Adaptive Subscription to YANG Notification
draft-ietf-netconf-adaptive-subscription-06
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Qin Wu , Wei Song , Peng Liu , Qiufang Ma , Wei Wang , Zhixiong Niu | ||
| Last updated | 2024-09-11 (Latest revision 2024-06-13) | ||
| Replaces | draft-wang-netconf-adaptive-subscription | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Reviews |
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draft-ietf-netconf-adaptive-subscription-06
NETCONF Working Group Q. Wu
Internet-Draft W. Song
Intended status: Experimental Huawei
Expires: 15 March 2025 P. Liu
China Mobile
Q. Ma
Huawei
W. Wang
China Telecom
Z. Niu
Microsoft
11 September 2024
Adaptive Subscription to YANG Notification
draft-ietf-netconf-adaptive-subscription-06
Abstract
This document defines a YANG data model and associated mechanism that
enable adaptive subscription to YANG notifications. The periodic
update interval for the stream can be set adaptively. 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.
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
* YYYY --> the assigned RFC number for [I-D.ietf-netmod-rfc6991-bis]
* 2024-09-09 --> 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.
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This Internet-Draft will expire on 15 March 2025.
Copyright Notice
Copyright (c) 2024 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/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Adaptive Subscription Parameters . . . . . . . . . . . . 5
2.2. YANG RPC Augmentations . . . . . . . . . . . . . . . . . 7
2.2.1. RPC Failures . . . . . . . . . . . . . . . . . . . . 7
2.3. Subscription State Change Notifications . . . . . . . . . 8
2.4. Notifications for Adaptive Subscribed Content . . . . . . 8
3. XPath Complexity Evaluation . . . . . . . . . . . . . . . . . 9
4. Adaptive Subscription Data Model . . . . . . . . . . . . . . 10
4.1. YANG Tree Diagram . . . . . . . . . . . . . . . . . . . . 11
4.2. The "ietf-adapt-subscription" Module . . . . . . . . . . 12
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
5.1. Updates to the IETF XML Registry . . . . . . . . . . . . 20
5.2. Updates to the YANG Module Names Registry . . . . . . . . 20
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 20
7. Security Considerations . . . . . . . . . . . . . . . . . . . 22
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23
9. Acknowledges . . . . . . . . . . . . . . . . . . . . . . . . 23
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
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10.1. Normative References . . . . . . . . . . . . . . . . . . 23
10.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. Use Cases . . . . . . . . . . . . . . . . . . . . . 26
A.1. Wireless Network Performance Monitoring . . . . . . . . . 26
A.2. Reducing Impact on High CPU Utilization . . . . . . . . . 26
Appendix B. Example YANG Module . . . . . . . . . . . . . . . . 26
B.1. "example-wifi-network-diagnostic" YANG Module . . . . . . 27
Appendix C. Adaptive Subscription and Notification Example . . . 31
C.1. "edit-config" Example . . . . . . . . . . . . . . . . . . 32
C.2. Create Adaptive Subscription Example . . . . . . . . . . 34
C.3. "xpath-evaluation-unsupported" error response example . . 34
C.4. "adaptive-period-update" notification example . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 36
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 (i.e.,
update trigger) to determine when an update record needs to be
generated. Two types of subscription are introduced in [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 update to be triggered whenever a
change in the subscribed information is detected.
However, in some deployments where an increased data collection rate
is used, it becomes more likely that both clients and servers 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. Conversely, if a stream of 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 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.
In addition, when tens of thousands of network devices need to be
managed, frequent follow-up modification requests are prone to
errors.
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This document defines a YANG data model and associated mechanism that
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
* Configuration
* Configured subscription
* Configuration datastore
* Notification message
* Publisher
* Receiver
* Subscriber
* Subscription
* On-change subscription
* Periodic subscription
* Selection filter
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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.
2. Solution Overview
2.1. Adaptive Subscription Parameters
For adaptive subscriptions, triggered updates will occur at the
boundaries of specified time intervals when the corresponding trigger
condition is satisfied. These boundaries can be calculated from the
following parameters:
* "name": represents the name of each adaptive period;
* "xpath-eval-criterion": 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 even/
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".
It is not always trivial for a subscriber to determine the
threshold used in an XPath expression criterion. Sometimes the
threshold needs to be adjusted during the lifecycle of an adaptive
subscription, depending on historical fluctuation range and how
rapid the targeted value of the node changes, distribution
characteristics of the targeted node value or even the generated
volume of telemetry traffic.
