Adaptive Subscription to YANG Notifications
draft-ietf-netconf-adaptive-subscription-18
| Document | Type | Active Internet-Draft (netconf WG) | |
|---|---|---|---|
| Authors | Qin Wu , Peng Liu , Qiufang Ma , Wei Wang , Zhixiong Niu | ||
| Last updated | 2026-04-28 (Latest revision 2026-04-22) | ||
| Replaces | draft-wang-netconf-adaptive-subscription | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Experimental | ||
| Formats | |||
| Yang Validation | 0 errors, 0 warnings | ||
| Reviews |
YANGDOCTORS Early review
(of
-07)
by Joe Clarke
On the right track
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Thomas Graf | ||
| Shepherd write-up | Show Last changed 2025-10-16 | ||
| IESG | IESG state | RFC Ed Queue | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Mahesh Jethanandani | ||
| Send notices to | thomas.graf@swisscom.com | ||
| IANA | IANA review state | IANA OK - Actions Needed | |
| IANA action state | RFC-Ed-Ack | ||
| IANA expert review state | Expert Reviews OK | ||
| IANA expert review comments | The ns registration has been approved. | ||
| RFC Editor | RFC Editor state | EDIT | |
| Details |
draft-ietf-netconf-adaptive-subscription-18
NETCONF Working Group Q. Wu
Internet-Draft Huawei
Intended status: Experimental P. Liu
Expires: 24 October 2026 China Mobile
Q. Ma
Huawei
W. Wang
China Telecom
Z. Niu
Microsoft
22 April 2026
Adaptive Subscription to YANG Notifications
draft-ietf-netconf-adaptive-subscription-18
Abstract
This document defines an experimental mechanism and its companion
YANG data model to enable adaptive subscriptions to YANG
notifications. The publisher can dynamically adjust the periodic
update interval based on the evaluation of pre-configured conditions
(e.g., thresholds or expressions). This allows for finer-grained
telemetry by increasing update frequency when certain criteria are
met, and reducing it otherwise.
Editorial Note (To be removed by RFC Editor)
Note to the RFC Editor: This section is to be removed prior to
publication. Please also remove Section 6.
This document contains placeholder values that need to be replaced
with finalized values at the time of publication. This note
summarizes all of the substitutions that are needed. No other RFC
Editor instructions are specified elsewhere in this document.
Please apply the following replacements:
* XXXX --> the assigned RFC number for this document
* 2026-02-27 --> the actual date of the publication of this document
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Wu, et al. Expires 24 October 2026 [Page 1]
Internet-Draft Adaptive Subscription April 2026
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 24 October 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Experimental Considerations . . . . . . . . . . . . . . . 5
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Adaptive Subscription Parameters . . . . . . . . . . . . 6
2.2. RPC Failures . . . . . . . . . . . . . . . . . . . . . . 8
2.3. Subscription State Change Notifications . . . . . . . . . 9
2.4. Notifications for Adaptive Subscribed Content . . . . . . 10
3. Adaptive Subscription Data Model . . . . . . . . . . . . . . 11
3.1. YANG Tree Diagram . . . . . . . . . . . . . . . . . . . . 11
3.2. The "ietf-adaptive-subscription" Module . . . . . . . . . 13
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
4.1. Updates to the IETF XML Registry for New YANG Module . . 21
4.2. Updates to the YANG Module Names Registry for New YANG
Module . . . . . . . . . . . . . . . . . . . . . . . . . 22
5. Operational Considerations . . . . . . . . . . . . . . . . . 22
5.1. XPath Complexity Evaluation . . . . . . . . . . . . . . . 22
5.2. Threshold Selection for XPath Evaluation . . . . . . . . 23
5.3. Deployment and Monitoring Considerations . . . . . . . . 24
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 24
Wu, et al. Expires 24 October 2026 [Page 2]
Internet-Draft Adaptive Subscription April 2026
7. Security Considerations . . . . . . . . . . . . . . . . . . . 26
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 27
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 27
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
10.1. Normative References . . . . . . . . . . . . . . . . . . 28
10.2. Informative References . . . . . . . . . . . . . . . . . 29
Appendix A. Use Cases . . . . . . . . . . . . . . . . . . . . . 30
A.1. Wireless Network Performance Monitoring . . . . . . . . . 30
A.2. Reducing Impact on High CPU Utilization . . . . . . . . . 31
Appendix B. Example YANG Module . . . . . . . . . . . . . . . . 31
B.1. "example-wifi-network-diagnostic" YANG Module . . . . . . 32
Appendix C. Adaptive Subscription and Notification Example . . . 36
C.1. Configured Subscription Example . . . . . . . . . . . . . 37
C.2. Dynamic Subscription Example . . . . . . . . . . . . . . 38
C.3. Error Response Examples . . . . . . . . . . . . . . . . . 39
C.3.1. "xpath-evaluation-unsupported" error response
example . . . . . . . . . . . . . . . . . . . . . . . 39
C.3.2. "evaluation-interval-unsupported" error response
example . . . . . . . . . . . . . . . . . . . . . . . 40
C.4. "adaptive-period-update" notification example . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 42
1. Introduction
YANG-Push subscriptions [RFC8641] allow subscriber applications to
request a continuous customized stream of updates from a YANG
datastore without needing to poll. It defines a mechanism called
update trigger to determine when an update record needs to be
generated. Two types of subscriptions are introduced in Section 3.1
of [RFC8641], distinguished by how updates are triggered: periodic
and on-change.
* Periodic subscription allows subscribed data to be streamed to the
destination at a configured fixed time interval;
* On-change subscription allows updates to be triggered whenever a
change in the subscribed information is detected.
However, in some deployments involving an increased data collection
rate or "on-change" subscription to push updates that change more
frequently than the receiver can effectively process, it becomes more
likely that both the receiver and the publisher could be temporarily
overwhelmed with a burst of streamed data, and network and
computation resources could be excessively consumed. Therefore, it
may be expensive to continuously monitor operational data at a high
collection rate, and on-change subscriptions are only suitable for
data that changes infrequently and may not be supported by all
implementations or every data object. Conversely, if a stream of
Wu, et al. Expires 24 October 2026 [Page 3]
Internet-Draft Adaptive Subscription April 2026
data is collected at a lower rate or some low priority data is
allowed to be dropped, insufficient data might not be able to detect
and diagnose service problems.
A client might choose to monitor the operational state and send a
request to modify the data collection rate on the server (also
referred to as the "publisher") as needed. But how often the client
evaluates if the modification of the data collection rate is required
highly depends on the current collection rate, collecting a stream of
data at a low rate prevents the subscriber from capturing sufficient
data for timely decision-making.
This document defines an experimental mechanism and its companion
YANG data model to enable adaptive subscription to YANG
notifications. Servers can be configured with multiple different
period intervals and corresponding period update conditions which
allow servers/publishers to automatically switch to different period
intervals according to the network condition changes without the
interaction with the client for policy update instructions. Applying
adaptive subscription allows publishers to adjust the subscription
period dynamically based on pre-defined threshold for finer-grained
network telemetry data sent to receivers.
1.1. Terminology
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are defined in [RFC5277], [RFC7950], [RFC8342],
[RFC8639], [RFC8641] and are not redefined here:
* Event
* Client
* Server
* Configuration
* Configured subscription
* Configuration datastore
* Notification message
Wu, et al. Expires 24 October 2026 [Page 4]
Internet-Draft Adaptive Subscription April 2026
* Publisher
* Receiver
* Subscriber
* Subscription
* On-change subscription
* Periodic subscription
* Selection filter
* Datastore node
* Update trigger
* Update record
This document defines the following term:
Adaptive Subscription: A subscription that specifies subscription
period update policy on the servers when the subscription is
initialized and allows servers/publishers to automatically switch
to different period intervals according to network condition
changes without interacting with the client for update policy
instructions. This mechanism also requires the client to handle
varying update period intervals and potential increases in update
volume resulting from interval switches.
