YANG-Push Notification Capabilities

YANG-Push Notification Capabilities Ericsson

Magyar Tudosok korutja 11 1117 Budapest Hungary balazs.lengyel@ericsson.com

Futurewei

2330 Central Expressway Santa Clara, CA 95050 USA ludwig@clemm.org

Cisco Systems, Inc.

De Kleetlaan 6a b1 1831 Diegem Belgium bclaise@cisco.com

OPS NETCONF This document proposes a YANG module that allows a publisher to specify capabilities related to "Subscription to YANG Datastores" (YANG-Push). It proposes to use YANG Instance Data to document this information and make it already available at implementation-time, but also allow it to be reported at run-time.

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 terms YANG-Push, On-change subscription and Periodic subscription are used as defined in The terms Subscriber, Publisher and Receiver are used as defined in The term Server is used as defined in On-change Notification Capability: The capability of the publisher to send on-change notifications for a specific datastore or a specific data node. Implementation-time information: Information about the publisher's behavior that is made available during the implementation of the publisher, available from a source other then a running server implementing the publisher. Run-time information: Information about the publisher's behavior that is available from the running server (implementing the publisher) via management protocols such as NETCONF or RESTCONF .

As defined in a publisher may allow subscribers to subscribe to updates from a datastore and subsequently push such update notifications to the receiver. Notifications may be sent periodically or on-change (more or less immediately after each change). A publisher supporting YANG-Push has a number of capabilities defined in that are often determined during the implementation of the publisher. These include: Supported (reporting) periods for periodic subscriptions Maximum number of objects that can be sent in an update The set of datastores or data nodes for which periodic notification is supported If the optional on-change feature is supported, additionally: Supported dampening periods for on-change subscriptions The set of datastores or data nodes for which on-change notification is supported Publishers have limitations in how many update notifications and how many datastore node updates they can send out in a certain time-period. Publishers might not support periodic subscriptions to all datastores. In some cases, a publisher supporting on-change notifications will not be able to push updates for some object types on-change. Reasons for this might be that the value of the datastore node changes frequently (e.g. in-octets counter), that small object changes are frequent and irrelevant to the receiver (e.g., a temperature gauge changing 0.1 degrees within a predetermined and acceptable range), or that the implementation is not capable of on-change notification for a particular object. In those cases, it will be important for subscriber applications to have a way to identify which objects on-change notifications are supported and for which ones not. Faced with the reality that support for on-change notification does not mean that such notifications will be sent for any specific data node, subscriber/management applications can not rely on the on-change functionality unless the subscriber has some means to identify which objects on-change notifications are supported. YANG models are meant to be used as an interface contract. Without identification of the data nodes actually supporting on-change, this contract would be incomplete. This document proposes a YANG module that allows a subscriber to discover YANG-Push related capabilities both at implementation-time and run-time. Implementation-time information is needed by Network Management System (NMS) implementers. A NMS implementation that wants to support notifications, needs the information about on-change notification capability. If the information is not documented in a way available to the NMS designer, but only as instance data from the network node once it is deployed, the NMS implementation will be delayed, because it has to wait for the network node to be ready. In addition, the assumption that all NMS implementers will have a correctly configured network node available to retrieve data from is an expensive proposition and may not always hold. (An NMS may need to be able to handle many dozens of network node types.) Often a fully functional NMS is a requirement for introducing a new network node type into a network, so delaying NMS readiness effectively also delays the time at which a new network node type can be introduced into the network. Implementation-time information is needed by system integrators. When introducing a network node type into their network, operators often need to integrate the node type into their own management system. The NMS may have management functions that depend on on-change notifications. The network operator needs to plan his management practices and NMS implementation before he even decides to buy the specific network node type. Moreover the decision to buy the node type sometimes depends on these management possibilities. Run-time information is needed: for any "purely model driven" application, e.g. a NETCONF-browser. Such applications depend on reading models, capabilities in run-time to support all the publisher's available functionality. in case the capability might change during run-time e.g. due to licensing, HW constraints etc. to check that capability information provided early, already in implementation-time is indeed what the publisher implements (is the supplied documentation correct?)

It is a goal to provide YANG-Push notification capability information in a format that is: vendor independent machine readable identical for implementation-time and run-time The YANG module ietf-notification-capabilities is defined to provide the information. It contains: a set of capabilities related to the throughput of notification data the publisher can send out. specification of which data nodes support on-change notifications. Capability values can be specified on publisher level, datastore level or on specific data nodes (and their contained sub-tree) of a specific datastore. Capability values on a smaller, more specific part of the publisher's data always override more generic values. Note: The solution is usable for both NMDA and non-NMDA systems. For non-NMDA servers/publishers the config=false data is considered as if it was part of the running datastore. The information SHOULD be provided in two ways both following the ietf-notification-capabilities module: For the implementation-time use-case: It SHOULD be provided by the implementer as YANG instance data file complying to . The file SHALL be available already in implementation-time retrievable in a way that does not depend on a live network node. E.g. download from product website. For the run-time use-case: It SHOULD be available via NETCONF or RESTCONF from the live server (implementing the publisher) during run-time. Implementations which support changing these capabilities at run-time SHOULD support on-change notifications about the publisher-subscription-capabilities container.

The following tree diagram provides an overview of the data model.

/yanglib:yang-library/datastore/name +--ro per-node-capabilities* [node-selector] +--ro node-selector nacm:node-instance-identifier +--ro (update-period)? | +--:(minimum-update-period) | | +--ro minimum-update-period? uint32 | +--:(supported-update-period) | +--ro supported-update-period* uint32 +--ro max-objects-per-update? uint32 +--ro minimum-dampening-period? uint32 | {yp:on-change}? +--ro on-change-supported? notification-support | {yp:on-change}? +--ro periodic-notifications-supported? notification-support +--ro supported-excluded-change-type* union {yp:on-change}? ]]>

<CODE BEGINS> file "ietf-notification-capabilities@2019-11-05.yang"

WG List: Editor: Balazs Lengyel "; description "This module specifies YANG-Push related publisher capabilities. The module contains - capabilities related to the throughput of notification data the publisher can support. (Note that for a specific subscription the publisher MAY still allow only longer periods or smaller updates depending on e.g. actual load conditions.) - specification of which data nodes support on-change or periodic notifications. Capability values can be specified on publisher level, datastore level or on specific data nodes (and their contained sub-tree) of a specific datastore. If a capability is specified on multiple levels, the specification on a more specific level overrides more generic capability specifications; thus - a publisher level specification is overridden by any other specification - a datastore level specification (with a node-selector '/') is overridden by a specification with a more specific node-selector. - a specification for a specific datastore and node-selector is overridden by a specification for the same datastore with a node-slector that describes more levels of containing lists and containers. If, different data nodes covered by a single subscription have different values for a specific capability, then using values that are only acceptable for some of these data nodes, but not for others, may result in the rejection of the subscription. To find a capability value for a specific node in a specific datastore the user SHALL 1) consider the publisher level capabilities under the publisher-subscription-capabilities container if the capability value is specified. 2) search for a datastore-capabilities list entry for the specific datastore. 3) within that datastore entry search for a per-node-capabilities entry that specifies the specific capability and that has the node-selector selecting the specific data node and that specifies the most levels of containing containers and lists. 4) If no entries are found in the previous steps the publisher is not capable of providing a value because it is unknown, the capability is changing for some reason, there is no specified limit etc. In this case the publisher's behavior is unspecified. 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. Copyright (c) 2019 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 (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; revision 2019-11-05 { description "Initial version"; reference "RFC XXX: YANG-Push Notification Capabilities"; } grouping subscription-capabilities { description "Capabilities related to Yang-Push notifications"; typedef notification-support { type enumeration { enum no-notifications-supported { description "The publisher is not capable of sending any notifications for the relevant scope and subscription type." ; } enum notifications-for-config-changes-supported { description "The publisher is capable of sending notifications for config=true nodes, but not for config=false nodes for the relevant scope and subscription type." ; } enum notifications-for-state-changes-supported { description "The publisher is capable of sending notifications for config=false nodes, but not for config=true nodes for the relevant scope and subscription type." ; } enum notifications-for-all-changes-supported { description "The publisher is capable of sending notifications for both config=false and config=true nodes for the relevant scope and subscription type." ; } } description "Type for defining whether on-change or periodic notifications are supported for no, only config=true, only config=false or all data nodes."; } choice update-period { description "Supported update period value or values for periodic subscriptions."; leaf minimum-update-period { type uint32; units "centiseconds"; description "Indicates the minimal update period that is supported for a periodic subscription. A periodic subscription to the selected data nodes must specify a value that is at least as large or greater than this"; reference "The period leaf in RFC 8641 ietf-yang-push YANG module"; } leaf-list supported-update-period { type uint32; units "centiseconds"; description "Supported update period values for a periodic subscription. A periodic subscription to the selected data nodes must specify one of the values in the list; other values are not supported."; reference "The period leaf in RFC 8641 ietf-yang-push YANG module"; } } leaf max-objects-per-update { type uint32 { range "1..max"; } description "Maximum number of objects that can be sent in an update for the selected data nodes."; } leaf minimum-dampening-period { if-feature yp:on-change; type uint32; units "centiseconds"; description "The minimum dampening period supported for on-change subscriptions for the selected data nodes."; } leaf on-change-supported { if-feature yp:on-change; type notification-support; description "Specifies whether the publisher is capable of sending on-change notifications for the selected data store or data nodes and the subtree below them."; } leaf periodic-notifications-supported { type notification-support; description "Specifies whether the publisher is capable of sending periodic notifications for the selected data store or data nodes and the subtree below them."; } leaf-list supported-excluded-change-type { if-feature yp:on-change; type union { type enumeration { enum none { description "None of the change types can be excluded."; } enum all { description "Any combination of change types can be excluded."; } } type yp:change-type; } description "The change types that can be excluded in YANG-Push subscriptions."; } } container publisher-subscription-capabilities { config false; description "YANG-Push related publisher capabilities. Capability values specified here at the publisher level are valid for all datastores and are used when the capability is not specified on the datastore level or for specific data nodes. "; uses subscription-capabilities { refine supported-excluded-change-type { default none; } } list datastore-capabilities { key datastore; description "Capabilities values per datastore. For non-NMDA servers/publishers the config=false data is considered as if it was part of the running datastore."; leaf datastore { type leafref { path /yanglib:yang-library/yanglib:datastore/yanglib:name; } description "The datastore for which capabilities are defined. Only individual datastores can be specified e.g. ds:conventional is not allowed."; } list per-node-capabilities { key "node-selector"; description "Each list entry specifies notification capabilities for the selected data nodes. The same capabilities apply for the data nodes in the subtree below them unless another list entry with a more specific node selector is present."; leaf node-selector { type nacm:node-instance-identifier; description "Selects the data nodes for which capabilities are specified. The special value '/' denotes all data nodes in the datastore. The system SHOULD order list entries according to the tree structure of the data models to make reading/parsing the data model more simple."; } uses subscription-capabilities; } } } } ]]> <CODE ENDS>

The YANG module specified in this document defines a 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) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. All protocol-accessible data nodes are read-only and cannot be modified. The data in this module is not security sensitive. Access control may be configured, to avoid exposing the read-only data. When that data is in file format, data should be protected against modification or unauthorized access using normal file handling mechanisms.

This document registers one URI in the IETF XML registry . Following the format in , the following registrations are requested:

URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.

This document registers one YANG module in the YANG Module Names registry . Following the format in , the the following registrations are requested:

name: ietf-notification-capabilities namespace: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities prefix: inc reference: RFC XXXX

The following example is instance-data describing the notification capabilities of a hypothetical "acme-switch". The switch implements the running, candidate and operational datastores. Every change can be reported on-change from running, nothing from candidate and all config=false data from operational. Periodic subscriptions are supported for running and operational, but not for candidate.

acme-switch-notification-capabilities ietf-notification-capabilities@2019-10-22.yang Notification capabilities of acme-switch. Acme-switch implements the running, candidate and operational datastores. Every change can be reported on-change from running, nothing from candidate and all config=false data from operational. Periodic subscriptions are supported for running and operational, but not for candidate.

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