Self-Describing Data Object Tags in YANG Data Models

Self-Describing Data Object Tags in YANG Data Models Huawei

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Huawei

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China Mobile

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China Mobile

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Orange

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OPS Area NETMOD Working Group This document defines a method to tag data objects that are associated with operation and management data in YANG modules. This method for tagging YANG data objects is meant to be used for classifying data objects from different YANG modules and identifying their characteristics data. Tags may be registered as well as assigned during the module definition, assigned by implementations, or dynamically defined and set by users. This document also provides guidance to future YANG data model writers; as such, this document updates RFC 8407.

The use of tags for classification and organization purposes is fairly ubiquitous, not only within IETF protocols, but globally in the Internet (e.g., "#hashtags"). For the specific case of YANG data models, a module tag is defined as a string that is associated with a module name at the module level . Many data models have been specified by various Standards Developing Organizations (SDOs) and the Open Source community, and it is likely that many more will be specified. These models cover many of the networking protocols and techniques. However, the data objects defined by these technology-specific data models might represent a portion of fault, configuration, accounting, performance, and security (FCAPS) management information () at different levels and network locations, but also categorised in various different ways. Furthermore, there is no consistent classification criteria or representation for a specific service, feature, or data source. This document defines self-describing data object tags and associates them with data objects within a YANG module, which: Provide dictionary meaning for specific targeted data objects. Indicate a relationship between data objects within the same YANG module or from different YANG modules. Identify key performance metric data objects and the absolute XPath expression identifying the element path to the node. The self-describing data object tags can be used by the NETCONF or RESTCONF client to classify data objects from different YANG modules and identify characteristic data. In addition, these tags can provide input, instructions, or indications to selection filters and filter queries of configuration or operational state on a server based on these data object tags (e.g., return specific objects containing operational state related to system-management). NETCONF clients can discover data objects with self-describing data object tags supported by a NETCONF server by means of the <get-schema> operation (Section 3.1 of ). The self-describing data object tag capability can also be advertised using the capability notification model by the NETCONF server or some websites where offline documents are kept. Similar to YANG module tags defined in , these data object tags may be registered or assigned during the module definition, assigned by implementations, or dynamically defined and set by users. This document defines a YANG module that augments the module tag model and provides a list of data object entries to add or remove self-describing tags as well as to view the set of self-describing tags associated with specific data objects within YANG modules. This document defines three extension statements to indicate self-describing tags that should be added by the module implementation automatically (i.e., outside of configuration). This document also defines an IANA registry for tag prefixes and a set of globally assigned tags (). provides guidelines for authors of YANG data models. This document updates . The YANG data model in this document conforms to the Network Management Datastore Architecture defined in .

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. The meanings of the symbols in tree diagrams are defined in .

Among data object tags, the 'opm' (object, property, metric) tags can be used to tackle massive data object collections, indicate relationships between data objects, and capture YANG data objects associated with YANG-modelled performance metrics data. An example is depicted in .

