encourage consistency and provide a canonical base file representation of the package definition. The "ietf-yang-package-instance" YANG module has the following structure: Wilton, et al. Expires 6 January 2027 [Page 22] Internet-Draft YANG Packages July 2026 module: ietf-yang-package-instance structure package: // Uses the yang-package-instance grouping defined in // ietf-yang-package-types.yang +-- name pkg-name +-- version pkg-version ... remainder of yang-package-instance grouping ... 5.6. YANG packages as schema for YANG instance data document YANG package definitions can be used to define the content schema for YANG instance data files, extending the content schema definition in Section 3.2 of [RFC9195]. When using a package-based content schema, the package name and version MUST be specified, and one or more location URLs for retrieving the package definition MAY also be provided. The resolved package schema provides the exact specification for the content schema, taking into consideration all implemented modules, import-only modules, augmentations, enabled features and any deviations. The "ietf-yang-inst-data-pkg" YANG module has the following structure: module: ietf-yang-inst-data-pkg augment-structure /yid:instance-data-set/... +--:(pkg-schema) +-- pkg-schema +-- name pkg-name +-- version pkg-version +-- location* inet:uri The following example shows how the example in Section 2.2.3 of [RFC9195] could alternatively use example-diagnostics- schema@1.0.0.ypkg to define the content schema for NETCONF monitoring state data. Example of YANG instance data file using a schema defined by a YANG package. Wilton, et al. Expires 6 January 2027 [Page 23] Internet-Draft YANG Packages July 2026 ========== NOTE: '\' line wrapping per RFC 8792 =========== { "ietf-yang-instance-data:instance-data-set": { "name": "example-router-netconf-diagnostics", "content-schema": { "pkg-schema": { "name": "example-diagnostics-schema", "version": "1.0.0", "location": "https://example.org/\ example-diagnostics-schema@1.0.0.ypkg", } }, "timestamp": "2018-01-25T17:00:38Z", "description": ["NETCONF statistics, \ The data may change at any time."], "content-data": { "ietf-netconf-monitoring:netconf-state": { "statistics": { "netconf-start-time ": "2018-12-05T17:45:00Z", "in-bad-hellos ": "32", "in-sessions ": "397", "dropped-sessions ": "87", "in-rpcs ": "8711", "in-bad-rpcs ": "408", "out-rpc-errors ": "408", "out-notifications": "39007" } } } } } Example package definition used as the content schema for the NETCONF monitoring instance data above. file "example-diagnostics-schema@1.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-diagnostics-schema", "version": "1.0.0", "timestamp": "2018-01-25T17:00:38Z", "description": "Example schema package for NETCONF \ Wilton, et al. Expires 6 January 2027 [Page 24] Internet-Draft YANG Packages July 2026 monitoring instance data.", "reference": "RFC 6022", "includes": { "module": [ { "name": "ietf-netconf-monitoring", "version": "2010-10-04", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-netconf-monitoring@2010-10-04.yang" ] } ], "import-only-module": [ { "name": "ietf-yang-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-types@2025-12-22.yang" ] }, { "name": "ietf-inet-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-inet-types@2025-12-22.yang" ] } ] } } } } } 6. Package Evolution and Versioning 6.1. Package versioning As defined in Section 3.1, YANG packages are versioned using [I-D.ietf-netmod-yang-semver]. This section describes how those rules apply to YANG package definitions. Wilton, et al. Expires 6 January 2027 [Page 25] Internet-Draft YANG Packages July 2026 6.1.1. Updating a package with a new version Package compatibility is fundamentally defined by how the package schema between two package versions has changed. When a package definition is updated, the version associated with the package MUST be updated appropriately, taking into consideration the scope of the changes as defined by the rules below. See section 4.5 of [I-D.ietf-netmod-yang-semver] for guidance on choosing the next version number based on the type of change being made. It is important to note that a non-backwards-compatible (NBC) change to a package definition (generally requiring a major version number increment) may not always result in an NBC change to the resolved package schema. For example, if a package replaces a module version 1.0.0 with version 3.0.0, but the content of version 3.0.0 has been reverted to be functionally identical to version 1.0.0 (effectively backing out previous changes between the two), the schema difference between the package versions may be functionally compatible. Nevertheless, such changes must still follow the versioning rules defined above based on the package definition changes, not the effective change to the resolved package schema. 6.1.1.1. Non-Backwards-compatible changes Non-backwards-compatible changes to a package are those that may cause the resolved package schema to change in a way that can negatively impact clients. E.g., the removal or change of a data node that was present in the previous package version, which may be used by client applications. The following changes classify as non-backwards-compatible changes to a package definition: * Changing an 'includes/package' list entry to select a package version that is non-backwards-compatible to the prior package version, or removing a previously included package. * Changing an 'includes/module' or 'includes/import-only-module' list entry to select a module version that is non-backwards- compatible to the prior module version, or removing a previously implemented module. * Adding an entry to the 'excludes/module' list or the 'excludes/ import-only-module' list, which in either case causes a module to be removed from an included package and could affect the conformance reporting of whether the included package is deemed as being implemented. Wilton, et al. Expires 6 January 2027 [Page 26] Internet-Draft YANG Packages July 2026 * Removing a feature from the 'includes/feature' list unless the feature was not enabled by any included packages. * Adding a feature to the 'excludes/feature' list unless the feature was not enabled by any included package. * Adding, changing, or removing a module containing one or more deviations, that when applied to the target module would create a change that is considered a non-backwards-compatible change to the affected data node in the schema associated with the prior package version. * Removing a package from a mount point, or changing a mounted package to a version that is non-backwards-compatible to the prior package version. 6.1.1.2. Backwards-compatible changes Backwards-compatible changes to a package are those that may cause the resolved package schema to change in a way that should not impact clients. E.g., the addition of a new data node that was not present in the previous package version. The following changes classify as backwards-compatible changes to a package definition: * Changing an 'includes/package' list entry to select a package version that is backwards-compatible to the prior package version, or including a new package that does not conflict with any existing included package or module. * Changing an 'includes/module' or 'includes/import-only-module' list entry to select a module version that is backwards-compatible to the prior module version, or including a new module to the package definition. * Removing an entry from the 'excludes/module' list or the 'excludes/import-only-module' list. * Adding a feature to the 'includes/feature' leaf-list. * Removing a feature from the 'excludes/feature' leaf-list. * Adding, changing, or removing a module containing one or more deviations, that when applied to the target module would create a change that is considered a backwards-compatible change to the affected data node in the schema associated with the prior package version. Wilton, et al. Expires 6 January 2027 [Page 27] Internet-Draft YANG Packages July 2026 6.1.1.3. Editorial changes Editorial changes to a package are those that do not change the resolved package schema. The following changes classify as editorial changes to a package definition: * Changing an 'includes/package' list entry to select a package version that is classified as an editorial change relative to the prior package version. * Changing an 'includes/module' or 'includes/import-only-module' list entry to select a module version that is classified as an editorial change relative to the prior module version. * Adding an 'includes/package', 'includes/module', 'includes/import- only-module', or 'mount/package' list entry if the referenced package or module version is already present from an included package. * Updating location information in an 'includes/package', 'includes/ module', 'includes/import-only-module', or 'mount/package' list entry without changing the referenced package or module version. * Any change to any meta-data associated with a package definition. 6.1.2. Guidelines for Package Versions During Package Development During development of a new package, or while updating a previously released package, special care should be taken with the selection of the version associated with the package. General YANG Semver versioning guidance from Section 6 of [I-D.ietf-netmod-yang-semver] may be helpful, additional IETF specific guidance for managing IETF package definitions may be provided in a future RFC, pending the output of [I-D.mahesh-opsawg-veloce-yang]. 7. Package Conformance Better and easier conformance is a major design goal for YANG packages. YANG package conformance is similar to how YANG [RFC7950] requires that servers either implement a module faithfully, or otherwise use deviations to indicate areas of non-conformance. Ultimately, each version of a YANG package resolves, as per (Section 4), to a YANG schema that is defined as a set of implemented modules and import-only modules, deviations, features, and mounted Wilton, et al. Expires 6 January 2027 [Page 28] Internet-Draft YANG Packages July 2026 schema. For YANG package conformance, it is necessary to determine whether an implementation faithfully conforms to the full YANG schema defined by a resolved YANG package. The YANG packaging solution is designed to allow for conformance to be checked at a package level, potentially using cached offline package definitions, rather than requiring a client to download all modules, supported features, and deviations from the server to ensure that the datastore schema used by the server is compatible with the client. In the case where a device does not completely conform to a standard or industry defined YANG package definition, then there are a few suggestions on how this can be handled: * Automatic module version resolution rules can be used to select the latest module version between packages. * Server implementation packages can be defined that include and refine standard/industry packages to accurately report the device's schema and any variations from the standard. 7.1. Resolving conflicting module versions in included packages Sometimes a package definition may include multiple packages that implement different versions of a module. As per the package definition rules in Section 3.1, a package can only implement a single version of a module, and hence in cases of conflicting versions in included packages/modules it is necessary to resolve which version of the module is used. The default behavior, defined in Section 4.1 is to use automatic resolution, which is generally the best choice. Manual resolution could be used to select a different module version instead, or even remove the module from the package entirely. However, care must be taken if an older module version is chosen, or a new non-backwards-compatible newer version is chosen, because, in both cases, this may affect conformance in one of the included packages. 7.2. Handling multiple included package versions Unlike modules in a package definition, where there can only be a single version of a module in a resolved package schema, this does not apply to included packages. As per the package resolution rules in Section 4, when multiple included packages define different versions of the same package, then both versions are retained in the resolved package schema. Wilton, et al. Expires 6 January 2027 [Page 29] Internet-Draft YANG Packages July 2026 Instead, package and schema comparison tooling can be used to determine what level of package conformance has been achieved for each of the recursively included packages. 