YANG PackagesCisco Systems, Inc.rwilton@cisco.comEquinixreshad@yahoo.comCisco Systems, Inc.jclarke@cisco.comNokiajason.sterne@nokia.comThis document defines YANG packages: versioned organizational
structures used to manage the schema and conformance of a set of
YANG modules as a cohesive unit.This document defines and describes the YANG
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 ,accessed as instance data files , 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.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 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
.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.There are several alternative approaches to managing YANG schema.
These include: Using YANG library, along with YANG Instance Data files
,Using git tags and version labels for modules maintained on
GitHub,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/yangAlthough 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.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/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
when, and only when,
they appear in all capitals, as shown here.This document uses the following terminology introduced in
YANG Semantic Versioning :
YANG SemverThis document uses the following terminology introduced in
the Network Management Datastore Architecture :
datastore schemaThis document uses the following terminology introduced in
the YANG 1.1 Data Modeling Language :
data nodeschema nodeTree diagrams used in this document follow the notation defined in
.In addition, this document defines the following terminology: 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 .YANG package: The versioned organizational structure defined in
. 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 . When used in the
context of a YANG package, it follows the definition in .non-backwards-compatible (NBC) change: When used in the context
of a YANG module, it follows the definition in Section 3.1.2 of
. When used
in the context of a YANG package, it follows the definition in .editorial change: When used in the context of a YANG module, it
follows the definition of an 'editorial change' in 4.4 of . When used in the
context of a YANG package, it follows the definition in .resolved package schema: The resolved package schema is the YANG
schema defined by a package after package resolution has been
performed, as defined in . 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'.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.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:For a YANG package to be valid, it MUST conform to all the
following rules: Each (package name, version) pairing MUST define a globally
unique version of that package definition.Each YANG package name MUST be globally unique to avoid issues
with tools and caching, e.g., using the mechanisms specified in
.YANG packages MUST be versioned using YANG Semver,
. Versioning YANG
packages is further described in .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 .
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.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.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
.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.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
.Multiple versions/revisions of an import-only module MAY be
listed, but any extraneous import-only module versions SHOULD be
removed.A package definition MUST NOT include the same module name in
both the 'includes/module' and 'excludes/module' lists.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.A package definition MUST NOT include the same feature name in
both the 'includes/feature' and 'excludes/feature' lists.A package definition MUST NOT exclude a module and list features
defined by that module in the 'includes/feature' list.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.Finally, standard rules for YANG instance data apply. E.g.,
entries in the various lists MUST be unique by any list key.A YANG package may represent a schema that is 'referentially
complete', or 'referentially incomplete', indicated in the package
definition by the 'complete' flag.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 for details on cases
when referentially incomplete packages are helpful.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.As defined in and , 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.YANG Schema Mount 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., defines a YANG
Model for Network Instances, that uses YANG mount points to mount IETF
routing protocol YANG modules within the network instance list. 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
.
If a server implements the YANG library package bindings defined in
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,
.A package definition may exclude modules or enabled features. The
mechanism for this is described in , and
the conformance implications are described in
.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:
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 ,
with Schema Mount if mount points are used.
