RFC 9196
YANG Modules Describing Capabilities for Systems and Datastore Update Notifications
RFC 9196: YANG Modules Describing Capabilities for Systems and Datastore Update Notifications 🎀
- Request for Comments: 9196 🌸
- Who wrote it: B. Lengyel (Ericsson), A. Clemm (Futurewei), and B. Claise (Huawei) 💅
- Stream: IETF, the Internet Engineering Task Force 🦋
- Category: Standards Track ✨
- Date: February 2022 📅
- ISSN: 2070-1721
- Obsoletes and updates: the title block has no Obsoletes or Updates line, so this RFC doesn't list any. 🙈
Abstract
okay so this doc defines two YANG modules, ietf-system-capabilities and ietf-notification-capabilities 🧚
ietf-system-capabilities is basically a placeholder structure for discovering YANG-related system capabilities on servers. You can use it to report capability info from the server at runtime, or at implementation time by using the YANG instance data file format. 💖
ietf-notification-capabilities augments ietf-system-capabilities so it can specify capabilities for "Subscription to YANG Notifications for Datastore Updates" (RFC 8641). 🔥
Status of This Memo
this is an Internet Standards Track document. 👑
It's a product of the Internet Engineering Task Force (IETF), and it represents the consensus of the IETF community. It got public review and was approved for publication by the Internet Engineering Steering Group (IESG). More info on Internet Standards is in Section 2 of RFC 7841. ✨
For the current status of this document, any errata, and how to send feedback, check https://www.rfc-editor.org/info/rfc9196. 💜
Copyright Notice
Copyright (c) 2022 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) as in effect on the date of publication. Please read these carefully, because 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 they are provided without warranty as described in the Revised BSD License. 📜
Table of Contents
1. Introduction
1.1. Terminology
2. Providing System Capability Information
3. Providing YANG-Push Notification Capabilities Information
4. System Capabilities Model
4.1. Tree Diagram
4.2. YANG Module
5. Notification Capabilities Model
5.1. Tree Diagram
5.2. YANG Module
6. Security Considerations
7. IANA Considerations
7.1. The IETF XML Registry
7.2. The YANG Module Names Registry
8. References
8.1. Normative References
8.2. Informative References
Appendix A. Instance Data Example #1
Appendix B. Instance Data Example #2
Acknowledgments
Authors' Addresses1. Introduction ✨
okay so servers and/or publishers often have capabilities. These are values that describe how they behave operationally, and clients need to know about them. The YANG modules in this document make that possible. 💅
We need to publish this capability info because it's part of the API contract between the server and the client. Examples include the maximum size of data that can be stored or transferred, and info about counters (like whether a node supports "on-change" telemetry), etc. Those capabilities usually depend on the vendor's implementation or on the resources available at deployment. A lot of them are specific to the whole system, to individual YANG datastores [RFC8342], to specific parts of the YANG schema, or even to individual data nodes. 🦋
So this doc's goal is to give everyone a common way to represent these capabilities, in a format that is:
- vendor independent, 🌸
- machine readable, and 🤖
- available in an identical format both at implementation time and at runtime. 💖
Implementation-time info matters for Network Management System (NMS) implementers. An NMS that supports notifications needs to know a system's capabilities so it can send "on-change" notifications. If that info isn't documented in a way that's easy for the NMS designer to get, and is only available as instance data from the network node once it's deployed, the NMS implementation gets delayed because it has to wait for the node to be ready. Also, assuming every NMS implementer will have a correctly configured network node to pull data from is kind of a lot to ask, and it may not always be true. (An NMS may need to handle many dozens of network node types. 😭) A fully working NMS is often required before a new network node type can be introduced into a network, so delaying NMS readiness also delays when that new node type can show up. 🙈
Implementation-time info also matters for system integrators. When operators bring a new network node type into their network, they often need to fit it into their own management system. The NMS may have management functions that depend on "on-change" notifications. Operators need to plan their management practices and NMS implementation before they decide to buy that specific node type. Sometimes the decision to buy it even depends on those management possibilities. 🧚
Runtime capability info is needed in these situations:
- for any "purely model-driven" application, e.g., a NETCONF browser. Those apps depend on reading models and capabilities at runtime to support all of the publisher's available functionality. 🍓
- in case the capability might change during runtime, e.g., due to licensing, hardware constraints, etc. 👑
- to check that the capability info provided earlier, at implementation time, is what the publisher has actually implemented. ✅
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 terms "YANG-Push", "on-change subscription", and "periodic subscription" are used as defined in [RFC8641]. 💜
The terms "subscriber", "publisher", and "receiver" are used as defined in [RFC8639]. 🫶