.------. |Object| | Tag | '--+--' | +---------V--------+ contain | YANG Data Node <----------------+ | /Data Object 1 | | +--^-------------^-+ | |contain |contain | | | | +-----------+---+ +- -----+-------+ +-----+---------+ | YANG Data Node| | YANG Data Node| | YANG Data Node| |/Sub Object 2 | | /Sub Object 3 | | /Sub Object 4 | +--^------------+ +^-----^--------+ +^-----^------^-+ | | | | | | .---+---. | .--+--. | .--+--. | |Property | | |Metric | | |Metric | | | Tag | | | Tag | | | Tag | | '---------' | '-------' | '-------' | | | | .--+--. .--+--. .---+---. |Metric | |Metric | || Multi || | Type | | Type | ||Metric || | Tag | | Tag | ||Source || '-------' '-------' \\ Tag // '-----' In , data objects can contain other data objects called 'subobjects'. Both object and subobjects can be modeled as YANG data nodes . Data objects that contain other data objects can be one of type 'container', 'leaf-list', or 'list' and are tagged with the object tag. A subobject tagged with the property tag is a 'leaf' node. Subobjects tagged with the metric tag can be one of 'container', 'leaf-list', 'list', or 'leaf' data node. A data object may contain one single object tag, or one single property tag, or one single metric tag. The data object tagged with the metric tag also can have one or multiple Metric Type tags and/or one single multi-source tag. The use of 'opm' tags is meant to help filter discrete categories of YANG data objects scattered across the same or different YANG modules that are supported by a device and capture all network performance data or all property data in a single view of the data. In the example shown in , the 'tunnel-svc' data object is a container node defined in a 'tunnel-pm' module and can be seen as the root object for property tagged subobjects (e.g., 'tunnel-svc'/'create-time') and metric tagged subobjects (e.g., 'tunnel-svc'/'avg-latency'). The 'name', 'create-time', and 'modified-time' are property tagged subobjects under 'tunnel-svc' container. The 'avg-latency' and 'packet-loss' metrics are tagged subobjects under 'tunnel-svc' container node. Consider the 'tunnel-svc' data object and the 'tunnel-svc/name' data object as an example: the 'tunnel-svc' data object has one single object tag (i.e., 'ietf:object'), while the 'tunnel-svc/name' data object has one single property subobject tag (i.e., 'ietf:property'). In addition, not all metric subobjects need to be tagged (e.g., define specific categories, such as loss-related metric subobjects need to be tagged with a metric-type tag which can further reduce amount data to be fetched).

All data object tags SHOULD begin with a prefix indicating who owns their definition. An IANA registry () is used to register data object tag prefixes. Initially, three prefixes are defined. No further structure is imposed by this document on the value following the registered prefix, and the value can contain any YANG type 'string' characters except carriage returns, newlines, tabs, and spaces. Except for the conflict-avoiding prefix, this document is purposefully not specifying any structure on (i.e., restricting) the tag values. The intent is to avoid arbitrarily restricting the values that designers, implementers, and users can use. As a result of this choice, designers, implementers, and users are free to add or not add any structure they may require to their own tag values.

An IETF tag is a data object tag that has the prefix "ietf:". All IETF data object tags are registered with IANA in the registry defined in .

A vendor tag is a tag that has the prefix "vendor:". These tags are defined by the vendor that implements the module, and are not registered with IANA. However, it is RECOMMENDED that the vendor includes extra identification in the tag to avoid collisions, such as using the enterprise or organization name following the "vendor:" prefix (e.g., vendor:example.com:vendor-defined-classifier).

A user tag is any tag that has the prefix "user:". For the avoidance of confusion, the colon (":") when it appears for the first time, is always assumed to be the separator between a prefix and the rest of the tag. And so, when a user tag does not have a prefix, it MUST NOT contain a colon. These tags are defined by a user/administrator and are not meant to be registered with IANA. Users are not required to use the "user:" prefix; however, doing so is RECOMMENDED as it helps avoid collisions.

Any tag not starting with the prefix "ietf:", "vendor:", or "user:" is reserved for future use (). These tag values are not invalid, but simply reserved in the context of specifications (e.g., RFCs).

Tags may be associated with a data object within a YANG module in a number of ways. Typically, tags may be defined and associated at the module design time, at implementation time without the need of a live server, or via user administrative control. As the main consumers of data object tags are users, users may also remove any tag from a live server, no matter how the tag became associated with a data object within a YANG module.

