Extensible YANG Model for YANG-Push Notifications

Internet-Draft	YANG-Push Notification Envelope	March 2025
Huang Feng, et al.	Expires 17 September 2025	[Page]

Abstract

This document defines a new extensible notification structure, defined in YANG, for use in YANG-Push Notification messages enabling any YANG compatible encodings such as XML, JSON or CBOR. Additionally, it defines two essential extensions to this structure, the support of a hostname and a sequence number and the support of a timestamp characterizing the moment when the changed data was observed.¶

3. Solution

Section 4.2.10 of [RFC7950] defines the encoding of YANG notifications. A notification is created by defining a 'notification' statement in the YANG module. When a NETCONF server sends this notification, it is composed of two parts: a header containing notification metadata which encapsulates the content and the content defined by the 'notification' statement.¶

In YANG 1.1 [RFC7950], the notification header is based on the model defined in [RFC5277] which contains a single metadata 'eventTime' leaf. An example extracted from [RFC7950] is shown in the following XML:¶

  <notification
      xmlns="urn:ietf:params:netconf:capability:notification:1.0">
    <eventTime>2007-09-01T10:00:00Z</eventTime>
    <link-failure xmlns="urn:example:system">
      <if-name>so-1/2/3.0</if-name>
      <if-admin-status>up</if-admin-status>
      <if-oper-status>down</if-oper-status>
    </link-failure>
  </notification>

This document defines a new notification header and enables extending this header with new notification metadata. The notification header and extensions defined in the following sections are to be used in YANG-Push [RFC8641] environments and can be implemented with NETCONF [RFC6241] and RESTCONF [RFC8040]. Thus, when enabled, this new header replaces the notifications defined in Subscribed Notifications [RFC8639] and YANG-Push [RFC8641] notifications globally for all the entire server.¶

Section 3.1 defines how a client enables the header defined in this document. Section 3.2 extends the model from [RFC9196] to enable clients to discover the capability of using the new notification header for both implementation-time information and runtime information. Lastly, Section 3.3.2 defines the new notification header and how it is encoded using XML, JSON and CBOR.¶

3.1. Enabling the Notification Envelope

The use of the notification envelope defined in this document can be enabled during the configuration of a YANG-Push subscription. This document augments the "ietf-subscribed-notification" model [RFC8639] to support the configuration of the "notification-envelope". When enabled, all the notifications defined in Subscribed Notification [RFC8639] and YANG-Push [RFC8641] are encoded as defined in Section 3.3.¶

module: ietf-yp-notification

  augment /sn:subscriptions:
    +--rw enable-notification-envelope?   boolean
    +--rw metadata

When the node 'enable-notification-envelope' is set to true, the notifications published by a YANG-Push publisher MUST use the header defined in Section 3.3.1. If any notification metadata is enabled during the configuration of the subscription, the notification metadata nodes MUST be present in the header. When this node is disabled, notifications are encoded as defined in NETCONF Event Notifications [RFC5277].¶

When there are existing subscriptions and a client changes the node 'enable-notification-envelope', all existing subscriptions MUST be terminated. The publisher MUST send a 'subscription-terminated' notification to all the existing subscriptions using the header configured prior to the change. Any new subscription after the change use the header defined by the node 'enable-notification-envelope', i.e. encoded as Section 3.3.1 when enabled and as defined in [RFC5277] if disabled.¶

3.2. Discovering the support of this model

A client can discover the support of 'notification-envelope' model through the capabilities model defined in [RFC9196]. This documents extends the 'ietf-notification-capabilities' model with:¶

A container containing a leaf 'notification-envelope', stating that the YANG notification can be encoded following the notification-envelope model.¶
A container 'metadata' containing all the supported extensions to this header. Extensions are defined in Section 3.4.¶

The YANG models defined in Section 5 augments the 'ietf-notification-capabilities' model with the leaf and container listed above:¶

  augment /sysc:system-capabilities/notc:subscription-capabilities:
    +--ro notification-metadata
       +--ro notification-envelope?   boolean
       +--ro metadata

This model can be retrieved via a NETCONF <get> RPC.¶

3.3. Notification Envelope

This section defines how YANG notifications are structured when the notification envelope is enabled on YANG-Push subscriptions. The following sections define how this model is encoded in XML, JSON and CBOR.¶