The term "server" is used as defined in [RFC8342]. 🌈
The terms "YANG instance data file format", "instance data", and "instance data set" are used as defined in [RFC9195]. 🎀
This document also defines the following terms:
- Implementation-time information: info about the server's behavior that's made available while the server is being implemented, from a source other than a running server. 🛠️
- Runtime information: info about the server's behavior that's available from the running server through management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. ⭐
2. Providing System Capability Information 💖
okay so capability info is represented by instance data based on one or more "capability-defining YANG modules." This lets a user discover capabilities both at implementation time and at runtime. 🦋
For the implementation-time use case:
- Capabilities SHOULD be provided by the implementer as YANG instance data files complying with [RFC9195]. When they're provided, the file MUST already be available at implementation time, and it must be retrievable in a way that doesn't depend on a live network node, e.g., downloading from a product website. 🌸
For the runtime use case:
- Capabilities SHOULD be available via NETCONF [RFC6241] or RESTCONF [RFC8040] from the live server (the one implementing the publisher) during runtime. Implementations that support changing these capabilities at runtime SHOULD support "on-change" notifications about the system-capabilities container. ✨
The module ietf-system-capabilities provides a placeholder structure that's used to specify any YANG-related system capability. 🧚
The module ietf-notification-capabilities is defined so a publisher can specify capabilities related to "Subscription to YANG Notifications for Datastore Updates" [RFC8641], also known as YANG-Push. It augments ietf-system-capabilities. 🔥
The YANG data models in this document conform to the Network Management Datastore Architecture (NMDA) defined in [RFC8342]. 🌈
3. Providing YANG-Push Notification Capabilities Information 🎀
so here's a specific case: we need to specify capabilities for the YANG-Push functionality. As defined in [RFC8641], a publisher may let subscribers subscribe to updates from a datastore, and it will then push those update notifications to the receiver. Notifications may be sent periodically or "on change" (more or less immediately after each change). 💅
A publisher that supports YANG-Push has a bunch of capabilities defined in [RFC8641], and they're often decided during the publisher's implementation. These include:
- supported (reporting) periods for "periodic" subscriptions. ⏰
- the maximum number of objects that can be sent in an update. 📦
- the set of datastores or data nodes for which "periodic" notification is supported. 🍓
Additional capabilities, if the optional "on-change" feature is supported, include:
- supported dampening periods for "on-change" subscriptions. 🌸
- the set of datastores or data nodes for which "on-change" notification is supported. 💜
Publishers might have some capabilities (or limitations) worth documenting. For example, how many update notifications and how many datastore node updates they can send out in a certain time period. Other publishers might not support "periodic" subscriptions to all datastores. In some cases, a publisher that supports "on-change" notifications won't be able to push updates for some object types "on change." The reasons might be that the datastore node's value changes frequently (e.g., an in-octet counter), that small object changes are frequent and irrelevant to the receiver (e.g., a temperature gauge changing 0.1 degrees within a predetermined and acceptable range), or that the implementation just can't do on-change notification for a particular object. In all of those cases, it's important for subscriber applications to have a way to identify which objects support "on-change" notifications and which don't. 🙈
Support for "on-change" notifications does not mean such notifications will be sent for any specific data node, since the ability to do so may not exist for every data node. So subscriber/management applications can't rely on the "on-change" functionality unless the subscriber has some way to identify which objects actually support "on-change" notifications. YANG data models are meant to work as an interface contract, and without identifying which data nodes actually support "on-change" notifications, that contract would be incomplete. 🫶
Clients of a server (and subscribers to a publisher, since subscribers are also clients) need a method to gather capability information. 🦋
4. System Capabilities Model ✨
okay so the module ietf-system-capabilities is basically a read-only operational state structure that lets you discover any YANG-related system capability 🔍🦋 it's giving "what can you do?" but make it a data model
This module doesn't hold any capabilities itself 🙈 it's more like a set of augmentation points where capabilities get defined in later YANG modules. ietf-system-capabilities is used by other modules to augment in their specific capability info. Every set of those capabilities MUST be wrapped in a container under the augment statement, so different groups of capabilities stay neatly separated 🗂️💅 those wrapper containers SHALL be augmented at /sysc:system-capabilities and at /sysc:system-capabilities/sysc:datastore-capabilities/sysc:per-node-capabilities.