E.g., see .The following process defines how a YANG package definition is
resolved, using two explicit steps:
Step 1: recursively resolve each package in the
"includes/package" list using this same two-step process.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
, 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-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 ignored. Hence, the
first occurrence of each location is retained and the relative order
of non-duplicate locations is preserved.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:
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
and
. Any
"_compatible" or "_non_compatible" modifier, pre-release metadata,
and build metadata are ignored for this comparison:
The module with the highest MAJOR version component is chosen.Otherwise, if the MAJOR version components are the same, then the module
with the highest MINOR version component is chosen.Otherwise, the module with the highest PATCH version component is chosen.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.If neither module has a version statement that matches the YANG
Semver format, then the module with the most recent revision-date is
chosen.If there is no difference in version or revision-dates to
distinguish between two modules then:
Submodule information, if present, for both module definitions
is assumed to be equivalent and hence either can be used.the location leaf-lists for the module definitions are
merged using the location-lists
rule.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.Where possible, package definitions SHOULD be made available offline in
Package Instance Data files, see , 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 .As per , 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.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
.As per section 9.10.2, identities are
only available for use by the server for implemented modules.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 , 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.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 .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.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 .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 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.The "ietf-yang-packages" YANG module has the following
structure: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 .This means that conflicting module versions between the listed
packages are resolved using the automatic module version resolution
rules in . As a result,
the version that wins those rules 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
).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
, 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: /pkgs:packages/package/name
| +--ro version leafref
| +--ro location* inet:uri
+--ro additional-feature* pkg-types:scoped-feature
]]>YANG packages SHOULD be made available offline from the server,
defined as YANG instance data files 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
.The following rules apply to the format of the YANG package instance
files:The file MUST be encoded in JSON.The name of the file MUST follow the format
"<package-name>@<version>.ypkg", and the package-name
and version MUST match the values specified in the package
container's 'name' and 'version' leafs.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.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.The instance-data file can specify a schema:
The default schema for .ypkg files is
"ietf-inst-data-pkg-schema.ypkg", defined in
. 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
and
.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.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.The 'revision' list in the instance data file MUST NOT be used,
since versioning is handled by the package definition.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:YANG package definitions can be used to define the content schema for
YANG instance data files, extending the content schema definition in
. 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:The following example shows how the example in 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.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 \
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"
]
}
]
}
}
}
}
}
]]>As defined in , YANG packages are
versioned using . This
section describes how those rules apply to YANG package definitions.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 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.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.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.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.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.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
may be helpful,
additional IETF specific guidance for managing IETF package definitions
may be provided in a future RFC, pending the output of
.Better and easier conformance is a major design goal for YANG packages. YANG
package conformance is similar to how YANG
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 (),
to a YANG schema that is defined as a set of implemented modules and
import-only modules, deviations, features, and mounted 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.Sometimes a package definition may include multiple packages that
implement different versions of a module.As per the package definition rules in , 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 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.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 , when multiple included packages define
different versions of the same package, then both versions are retained
in the resolved package schema.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.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
.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.The YANG language, 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.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.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. 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.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.As defined by NMDA , each datastore has
an associated datastore schema. These datastore schemas can be
advertised by servers using YANG Library ,
augmented with the associated YANG package information, as per
. 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): 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.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.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.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 .The "ietf-yang-package-types" module imports "ietf-yang-revisions"
,
"ietf-yang-semver" ,
"ietf-yang-types" , and "ietf-inet-types"
. 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;
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";
}
/*
* 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;
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";
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
"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.";
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;
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 {
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
"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;
}
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;
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
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
"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.";
}
}
}
}
]]>The "ietf-yang-package-instance" module imports "ietf-yang-semver"
,
"ietf-yang-package-types" defined in this document, and
"ietf-yang-structure-ext" . 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
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;
}
}
]]>The "ietf-yang-package" module imports "ietf-yang-semver"
and
"ietf-yang-package-types" defined in this document. 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.";
// 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.
*/
container packages {
config false;
description "All YANG package definitions";
list package {
key "name version";
description
"YANG package instance";
uses pkg-types:yang-pkg-instance;
}
}
}
]]>The "ietf-yl-packages" module imports "ietf-yang-revisions"
,
"ietf-yang-semver" ,
"ietf-yang-package-types" and "ietf-yang-packages" defined in this
document, and "ietf-yang-library" . 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.";
}
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
// 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 {
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.";
}
}
}
]]>The "ietf-yang-inst-data-pkg" module imports "ietf-yang-revisions"
,
"ietf-yang-semver" ,
"ietf-yang-package-types" defined in this document,
"ietf-inet-types" , "ietf-yang-structure-ext"
, and "ietf-yang-instance-data"
. 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 {
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.
