Support of Versioning in YANG Notifications Subscription

In order to process the received YANG push notification messages described in section 3.7 of at the YANG push receiver, a semantic reference to the YANG module and the XPath or subtree is needed to determine the data types for each field and which part of the YANG module the metrics are expose from. This specification applies to the YANG push configured subscriptions defined in Section 2.5 of , where a publisher is configured to stream notification out of band, as opposed to dynamic subscriptions defined in Section 2.4 of , where the subscriber can initiate and modify the subscription dynamically in-band. In the latter case, the subscriber knows already all the subscriber YANG-related information, which it has to know in order to configure the subscription. This semantic reference is available during the subscription period described in Section 3.6 of where for each subscription a locally unique subscription ID described in Section 4.3.2 of is being issued and streamed as metadata with the notification message in the YANG push message header. This implies that the YANG receiver needs to lookup the subscription inventory for a subscription ID in each notification message to determine the YANG module name, namespace, and filter definitions. The semantics can change between different YANG module revisions. The YANG module version statement is specified in Section 7.1.2 of and states that the newer revision needs to be backward compatible to the previous revision. Section 3.1 of specifies that newer semantic versions introduced in MAY not be backward compatible to the previous version when indicated with non-backwards-compatible keyword. The YANG notifications subscription mechanism defined in does not allow to specify the YANG module revision. When a network node is upgraded, the subscribed YANG module revision MAY have updated and might, consequently, break the data processing pipeline since the YANG push receiver may not be aware of this change. This documents extends the current YANG notifications subscription mechanism to allow to subscribe to a specific revision or latest semantic version to which the YANG module version needs to be backward compatible to and advertises its specific YANG module revision inband. Besides the existing Subscription ID, the YANG module name, namespace, revision and filtering metadata is added to the YANG push notification header to lift the YANG push receiver need to lookup the subscription inventory information.

The YANG notifications subscription OPTIONALLY can be restricted to the following YANG module revision for future capabilities:

latest:: Restricts the subscription to the latest YANG module revision.

revision:: Restricts the subscription to a specific YANG module revision. Example 2014-05-08.

latest-compatible-semversion:: Restricts the subscription to the latest compatible YANG module semantic version referenced to. Example 2.0.0.

If nothing is specified, latest YANG module version is implied.

Along with the subscribed content, besides the Subcription ID, the following metadata objects are part of a "push-update" or "push-change-update" notification.

module:: Describes the YANG module name for the related streamed content.

namespace:: Describes the YANG module namespace as specified in Section 7.1.3 of for the related streamed content.

revision:: Describes the YANG module revision as specified in Section 7.1.2 of for the related streamed content.

revision-label:: Describes the YANG module semantic version as specified in for the related streamed content.

datastore-xpath-filter:: Describes the YANG module xpath filter as specified in Section 6.4 of for the related streamed content.

datastore-subtree-filter:: Describes the YANG module subtree filter as specified in Section 6 of for the related streamed content.

Figure 1 provides an example of a notification message with the YANG module name, revision, revision label and datastore-xpath-filter for a subscription tracking the operational status of a single Ethernet interface (per ). This notification message is encoded XML over the Network Configuration Protocol (NETCONF) as per .

2022-09-02T10:59:55.32Z 101 ietf-interfaces urn:ietf:params:xml:ns:yang:ietf-interfaces 2014-05-08

1.0.0

ietf-interfaces:interfaces

eth0

Figure 1: XML Push Example for a Periodical Notification Message ]]> Figure 2 provides an example of a JSON encoded, , notification message over HTTPS-based or UDP-based transport for the same subscription.

This YANG module augments the "ietf-yang-push" module to add subcription metadata into the "push-update" and "push-change-update" notification and the ability to define the "revision" and "revision-label" in the "establish-subscription" and "modify-subscription" in the datastore push subscription.