3.3.1. Base Notification Model

When a YANG-Push publisher uses the notification model defined in this document, the notification is structured as follows:¶

The notification is encapsulated in a root "envelope" container.¶
The header of the notification contains the notification metadata that is enabled during the configuration of the subscription as a child nodes of the root "notification-envelope" container.¶
The content of the notification defined by the 'notification' statement is encoded in the 'contents' leaf.¶
The 'contents' element SHOULD be located at the end of the notification envelop structure.¶

The following YANG tree [RFC8340] illustrates the notification envelope supporting only the mandatory metadata 'event-time'. See Section 3.4 for more extensions to this header.¶

  structure envelope:
    +-- event-time         yang:date-and-time
    +-- contents?          <anydata>

3.3.2. Encoding of the Notification model

The YANG notification can be encoded using XML [W3C.REC-xml-20001006][RFC7951], JSON [RFC7951] and CBOR [RFC9254].¶

3.3.2.1. XML encoding

A YANG notification encoded in XML is structured as a root "envelope" container. The namespace of this container is the namespace defined in the YANG module "ietf-yp-notification":¶

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

Two mandatory child nodes within the "envelope" container are expected, representing the event time and the notification payload. The "event-time" node is defined within the same XML namespace as the "envelope" container. The "event-time" node MUST be compliant with [RFC3339]. Other notification metadata defined within the YANG module defined in Section 5.1.2 MUST use the same XML namespace. See Section 3.4 for more details.¶

When other notification metadata is enabled through configuration, the supplementary nodes are encoded at the same level of the mandatory "event-time" node and use the XML namespace defined in the YANG module.¶

The content of the notification that is defined by the 'notification' statement is encoded in the "contents" node. The name and namespace of this payload element are determined by the YANG module containing the 'notification' statement representing the notification message.¶

The following example shows a "push-update" notification defined in the YANG module of YANG-Push [RFC8641] encoded in XML:¶

<envelope xmlns="urn:ietf:params:xml:ns:yang:ietf-yp-notification">
  <event-time>2024-10-10T10:59:55.32Z</event-time>
  <contents>
    <push-update xmlns="urn:ietf:params:xml:ns:yang:ietf-yang-push">
      <id>1011</id>
      <datastore-contents>
        <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces">
          <interface>
            <name>eth0</name>
            <oper-status>up</oper-status>
          </interface>
        </interfaces>
      </datastore-contents>
    </push-update>
  </contents>
</envelope>

Figure 1: XML-encoded notification

3.3.2.2. JSON Encoding

A YANG notification encoded in JSON is structured as a root "envelope" container. The namespace of this container is the name of the YANG module "ietf-yp-notification" defined in Section 5.1.2.¶

Two mandatory child nodes within the "ietf-notification:envelope" container are expected, representing the event time and the notification payload. The "event-time" node is defined within the same namespace as the "ietf-yp-notification:envelope" container and is compliant with [RFC3339]. Other metadata specified within the YANG module defined in Section 5.1.2 MUST use the same namespace "ietf-yp-notification".¶

When other notification metadata is enabled through configuration, the supplementary nodes are encoded at the same level of the mandatory 'event-time' node and use the YANG module name as its namespace. See Section 3.4 for more details.¶

The following example shows a "push-update" notification defined in the YANG module of YANG-Push [RFC8641] encoded in JSON:¶

    {
        "ietf-yp-notification:envelope": {
            "event-time": "2024-10-10T08:00:11.22Z",
            "contents": {
              "ietf-yang-push:push-update": {
                  "id": 1011,
                  "datastore-contents": {
                      "ietf-interfaces:interfaces": [
                          {
                              "interface": {
                                  "name": "eth0",
                                  "oper-status": "up"
                              }
                          }
                      ]
                  }
              }
            }
        }
    }

Figure 2: JSON-encoded notification

3.3.2.3. CBOR Encoding

YANG notifications can be encoded in CBOR using Names or SIDs in keys.¶

Notifications encoded using names is similar to JSON encoding as defined in Section 3.3 of [RFC9254]. The key of the element can be the name of the element itself or be namespace-qualified. In the latter case, the namespace of the notification container uses the YANG module name "ietf-yp-notification" defined in Section 5.1.2.¶