1.2. Experimental Considerations
The YANG data model and associated mechanism detailed in this
document are designated as experimental. The experiment aims to
explore the use of XPath condition expressions as defined in "eval-
expression" parameter to determine the period interval with which to
report updates, as well as the selection of "eval-interval" parameter
to optimally balance detection effectiveness against system resource
overhead, and how server resource availability impacts this balance.
RPC failures specified in Section 2.2 prevent unspecified failures
when the server cannot satisfy the adaptive subscription request.
They may serve as safeguards against unstable behaviors or
unpredictable states, thereby easing troubleshooting for operators.
Wu, et al. Expires 24 October 2026 [Page 5]
Internet-Draft Adaptive Subscription April 2026
Moreover, the deployment also needs to assess whether the client can
effectively handle varying period intervals and potential increases
in update volume resulting from adaptive interval switches, including
client-side buffer management, processing overhead, and behavior when
experiencing sudden bursts of updates.
Additional implementations would be necessary in the future to assess
the scalability, stability, and effectiveness of the proposed
solution in the document. It is encouraged that parties
participating in this experiment will publish experimental results
within one year of the publication of this document. The absence of
published results after this period will be one factor considered by
the community in assessing the interest level and maturity of the
approach. Experimental results and feedback for the experiment
should include:
* Stability under high-frequency state change scenarios (e.g.,
interface flapping).
* Scalability across diverse network scales and a description of
these network scales.
* Operational impact on system resources.
* Operational impact on client's ability to handle dynamically
changing update intervals, including its resource consumption.
* Telemetry data transmission savings achieved through adaptive
subscription compared with periodic subscription.
* Refinements to operational considerations and guidance based on
experimental results and real-world deployment experience.
2. Solution Overview
2.1. Adaptive Subscription Parameters
Adaptive subscription can be implemented using either dynamic or
configured subscription. Regardless of the type of adaptive
subscription, triggered updates always occur at the boundaries of
specified time intervals when the corresponding trigger condition is
evaluated to be satisfied. These boundaries can be calculated from
the following parameters:
* "name": represents the unique name of each adaptive period.
Wu, et al. Expires 24 October 2026 [Page 6]
Internet-Draft Adaptive Subscription April 2026
* "eval-expression": represents a standard XPath evaluation
expression (Section 6.4 of [RFC7950]) that is applied against the
targeted data node, which is used to trigger/control the update
interval switching within the server. It follows the rules
defined in Section 3.4 of [XPATH1.0] and contains a comparison of
a targeted node instance to the specific threshold in the XPath
format. Different from selection filter defined in [RFC8641], it
monitors a specific data node instance change and evaluates the
trigger condition associated with the specified threshold value to
be true or false using XPath rules and does not affect the event/
update record output generation from a publisher. The updates are
only pushed as the corresponding period interval when the XPath
expression is evaluated to "true".
The represented expression defined in "eval-expression" is
evaluated in the following XPath context:
- The set of namespace declarations is the set of prefix and
namespace pairs for all YANG modules implemented by the server,
where the prefix is the YANG module name and the namespace is
as defined by the "namespace" statement in the YANG module.
- If the leaf is encoded in XML, all namespace declarations in
scope on the "eval-expression" leaf element are added to the
set of namespace declarations. If a prefix found in the XML is
already present in the set of namespace declarations, the
namespace in the XML is used.
- The set of variable bindings is empty.
- The function library is the core function library defined in
[XPATH1.0] and the function defined in Section 10 of [RFC7950].
- The context node is the root node in the accessible tree which
is the operational state data in the server.
When specified, multiple XPath evaluation criteria inside
"adaptive-periodic" container MUST be mutually exclusive. For the
cases where the "eval-expression" parameter refers to multiple
list/leaf-list instances, XPath abbreviated syntax can be used to
identify a particular instance, e.g., to represent a comparison
for a leaf in a list entry:
/if:interfaces/if:interface[if:name="eth0"]/if:in-errors>1000.
The server MUST convert the XPath evaluation expression defined in
"eval-expression" to a boolean value and internally apply the
"boolean" function defined in Section 4.3 in [XPATH1.0] if the
Wu, et al. Expires 24 October 2026 [Page 7]
Internet-Draft Adaptive Subscription April 2026
evaluated result is not a boolean value. It MUST evaluate to
"false" if the target node instance to be compared is deleted.
Only if the XPath expression is evaluated to "true", does the
publisher switch to the corresponding period with which push
updates are reported.
* "eval-interval": defines how often the XPath condition expression
as defined in "eval-expression" is evaluated to decide whether to
switch to another period interval. If an "eval-interval" is not
provided, then the "eval-interval" is set with the minimum time
interval that the server is able to detect whenever changes to the
targeted data node occur. The selection of this minimum time
interval is implementation-specific and may vary dynamically based
on the server's available resources (e.g., memory, CPU).
* "period": defines the duration between push updates, in units of
0.01 seconds. The "period" has the same definition as the
yp:period for periodic subscription defined in [RFC8641], while it
must be present with the "eval-expression" parameter so that
update interval can be switched based on trigger conditions
indicated by the "eval-expression" parameter;
* "anchor-time": update intervals fall on the points in time that
are a multiple of a "period" from an "anchor-time". If an
"anchor-time" is not provided, then the "anchor-time" MUST be set
with the creation time of the initial update record inside each
periodic timeframe. The "anchor-time" parameter, together with
the "eval-interval" value, specifies when the initial update is to
be pushed within each adaptive periodic timeframe.
Note that the adaptive subscription may not be supported by every
YANG datastore node. The solution presented in this document
augments the "ietf-notification-capabilities" YANG module defined in
[RFC9196] to enable a subscriber to discover adaptive subscription
capabilities. A publisher MAY decide to simply reject an adaptive
subscription with "adaptive-unsupported" (defined in Section 2.2) if
the subscription contains selected data nodes for which adaptive
subscription is not supported.
2.2. RPC Failures
RPC error responses from the publisher are used to indicate a
rejection of an RPC for any reason. In addition to the RPC failures
defined in [RFC8639] and [RFC8641], this document introduces
following RPC errors for "establish-subscription" and "modify-
subscription" RPCs.
Wu, et al. Expires 24 October 2026 [Page 8]
Internet-Draft Adaptive Subscription April 2026
establish-subscription
-----------------------------
adaptive-unsupported
xpath-evaluation-unsupported
evaluation-interval-unsupported
multi-xpath-criteria-conflict
modify-subscription
-----------------------------
xpath-evaluation-unsupported
evaluation-interval-unsupported
multi-xpath-criteria-conflict
The "adaptive-unsupported" RPC error is used to indicate that the
adaptive subscription is not supported for the targeted set of data
nodes that are selected by the filter.
The "xpath-evaluation-unsupported" RPC error is used to indicate that
a server failed to parse syntax defined in "eval-expression". The
failure can be caused by either a syntax error or some XPath 1.0
syntax not supported against the specific data node. The "error-
message" should provide further details to help operators identify
the exact cause for troubleshooting purposes.
The "evaluation-interval-unsupported" RPC error is used to indicate
that the requested XPath evaluation interval represented by "eval-
interval" is too short. Hints suggesting alternative intervals may
be returned as supplementary information.
The "multi-xpath-criteria-conflict" error is used to indicate that
the multiple XPath evaluation criteria represented by "eval-
expression" are evaluated as conflicting, i.e., more than one
condition expressions may be evaluated to "true" at the same time.
