]> Cisco Systems, Inc.

7200-12 Kit Creek Rd Research Triangle Park North Carolina United States of America +1-919-392-2867 jclarke@cisco.com

Cisco Systems, Inc.

De Kleetlaan 6a b1 1831 Diegem Belgium +32 2 704 5622 bclaise@cisco.com

This document specifies a YANG module that contains metadata related to YANG modules and vendor implementations of those YANG modules.

YANG became the standard data modeling language of choice. Not only is it used by the IETF for specifying models, but also in many Standard Development Organizations (SDOs), consortia, and open-source projects: the IEEE, the Broadband Forum (BFF), DMTF, MEF, ITU, OpenDaylight, Open ROADM, Openconfig, sysrepo, and more. With the rise of data model-driven management and the success of YANG as a key piece comes a challenge: the entire industry develops YANG models. In order for operators to automate coherent services, the industry must ensure the following: Data models must work together There exists a toolchain to help one search and understand models Metadata is present to further describe model attributes The site (and the YANG catalog that it provides) is an attempt to address these key tenants. From a high level point of view, the goal of this catalog is to become a reference for all YANG modules available in the industry, for both YANG developers (to search on what exists already) and for operators (to discover the more mature YANG models to automate services). This YANG catalog should not only contain pointers to the YANG modules themselves, but also contains metadata related to those YANG modules: What is the module type (service model or not?); what is the maturity level? (e.g., for the IETF: is this an RFC, a working group document or an individual draft?); is this module implemented?; who is the contact?; is there open-source code available? And we expect much more in the future. The industry starts to understand that the metadata related to YANG models become equally important as the YANG models themselves. This document defines a YANG module called yang-catalog.yang that contains the metadata definitions, that must be kept next to the YANG module specification. The YANG module design is based on experience and real code. As such, it's expected that this YANG module will be a living document. Furthermore, new use cases, which require new metadata in this YANG module, are discovered on a regular basis.

The top open issues are: Add a leaf to indicate the tree type relative to Obtain feedback from vendors and SDOs Socialize module at the IETF and incorporate feedback

While implementing the catalog and tools at yangcatalog.org, we initially looked at the "Catalog and registry for YANG models" as a starting point but we quickly realized that the objectives are different. As a consequence, even if some of the information is similar, this YANG module started to diverge. [TO BE EXPANDED ON THE DIFFERENT OBJECTIVES.] Below are our observations and the justifications for the divergence.

In order for the YANG catalog to become a complete inventory of which models are supported on the different platforms, content such as the support of the YANG module/deviation/feature/etc. should be easy to import and update. An easy way to populate this information is to have a similar structure as the YANG Module Library . That way, querying the YANG Module Library from a platform provides, directly in the right format, the input for the YANG catalog inventory. There are some similar entries between the YANG Module Library and the Openconfig catalog. For example, the Openconfig catalog model defines a "uri" leaf which is similar to "schema" from ). And this adds to the overall confusion.

The structure of the yang-catalog.yang module described in this document is found below:

module: yang-catalog +--rw catalog +--rw modules | +--rw module* [name revision] | +--rw name yang:yang-identifier | +--rw revision union | +--rw datastore* identityref | +--rw schema? inet:uri | +--rw namespace inet:uri | +--rw feature* yang:yang-identifier | +--rw deviation* [name revision] | | +--rw name yang:yang-identifier | | +--rw revision union | +--rw conformance-type enumeration | +--rw submodule* [name revision] | | +--rw name yang:yang-identifier | | +--rw revision union | | +--rw schema? inet:uri | +--rw document-name? string | +--rw author-email? string | +--rw compilation-status? enumeration | +--rw compilation-result? string | +--rw reference? string | +--rw prefix? string | +--rw yang-version? string | +--rw organization? string | +--rw description? string | +--rw contact? string | +--rw maturity-level? enumeration | +--rw implementations | +--rw implementation* [vendor platform software-version software-flavor] | +--rw vendor string | +--rw platform string | +--rw software-version string | +--rw software-flavor string | +--rw os-version? string | +--rw feature-set? string | +--rw os-type? string +--rw vendors +--rw vendor* [name] +--rw name string +--rw platforms +--rw platform* [name] +--rw name string +--rw software-versions +--rw software-version* [name] +--rw name string +--rw software-flavors +--rw software-flavor* [name] +--rw name string +--rw protocols | +--rw protocol* [name] | +--rw name enumeration | +--rw protocol-version? string | +--rw capabilities* string +--rw modules +--rw module* [name revision] +--rw name -> ../../../../../../../../../../../modules/module/name +--rw revision -> ../../../../../../../../../../../modules/module/revision