Notification encoded using YANG-SIDs replaces the names of the keys of the CBOR encoded message for a 63 bit unsigned integer. In this case, the keys of the encoded data use the SID value as defined in Section 3.2 of [RFC9254]. A SID allocation process is needed beforehand as defined in [RFC9595].¶

In the notification, two mandatory child nodes within the "ietf-yp-notification:envelope" container are expected, representing the event time and the notification payload. The "event-time" node is defined within the same namespace as the "ietf-yp-notification:envelope" container and is compliant with [RFC3339].¶

When other notification metadata is enabled through configuration, the supplementary nodes are encoded at the same level of the mandatory "event-time" node and use the YANG module name as its namespace when they are encoded as names. When they are encoded using YANG SIDs, a SID value assigned to the metadata node is used. See Section 3.4 for more details.¶

Figure 3 shows a "push-update" notification defined in the YANG module of YANG-Push [RFC8641] encoded in CBOR using names as keys. The example uses the CBOR diagnostic notation as defined in section 3.1 of [RFC9254]:¶

  {
      "ietf-yp-notification:envelope": {
          "event-time": "2024-10-10T08:00:11.22Z",
          "contents": {
            "ietf-yang-push:push-update": {
                "id": 1011,
                "datastore-contents": {
                    "ietf-interfaces:interfaces": [
                        {
                            "interface": {
                                "name": "eth0",
                                "oper-status": "up"
                            }
                        }
                    ]
                }
            }
          }
      }
  }

Figure 3: CBOR-encoded notification using diagnostic notation

And Figure 4 shows the same notifcation encoded using SIDs:¶

  {
      2551: {
          1: "2024-10-10T08:00:11.22Z",
          4: {
            "ietf-yang-push:push-update": {
                "id": 1011,
                "datastore-contents": {
                    "ietf-interfaces:interfaces": [
                        {
                            "interface": {
                                "name": "eth0",
                                "oper-status": "up"
                            }
                        }
                    ]
                }
            }
          }
      }
  }

Figure 4: CBOR-encoded notification using YANG SIDs in CBOR diagnostic notation

3.4. Extensions for the Notification Envelope

This section describes two envelope header extensions. When the envelope is enabled via the "enable-notification-envelope" node, the publisher includes by default the "hostname" and "sequence-number" defined in Section 3.4.1. The client discovers the support of these two extensions with the mechanism defined in Section 3.2. When the extensions defined in this document are supported by the server, the client discovers the presence of these new metadata with the following augmentations in the 'ietf-notification-capabilities':¶

module: ietf-yp-notification

  augment /sysc:system-capabilities/notc:subscription-capabilities:
    +--ro notification-metadata
       +--ro notification-envelope?   boolean
       +--ro metadata
          +--ro hostname-sequence-number?   boolean

module: ietf-yp-observation

  augment /sysc:system-capabilities/notc:subscription-capabilities:
    +--ro yang-push-observation-supported?   boolean
            {yang-push-observation-timestamp}?

This document defines the following notification metadata as shown in the following YANG tree [RFC8340]. It also defines an extension to the YANG-Push header. See the following sections for more details.¶

  structure envelope:
    +-- event-time         yang:date-and-time
    +-- hostname?          inet:host
    +-- sequence-number?   yang:counter32
    +-- contents?          <anydata>

3.4.1. Support of Hostname and Sequencing

When YANG-Push notification messages are forwarded from a receiver to another system, such as a message broker or a time series database, the transport context is lost since it is not part of the notification metadata of the notification container. Therefore, the downstream system is unable to associate the message to the publishing process (the exporting network node), nor able to detect message loss or reordering.¶

To correlate network data among different Network Telemetry planes as described in Section 3.1 of [RFC9232] or among different YANG-Push subscription types as defined in Section 3.1 of [RFC8641], a reference to the node streaming the data is needed. This is essential for understanding the timely relationship among these different planes and YANG-Push subscription types.¶

Today, network operators work around this impediment by preserving the transport source IP address and sequence numbers of the publishing process. However, this implies encoding this information in the YANG-Push notification messages which impacts the semantic readability of the message in the downstream system.¶