Capability values can be set at three levels: the system level, the datastore level (by selecting all nodes in the datastore), or for specific data nodes in a specific datastore (and all the subtrees under them) 🌳 And here's the main character moment: values set for a specific datastore or node-set override the values set at the system level 👑
Note: This solution works for both NMDA and non-NMDA systems. On non-NMDA servers, "config false" data is treated as if it were part of the running datastore. 🌸
4.1. Tree Diagram
The tree diagram below [RFC8340] gives you the big-picture view of the data model 🧚
module: ietf-system-capabilities
+--ro system-capabilities
+--ro datastore-capabilities* [datastore]
+--ro datastore -> /yanglib:yang-library/datastore/name
+--ro per-node-capabilities* []
+--ro (node-selection)?
+--:(node-selector)
+--ro node-selector? nacm:node-instance-identifier4.2. YANG Module
okay this YANG module pulls typedefs from [RFC8341] and a reference path from [RFC8525] 💖 here's the full thing:
<CODE BEGINS> file "ietf-system-capabilities@2022-02-17.yang"
module ietf-system-capabilities {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-system-capabilities";
prefix sysc;
import ietf-netconf-acm {
prefix nacm;
reference
"RFC 8341: Network Configuration Access Control Model";
}
import ietf-yang-library {
prefix yanglib;
description
"This module requires ietf-yang-library to be implemented.
Revision 2019-01-04 or a revision derived from it
is REQUIRED.";
reference
"RFC8525: YANG Library";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description
"This module specifies a structure to specify system
capabilities for a server or a publisher. System capabilities
may include capabilities of a NETCONF or RESTCONF server or a
notification publisher.
This module does not contain any specific capabilities; it only
provides a structure where containers containing the actual
capabilities are augmented in.
Capability values can be specified at the system level, at the
datastore level (by selecting all nodes in the datastore), or
for specific data nodes of a specific datastore (and their
contained subtrees).
Capability values specified for a specific datastore or
node-set override values specified on the system/publisher
level.
The same grouping MUST be used to define hierarchical
capabilities supported both at the system level and at the
datastore/data-node level.
To find a capability value for a specific data node in a
specific datastore, the user SHALL:
1) search for a datastore-capabilities list entry for
the specific datastore. When stating a specific capability, the
relative path for any specific capability must be the same
under the system-capabilities container and under the
per-node-capabilities list.
2) If the datastore entry is found within that entry, process
all per-node-capabilities entries in the order they appear in
the list. The first entry that specifies the specific
capability and has a node-selector selecting the specific data
node defines the capability value.
3) If the capability value is not found above and the specific
capability is specified under the system-capabilities container
(outside the datastore-capabilities list), this value shall be
used.
4) If no values are found in the previous steps, the
system/publisher is not capable of providing a value. Possible
reasons are that it is unknown, the capability is changing for
some reason, there is no specified limit, etc. In this case,
the system's behavior is unspecified.
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.
Copyright (c) 2022 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 9196
(https://www.rfc-editor.org/info/rfc9196); see the RFC itself
for full legal notices.";
revision 2022-02-17 {
description
"Initial version";
reference
"RFC 9196: YANG Modules Describing Capabilities for Systems
and Datastore Update Notifications";
}
container system-capabilities {
config false;
description
"System capabilities.
Capability values specified here at the system level
are valid for all datastores and are used when the
capability is not specified at the datastore level
or for specific data nodes.";
/*
* "Augmentation point for system-level capabilities."
*/
list datastore-capabilities {
key "datastore";
description
"Capabilities values per datastore.
For non-NMDA servers/publishers, 'config false' data is
considered as if it were part of the running datastore.";
leaf datastore {
type leafref {
path
"/yanglib:yang-library/yanglib:datastore/yanglib:name";
}
description
"The datastore for which capabilities are defined.
Only one specific datastore can be specified,
e.g., ds:conventional must not be used, as it
represents a set of configuration datastores.";
}
list per-node-capabilities {
description
"Each list entry specifies capabilities for the selected
data nodes. The same capabilities apply to the data nodes
in the subtree below the selected nodes.