Various elements of this module tree will be discussed in the subsequent sections.

Each module in the YANG Catalog is enumerated by its metadata and by various vendor implementations. Within the "module" sub-tree, each module is listed using its YANG Module Library "module-list" grouping information. The yang-catalog module then augments the grouping to add metadata elements that will aid module developers and module consumers alike in understanding the relative maturity, compilation status, and the support contact(s) of each YANG module.

+--rw module* [name revision] +--rw name yang:yang-identifier +--rw revision union +--rw schema? inet:uri +--rw namespace inet:uri +--rw feature* yang:yang-identifier +--rw deviation* [name revision] | +--rw name yang:yang-identifier | +--rw revision union +--rw conformance-type enumeration +--rw submodule* [name revision] | +--rw name yang:yang-identifier | +--rw revision union | +--rw schema? inet:uri +--rw document-name? string +--rw author-email? string +--rw compilation-status? enumeration +--rw compilation-result? string +--rw reference? string +--rw prefix? string +--rw yang-version? string +--rw organization? string +--rw description? string +--rw contact? string +--rw module-type? enumeration +--rw maturity-level? enumeration +--rw implementations +--rw implementation* [vendor platform software-version software-flavor] +--rw vendor string +--rw platform string +--rw software-version string +--rw software-flavor string +--rw os-version? string +--rw feature-set? string +--rw os-type? string

Many of these additional metadata fields are self-explanatory, especially given their descriptions in the module itself. However, those requiring additional explanation or context as to why they are needed are described in the subsequent sections.

For the inventory to be complete, YANG modules at different stage of maturity should be taken into account, including YANG modules that are clearly work-in-progress, i.e. that do not validate correctly, either because of a faulty YANG constructs, because of a faulty imported YANG module, or simply because of a warnings. Note that some of those warnings are not always show-stoppers from a code generation point of view. Nonetheless, the compilation or validation status, along with the compilation output, provide a clear indication on the YANG module development phase and stability.

leaf compilation-status { description "Status of the module, whether it was possible to compile this YANG module or there are still some errors/warnings."; type enumeration { enum PASSED { value 0; description "In case that all compilers were able to compile this YANG module without any error/warning."; } enum PASSED-WITH-WARNINGS { value 1; description "In case that all compilers were able to compile this YANG module without any error, but at least one of them caught some warning."; } enum FAILED { value 2; description "In case that at least one of compilers found some error while compiling this YANG module."; } enum MISSING { value 3; description "In case that there is not sufficient information about compilation status."; } } } leaf compilation-result { type string; description "Result of the compilation explaining specifically what error or warning occurred. This is not existing if compilation status is PASSED."; }

Figure 1: Compilation Status and Compilation Result The compilation status and result have been added as two extra leaves, for each YANG module.

Models also have inherent maturity levels from their respective Standards Development Organizations (SDOs). These maturity levels will help model consumers understand how complete, tested, etc. a model is.

leaf maturity-level { description "The current maturity of the module with respect to the body that created it. This allows one to understand where the module is in its overall life cycle."; type enumeration { enum ratified { value 0; description "Maturity of a module that is fully approved (e.g., a standard)."; } enum working-group { value 1; description "Maturity of a module that is actively being developed by a organization towards ratification."; } enum individual { value 2; description "Maturity of a module that has been initially created, but has no official organization-level status."; } } }

This enumeration mapping has been implemented for the YANG modules from IETF and BBF. With respect to vendor-specific modules, this same enumeration should be used and mapped to the internal vendor release or development names. Once a module has been completed, fully tested, and is stable, its maturity level should be "ratified".