7.3. Exclusions and Deviations Whenever possible, servers should aim to implement standards defined packages or industry defined packages accurately since this maximizes interoperability for clients. However, if a server does not faithfully implement a YANG package then it can define a new server specific package to accurately report what it does implement. The RECOMMENDED approach to achieve this is to define and advertise a separate "server implementation" package which incorporates the package to be conformed to via including it in "/includes/package", and then excludes modules or selects different versions, adds deviation modules, and excludes enabled features to indicate the actual conformance of the server implementation. An example of this approach is provided in Appendix A.2.1. If an implementation doesn't support any functionality in a module then it should exclude the module rather than using deviations to exclude all data nodes added by the module to the resolved package schema. This gives a clearer indication to users of the package definition as to the intent. However, be aware when combining two included packages, that a module removed by one package could still be re-added by another included package. If deviations are used this won't happen unless the module defining the deviations is explicitly removed. If an alternative version of a module is used then it is RECOMMENDED to use a newer module version, if possible, rather than an older version. Selecting a backwards-compatible version is also helpful because it maximizes the chance that clients will be able to easily interoperate with the server. 7.4. Use of features in YANG modules and YANG packages The YANG language, [RFC7950] section 5.6.2, supports feature statements as the mechanism to make parts of a schema optional. Published standard YANG modules make use of appropriate feature statements to provide flexibility in how YANG modules may be used by implementations and used by YANG modules published by other organizations. Wilton, et al. Expires 6 January 2027 [Page 30] Internet-Draft YANG Packages July 2026 YANG packages include the 'includes/feature' list, which allows the package to define a set of features that MUST be enabled by any conformant implementation of the package as a mechanism to simplify and manage the schema represented by a YANG package. 7.5. Use of YANG semantic versioning for YANG packages Using the YANG semantic versioning scheme for package version numbers and module version labels can help with conformance. In the general case, clients should be able to determine the nature of changes between two package versions by comparing the version number. This usually means that a client does not have to be restricted to working only with servers that advertise exactly the same version of a package in YANG library. Instead, reasonable clients should be able to interoperate with any server that supports a package version that is backwards compatible with the version that the client is designed for, assuming that the client is designed to ignore operational values for unknown data nodes. For example, a client coded to support 'example-foo' package at version 1.0.0 should interoperate with a server implementing 'example-foo' package at version 1.3.5, because the YANG semantic versioning rules require that package version 1.3.5 is backwards compatible with version 1.0.0. This also has a relevance on servers that are capable of supporting version selection because they need not support every version of a YANG package to ensure good client compatibility. Choosing suitable minor versions within each major version number should generally be sufficient, particularly if they can avoid non-backwards-compatible patch level changes. 7.6. Restrictions on the use of deviations in YANG packages [RFC7950] section 5.6.3 defines deviations as the mechanism to allow servers to indicate where they do not conform to a published YANG module that is being implemented. Organizations may wish to reuse YANG modules and YANG packages published by other organizations for new functionality. Sometimes, they may desire to modify the published YANG modules. However, they MUST NOT use deviations in an attempt to achieve this because such deviations cause two problems: They prevent implementations from reporting their own deviations for the same nodes. Wilton, et al. Expires 6 January 2027 [Page 31] Internet-Draft YANG Packages July 2026 They fracture the ecosystem by preventing implementations from conforming to the standards specified by both organizations. This hurts the interoperability in the YANG community, promotes development of disconnected functional silos, and hurts creativity in the market. 7.7. The relationship between packages and datastores As defined by NMDA [RFC8342], each datastore has an associated datastore schema. These datastore schemas can be advertised by servers using YANG Library [RFC8525], augmented with the associated YANG package information, as per Section 5.4.3. Sections 5.1 and 5.3 of NMDA defines further constraints on the schema associated with datastores. These constraints can be summarized thus: * The schema for all conventional datastores is the same. * The schema for non-conventional configuration datastores (e.g., dynamic datastores) may completely differ (i.e. no overlap at all) from the schema associated with the conventional configuration datastores, or may partially or fully overlap with the schema of the conventional configuration datastores. A dynamic datastore, for example, may support different modules than conventional datastores, or may support a subset or superset of modules, features, or data nodes supported in the conventional configuration datastores. Where a data node exists in multiple datastore schemas it has the same type, properties and semantics. * The schema for the operational datastore is intended to be a superset of all the configuration datastores (i.e. includes all the schema nodes from the conventional configuration datastores), but data nodes can be omitted if they cannot be accurately reported. The operational datastore schema can include additional modules containing only config false data nodes, but there is no harm in including those modules in the configuration datastore schema as well. Given that YANG packages represent a schema, it follows that each datastore schema can be represented using packages. In addition, the schemas for most datastores on a server are often closely related. Given that there are many ways that a datastore schema could be represented using packages, the following guidance provides a consistent approach to help clients understand the relationship between the different datastore schemas supported by a device (e.g., which parts of the schema are common and which parts have differences): Wilton, et al. Expires 6 January 2027 [Page 32] Internet-Draft YANG Packages July 2026 * Any datastores (e.g., conventional configuration datastores) that have exactly the same datastore schema MUST use the same package definitions. This is to avoid, for example, the creation of a 'running-cfg' package and a separate 'intended-cfg' package that have identical schema. * Common package definitions SHOULD be used for those parts of the datastore schema that are common between datastores, when those datastores do not share exactly the same datastore schema. E.g., if a substantial part of the schema is common between the conventional, dynamic, and operational datastores then a single common package can be used to describe the common parts, along with other packages to describe the unique parts of each datastore schema. * YANG modules that do not contain any configuration data nodes MAY be included in the package for configuration datastores if that helps unify the package definitions. * The packages for the operational datastore schema SHOULD include all packages for all configuration datastores, along with any required modules defining deviations to mark unsupported data nodes. The deviations MAY be defined directly in the packages defining the operational datastore schema, or in separate packages (which may be packages attached to the datastore, or may be packages included by other packages). * The schema for a datastore MAY be represented using a single package or as the union of a set of compatible packages, i.e., equivalently to a set of non-conflicting packages being included together in an overarching package definition that relies on the automatic resolution of module versions. * The resolved package schema representing a datastore MUST be referentially complete. 7.8. Using package comparison tools Clients fetch the package information from the server (if required), and then can use tools to generate the resolved package schema. The resolved package schema may list multiple versions of the same package (if included with different versions), and it may list package versions that are not completely implemented by the device. By using package schema comparison, as described below, tooling can report on the level of conformance for each package and included package version advertised by the device. Wilton, et al. Expires 6 January 2027 [Page 33] Internet-Draft YANG Packages July 2026 YANG package schema comparison tools (and also documentation) can be used to determine how closely a device implements particular YANG package definitions advertised by the device. The tooling, by resolving the package definition, then comparing the set of module versions, features, deviations and mounts, can determine if the package schema is implemented exactly, or if the package schema is backwards-compatible, or non-backwards-compatible. Tooling can determine if modules have been removed, mounts have been changed, or deviations have been applied. 8. YANG Modules The YANG module definitions for the modules described in the previous sections follow. Some of these modules use the YANG Data Structure Extensions defined in [RFC8791]. 8.1. ietf-yang-package-types The "ietf-yang-package-types" module imports "ietf-yang-revisions" [I-D.ietf-netmod-yang-module-versioning], "ietf-yang-semver" [I-D.ietf-netmod-yang-semver], "ietf-yang-types" [RFC9911], and "ietf-inet-types" [RFC9911]. file "ietf-yang-package-types#0.9.0.yang" module ietf-yang-package-types { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-package-types"; prefix "pkg-types"; import ietf-yang-revisions { prefix rev; reference "XXXX: Updated YANG Module Revision Handling"; } import ietf-yang-semver { prefix ys; reference "XXXX: YANG Semantic Versioning"; } import ietf-yang-types { prefix yang; rev:recommended-min-date 2025-12-22; reference "RFC 9911: Common YANG Data Types."; } import ietf-inet-types { prefix inet; rev:recommended-min-date 2025-12-22; Wilton, et al. Expires 6 January 2027 [Page 34] Internet-Draft YANG Packages July 2026 reference "RFC 9911: Common YANG Data Types."; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Rob Wilton "; description "This module provides type and grouping definitions for YANG packages. 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). 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."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2026-06-12 { ys:version 0.9.0; description "Initial revision"; reference "RFC XXXX: YANG Packages"; } Wilton, et al. Expires 6 January 2027 [Page 35] Internet-Draft YANG Packages July 2026 /* * Typedefs */ typedef pkg-name { type yang:yang-identifier; description "Package names are typed as YANG identifiers."; } typedef pkg-version { type ys:version; description "Packages are versioned using YANG Semver version labels."; } typedef module-name { type yang:yang-identifier; description "Module names are typed as YANG identifiers."; } typedef version-or-rev-date { type union { type rev:revision-date; type ys:version; } description "Identifies a module by YANG semantic version or revision date"; } typedef scoped-feature { type string { pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*:[a-zA-Z_][a-zA-Z0-9\-_.]