Refer to Appendix C.3 for some examples of how the above RPC errors
can be returned.
Note that existing RPC errors defined in [RFC8639] and [RFC8641] are
still supported by this document. For example, if any configured
period for adaptive subscription is not supported by the publisher, a
"period-unsupported" error response could be used.
2.3. Subscription State Change Notifications
This document reuses subscription state change notifications and
mechanisms from [RFC8639] and [RFC8641]. Notifications
"subscription-started" and "subscription-modified" have been
augmented to include the adaptive subscription specific parameters.
Wu, et al. Expires 24 October 2026 [Page 9]
Internet-Draft Adaptive Subscription April 2026
2.4. Notifications for Adaptive Subscribed Content
This document also defines a new subscription state change
notification called "adaptive-period-update", to indicate that an
adaptive subscription period interval has been switched based on its
trigger condition. Similar to subscription state change
notifications defined in [RFC8639], the adaptive period update
notification cannot be dropped or filtered out, it cannot be stored
in replay buffers, and it is delivered only to impacted receivers of
a subscription. The identification of the adaptive update
notification is easy to separate from other notification messages
using the YANG extension "subscription-state-notification" defined in
[RFC8639]. This extension tags a notification as a subscription
state change notification.
The elements in the "adaptive-period-update" notification include:
* A subscription ID of the subscription for which the update record
was generated.
* A "period" that defines the duration between push updates, the
period can be changed based on trigger conditions.
* A "period-update-time" that refers to the timestamp when the
server switched to another period interval because the evaluated
"eval-expression" result changed.
* A chunk of data defined as an anydata node [RFC7950] called
"satisfied-criteria-data" to include the instance nodes and values
specified in "eval-expression" that satisfy the condition and thus
trigger the period interval switching within the server. This
node could be useful for troubleshooting.
* A selection filter to identify YANG nodes of interest in a
datastore. Filter contents are specified via a reference to an
existing filter or via an in-line definition for only that
subscription based on XPath Section 6.4 of [RFC7950] evaluation
criteria. Referenced filters allow an implementation to avoid
evaluating filter acceptability during a dynamic subscription
request. The "case" statement differentiates the options. Note
that filter contents are not affected by the "eval-expression"
parameter defined by the update trigger.
Wu, et al. Expires 24 October 2026 [Page 10]
Internet-Draft Adaptive Subscription April 2026
3. Adaptive Subscription Data Model
This document defines a YANG module named "ietf-adaptive-
subscription" which augments the "update-trigger" choice defined in
the "ietf-yang-push" module [RFC8641] with subscription configuration
parameters that are specific to a subscriber's adaptive subscription.
In addition to subscription state notifications defined in [RFC8639]
and notifications for subscribed content defined in [RFC8641], "ietf-
adaptive-subscription" module also defines "adaptive-period-update"
notification to report the update interval change.
Additionally, it augments the "ietf-notification-capabilities" module
defined in [RFC9196] so that the adaptive subscription capabilities
could be discovered beforehand.
3.1. YANG Tree Diagram
The following tree diagrams [RFC8340] provide an overview of the data
model for "ietf-adaptive-subscription" module.
module: ietf-adaptive-subscription
augment /sn:subscriptions/sn:subscription/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+--rw adaptive-periodic
+--rw periodic* [name]
+--rw name string
+--rw eval-expression yang:xpath1.0
+--rw eval-interval? yp:centiseconds
+--rw period yp:centiseconds
+--rw anchor-time? yang:date-and-time
augment /sn:establish-subscription/sn:input/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periodic
+-- periodic* [name]
+-- name string
+-- eval-expression yang:xpath1.0
+-- eval-interval? yp:centiseconds
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sn:modify-subscription/sn:input/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periodic
+-- periodic* [name]
+-- name string
+-- eval-expression yang:xpath1.0
+-- eval-interval? yp:centiseconds
+-- period yp:centiseconds
Wu, et al. Expires 24 October 2026 [Page 11]
Internet-Draft Adaptive Subscription April 2026
+-- anchor-time? yang:date-and-time
augment /sn:subscription-started/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periodic
+-- periodic* [name]
+-- name string
+-- eval-expression yang:xpath1.0
+-- eval-interval? yp:centiseconds
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sn:subscription-modified/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periodic
+-- periodic* [name]
+-- name string
+-- eval-expression yang:xpath1.0
+-- eval-interval? yp:centiseconds
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sysc:system-capabilities/notc:subscription-capabilities:
+--ro adaptive-notifications-supported? notification-support
augment /sysc:system-capabilities/sysc:datastore-capabilities
/sysc:per-node-capabilities
/notc:subscription-capabilities:
+--ro adaptive-notifications-supported? notification-support
notifications:
+---n adaptive-period-update {adaptive-subscription}?
+--ro id?
| sn:subscription-id
+--ro period yp:centiseconds
+--ro period-update-time?
| yang:date-and-time
+--ro satisfied-criteria-data? <anydata>
+--ro datastore identityref
+--ro (selection-filter)?
+--:(by-reference)
| +--ro selection-filter-ref
| selection-filter-ref
+--:(within-subscription)
+--ro (filter-spec)?
+--:(datastore-subtree-filter)
| +--ro datastore-subtree-filter? <anydata>
| {sn:subtree}?
+--:(datastore-xpath-filter)
+--ro datastore-xpath-filter? yang:xpath1.0
{sn:xpath}?
Wu, et al. Expires 24 October 2026 [Page 12]
Internet-Draft Adaptive Subscription April 2026
3.2. The "ietf-adaptive-subscription" Module
This YANG module imports modules from [RFC9911],[RFC8639], [RFC8641],
and [RFC9196].
<CODE BEGINS> file "ietf-adaptive-subscription@2026-02-27.yang"
module ietf-adaptive-subscription {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription";
prefix adaps;
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-types {
prefix yang;
reference
"RFC 9911: Common YANG Data Types";
}
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: <https://datatracker.ietf.org/wg/netconf/>
WG List: NETCONF <netconf@ietf.org>
Author: Qin Wu
<mailto:bill.wu@huawei.com>
Wu, et al. Expires 24 October 2026 [Page 13]
Internet-Draft Adaptive Subscription April 2026
Author: Peng Liu
<mailto: liupengyjy@chinamobile.com>
Author: Qiufang Ma
<mailto: maqiufang1@huawei.com>
Author: Wei Wang
<mailto: wangw36@chinatelecom.cn>
Author: Zhixiong Niu
<mailto: Zhixiong.Niu@microsoft.com>";
description
"This module defines an experimental YANG module that
extends YANG-push to enable the subscriber's adaptive
subscriptions to a publisher's event streams with various
different period intervals to report updates.
Copyright (c) 2026 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).
All revisions of IETF and IANA published modules can be
found at the YANG Parameters registry group
(https://www.iana.org/assignments/yang-parameters).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.