As of version 02 of openconfig-model-catalog.yang it is not possible to identify the implementations of one specific module. Instead modules are grouped into feature-bundle, and feature-bundles are implemented by devices. Because of this, we added our own implementation sub-tree under each module to yang-catalog.yang. Our implementation sub-tree is:

+--rw implementation* [vendor platform software-version software-flavor] +--rw vendor string +--rw platform string +--rw software-version string +--rw software-flavor string +--rw os-version? string +--rw feature-set? string +--rw os-type? string

The keys in this sub-tree can be used in the "vendor" sub-tree defined below to walk through each vendor, platform, and software release to get a full list of supported YANG modules for that release. The "software-flavor" key leaf identifies a variation of a specific version where YANG model support may be different. Depending on the vendor, this could be a license, additional software component, or a feature set. The other non-key leaves in the implementation sub-tree represent optional elements of a software release that some vendors may choose to use for informational purposes.

The vendor sub-tree provides a way, especially for module consumers, to walk through a specific device and software release to find a list of modules supported therein. This sub-tree turns the "implementation" sub-tree on its head to provide an optimized index for one wanting to go from a platform to a full list of modules. In addition to the module list, the vendor sub-tree lists the YANG-based protocols (e.g., NETCONF or RESTCONF) that the platforms support.

+--rw vendor* [name] +--rw name string +--rw platforms +--rw platform* [name] +--rw name string +--rw software-versions +--rw software-version* [name] +--rw name string +--rw software-flavors +--rw software-flavor* [name] +--rw name string +--rw protocols | +--rw protocol* [name] | +--rw name enumeration | +--rw protocol-version? string | +--rw capabilities* string +--rw modules +--rw module* [name revision] +--rw name -> ../../../../../../../../../../../modules/module/name +--rw revision -> ../../../../../../../../../../../modules/module/revision

This sub-tree structure also enables one to look for YANG modules for a class of platforms (e.g., list of modules for Cisco, or list of modules for Cisco ASR9000 routers) instead of only being able to look for YANG modules for a specific platform and software release.

Another challenge with using as the canonical catalog is the regular expression syntax it uses. The Openconfig module uses a POSIX-compliant regular expression syntax whereas YANG-based protocol implementations like ConfD expect the IETF-chosen W3C syntax. In order to load the Openconfig catalog in such engines, changes to the regular expression syntax had to be done, and these one-off changes are not supportable.

The YANG Catalog module is currently targeted to address the following use cases.

The yangcatalog.org toolchain provides a service for searching for YANG modules based on keywords. The resulting search data currently stores the module and node metadata in a proprietary format along with the search index data. By populating the yang-catalog module, this search service can instead pull the metadata from the implementation of the module. Populating this instance of the yang-catalog module will be using an API that is still under development, but will ultimately allow SDOs and vendors to provide metadata and ensure the search service has the most up-to-date data for all available modules.

By organizing the yang-catalog module so that one can either find all implementations for a given module, or find all modules supported by a vendor platform and software release, the catalog will provide a straight-forward way for one to understand the extent of YANG module support in participating vendors' software images. Eventually a web-based graphical interface will be connected to this on yangcatalog.org to make it easier for consumers to leverage the instance of the yang-catalog module for this use case.