*'; } description "Represents a feature name scoped to a particular module, identified as the ':', where both and are YANG identifier strings, as defined by Section 12 or RFC 6020."; reference "RFC XXXX, YANG Packages."; } typedef mount-ypath { type string; Wilton, et al. Expires 6 January 2027 [Page 36] Internet-Draft YANG Packages July 2026 description "A path that identifies a set of data nodes in the schema tree. This leaf is encoded as a JSON style encoded instance-identifier (regardless of whether the format used to encode the YANG instance data), as specified in RFC 7951, section 6.11, except that keys are optional. For optional keys, the name and value of the key is excluded from the key list. TODO - Check if this definition is sufficient."; } /* * Groupings */ grouping yang-pkg-identification-leafs { description "Parameters for identifying a specific version of a YANG package"; leaf name { type pkg-name; mandatory true; description "The YANG package name."; } leaf version { type pkg-version; mandatory true; description "Uniquely identifies a particular version of a YANG package. Follows the definition for YANG Semantic Version labels defined in draft-ietf-netmod-yang-semver, section 4.2 XXXX, RFC Editor, please update reference and section to the published YANG Semver RFC."; } } grouping yang-pkg-exclusions { description "Parameters for excluding modules and packages from a YANG package definition"; Wilton, et al. Expires 6 January 2027 [Page 37] Internet-Draft YANG Packages July 2026 container excludes { description "Contains parameters for excluding modules and packages from a YANG package definition"; leaf-list module { type module-name; description "Lists implemented modules, of any version, that may have have been brought in by included packages, but are explicitly excluded from this package definition. Excluding a module can affect the compliance and correctness of any included packages that expect that module to be implemented. Excluding a module also implicitly excludes any submodules and enabled features defined in the excluded module. It is an error to list a module in both this list and the 'includes/module' list."; } list import-only-module { key "name"; description "Lists import-only modules that may have have been brought in by included packages, but are explicitly excluded from this package definition. It is an error to list the same module version in both this list and the 'includes/import-only-module' list. If no versions are listed for an entry in this list, then that entry excludes all versions of the import-only module and it is an error to list the same module name in the 'includes/import-only-module' list."; leaf name { type module-name; mandatory true; description "The name of the import-only module to exclude some versions of."; } leaf-list version { type version-or-rev-date; description Wilton, et al. Expires 6 January 2027 [Page 38] Internet-Draft YANG Packages July 2026 "Lists specific versions of the import-only module being excluded. If no versions are listed, all versions of the import-only module are excluded. If required, the YANG Semantic Version SHOULD be used to identify the module version, otherwise the YANG module revision date is used."; } } leaf-list feature { type scoped-feature; description "Lists features from the 'includes/feature' list exported by an included package that are reclassified as being OPTIONAL to support by any server implementing the package, overriding the behavior specified by the included package. Features MUST NOT be specified both in this list and also the 'includes/feature' list."; } } } grouping yang-pkg-location { description "Parameters for locating a YANG package instance"; leaf-list location { type inet:uri; ordered-by user; description "Contains a URL that represents where an instance data file (RFC 9195) for this YANG package can be found. This leaf will only be present if there is a URL available for retrieval of the schema for this entry. If multiple locations are provided, then the first location in the leaf-list SHOULD be the canonical location that uniquely identifies this package."; } } grouping submodule-identification-leafs { description "Defines the data nodes for representing a submodule reference in a YANG package definition."; Wilton, et al. Expires 6 January 2027 [Page 39] Internet-Draft YANG Packages July 2026 list submodule { key "name"; description "Each entry represents one submodule within the parent module."; leaf name { type module-name; mandatory true; description "The YANG submodule name."; } leaf version { type version-or-rev-date; mandatory true; description "The YANG submodule revision date or YANG Semantic version. If the parent module include statement for this submodule includes a revision date then it MUST match the revision date specified here or it MUST match the revision-date associated with the version specified here."; } leaf-list location { type inet:uri; ordered-by user; description "Contains a URL from where the YANG schema resource for this submodule can be retrieved. If multiple locations are provided, then the first location in the leaf-list SHOULD be the canonical location that uniquely identifies this submodule."; } } } grouping module-and-submodule-identification-leafs { description "Defines the data nodes for representing a module reference with its associated submodules."; leaf name { type module-name; mandatory true; Wilton, et al. Expires 6 January 2027 [Page 40] Internet-Draft YANG Packages July 2026 description "The YANG module name."; } leaf version { type version-or-rev-date; mandatory true; description "Identifies the module version. If available, the YANG Semantic Version SHOULD be used, otherwise the YANG module revision date is used."; } leaf-list location { type inet:uri; ordered-by user; description "Contains a URL that represents the YANG schema resource for this module. This leaf will only be present if there is a URL available for retrieval of the schema for this entry. If multiple locations are provided, then the first location in the leaf-list SHOULD be the canonical location that uniquely identifies this module."; } uses submodule-identification-leafs; } grouping yang-pkg-instance { description "Specifies the data node for a full YANG package instance represented either on a server or as a YANG instance data document."; uses yang-pkg-identification-leafs; leaf version-description { type string; description "An optional description of the package version. E.g., perhaps tying it to a software release or a description of what key changes have occurred compared to the previous version."; } leaf timestamp { Wilton, et al. Expires 6 January 2027 [Page 41] Internet-Draft YANG Packages July 2026 type yang:date-and-time; description "An optional timestamp for when this package was created. This does not need to be unique across all versions of a package."; } leaf organization { type string; description "Organization responsible for this package"; } leaf contact { type string; description "Contact information for the person or organization to whom queries concerning this package should be sent."; } leaf description { type string; description "Provides a description of the package"; } leaf reference { type string; description "Allows for a reference for the package"; } leaf complete { type boolean; default true; description "Indicates whether the schema defined by this package is referentially complete. I.e. all module imports can be resolved to a module explicitly defined in this package or one of the included packages."; } container includes { description "Lists package and modules that are included in the package definition."; list package { key "name version"; ordered-by user; description Wilton, et al. Expires 6 January 2027 [Page 42] Internet-Draft YANG Packages July 2026 "An entry in this list represents a package that is included as part of the package definition. A package MAY directly include multiple versions of the same package, but normally only a single package version is expected. Multiple package versions can be listed, for example, to update location information for package versions included through other packages."; reference "RFC XXXX: YANG Packages, Section 4."; uses yang-pkg-identification-leafs; uses yang-pkg-location; } list module { key "name"; description "An entry in this list represents a module that MUST be implemented by a server implementing this package, as per RFC 7950 section 5.6.5. An entry in this list overrides any module version 'implemented' by an included package."; reference "RFC 7950: The YANG 1.1 Data Modeling Language."; uses module-and-submodule-identification-leafs; } list import-only-module { key "name version"; description "An entry in this list indicates that the server imports reusable definitions from the specified version of the module, but does not implement any protocol accessible objects from this version. This entry overrides any import-only module definition with the same module name and version from an included package. Multiple entries for the same module name MAY exist. This can occur if multiple modules import the same module, but specify different revision-dates in the import statements."; uses module-and-submodule-identification-leafs; Wilton, et al. Expires 6 January 2027 [Page 43] Internet-Draft YANG Packages July 2026 } leaf-list feature { type scoped-feature; description "Lists features, defined in any modules included in the package, that MUST be supported by any server implementing the package. Enabled features specified by any directly included packages MUST also be supported by server implementations, unless excluded by an entry in the 'excludes/feature' list, and do not need to be repeated in this list. All other features defined in modules included in the package are OPTIONAL to implement."; } } uses yang-pkg-exclusions; container depends-on { when "../complete = 'false'"; description "Lists packages that are depended on by this 'incomplete' package definition. All packages listed in this list MUST be fetched and resolved by the server or produce a complete package definition. This additional schema information SHOULD be provided by a server to help a client resolve a complete schema in a machine readable way. The server MAY provide the additional schema information in another way, e.g., via user documentation, or if the dependencies are more complex."; reference "RFC XXXX: YANG Packages, Section 4."; list package { key "name version"; description "An entry in this list represents a package that is depended on by this 'incomplete' package definition."; uses yang-pkg-identification-leafs; Wilton, et al. Expires 6 January 2027 [Page 44] Internet-Draft YANG Packages July 2026 uses yang-pkg-location; } } list mount { key "mount-path"; description "An entry in this list represents additions to the schema found at the specified mount point, or, if 'inherit-packages' is 'false', replacement of the inherited schema found at the specified mount point."; leaf "mount-path" { type mount-ypath; mandatory true; description "This path identifies a mount point in the schema. This leaf is encoded as a JSON style encoded instance-identifier (regardless of whether the format used to encode the YANG instance data), as specified in RFC 7951, section 6.11, except that keys are optional. For optional keys, the name and value of the key is excluded from the key list. Mount paths MUST only be used for schema mount points defined in the package schema. For example, if an example module 'ex-module' defines a mount point under list entry'/modules/module/' then a mount path of - '/modules/module[name=foo]' would indicate the mounted package schema for only the 'foo' entry in the module list. Each entry in the list could have a different mounted schema specified. - '/modules/module[]' would indicate that the same mounted package schema is available for all list entries in the module list."; } leaf inherit-packages { type boolean; default true; description "Indicates whether the packages, additional features, and Wilton, et al. Expires 6 January 2027 [Page 45] Internet-Draft YANG Packages July 2026 parent-references available at the mount point for this package definition automatically include all packages, additional features, and parent-references mounted at the same mount path in any 'includes/package' entries. If set to true (the default), the schema is defined as the union of the resolved package schema at the mount point by any packages in the 'includes/package' list combined with the resolved package schema of all packages listed in the 'package' list, plus any additional features and parent-references defined for the same mount point. If set to false, then the mounted schema starts from a blank slate and only packages, additional features, and parent-references listed in this 'mount' entry are included. This allows the definitions in the mounted packages to be modified (e.g., remove or change module versions). To help conformance, the packages listed here SHOULD include all the packages that would have been automatically included. "; } list package { key "name version"; ordered-by user; description "The packages that will be mounted at the specified mount path. A mount point MAY directly list multiple versions of the same package, but normally only a single package version is expected. Multiple package versions can be listed, for example, to update location information for package versions inherited from included packages. If 'inherit-packages' is true, or absent, then these packages are mounted in addition to the mounted packages from the 'includes/package' list. If 'inherit-packages' is false, then these packages, together with any additional features and parent-references in the same 'mount' entry, define the mounted package schema at this mount point. Also see the 'inherit-packages' leaf."; reference Wilton, et al. Expires 6 January 2027 [Page 46] Internet-Draft YANG Packages July 2026 "RFC XXXX: YANG Packages, Section 4."; uses yang-pkg-identification-leafs; uses yang-pkg-location; } leaf-list additional-feature { type scoped-feature; description "The name of YANG features enabled at the mount point in addition to the enabled features from the resolved mounted package definitions. This list identifies additional features rather than the complete set of supported features. The features listed here MUST be defined in modules included in the resolved mounted package schema. Features are identified using :. "; } leaf-list parent-reference { type mount-ypath; description "Represents paths in the parent schema that are accessible from the mounted schema for the evaluation of XPath expressions. See Mount Point path and parent-reference in Schema Mount (RFC 8528) for a more detailed description. Unlike the YANG module defined in RFC 8528, this leaf is encoded as a JSON style encoded instance-identifier (regardless of whether the format used to encode the YANG instance data), as specified in RFC 7951, section 6.11, except that keys are optional. For optional keys, the name and value of the key is excluded from the key list."; } } } } Wilton, et al. Expires 6 January 2027 [Page 47] Internet-Draft YANG Packages July 2026 8.2. ietf-yang-package-instance The "ietf-yang-package-instance" module imports "ietf-yang-semver" [I-D.ietf-netmod-yang-semver], "ietf-yang-package-types" defined in this document, and "ietf-yang-structure-ext" [RFC8791]. file "ietf-yang-package-instance#0.9.0.yang" module ietf-yang-package-instance { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-package-instance"; prefix pkg-inst; import ietf-yang-semver { prefix ys; reference "XXXX: YANG Semantic Versioning"; } import ietf-yang-package-types { prefix pkg-types; ys:recommended-min-version 0.8.0; reference "RFC XXX: this RFC."; } import ietf-yang-structure-ext { prefix sx; reference "RFC 8791: YANG Data Structure Extensions."; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Rob Wilton "; description "This module provides a definition of a YANG package, which is used as the content schema for a YANG instance data document specifying a YANG package. 