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.";
revision 2026-02-27 {
description
"Initial revision";
reference
"RFC XXXX: Adaptive Subscription to YANG Notifications.";
}
feature adaptive-subscription {
description
"This feature indicates that adaptive-subscriptions are
Wu, et al. Expires 24 October 2026 [Page 14]
Internet-Draft Adaptive Subscription April 2026
supported.";
}
identity adaptive-unsupported {
base sn:establish-subscription-error;
description
"Adaptive-subscription is not supported for the targeted set
of objects that are selectable by the filter.";
}
identity xpath-evaluation-unsupported {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
description
"Unable to parse the XPath evaluation criteria defined in
'eval-expression' because of a syntax error or some XPath
1.0 syntax not supported against the specific data node.";
}
identity evaluation-interval-unsupported {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
description
"The requested XPath evaluation interval represented by
'eval-interval' is too short. Hints suggesting alternative
intervals may be returned as supplementary information.";
}
identity multi-xpath-criteria-conflict {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
description
"Multiple XPath evaluation criteria represented by
'eval-expression' are evaluated as a conflict. I.e.,
more than one condition expression is evaluated to
'true'.";
}
grouping adaptive-subscription-modifiable {
description
"This grouping describes the datastore-specific adaptive
subscription conditions that can be changed during the
lifetime of the subscription.";
container adaptive-periodic {
description
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The publisher supports
Wu, et al. Expires 24 October 2026 [Page 15]
Internet-Draft Adaptive Subscription April 2026
to switch to different period intervals adaptively based
on pre-defined condition expressions.";
list periodic {
key "name";
description
"A list of adaptive periods which define a push update
interval and trigger conditions to switch to the update
interval for sending an event record to the subscriber.";
leaf name {
type string;
description
"A name that uniquely identifies an adaptive period
within the same subscription.";
}
leaf eval-expression {
type yang:xpath1.0;
mandatory true;
description
"A standard XPath evaluation expression that is applied
against the targeted data node, which is used to
trigger/control the update interval switching within
the server. The updates are only pushed at the
corresponding period interval when the XPath expression
is evaluated to 'true'.
The expression is evaluated in the following XPath
context:
- The set of namespace declarations is the set of
prefix and namespace pairs for all YANG modules
implemented by the server, where the prefix is the
YANG module name and the namespace is as defined by
the 'namespace' statement in the YANG module.
- If the leaf is encoded in XML, all namespace
declarations in scope on the 'eval-expression' leaf
element are added to the set of namespace
declarations. If a prefix found in the XML is
already present in the set of namespace
declarations, the namespace in the XML is used.
- The set of variable bindings is empty.
- The function library is the core function library
defined in XPath1.0 and the functions defined in
Section 10 in RFC 7950.
- The context node is the root node in the accessible
tree which is the operational state data in the
Wu, et al. Expires 24 October 2026 [Page 16]
Internet-Draft Adaptive Subscription April 2026
server.";
reference
"XML Path Language (XPath) Version 1.0
(https://www.w3.org/TR/1999/REC-xpath-19991116)
RFC 7950: The YANG 1.1 Data Modeling Language,
Section 10";
}
leaf eval-interval {
type yp:centiseconds;
description
"How often the XPath condition expression represented
by 'eval-expression' is evaluated to decide whether
to switch to another period interval, in units of 0.01
seconds. If this parameter is not provided, it is set
with the minimum time interval that the server is able
to detect whenever changes to the targeted data node
occur.";
}
leaf period {
type yp:centiseconds;
mandatory true;
description
"Duration of time that should occur between periodic
push updates, in units of 0.01 seconds.";
}
leaf anchor-time {
type yang:date-and-time;
description
"Designates a timestamp before or after which a series
of periodic push updates is determined. The next
update will take place at a point in time that is a
multiple of a period from the 'anchor-time'.
For example, for an 'anchor-time' that is set for the
top of a particular minute and a period interval of a
minute, updates will be sent at the top of every
minute that this subscription is active.";
}
}
}
}
augment "/sn:subscriptions/sn:subscription/yp:update-trigger" {
description
"This augmentation adds additional subscription parameters
that apply specifically to adaptive subscription.";
case adaptive-periodic {
if-feature "adaptive-subscription";
description
Wu, et al. Expires 24 October 2026 [Page 17]
Internet-Draft Adaptive Subscription April 2026
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The periodicity of
these notifications are determined by adaptive criteria.";
uses adaptive-subscription-modifiable;
}
}
augment "/sn:establish-subscription/sn:input/yp:update-trigger" {
description
"This augmentation adds additional establish-subscription
parameters that apply specifically to datastore updates to
RPC input.";
case adaptive-periodic {
if-feature "adaptive-subscription";
description
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The periodicity of
these notifications are determined by adaptive criteria.";
uses adaptive-subscription-modifiable;
}
}
augment "/sn:modify-subscription/sn:input/yp:update-trigger" {
description
"This augmentation adds additional modify-subscription
parameters that apply specifically to datastore updates to
RPC input.";
case adaptive-periodic {
if-feature "adaptive-subscription";
description
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The periodicity of
these notifications are determined by adaptive criteria.";
uses adaptive-subscription-modifiable;
}
}
augment "/sn:subscription-started/yp:update-trigger" {
description
"This augmentation adds additional adaptive subscription
parameters to the notification that a subscription has
started.";
case adaptive-periodic {
if-feature "adaptive-subscription";
description
Wu, et al. Expires 24 October 2026 [Page 18]
Internet-Draft Adaptive Subscription April 2026
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The periodicity of
these notifications are determined by adaptive criteria.";
uses adaptive-subscription-modifiable;
}
}
augment "/sn:subscription-modified/yp:update-trigger" {
description
"This augmentation adds additional adaptive subscription
parameters to the notification that a subscription has been
modified.";
case adaptive-periodic {
if-feature "adaptive-subscription";
description
"The publisher is requested to periodically notify the
receiver regarding the current values of the datastore
as defined by the selection filter. The periodicity of
these notifications are determined by adaptive criteria.";
uses adaptive-subscription-modifiable;
}
}
notification adaptive-period-update {
if-feature "adaptive-subscription";
sn:subscription-state-notification;
description
"This notification is sent to indicate that an adaptive
subscription period interval has been switched based on
its triggered condition.";
leaf id {
type sn:subscription-id;
description
"This references the subscription that drove the
notification to be sent.";
}
leaf period {
type yp:centiseconds;
mandatory true;
description
"New duration of time that should occur between periodic
push updates, in units of 0.01 seconds.";
}
leaf period-update-time {
type yang:date-and-time;
description
"The timestamp when the server switched to another period
Wu, et al. Expires 24 October 2026 [Page 19]
Internet-Draft Adaptive Subscription April 2026
interval because the evaluated 'eval-expression' expression
result changed.";
}
anydata satisfied-criteria-data {
description
"The corresponding instance nodes and values specified in
'eval-expression' that satisfied the condition and thus
triggered the update interval switching within the server.";
}
uses yp:datastore-criteria {
refine "selection-filter/within-subscription" {
description
"Specifies the selection filter and where it originated
from. If the 'selection-filter-ref' is populated, the
filter in the subscription came from the 'filters'
container. Otherwise, it is populated in-line as part
of the subscription itself.";
}
}
}
grouping adaptive-subscription-capabilities {
description
"Capabilities related to adaptive subscription and
notification.";
typedef notification-support {
type bits {
bit config-changes {
description
"The publisher is capable of sending
notifications for 'config true' nodes for the
relevant scope and subscription type.";
}
bit state-changes {
description
"The publisher is capable of sending
notifications for 'config false' nodes for the
relevant scope and subscription type.";
}
}
description
"Type for defining whether 'on-change' or
'periodic' notifications are supported for all data nodes,
'config false' data nodes, 'config true' data nodes, or
no data nodes.
The bits config-changes or state-changes have no effect
when they are set for a datastore or for a set of nodes
Wu, et al. Expires 24 October 2026 [Page 20]
Internet-Draft Adaptive Subscription April 2026
that does not contain nodes with the indicated config
value. In those cases, the effect is the same as if no
support was declared. One example of this is indicating
support for state-changes for a candidate datastore that
has no effect.";
}
leaf adaptive-notifications-supported {
type notification-support;
description
"Specifies whether the publisher is capable of sending
'adaptive' notifications for the selected data nodes,
including any subtrees that may exist below them.";
}
}
augment "/sysc:system-capabilities"
+ "/notc:subscription-capabilities" {
description
"Add system level capabilities of adaptive subscription.";
uses adaptive-subscription-capabilities;
}
augment
"/sysc:system-capabilities/sysc:datastore-capabilities/"
+ "sysc:per-node-capabilities/notc:subscription-capabilities" {
description
"Add node-level capabilities of adaptive subscription.";
uses adaptive-subscription-capabilities;
}
}
<CODE ENDS>
4. IANA Considerations
4.1. Updates to the IETF XML Registry for New YANG Module
IANA is requested to register the following URI in the "ns" registry
within the "IETF XML Registry" group [RFC3688].
