Support of Observation Timestamp in YANG-Push Notifications

To correlate network data among different Network Telemetry planes as described in Section 3.1 of or among different YANG-Push subscription types defined in Section 3.1 of , observation timestamp describes when the state change was observed or when the data was accounted. This is essential for understanding the timely relationship among these different planes and YANG push subscription types. With the delay between the YANG Notification export and the arrival at the downstream system storing the data can be measured. With observation timestamp described in this document, the delay between the time of the network observation and the data export of the YANG push publisher process can be measured as well, extending the delay measurement scope from the time the network observation and storing the data. When the time bucket length in a time series database and the periodical YANG push subscription time is identical, the eventTime of the netconf notification message header is used for indexing, there is variable delay between the observation timestamp and the eventTime, and the anchor-time as described in Section 4.2 of is close to the time bucket boundaries, a time bucket is going to have periodically 0 or 2 measurements indexed instead of 1. Leading to inconsistent accounting errors in the time series database. This problem is resolved by using the observation timestamp instead of the eventTime for time series database indexing. By extending YANG-Push Notifications with the observation timestamp YANG object and a point-in-time enumeration for streaming update YANG-Push notifications it is ensured that the observation timestamp is always present with the best available time, it can be therefore used unconditionally in the data processing chain and with the point-in-time enumeration there is semantic describing at which point in time the observation timestamp was observed.

The following terms are defined in and are not redefined here: Publisher Receiver Subscription In addition, this document defines the following terms: Timestamp: Describes when the metric(s) (reported in YANG-Push subscriptions) were observed for a given Subscription ID and notification message. Point-in-time: Describes at which point in time the metric(s) reported in YANG-Push subscriptions) were observed for a given Subscription ID and notification message.

Besides the Subscription ID as described in Section 3.7 of , the following network observation time metadata objects are part of "push-update" and "push-change-update" notifications.

timestamp:: States the measurement observation time for the "push-update" notification in a "periodical" and for the "push-change-update" notification in a "on-change" subscription. By comparing the observation timestamp of two "push-update" notifications in a periodical subscription, the collector can deduce the actual cadence of the measurements, and compare it with the subscription configuration. In case of an "on-change" subscription it states the time when the network state change was observed.
point-in-time:: The enumeration states at which point in time the value of the observation timestamp was observed. Choices are: current-accounting states for "periodical" subscriptions, the point-in-time where the metrics are being polled and observed. initial-state states for "on-change sync on start" subscriptions, the initial point in time when the subscription was established and the state was observed. state-changed states for "on-change" and "on-change sync on start" subscriptions, the point in time when the state change was observed after the subscription was established.

provides an example timeline of events to describe observation timestamp and point-in-time for "on-change sync on start" subscriptions. At "T2" when the "on-change sync on start" subscription is established, the timestamp of "T2" is used in observation timestamp and "point-in-time" is set to "initial-state". At "T3" and "T4" the timestamp of "T3" respectively "T4" is used in observation timestamp and point-in-time is set to "state-changed".

provides an example timeline of events to describe point-in-time for "periodical" subscriptions. The timestamp of observation timestamp in "T2" is set at the start of the polling of the YANG data store to "T2" and point-in-time is set "current-accounting". At "T3" the timestamp of observation timestamp of "T3" is used. At "T4" the timestamp of observation timestamp of "T4" is used.

YANG-related system capabilities can be discovered by subscribing to the datastore defined in . This document augments the "ietf-notification-capabilities" defined in so that the YANG-Push receiver can learn the capabilities defined in this documents through the datastore. The definition of this YANG augmentation is specified in .

This YANG module augments the "ietf-yang-push" module with the observation timestamp and point-in-time in the "push-update" and "push-change-update" streaming update notifications.

This "ietf-yp-observation" YANG module augments the "ietf-yang-push" YANG module specified in Section 5 of adding the "timestamp" and the "point-in-time" leaves and augments "ietf-notification-capabilities" defined in to add a system level capability.

The following YANG tree diagram shows the complete notification defined in the "ietf-yang-push" module:

| +--ro incomplete-update? empty | +--ro ypot:timestamp? yang:date-and-time | +--ro ypot:point-in-time? enumeration +---n push-change-update {on-change}? +--ro id? sn:subscription-id +--ro datastore-changes +--ro incomplete-update? empty +--ro ypot:timestamp? yang:date-and-time +--ro ypot:point-in-time? enumeration ]]> The following YANG tree diagram shows the complete "ietf-system-capabilities" module with the augmentations defined in "ietf-yp-observation" module:

/yanglib:yang-library/datastore/name | +--ro per-node-capabilities* [] | +--ro (node-selection)? | | +--:(node-selector) | | +--ro node-selector? | | nacm:node-instance-identifier | +--ro notc:subscription-capabilities | +--ro notc:max-nodes-per-update? uint32 | +--ro notc:periodic-notifications-supported? | | notification-support | +--ro (notc:update-period)? | | +--:(notc:minimum-update-period) | | | +--ro notc:minimum-update-period? uint32 | | +--:(notc:supported-update-period) | | +--ro notc:supported-update-period* uint32 | +--ro notc:on-change-supported? | | notification-support {yp:on-change}? | +--ro notc:minimum-dampening-period? uint32 | | {yp:on-change}? | +--ro notc:supported-excluded-change-type* union | {yp:on-change}? +--ro notc:subscription-capabilities +--ro notc:max-nodes-per-update? uint32 +--ro notc:periodic-notifications-supported? | notification-support +--ro (notc:update-period)? | +--:(notc:minimum-update-period) | | +--ro notc:minimum-update-period? uint32 | +--:(notc:supported-update-period) | +--ro notc:supported-update-period* uint32 +--ro notc:on-change-supported? | notification-support {yp:on-change}? +--ro notc:minimum-dampening-period? uint32 | {yp:on-change}? +--ro notc:supported-excluded-change-type* union | {yp:on-change}? +--ro inotifseq:sysname-sequence-supported? | notification-support {sysname-sequence}? +--ro ypot:yang-push-observation-supported? inotifseq:notification-support {yang-push-observation-timestamp}? ]]>

The YANG module has one leave augmenting the model of Subscription to YANG Notifications.

file "ietf-yp-observation@2024-06-18.yang" module ietf-yp-observation { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yp-observation"; prefix ypot; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-yang-push { prefix yp; reference "RFC 8641: Subscription to YANG Notifications for Datastore Updates"; } import ietf-system-capabilities { prefix sysc; reference "RFC 9196: YANG Modules Describing Capabilities for Systems and Datastore Update Notifications"; } import ietf-notification-capabilities { prefix notc; reference "RFC 9196: YANG Modules Describing Capabilities for Systems and Datastore Update Notifications"; } import ietf-notification-sequencing { prefix inotifseq; reference "draft-tgraf-netconf-notif-sequencing-05: YANG Notifications Sequencing"; } 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 the observation time in streaming update notifications. Copyright (c) 2024 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 2024-06-18 { description "First revision"; reference "RFC XXXX: Support of YANG-Push Notifications Observation Time"; } feature yang-push-observation-timestamp { description "This feature indicates the YANG-push Notifications support the observation timestamps in streaming update notifications."; } grouping yang-push-observation { description "This grouping adds the observation timestamp for the observed metrics."; leaf timestamp { type yang:date-and-time; description "This is the time when metrics were observed."; } leaf point-in-time { type enumeration { enum current-accounting { description "For periodical subscriptions, the point-in-time where the metrics are being polled and observed."; } enum initial-state { description "For 'on-change sync on start' subscriptions, the initial point in time when the subscription was established and the state was observed."; } enum state-changed { description "For 'on-change sync on start' subscriptions, the point in time when the state change was observed after the subscription was established."; } } description "This describes at which point in time the metrics were observed"; } } // Event notifications augment "/yp:push-update" { description "This augmentation adds the observation timestamp of the accounted metrics in the push-update notification."; uses ypot:yang-push-observation; } augment "/yp:push-change-update" { description "This augmentation adds the observation timestamp of the event in the push-change-update notification."; uses ypot:yang-push-observation; } // Event capabilities augment "/sysc:system-capabilities/notc:subscription-capabilities" { description "Add system level capabilities"; leaf yang-push-observation-supported { if-feature "yang-push-observation-timestamp"; type inotifseq:notification-support; description "Specifies whether the publisher supports exporting observation-timestamp and point-in-time in notifications."; reference "RFC XXXX: YANG Notifications Observation Time"; } } } ]]>



    
      Note to the RFC-Editor: Please remove this section before
      publishing.

      
        6WIND implemented this document for a YANG Push publisher on UDP-based Transport for Configured
        Subscriptions in their VSR platform.
      
    

    
      
        Since the timespan between network state change and subscription
        establishment as exampled in timeline with "T1" and "T2" in  for "on-change sync on
        start" subscriptions could be very long when the network node uptime
        and thus the state change was long time ago and the subscription is
        establish very recent, a time series database may discard the
        notification message at ingestion since the observation timestamp is
        in the very past and therefore would have potential performance impact
        on the time series database indexing. This can be circumvent by using
        the eventTime for indexing or a change to "on-change" subscriptions
        instead.
      
    

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

    
      This document describes the URI used for the IETF XML Registry and
      registers a new YANG module name.

      
        IANA is requested to add this document as a reference in the
        following URI in the IETF XML Registry .

        
          URI:

          urn:ietf:params:xml:ns:yang:ietf-yp-observation

          Registrant Contact:

          The IESG.

          XML:

          N/A; the requested URI is an XML namespace.

          Reference:

          RFC5277; RFC-to-be
        
      

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

        
          name:

          ietf-yp-observation

          namespace:

          urn:ietf:params:xml:ns:yang:ietf-yp-observation

          prefix:

          ypot

          Reference:

          RFC-to-be
        
      
    

    
      The authors would like to thank Rob Wilton, Nick Corran, Pierre
      Francois Ahmed Elhassany, Jean Quilbeuf and Marco Tollini for their
      review and valuable comments.