{sn:subtree}? augment /yp:push-change-update: +--ro module? string +--ro namespace? string +--ro revision? rev:revision-date-or-label +--ro revision-label? ysver:version +--ro datastore-xpath-filter? yang:xpath1.0 {sn:xpath}? +--ro datastore-subtree-filter? {sn:subtree}? augment /sn:establish-subscription/sn:input/sn:target: +-- revision? rev:revision-date-or-label +-- revision-label? ysver:version augment /sn:modify-subscription/sn:input/sn:target: +-- revision? rev:revision-date-or-label +-- revision-label? ysver:version augment /sn:subscription-started/sn:target: +-- revision? rev:revision-date-or-label +-- revision-label? ysver:version augment /sn:subscription-modified/sn:target: +-- revision? rev:revision-date-or-label +-- revision-label? ysver:version augment /sn:subscriptions/sn:subscription/sn:target: +--rw revision? rev:revision-date-or-label +--rw revision-label? ysver:version ]]>

The YANG module has six leaves augmenting the model of YANG-push.

file "ietf-yang-push-metadata@2022-10-10.yang" module ietf-yang-push-metadata { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-push-metadata"; prefix ypm; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-subscribed-notifications { prefix sn; reference "RFC 8639: Subscription to YANG Notifications"; } import ietf-yang-push { prefix yp; reference "RFC 8641: Subscription to YANG Notifications for Datastore Updates"; } import ietf-yang-revisions { prefix rev; reference "RFC XXXX: draft-ietf-netmod-yang-module-versioning-06, Updated YANG Module Revision Handling"; } import ietf-yang-semver { prefix ysver; reference "RFC XXXX: draft-ietf-netmod-yang-semver-07, YANG Semantic Versioning"; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: Authors: Thomas Graf Benoit Claise Alex Huang Feng "; description "Defines YANG push event notification header with metadata. 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; see the RFC itself for full legal notices."; revision 2022-09-21 { description "First revision"; reference "RFC XXXX: Support of Versioning in YANG Notifications Subscription"; } feature yang-push-metadata-supported { description "This feature indicates the YANG Notifications have the metadata defined in this YANG module."; } grouping yang-push-module-version { leaf revision { type rev:revision-date-or-label; description "This references the YANG module revision of the sent notification."; } leaf revision-label { type ysver:version; description "This references the YANG module semversion of the sent notification."; } } grouping yang-push-metadata { leaf module { type string; description "This references the YANG module of the sent notification."; } leaf namespace { type string; description "This references the YANG module namespace of the sent notification."; } uses ypm:yang-push-module-version; leaf datastore-xpath-filter { type yang:xpath1.0; if-feature "sn:xpath"; description "This references the YANG module xpath of the sent notification."; } anydata datastore-subtree-filter { if-feature "sn:subtree"; description "This references the YANG module subtree of the sent notification."; } } // Event notifications augment "/yp:push-update" { description "This augmentation adds the module, the namespace, the revision, the semversion, the xpath and the subtree in the push-update notification"; uses ypm:yang-push-metadata; } augment "/yp:push-change-update" { description "This augmentation adds the module, the namespace, the revision, the semversion, the xpath and the subtree in the push-change-update notification"; uses ypm:yang-push-metadata; } // Subscription parameters augment "/sn:establish-subscription/sn:input/sn:target" { uses ypm:yang-push-module-version; } augment "/sn:modify-subscription/sn:input/sn:target" { uses ypm:yang-push-module-version; } // Subscription notifications augment "/sn:subscription-started/sn:target" { uses ypm:yang-push-module-version; } augment "/sn:subscription-modified/sn:target" { uses ypm:yang-push-module-version; } // Subscription container augment "/sn:subscriptions/sn:subscription/sn:target" { uses ypm:yang-push-module-version; } } ]]>



    
      The security considerations for the YANG notifications subscription
      mechanism are described in . This documents adds
      no additional security considerations.
    

    
      This document has no IANA actions.
    

    
      The authors would like to thank xxx for their review and valuable
      comments.