A data object definition MAY indicate a set of data object tags to be added by a module's implementer. These design time tags are indicated using a set of extension statements which include: Classifies management and operation data into object, property subobject, and metric subobject categories. Both objects and subobjects can be modeled as YANG data nodes . Data objects that contain other data objects can be one of type 'container', 'leaf-list', and 'list' and are tagged with object tag. A subobject tagged with the property tag is a 'leaf' node. Subobjects tagged with the metric tag can be one of 'container', 'leaf-list', 'list', or 'leaf' data node. A data object contains one single object tag, one single property tag, or one single metric tag. A data object tagged with metric tag also can have one or multiple Metric type tag and/or one single multi-source tag. See the examples depicted in and . Provides metric data objects classifications (e.g., loss, jitter, delay, counter, gauge, summary, unknown) within the YANG module. Identifies multi-source aggregation type (e.g., aggregated, non-aggregated) related to a metric subobject. The 'aggregated' multi-source aggregation type allows a large number of measurements on metric subobjects from different sources of the same type (e.g., line card, each subinterface of aggregated Ethernet interface) to be combined into aggregated statistics and report as one metric subobject. The 'non-aggregated' multi-source aggregation type allows measurement from each source of the same type (e.g., line card, each subinterface of aggregated Ethernet interface) to be reported separately. Among these extension statements, the 'metric-type' and 'multi-source' tag extension statements are context information that can be used to correlate data objects from the different modules. If the data node is defined in an IETF Standards Track document, the data object tags MUST be IETF Tags (). Thus, new data objects can drive the addition of new IETF tags to the IANA registry defined in , and the IANA registry can serve as a check against duplication.

An implementation MAY include additional tags associated with data objects within a YANG module. These tags SHOULD be IETF () or vendor tags ().

Data object tags of any kind, with or without a prefix, can be assigned and removed by the user from a server using normal configuration mechanisms. In order to remove a data object tag from the operational datastore, the user adds a matching "masked-tag" entry for a given data object within the 'ietf-data-object-tags' module.

The tree associated with the "ietf-data-object-tags" module is as follows:

module: ietf-data-object-tags augment /tags:module-tags/tags:module: +--rw data-object-tags +--rw data-object* [name] +--rw name nacm:node-instance-identifier +--rw tag* tags:tag +--rw masked-tag* tags:tag

This module imports types from [RFC8819],[RFC8341].

<CODE BEGINS> file "ietf-data-object-tags@2022-02-04.yang" module ietf-data-object-tags { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-tags"; prefix ntags; import ietf-netconf-acm { prefix nacm; reference "RFC 8341: Network Configuration Access Control Model"; } import ietf-module-tags { prefix tags; reference "RFC 8819: YANG Module Tags "; } organization "IETF NetMod Working Group (NetMod)"; contact "WG Web: <https://datatracker.ietf.org/wg/netmod/> WG List: <mailto:netmod@ietf.org> Editor: Qin Wu <mailto:bill.wu@huawei.com> Editor: Benoit Claise <mailto:benoit.claise@huawei.com> Editor: Peng Liu <mailto:liupengyjy@chinamobile.com> Editor: Zongpeng Du <mailto:duzongpeng@chinamobile.com> Editor: Mohamed Boucadair <mailto:mohamed.boucadair@orange.com>"; description "This module describes a mechanism associating self-describing tags with YANG data object within YANG modules. Tags may be IANA assigned or privately defined. Copyright (c) 2022 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 (https://datatracker.ietf.org/html/rfcXXXX); see the RFC itself for full legal notices."; revision 2022-02-04 { description "Initial revision."; reference "RFC XXXX: Self-Describing Data Object Tags in YANG Data Models"; } extension opm-tag { argument tag; description "The argument 'tag' is of type 'tag'. This extension statement is used by module authors to indicate the opm tags that should be added automatically by the system. 'opm-tag' is used to classify operation and management data objects into the three categories, object, property, and metric. Data Object can contain other data objects called subobjects. Both object and subobjects can be modeled as data nodes. A data object tagged with object tag can be one of container, leaf-list, or list. A data object tagged is with the property tag is a leaf node. The data object tagged with the metric tag can be one of container, leaf-list, list, or leaf. A data objects tagged with either property tag or metric tag are subobjects belonging to a specific root data object. Each data object may contain one single object tag, or one single property tag, or one single metric tag (these tags are mutually exclusive). As such, the origin of the value for the pre-defined tags should be set to 'system'."; } extension metric-type { argument tag; description "The argument 'tag' is of type 'tag'. The metric type can be used to provide metric data object classification (e.g., loss, jitter, packet loss, counter, gauge, summary, unknown) within a YANG module."; } extension multi-source-tag { argument tag; description "The argument 'tag' is of type 'tag'. The multi-source-tag can be used to identify multi-source aggregation type (e.g., aggregated, non-aggregated) related to a metric subobject. The 'aggregated' multi-source aggregation type allows a large number of measurements on metric subobjects from different sources of the same type (e.g., line card, each subinterface of an aggregated Ethernet interface) to be combined into aggregated statistics and reported as one metric subobject value. The 'non-aggregated' multi-source aggregation type allows measurement from each source of the same type (e.g., line card, each subinterface of an aggregated Ethernet interface) to be reported separately."; } augment "/tags:module-tags/tags:module" { description "Augment the Module Tags module with data object tag attributes."; container data-object-tags { description "Contains the list of data objects and their associated data object tags."; list data-object { key "name"; description "Includes a list of data objects and their associated data object tags."; leaf name { type nacm:node-instance-identifier; mandatory true; description "The YANG data object name."; } leaf-list tag { type tags:tag; description "Lists the tags associated with the data object within the YANG module. See the IANA 'YANG Data Object Tag Prefixes' registry for reserved prefixes and the IANA 'IETF YANG Data Object Tags' registry for IETF tags. The 'operational' state view of this list is constructed using the following steps: 1) System tags (i.e., tags of 'system' origin) are added. 2) User configured tags (i.e., tags of 'intended' origin) are added. 3) Any tag that is equal to a masked-tag is removed."; reference "RFC XXXX: Self-Describing Data Object Tags in YANG Data Models, Section 9"; } leaf-list masked-tag { type tags:tag; description "The list of tags that should not be associated with the data object within the YANG module. The user can remove (mask) tags from the operational state datastore by adding them to this list. It is not an error to add tags to this list that are not associated with the data object within YANG module, but they have no operational effect."; } } } } } <CODE ENDS>