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 Wilton, et al. Expires 6 January 2027 [Page 48] Internet-Draft YANG Packages July 2026 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). 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."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2026-06-12 { ys:version 0.9.0; description "Initial revision"; reference "RFC XXXX: YANG Packages"; } /* * Top-level structure */ sx:structure package { description "Defines the YANG package structure for use in a YANG instance data document."; uses pkg-types:yang-pkg-instance; } } 8.3. ietf-yang-package The "ietf-yang-package" module imports "ietf-yang-semver" [I-D.ietf-netmod-yang-semver] and "ietf-yang-package-types" defined in this document. Wilton, et al. Expires 6 January 2027 [Page 49] Internet-Draft YANG Packages July 2026 file "ietf-yang-packages#0.9.0.yang" module ietf-yang-packages { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-packages"; prefix pkgs; import ietf-yang-semver { prefix ys; reference "XXXX: YANG Semantic Versioning"; } import ietf-yang-package-types { prefix pkg-types; ys:recommended-min-version 0.8.0; reference "RFC XXX: this RFC."; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Rob Wilton "; description "This module defines YANG packages on a server implementation. 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). 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."; Wilton, et al. Expires 6 January 2027 [Page 50] Internet-Draft YANG Packages July 2026 // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2026-06-12 { ys:version 0.9.0; description "Initial revision"; reference "RFC XXXX: YANG Packages"; } /* * Groupings */ grouping yang-pkg-ref { description "Defines the leaves used to reference a single entry in the top-level '/pkgs:packages/pkgs:package' list."; leaf name { type leafref { path '/pkgs:packages/pkgs:package/pkgs:name'; } description "The name of the referenced package in the top-level '/pkgs:packages/pkgs:package' list."; } leaf version { type leafref { path '/pkgs:packages' + '/pkgs:package[pkgs:name = current()/../name]' + '/pkgs:version'; } description "The version of the referenced package in the top-level '/pkgs:packages/pkgs:package' list."; } } /* * Top level data nodes. Wilton, et al. Expires 6 January 2027 [Page 51] Internet-Draft YANG Packages July 2026 */ container packages { config false; description "All YANG package definitions"; list package { key "name version"; description "YANG package instance"; uses pkg-types:yang-pkg-instance; } } } 8.4. ietf-yl-packages The "ietf-yl-packages" module imports "ietf-yang-revisions" [I-D.ietf-netmod-yang-module-versioning], "ietf-yang-semver" [I-D.ietf-netmod-yang-semver], "ietf-yang-package-types" and "ietf- yang-packages" defined in this document, and "ietf-yang-library" [RFC8525]. file "ietf-yl-packages#0.9.0.yang" module ietf-yl-packages { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yl-packages"; prefix yl-pkgs; import ietf-yang-revisions { prefix rev; reference "XXXX: Updated YANG Module Revision Handling"; } import ietf-yang-semver { prefix ys; reference "XXXX: YANG Semantic Versioning"; } import ietf-yang-package-types { prefix pkg-types; ys:recommended-min-version 0.8.0; reference "RFC XXX: YANG Packages."; } Wilton, et al. Expires 6 January 2027 [Page 52] Internet-Draft YANG Packages July 2026 import ietf-yang-packages { prefix pkgs; ys:recommended-min-version 0.8.0; reference "RFC XXX: YANG Packages."; } import ietf-yang-library { prefix yanglib; rev:recommended-min-date 2019-01-04; reference "RFC 8525: YANG Library"; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Rob Wilton "; description "This module provides defined augmentations to YANG library to allow a server to report YANG package information. 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). 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."; // RFC Ed.: update the date below with the date of RFC publication Wilton, et al. Expires 6 January 2027 [Page 53] Internet-Draft YANG Packages July 2026 // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2026-06-12 { ys:version 0.9.0; description "Initial revision"; reference "RFC XXXX: YANG Packages"; } /* * Augmentations */ augment "/yanglib:yang-library/yanglib:schema" { description "Allow datastore schema to be related to a set of YANG packages. Features enabled by the server in addition to the mandatory features from the package definitions are listed in the 'additional-feature' list. "; list package { key "name version"; ordered-by user; description "Identifies the YANG packages that collectively define the schema for the associated datastore. The referenced packages are resolved as if they were all directly included in a single package definition, as described in RFC XXXX, Section 5.4.3. The resolved datastore schema MUST be referentially complete."; reference "RFC XXXX: YANG Packages, Section 5.4.3."; uses pkgs:yang-pkg-ref; uses pkg-types:yang-pkg-location; } leaf-list additional-feature { Wilton, et al. Expires 6 January 2027 [Page 54] Internet-Draft YANG Packages July 2026 type pkg-types:scoped-feature; description "The name of YANG features enabled by the server in addition to the enabled features from the resolved package definitions associated with this datastore schema. Although this list identifies additional features rather than the complete set of supported features, enabled features from the resolved packages MAY be included. The features listed here MUST be defined in modules included in the datastore schema. Features are identified using :. This list, combined with the enabled features from the resolved package schemas, MUST be equivalent to the list of supported features advertised in YANG library."; } } } 8.5. ietf-yang-inst-data-pkg The "ietf-yang-inst-data-pkg" module imports "ietf-yang-revisions" [I-D.ietf-netmod-yang-module-versioning], "ietf-yang-semver" [I-D.ietf-netmod-yang-semver], "ietf-yang-package-types" defined in this document, "ietf-inet-types" [RFC9911], "ietf-yang-structure-ext" [RFC8791], and "ietf-yang-instance-data" [RFC9195]. file "ietf-yang-inst-data-pkg#0.9.0.yang" module ietf-yang-inst-data-pkg { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-inst-data-pkg"; prefix yid-pkg; import ietf-yang-revisions { prefix rev; reference "XXXX: Updated YANG Module Revision Handling"; } import ietf-yang-semver { prefix ys; reference "XXXX: YANG Semantic Versioning"; } import ietf-yang-package-types { Wilton, et al. Expires 6 January 2027 [Page 55] Internet-Draft YANG Packages July 2026 prefix pkg-types; ys:recommended-min-version 0.8.0; reference "RFC XXX: this RFC."; } import ietf-inet-types { prefix inet; rev:recommended-min-date 2025-12-22; reference "RFC 9911: Common YANG Data Types."; } import ietf-yang-structure-ext { prefix sx; reference "RFC 8791: YANG Data Structure Extensions."; } import ietf-yang-instance-data { prefix yid; reference "RFC 9195: YANG Instance Data File Format."; } organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Rob Wilton "; description "The module augments ietf-yang-instance-data to allow package definitions to be used to define content schema in YANG instance data documents. 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). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices. Wilton, et al. Expires 6 January 2027 [Page 56] Internet-Draft YANG Packages July 2026 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."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2026-06-12 { ys:version 0.9.0; description "Initial revision"; reference "RFC XXXX: YANG Packages"; } /* * Augmentations */ sx:augment-structure "/yid:instance-data-set/yid:content-schema/" + "yid:content-schema-spec" { description "Add package reference to instance data set schema specification"; case pkg-schema { container pkg-schema { uses pkg-types:yang-pkg-identification-leafs; leaf-list location { type inet:uri; ordered-by user; description "Contains a URL that represents where an instance data file for this YANG package can be found. This leaf will only be present if there is a URL available for retrieval of the schema for this entry. If multiple locations are provided, then the first location in the leaf-list SHOULD be the canonical location that uniquely identifies this package."; } } } Wilton, et al. Expires 6 January 2027 [Page 57] Internet-Draft YANG Packages July 2026 } } 9. YANG Package Instance Data Schema This section defines the YANG package schema to use as a schema for YANG instance data files defining YANG packages. Although this definition may appear to be somewhat self-recursive, this can be mitigated by the fact that tools SHOULD recognize files of type ".ypkg" as being YANG package instance data files, without needing to check the package schema. RFC Editor note: Please check module versions, and update the package version and module versions to 1.0.0 on publication of the RFC. I.e., the expectation is that any non-example versions starting 0.x.y should become 1.0.0 on publication. file "yang-inst-data-schema@0.1.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "yang-inst-data-schema", "version": "0.1.0", "timestamp": "2026-03-20T17:52:47.188253Z", "organization": "IETF", "contact": "IESG", "description": "Package schema to use for defining the \ yang-inst-data-schema schema for YANG packages. TODO - RFC Editor, \ plesae check semver and module versioning module revisions. RFC \ Editor, please update this module version to 1.0.0 on publication \ of the RFC.", "includes": { "module": [ { "name": "ietf-yang-package-instance", "version": "0.8.0", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-package-instance@0.8.0.yang" ] } ], "import-only-module": [ { Wilton, et al. Expires 6 January 2027 [Page 58] Internet-Draft YANG Packages July 2026 "name": "ietf-yang-package-types", "version": "0.8.0", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-package-types@0.8.0.yang" ] }, { "name": "ietf-yang-revisions", "version": "2025-09-16", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-revisions@2025-09-16.yang" ] }, { "name": "ietf-yang-semver", "version": "2025-09-29", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-semver@2025-09-29.yang" ] }, { "name": "ietf-yang-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-types@2025-12-22.yang" ] }, { "name": "ietf-inet-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-inet-types@2025-12-22.yang" ] }, { "name": "ietf-yang-structure-ext", "version": "2020-06-17", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-structure-ext@2020-06-17.yang" ] } ] Wilton, et al. Expires 6 January 2027 [Page 59] Internet-Draft YANG Packages July 2026 } } } } } 10. Security Considerations This document defines YANG modules for defining YANG schema, that are often used to configure and monitor network devices. The document defines three YANG modules that are accessible from devices, and the normal YANG network management security considerations apply, which are further described below, in Section 10.1. YANG packages also offer an alternative mechanism to YANG Library [RFC8525] for reporting YANG schema, and hence the security considerations from that document also apply to the use of YANG packages. As per the YANG library security considerations, the module and version information in YANG packages may help an attacker identify the server capabilities and server implementations with known bugs since the set of YANG modules supported by a server may reveal the kind of device and the manufacturer of the device. Server vulnerabilities may be specific to particular modules, module revisions, module features, or even module deviations. For example, if a particular operation on a particular data node is known to cause a server to crash or significantly degrade device performance, then the YANG packages information will help an attacker identify server implementations with such a defect, in order to launch a denial-of- service attack on the device. The 'ietf-yang-package-instance.yang' YANG file allows YANG packages to be defined in YANG instance data files. In addition, "ietf-yang- inst-data-pkg" allows YANG packages to be used to define the schema for YANG instance data files. In both cases, the security considerations from [RFC9195] apply. Since YANG package instance data files are outside the security controls of the network management protocols, it is important to consider controlling access to these files to restrict access to potentially sensitive information. 