The system SHALL order the entries according to their
precedence. The order of the entries MUST NOT change
unless the underlying capabilities also change.
Note that the longest patch matching can be achieved
by ordering more specific matches before less
specific ones.";
choice node-selection {
description
"A method to select some or all nodes within a
datastore.";
leaf node-selector {
type nacm:node-instance-identifier;
description
"Selects the data nodes for which capabilities are
specified. The special value '/' denotes all data
nodes in the datastore, consistent with the path
leaf node on page 41 of [RFC8341].";
reference
"RFC 8341: Network Configuration Access Control Model";
}
}
/*
* "Augmentation point for datastore- or data-node-level
* capabilities."
*/
}
}
}
}
<CODE ENDS>5. Notification Capabilities Model
so the YANG module ietf-notification-capabilities is all about the YANG-Push capability 📡💜 it's the info about what your publisher can actually do with subscriptions
5.1. Tree Diagram
here's the overview tree [RFC8340] 🌈
module: ietf-notification-capabilities
augment /sysc:system-capabilities:
+--ro subscription-capabilities
+--ro max-nodes-per-update? uint32
+--ro periodic-notifications-supported? notification-support
+--ro (update-period)?
| +--:(minimum-update-period)
| | +--ro minimum-update-period? uint32
| +--:(supported-update-period)
| +--ro supported-update-period* uint32
+--ro on-change-supported? notification-support
| {yp:on-change}?
+--ro minimum-dampening-period? uint32
| {yp:on-change}?
+--ro supported-excluded-change-type* union
{yp:on-change}?
augment /sysc:system-capabilities/sysc:datastore-capabilities
/sysc:per-node-capabilities:
+--ro subscription-capabilities
+--ro max-nodes-per-update? uint32
+--ro periodic-notifications-supported? notification-support
+--ro (update-period)?
| +--:(minimum-update-period)
| | +--ro minimum-update-period? uint32
| +--:(supported-update-period)
| +--ro supported-update-period* uint32
+--ro on-change-supported? notification-support
| {yp:on-change}?
+--ro minimum-dampening-period? uint32
| {yp:on-change}?
+--ro supported-excluded-change-type* union
{yp:on-change}?5.2. YANG Module ✨
okay so this is the actual YANG module, bestie 💅 It pulls in the YANG-Push feature and typedefs from [RFC8641] and also imports the "ietf-system-capabilities" module from this document, so it's giving group project 🫶
Here it is, verbatim: 🌸
<CODE BEGINS> file "ietf-notification-capabilities@2022-02-17.yang"
module ietf-notification-capabilities {
yang-version 1.1;
namespace
"urn:ietf:params:xml:ns:yang:ietf-notification-capabilities";
prefix notc;
import ietf-yang-push {
prefix yp;
description
"This module requires ietf-yang-push to be implemented.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates";
}
import ietf-system-capabilities {
prefix sysc;
description
"This module requires ietf-system-capabilities to be
implemented.";
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: <mailto:netconf@ietf.org>
Editor: Balazs Lengyel
<mailto:balazs.lengyel@ericsson.com>";
description
"This module specifies publisher capabilities related to
YANG-Push (RFC 8641).
The module contains:
- a specification of the data nodes that support 'on-change' or
'periodic' notifications.
- capabilities related to the throughput of notification data
that the publisher can support. (Note that for a specific
subscription, the publisher MAY allow only longer periods
or smaller updates depending on, e.g., actual load conditions.)
Capability values can be specified at the system/publisher
level, at the datastore level, or for specific data nodes of
a specific datastore (and their contained subtrees), as defined
in the ietf-system-capabilities module.
If different data nodes covered by a single subscription
have different values for a specific capability, then using
values that are only acceptable for some of these data nodes,
but not for others, may result in the rejection of the
subscription.
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.
Copyright (c) 2022 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 9196
(https://www.rfc-editor.org/info/rfc9196); see the RFC itself
for full legal notices.";
revision 2022-02-17 {
description
"Initial version";
reference
"RFC 9196: YANG Modules Describing Capabilities for Systems
and Datastore Update Notifications";
}
grouping subscription-capabilities {
description
"Capabilities related to YANG-Push subscriptions
and notifications";
container subscription-capabilities {
description
"Capabilities related to YANG-Push subscriptions
and notifications";
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
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 max-nodes-per-update {
type uint32 {
range "1..max";
}
description
"Maximum number of data nodes that can be sent
in an update. The publisher MAY support more data nodes
but SHOULD support at least this number.