This section updates .

A module MAY indicate, using data object tag extension statements, a set of data object tags that are to be automatically associated with data object within the module (i.e., not added through configuration).

module example-module-A { //... import ietf-data-node-tags { prefix ntags; } container top { ntags:opm-tag "ietf:object"; list X { leaf foo { ntags:opm-tag "ietf:property"; } leaf bar { ntags:opm-tag "ietf:metric"; } } } // ... } The module writer can use existing standard data object tags, or use new data object tags defined in the data object definition, as appropriate. For IETF standardized modules, new data object tags MUST be assigned in the IANA registry defined in Section .

This document requests IANA to create "YANG Data Object Tag Prefixes" subregistry in "YANG Data Object Tag" registry. This registry allocates tag prefixes. All YANG Data Object Tags should begin with one of the prefixes in this registry. Prefix entries in this registry should be short strings consisting of lowercase ASCII alpha-numeric characters and a final ":" character. The allocation policy for this registry is Specification Required . The Reference and Assignee values should be sufficient to identify and contact the organization that has been allocated the prefix. There is no specific guidance for the Designated Expert and there is a presumption that a code point should be granted unless there is a compelling reason to the contrary. The initial values for this registry are as follows:

This document requests IANA to create "IETF OPM Tags","IETF Metric Type Tags","IETF Multiple Source Tags" three subregistries in "YANG Data Object Tag" registry. These 3 subregistries appear below "YANG Data Object Tag Prefixes" registry. Three subregistries allocate tags that have the registered prefix "ietf:". New values should be well considered and not achievable through a combination of already existing IETF tags. The allocation policy for these three subregistries is IETF Review . The Designated Expert is expected to verify that IANA assigned tags conform to Net-Unicode as defined in , and shall not need normalization. The initial values for these three subregistries are as follows:

This document registers the following namespace URI in the "ns" subregistry within the "IETF XML Registry" :

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

This document registers the following YANG module in the YANG Module Names registry within the "YANG Parameters" registry:

name: ietf-data-object-tags namespace: urn:ietf:params:xml:ns:yang:ietf-data-object-tags prefix: ntags reference: RFC XXXX maintained by IANA: N

The YANG module specified in this document defines schema for data that is designed to be accessed via network management protocols such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . 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, e.g., the presence of tags may reveal information about the way in which data objects are used and therefore providing access to private information or revealing an attack vector should be restricted. Note that appropriate privilege and security levels need to be applied to the addition and removal of user tags to ensure that a user receives the correct data. This document adds the ability to associate data object tag meta-data with data object within the YANG modules. This document does not define any actions based on these associations, and none are yet defined, and therefore it does not by itself introduce any new security considerations. Users of the data object tag meta-data may define various actions to be taken based on the data object tag meta-data. These actions and their definitions are outside the scope of this document. Users will need to consider the security implications of any actions they choose to define, including the potential for a tag to get 'masked' by another user.