10.1. YANG Module Security Considerations This section is modeled after the template described in Section 3.7 of [RFC9907]. Wilton, et al. Expires 6 January 2027 [Page 60] Internet-Draft YANG Packages July 2026 The "ietf-yang-package-types", "ietf-yang-packages" and "ietf-yl- packages" YANG modules define data models that are designed to be accessed via YANG-based management protocols, such as NETCONF [RFC6241] and RESTCONF [RFC8040]. These YANG-based management protocols (1) have to use a secure transport layer (e.g., SSH [RFC6242], TLS [RFC8446], 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. 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: * There are no particularly sensitive readable data nodes. Modules that use the groupings that are defined in this document should identify the corresponding security considerations. For example, reusing some of these groupings will expose privacy-related information (e.g., 'yang-pkg-instance'). 11. Operational Considerations YANG packages provide an alternative mechanism to YANG Library [RFC8525] for describing a server's implemented YANG schema. However, package support is not expected to replace YANG Library on servers. Devices are expected to continue supporting YANG Library for clients that are not package-aware, and package-aware clients may still use YANG Library information when resolving or validating the effective datastore schema. Device vendors and package publishers should take care when making non-backwards-compatible (NBC) package changes, since such changes can be impactful to clients that depend on the prior package schema. Where NBC changes are necessary, it is better to make them clear and transparent through the package version number. The "version- description" leaf can also be used to highlight important NBC changes, such as removed modules, removed enabled features, down- referenced modules or packages, or new deviations that restrict the schema. NBC changes should still be minimized where practical. Wilton, et al. Expires 6 January 2027 [Page 61] Internet-Draft YANG Packages July 2026 Package resolution is generally expected to be performed off-device using tooling rather than by the managed device itself. To support this, package definitions should be made available off-device as ".ypkg" instance data files using stable URIs. Stable locations allow operators, clients, and tooling to retrieve package definitions, resolve package dependencies, compare package versions, and validate schemas without relying on repeated retrieval of schema information from the device. 12. IANA Considerations 12.1. IANA YANG Module and Namespace Registrations This document requests IANA to registers a URI in the "IETF XML Registry" [RFC3688]. Following the format in RFC 3688, the following registrations are requested. URI: urn:ietf:params:xml:ns:yang:ietf-yang-package-types Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-yang-package-instance Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-yang-packages Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-yl-packages Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-yang-inst-data-pkg Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. This document requests that the following YANG modules are added in the "YANG Module Names" registry [RFC6020]: Name: ietf-yang-package-types Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-package-types Prefix: pkg-types Reference: RFC XXXX Name: ietf-yang-package-instance Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-package-instance Prefix: pkg-inst Wilton, et al. Expires 6 January 2027 [Page 62] Internet-Draft YANG Packages July 2026 Reference: RFC XXXX Name: ietf-yang-packages Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-packages Prefix: pkgs Reference: RFC XXXX Name: ietf-yl-packages Namespace: urn:ietf:params:xml:ns:yang:ietf-yl-packages Prefix: yl-pkgs Reference: RFC XXXX Name: ietf-yang-inst-data-pkg Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-inst-data-pkg Prefix: yid-pkg Reference: RFC XXXX 12.2. IETF YANG Package Registry This document requests that IANA create a registry for IETF YANG packages, that lists all versions of all YANG package definitions published by the IETF, and provides a reliable location to store the YANG package definitions. The name of the registry is "YANG Package Names" in the "YANG Parameters" registry group. The registry shall record for each entry: * the name of the YANG package * a brief description of the package purpose * The latest published package version * A list of all published package versions, each hyperlinked to the location where a package instance data file, Section 5.5, for that package definition may be retrieved from. * a reference to the package documentation (e.g., the RFC number) On creation of the registry, the ietf-inst-data-pkg-schema.ypkg, defined in Section 9, should be added. For allocation, the registration policy is Specification Required, as defined in [RFC8126]. All registered YANG package names must comply with the rules for identifiers stated in Section 6.2, and must have a package name prefix. Wilton, et al. Expires 6 January 2027 [Page 63] Internet-Draft YANG Packages July 2026 The package name prefix 'ietf-' is reserved for YANG packages managed and published under the IETF stream [RFC4844], while the package name prefix 'irtf-' is reserved for YANG packages defined by the IRTF stream. Packages published in other RFC streams must use a similar suitable prefix. All package names in the registry must be unique. 12.3. Media Type Registration for application/ypkg This document requests IANA to register the following media type, following the procedures of [RFC6838]: Type name: application Subtype name: ypkg Required parameters: N/A Optional parameters: N/A Encoding considerations: 8bit; YANG package instance data files are encoded in UTF-8. Security considerations: See the Security Considerations section of RFC XXXX. Interoperability considerations: N/A Published specification: RFC XXXX Applications that use this media type: YANG tooling and servers that generate or consume YANG package instance data files. Additional information: Magic number(s): None File extension(s): ypkg Macintosh file type code(s): 'Text' Fragment identifiers: N/A Person & Email address to contact for further information: NETMOD WG (mailto:netmod@ietf.org) Intended usage: COMMON Restrictions on usage: N/A Author: IETF Change controller: IESG 13. Acknowledgements Feedback helping shape this document has kindly been provided by Andy Bierman, James Cumming, Mahesh Jethanandani, Balazs Lengyel, Ladislav Lhotka, and Jan Lindblad. Bo Wu acted as a temporary editor for earlier versions of this work. Wilton, et al. Expires 6 January 2027 [Page 64] Internet-Draft YANG Packages July 2026 LLMs, mainly Codex, have been used to review and hopefully improve this document and have been directed help generate some content, in particular the examples. The final content remains the responsibility of the authors. 14. References 14.1. Normative References [I-D.ietf-netmod-yang-module-versioning] Wilton, R., Rahman, R., Lengyel, B., Clarke, J., and J. Sterne, "Updated YANG Module Revision Handling", Work in Progress, Internet-Draft, draft-ietf-netmod-yang-module- versioning-17, 29 June 2026, . [I-D.ietf-netmod-yang-semver] Clarke, J., Wilton, R., Rahman, R., Lengyel, B., Sterne, J., and B. Claise, "YANG Semantic Versioning", Work in Progress, Internet-Draft, draft-ietf-netmod-yang-semver- 26, 7 May 2026, . [I-D.ietf-netmod-yang-ver-selection] Wilton, R., Rahman, R., Clarke, J., Sterne, J., and B. Wu, "YANG Schema Selection", Work in Progress, Internet-Draft, draft-ietf-netmod-yang-ver-selection-00, 17 March 2020, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . Wilton, et al. Expires 6 January 2027 [Page 65] Internet-Draft YANG Packages July 2026 [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 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, . [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, . [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, March 2019, . [RFC8528] Bjorklund, M. and L. Lhotka, "YANG Schema Mount", RFC 8528, DOI 10.17487/RFC8528, March 2019, . [RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data Structure Extensions", RFC 8791, DOI 10.17487/RFC8791, June 2020, . [RFC9195] Lengyel, B. and B. Claise, "A File Format for YANG Instance Data", RFC 9195, DOI 10.17487/RFC9195, February 2022, . Wilton, et al. Expires 6 January 2027 [Page 66] Internet-Draft YANG Packages July 2026 [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, . [RFC9911] Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911, DOI 10.17487/RFC9911, December 2025, . 14.2. Informative References [I-D.mahesh-opsawg-veloce-yang] Jethanandani, M., "YANG deVELpment PrOCEss and maintenance (VELOCE)", Work in Progress, Internet-Draft, draft-mahesh- opsawg-veloce-yang-01, 5 May 2026, . [RFC4844] Daigle, L., Ed. and IAB, "The RFC Series and RFC Editor", RFC 4844, DOI 10.17487/RFC4844, July 2007, . [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, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 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, . [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, . Wilton, et al. Expires 6 January 2027 [Page 67] Internet-Draft YANG Packages July 2026 [RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport", RFC 9000, DOI 10.17487/RFC9000, May 2021, . Appendix A. Package Examples This section provides various examples of YANG packages, and as such this text is non-normative. The purpose of the examples is to illustrate the file format of YANG packages, how package dependencies, exclusions, and package mounts work. It does not imply that such packages will be defined by IETF, or which modules would be included in those packages even if they were defined. The initial examples, in Appendix A.1, illustrate small, but complete YANG package definitions. For the remaining examples, the focus is on illustrating particular features of YANG packages, and so whilst the packages are complete and will compile, they leave out some of the optional fields. Long lines in examples are wrapped using the mechanism defined in [RFC8792]. A.1. Basic Package Examples This section provides some very simple examples of YANG package definitions that may be published by an SDO, illustrated using the instance data file format defined in Section 5.5. The version numbers chosen are somewhat arbitrary, and illustrative. Wilton, et al. Expires 6 January 2027 [Page 68] Internet-Draft YANG Packages July 2026 +========================+==========+==============================+ | Package | Versions | Content Overview | +========================+==========+==============================+ | example-base-types | 1.0.0, | Base IETF and IANA type | | | 1.1.0 | modules. | +------------------------+----------+------------------------------+ | example-network-device | 1.1.2 | Basic network device system, | | | | interface, access control, | | | | key chain, and IP modules. | +------------------------+----------+------------------------------+ | example-routing-types | 1.0.0 | Routing and BGP type | | | | modules. | +------------------------+----------+------------------------------+ | example-routing | 1.3.1 | Basic routing, routing | | | | policy, BGP, and ACL | | | | modules. | +------------------------+----------+------------------------------+ Table 1: Common example packages A.1.1. Example Basic Types YANG package, version 1.0.0 A very simple package with no dependencies on other packages that illustrates how a basic types package might be defined. In this case, the module dependencies have been declared as import-only, but they could also have been declared as implemented modules. file "example-base-types@1.