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.";
}
}
}
}
}
]]>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": [
{
"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"
]
}
]
}
}
}
}
}
]]>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
.YANG packages also offer an alternative
mechanism to YANG Library 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 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.This section is modeled after the template described in Section 3.7
of .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 and
RESTCONF . These YANG-based management protocols (1)
have to use a secure transport layer (e.g., SSH ,
TLS , and QUIC ) and (2) have
to use mutual authentication.The Network Configuration Access Control Model (NACM)
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').YANG packages provide an alternative mechanism to YANG Library
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.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.This document requests IANA to registers a URI in the "IETF XML
Registry" . Following the format in RFC 3688,
the following registrations are requested.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-package-typesRegistrant Contact: The IESG.XML: N/A, the requested URI is an XML namespace.URI:
urn:ietf:params:xml:ns:yang:ietf-yang-package-instanceRegistrant Contact: The IESG.XML: N/A, the requested URI is an XML namespace.URI: urn:ietf:params:xml:ns:yang:ietf-yang-packagesRegistrant Contact: The IESG.XML: N/A, the requested URI is an XML namespace.URI: urn:ietf:params:xml:ns:yang:ietf-yl-packagesRegistrant Contact: The IESG.XML: N/A, the requested URI is an XML namespace.URI: urn:ietf:params:xml:ns:yang:ietf-yang-inst-data-pkgRegistrant 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 :
Name: ietf-yang-package-typesNamespace:
urn:ietf:params:xml:ns:yang:ietf-yang-package-typesPrefix: pkg-typesReference: RFC XXXXName: ietf-yang-package-instanceNamespace:
urn:ietf:params:xml:ns:yang:ietf-yang-package-instancePrefix: pkg-instReference: RFC XXXXName: ietf-yang-packagesNamespace:
urn:ietf:params:xml:ns:yang:ietf-yang-packagesPrefix: pkgsReference: RFC XXXXName: ietf-yl-packagesNamespace: urn:ietf:params:xml:ns:yang:ietf-yl-packagesPrefix: yl-pkgsReference: RFC XXXXName: ietf-yang-inst-data-pkgNamespace:
urn:ietf:params:xml:ns:yang:ietf-yang-inst-data-pkgPrefix: yid-pkgReference: RFC XXXXThis 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 packagea brief description of the package purposeThe latest published package versionA list of all published package versions, each hyperlinked to the
location where a package instance data file,
, 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 , should be added.For allocation, the registration policy is Specification Required,
as defined in . All registered YANG package
names must comply with the rules for identifiers stated in Section 6.2,
and must have a package name prefix.The package name prefix 'ietf-' is reserved for YANG packages managed
and published under the IETF stream , 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.This document requests IANA to register the following media type,
following the procedures of :Type name: applicationSubtype name: ypkgRequired parameters: N/AOptional parameters: N/AEncoding 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/APublished specification: RFC XXXXApplications that use this media type: YANG tooling and servers
that generate or consume YANG package instance data files.Additional information:
Magic number(s): NoneFile extension(s): ypkgMacintosh file type code(s): 'Text'Fragment identifiers: N/APerson & Email address to contact for further information:
NETMOD WG (mailto:netmod@ietf.org)Intended usage: COMMONRestrictions on usage: N/AAuthor: IETFChange controller: IESGFeedback 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.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.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 , 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
.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
. The version numbers chosen are somewhat
arbitrary, and illustrative.PackageVersionsContent Overviewexample-base-types1.0.0, 1.1.0Base IETF and IANA type modules.example-network-device1.1.2Basic network device system, interface, access control, key chain,
and IP modules.example-routing-types1.0.0Routing and BGP type modules.example-routing1.3.1Basic routing, routing policy, BGP, and ACL modules.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",
"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"
]
}
]
}
}
}
}
}
]]>An updated version of the basic types package that includes updated
versions of the types modules and follows the YANG Semver versioning
rules. 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"
]
}
]
}
}
}
}
}
]]>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"
]
}
],
"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"
]
},
{
"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"
]
}
}
}
}
}
]]>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",
"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"
]
}
]
}
}
}
}
}
]]>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",
"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"
]
},
{
"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"
]
}
],
"feature": [
"ietf-access-control-list:match-on-ipv6",
"ietf-access-control-list:ipv6"
]
}
}
}
}
}
]]>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 , but extended with
device implementation specific modifications to those packages.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. 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"
]
}
}
}
}
}
]]>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": [
{
"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"
}
]
}
}
}
}
]]>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 . 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
, 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
"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"
},
{
"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 ..."
]
}
}
}
}
]]>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.The initial package version defines a small routing schema. This
version is used as the starting point for the later examples. 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"
]
}
}
}
}
}
]]>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. 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"
]
}
}
}
}
}
]]>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. 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"
]
}
}
}
}
}
]]>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. 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"
]
}
}
}
}
}
]]>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"
},
{
"name": "example-isis",
"version": "1.0.0"
}
],
"feature": [
"example-routing-core:ipv6",
"example-routing-policy:statistics"
]
}
}
}
}
}
]]>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"
}
],
"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"
]
}
}
}
}
}
]]>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.As described in , 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.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. 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. 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.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. 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:
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. 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"
]
}
}
}
}
}
]]>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.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. 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:
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.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.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. 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. 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"
]
}
}
}
}
}
]]>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"
}
}
}
}
]]>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.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.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.