May be used to avoid the 'update-too-big' error
during subscription.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates, the 'update-too-big' error/identity";
}
leaf periodic-notifications-supported {
type notification-support;
description
"Specifies whether the publisher is capable of
sending 'periodic' notifications for the selected
data nodes, including any subtrees that may exist
below them.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates, 'periodic' subscription concept";
}
choice update-period {
description
"Supported update period value or values for
'periodic' subscriptions.";
leaf minimum-update-period {
type uint32;
units "centiseconds";
description
"Indicates the minimal update period that is
supported for a 'periodic' subscription.
A subscription request to the selected data nodes with
a smaller period than what this leaf specifies is
likely to result in a 'period-unsupported' error.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates, the period leaf in the ietf-yang-push
YANG module";
}
leaf-list supported-update-period {
type uint32;
units "centiseconds";
description
"Supported update period values for a 'periodic'
subscription.
A subscription request to the selected data nodes with a
period not included in the leaf-list will result in a
'period-unsupported' error.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates, the period leaf in the ietf-yang-push
YANG module";
}
}
leaf on-change-supported {
if-feature "yp:on-change";
type notification-support;
description
"Specifies whether the publisher is capable of
sending 'on-change' notifications for the selected
data nodes and the subtree below them.";
reference
"RFC 8641: Subscription to YANG Notifications for Datastore
Updates, on-change concept";
}
leaf minimum-dampening-period {
if-feature "yp:on-change";
type uint32;
units "centiseconds";
description
"The minimum dampening period supported for 'on-change'
subscriptions for the selected data nodes.
If this value is present and greater than zero,
that implies dampening is mandatory.";
reference
"RFC 8641: Subscription to YANG Notifications for
Datastore Updates, the dampening-period leaf in the
ietf-yang-push YANG module";
}
leaf-list supported-excluded-change-type {
if-feature "yp:on-change";
type union {
type enumeration {
enum none {
value -2;
description
"None of the change types can be excluded.";
}
enum all {
value -1;
description
"Any combination of change types can be excluded.";
}
}
type yp:change-type;
}
description
"The change types that can be excluded in
YANG-Push subscriptions for the selected data nodes.";
reference
"RFC 8641: Subscription to YANG Notifications for Datastore
Updates, the change-type typedef in the ietf-yang-push
YANG module";
}
}
}
augment "/sysc:system-capabilities" {
description
"Add system level capabilities";
uses subscription-capabilities {
refine
"subscription-capabilities/supported-excluded-change-type" {
default "none";
}
}
}
augment "/sysc:system-capabilities/sysc:datastore-capabilities"
+ "/sysc:per-node-capabilities" {
description
"Add datastore and node-level capabilities";
uses subscription-capabilities {
refine
"subscription-capabilities/supported-excluded-change-type" {
default "none";
}
}
}
}
<CODE ENDS>
<CODE ENDS>That's the whole module, no cap the notification side is SO well organised 💜 🦋
6. Security Considerations 🔒
okay bestie, this is the serious part 😭 The YANG modules here define a schema for data that's meant to be reached through network management protocols like NETCONF [RFC6241] or RESTCONF [RFC8040], or used as YANG instance data. On the NETCONF side, the bottom layer is the secure transport layer, and the mandatory-to-implement one is Secure Shell (SSH) [RFC6242]. On the RESTCONF side, the bottom layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446] 🔐✨
The Network Configuration Access Control Model (NACM) [RFC8341] is the bouncer 💅 It lets you restrict particular NETCONF or RESTCONF users to a preconfigured subset of all the available protocol operations and content.