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

file "yang-catalog@2017-07-03.yang" module yang-catalog { namespace "urn:ietf:params:xml:ns:yang:yang-catalog"; prefix yc; import ietf-yang-library { prefix yanglib; } organization "yangcatalog.org"; contact "Benoit Claise Joe Clarke "; description "This module contains metadata pertinent to each YANG module, as well as a list of vendor implementations for each module. The structure is laid out in such a way as to make it possible to locate metadata and vendor implementation on a per-module basis as well as obtain a list of available modules for a given vendor's platform and specific software release."; revision 2017-07-03 { description "Initial revision."; reference " YANG Catalog "; } container catalog { description "Root container of yang-catalog holding two main branches - modules and vendors. The modules sub-tree contains all the modules in the catalog and all of their metadata with their implementations. The vendor sub-tree holds modules for specific vendors, platforms, software-versions, and software-flavors. It contains reference to a name and revision of the module in order to reference the module's full set of metadata."; container modules { description "Container holding the list of modules"; uses yanglib:module-list; } // end of modules container vendors { description "Container holding lists of organizations that publish YANG modules."; list vendor { key name; description "List of organizations publishing YANG modules."; leaf name { type string; description "Name of the maintaining organization -- the name should be supplied in the official format used by the organization. Standards Body examples: IETF, IEEE, MEF, ONF, etc. Commercial entity examples: AT&T, Facebook, Name of industry forum examples: OpenConfig, OpenDaylight, ON.Lab"; } container platforms { description "Container holding list of platforms."; list platform { key name; description "List of platforms under specific vendor"; leaf name { type string; description "Name of the platform"; } container software-versions { description "Container holding list of versions of software versions."; list software-version { key name; description "List of version of software versions under specific vendor, platform."; leaf name { type string; description "Name of the version of software. With respect to most network device appliances, this will be the operating system version. But for other YANG module implementation, this would be a version of appliance software. Ultimately, this should correspond to a version string that will be recognizable by the consumers of the platform."; } container software-flavors { description "Container holding list of software flavors."; list software-flavor { key name; description "List of software flavors under specific vendor, platform, software-version."; leaf name { type string; description "A variation of a specific version where YANG model support may be different. Depending on the vendor, this could be a license, additional software component, or a feature set."; } container protocols { description "List of the protocols"; list protocol { key name; description "YANG-based protocol that is used on the device. This enumeration will is expected to be augmented to list other protocol names."; leaf name { type enumeration { enum netconf { description "NETCONF protocol described in RFC 6241"; } enum restconf { description "RESTCONF protocol described in RFC 8040"; } } description "Name of the YANG-based protocol that is supported."; } // end of name leaf protocol-version { type string; description "Version of the specific protocol."; } leaf-list capabilities { type string; description "Listed name of capabilities that are supported by the specific device."; } } // end of protocol } // end of protocols container modules { description "Container holding list of modules."; list module { key "name revision"; description "List of references to YANG modules under specific vendor, platform, software-version, software-flavor. Using these references, the complete set of metadata can be retrieved for each module."; leaf name { type leafref { path "../../../../../../../../../../../modules/module/name"; } description "Reference to a name of the module that is contained in specific vendor, platform, software-version, software-flavor."; } leaf revision { type leafref { path "../../../../../../../../../../../modules/module/revision"; } description "Reference to a revision of the module that is contained in specific vendor, platform, software-version, software-flavor."; } } // end of list module } // end of container modules } // end of software-flavor } // end of software-flavors } // end of software-version } // end of software-versions } // end of platform } // end of platforms } // end of vendor } // end of vendors } //end of catalog augment "/catalog/modules/module" { uses module-data; container implementations { description "Container holding lists of per-module implementation details."; list implementation{ key "vendor platform software-version software-flavor"; description "List of module implementations."; leaf vendor { type string; description "Organization that created this module."; } leaf platform { type string; description "Platform on which this module is implemented."; } leaf software-version { type string; description "Name of the version of software. With respect to most network device appliances, this will be the operating system version. But for other YANG module implementation, this would be a version of appliance software. Ultimately, this should correspond to a version string that will be recognizable by the consumers of the platform."; } leaf software-flavor { type string; description "A variation of a specific version where YANG model support may be different. Depending on the vendor, this could be a license, additional software component, or a feature set."; } leaf os-version { type string; description "Version of the operating system using this module. This is primarily useful if the software implementing the module is an application that requires a specific operating