On top of that, the transport source IP address might not represent the management IP address by which the YANG-Push publisher should be known. In other terms, the source-host [RFC6470], which is the "Address of the remote host for the session" might not be the management IP address.¶

To overcome these issues, this document proposes a notification container extension with a hostname and a sequence number. This allows the downstream system to not only be able to identify from which network node, subscription, and time the message was published but also, the order of the published messages.¶

hostname:: Describes the node's hostname according to the 'sysName' object definition in [RFC1213] from where the message was published from. This value is usually configured on the node by the administrator to uniquely identify the node in the network.¶

sequence-number:: Generates a unique sequence number for each published message by the publisher process. The number counts up at every published notification message as described in [RFC9187].¶

Figure 5 provides an example of a JSON encoded, [RFC8259], "push-update" notification message with hostname and sequence-number as extension.¶

========== NOTE: '\' line wrapping per RFC 8792) ===========

{
    "ietf-yp-notification:envelope": {
    "event-time": "2023-03-25T08:30:11.22Z",
    "hostname": "example-router",
    "sequence-number": 1,
    "contents": {
      "ietf-yang-push:push-update": {
        "id": 6666,
        "datastore-contents": {
          "ietf-interfaces:interfaces": [
            {
              "interface": {
                "name": "eth0",
                "type": "iana-if-type:ethernetCsmacd",
                "oper-status": "up",
                "mtu": 1500
              }
            }
          ]
        }
      }
    }
  }
}

Figure 5: JSON Example for a 'push-update' notification message

3.5. Extensions for the YANG-Push Envelope

This section described two optional YANG 'push-update' and 'push-change-update' notification header extensions which are enabled by default. The client discovers the support of these two extension headers with the mechanism defined in Section 3.2.¶

This document defines the following notification metadata as shown in the following YANG tree [RFC8340]. See the following sections for more details.¶

module: ietf-yang-push

  notifications:
    +---n push-update
    |  +--ro id?                      sn:subscription-id
    |  +--ro datastore-contents?      <anydata>
    |  +--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

3.5.1. Support of Observation Timestamp

To correlate network data among different Network Telemetry planes, as described in Section 3.1 of [RFC9232], or among different YANG-Push subscription types, as defined in Section 3.1 of [RFC8641], a receiver needs a timestamp reference to align all the metrics and events. The observation timestamp defined in this document characterizes the moment the state change was observed or the moment when the data was measured, so that a receiver can correctly align the collected data.¶

The delay between the YANG-Push export process and the reception of the message at the receiver instance can be measured using the node 'event-time' defined in Section 3.3.1. However, as the 'event-time' node only defines the moment when the YANG-Push message was crafted and sent, the moment when such metrics were collected or the state changes were observed cannot be measured using this timestamp. The observation timestamp defined in this section characterizes the moment when the metrics were observed, which enable aligning the received metrics to the actual moment they were measured.¶

When the time bucket length in a time series database and the periodical YANG-Push subscription time is configured with the same values, the 'event-time' of the NETCONF notification message header can be used for indexing the data in the time series database. There is a variable delay between the observation timestamp, the 'event-time', and the anchor-time as described in Section 4.2 of [RFC8641]. When these timestamps are close to the time bucket boundaries, a time bucket may experience data collection discrepancies, e.g. 0 measurements are aggregated into one time bucket while the next time bucket contains 2 measurements. This lead to inconsistent accounting errors in the time series database. This problem is resolved by using the observation timestamp instead of the 'event-time' for time series database indexation.¶

By extending YANG-Push Notifications with the observation timestamp and a 'point-in-time' node, the data collection process can always ensure that it has the best available time for indexing the data. It can therefore use unconditionally the observation timestamp node in the data processing chain to correctly align the metrics and events. At the same time, the 'point-in-time' node ensures that the semantics associated to the timestamp are not lost throughout the data collection chain.¶

Besides the Subscription ID as described in Section 3.7 of [RFC8641], 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 "periodical" subscriptions and for the "push-change-update" notification in "on-change" subscriptions.¶

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 the point in time where the metrics are polled and observed in "periodical" subscriptions.¶

'initial-state' states the initial point in time when the subscription was established and the state was observed for "on-change sync on start" subscriptions.¶

'state-changed' states the point in time when the state change was observed after the subscription was established for "on-change" and "on-change sync on start" subscriptions.¶

