]> System-Defined Configuration Huawei
101 Software Avenue, Yuhua District Nanjing Jiangsu 210012 China maqiufang1@huawei.com
Huawei
101 Software Avenue, Yuhua District Nanjing Jiangsu 210012 China bill.wu@huawei.com
fengchongllly@gmail.com
OPS netmod system config 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 a 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.
Introduction The Network Management Datastore Architecture (NMDA) defines system configuration as the configuration that is supplied by the device itself and appears in <operational> when it is in use (see Figure 2 in ). However, there is a desire from operators to enable a server to better expose the system configuration, regardless of whether it is in use. For example, some implementations define the system configuration that must be referenced to be active. Network Configuration Protocol (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, whose existence in the system configuration is tied to the presence of particular hardware, 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 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 ().
Terminology This document assumes that the reader is familiar with the contents of , , , and and uses terminologies from those documents. The terms "device" and "server" are used interchangeably in this document. The following terms are defined in this document:
system configuration:
defines it as "Configuration that is supplied by the device itself". The definition herein refines that definition to represent configuration present in the system configuration datastore (regardless of whether it is applied or referenced). It may also be referred to as "system-defined configuration" or "system-provided configuration" throughout this document. The system configuration discussed in this document cannot be deletable; configuration provided by the server that is deletable is outside the scope of this document.
system configuration datastore:
This is 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 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. Note that while protocol operations allow copying data between conventional datastores, the read-only nature of datastores such as <system> and <intended> restricts clients from copying data into them.
system node:
This is 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 the following:
  • 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.
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 when, and only when, they appear in all capitals, as shown here.
Updates to RFC 8342 This document updates to define a configuration datastore called "system" that holds system configuration (). It also redefines the term "conventional configuration datastore" from to include "system" in the list. To ensure the validity of <intended> when clients interact with system configuration (e.g., configuration provided by clients references system configuration) and allow the existence of system-defined templates and inactive system configuration, configuration in <running> is merged with <system> to create the contents of <intended> after the configuration transformations (e.g., template expansion or removal of inactive configuration defined in ) have been performed, as described in . Specifications in related to the processing of system configuration are updated by the mechanism defined in this document. Additionally, this document also updates the definition of the "intended" origin metadata annotation identity defined in . The "intended" identity of the origin value defined in represents the origin of configuration provided by <intended>. This document updates that definition as the origin source of configuration explicitly provided by clients 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. As per , all configuration with the origin value being reported as "intended" MUST originate from <running>, which includes any configuration in <system> that has been copied into <running>. Configuration that is in <system> and not also present in <running> MUST be reported as origin "system" in <operational>.
Kinds of System Configuration This document defines two types of system configuration: configuration that is always present and configuration that is conditionally present. These types of system configuration are described in Sections and , respectively.
Always Present The always-present system configuration is generated in <system> when the device is powered on, irrespective of whether physical resources are present or whether a special functionality is enabled. An example of an always-present system configuration is an always-existing loopback interface.
Conditionally Present The conditionally present system configuration 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 the associated configuration; when the physical resource is not present (an interface card is removed), the system configuration will automatically be removed from <system>. Another example is when a special functionality (e.g., a license or feature) is enabled, specific configuration may be created by the system.
The System Configuration Datastore (<system>) Following guidelines for defining datastores in , 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 node, 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 management operations via NETCONF and RESTCONF protocols.
Origin:
This document does not define any new origin identity. The "system" identity of origin metadata annotation is used to indicate the origin of a data item provided in <system>.
Protocols:
YANG-driven management protocols, such as NETCONF and RESTCONF.
Defining YANG module:
"ietf-system-datastore" ().
The system configuration datastore does not persist across reboots.
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 . 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 or removal of inactive configuration defined in ) before it can be applied, configuration transformations MUST be performed independently on each datastore 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 is updated with the below conceptual model of datastores that incorporates the system configuration datastore. For completeness, this model also includes <factory-default> introduced in .