---------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
---------------------------------------------------------------------
Wu, et al. Expires 24 October 2026 [Page 21]
Internet-Draft Adaptive Subscription April 2026
4.2. Updates to the YANG Module Names Registry for New YANG Module
IANA is requested to register the following YANG module in the "YANG
Module Names" registry [RFC6020] within the "YANG Parameters"
registry group.
---------------------------------------------------------------------
Name: ietf-adaptive-subscription
Maintained by IANA? N
Namespace: urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription
Prefix: adaps
Reference: RFC XXXX
---------------------------------------------------------------------
5. Operational Considerations
5.1. XPath Complexity Evaluation
YANG-Push subscriptions [RFC8641] specify selection filters to
identify targeted YANG datastore nodes and/or datastore subtrees for
which updates are to be pushed. In addition, it specifies update
policies which contain conditions that trigger generation and pushing
of new update records. To support a subscriber's adaptive
subscription defined in this document, the trigger condition also
uses similar selection filters to express a standard XPath evaluation
criterion that is applied against the targeted data node(s).
Care must be taken when using an arbitrary complex XPath evaluation
criteria. While well-supported by Section 3.4 of [XPATH1.0], it
could be error-prone, exhaust computational resources, or not fully
implemented by XPath interpreter in real deployments. Some examples
are given below for illustration:
* Applying XPath evaluation criteria on any arbitrary "config true"
and "config false" data nodes;
* Including more than one target data node selection and operation
(e.g., addition, subtraction, division and multiplication) within
a single XPath evaluation criterion;
* Targeting any type of node value in the XPath evaluation
criterion, e.g., string, int64, uint64, and decimal64 types;
* Comparing two node-sets within the XPath evaluation criterion;
* Comparing targeted data of different data types, e.g., one is an
integer, the other is a string.
Wu, et al. Expires 24 October 2026 [Page 22]
Internet-Draft Adaptive Subscription April 2026
As described in Section 6.4 of [RFC7950], Numbers in XPath 1.0 are
IEEE 754 [IEEE754-2008] double-precision floating-point values; some
values of int64, uint64, and decimal64 types cannot be exactly
represented in XPath expressions.
If targeted data to be compared are in different data types, a
conversion function is needed to convert different data types into
numbers.
If both objects in XPath evaluation criteria to be compared are node-
sets, more computation resources are required which adds complexity.
To reduce these complexities, the following implementation and use
principles are RECOMMENDED:
* XPath evaluation criteria are applied against a minimal set of
data nodes in the data model. The minimal set of data nodes can
be advertised using "ietf-notification-capabilities" module
defined in [RFC9196];
* Both targets in the XPath evaluation criterion to be compared are
in the same data type;
* When comparing a numerical leaf or leaf-list node (e.g., signed/
unsigned integer) against a threshold value, use a constant
numeric value in the XPath evaluation criteria.
If a server receives an XPath evaluation criterion with some XPath
syntax unsupported against the specific targeted data node, an RPC
error with "xpath-evaluation-unsupported" MUST be returned. A
mechanism for clients to discover supported XPath capabilities may be
considered in the future as an operational enhancement, pending
implementation experience gathered from this experiment.
5.2. Threshold Selection for XPath Evaluation
Determining the threshold used in an XPath expression criterion can
be challenging for subscribers sometimes. Generally, the selection
of a threshold should be based on the impact of the targeted node on
monitored service/application and experience from deployments. In
extreme cases, setting an excessively high or low threshold may cause
adaptive subscription to degenerate to periodic subscription.
Sometimes the threshold needs to be adjusted during the lifecycle of
an adaptive subscription, depending on factors like historical
fluctuation range, how rapid the targeted value of the node changes,
distribution characteristics of the targeted node value and even the
generated volume of telemetry traffic.
Wu, et al. Expires 24 October 2026 [Page 23]
Internet-Draft Adaptive Subscription April 2026
5.3. Deployment and Monitoring Considerations
Subscribers are recommended to deploy adaptive subscriptions starting
with conservative adaptation parameters (e.g., a minimum supported
"eval-interval" value) to observe system behavior. An improperly
configured adaptive subscription may lead to operational instability.
Care must be taken when designing evaluation expressions. For
example, a high volume of "adaptive-period-update" notification
within a short time window is a primary indicator of oscillation or
unstable evaluation expressions. Other potential failure scenarios
include invalid or unsupported XPath condition expressions, exhausted
system resources, and unsupported period intervals, all of which
could result in RPC errors.
To support operational visibility and troubleshooting, the following
signals are recommended for monitoring:
* The "adaptive-period-update" notification, indicating that an
adaptive subscription period interval has been updated.
* Subscription state change notification, indicating events related
to adaptive subscription management have occurred.
* RPC failures, indicating why a specific adaptive subscription
could not be created or modified.
6. Implementation Status
Note to the RFC Editor: Please remove this section before
publication, as well as the reference to [RFC7942].
This section records the status of known implementations of the
mechanism defined by this specification at the time of posting of
this Internet-Draft, and is based on a proposal described in
[RFC7942]. The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual
implementation here does not imply endorsement by the IETF.
Furthermore, no effort has been spent to verify the information
presented here that was supplied by IETF contributors. This is not
intended as, and must not be construed to be, a catalog of available
implementations or their features. Readers are advised to note that
other implementations may exist.
Wu, et al. Expires 24 October 2026 [Page 24]
Internet-Draft Adaptive Subscription April 2026
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
There is at least one known implementation, the details of which are
as follows.
* Organization: Huawei Technologies Co.,Ltd.
* Implementation: https://github.com/IETF-Hackathon/ietf113-project-
presentations/blob/main/ietf-hackathon-adaptive-subscription.pdf
* Description: gRPC-based adaptive telemetry to collect data from
Access Points (APs) in a campus network.
* Level of maturity: prototype.
* Coverage: The "ietf-adaptive-subscription" module with the
evaluation criteria supporting a comparison of a limited set of
targeted node instances to the threshold in the XPath format.
* Contact: maqiufang1@huawei.com
* Test Scenario: The radio signals of an AP can cover only a limited
area, Wi-Fi roaming is what happens when a wireless client
disconnects from one AP because it receives weak signals (i.e.,
the Received Signal Strength Indicator (RSSI) lower than the
threshold) and connects to another as the client moves from the
coverage area of an AP to that of another AP. One objective of
telemetry in this scenario is to collect the RSSI values of a
specific client as it moves and detect real-time Wi-Fi roaming
events. We also collect the bytes sent from the AP uplink (which
is also identified as "upbytes") so as to detect the possible
uplink congestion. Three data collection ways are evaluated:
- Periodic subscriptions with periods of 2 seconds for RSSI
collection and 1 minute for upbytes collection.
- Periodic subscriptions with periods of 30 seconds for RSSI
collection and 10 minutes for upbytes collection.