3.5.1.1. Usage Example

This section illustrates the usage of the "point-in-time" node in two different subscriptions. Section 3.5.1.1.1 showcases a YANG-Push subscription monitoring the state of an interface using a 'on-change sync on start' subscription. Section 3.5.1.1.2 illustrates the usage of the 'point-in-time' node within periodical subscriptions.¶

3.5.1.1.1. On-Change Subscriptions

Figure 6 illustrates the set of events that lead to the generation of 'on-change' YANG-Push notifications. This timeline depicts the following states and events:¶

T1: At first, the operational state of the interface is "Up".¶
T2: After configuring an 'on-change' subscription supporting 'sync on start', the publisher sends the initial state of the interface.¶
T3: This is the moment the interface changes its operational status to "Down".¶
T4: After the interface state changes, the publisher generates the 'on-change' notification alerting the receiver.¶

Timeline
---------------------------------------------------------------------->
 | (T1) Interface | (T2) YANG-Push   | (T3) Interface | (T4) YANG-Push
 | state changed  | "on-change sync  | state changed  | "on-change"
 | to "Up".       | on start"        | to "Down".     | notification
 |                | subscription for |                | with the new
 |                | interface state  |                | interface state.
 |                | is established.  |                |
 v                v                  v                v

Figure 6: Example timeline for On-Change Sync on Start Subscription

At T2, after configuring the subscription, the publisher triggers a 'push-update' notification as depicted in Figure 7. The 'event-time' is the moment the YANG-Push process triggered the notification while the 'ietf-yp-observation:timestamp' node characterizes the timestamp T1, the latest moment this state was observed. In this case, the 'point-in-time' node is set to 'initial-state'.¶

{
  "ietf-yp-notification:envelope": {
    "event-time": "2025-03-25T08:30:11.22Z",
    "hostname": "example-router",
    "sequence-number": 1,
    "contents": {
      "ietf-yang-push:push-update": {
        "id": 6666,
        "ietf-yp-observation:timestamp": "2025-03-25T08:29:30.22Z",
        "ietf-yp-observation:point-in-time": "initial-state",
        "datastore-contents": {
          "ietf-interfaces:interfaces": [
            {
              "interface": {
                "name": "eth0",
                "type": "iana-if-type:ethernetCsmacd",
                "oper-status": "up",
                "mtu": 1500
              }
            }
          ]
        }
      }
    }
  }
}

Figure 7: Example of 'push-update' notification sent after the subscription is established.

After T3, the publisher triggers a 'push-change-update' notification announcing an interface status change to the receiver as depicted in Figure 8. In this case, the 'ietf-yp-observation:timestamp' node characterizes the moment the interface changed its status at T3 while the value of the 'event-time' node characterizes the moment the YANG-Push process generated the message at T4.¶

{
  "ietf-yp-notification:envelope": {
    "event-time": "2025-03-25T08:35:12.22Z",
    "hostname": "example-router",
    "sequence-number": 1,
    "contents": {
      "ietf-yang-push:push-change-update": {
        "id": 2222,
        "ietf-yp-observation:timestamp": "2025-03-25T08:34:05.22Z",
        "ietf-yp-observation:point-in-time": "state-changed",
        "datastore-contents": {
          "yang-patch": {
            "patch-id": "52",
            "edit": {
              "edit-id": "edit_example_1",
              "operation": "replace",
              "target": "/ietf-interfaces:interfaces",
              "value": {
                "interfaces": [
                  {
                    "interface": {
                      "name": "eth0",
                      "type": "iana-if-type:ethernetCsmacd",
                      "oper-status": "down",
                      "mtu": 1500
                    }
                  }
                ]
              }
            }
          }
        }
      }
    }
  }
}

Figure 8: JSON Push Example for a push-change-update notification message

3.5.1.1.2. Periodical Subscriptions

In periodical subscription, the observation time characterizes the time when the metrics were polled from the datastore before it generates the actual YANG-Push message.¶

Figure 9 illustrates the delays associated to the generation of the YANG-Push message. The timeline shows the following states:¶

T1: First, the periodical subscription is configured to push the operational status of the interface every N interval.¶
T2: This is the moment the YANG-Push process polls the data state data and metrics from the datastore.¶
T3: After polling the metrics, the YANG-Push process generates the 'push-update' notification.¶

    Timeline
    ------------------------------------------------------>
    | (T1) YANG-Push | (T2) YANG-Push | (T3) YANG-Push
    | "periodical"   | process polls  | "periodical"
    | subscription   | the metrics    | current
    | for interface  | from the       | accounting.
    | counter is     | datastore.     |
    | established    |                |
    v                v                v

Figure 9: Example timeline for Periodical Subscription

An example of a 'push-update' notification sent at T3 is illustrated in Figure 10. In this case, the node 'event-time' characterizes the moment the YANG-Push process generated the message while the node 'ietf-yp-observation:timestamp' establishes the moment when the metrics were polled from the datastore. For these periodical subscriptions, the 'point-in-time' node must be set to 'current-accounting'.¶

{
  "ietf-yp-notification:envelope": {
    "event-time": "2023-03-25T08:30:12.25Z",
    "hostname": "example-router",
    "sequence-number": 1,
    "contents": {
      "ietf-yang-push:push-update": {
        "id": 6666,
        "ietf-yp-observation:timestamp": "2023-03-25T08:30:00.00Z",
        "ietf-yp-observation:point-in-time": "current-accounting",
        "datastore-contents": {
          "ietf-interfaces:interfaces": [
            {
              "interface": {
                "name": "eth0",
                "type": "iana-if-type:ethernetCsmacd",
                "oper-status": "up",
                "mtu": 1500
              }
            }
          ]
        }
      }
    }
  }
}

Figure 10: JSON Push Example for a push-update notification message

5. YANG Modules

5.1. The 'ietf-yp-notification' Module

The following sections shows the YANG tree and YANG module for the 'ietf-yp-notification' module.¶

5.1.1. YANG ietf-yp-notification Tree Diagram

This YANG module extends "ietf-subscribed-notifications" [RFC8641] and "ietf-notification-capabilities" [RFC9196] as shown in the following YANG tree [RFC8340]:¶

module: ietf-yp-notification

  augment /sn:subscriptions:
    +--rw enable-notification-envelope?   boolean
    +--rw metadata
  augment /sysc:system-capabilities/notc:subscription-capabilities:
    +--ro notification-metadata
       +--ro notification-envelope?   boolean
       +--ro metadata
          +--ro hostname-sequence-number?   boolean

  structure envelope:
    +-- event-time         yang:date-and-time
    +-- hostname?          inet:host
    +-- sequence-number?   yang:counter32
    +-- contents?          <anydata>

5.1.2. YANG ietf-yp-notification Module

The YANG module augments the module "ietf-subscribed-notifications" [RFC8641], augments the module "ietf-notification-capabilities" [RFC9196] and uses "ietf-yang-types" module [RFC6991] and "ietf-yang-structure-ext" module [RFC8791].¶

<CODE BEGINS> file "[email protected]"

module ietf-yp-notification {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-yp-notification";
  prefix inotenv;
  import ietf-yang-types {
    prefix yang;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-inet-types {
    prefix inet;
    reference
      "RFC 6991: Common YANG Data Types";
  }
  import ietf-subscribed-notifications {
    prefix sn;
    reference
      "RFC 8639: Subscription to YANG Notifications";
  }
  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-yang-structure-ext {
    prefix sx;
    reference
      "RFC 8791: YANG Data Structure Extensions";
  }

  organization "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   <https://datatracker.ietf.org/group/netconf/>
     WG List:  <mailto:[email protected]>

     Authors:  Alex Huang Feng
               <mailto:[email protected]>
               Pierre Francois
               <mailto:[email protected]>
               Thomas Graf
               <mailto:[email protected]>
               Benoit Claise
               <mailto:[email protected]>";

  description
    "Defines a notification header for Subscribed Notifications
    [RFC8639] and YANG-Push [RFC8641]. When this notification header
    is enabled through configuration, the root container of the
    notification is encoded as defined in RFCXXX.

    This module can be used to validate XML encoded notifications
    [RFC7950], JSON encoded messages [RFC7951] and CBOR encoded
    messages [RFC9254]. Refer to Section Y of RFC XXXX for more
    details.

    Copyright (c) 2025 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://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
    for full legal notices.";

  revision 2025-02-24 {
    description
      "First revision";
    reference
      "RFC XXXX: YANG-Push Notification Envelope";
  }

  identity notif-envelope-error {
    description
      "Base identify for errors found while attempting to
      change the value of the leaf 'enable-notification-envelope'.";
  }

  grouping notif-env-capabilities {
    description
      "This grouping defines the capabilities for
      the notification-envelope defined in RFC XXXX
      and the different supported metadata.";
    leaf notification-envelope {
      type boolean;
      default false;
      description
        "Supports YANG-Push to use the notification-envelope
        defined in RFC XXXX.";
    }
    container metadata {
      description
        "Container with the supported optional metadata by the
        YANG-Push publisher.";
      leaf hostname-sequence-number {
        type boolean;
        default false;
        description
          "Supports hostname and sequence-number
          in the YANG-Push notifications as defined in the
          YANG-Push notification-envelope in RFC XXXX.";
      }
    }
  }

  sx:structure envelope {
    leaf event-time {
      type yang:date-and-time;
      mandatory true;
      description
        "The date and time the event was generated by the event
        source. This parameter is of type dateTime and compliant
        to [RFC3339].";
    }
    leaf hostname {
      type inet:host;
      description
        "The hostname of the network node according to
        [RFC1213]. This value is usually configured on the node
        by the administrator to uniquely identify the node in
        the network.";
    }
    leaf sequence-number {
      type yang:counter32;
      description
        "Unique sequence number as described in [RFC9187] for each
        published message.";
    }
    anydata contents {
      description
        "This contains the values defined by the 'notification'
        statement unchanged.";
    }
  }

  // Subscription container
  augment "/sn:subscriptions" {
    description
      "This augmentation adds the configuration switches for
      enabling the notification envelope and metadatas.";
    leaf enable-notification-envelope {
      type boolean;
      default false;
      description
        "Enables YANG-Push to use the notification-envelope
        defined in RFC XXXX.";
    }
    container metadata {
      description
        "Container for configuring optional metadata.";
    }
  }

  // YANG-Push Capabilities extension
  augment "/sysc:system-capabilities/notc:subscription-capabilities" {
    description
      "Extension to the subscription-capabilities model to enable
      clients to learn whether the publisher supports the
      notification-envelope";

    container notification-metadata {
      description
        "Adds the notification metadata capabilities to subscription
        capabilities.";
      uses notif-env-capabilities;
    }
  }
}

<CODE ENDS>

5.2. The 'ietf-yp-observation' Module

The following sections shows the YANG tree and YANG module for the 'ietf-yp-observation' module.¶

5.2.1. YANG ietf-yp-observation Tree Diagram

This YANG module extends "ietf-yang-push" [RFC8641] and "ietf-notification-capabilities" [RFC9196] as shown in the following YANG tree [RFC8340]:¶

module: ietf-yp-observation

  augment /yp:push-update:
    +--ro timestamp?       yang:date-and-time
    +--ro point-in-time?   enumeration
  augment /yp:push-change-update:
    +--ro timestamp?       yang:date-and-time
    +--ro point-in-time?   enumeration
  augment /sysc:system-capabilities/notc:subscription-capabilities:
    +--ro yang-push-observation-supported?   boolean
            {yang-push-observation-timestamp}?

5.2.2. YANG ietf-yp-observation Module

The YANG module augments the module "ietf-yang-push" [RFC8641], augments the module "ietf-system-capabilities" [RFC9196].¶

<CODE BEGINS> file "[email protected]"

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";
  }
  organization "IETF NETCONF (Network Configuration) Working Group";
  contact
    "WG Web:   <http:/tools.ietf.org/wg/netconf/>
     WG List:  <mailto:[email protected]>

     Authors:  Thomas Graf
               <mailto:[email protected]>
               Benoit Claise
               <mailto:[email protected]>
               Alex Huang Feng
               <mailto:[email protected]>";

  description
    "Defines YANG-Push event notification header with the observation
    time in streaming update notifications.

    Copyright (c) 2025 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 2025-02-24 {
    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 boolean;
      description
        "Specifies whether the publisher supports exporting
        observation-timestamp and point-in-time in notifications.";
      reference
        "RFC XXXX: YANG Notifications Observation Time";
    }
  }
}

<CODE ENDS>