The authors would like to thank Ran Tao for his major contributions to the initial modeling and use cases. The authors would also like to acknowledge the comments and suggestions received from Juergen Schoenwaelder, Andy Bierman, Lou Berger,Jaehoon Paul Jeong, Wei Wang, Yuan Zhang, Ander Liu, YingZhen Qu, Boyuan Yan, Adrian Farrel, and Mahesh Jethanandani.

Liang Geng China Mobile 32 Xuanwumen West St, Xicheng District Beijing 10053 Email: gengliang@chinamobile.com

X.700 : Management framework for Open Systems Interconnection (OSI) for CCITT applications

The following is a NETCONF example result from a query of the data object tags list. For the sake of brevity only a few module and associated data object results are provided. The example uses the folding defined in .

=============== NOTE: '\' line wrapping per RFC 8792 ================ <ns0:data xmlns:ns0="urn:ietf:params:xml:ns:netconf:base:1.0"> <t:module-tags xmlns:t="urn:ietf:params:xml:ns:yang:ietf-module-tags"> <t:module> <t:name>ietf-interfaces</t:name> <s:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf-\ data-object-tags"> <s:data-object> <s:name>/if:interfaces/if:interface</s:name> <s:tag>ietf:object</s:tag> </s:data-object> <s:data-object> <s:name>/if:interfaces/if:interface/if:last-change</\ s:name> <s:tag>ietf:property</s:tag> </s:data-object> <s:data-object> <s:name> /if:interfaces/if:interface/if:statistics/if:in-errors </s:name> <s:tag>ietf:metric</s:tag> <s:tag>ietf:loss</s:tag> <s:tag>ietf:non-agg</s:tag> </s:data-object> </s:data-object-tags> </t:module> <t:module> <t:name>ietf-ip</t:name> <s:data-object-tags xmlns:s="urn:ietf:params:xml:ns:yang:ietf\ -data-object-tags"> <s:data-object> <s:name>/if:interfaces/if:interface/ip:ipv4</s:name> <s:tag>ietf:object</s:tag> </s:data-object> <s:data-object> <s:name>/if:interfaces/if:interface/ip:ipv4/ip:enable\ </s:name> <s:tag>ietf:property</s:tag> </s:data-object> <s:data-object> <s:name>/if:interfaces/if:interface/ip:ipv4/ip:mtu</s:name> <s:tag>ietf:metric</s:tag> <s:tag>ietf:non-agg</s:tag> </s:data-object> </s:data-object-tags> </t:module> </t:module-tags> </ns0:data>

As per [RFC8407], the following is a non-NMDA module to support viewing the operational state for non-NMDA compliant servers.