- Adaptive subscriptions:
Wu, et al. Expires 24 October 2026 [Page 25]
Internet-Draft Adaptive Subscription April 2026
o For the RSSI collection, if the RSSI value is greater than
or equal to -65 dB, switch to 30 seconds for publication;
otherwise, switch to 2 seconds for publication; threshold
detection occurs every 2 seconds.
o For the upbytes collection, if the upbytes value is greater
than or equal to 60000 bytes, switch to 1 minute for
publication; otherwise, switch to 10 minutes for
publication; threshold detection occurs every minute.
* Implementation experience: The results show adaptive telemetry can
greatly reduce the data volume but still ensure network events can
be captured at the same time. When the specific value does not
reach the threshold, a lower frequency data publication can
greatly reduce the amount of collected data; when it does exceed
the threshold, the device detects the change and switches to a
higher frequency data publication so that sufficient data will not
be missed to diagnose network events. Adaptive subscription can
be served as a compromise between data management resource cost
and data fidelity for network diagnosis. However, the selection
of threshold is crucial to adaptive subscription and should be
based on operational experience and adjusted as needed.
7. Security Considerations
This section is modeled after the template described in [RFC9907].
The "ietf-adaptive-subscription" YANG module defines a data model
that is designed to be accessed via YANG-based management protocols,
such as NETCONF [RFC6241] and RESTCONF [RFC8040]. These YANG-based
management protocols (1) have to use a secure transport layer (e.g.,
SSH [RFC4252], TLS [I-D.ietf-tls-rfc8446bis], and QUIC [RFC9000]) and
(2) have to use mutual authentication.
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.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., "config true", which is the
default). All writable data nodes are likely to be reasonably
sensitive or vulnerable in some network environments. Write
operations (e.g., edit-config) and delete operations to these nodes
without proper protection or authentication can have a negative
effect on network operations. The following subtrees and data nodes
have particular sensitivities/vulnerabilities:
Wu, et al. Expires 24 October 2026 [Page 26]
Internet-Draft Adaptive Subscription April 2026
* "periodic": By modifying this list, an attacker might alter the
updates that are being sent in order to confuse a receiver,
withhold certain updates to be sent to the receiver, and/or
overwhelm a receiver. For example, an attacker might modify the
period with which updates are reported and/or the XPath evaluation
expression, resulting in certain updates not being published or a
high volume of updates being published to exhaust receiver
resources.
This YANG module uses groupings from other YANG modules that define
nodes that may be considered sensitive or vulnerable in network
environments. Refer to the Security Considerations of [RFC8641] for
information as to which nodes may be considered sensitive or
vulnerable in network environments.
There are no particular sensitive RPC or action operations.
8. Contributors
Wei Song
Email: songwei80@huawei.com
Michael Wang
Email: wangzitao@huawei.com
9. Acknowledgments
We would like to thank Rob Wilton, Thomas Graf, Andy Bierman, Michael
Richardson, Henk Birkholz, Chong Feng, Adrian Farrel, Joe Clarke, and
Dhruv Dhody for valuable review on this document, special thanks to
Thomas and Michael for organizing the discussion on several relevant
drafts and reach the common understanding on the concept and ideas.
The authors would also like to thank Michael for providing CHIP/
Matter WI-FI statistics reference.
Thanks to Dhruv Dhody for the OPSDIR review, Joe Clarke for the
YANGDOCTORS review, Yoav Nir for the SECDIR review, and Joseph Touch
for the TSVART review.
Thanks to Mahesh Jethanandani for the careful AD review.
Thanks to Mohamed Boucadair, Andy Newton, Charles Eckel, Christopher
Inacio, Deb Cooley, Éric Vyncke, Gorry Fairhurst, Gunter Van de
Velde, Jim Guichard, Roman Danyliw, and Tommy Jensen for the IESG
review.
10. References
Wu, et al. Expires 24 October 2026 [Page 27]
Internet-Draft Adaptive Subscription April 2026
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
E., and A. Tripathy, "Subscription to YANG Notifications",
RFC 8639, DOI 10.17487/RFC8639, September 2019,
<https://www.rfc-editor.org/info/rfc8639>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/info/rfc8641>.
Wu, et al. Expires 24 October 2026 [Page 28]
Internet-Draft Adaptive Subscription April 2026
[RFC9196] Lengyel, B., Clemm, A., and B. Claise, "YANG Modules
Describing Capabilities for Systems and Datastore Update
Notifications", RFC 9196, DOI 10.17487/RFC9196, February
2022, <https://www.rfc-editor.org/info/rfc9196>.
[RFC9911] Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911,
DOI 10.17487/RFC9911, December 2025,
<https://www.rfc-editor.org/info/rfc9911>.
[XPATH1.0] W3C, "https://www.w3.org/TR/1999/REC-xpath-19991116/", 11
November 1999.
10.2. Informative References
[CHIP] CSA, "Connected Home over IP Specification", April 2021,
<https://csa-iot.org/all-solutions/matter>.
[I-D.ietf-tls-rfc8446bis]
Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", Work in Progress, Internet-Draft, draft-
ietf-tls-rfc8446bis-14, 13 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-tls-
rfc8446bis-14>.
[IEEE754-2008]
IEEE, "IEEE Standard for Floating-Point Arithmetic", DOI
10.1109/IEEESTD.2008.4610935, 2008,
<http://standards.ieee.org/findstds/
standard/754-2008.html>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
Wu, et al. Expires 24 October 2026 [Page 29]
Internet-Draft Adaptive Subscription April 2026
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
<https://www.rfc-editor.org/info/rfc8792>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
[RFC9907] Bierman, A., Boucadair, M., Ed., and Q. Wu, "Guidelines
for Authors and Reviewers of Documents Containing YANG
Data Models", BCP 216, RFC 9907, DOI 10.17487/RFC9907,
March 2026, <https://www.rfc-editor.org/info/rfc9907>.
Appendix A. Use Cases
The use cases presented in this section are for illustrative
purposes.
A.1. Wireless Network Performance Monitoring
Wireless signal strength is a critical factor in determining the
quality and reliability of a wireless network connection. In
practical scenarios, when the wireless signal strength drops below a
specific threshold, the network may experience issues such as
increased latency, packet loss, or even disconnections, which would
require more frequent monitoring of network and service performance
metrics to detect anomalies in a timely manner. Conversely, when the
wireless signal strength exceeds a specific threshold, indicating a
stable and strong connection, the data streaming rate can be reduced
to a reasonable value to help conserve network bandwidth and
computational resources.
To optimize the process, adaptive subscription can be employed. When
the wireless signal strength falls below a configured threshold, the
subscribed data can be streamed at a higher rate to capture
potentially important data and events that might indicate continuous
service degeneration or anomalies; while when the wireless signal
strength crosses a configured threshold, the subscribed data can be
streamed at a lower rate to maintain efficient resource utilization.
Wu, et al. Expires 24 October 2026 [Page 30]
Internet-Draft Adaptive Subscription April 2026
A.2. Reducing Impact on High CPU Utilization
Continuous monitoring of some metrics is essential for maintaining
network and service health, however, this can place a significant
burden on the device's CPU utilization, especially when the device is
running resource-intensive tasks and is overloaded. When the CPU
utilization on the device exceeds a certain high-level value, it is
crucial to manage the network monitoring process in a way that
minimizes its impact on overall system performance.
In such cases, adaptive subscription can dynamically adjust the
period interval with which to report streaming update and help
balance monitoring needs with computational demands. When the CPU
utilization on the device exceeds a certain high-level value, the
subscriber can specify a longer period interval for some less
critical statistics to make room and save more resources.
Conversely, When the CPU utilization falls below a specified
threshold, indicating the device has sufficient idle resources, the
subscriber can revert to a shorter period interval for streaming data
without exhausting the CPU resources at the same time.