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-base-types", "version": "1.0.0", "timestamp": "2026-03-20T17:52:47.188322Z", "organization": "IETF NETMOD Working Group", "contact": "WG Web: , \ WG List: ", "description": "Example package containing base IETF and \ IANA type modules", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "import-only-module": [ { "name": "ietf-yang-types", "version": "2010-09-24", Wilton, et al. Expires 6 January 2027 [Page 69] Internet-Draft YANG Packages July 2026 "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-types@2010-09-24.yang" ] }, { "name": "ietf-inet-types", "version": "2010-09-24", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-inet-types@2010-09-24.yang" ] }, { "name": "ietf-netconf-acm", "version": "2012-02-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-netconf-acm@2012-02-22.yang" ] } ] } } } } } A.1.2. Example Basic Types YANG package, version 1.1.0 An updated version of the basic types package that includes updated versions of the types modules and follows the YANG Semver versioning rules. Wilton, et al. Expires 6 January 2027 [Page 70] Internet-Draft YANG Packages July 2026 file "example-base-types@1.1.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-base-types", "version": "1.1.0", "version-description": "Updated to 2025 RFC module versions", "timestamp": "2026-03-20T17:52:47.188373Z", "description": "Example package containing base IETF and \ IANA type modules", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "import-only-module": [ { "name": "ietf-yang-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-yang-types@2025-12-22.yang" ] }, { "name": "ietf-inet-types", "version": "2025-12-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-inet-types@2025-12-22.yang" ] }, { "name": "ietf-netconf-acm", "version": "2018-02-14", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-netconf-acm@2018-02-14.yang" ] } ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 71] Internet-Draft YANG Packages July 2026 A.1.3. Example Network Device YANG package This section provides an instance data file example of a Network Device YANG package. This example package is intended to represent the standard set of YANG modules, with import dependencies, to implement a basic network device without any dynamic routing or layer 2 services. E.g., it includes functionality such as system information, interface and basic IP configuration. It includes the package (and hence all modules, enabled features, etc.) from the example-base-types package. This package also enables features for system authentication, including local users and RADIUS-based authentication, and enables IPv6 privacy autoconfiguration for the IP module. As for all 'complete' YANG packages, all import dependencies are fully resolved. Because this example uses YANG modules that have been standardized before YANG semantic versioning, the modules are referenced by revision date rather than version. file "example-network-device@1.1.2.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-network-device", "version": "1.1.2", "timestamp": "2018-12-13T17:00:00Z", "organization": "IETF NETMOD Working Group", "contact": "WG Web: , \ WG List: ", "description": "Example IETF network device YANG package. \ This package defines a small sample set of YANG modules that could \ represent the basic set of modules that a standard network device \ might be expected to support.", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-base-types", "version": "1.0.0", "location": [ "https://example.org/yang/packages/\ example-base-types@1.0.0.ypkg" ] } Wilton, et al. Expires 6 January 2027 [Page 72] Internet-Draft YANG Packages July 2026 ], "module": [ { "name": "iana-crypt-hash", "version": "2014-08-06", "location": [ "https://www.iana.org/assignments/yang-parameters/\ iana-crypt-hash@2014-08-06.yang" ] }, { "name": "ietf-system", "version": "2014-08-06", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-system@2014-08-06.yang" ] }, { "name": "iana-if-type", "version": "2026-03-17", "location": [ "https://www.iana.org/assignments/yang-parameters/\ iana-if-type@2026-03-17.yang" ] }, { "name": "ietf-interfaces", "version": "2018-02-20", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-interfaces@2018-02-20.yang" ] }, { "name": "ietf-netconf-acm", "version": "2018-02-14", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-netconf-acm@2018-02-14.yang" ] }, { "name": "ietf-key-chain", "version": "2017-06-15", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-key-chain@2017-06-15.yang" Wilton, et al. Expires 6 January 2027 [Page 73] Internet-Draft YANG Packages July 2026 ] }, { "name": "ietf-ip", "version": "2018-02-22", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-ip@2018-02-22.yang" ] } ], "feature": [ "ietf-system:authentication", "ietf-system:local-users", "ietf-system:radius", "ietf-system:radius-authentication", "ietf-ip:ipv6-privacy-autoconf" ] } } } } } A.1.4. Example Routing Types YANG package An example package that contains routing type modules used by the example routing package. The package imports the updated basic types package for common IETF and IANA type modules. The "ietf-routing-types" and "ietf-bgp-types" modules are included as implemented modules, rather than import-only modules, because they define identities that may be referenced at runtime. An alternative design would be to include them as import-only modules and then require any package containing modules that reference those identities to re-include them as implemented modules. file "example-routing-types@1.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-routing-types", Wilton, et al. Expires 6 January 2027 [Page 74] Internet-Draft YANG Packages July 2026 "version": "1.0.0", "timestamp": "2026-03-20T17:52:47.202513Z", "description": "Example package containing routing types \ modules", "includes": { "package": [ { "name": "example-base-types", "version": "1.1.0", "location": [ "https://example.org/yang/packages/\ example-base-types@1.1.0.ypkg" ] } ], "module": [ { "name": "ietf-routing-types", "version": "2017-12-04", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-routing-types@2017-12-04.yang" ] }, { "name": "ietf-bgp-types", "version": "2018-05-09", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-bgp-types@2018-05-09.yang" ] } ], "import-only-module": [ { "name": "iana-routing-types", "version": "2017-12-04", "location": [ "https://www.iana.org/assignments/yang-parameters/\ iana-routing-types@2017-12-04.yang" ] } ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 75] Internet-Draft YANG Packages July 2026 A.1.5. Example Basic Routing YANG package This section provides an instance data file example of a basic Routing YANG package formatted in JSON. This example package is intended to represent the standard set of YANG modules, with import dependencies, that builds upon the example- network-device and example-routing-types YANG packages to add support for basic dynamic routing and ACLs. The package also enables ACL features for matching IPv6 packet fields and configuring IPv6 ACL entries, with the expectation that all devices that implement this package will support these features. As for all YANG packages, all import dependencies are fully resolved. Because this example uses YANG modules that have been standardized before YANG semantic versioning, the modules are referenced by revision date rather than version. file "example-routing@1.3.1.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-routing", "version": "1.3.1", "timestamp": "2018-12-13T17:00:00Z", "description": "This package defines a small sample set of \ IETF routing YANG modules that could represent the set of IETF \ routing functionality that a basic IP network device might be \ expected to support.", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.1.2", "location": [ "https://example.org/yang/packages/\ example-network-device@1.1.2.ypkg" ] }, { "name": "example-routing-types", "version": "1.0.0", Wilton, et al. Expires 6 January 2027 [Page 76] Internet-Draft YANG Packages July 2026 "location": [ "https://example.org/yang/packages/\ example-routing-types@1.0.0.ypkg" ] } ], "module": [ { "name": "ietf-routing", "version": "2018-03-13", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-routing@2018-03-13.yang" ] }, { "name": "ietf-ipv4-unicast-routing", "version": "2018-03-13", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-ipv4-unicast-routing@2018-03-13.yang" ] }, { "name": "ietf-ipv6-unicast-routing", "version": "2018-03-13", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-ipv6-unicast-routing@2018-03-13.yang" ] }, { "name": "ietf-isis", "version": "2018-12-11", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-isis@2018-12-11.yang" ] }, { "name": "ietf-interfaces-common", "version": "2018-07-02", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-interfaces-common@2018-07-02.yang" ] }, { Wilton, et al. Expires 6 January 2027 [Page 77] Internet-Draft YANG Packages July 2026 "name": "ietf-if-l3-vlan", "version": "2017-10-30", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-if-l3-vlan@2017-10-30.yang" ] }, { "name": "ietf-routing-policy", "version": "2018-10-19", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-routing-policy@2018-10-19.yang" ] }, { "name": "ietf-bgp", "version": "2018-05-09", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-bgp@2018-05-09.yang" ] }, { "name": "ietf-access-control-list", "version": "2018-11-06", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-access-control-list@2018-11-06.yang" ] } ], "import-only-module": [ { "name": "ietf-packet-fields", "version": "2018-11-06", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-packet-fields@2018-11-06.yang" ] }, { "name": "ietf-ethertypes", "version": "2018-11-06", "location": [ "https://www.iana.org/assignments/yang-parameters/\ ietf-ethertypes@2018-11-06.yang" ] Wilton, et al. Expires 6 January 2027 [Page 78] Internet-Draft YANG Packages July 2026 } ], "feature": [ "ietf-access-control-list:match-on-ipv6", "ietf-access-control-list:ipv6" ] } } } } } A.2. Device Implementation Examples This section provides examples of how a device may implement YANG packages, and advertise them to clients. It reuses some of the example packages defined in Appendix A.1, but extended with device implementation specific modifications to those packages. A.2.1. device-routing YANG package This example illustrates a vendor's device-routing package that includes the example-routing package, and hence all its dependencies, but also removes a YANG module that is not implemented on the device, removes enabled features that are not supported, adds a YANG module containing deviations to other YANG modules, and adds a vendor device-isis-extensions YANG module, version 1.2.3, that augments the base ietf-isis package. Wilton, et al. Expires 6 January 2027 [Page 79] Internet-Draft YANG Packages July 2026 file "device-routing@1.0.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "device-routing", "version": "1.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example vendor device routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-routing", "version": "1.3.1" } ], "module": [ { "name": "vendor-ietf-bgp-deviations", "version": "2026-06-22" }, { "name": "device-isis-extensions", "version": "1.2.3" } ] }, "excludes": { "module": [ "ietf-if-l3-vlan" ], "feature": [ "ietf-system:radius", "ietf-system:radius-authentication" ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 80] Internet-Draft YANG Packages July 2026 A.2.2. YANG library advertisement for device-routing The following JSON fragment illustrates how the device may advertise the datastore schema using YANG library and YANG package bindings. The YANG library "module-set" contains the resolved set of modules for the device schema, but the module details are elided for brevity. The schema is bound to the "device-routing" package, and the top- level package list advertises the directly referenced package and all packages that it includes, recursively. Again, the contents of the packages have been elided for brevity, but the content matches the content previously illustrated in this document. file "device-routing-library.json" { "ietf-yang-instance-data:instance-data-set": { "name": "Device routing datastore schema", "description": "YANG library and package advertisement", "content-data": { "ietf-yang-library:library": { "module-set": [ { "name": "device-module-set", "module": [ "... implemented module details elided ..." ], "import-only-module": [ "... import-only module details elided ..." ] } ], "schema": [ { "name": "device-routing datastore schema", "module-set": [ "device-module-set" ], "ietf-yl-packages:package": [ { "name": "device-routing", "version": "1.0.0" } ] } ], "content-id": "3a6f9c2d7e0b1845" }, "ietf-yang-packages:packages": { "package": [ Wilton, et al. Expires 6 January 2027 [Page 81] Internet-Draft YANG Packages July 2026 { "name": "device-routing", "version": "1.0.0", "description": "Example vendor device routing package", "...": "package details elided" }, { "name": "example-routing", "version": "1.3.1", "description": "Example basic routing package", "...": "package details elided" }, { "name": "example-network-device", "version": "1.1.2", "description": "Example network device package", "...": "package details elided" }, { "name": "example-routing-types", "version": "1.0.0", "description": "Example routing types package", "...": "package details elided" }, { "name": "example-base-types", "version": "1.1.0", "description": "Example updated base types package", "...": "package details elided" }, { "name": "example-base-types", "version": "1.0.0", "description": "Example base types package", "...": "package details elided" } ] } } } } Wilton, et al. Expires 6 January 2027 [Page 82] Internet-Draft YANG Packages July 2026 A.2.3. Hotfix Package Example This example illustrates how a vendor can advertise a small hotfix package that updates one module in the device schema without publishing a complete replacement for the baseline device package. The hotfix package is marked as incomplete (i.e., "complete" = "false") because it contains only the updated device-isis-extensions module, and relies on the other packages bound to the datastore schema to provide the rest of the schema. The updated device-isis-extensions module uses version 1.2.4_compatible. This follows the YANG Semver versioning rules described in [I-D.ietf-netmod-yang-semver]. In this example, it is assumed that version 1.3.0 was not usable because it had previously been published with different content. file "vendor-isis-hotfix@1.0.