Architectural Model of Datastores | +-----| (ct, ro) |-----+ | +-----------------+ | //"factory-reset" RPC| | | v | v +-------------+ | +-----------+ | | | | | | (ct, rw) |<---+ | +---->| (ct, rw) | +-------------+ | | | +-----------+ | | v | | +-----------+ | +-----------+ | | | +------->| |<--------+ | (ct, ro) | | (ct, rw) | +-----------+ +-----------+ | | | | | | // configuration transformations, +--------------+---------------+ // e.g., removal of nodes marked | // as "inactive", expansion of | // templates v +------------+ | | // 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 +---------------+ | | <-- system state | (ct + cf, ro) | +---------------+ ct = config true; cf = config false rw = read-write; ro = read-only boxes denote named datastores]]>
Configuration in <system> cannot be deleted by clients (e.g., a list entry can never be removed from <system> through protocol operations), even though a node defined in <system> may be overridden in <running>. If the system initializes a value for a particular leaf that is overridden by the client with a different value in <running> (), and if the node in <running> is removed at a later time, the system-initialized value defined in <system> appears in <intended> and may come into use eventually if applied successfully. Configuration may disappear from <system> due to, e.g., resources no longer available. In such cases, configuration for missing resources can still remain in <running> and <intended>, but it will not be applied and appear in <operational>. This is further clarified in .
Static Characteristics
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 ).
No Changes to <operational> This work does not change the definition of <operational> nor does it impact the contents of <operational>, as specified in . It clarifies origin reporting, i.e., the origin of nodes sourced from <system> is reported as "system" unless explicitly configured or overridden in <running>. <system> enables system-defined 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.
Dynamic Behaviors
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 ). The updates of system configuration may be obtained through YANG notifications (e.g., on-change notification). If system configuration changes (e.g., during a software upgrade), <running> SHOULD remain a valid configuration data tree. Any mechanisms to achieve this are outside the scope of this document.
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. provides an example of a client referencing system-defined nodes.
Overriding System Configuration Although <system> is read-only, in some cases, a server may allow some parts of system configuration (e.g., a leaf's value) to be overridden (note the distinction between <system> and system configuration). Overriding of system configuration is achieved by the client writing configuration data in <running>, which 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 overridden (some implementations may have immutable system configuration that is identified by the server using an immutable metadata annotation; see for details), regardless of whether a system-instantiated value changes subsequently. provides an example of a client overriding a system-instantiated leaf's value.
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). provides an example of a client configuring descendant nodes of a system-defined node.
The "ietf-system-datastore" Module
Data Model Overview This YANG module defines a new YANG identity named "system", which uses the "ds:conventional" identity defined in 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: The diagram above uses syntax that is similar to but not defined in .
YANG Module WG List: Author: Qiufang Ma Author: Qin Wu Author: Chong Feng "; description "This module defines a new YANG identity that uses the ds:conventional identity defined in RFC 8342. Copyright (c) 2026 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC 10016 (https://www.rfc-editor.org/info/rfc10016); see the RFC itself for full legal notices."; revision 2026-09-16 { description "Initial version."; reference "RFC 10016: System-Defined Configuration"; } identity system { base ds:conventional; description "This read-only datastore contains the configuration provided by the system itself."; } }]]>
Example Usage The following example shows how the configuration in <system> could be retrieved in a NETCONF <get-data> RPC operation. The example uses the "example-application" fictional data model defined in and the Extensible Markup Language (XML) encoding. sysds:system ]]> When using the RESTCONF protocol, the system configuration datastore can be accessed via the resource: {+restconf}/ds/ietf-system-datastore:system. The following example uses an HTTP GET method to request "applications" configuration:
IANA Considerations
The IETF XML Registry IANA has registered the following XML namespace URI in the "ns" registry within the "IETF XML Registry" group :
URI:
urn:ietf:params:xml:ns:yang:ietf-system-datastore
Registrant Contact:
The IESG
XML:
N/A; the requested URIs are XML namespaces.
The YANG Module Names Registry IANA has registered the following YANG module in the "YANG Module Names" registry within the "YANG Parameters" registry group. .
Name:
ietf-system-datastore
Maintained by IANA?
N
Namespace:
urn:ietf:params:xml:ns:yang:ietf-system-datastore
Prefix:
sysds
Reference:
RFC 10016
Operational Considerations System configuration exists regardless of whether the server implements <system> or not. The introduction of <system> provides a standardized way to expose system configuration within NMDA. NMDA clients that are not aware of <system> will continue to operate correctly. They will interact only with datastores such as <running>, <candidate>, <intended>, and <operational> as before. The presence of <system> does not change the fundamental behavior for such legacy clients. Operators should be aware that to fully leverage the capabilities defined in this document, client applications need to be updated to recognize and interact with <system>.