Appendix B. Example YANG Module
This section presents an example YANG module so that Appendix C can
give examples of how the YANG module defined in Section 3.2 is used
to perform adaptive subscription. The example YANG module used in
this section represents a Wi-Fi Network Diagnostics data specified in
[CHIP] which can be used by a Node to assist a user or Administrative
Node in diagnosing potential problems.
YANG tree diagram for the "example-wifi-network-diagnostic" module:
Wu, et al. Expires 24 October 2026 [Page 31]
Internet-Draft Adaptive Subscription April 2026
module: example-wifi-network-diagnostic
+--ro server
| +--ro bssid? yang:mac-address
| +--ro security-type? enumeration
| +--ro wifi-version? enumeration
| +--ro channel-num? int8
| +--ro rssi? int8
| +--ro beacon-lost-count? yang:zero-based-counter32
| +--ro beacon-rx-count? yang:zero-based-counter32
| +--ro packet-multicast-rx-count? yang:zero-based-counter32
| +--ro packet-multicast-tx-count? yang:zero-based-counter32
| +--ro packet-unicast-rx-count? yang:zero-based-counter32
| +--ro packet-unicast-tx-count? yang:zero-based-counter32
| +--ro current-max-rate? uint32
| +--ro overrun-count? yang:zero-based-counter32
+--ro events
+--ro event* [name]
+--ro name string
+--ro disconnection? enumeration
+--ro association-failure? enumeration
+--ro connection-status? enumeration
B.1. "example-wifi-network-diagnostic" YANG Module
module example-wifi-network-diagnostic {
yang-version 1;
namespace "http://example.com/yang/wifi-network-diagnostic";
prefix ex-wnd;
import ietf-yang-types {
prefix yang;
}
container server {
config false;
description
"Configuration of the Wi-Fi Server logical entity.";
leaf bssid {
type yang:mac-address;
description
"The MAC address of a wireless access point.";
}
leaf security-type {
type enumeration {
enum unspecified {
value 0;
}
enum none {
Wu, et al. Expires 24 October 2026 [Page 32]
Internet-Draft Adaptive Subscription April 2026
value 1;
}
enum wep {
value 2;
}
enum wpa {
value 3;
}
enum wpa2 {
value 4;
}
enum wpa3 {
value 5;
}
}
description
"The type of Wi-Fi security used. A value of 0
indicate that the interface is not currently
configured or operational.";
}
leaf wifi-version {
type enumeration {
enum 80211a {
value 0;
}
enum 80211b {
value 1;
}
enum 80211g {
value 2;
}
enum 80211n {
value 3;
}
enum 80211ac {
value 4;
}
enum 80211ax {
value 5;
}
}
description
"The highest 802.11 standard version usable
by the Node.";
}
leaf channel-num {
type int8;
description
Wu, et al. Expires 24 October 2026 [Page 33]
Internet-Draft Adaptive Subscription April 2026
"The channel that Wi-Fi communication is currently
operating on. A value of 0 indicates that the interface
is not currently configured or operational.";
}
leaf rssi {
type int8;
description
"The RSSI of the Node's Wi-Fi radio in dBm.";
}
leaf beacon-lost-count {
type yang:zero-based-counter32;
description
"The count of the number of missed beacons the
Node has detected.";
}
leaf beacon-rx-count {
type yang:zero-based-counter32;
description
"The count of the number of received beacons. The
total number of expected beacons that could have been
received during the interval since association matches
the sum of BeaconRxCount and BeaconLostCount. ";
}
leaf packet-multicast-rx-count {
type yang:zero-based-counter32;
description
"The number of multicast packets received by
the Node.";
}
leaf packet-multicast-tx-count {
type yang:zero-based-counter32;
description
"The number of multicast packets transmitted by
the Node.";
}
leaf packet-unicast-rx-count {
type yang:zero-based-counter32;
description
"The number of multicast packets received by
the Node.";
}
leaf packet-unicast-tx-count {
type yang:zero-based-counter32;
description
"The number of multicast packets transmitted by
the Node.";
}
leaf current-max-rate {
Wu, et al. Expires 24 October 2026 [Page 34]
Internet-Draft Adaptive Subscription April 2026
type uint32;
description
"The current maximum PHY rate of transfer of
data in bytes-per-second.";
}
leaf overrun-count {
type yang:zero-based-counter32;
description
"The number of packets dropped either at ingress or
egress, due to lack of buffer memory to retain all
packets on the ethernet network interface. The
OverrunCount attribute is reset to 0 upon a
reboot of the Node.";
}
}
container events {
config false;
description
"Configuration of WI-FI Network Diagnostic events.";
list event {
key "name";
description
"The list of event sources configured on the
server.";
leaf name {
type string;
description
"The unique name of an event source.";
}
leaf disconnection {
type enumeration {
enum de-authenticated {
value 1;
}
enum dis-association {
value 2;
}
}
description
"A Node's Wi-Fi connection has been disconnected as a
result of de-authenticated or dis-association and
indicates the reason.";
}
leaf association-failure {
type enumeration {
enum unknown {
value 0;
}
Wu, et al. Expires 24 October 2026 [Page 35]
Internet-Draft Adaptive Subscription April 2026
enum association-failed {
value 1;
}
enum authentication-failed {
value 2;
}
enum ssid-not-found {
value 3;
}
}
description
"A Node has attempted to connect, or reconnect, to
a Wi-Fi access point, but is unable to successfully
associate or authenticate, after exhausting all
internal retries of its supplicant.";
}
leaf connection-status {
type enumeration {
enum connected {
value 1;
}
enum notconnected {
value 2;
}
}
description
"A Node's connection status to a Wi-Fi network has
changed. Connected, in this context, means that
a Node acting as a Wi-Fi station is successfully
associated to a Wi-Fi Access Point.";
}
}
}
}
Appendix C. Adaptive Subscription and Notification Example
The examples within this document use the normative YANG module
"ietf-adaptive-subscription" defined in Section 3.2 and the non-
normative example YANG module "example-wifi-network-diagnostic"
defined in Appendix B.1.
This section shows some typical adaptive subscription and
notification message exchanges.
Wu, et al. Expires 24 October 2026 [Page 36]
Internet-Draft Adaptive Subscription April 2026
C.1. Configured Subscription Example
The client configures adaptive subscription policy parameters on the
server. The adaptive subscription configuration parameters require
the server to support two update intervals (i.e., 5 seconds, 20
seconds) and report updates every 20 seconds if the RSSI value is
greater than or equal to -65 dB; If the RSSI value is less than -65
dB, switch to 5 seconds period value to report updates. The server
compares the rssi value with -65 dB every 2 seconds. Figure 1
specifies an example of configured subscription with the <edit-
config> operation.
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="101">
<edit-config>
<target>
<running/>
</target>
<config>
<subscriptions
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<subscription>
<id>1011</id>
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex-wnd="http://example.com/yang/wifi-network-diagnostic">
/ex-wnd:server
</yp:datastore-xpath-filter>
<adaps:adaptive-periodic
xmlns:adaps="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
<adaps:periodic>
<adaps:name>adaptive-period-1</adaps:name>
<adaps:eval-expression>
/ex-wnd:server/ex-wnd:rssi<-65
</adaps:eval-expression>
<adaps:eval-interval>200</adaps:eval-interval>
<adaps:period>500</adaps:period>
<adaps:anchor-time>2025-04-11T08:00:00Z</adaps:anchor-time>
</adaps:periodic>
<adaps:periodic>
<adaps:name>adaptive-period-2</adaps:name>
<adaps:eval-expression>
/ex-wnd:server/ex-wnd:rssi>-65
</adaps:eval-expression>
<adaps:eval-interval>200</adaps:eval-interval>
Wu, et al. Expires 24 October 2026 [Page 37]
Internet-Draft Adaptive Subscription April 2026
<adaps:period>2000</adaps:period>
<adaps:anchor-time>2025-04-11T08:00:00Z</adaps:anchor-time>
</adaps:periodic>
</adaps:adaptive-periodic>
<receivers>
<receiver>
<name>host.example.com</name>
</receiver>
</receivers>
</subscription>
</subscriptions>
</config>
</edit-config>
</rpc>
Figure 1: An Example of Configured Subscription
C.2. Dynamic Subscription Example
Alternatively, the subscriber may send an "establish-subscription"
RPC with the parameters listed in Section 2.1 to request the creation
of an adaptive subscription. The adaptive subscription configuration
parameters require the server to report updates every 5 seconds if
the RSSI value is less than -65 dB; If the RSSI value is greater than
or equal to -65 dB, switch to 20 seconds period value. The server
compares the RSSI value with -65 dB every 2 seconds. Figure 2
specifies an example of the "establish-subscription" RPC request.