<CODE BEGINS> file "ietf-data-object-tags-state@2022-02-03.yang" module ietf-data-object-tags-state { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-data-object-tags-state"; prefix ntags-s; import ietf-netconf-acm { prefix nacm; reference "RFC 8341: Network Configuration Access Control Model"; } import ietf-module-tags { prefix tags; reference "RFC 8819: YANG Module Tags "; } organization "IETF NetMod Working Group (NetMod)"; contact "WG Web: <https://datatracker.ietf.org/wg/netmod/> WG List:<mailto:netmod@ietf.org> Editor: Qin Wu <mailto:bill.wu@huawei.com> Editor: Benoit Claise <mailto:benoit.claise@huawei.com> Editor: Peng Liu <mailto:liupengyjy@chinamobile.com> Editor: Zongpeng Du <mailto:duzongpeng@chinamobile.com> Editor: Mohamed Boucadair <mailto:mohamed.boucadair@orange.com>"; description "This module describes a mechanism associating self-describing tags with YANG data object within YANG modules. Tags may be IANA assigned or privately defined. Copyright (c) 2022 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://datatracker.ietf.org/html/rfcXXXX); see the RFC itself for full legal notices."; revision 2022-02-04 { description "Initial revision."; reference "RFC XXXX: Self-Describing Data Object Tags in YANG Data Models"; } extension opm-tag { argument tag; description "The argument 'tag' is of type 'tag'. This extension statement is used by module authors to indicate the opm tags that should be added automatically by the system. 'opm-tag' is used to classify operation and management data objects into the three categories, object, property, and metric. Data Object can contain other data objects called subobjects. Both object and subobjects can be modeled as data nodes. The Data Object tagged with object tag can be one of container, leaf-list and list. The Data Object tagged with the Property tag is a leaf node. The Data Object tagged with the Metric tag can be one of type container, leaf-list, list, leaf. The Data objects tagged with either property tag or metric tag are subobjects belonging to a specific root data object. Each Data Object may contain one single object tag, or one single property tag, or one single metric tag (these tags are mutually exclusive). As such, the origin of the value for the pre-defined tags should be set to 'system'."; } extension metric-type { argument tag; description "The argument 'tag' is of type 'tag'.The metric-type can be used to provide metric subobject classification (e.g., loss, jitter, packet loss, guage, counter, histogram, unknow, etc.) within the YANG module."; } extension multi-source-tag { argument tag; description "The argument 'tag' is of type 'tag'. The multi-source tag can be used to identify multi-source aggregation type (e.g., aggregated, non-aggregated) related to a metric subobject. The 'aggregated' multi-source aggregation type allows a large number of measurements on metric subobjects from different sources of the same type (e.g., line card, each subinterface of aggregated Ethernet interface) to be combined into aggregated statistics and reported as one metric subobject value. The 'non-aggregated'multi-source aggregation type allows measurement from each source of the same type (e.g., line card, each subinterface of aggregated Ethernet interface) to be reported separately."; } augment "/tags:module-tags/tags:module" { description "Augments the Module Tags module with data object tag attributes."; container data-object-tags { config false; status deprecated; description "Contains the list of data objects and their associated self describing tags."; list data-object { key "name"; status deprecated; description "Lists the data objects and their associated self describing tags."; leaf name { type nacm:node-instance-identifier; mandatory true; status deprecated; description "The YANG data object name."; } leaf-list tag { type tags:tag; status deprecated; description "Tags associated with the data object within the YANG module. See the IANA 'YANG Data Object Tag Prefixes' registry for reserved prefixes and the IANA 'IETF YANG Data Object Tags'registry for IETF tags. The 'operational' state view of this list is constructed using the following steps: 1) System tags (i.e., tags of 'system' origin) are added. 2) User configured tags (i.e., tags of 'intended' origin) are added. 3) Any tag that is equal to a masked-tag is removed."; reference "RFC XXXX: Self-Describing Data Object Tags in YANG Data Models, Section 9"; } leaf-list masked-tag { type tags:tag; status deprecated; description "The list of tags that should not be associated with the data object within the YANG module. The user can remove (mask) tags from the operational state datastore by adding them to this list. It is not an error to add tags to this list that are not associated with the data object within YANG module, but they have no operational effect."; } } } } } <CODE ENDS>

The following provides targeted data object collection example which helps reduce amount of data to be fetched. The subscription "id" values of 22 used below is just an example. In production, the actual values of "id" might not be small integers.