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How often the XPath expression criterion is evaluated to decide
whether to switch to another period interval is up to the
publisher's implementation. With minimal delay, the expression
can be evaluated whenever changes to targeted data node occur, or
at the end of each shortest streaming update period. To reduce
the frequency of evaluation, the server can choose to check
targeted node change at every multiple (e.g.,2 or 3) high-
frequency streaming update periods.
The represented expression defined in "xpath-eval-criterion" 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 "xpath-eval-criterion" 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 in RFC 7950.
- The context node is the root node in the accessible tree which
is the operational state data in the server.
For the cases where the "xpath-eval-criterion" 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
"xpath-eval-criterion" to a boolean value and internally apply the
"boolean" function defined in Section 4.3 in [XPATH1.0] if the
evaluated result is not a boolean value. It MUST evaluates 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.
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* "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 an "xpath-eval-criterion" parameter so that
update interval can be switched based on trigger conditions
indicated by the "xpath-eval-criterion" 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.
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 2.2.1)
if the scope of the subscription contains selected data nodes for
which adaptive subscription is not supported.
2.2. YANG RPC Augmentations
Adaptive Subscriptions are established, modified, and deleted using
RPCs from [RFC8639] and [RFC8641]. RPCs "establish-subscription" and
"modify-subscription" have been augmented to include the adaptive
subscription specific parameters, those parameters are the same as
the ones defined in Section 2.1.
2.2.1. 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.
establish-subscription
-----------------------------
adaptive-unsupported
xpath-evaluation-unsupported
multi-xpath-criteria-conflict
modify-subscription
-----------------------------
xpath-evaluation-unsupported
multi-xpath-criteria-conflict
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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 "xpath-eval-criterion".
The failure can be caused by either a syntax error or some XPath 1.0
syntax not supported against the specific data node.
When specified, multiple XPath evaluation criteria inside "adaptive-
periods" container MUST be mutually exclusive. The "multi-xpath-
criteria-conflict" error is used to indicate that the multiple XPath
evaluation criteria represented by "xpath-eval-criterion" are
evaluated as conflicting, i.e., more than one condition expressions
may be evaluated to "true" at the same time.
For an example of how the above RPC errors can be returned, see the
"xpath-evaluation-unsupported" error response illustrated in
Appendix C.3.
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
Subscription state change notifications and mechanisms are reused
from [RFC8639] and [RFC8641]. Notifications "subscription-started"
and "subscription-modified" have been augmented to include the
adaptive subscription specific parameters.
2.4. Notifications for Adaptive Subscribed Content
The adaptive update notification is similar to subscription state
change notifications defined in [RFC8639]. It is inserted into the
sequence of notification messages sent to a particular receiver. As
stated in Section 2.7 of [RFC8639], the adaptive 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 through the use
of 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:
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* a "period" that defines the duration between push updates, the
period can be changed based on trigger conditions.
* a "period-update-time" that designates a timestamp when the server
starts to switch to another period interval because the evaluated
"xpath-eval-criterion" expression result changed.
* 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 "xpath-eval-
criterion" parameter defined by the update trigger.
3. 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).
The following complex implementation and use choices need to be
cautious, although they have already been well supported by the
Section 3.4 of [XPATH1.0]:
* Support XPath evaluation criteria for all "config true" and
"config false" data nodes;
* Support more than one target data node selection and operation
(e.g., addition, subtraction, division and multiplication) in a
single XPath evaluation criterion;
* Support any type of node value in the XPath evaluation criterion,
e.g., string, int64, uint64, and decimal64 types;
* Both objects in the XPath evaluation criterion to be compared are
node-sets;
* Targeted data to be compared are in different data types, e.g.,
one is an integer, the other is a string.
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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 add 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;
* One target to be compared in the XPath evaluation criterion is a
leaf/leaf-list data node with numerical data type (e.g., signed/
unsigned integer) and the other is a numerical threshold value.
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.
4. Adaptive Subscription Data Model
This document defines a YANG data model named "ietf-adapt-
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-
adapt-subscription" module also defines "adaptive-period-update"
notification to report the update interval change.
Additionally, it augments the "ietf-notification-capabilities" data
model defined in [RFC9196] so that the adaptive subscription
capabilities could be discovered beforehand.
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4.1. YANG Tree Diagram
The following tree diagrams [RFC8340] provide an overview of the data
model for "ietf-adapt-subscription" module.
module: ietf-adapt-subscription
augment /sn:subscriptions/sn:subscription/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+--rw adaptive-periods
+--rw adaptive-period* [name]
+--rw name yang:yang-identifier
+--rw xpath-eval-criterion yang:xpath1.0
+--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-periods
+-- adaptive-period* [name]
+-- name yang:yang-identifier
+-- xpath-eval-criterion yang:xpath1.0
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sn:modify-subscription/sn:input/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periods
+-- adaptive-period* [name]
+-- name yang:yang-identifier
+-- xpath-eval-criterion yang:xpath1.0
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sn:subscription-started/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periods
+-- adaptive-period* [name]
+-- name yang:yang-identifier
+-- xpath-eval-criterion yang:xpath1.0
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sn:subscription-modified/yp:update-trigger:
+--:(adaptive-periodic) {adaptive-subscription}?
