Extensible YANG model for YANG-Push Notifications

YANG-Push allows publishers to send notifications to a data collection. The YANG-Push receiver decodes the message and optionally validates the header and the content before forwarding to the next process. The notification container from YANG-Push is currently based on the XML model from NETCONF Event Notifications . This model has the drawback that only a single mandatory "eventTime" leaf is defined and does offer a way to extend this header with new metadata. Additionally, this XML model is only valid for XML-based environments. When messages are encoded in other YANG encodings, such as JSON or CBOR , validators cannot use YANG to validate the message schema. YANG data consumer receiving notifications require additional metadata to understand the full context of the received message. For example, in addition to the timestamp of when the event was encoded, it is also important to know the hostname which sourced the message, and have sequence numbers in generated messages so that lost notification messages can be detected. This additional metadata is also helpful to correlate the data with other sources of Network Telemetry information. For such reasons, this document proposes the following:

First, it provides an extensible YANG notification header allowing implementors and IETF contributors to easily add new metadata to the notification message.
Second, it provides the first crucial extensions enabling operators to identify which network node publishes which YANG-Push messages and when the events or metrics were observed on the network node.
And finally, it provides a way to enable and disable these extensions on a subscription basis, making the coexistence of different YANG-Push and NETCONF Event Notification possible.

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 "subscriber", "publisher", and "receiver" are used as defined in . The terms "client" is used as defined in for NETCONF and for RESTCONF. The terms "implementation-time information" and "runtime information" are used as defined in .

This section shows the relationship to , , and .

defines a mechanism for NETCONF nodes to send notifications to a collector. These are the key relationships between the current document and :

This document does not change the header defined by nor update any behavior defined in . Implementations of use the header defined in Section 2.2.1 of .
The co-existance of the notification model defined in and the model defined in the current document is possible. The co-existence is discussed in .

Subscribed Notifications defines a mechanism on top of to stream notifications from the NETCONF node. These are the key relationships between the current document and :

Section 1.4 of states that the the solution uses the notification header defined in . This document proposes a new header, which clients can enable and replace the previously defined. When this new header is used, notification messages are encoded as defined in Section .
Section 2.4.2 of defines how a YANG-Push subscription is defined via an the 'establish-subscription' RPC. This document extends the RPCs from Subscribed Notifications to support enabling the new header defined in this document.

defines how YANG data is encoded in XML. These are the key relationship points between the current document and :

Section 7.16.2 of defines the XML encoding of YANG notification. This document defines a new header for such notifications. When a YANG-Push publisher implements the specifications in this document with the XML encoding, the notifications are encoded according to in this document.

defines how YANG data is encoded using JSON. These are the key relationship points between the current document and :

does not define explicitly how a YANG notification should be encoded using JSON encoding. This document specifies a new header for such notifications. When a YANG-Push publisher implements the specifications in this document with JSON encoding, the notifications are encoded according to in this document.

defines how YANG data is encoded using CBOR. These are the key relationship points between the current document and :

does not define explicitly how a YANG notification should be encoded using CBOR encoding. When a YANG-Push publisher implements the specifications in this document in CBOR encoding, the notifications are encoded according to in this document.

Section 4.2.10 of 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 metadata which encapsulates the content and the content defined by the 'notification' statement. In YANG 1.1 , the notification header is based on the model defined in which contains a single metadata 'eventTime' leaf. An example extracted from is shown in the following XML: 2007-09-01T10:00:00Z

so-1/2/3.0

down

]]> This document defines a new notification header and enables extending it with new metadata. The notification header defined in the following sections is to be used in YANG-Push environments and can be implemented with NETCONF and RESTCONF . defines how a client enables the header defined in this document. extends the model from to enable clients to discover the capability of using the new notification header for both implementation-time information and runtime information. Lastly, defines the new notification header and how it is encoded using XML, JSON and CBOR.

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 to support the configuration of "notification-envelope". When the node 'enable-notification-envelope' is set to true, the notifications published by a YANG-Push publisher MUST use the header defined in . If any metadata is enabled during the configuration of the subscription, the metadata nodes MUST be present in the header.