Wu, et al. Expires 24 October 2026 [Page 38]
Internet-Draft Adaptive Subscription April 2026
<netconf:rpc message-id="101"
xmlns:netconf="urn:ietf:params:xml:ns:netconf:base:1.0">
<establish-subscription
xmlns="urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex-wnd="http://example.com/yang/wifi-network-diagnostic">
/ex-wnd:server
</yp:datastore-xpath-filter>
<adaps:adaptive-periodic
xmlns:adaps="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
<adaps:periodic>
<adaps:name>adaptive-period-1</adaps:name>
<adaps:eval-expression>
/ex-wnd:server/ex-wnd:rssi<-65
</adaps:eval-expression>
<adaps:eval-interval>200</adaps:eval-interval>
<adaps:period>500</adaps:period>
<adaps:anchor-time>2025-04-11T08:00:00Z</adaps:anchor-time>
</adaps:periodic>
<adaps:periodic>
<adaps:name>adaptive-period-2</adaps:name>
<adaps:eval-expression>
/ex-wnd:server/ex-wnd:rssi>-65
</adaps:eval-expression>
<adaps:eval-interval>200</adaps:eval-interval>
<adaps:period>2000</adaps:period>
<adaps:anchor-time>2025-04-11T08:00:00Z</adaps:anchor-time>
</adaps:periodic>
</adaps:adaptive-periodic>
</establish-subscription>
</netconf:rpc>
Figure 2: An Example of Dynamic Subscription
C.3. Error Response Examples
C.3.1. "xpath-evaluation-unsupported" error response example
If the subscriber has authorization to establish the subscription
with a server, but the server had not been able to fully satisfy the
request from the subscriber, the server should send an RPC error
response.
Wu, et al. Expires 24 October 2026 [Page 39]
Internet-Draft Adaptive Subscription April 2026
For instance, if the XPATH 1.0 syntax against the targeted data node
defined in "eval-expression" is not supported by the server' s
implementation, the server returns a reply indicating a failure.
Figure 3 illustrates an example of RPC error response with this.
=============== NOTE: '\' line wrapping per RFC 8792 ================
<?xml version="1.0" encoding="utf-8"?>
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>invalid-value</error-tag>
<error-severity>error</error-severity>
<error-app-tag>
ietf-adaptive-subscription:xpath-evaluation-unsupported
</error-app-tag>
<error-path xmlns:adaps="urn:ietf:params:xml:ns:yang:\
ietf-adaptive-subscription">
/adaps:adaptive-periodic/adaps:periodic/adaps:eval-expression
</error-path>
<error-message xml:lang="en">
Unsupported XPath expression:/ex-wnd:server/ex-wnd:rssi
</error-message>
</rpc-error>
</rpc-reply>
Figure 3: An Example of "xpath-evaluation-unsupported" RPC Error
Response
Since adaptive subscription allows a server to be configured with
multiple different period intervals and corresponding XPath
evaluation criteria to trigger update interval switch in the server,
it may be possible for the server to return multiple <rpc-error>
elements with "xpath-evaluation-unsupported" failure specified by
different error paths. The subscriber can use this information in
future attempts to establish a subscription.
C.3.2. "evaluation-interval-unsupported" error response example
If the requested XPath evaluation interval is too short for the
server to support, the server returns an RPC error indicating the
failure and may provide hints suggesting alternative intervals.
Figure 4 illustrates an example of RPC error response where the
server rejects a request for a 200 centisecond (2 second) evaluation
interval and indicates 300 centiseconds (3 second) as the minimum
supported interval.
Wu, et al. Expires 24 October 2026 [Page 40]
Internet-Draft Adaptive Subscription April 2026
<?xml version="1.0" encoding="utf-8"?>
<rpc-reply message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rpc-error>
<error-type>application</error-type>
<error-tag>invalid-value</error-tag>
<error-severity>error</error-severity>
<error-app-tag>
ietf-adaptive-subscription:evaluation-interval-unsupported
</error-app-tag>
<error-path
xmlns:adaps="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
/adaps:adaptive-periodic/adaps:periodic/adaps:eval-interval
</error-path>
<error-message xml:lang="en">
Minimum supported eval-interval is 300 cs; requested 200 cs
</error-message>
</rpc-error>
</rpc-reply>
Figure 4: An Example of "evaluation-interval-unsupported" RPC
Error Response
The supplementary information including the minimum evaluation
interval that the server can support for the targeted data node is
declared in the "error-message" element.
C.4. "adaptive-period-update" notification example
Suppose initially the RSSI value is below -65dB, the server pushes
updates every 5 seconds starting at 2025-04-11T08:00:00Z and
continuing through 2025-04-11T08:02:05Z. The server evaluates the
RSSI value against -65 dB every 2 seconds and from
2025-04-11T08:02:06Z it detects that the RSSI value exceeds -65 dB
continuously. As the "anchor-time" is set to 2025-04-11T08:00:00Z
for adaptive-period-2, which means updates can only be sent at the
top of every 00, 20, 40 second, the server sends the next update
record at 2025-04-11T08:02:20Z and adjusts the update interval to 20
seconds. Before this, the server generates and sends an "adaptive-
period-update" notification to inform receivers of the new period
interval value. An example of "adaptive-period-update" notification
is indicated in Figure 5.
Wu, et al. Expires 24 October 2026 [Page 41]
Internet-Draft Adaptive Subscription April 2026
<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<eventTime>2025-04-11T08:02:19.33Z</eventTime>
<adaptive-period-update
xmlns="urn:ietf:params:xml:ns:yang:ietf-adaptive-subscription">
<id>1011</id>
<period>2000</period>
<period-update-time>2025-04-11T08:02:20Z</period-update-time>
<satisfied-criteria-data>
<path>/ex-wnd:server/ex-wnd:rssi</path>
<value>-40</value>
</satisfied-criteria-data>
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:ex-wnd="http://example.com/yang/wifi-network-diagnostic">
/ex-wnd:server
</yp:datastore-xpath-filter>
</adaptive-period-update>
</notification>
Figure 5: An Example of "adaptive-period-update" Notification
Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: bill.wu@huawei.com
Peng Liu
China Mobile
32 Xuanwumen West St, Xicheng District
Beijing
Email: liupengyjy@chinamobile.com
Wu, et al. Expires 24 October 2026 [Page 42]
Internet-Draft Adaptive Subscription April 2026
Qiufang Ma
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: maqiufang1@huawei.com
Wei Wang
China Telecom
32 Xuanwumen West St, Xicheng District
Beijing
Email: wangw36@chinatelecom.cn
Zhixiong Niu
Microsoft
Email: Zhixiong.Niu@microsoft.com
Wu, et al. Expires 24 October 2026 [Page 43]