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "vendor-isis-hotfix", "version": "1.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example vendor ISIS hotfix package", "reference": "XXX, draft-ietf-netmod-yang-packages;", "complete": false, "includes": { "module": [ { "name": "device-isis-extensions", "version": "1.2.4_compatible" } ] } } } } } When the hotfix package is used, the YANG library schema package binding lists both the baseline device package and the hotfix package, making use of automatic conflict resolution, as per Section 4.1, to automatically select the later version (1.2.4_compatible) of the device-isis-extensions YANG module. The YANG library module-set contents would be updated so that the "device-module-set" contains device-isis-extensions version Wilton, et al. Expires 6 January 2027 [Page 83] Internet-Draft YANG Packages July 2026 "1.2.4_compatible" rather than previous version, "1.2.3". The YANG library "content-id" would also change because the YANG library content has changed, and a yang-library-update notification would be generated. However, the goal is that the client doesn't need to fetch the updated YANG library information at all, and just rely on the advertised schema package bindings and the location URLs to fetch the packages and modules and fully resolve the schema off the device. file "device-routing-hotfix-library.json" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "name": "Device routing datastore schema with ISIS hotfix", "description": "YANG library and package advertisement", "content-data": { "ietf-yang-library:library": { "module-set": [ { "name": "device-module-set", "module": [ { "name": "device-isis-extensions", "revision": "2026-06-22", "ietf-yang-library-semver:version": \ "1.2.4_compatible" }, "... other implemented module details elided ..." ], "import-only-module": [ "... import-only module details elided ..." ] } ], "schema": [ { "name": "device-routing datastore schema", "module-set": [ "device-module-set" ], "ietf-yl-packages:package": [ { "name": "device-routing", "version": "1.0.0" }, { Wilton, et al. Expires 6 January 2027 [Page 84] Internet-Draft YANG Packages July 2026 "name": "vendor-isis-hotfix", "version": "1.0.0" } ] } ], "content-id": "9f2c6a0d4b8e7135" }, "ietf-yang-packages:packages": { "package": [ { "name": "vendor-isis-hotfix", "version": "1.0.0", "description": "Example vendor ISIS hotfix package", "...": "package details elided" }, "... other advertised package entries elided ..." ] } } } } A.3. Package Versioning Examples This section provides examples of versioning packages. The examples are non-normative, and for brevity only the relevant package definition fields are shown in the package instance-data files. The examples illustrate the history of a single package, "example- versioned-routing". Each example highlights whether the package definition changes are backwards-compatible (BC), non-backwards- compatible (NBC), or editorial. The following diagram summarizes the version lineage illustrated by the examples. The lineage is linear because these examples focus on successive updates to a single package definition. Wilton, et al. Expires 6 January 2027 [Page 85] Internet-Draft YANG Packages July 2026 1.0.0 - Initial published version | 1.1.0 - BC: add package, module, and mandatory features | 2.0.0 - NBC: downref package and remove module | 3.0.0 - NBC: add module containing deviations | 4.0.0 - NBC: remove IPv4 feature, downref module, and add module | 4.0.1 - Editorial: update module location information A.3.1. Initial Package Version The initial package version defines a small routing schema. This version is used as the starting point for the later examples. Wilton, et al. Expires 6 January 2027 [Page 86] Internet-Draft YANG Packages July 2026 file "example-versioned-routing@1.0.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "1.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.1.2" } ], "module": [ { "name": "example-routing-core", "version": "2.0.0" }, { "name": "example-routing-acl", "version": "1.0.0" } ], "feature": [ "example-routing-core:ipv4" ] } } } } } A.3.2. Backwards-compatible Update In version 1.1.0, a new included package, a new module, and new mandatory features are added. These are all backwards-compatible changes, so the minor version is incremented. Wilton, et al. Expires 6 January 2027 [Page 87] Internet-Draft YANG Packages July 2026 file "example-versioned-routing@1.1.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "1.1.0", "version-description": "Adds telemetry, policy, and new \ features.", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.1.2" }, { "name": "example-routing-telemetry", "version": "1.0.0" } ], "module": [ { "name": "example-routing-core", "version": "2.0.0" }, { "name": "example-routing-acl", "version": "1.0.0" }, { "name": "example-routing-policy", "version": "1.0.0" } ], "feature": [ "example-routing-core:ipv4", "example-routing-core:ipv6", "example-routing-policy:statistics" ] } } } } Wilton, et al. Expires 6 January 2027 [Page 88] Internet-Draft YANG Packages July 2026 } A.3.3. Package Downref and Module Removal In version 2.0.0, the "example-network-device" package reference is changed to an older package version, and the previously included "example-routing-acl" module is removed. Both changes are NBC, so the major version is incremented. Wilton, et al. Expires 6 January 2027 [Page 89] Internet-Draft YANG Packages July 2026 file "example-versioned-routing@2.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "2.0.0", "version-description": "Downrefs a package and removes the \ ACL module.", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.0.0" }, { "name": "example-routing-telemetry", "version": "1.0.0" } ], "module": [ { "name": "example-routing-core", "version": "2.0.0" }, { "name": "example-routing-policy", "version": "1.0.0" } ], "feature": [ "example-routing-core:ipv4", "example-routing-core:ipv6", "example-routing-policy:statistics" ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 90] Internet-Draft YANG Packages July 2026 A.3.4. Adding a Deviations Module In version 3.0.0, a new module containing deviations that modified some data nodes and marked other data nodes as not-supported. The deviations remove or restrict nodes that were present in the previous resolved package schema. The change is therefore NBC, and the major version is incremented. Wilton, et al. Expires 6 January 2027 [Page 91] Internet-Draft YANG Packages July 2026 file "example-versioned-routing@3.0.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "3.0.0", "version-description": "Adds NBC vendor deviations.", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.0.0" }, { "name": "example-routing-telemetry", "version": "1.0.0" } ], "module": [ { "name": "example-routing-core", "version": "2.0.0" }, { "name": "example-routing-policy", "version": "1.0.0" }, { "name": "vendor-routing-deviations", "version": "2026-06-22" } ], "feature": [ "example-routing-core:ipv4", "example-routing-core:ipv6", "example-routing-policy:statistics" ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 92] Internet-Draft YANG Packages July 2026 A.3.5. Mixed Backwards-compatible and NBC Changes In version 4.0.0, the mandatory "example-routing-core:ipv4" feature is removed and the "example-routing-core" module is changed to an older version. Both of these are NBC changes. A new "example-isis" module is also added, which would otherwise be a BC change, but the overall package update is still NBC, so the major version is incremented. file "example-versioned-routing@4.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "4.0.0", "version-description": "Removes IPv4, downrefs core, adds \ ISIS.", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.0.0" }, { "name": "example-routing-telemetry", "version": "1.0.0" } ], "module": [ { "name": "example-routing-core", "version": "1.5.0" }, { "name": "example-routing-policy", "version": "1.0.0" }, { "name": "vendor-routing-deviations", "version": "2026-06-22" }, { Wilton, et al. Expires 6 January 2027 [Page 93] Internet-Draft YANG Packages July 2026 "name": "example-isis", "version": "1.0.0" } ], "feature": [ "example-routing-core:ipv6", "example-routing-policy:statistics" ] } } } } } A.3.6. Editorial Location Update In version 4.0.1, the referenced module versions are unchanged, but location information for "example-routing-core" is updated. This does not change the resolved package schema, so it is an editorial package update. The same classification would apply if the module version had already been resolved from an included package and the package explicitly listed that same module version only to provide updated location information. file "example-versioned-routing@4.0.1.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-versioned-routing", "version": "4.0.1", "version-description": "Updates module location \ information.", "timestamp": "2026-06-22T00:00:00Z", "description": "Example versioned routing package", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-network-device", "version": "1.0.0" }, { "name": "example-routing-telemetry", "version": "1.0.0" Wilton, et al. Expires 6 January 2027 [Page 94] Internet-Draft YANG Packages July 2026 } ], "module": [ { "name": "example-routing-core", "version": "1.5.0", "location": [ "https://example.org/yang/\ example-routing-core@1.5.0.yang" ] }, { "name": "example-routing-policy", "version": "1.0.0" }, { "name": "vendor-routing-deviations", "version": "2026-06-22" }, { "name": "example-isis", "version": "1.0.0" } ], "feature": [ "example-routing-core:ipv6", "example-routing-policy:statistics" ] } } } } } A.4. Package Resolution Examples This section provides examples of package resolution. The examples are non-normative, and for brevity the package instance data files omit location information except where used to illustrate a specific point. Wilton, et al. Expires 6 January 2027 [Page 95] Internet-Draft YANG Packages July 2026 As described in Section 4, resolving a set of packages produces a YANG schema: a set of implemented modules, import-only modules, enabled features, deviations, and mount points. Included packages are recursively resolved first. The resulting package schemas are then combined using automatic module resolution, and finally any local module, import-only-module, feature, or exclusion entries in the including package are applied. A.4.1. Recursive Package Resolution The following examples define two versions of a common package. The access package includes version 1.0.0 of that common package, while the routing package includes version 1.4.0. This illustrates that package resolution is performed on the resolved module sets, not by choosing one package version and discarding the other package version. Wilton, et al. Expires 6 January 2027 [Page 96] Internet-Draft YANG Packages July 2026 file "example-resolution-common@1.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-resolution-common", "version": "1.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example common package for resolution \ examples", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "module": [ { "name": "example-resolution-base", "version": "1.0.0" } ], "import-only-module": [ { "name": "example-resolution-types", "version": "1.0.0" } ], "feature": [ "example-resolution-base:basic" ] } } } } } Resolved contents for "example-resolution-common" version 1.0.0: * Implemented modules: example-resolution-base@1.0.0. * Import-only modules: example-resolution-types@1.0.0. * Enabled features: example-resolution-base:basic. Since this package does not include any other packages, the resolved package schema is the module, import-only module, and feature set that it directly defines. Wilton, et al. Expires 6 January 2027 [Page 97] Internet-Draft YANG Packages July 2026 file "example-resolution-common@1.4.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-resolution-common", "version": "1.4.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Updated common package for resolution \ examples", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "module": [ { "name": "example-resolution-base", "version": "1.4.0" }, { "name": "example-resolution-telemetry", "version": "1.2.0" } ], "import-only-module": [ { "name": "example-resolution-types", "version": "1.4.0" } ], "feature": [ "example-resolution-base:basic", "example-resolution-telemetry:events" ] } } } } } Resolved contents for "example-resolution-common" version 1.4.0: * Implemented modules: example-resolution-base@1.4.0, example- resolution-telemetry@1.2.0. * Import-only modules: example-resolution-types@1.4.0. Wilton, et al. Expires 6 January 2027 [Page 98] Internet-Draft YANG Packages July 2026 * Enabled features: example-resolution-base:basic, example- resolution-telemetry:events. This newer package version selects newer versions of the base and types modules, and adds the telemetry module and its enabled feature. Wilton, et al. Expires 6 January 2027 [Page 99] Internet-Draft YANG Packages July 2026 file "example-resolution-access@2.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-resolution-access", "version": "2.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example access package for resolution \ examples", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-resolution-common", "version": "1.0.0" } ], "module": [ { "name": "example-resolution-acl", "version": "1.1.0", "location": [ "example:location-qux" ] }, { "name": "example-resolution-transport", "version": "1.2.0", "location": [ "example:location-foo", "example:location-bar" ] } ], "feature": [ "example-resolution-acl:ipv4" ] } } } } } Resolved contents for "example-resolution-access" version 2.0.0: Wilton, et al. Expires 6 January 2027 [Page 100] Internet-Draft YANG Packages July 2026 * Included packages: example-resolution-common@1.0.0. * Implemented modules: example-resolution-base@1.0.0, example- resolution-acl@1.1.0 [example:location-qux], example-resolution- transport@1.2.0 [example:location-foo, example:location-bar]. * Import-only modules: example-resolution-types@1.0.0. * Enabled features: example-resolution-base:basic, example- resolution-acl:ipv4. The included common package is resolved first, then the local ACL and transport modules and ACL feature are added. The ACL and transport module entries include location information; the transport module uses a shared primary location and an access-specific secondary location. Wilton, et al. Expires 6 January 2027 [Page 101] Internet-Draft YANG Packages July 2026 file "example-resolution-routing@3.0.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-resolution-routing", "version": "3.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Example routing package for resolution \ examples", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-resolution-common", "version": "1.4.0" } ], "module": [ { "name": "example-resolution-acl", "version": "1.3.0" }, { "name": "example-resolution-routing", "version": "1.3.0" }, { "name": "example-resolution-transport", "version": "1.2.0", "location": [ "example:location-foo", "example:location-baz" ] } ], "feature": [ "example-resolution-routing:statistics" ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 102] Internet-Draft YANG Packages July 2026 Resolved contents for "example-resolution-routing" version 3.0.0: * Included packages: example-resolution-common@1.4.0. * Implemented modules: example-resolution-base@1.4.0, example- resolution-telemetry@1.2.0, example-resolution-acl@1.3.0, example- resolution-routing@1.3.0, example-resolution-transport@1.2.0 [example:location-foo, example:location-baz]. * Import-only modules: example-resolution-types@1.4.0. * Enabled features: example-resolution-base:basic, example- resolution-telemetry:events, example-resolution- routing:statistics. The routing package includes the newer common package version, so its resolved package schema contains the newer base and import-only type modules, plus telemetry, routing, ACL, and transport modules. The transport module is the same version as in the access package, with the same primary location and a routing-specific secondary location. A.4.2. Local Entries and Exclusions The top-level device package includes both the access and routing packages. Recursively, this also brings in both versions of "example-resolution-common". There is no mechanism to exclude an included package. Instead, resolution operates on the modules and features contributed by those packages. This package locally selects version 1.1.0 of "example-resolution-acl", excludes the telemetry module, and excludes the routing statistics feature. Wilton, et al. Expires 6 January 2027 [Page 103] Internet-Draft YANG Packages July 2026 file "example-resolution-device@4.0.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-resolution-device", "version": "4.0.0", "timestamp": "2026-06-22T00:00:00Z", "description": "Top-level package for resolution examples", "reference": "XXX, draft-ietf-netmod-yang-packages", "includes": { "package": [ { "name": "example-resolution-access", "version": "2.0.0" }, { "name": "example-resolution-routing", "version": "3.0.0" } ], "module": [ { "name": "example-resolution-acl", "version": "1.1.0", "location": [ "example:location-quux" ] } ] }, "excludes": { "module": [ "example-resolution-telemetry" ], "feature": [ "example-resolution-routing:statistics" ] } } } } } Resolved contents for "example-resolution-device" version 4.0.0: Wilton, et al. Expires 6 January 2027 [Page 104] Internet-Draft YANG Packages July 2026 * Included packages: example-resolution-access@2.0.0, example- resolution-routing@3.0.0, example-resolution-common@1.0.0, example-resolution-common@1.4.0. * Implemented modules: example-resolution-base@1.4.0, example- resolution-transport@1.2.0 [example:location-foo, example:location-bar, example:location-baz], example-resolution- acl@1.1.0 [example:location-quux], example-resolution- routing@1.3.0. * Import-only modules: example-resolution-types@1.0.0, example- resolution-types@1.4.0. * Enabled features: example-resolution-base:basic, example- resolution-acl:ipv4. The common package is still listed at both versions because packages themselves are not excluded during resolution; instead, automatic module resolution selects example-resolution-base@1.4.0 from the two common package versions. The local module entry for example- resolution-acl@1.1.0 overrides the newer ACL version inherited from the routing package. Since the local ACL module entry is explicitly listed by the device package, its location list also replaces the location list inherited from the access package for the same ACL module version. The telemetry module is removed by the excludes/ module list, which also removes its enabled feature. The routing statistics feature is explicitly removed by the excludes/feature list. If multiple package entries contribute the same module at the same version, the resulting module entry is only included once and the location lists are merged. In this example, "example-resolution- transport" version 1.2.0 is included via both the access and routing packages. Both paths list the same primary location, and each path also lists a different secondary location. The resolved module entry contains the deduplicated union of those locations: the shared primary location, the access-specific secondary location, and the routing-specific secondary location. A.5. Package Exclusion Examples This section provides examples of how to exclude modules, and packages in a package definition, and to remove enabled features. The examples are non-normative, and for brevity, some expected information (e.g., locations) are omitted. Wilton, et al. Expires 6 January 2027 [Page 105] Internet-Draft YANG Packages July 2026 A.5.1. Example of excluding modules and an enabled feature The following example defines two YANG packages. The first package, "example-ab", implements two example modules, "example-module-a" and "example-module-b", two related types modules, and declares two enabled features. The second package, "example-c", imports the first package, but excludes the implemented "example-module-a" module, the import-only "example-module-b-types" module, and the enabled feature "bar" from the "example-module-b" module. TODO - Should that feature have been implicitly removed? The third figure shows the resulting schema in YANG Library format, but with namespaces and locations elided for brevity. Wilton, et al. Expires 6 January 2027 [Page 106] Internet-Draft YANG Packages July 2026 file "example-ab@0.1.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-ab", "version": "0.1.0", "timestamp": "2026-03-20T17:52:47.188303Z", "description": "Example package defining modules A, B and \ associated types", "includes": { "module": [ { "name": "example-module-a", "version": "1.0.0" }, { "name": "example-module-b", "version": "1.1.0" } ], "import-only-module": [ { "name": "example-module-a-types", "version": "1.0.0" }, { "name": "example-module-b-types", "version": "1.1.0" } ], "feature": [ "example-module-a:foo", "example-module-b:bar" ] } } } } } The "example-c" Yang Package example illustrates exclusions of modules, import-only-modules and features. Wilton, et al. Expires 6 January 2027 [Page 107] Internet-Draft YANG Packages July 2026 file "example-c@0.1.0.ypkg" =============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-yang-instance-data:instance-data-set": { "content-data": { "ietf-yang-package-instance:package": { "name": "example-c", "version": "0.1.0", "timestamp": "2026-03-20T17:52:47.202747Z", "description": "Example package importing A, removing B and \ adding C", "includes": { "package": [ { "name": "example-ab", "version": "0.1.0", "location": [ "https://example.org/yang/packages/\ example-ab@0.1.0.ypkg" ] } ], "module": [ { "name": "example-module-c", "version": "2.0.0" } ] }, "excludes": { "module": [ "example-module-b" ], "import-only-module": [ { "name": "example-module-b-types" } ], "feature": [ "example-module-b:bar" ] } } } } } Wilton, et al. Expires 6 January 2027 [Page 108] Internet-Draft YANG Packages July 2026 The following JSON illustrates what a resulting YANG library file would look like once all dependencies in the "example-c" YANG package have been resolved. file "example-c-library@0.1.0.ypkg" { "ietf-yang-instance-data:instance-data-set": { "name": "Package example-c@0.1.0 schema", "description": "YANG package definition", "content-data": { "ietf-yang-library:library": { "module-set": [ { "name": "Package example-c@0.1.0", "module": [ { "name": "example-module-c", "revision": "2.0.0", "ietf-yang-library-semver:version": "2.0.0" }, { "name": "example-module-a", "revision": "1.0.0", "ietf-yang-library-semver:version": "1.0.0", "feature": [ "foo" ] } ], "import-only-module": [ { "name": "example-module-a-types", "revision": "1.0.0", "ietf-yang-library-semver:version": "1.0.0" } ] } ], "schema": [ { "name": "Package example-c@0.1.0 schema", "module-set": [ "Package example-c@0.1.0" ] } ], "content-id": "c826ea09" } Wilton, et al. Expires 6 January 2027 [Page 109] Internet-Draft YANG Packages July 2026 } } } A.6. Mounted Package Examples This section provides examples of XXX when using mounted packages. The examples are non-normative, and for brevity, some expected information (e.g., locations) are omitted. A.6.1. Example of package with a mounted package This example illustrates a YANG package representing a network device that mounts a routing package at the network-instance mount point. TODO - Can we use example that is the same, or very similar, to the network-instances example? TODO - Indicate that this is a minimal example to illustrate a concept, and leaves out some optional elements that would be expected in a full implementation. A.6.2. Example of a package replacing the mounted schema This example illustrates an implementation of the mounted package defined in XXX, but that modifies the mounted package. Although this example illustrates applying deviations to the schema of a mounted package, the same mechanism can be used to change the implemented package version, remove a mounted package in its entirety, remove modules from a mounted package, change enabled features, change the behavior of recursive mounts, etc. TODO - Probably need more than one example. Authors' Addresses Robert Wilton (editor) Cisco Systems, Inc. Email: rwilton@cisco.com Reshad Rahman Equinix Email: reshad@yahoo.com Wilton, et al. Expires 6 January 2027 [Page 110] Internet-Draft YANG Packages July 2026 Joe Clarke Cisco Systems, Inc. Email: jclarke@cisco.com Jason Sterne Nokia Email: jason.sterne@nokia.com Wilton, et al. Expires 6 January 2027 [Page 111]