This document sets up a framework for conveying system capability information, and it's giving flexible and extensible 🦋 We don't know every use case yet, but they could be as wide as sharing the minimum update period for periodic subscription updates, and which protocols might be used for those notifications. Now here's the spicy part 🫣 Knowing that kind of value could let an attacker figure out how long unauthorized configuration changes might stay active before anyone notices, and which communication channels could be disrupted to stretch out the period of non-detection. Documents that add capabilities by augmenting this module are encouraged to document the security considerations of their new YANG nodes, following the guidance in BCP 216 [RFC8407] 📝
⚠️ Read-only is the whole vibe here. All protocol-accessible data nodes in augmented modules are read-only and cannot be modified. Access control may be configured to avoid exposing any read-only data that the augmenting module documentation defines as security sensitive. So lock down the sensitive stuff! 🔒
When the data is in file format, the data should be protected against modification or unauthorized access using normal file-handling mechanisms 🗂️ The file-format data also inherits all the security considerations of [RFC9195], which covers extra considerations about read protections and separates data at rest from data in motion. Be careful, bestie 💀
7. IANA Considerations 🌸
7.1. The IETF XML Registry
This document registers the following URIs in the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-system-capabilities
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:ietf-notification-capabilities
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.7.2. The YANG Module Names Registry
This document registers the following YANG modules in the "YANG Module Names" registry [RFC6020] 🧚
name: ietf-system-capabilities
namespace: urn:ietf:params:xml:ns:yang:ietf-system-capabilities
prefix: sysc
reference: RFC 9196
name: ietf-notification-capabilities
namespace: urn:ietf:params:xml:ns:yang:ietf-notification-
capabilities
prefix: notc
reference: RFC 91968. References 📚
8.1. Normative References
Here are the normative references, the ones you absolutely need to read 💜
[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>.
[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>.
[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>.
[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>.
[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>.
[RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC8525, March 2019,
<https://www.rfc-editor.org/info/rfc8525>.
[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>.
[RFC9195] Lengyel, B. and B. Claise, "A File Format for YANG
Instance Data", RFC 9195, DOI 10.17487/RFC9195, February
2022, <https://www.rfc-editor.org/info/rfc9195>.8.2. Informative References
And these are the informative ones, good to know but not required 🦋
[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>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
[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>.Appendix A. Instance Data Example #1 🎀
The following examples use artwork folding [RFC8792] for better formatting, so the long lines don't look messy 🙈
The following instance data example describes the notification capabilities of a hypothetical "acme-router" 🤖 The router implements the running and operational datastores. Every change can be reported "on-change" from the running datastore, but only "config false" nodes and some "config false" data can be reported on-change from the operational datastore. Interface statistics are not reported "on-change"; only two important counters are. Datastore subscription capabilities are not reported "on-change", since they never change on the acme-router during runtime 💖
========== NOTE: '\' line wrapping per RFC 8792) ===========
<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=\
"urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
<name>acme-router-notification-capabilities</name>
<content-schema>
<module>ietf-system-capabilities@2022-02-17</module>
<module>ietf-notification-capabilities@2022-02-17</module>
</content-schema>
<description>Defines the notification capabilities of an
acme-router. The router only has running and operational
datastores. Every change can be reported on-change from the
running datastore, but only "config false" nodes and some
"config false" data can be reported on-change from the
operational datastore. Statistics
are not reported on-change except for two important counters,
where a small dampening period is mandated.
</description>
<content-data>
<system-capabilities \
xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
xmlns:notc=\
"urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<notc:subscription-capabilities>
<notc:minimum-update-period>500</notc:minimum-update-period>
<notc:max-nodes-per-update>2000</notc:max-nodes-per-update>
<notc:minimum-dampening-period>\
100\
</notc:minimum-dampening-period>
<notc:periodic-notifications-supported>\
config-changes state-changes\
</notc:periodic-notifications-supported>
<notc:on-change-supported>\
config-changes state-changes\
</notc:on-change-supported>
<notc:supported-excluded-change-type>\
all\