+-----------+ +-----------+ | Subscriber| | Publisher | +-----+-----+ +-----+-----+ | | |Telemery data Tagging Advertisement | |(data object name, opm-tag = metric)| |<-----------------------------------+ | | | establish-subscription | +----------------------------------->| | | | RPC Reply: OK, id = 22 | |<-----------------------------------+ | | | Notification Message (for 22) | |<-----------------------------------+ | | The publisher advertises telemetry data object capability to the subscriber to instruct the receiver to subscribe tagged data object (e.g., performance metric data object) using standard subscribed notification mechanism [RFC8639]. The corresponding telemetry data object capability model is created based on ietf-data-object-tags module defined in this document. illustrates the advertisment of the list of available target objects using the YANG instance file format :

=============== NOTE: '\' line wrapping per RFC 8792 ================ <?xml version="1.0" encoding="UTF-8"?> <instance-data-set xmlns=\ "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data"> <name>acme-router-notification-capabilities</name> <content-schema> <module>ietf-system-capabilities@2020-03-23</module> <module>ietf-notification-capabilities@2020-03-23</module> <module>ietf-data-export-capabilities@2020-03-23</module> </content-schema>  <description>Defines the notification capabilities of an acme-router.The router only has running, and operational datastores. Every change can be reported on-change from running, but only config=true nodes and some config=false data from operational. Statistics are not reported based on timer based trigger and counter threshold based trigger. </description> <content-data> <system-capabilities \ xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \ xmlns:inc=\ "urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \ xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> <datastore-capabilities> <datastore>ds:operational</datastore> <per-node-capabilities> <node-selector>\ /if:interfaces/if:interface/if:statistics/if:in-errors\ </node-selector> <sec:self-describing-capabilities> <sec:opm-tag>metric</sec:opm-tag> <sec:metric-type>loss</sec:metric-type> </sec:self-describing-capabilities> </per-node-capabilities> </datastore-capabilities> </system-capabilities> </content-data> </instance-data-set> With telemetry data tagging information carried in the telemetry data tagging Advertisement, the subscriber identifies targeted data object and associated data path to the datastore node and sends a standard establish-subscription RPC to subscribe tagged data objects that are interests to the client application from the publisher. Alternatively, the subscriber can query data object tag list from somewhere (e.g., the network device, or offline document) using ietf-data-object-tags module defined in this document and fetch tagged data objects and associated data path to the datastore node and sends a standard establish-subscription RPC to subscribe tagged data objects that are interests to the client application from the publisher.

=============== NOTE: '\' line wrapping per RFC 8792 ================ <netconf:rpc message-id="101" xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0"> <establish-subscription xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifica\ tions" xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push"> <yp:datastore xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores"> ds:operational </yp:datastore> <yp:datastore-xpath-filter xmlns:ex="https://example.com/sample-data/1.0"> /if:interfaces/if:interface/if:statistics/if:in-errors </yp:datastore-xpath-filter> <yp:periodic> <yp:period>500</yp:period> </yp:periodic> </establish-subscription> </netconf:rpc> The publisher returns specific object types of operational state (e.g., in-errors statistics data) subscribed by the client.

Editorial Note (To be removed by RFC Editor) v05 - v06 Additional Editorial changes; Use the folding defined in [RFC8792]. v04 - v05 Add user tag formating clarification; Provide guidance to the Designated Expert for evaluation of YANG Data Object Tag registry and YANG Data Object Tag prefix registry. Update the figure 1 and figure 2 with additional tags. Security section enhancement for user tag managment. Change data object name into name in the module. Other Editorial changes to address Adrian's comments and comments during YANG docotor review. Open issue: Are there any risks associated with an attacker adding or removing tags so that a requester gets the wrong data? v03 - v04 Remove histogram metric type tag from metric type tags. Clarify the object tag and property tag,metric tag are mutual exlusive. Clarify to have two optional node tags (i.e.,object tag and property tag) to indicate relationship between data objects. Update targeted data object collection example. v02 - v03 Additional Editorial changes. Security section enhancement. Nits fixed. v01 - v02 Clarify the relation between data object, object tag, property tag and metric tag in figure 1 and figure 2 and related description; Change Metric Group into Metric Type in the YANG model; Add 5 metric types in section 7.2; v00 - v01 Merge self-describing data object tag use case section into introduction section as a subsection; Add one glossary section; Clarify the relation between data object, object tag, property tag and metric tag in Self-Describing Data Object Tags Use Case section; Add update to RFC8407 in the front page.