A client can discover the support of 'notification-envelope' model through the capabilities model defined in . This documents extends the 'ietf-notification-capabilities' model with a container that includes:

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.

The YANG model defined in augments the 'ietf-notification-capabilities' model with the leaf and container listed above. This model can be retrieved via a NETCONF <get> RPC.

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

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 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 'notification-contents' leaf.

The following YANG tree illustrates the notification envelope containing the mandatory metadata 'event-time'. See for more detail on the optional metadata. ]]>

The YANG notification can be encoded using XML , JSON and CBOR .

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": 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 . Other metadata defined within the YANG module defined in MUST use the same XML namespace. See for more details. When other 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 "notification-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 encoded in XML:

2024-10-10T10:59:55.32Z

1011

eth0

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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 . 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 . Other metadata defined within the YANG module defined in MUST use the same namespace "ietf-yp-notification". When other 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 for more details. The content of the notification that is defined by the 'notification' statement is encoded in the "notification-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 encoded in JSON:

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 . 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 . 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 . A SID allocation process is needed beforehand following . 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 . When other 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 for more details. The content of the notification that is defined by the 'notification' statement is encoded in the "notification-contents" node. The name and namespace of this payload element are determined by the YANG module containing the 'notification' statement representing the notification message. Similarly, SIDs can be used as keys if they are well allocated. shows a "push-update" notification defined in the YANG module of YANG-Push encoded in CBOR using names as keys. The example uses the CBOR diagnostic notation as defined in section 3.1 of :

And shows the same notifcation encoded using SIDs:

This section described two optional YANG notification header extensions which are enabled by default when the notification envelope is enabled. When the envelope is enabled using the "enable-notification-envelope" node, the publisher includes by default the "hostname" and "sequence-number" defined in the following sections. The client discovers the support of these two extension headers with the mechanism defined in . This document defines the following metadata as shown in the following YANG tree . See the following sections for more details. ]]>

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 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 or among different YANG-Push subscription types as defined in , 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 , 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 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 .

provides an example of a JSON encoded, , "push-update" notification message with hostname and sequence-number as extension.

TBD: explain co-existence with RFC5277

This YANG module extends "ietf-subscribed-notifications" and "ietf-notification-capabilities" as shown in the following YANG tree : ]]>

The YANG module augments the module "ietf-subscribed-notifications" , augments the module "ietf-system-capabilities" , and uses "ietf-yang-types" module and . WG List: Authors: Alex Huang Feng Pierre Francois Thomas Graf Benoit Claise "; 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) 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 (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices."; revision 2024-10-18 { description "First revision"; reference "RFC XXXX: YANG-Push Notification Envelope"; } grouping notif-env-configuration { description "This grouping defines the configuration switches for enabling the notification-envelope defined in RFC XXXX and the different supported metadata."; 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."; } } 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."; } } } notification 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 notification-contents { description "This contains the values defined by the 'notification' statement unchanged."; } } // Subscription container augment "/sn:subscriptions/sn:subscription" { description "This augmentation adds the configuration switches for enabling the notification envelope and metadatas."; uses notif-env-configuration; } // Subscription RPCs augment "/sn:establish-subscription/sn:input" { description "This augmentation adds the configuration switches for enabling the notification envelope and other metadatas during the 'establish-subscription' RPC."; uses notif-env-configuration; } augment "/sn:modify-subscription/sn:input" { description "This augmentation adds the configuration switches for enabling the notification envelope and other metadatas during the 'establish-subscription' RPC."; uses notif-env-configuration; } // 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; } } } ]]>

TBD

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.

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

IANA is requested to register a new ".sid" file in the "IETF YANG SID Registry": A ".sid" file is proposed in .

The authors would like to thank Per Anderson, Andy Bierman, Carsten Bormann, Mohamed Boucadair, Tom Petch, Jason Sterne, Kent Watsen and Rob Wilton for their review and valuable comments.

Extensible Markup Language (XML) 1.0 (Second Edition) W3C

Note to the RFC-Editor: Please remove this section before publishing. For CBOR encoding using YANG-SIDs identifiers, a ".sid" file is requested to IANA in .