+-- adaptive-periods
+-- adaptive-period* [name]
+-- name yang:yang-identifier
+-- xpath-eval-criterion yang:xpath1.0
+-- period yp:centiseconds
+-- anchor-time? yang:date-and-time
augment /sysc:system-capabilities/notc:subscription-capabilities:
+--ro adaptive-notifications-supported? notification-support
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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 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}?
4.2. The "ietf-adapt-subscription" Module
This YANG module imports modules from [RFC8639], [RFC8641],
[RFC9196], and [I-D.ietf-netmod-rfc6991-bis].
<CODE BEGINS> file "ietf-adapt-subscription@2024-09-09.yang"
module ietf-adapt-subscription {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-adapt-subscription";
prefix as;
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";
}
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import ietf-yang-types {
prefix yang;
reference
"RFC YYYY: 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: <http://tools.ietf.org/wg/netconf>
WG List: <netconf@ietf.org>
Editor: Qin Wu
<mailto:bill.wu@huawei.com>
Editor: Wei Song
<mailto: songwei80@huawei.com>
Editor: Peng Liu
<mailto: liupengyjy@chinamobile.com>
Editor: Qiufang Ma
<mailto: maqiufang1@huawei.com>
Editor: Wei Wang
<mailto: wangw36@chinatelecom.cn>
Editor: Zhixiong Niu
<mailto: Zhixiong.Niu@microsoft.com>";
description
"This module extends the YANG data module defined in
YANG-push to enable the subscriber's adaptive
subscriptions to a publisher's event streams with various
different period intervals to report updates.
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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.
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 2024-09-09 {
description
"Initial revision";
reference
"RFC XXXX: Adaptive Subscription to YANG Notification.";
}
feature adaptive-subscription {
description
"This feature indicates that adaptive-subscriptions are
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
'xpath-eval-criterion' because of a syntax error or some
XPath 1.0 syntax not supported against the specific
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data node.";
}
identity multi-xpath-criteria-conflict {
base sn:establish-subscription-error;
base sn:modify-subscription-error;
description
"Multiple Xpath evaluation criteria represented by
'xpath-eval-criterion' 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-periods {
list adaptive-period {
key "name";
description
"An entry in this list represents an adaptive period
which defines a push update interval and trigger
conditions to switch to the update interval for
sending an event record to the subscriber.";
leaf name {
type yang:yang-identifier;
description
"The name of adaptive period.";
}
leaf xpath-eval-criterion {
type yang:xpath1.0;
mandatory true;
description
"An XPath string, representing a logical expression,
which can contain comparisons of datastore values
and logical operations in the XPath format.";
}
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;
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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.";
}
}
description
"Container for adaptively periodic subscription.";
}
}
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
"Defines adaptively periodic case for sending an event
record to the subscriber.";
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
"Defines adaptively periodic case for sending an event
record to the subscriber.";
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
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RPC input.";
case adaptive-periodic {
if-feature adaptive-subscription;
description
"Defines adaptively periodic case for sending an event
record to the subscriber.";
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
"Defines adaptively periodic case for sending an event
record to the subscriber.";
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
"Defines adaptively periodic case for sending an event
record to the subscriber.";
uses adaptive-subscription-modifiable;
}
}
notification adaptive-period-update {
if-feature adaptive-subscription;
sn:subscription-state-notification;
description
"This notification contains a push update that in turn
contains data subscribed to via a subscription. In the
case of a periodic subscription, this notification is sent
for periodic updates. It can also be used for
synchronization updates of an on-change subscription.
This notification shall only be sent to receivers of a
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subscription. It does not constitute a general-purpose
notification that would be subscribable as part of the
NETCONF event stream by any receiver.";
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
"Designates a timestamp when the server starts to switch
to another period interval because the evaluated 'xpath-
external-eval' expression result changed.";
}
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 {
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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
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>
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5. IANA Considerations
5.1. Updates to the IETF XML Registry
This document registers one URI in the IETF XML registry [RFC3688].