</notc:supported-excluded-change-type>
</notc:subscription-capabilities>
<datastore-capabilities>
<datastore>ds:operational</datastore>
<per-node-capabilities>
<node-selector>\
/if:interfaces/if:interface[if:name='lo']\
</node-selector>
<notc:subscription-capabilities>
<notc:on-change-supported/>
<notc:periodic-notifications-supported/>
</notc:subscription-capabilities>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>\
/if:interfaces/if:interface/if:statistics/if:in-octets\
</node-selector>
<notc:subscription-capabilities>
<notc:minimum-dampening-period>10
</notc:minimum-dampening-period>
<notc:on-change-supported>\
state-changes\
</notc:on-change-supported>
</notc:subscription-capabilities>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>\
/if:interfaces/if:interface/if:statistics/if:out-octets\
</node-selector>
<notc:subscription-capabilities>
<notc:minimum-dampening-period>10
</notc:minimum-dampening-period>
<notc:on-change-supported>\
state-changes\
</notc:on-change-supported>
</notc:subscription-capabilities>
</per-node-capabilities>
<per-node-capabilities>
<node-selector>\
/if:interfaces/if:interface/if:statistics\
</node-selector>
<notc:subscription-capabilities>
<notc:on-change-supported/>
</notc:subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
</system-capabilities>
</content-data>
</instance-data-set>Figure 1: Notification Capabilities with Settings Specific to the Data Node ✨
Appendix B. Instance Data Example #2 ✨
The examples in this appendix use artwork folding [RFC8792] so they fit nicely on the page 🎀
Okay so this one is a hypothetical "acme-switch" 🦋 It implements the running, candidate, and operational datastores. Every change can be reported "on-change" from the running datastore, nothing can be reported on-change from the candidate datastore, and all "config false" data can be reported on-change from the operational datastore 💅 "Periodic" subscriptions are supported for running and operational, but NOT for candidate datastores 🙈
Here's the instance data. Note the folded lines, where the backslash \ marks a line that got wrapped 🌸
========== NOTE: '\' line wrapping per RFC 8792) ===========<?xml version="1.0" encoding="UTF-8"?>
<instance-data-set xmlns=\
"urn:ietf:params:xml:ns:yang:ietf-yang-instance-data">
<name>acme-switch-notification-capabilities</name>
<content-schema>
<module>ietf-system-capabilities@2022-02-17</module>
<module>ietf-notification-capabilities@2022-02-17</module>
</content-schema>
<description>Notification capabilities of acme-switch.
Acme-switch implements the running, candidate, and operational
datastores. Every change can be reported on-change from the
running datastore, nothing from the candidate datastore and
all "config false" data from the operational datastore. Periodic
subscriptions are supported for running and operational, but not
for candidate datastore.
</description>
<content-data>
<system-capabilities \
xmlns="urn:ietf:params:xml:ns:yang:ietf-system-capabilities" \
xmlns:notc=\
"urn:ietf:params:xml:ns:yang:ietf-notification-capabilities" \
xmlns:ds="urn:ietf:params:xml:ns:yang:ietf-datastores">
<notc:subscription-capabilities>
<notc:minimum-update-period>500</notc:minimum-update-period>
<notc:max-nodes-per-update>2000</notc:max-nodes-per-update>
<notc:minimum-dampening-period>\
100\
</notc:minimum-dampening-period>
<notc:periodic-notifications-supported>\
config-changes state-changes\
</notc:periodic-notifications-supported>
</notc:subscription-capabilities>
<datastore-capabilities>
<datastore>ds:operational</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<notc:subscription-capabilities>
<notc:on-change-supported>\
state-changes\
</notc:on-change-supported>
</notc:subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
<datastore-capabilities>
<datastore>ds:candidate</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<notc:subscription-capabilities>
<notc:on-change-supported/>
<notc:periodic-notifications-supported/>
</notc:subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
<datastore-capabilities>
<datastore>ds:running</datastore>
<per-node-capabilities>
<node-selector>/</node-selector>
<notc:subscription-capabilities>
<notc:on-change-supported>\
config-changes\
</notc:on-change-supported>
</notc:subscription-capabilities>
</per-node-capabilities>
</datastore-capabilities>
</system-capabilities>
</content-data>
</instance-data-set>Figure 2: Notification Capabilities with Datastore-Level Settings
Acknowledgments 🫶
Huge thanks to everyone who gave valuable comments, discussions, and feedback, bestie 💜 We wish to acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Kent Watsen, Eric Voit, Joe Clarke, Martin Bjorklund, Ladislav Lhotka, Qin Wu, Mahesh Jethanandani, Ran Tao, Reshad Rahman, and other members of the Netmod Working Group 👑✨
Authors' Addresses 🎀
Meet the authors! 🧚
Balazs Lengyel
Ericsson
Budapest
Magyar Tudosok korutja 11
1117
Hungary
Email: balazs.lengyel@ericsson.comAlexander Clemm
Futurewei
2330 Central Expressway
Santa Clara, CA 95050
United States of America
Email: ludwig@clemm.orgBenoit Claise
Huawei
George's Court Townsend Street
Dublin 2
Ireland
Email: benoit.claise@huawei.comThat's the whole RFC, bestie! 🌈💖
📦 where this page comes from
- ietf: rfc9196 2022-02
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms