System-defined Configuration
draft-ietf-netmod-system-config-09
| Document | Type | Active Internet-Draft (netmod WG) | |
|---|---|---|---|
| Authors | Qiufang Ma , Qin Wu , Chong Feng | ||
| Last updated | 2024-09-29 | ||
| Replaces | draft-ma-netmod-with-system | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Yang Validation | 0 errors, 0 warnings | ||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | In WG Last Call | |
| Document shepherd | Kent Watsen | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | kent+ietf@watsen.net |
draft-ietf-netmod-system-config-09
NETMOD Q. Ma, Ed.
Internet-Draft Q. Wu
Updates: 8342 (if approved) Huawei
Intended status: Standards Track C. Feng
Expires: 2 April 2025 29 September 2024
System-defined Configuration
draft-ietf-netmod-system-config-09
Abstract
The Network Management Datastore Architecture (NMDA) in RFC 8342
defines several configuration datastores holding configuration. The
contents of these configuration datastores are controlled by clients.
This document introduces the concept of system configuration
datastore holding configuration controlled by the system on which a
server is running. The system configuration can be referenced (e.g.,
leafref) by configuration explicitly created by clients.
This document updates RFC 8342.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 April 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/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
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and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.3. Updates to RFC 8342 . . . . . . . . . . . . . . . . . . . 5
2. Kinds of System Configuration . . . . . . . . . . . . . . . . 5
2.1. Immediately-Present . . . . . . . . . . . . . . . . . . . 5
2.2. Conditionally-Present . . . . . . . . . . . . . . . . . . 6
3. The System Configuration Datastore (<system>) . . . . . . . . 6
4. Conceptual Model of Datastores . . . . . . . . . . . . . . . 7
5. Static Characteristics . . . . . . . . . . . . . . . . . . . 9
5.1. Read-only to Clients . . . . . . . . . . . . . . . . . . 9
5.2. No Impact to <operational> . . . . . . . . . . . . . . . 9
6. Dynamic Behaviors . . . . . . . . . . . . . . . . . . . . . . 9
6.1. May Change via Software Upgrades or Resource Changes . . 9
6.2. Referencing System Configuration . . . . . . . . . . . . 9
6.3. Modifying (Overriding) System Configuration . . . . . . . 10
6.4. Configuring Descendant nodes of System Configuration . . 10
7. Relationships to Other Datastores . . . . . . . . . . . . . . 10
7.1. The "factory-default" Datastore . . . . . . . . . . . . . 10
8. The "ietf-system-datastore" Module . . . . . . . . . . . . . 10
8.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 11
8.2. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 11
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 13
9.2. The "YANG Module Names" Registry . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Example of Dynamic Behaviors . . . . . . . . . . . . 16
A.1. Referencing System-defined Nodes . . . . . . . . . . . . 16
A.2. Modifying a System-instantiated Leaf's Value . . . . . . 22
A.3. Configuring Descendant Nodes of a System-defined Node . . 23
Appendix B. Key Use Cases . . . . . . . . . . . . . . . . . . . 24
B.1. Device Powers On . . . . . . . . . . . . . . . . . . . . 26
B.2. Client Commits Configuration . . . . . . . . . . . . . . 26
B.3. Operator Installs Card into a Chassis . . . . . . . . . . 28
B.4. Client further Commits Configuration . . . . . . . . . . 29
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 31
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
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1. Introduction
The Network Management Datastore Architecture (NMDA) [RFC8342]
defines system configuration as the configuration that is supplied by
the device itself and appears in <operational> when it is in use
(Figure 2 in [RFC8342]).
However, there is a desire to enable a server to better expose the
system configuration, regardless of whether it is in use. For
example, some implementations defines the system configuration which
must be referenced to be active. NETCONF/RESTCONF clients can
benefit from a standard mechanism to retrieve what system
configuration is available on a server.
Some servers allow the descendant nodes of system-defined
configuration to be configured or modified. For example, the system
configuration may contain an almost empty physical interface, while
the client needs to be able to add, modify, or remove a number of
descendant nodes. Some descendant nodes may not be modifiable (e.g.,
the interface "type" set by the system).
This document updates the NMDA defined in [RFC8342] with a read-only
conventional configuration datastore called "system" to expose
system-defined configuration. The solution enables configuration
explicitly created by the clients to reference nodes defined in
<system>, override system-provided values, and configure descendant
nodes of system-defined configuration.
The solution defined in this document requires the use of NMDA for
both clients and servers. Conformance to this document requires NMDA
servers implement the "ietf-system-datastore" YANG module
(Section 8).
1.1. Terminology
This document assumes that the reader is familiar with the contents
of [RFC6241], [RFC7950], [RFC8342], [RFC8407], and [RFC8525] and uses
terminologies from those documents.
The following terms are defined in this document:
system configuration: Configuration that is provided by the system
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itself. System configuration is present in the system
configuration datastore (regardless of whether it is applied or
referenced). It is a different and separate concept from factory
default configuration defined in [RFC8808] (which represents a
preset initial configuration that is used to initialize the
configuration of a server). System configuration may also be
referred to as "system-defined configuration" or "system-provided
configuration" throughout this document.
system configuration datastore: A configuration datastore holding
configuration provided by the system itself. This datastore is
referred to as "<system>".
This document redefines the term "conventional configuration
datastore" in Section 3 of [RFC8342] to add "system" to the list of
conventional configuration datastores:
conventional configuration datastore: One of the following set of
configuration datastores: <running>, <startup>, <candidate>,
<system>, and <intended>. These datastores share a common
datastore schema, and protocol operations allow copying data
between these datastores. The term "conventional" is chosen as a
generic umbrella term for these datastores.
system node: An instance in the data tree that is provided by the
system itself. System node may also be called "system-defined
node" or "system-provided node" throughout this document.
referenced node: A referenced node is one of:
* Targets of leafref values defined via the "path" statement.
* Targets of "instance-identifier" type values.
* Nodes present in an XPath expression of "when" constraints.
* Nodes present in an XPath expression of "must" constraints.
* Nodes defined to satisfy the "mandatory true" constraints.
* Nodes defined to satisfy the "min-elements" constraints.
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1.2. Requirements Language
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.
1.3. Updates to RFC 8342
This document updates RFC 8342 to define a configuration datastore
called "system" to hold system configuration (Section 3), it also
redefines the term "conventional configuration datastore" from
[RFC8342] to add "system" to the list of conventional configuration
datastores.
Configuration in <running> is merged with <system> to create the
contents of <intended> after the configuration transformations (e.g.,
template expansion, removal of inactive configuration defined in
[RFC8342]) have been performed, as described in Section 4.
This document also updates the definition of "intended" origin
metadata annotation identity defined in Section 5.3.4 of [RFC8342].
The "intended" identity of origin value defined in [RFC8342]
represents the origin of configuration provided by <intended>, this
document updates its definition as the origin source of configuration
explicitly provided by <running>, and allows a subset of
configuration in <intended> that flows from <system> yet is not
configured or overridden explicitly in <running> to use "system" as
its origin value.
2. Kinds of System Configuration
This document defines two types of system configuration.
Configuration that is immediately-present and configuration that is
conditionally-present. These types of system configuration are
described in Section 2.1 and Section 2.2, respectively.
2.1. Immediately-Present
Immediately-present refers to system configuration which is generated
in <system> when the device is powered on, irrespective of physical
resource present or not, a special functionality enabled or not. An
example of immediately-present system configuration is an always-
existing loopback interface.
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2.2. Conditionally-Present
Conditionally-present refers to system configuration which is
generated in <system> based on specific conditions being met in a
system. For example, if a physical resource is present (e.g., an
interface card is inserted), the system automatically detects it and
loads associated configuration; when the physical resource is not
present (an interface card is removed), the system configuration will
be automatically cleared. Another example is when a special
functionality is enabled, e.g., when a license or feature is enabled,
specific configuration may be created by the system.
3. The System Configuration Datastore (<system>)
Following guidelines for defining datastores in the Appendix A of
[RFC8342], this document introduces a new datastore resource named
"system" that represents the system configuration. NMDA servers
compliant with this document MUST implement a system configuration
datastore, and they SHOULD also implement <intended>.
* Name: "system".
* YANG modules: all.
* YANG nodes: all "config true" data nodes up to the root of the
tree, generated by the system.
* Management operations: The datastore can be read using network
management protocols such as NETCONF and RESTCONF, but its
contents cannot be changed by manage operations via NETCONF and
RESTCONF protocols.
* Origin: This document does not define any new origin identity.
The "system" identity of origin metadata annotation [RFC7952] is
used to indicate the origin of a data item provided by the system.
* Protocols: YANG-driven management protocols, such as NETCONF and
RESTCONF.
* Defining YANG module: "ietf-system-datastore" (Section 8).
The system configuration datastore doesn't persist across reboots.
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4. Conceptual Model of Datastores
Clients may provide configuration nodes that reference nodes defined
in <system>, override system-provided values, and configure
descendant nodes of system-defined configuration in <running>, as
detailed in Section 6.
To ensure the validity of <intended>, configuration in <running> is
merged with <system> to become <intended>, in which process,
configuration appearing in <running> takes precedence over the same
node in <system>. Since it is unspecified how to merge configuration
before transformations, if <system> or <running> includes
configuration that requires further transformation (e.g., template
expansion, removal of inactive configuration defined in [RFC8342])
before it can be applied, configuration transformations MUST be
performed before <running> is merged with <system>.
Whenever configuration in <system> changes, the server MUST also
immediately update and validate <intended>.
As a result, Figure 2 in Section 5 of [RFC8342] is updated with the
below conceptual model of datastores which incorporates the system
configuration datastore.
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+-------------+ +-----------+
| <candidate> | | <startup> |
| (ct, rw) |<---+ +---->| (ct, rw) |
+-------------+ | | +-----------+
| | | |
+-----------+ | +-----------+ |
| <system> | +------->| <running> |<--------+
| (ct, ro) | | (ct, rw) |
+-----------+ +-----------+
| |
| |
| | // configuration transformations,
+--------------+---------------+ // e.g., removal of nodes marked
| // as "inactive", expansion of
| // templates
v
+------------+
| <intended> | // subject to validation
| (ct, ro) |
+------------+
| // changes applied, subject to
| // local factors, e.g., missing
| // resources, delays
dynamic |
configuration | +-------- learned configuration
datastores -----+ | +-------- default configuration
| | |
v v v
+---------------+
| <operational> | <-- system state
| (ct + cf, ro) |
+---------------+
ct = config true; cf = config false
rw = read-write; ro = read-only
boxes denote named datastores
Figure 1: Architectural Model of Datastores
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Configuration in <system> is undeletable to clients (e.g., a system-
defined list entry can never be removed), even though a node defined
in <system> may be overridden in <running>. If it is desired to
enable a client to delete system configuration, it can be
approximated using <factory-default>, as described in Section 7.1.
If system initializes a value for a particular leaf which is
overridden by the client with a different value in <running>
(Section 6.3), the node in <running> may be removed later, in which
case system-initialized value defined in <system> may still be in use
and appear in <operational>.
5. Static Characteristics
5.1. Read-only to Clients
The system datastore is read-only (i.e., edits towards <system>
directly MUST be denied), though the client may be allowed to provide
configuration that overrides the value of a system-initialized node
(see Section 6.3).
5.2. No Impact to <operational>
This work has no impact to <operational>. Notably, it does not
define any new origin identity as it is able to use the existing
"system" identity defined in Section 5.3.4 of [RFC8342]. <system>
enables system-generated nodes to be defined like configuration,
i.e., made visible to clients in order for being referenced or
configurable prior to present in <operational>. "config false" nodes
are out of scope, hence existing "config false" nodes are not
impacted by this work.
6. Dynamic Behaviors
6.1. May Change via Software Upgrades or Resource Changes
The contents of <system> MAY change dynamically under various
conditions, such as license change, software upgrade, and system-
controlled resources change (see Section 2.2). The updates of system
configuration may be obtained through YANG notifications (e.g., on-
change notification) [RFC8639][RFC8641].
6.2. Referencing System Configuration
Clients may create configuration data in <running> that references
nodes in <system>. Some implementations may define system nodes
solely as a convenience for clients to reference. It is also
possible for the clients to define their customized nodes for
reference.
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Appendix A.1 provides an example of a client referencing system-
defined nodes.
6.3. Modifying (Overriding) System Configuration
In some cases, a server may allow some parts of system configuration
(e.g., a leaf's value) to be modified. Modification of system
configuration is achieved by the client writing configuration data in
<running> that overrides the values of matched configuration nodes at
the corresponding level in <system>. Configurations defined in
<running> take precedence over system configuration nodes in <system>
if the server allows the nodes to be modified. The immutability of
system configuration is defined in [I-D.ietf-netmod-immutable-flag].
Appendix A.2 provides an example of a client overriding a system-
instantiated leaf's value.
6.4. Configuring Descendant nodes of System Configuration
A server may also allow a client to add nodes to a list entry in
<system> by writing those additional nodes in <running>. Those
additional data nodes may not exist in <system> (i.e., an addition
rather than an override).
Appendix A.3 provides an example of a client configuring descendant
nodes of a system-defined node.
7. Relationships to Other Datastores
This section discusses the interesting relationships of <system> to
other datastores known at the time of this writing.
7.1. The "factory-default" Datastore
Any deletable system-provided configuration that is populated as part
of <running> by the system at boot up, without being part of the
contents of a <startup> datastore, must be defined in <factory-
default> [RFC8808], which is used to initialize <running> when the
device is first-time powered on or reset to its factory default
condition.
The <factory-reset> RPC operation can reset <system> to its factory
default contents.
8. The "ietf-system-datastore" Module
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8.1. Data Model Overview
This YANG module defines a new YANG identity named "system" that uses
the "ds: conventional" identity defined in [RFC8342] as its base. A
client can discover the system configuration datastore support on the
server by reading the YANG library information from the operational
state datastore.
The system datastore is defined as a conventional configuration
datastore and shares a common datastore schema with other
conventional datastores.
The following diagram illustrates the relationship amongst the
"identity" statements defined in the "ietf-system-datastore" and
"ietf-datastores" YANG modules:
Identities:
+--- datastore
| +--- conventional
| | +--- running
| | +--- candidate
| | +--- startup
| | +--- system
| | +--- intended
| +--- dynamic
| +--- operational
The diagram above uses syntax that is similar to but not defined in
[RFC8340].
8.2. YANG Module
<CODE BEGINS> file "ietf-system-datastore@2024-09-29.yang"
module ietf-system-datastore {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-system-datastore";
prefix sysds;
import ietf-datastores {
prefix ds;
reference
"RFC 8342: Network Management Datastore Architecture(NMDA)";
}
organization
"IETF NETMOD (Network Modeling) Working Group";
contact
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"WG Web: https://datatracker.ietf.org/wg/netmod/
WG List: NETMOD WG list <mailto:netmod@ietf.org>
Author: Qiufang Ma
<mailto:maqiufang1@huawei.com>
Author: Qin Wu
<mailto:bill.wu@huawei.com>
Author: Chong Feng
<mailto:fengchongllly@gmail.com>";
description
"This module defines a new YANG identity that uses the
ds:conventional identity defined in [RFC8342].
Copyright (c) 2024 IETF Trust and the persons identified
as authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with
or without modification, is permitted pursuant to, and
subject to the license terms contained in, the Revised
BSD License set forth in Section 4.c of the IETF Trust's
Legal Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC
itself for full legal notices.";
revision 2024-09-29 {
description
"Initial version.";
reference
"RFC XXXX: System-defined Configuration";
}
identity system {
base ds:conventional;
description
"This read-only datastore contains the configuration
provided by the system itself.";
}
}
<CODE ENDS>
9. IANA Considerations
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9.1. The "IETF XML" Registry
This document registers two XML namespace URNs in the 'IETF XML
registry', following the format defined in [RFC3688].
URI: urn:ietf:params:xml:ns:yang:ietf-system-datastore
Registrant Contact: The IESG.
XML: N/A, the requested URIs are XML namespaces.
9.2. The "YANG Module Names" Registry
This document registers two module names in the 'YANG Module Names'
registry, defined in [RFC6020].
name: ietf-system-datastore
prefix: sysds
namespace: urn:ietf:params:xml:ns:yang:ietf-system-datatstore
maintained by IANA? N
RFC: XXXX // RFC Ed.: replace XXXX and remove this comment
10. Security Considerations
This section is modeled after the template described in Section 3.7
of [I-D.ietf-netmod-rfc8407bis].
The "ietf-system-datastore" YANG module defines a data model that is
designed to be accessed via YANG-based management protocols, such as
NETCONF [RFC6241] and RESTCONF [RFC8040]. These protocols have to
use a secure transport layer (e.g., SSH [RFC4252], TLS [RFC8446], and
QUIC [RFC9000]) and have to use mutual authentication.
The Network Configuration Access Control Model (NACM) [RFC8341]
provides the means to restrict access for particular NETCONF or
RESTCONF users to a preconfigured subset of all available NETCONF or
RESTCONF protocol operations and content.
The YANG module only defines a identity that uses the
"ds:conventional" identity as its base. The module by itself does
not expose any data nodes that are writable, date nodes that contain
read-only state, or RPCs. As such, there are no additional security
issues related to the YANG module that need to be considered.
11. References
11.1. Normative References
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[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>.
[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>.
[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>.
[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>.
[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>.
11.2. Informative References
[I-D.ietf-netmod-immutable-flag]
Ma, Q., Wu, Q., Lengyel, B., and H. Li, "YANG Metadata
Annotation for Immutable Flag", Work in Progress,
Internet-Draft, draft-ietf-netmod-immutable-flag-02, 27
September 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-netmod-immutable-flag-02>.
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[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-17, 27 September 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
rfc8407bis-17>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC4252] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
January 2006, <https://www.rfc-editor.org/info/rfc4252>.
[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>.
[RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
RFC 7952, DOI 10.17487/RFC7952, August 2016,
<https://www.rfc-editor.org/info/rfc7952>.
[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>.
[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>.
[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>.
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[RFC8808] Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for
Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808,
August 2020, <https://www.rfc-editor.org/info/rfc8808>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
Appendix A. Example of Dynamic Behaviors
This section presents some sample data models and corresponding
contents of various datastores with different dynamic behaviors
described in Section 6. The XML snippets are used only for
illustration purposes.
A.1. Referencing System-defined Nodes
In this subsection, the following fictional module is used:
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module example-application {
yang-version 1.1;
namespace "urn:example:application";
prefix "ex-app";
import ietf-inet-types {
prefix "inet";
}
container applications {
list application {
key "name";
leaf name {
type string;
}
leaf app-id {
type string;
}
leaf protocol {
type enumeration {
enum tcp;
enum udp;
}
mandatory true;
}
leaf destination-port {
default "0";
type inet:port-number;
}
leaf description {
type string;
}
container security-protection {
presence "Indicates that security protection is enabled.";
leaf risk-level {
type enumeration {
enum high;
enum low;
}
}
//additional leafs for security-specific configuration...
}
}
}
}
A fictional ACL YANG module is used as follows, which defines a
leafref for the leaf-list "application" data node to refer to an
existing application name.
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module example-acl {
yang-version 1.1;
namespace "urn:example:acl";
prefix "ex-acl";
import example-application {
prefix "ex-app";
}
import ietf-inet-types {
prefix "inet";
}
container acl {
list acl-rule {
key "name";
leaf name {
type string;
}
container matches {
choice l3 {
container ipv4 {
leaf src-address {
type inet:ipv4-prefix;
}
leaf dst-address {
type inet:ipv4-prefix;
}
}
}
choice applications {
leaf-list application {
type leafref {
path "/ex-app:applications/ex-app:application"
+ "/ex-app:name";
}
}
}
}
leaf packet-action {
type enumeration {
enum forward;
enum drop;
enum redirect;
}
}
}
}
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}
The server may predefine some applications as a convenience for
clients, these applications are immediately-present system
configuration. When the device is powered on, the system-
instantiated application entries may be present in <system> as
follows:
<applications xmlns="urn:example:application">
<application>
<name>ftp</name>
<app-id>001</app-id>
<protocol>tcp</protocol>
<destination-port>21</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
<application>
<name>tftp</name>
<app-id>002</app-id>
<protocol>udp</protocol>
<destination-port>69</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
<application>
<name>smtp</name>
<app-id>003</app-id>
<protocol>tcp</protocol>
<destination-port>25</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
</applications>
The client may also define its customized applications. Suppose the
configuration of applications is present in <running> as follows:
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<applications xmlns="urn:example:application">
<application>
<name>my-smtp</name>
<app-id>101</app-id>
<protocol>tcp</protocol>
<destination-port>2345</destination-port>
<description>customized smtp application</description>
<security-protection>
<risk-level>high</risk-level>
</security-protection>
</application>
<application>
<name>my-foo</name>
<app-id>102</app-id>
<protocol>udp</protocol>
<destination-port>69</destination-port>
<description>customized application</description>
</application>
</applications>
If a client configures an ACL rule referencing some system-provided
or customized applications, the configuration of ACL rule may be
shown as follows:
<acl xmlns="urn:example:acl">
<acl-rule>
<name>allow-access-to-ftp-tftp</name>
<matches>
<ipv4>
<src-address>198.51.100.0/24</src-address>
<dst-address>192.0.2.0/24</dst-address>
</ipv4>
<application>ftp</application>
<application>tftp</application>
<application>my-smtp</application>
</matches>
<packet-action>forward</packet-action>
</acl-rule>
</acl>
As different entries of application configuration in <system> and
<running> is merged to create <intended>, <operational> might contain
the configuration of applications as follows:
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<applications xmlns="urn:example:application"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<application>
<name>my-smtp</name>
<app-id>101</app-id>
<protocol>tcp</protocol>
<destination-port>2345</destination-port>
<description>customized smtp application</description>
<security-protection>
<risk-level>high</risk-level>
</security-protection>
</application>
<application>
<name>my-foo</name>
<app-id>102</app-id>
<protocol>udp</protocol>
<destination-port>69</destination-port>
<description>customized application</description>
</application>
<application or:origin="or:system">
<name>ftp</name>
<app-id>001</app-id>
<protocol>tcp</protocol>
<destination-port>21</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
<application or:origin="or:system">
<name>tftp</name>
<app-id>002</app-id>
<protocol>udp</protocol>
<destination-port>69</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
<application or:origin="or:system">
<name>smtp</name>
<app-id>003</app-id>
<protocol>tcp</protocol>
<destination-port>25</destination-port>
<security-protection>
<risk-level>low</risk-level>
</security-protection>
</application>
</applications>
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A.2. Modifying a System-instantiated Leaf's Value
This subsection uses the following fictional interface YANG module:
module example-interface {
yang-version 1.1;
namespace "urn:example:interface";
prefix "ex-if";
import ietf-inet-types {
prefix "inet";
}
container interfaces {
list interface {
key name;
leaf name {
type string;
}
leaf description {
type string;
}
leaf mtu {
type uint32;
}
leaf-list ip-address {
type inet:ip-address;
}
}
}
}
Suppose the system provides an immediately-present loopback interface
(named "lo0") with a MTU value "65536", a default IPv4 address of
"127.0.0.1", and a default IPv6 address of "::1". The configuration
of "lo0" interface is present in <system> as follows:
<interfaces xmlns="urn:example:interface">
<interface>
<name>lo0</name>
<mtu>65536</mtu>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
</interface>
</interfaces>
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A client modifies the value of MTU to 9216 and adds the following
configuration into <running> using a "merge" operation:
<interfaces xmlns="urn:example:interface">
<interface>
<name>lo0</name>
<mtu>9216</mtu>
</interface>
</interfaces>
Then the configuration of interfaces is present in <operational> as
follows:
<interfaces xmlns="urn:example:interface"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface>
<name>lo0</name>
<mtu>9216</mtu>
<ip-address or:origin="or:system">127.0.0.1</ip-address>
<ip-address or:origin="or:system">::1</ip-address>
</interface>
</interfaces>
A.3. Configuring Descendant Nodes of a System-defined Node
In the above example, imagine the client further configures the
description node of a "lo0" interface in <running> using a "merge"
operation as follows:
<interfaces xmlns="urn:example:interface">
<interface>
<name>lo0</name>
<description>loopback</description>
</interface>
</interfaces>
The configuration of interface "lo0" is present in <operational> as
follows:
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<interfaces xmlns="urn:example:interface"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface>
<name>lo0</name>
<description>loopback</description>
<mtu>9216</mtu>
<ip-address or:origin="or:system">127.0.0.1</ip-address>
<ip-address or:origin="or:system">::1</ip-address>
</interface>
</interfaces>
Appendix B. Key Use Cases
This section provides three use cases related to how <system>
interacts with other datastores (e.g., <candidate>, <running>,
<intended>, and <operational>). The following fictional interface
data model is used:
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module example-interface-management {
yang-version 1.1;
namespace "urn:example:interfacemgmt";
prefix "ex-ifm";
import ietf-inet-types {
prefix "inet";
}
container interfaces {
list interface {
key "name";
leaf name {
type string;
}
leaf type {
type enumeration {
enum ethernet;
enum atm;
enum loopback;
}
}
leaf enabled {
type boolean;
default "true";
}
leaf-list ip-address {
type inet:ip-address;
}
leaf speed {
when "../type = 'ethernet'";
type enumeration {
enum 10Mb;
enum 100Mb;
}
}
leaf description {
type string;
}
}
}
}
For each use case, corresponding sample configuration in <running>,
<system>, <intended> and <operational> are shown. The XML snippets
are used only for illustration purposes.
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B.1. Device Powers On
When the device is powered on, suppose the system provides an
immediately-present loopback interface (named "lo0") which is not
explicitly configured in <running>. Thus, no configuration for
interfaces appears in <running>;
And the contents of <system> are:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces>
In this case, the configuration of loopback interface is only present
in <system>, the configuration of interface in <intended> would be
identical to the one in <system> shown above.
And <operational> will show the system-provided loopback interface,
note that <operational> also includes the default value specified in
the YANG module:
<interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:system">
<interface>
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces>
B.2. Client Commits Configuration
If a client creates an interface "et-0/0/0" but the interface does
not physically exist at this point, what is in <running> appears as
follows:
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<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
And the contents of <system> keep unchanged since the interface is
not physically present:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces>
The contents of <intended> represent the merged data of <system> and
<running>:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
Since the interface named "et-0/0/0" does not exist, the associated
configuration is not present in <operational>, which appears as
follows:
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<interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
</interfaces>
B.3. Operator Installs Card into a Chassis
When the interface is installed by the operator, the system will
detect it and generate the associated conditionally-present interface
configuration in <system>. The contents of <running> keep unchanged:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
And <system> might appear as follows:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<description>system-defined interface</description>
</interface>
</interfaces>
Then <intended> contains the merged configuration of <system> and
<running>:
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<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
And the contents of <operational> appear as follows:
<interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">
<name>lo0</name>
<type>loopback</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type or:origin="or:system">ethernet</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>192.168.10.10</ip-address>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
B.4. Client further Commits Configuration
If the client further sets the speed of interface "et-0/0/0" in
<running> using a "merge" operation:
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<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>et-0/0/0</name>
<speed>10Mb</speed>
</interface>
</interfaces>
The contents of <system> keep unchanged:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<description>system-defined interface</description>
</interface>
</interfaces>
And the contents of <intended> which represents a merged results of
<running> and <system> are as follows:
<interfaces xmlns="urn:example:interfacemgmt">
<interface>
<name>lo0</name>
<type>loopback</type>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type>ethernet</type>
<ip-address>192.168.10.10</ip-address>
<speed>10Mb</speed>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
And <operational> would appear as follows:
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<interfaces xmlns="urn:example:interfacemgmt"
xmlns:or="urn:ietf:params:xml:ns:yang:ietf-origin"
or:origin="or:intended">
<interface or:origin="or:system">
<name>lo0</name>
<type>loopback</type>
<enabled>true</enabled>
<ip-address>127.0.0.1</ip-address>
<ip-address>::1</ip-address>
<description>system-defined interface</description>
</interface>
<interface>
<name>et-0/0/0</name>
<type or:origin="or:system">ethernet</type>
<enabled or:origin="or:default">true</enabled>
<ip-address>192.168.10.10</ip-address>
<speed>10Mb</speed>
<description>pre-provisioned interface</description>
</interface>
</interfaces>
Acknowledgements
The authors would like to thank for following for discussions and
providing input to this document: Balazs Lengyel, Robert Wilton,
Juergen Schoenwaelder, Andy Bierman, Martin Bjorklund, Mohamed
Boucadair, Michal Vaško, Alexander Clemm, and Timothy Carey.
Contributors
Kent Watsen
Watsen Networks
Email: kent+ietf@watsen.net
Jan Lindblad
Cisco Systems
Email: jlindbla@cisco.com
Jason Sterne
Nokia
Email: jason.sterne@nokia.com
Chongfeng Xie
China Telecom
Beijing
China
Email: xiechf@chinatelecom.cn
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Authors' Addresses
Qiufang Ma (editor)
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: maqiufang1@huawei.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: bill.wu@huawei.com
Chong Feng
Email: fengchongllly@gmail.com
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