Following the format in [RFC3688], the following registration is
requested to be made:
---------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-adapt-subscription
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
---------------------------------------------------------------------
5.2. Updates to the YANG Module Names Registry
This document registers one YANG module in the YANG Module Names
registry [RFC7950]. Following the format in [RFC6020], the following
registration is requested to be made:
---------------------------------------------------------------------
Name: ietf-adapt-subscription
Namespace: urn:ietf:params:xml:ns:yang:ietf-adapt-subscription
Prefix: as
Reference: RFC XXXX
---------------------------------------------------------------------
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.
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
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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 a demo implementation of gRPC-based adaptive telemetry to
collect data from access points (APs) in a campus network. 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 becuase 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 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:
- 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.
- 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.
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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 disgnose 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. In extreme cases, a too hight or low threshold
may make adaptive subscription degenerated to periodic subscription.
7. Security Considerations
This section uses the template described in Section 3.7 of
[I-D.ietf-netmod-rfc8407bis].
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. These network management
protocols are required to use a secure transport layer and mutual
authentication, e.g., SSH [RFC6242] without the "none" authentication
option, Transport Layer Security (TLS) [RFC8446] with mutual X.509
authentication, and HTTPS with HTTP authentication (Section 11 of
[RFC9110]).
The NETCONF 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). These data nodes may be considered sensitive in some
network environments. Write operations (e.g., edit-config) to these
data nodes without proper protection can have a negative effect on
network operations. Specifically, the following subtrees and data
nodes have particular sensitivities/vulnerabilities:
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* "adaptive-period": By modifying this list, an attacker might alter
the upates 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.
8. Contributors
Thanks Michael Wang, Liang Geng for their major contributions to the
initial modeling and use cases.
Michael Wang
Email: wangzitao@huawei.com
Liang Geng
China Mobile
32 Xuanwumen West St, Xicheng District
Beijing 10053
Email: gengliang@chinamobile.com
9. Acknowledges
We would like to thank Rob Wilton, Thomas Graf, Andy Bierman, Michael
Richardson, Henk Birkholz, Chong Feng, Adrian Farrel 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. Thanks Michael for
providing CHIP/Matter WIFI statistics reference.
10. References
10.1. Normative References
[I-D.ietf-netmod-rfc6991-bis]
Schönwälder, J., "Common YANG Data Types", Work in
Progress, Internet-Draft, draft-ietf-netmod-rfc6991-bis-
16, 7 August 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-netmod-rfc6991-bis-16>.
[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>.
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[RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event
Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008,
<https://www.rfc-editor.org/info/rfc5277>.
[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>.
[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>.
10.2. Informative References
[CHIP] CSA, "Connected Home over IP Specification", April 2021.
[I-D.ietf-netmod-rfc8407bis]
Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
Authors and Reviewers of Documents Containing YANG Data
Models", Work in Progress, Internet-Draft, draft-ietf-
netmod-rfc8407bis-15, 10 September 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-15>.
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[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>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[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>.
[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>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[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>.
[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>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/info/rfc9110>.
[XPATH1.0] W3C, "https://www.w3.org/TR/1999/REC-xpath-19991116/", 11
November 1999.
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Appendix A. Use Cases
A.1. Wireless Network Performance Monitoring
Wireless signal strength determines the quality of wireless network
connection. 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 (e.g.,
continuous service degeneration); while when the wireless signal
strength crosses a configured threshold, the subscribed data can be
streamed at a lower rate.
A.2. Reducing Impact on High CPU Utilization
Frequent monitoring of some metrics could affect the CPU utilization
of the device. When the CPU utilization on the device exceeds a
certain high-level value, it might be desired for the monitoring
service to specify a less rapid period interval for some less-
important statistics to make room and save more resources.
Conversely, When the CPU usage is lower than the specified threshold,
a shorter period interval may be used 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 4.2 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:
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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? int8
| +--ro beacon-rx-count? int8
| +--ro packet-multicast-rx-count? int8
| +--ro packet-multicast-tx-count? int8
| +--ro packet-unicast-rx-count? int8
| +--ro packet-unicast-tx-count? int8
| +--ro current-max-rate? int8
| +--ro overrun-count? int8
+--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 wnd;
import ietf-yang-types {
prefix yang;
}
container server {
config false;
description
"Configuration of the WiFi 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 {
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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
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"The channel that Wi-Fi communication is currently
operating on. A value of 0indicates 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 int8;
description
"The count of the number of missed beacons the
Node has detected.";
}
leaf beacon-rx-count {
type int8;
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 SHOULD
match the sum of BeaconRxCount and BeaconLostCount. ";
}
leaf packet-multicast-rx-count {
type int8;
description
"The number of multicast packets received by
the Node.";
}
leaf packet-multicast-tx-count {
type int8;
description
"The number of multicast packets transmitted by
the Node.";
}
leaf packet-unicast-rx-count {
type int8;
description
"The number of multicast packets received by
the Node.";
}
leaf packet-unicast-tx-count {
type int8;
description
"The number of multicast packets transmitted by
the Node.";
}
leaf current-max-rate {
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type int8;
description
"The current maximum PHY rate of transfer of
data in bytes-per-second.";
}
leaf overrun-count {
type int8;
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 SHALL be reset to 0 upon a
reboot of the Node..";
}
}
container events {
config false;
description
"Configuration of WIFI 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;
}
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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, SHALL mean 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-adapt-subscription" defined in Section 4.2 and the non-
normative example YANG module "example-wifi-network-diagnostic"
defined in Appendix A.1.