system."; } leaf feature-set { type string; description "An optional feature of the software that is required in order to implement this module. Some form of this must be incorporated in software-version or software-flavor, but can be broken out here for additional clarity."; } leaf os-type { type string; description "Type of the operating system using this module. This is primarily useful if the software implementing the module is an application that requires a specific operating system."; } } } description "This table augments the per-module metadata set and provides details about vendor implementations for each module."; } grouping module-data { leaf document-name { type string; description "The name of the document from which the module was extracted or taken; or that provides additional context about the module."; } leaf author-email { type string; description "Contact email of the author who created this module."; } leaf compilation-status { type enumeration { enum PASSED { value 0; description "In case that all compilers were able to compile this YANG module without any error/warning."; } enum PASSED-WITH-WARNINGS { value 1; description "In case that all compilers were able to compile this YANG module without any error, but at least one of them caught some warning."; } enum FAILED { value 2; description "In case that at least one of compilers found some error while compiling this YANG module."; } enum MISSING { value 3; description "In case that there is not sufficient information about compilation status."; } } description "Status of the module, whether it was possible to compile this YANG module or there are still some errors/warnings."; } leaf compilation-result { type string; description "Result of the compilation explaining specifically what error or warning occurred. This is not existing if compilation status is PASSED."; } leaf reference { type string; description "A string that is used to specify a textual cross-reference to an external document, either another module that defines related management information, or a document that provides additional information relevant to this definition."; } leaf prefix { type string; description "Statement of yang that is used to define the prefix associated with the module and its namespace. The prefix statement's argument is the prefix string that is used as a prefix to access a module. The prefix string MAY be used to refer to definitions contained in the module, e.g., if:ifName."; } leaf yang-version { type string; default "1.0"; description "The optional yang-version statement specifies which version of the YANG language was used in developing the module. The statement's argument is a string. If present, it MUST contain the value 1, which is the current YANG version and the default value."; } leaf organization { type string; description "This statement defines the party responsible for this module. The argument is a string that is used to specify a textual description of the organization(s) under whose auspices this module was developed."; } leaf description { type string; description "This statement takes as an argument a string that contains a human-readable textual description of this definition. The text is provided in a language (or languages) chosen by the module developer; for the sake of interoperability, it is RECOMMENDED to choose a language that is widely understood among the community of network administrators who will use the module."; } leaf contact { type string; description "This statement provides contact information for the module. The argument is a string that is used to specify contact information for the person or persons to whom technical queries concerning this module should be sent, such as their name, postal address, telephone number, and electronic mail address."; } leaf module-type { type enumeration { enum module { value 0; description "If YANG file contains module."; } enum submodule { value 1; description "If YANG file contains sub-module."; } } description "Whether a file contains a YANG module or sub-module."; } leaf maturity-level { type enumeration { enum ratified { value 0; description "Maturity of a module that is fully approved (e.g., a standard)."; } enum working-group { value 1; description "Maturity of a module that is actively being developed by a organization towards ratification."; } enum individual { value 2; description "Maturity of a module that has been initially created, but has no official organization-level status."; } } description "The current maturity of the module with respect to the body that created it. This allows one to understand where the module is in its overall life cycle."; } description "Grouping of YANG module metadata that extends the common list defined in the YANG Module Library (RFC 7895)."; } } ]]>

The goal of the YANG Catalog module and yangcatalog.org is to document a large library of YANG modules and their implementations. Already, we have seen some SDOs hestitant to provide modules that have not reached a "ratified" maturity level because of intellectual property leakage concerns or simply organization process that mandates only fully ratified modules can be published. Care must be paid that through private automated testing and validation of such modules that their metadata does not leak before the publishing organization approves the release of such data. Similarly, from a vendor implementation standpoint, data that is exposed to the catalog before the vendor has fully vetted it could cause confusion amongst that vendor's customers or reveal product releases to the market before they have been officially announced. Ultimately, there is a balance to be struck with respect to providing a rich library of YANG module metadata, and doing so at the right time to avoid information leakage.

No action.

&RFC6020; &RFC7895; &RFC7950; &OPENCONFIG-YANG-CATALOG; &NETMOD-REVISED-DATASTORES;

The authors would like to thanks Miroslav Kovac for this help on this YANG module and the yangcatalog.org implementation. The RFC text was produced using Marshall Rose's xml2rfc tool.

Contributors' Addresses TBD