This section shows some typical adaptive subscription and
notification message exchanges.
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C.1. "edit-config" 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, 60
seconds) and report updates every 60 seconds if the rssi value is
greater than or equal to -65dB; If the rssi value is less than -65dB,
switch to 5 seconds period value to report updates.
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<rpc message-id="101"
xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<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:wnd="http://example.com/yang/wifi-network-diagnostic">
/wnd:server
</yp:datastore-xpath-filter>
<as:adaptive-periods
xmlns:as="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription">
<as:adaptive-period>
<as:name>adaptive-period-1</as:name>
<as:xpath-eval-criterion>
/wnd:server/wnd:rssi<-65
</as:xpath-eval-criterion>
<as:period>5</as:period>
</as:adaptive-period>
<as:adaptive-period>
<as:name>adaptive-period-2</as:name>
<as:xpath-eval-criterion>
/wnd:server/wnd:rssi>=-65
</as:xpath-eval-criterion>
<as:period>60</as:period>
</as:adaptive-period>
</as:adaptive-periods>
<receivers>
<receiver>
<name>host.example.com</name>
</receiver>
</receivers>
</subscription>
</subscriptions>
</config>
</edit-config>
</rpc>
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C.2. Create Adaptive Subscription Example
The subscriber sends 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 -65dB; If the rssi value is greater than
or equal to -65dB, switch to 60 seconds period value.
<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:wnd="http://example.com/yang/wifi-network-diagnostic">
/wnd:server
</yp:datastore-xpath-filter>
<as:adaptive-periods
xmlns:as="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription">
<as:adaptive-period>
<as:name>adaptive-period-1</as:name>
<as:xpath-eval-criterion>
/wnd:server/wnd:rssi<-65
</as:xpath-eval-criterion>
<as:period>5</as:period>
</as:adaptive-period>
<as:adaptive-period>
<as:name>adaptive-period-2</as:name>
<as:xpath-eval-criterion>
/wnd:server/wnd:rssi>=-65
</as:xpath-eval-criterion>
<as:period>60</as:period>
</as:adaptive-period>
</as:adaptive-periods>
</establish-subscription>
</netconf:rpc>
C.3. "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.
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For instance, if the XPATH 1.0 syntax against the targeted data node
defined in "xpath-eval-criterion" is not supported by the server' s
implementation, the server returns a reply indicating a failure. The
following <rpc-reply> illustrates an example:
<?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-adapt-subscription:xpath-evaluation-unsupported
</error-app-tag>
<error-path
xmlns:wnd="http://example.com/yang/wifi-network-diagnostic">
/wnd:server/wnd:rssi
</error-path>
</rpc-error>
</rpc-reply>
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.4. "adaptive-period-update" notification example
Upon the server switches from the update interval 5 seconds to the
new update interval 60 seconds, before sending event records to
receivers, the "adaptive-period-update" notification should be
generated and sent to the receivers to inform the receivers that the
update interval value is switched to the new value.
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<notification
xmlns="urn:ietf:params:xml:ns:netconf:notification:1.0"
xmlns:yp="urn:ietf:params:xml:ns:yang:ietf-yang-push">
<eventTime>2016-11-21T13:51:00Z</eventTime>
<adaptive-period-update
xmlns="urn:ietf:params:xml:ns:yang:ietf-adapt-subscription">
<id>1011</id>
<period>60</period>
<yp:datastore
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
ds:operational
</yp:datastore>
<yp:datastore-xpath-filter
xmlns:wnd="http://example.com/yang/wifi-network-diagnostic">
/wnd:server
</yp:datastore-xpath-filter>
</adaptive-period-update>
</notification>
Authors' Addresses
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: bill.wu@huawei.com
Wei Song
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: songwei80@huawei.com
Peng Liu
China Mobile
32 Xuanwumen West St, Xicheng District
Beijing
Email: liupengyjy@chinamobile.com
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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
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