Security Considerations
Considerations for the "ietf-system-datastore" YANG Module This section is modeled after the template described in . The "ietf-system-datastore" YANG module defines a data model that is designed to be accessed via YANG-based management protocols, such as the Network Configuration Protocol (NETCONF) and RESTCONF . These YANG-based management protocols (1) have to use a secure transport layer and (2) have to use mutual authentication (e.g., Secure Shell (SSH) , TLS , and QUIC ). The Network Configuration Access Control Model (NACM) 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 an identity that uses the "ds:conventional" identity as its base. The module by itself does not expose any sensitive data nodes that are writable or that contain read-only state, and there are no particularly sensitive RPC or action operations. As such, there are no additional security issues related to the YANG module that need to be considered.
Considerations for System Configuration The system datastore, while read-only to clients, may contain sensitive information such as hardware identifiers, security policies, and critical system resources. Read access to sensitive system nodes and subtrees within the datastore MUST be controlled to prevent unauthorized disclosure. Implementations are strongly advised to log all access attempts to sensitive system configuration for audit purposes. Furthermore, while <system> cannot be modified directly, system configuration may be overridden as a merging result (). An attacker may configure a leaf that shadows a sensitive node in <system>. Misconfiguration in <running> could lead to unintended system behavior, including security policy bypass and availability risks. Unauthorized modification to sensitive contents MUST be prevented to avoid those negative effects on the network.
References Normative References Informative References YANG Metadata Annotation for Immutable Flag Huawei Huawei Ericsson HPE Extensible Markup Language (XML) 1.0 (Fifth Edition) W3C Recommendation Latest version available at .
Example of Dynamic Behaviors (Informative) This section presents some sample data models and corresponding contents of various datastores with different dynamic behaviors described in . The XML snippets are used only for illustration purposes. Note that this section does not show the contents of <intended> as they are related to the configuration in <operational>, assuming the intended configuration is applied successfully. Also note that if the "origin" metadata annotation for configuration is unspecified in snippets, it is inherited from its parent node.
Referencing System-Defined Nodes In this subsection, the following fictional module is used: A fictional Access Control List (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. 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: ftp 001 tcp 21 low tftp 002 udp 69 low smtp 003 tcp 25 low ]]> The client may also define customized applications. Those applications may be present in <running> as follows: my-smtp 101 tcp 2345 customized smtp application high my-foo 102 udp 1024 customized application ]]> If a client configures an ACL rule referencing some system-provided or customized applications, the configuration of the ACL rule may be shown as follows: allow-access-to-ftp-tftp 198.51.100.0/24 192.0.2.0/24 ftp tftp my-smtp forward ]]> As different entries of application configuration in <system> and <running> are merged to create <intended>, and there are no merging conflicts in the contents between <system> and <running>, <operational> might contain the configuration of applications with the values of origin reflecting the source of entries as follows: my-smtp 101 tcp 2345 customized smtp application high my-foo 102 udp 1024 customized application ftp 001 tcp 21 low tftp 002 udp 69 low smtp 003 tcp 25 low ]]>
Modifying a System-Instantiated Leaf's Value This subsection uses the following fictional interface YANG module: Suppose the system provides an always-present loopback interface (named "lo0") with an MTU value "65536", a default IPv4 address of "127.0.0.1", and a default IPv6 address of "::1". The configuration of the "lo0" interface may be present in <system> as follows: lo0 65536 127.0.0.1 ::1 ]]> A client modifies the value of MTU to 9216 by adding the following configuration into <running>: lo0 9216 ]]> Since the MTU value provided by the client takes precedence over the system-provided value, and the "origin" value of configuration provided by the client is set to "intended", the configuration of interfaces that is present in <operational> may be as follows: lo0 9216 127.0.0.1 ::1 ]]>
Configuring Descendant Nodes of a System-Defined Node Based on the example in , imagine the client further adds the description node of a "lo0" interface in <running> as follows: lo0 loopback ]]> The configuration of interface "lo0" is present in <operational> as follows: lo0 loopback 9216 127.0.0.1 ::1 ]]>
Key Use Cases (Informative) This section updates the "Interface Example" supplied in . This section provides several 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: For each use case, corresponding sample configuration in <running>, <system>, <intended>, and <operational> is shown. The XML snippets are used only for illustration purposes.
Device Powers On When the device is powered on, assume the system provides an always-present loopback interface named "lo0" that is not explicitly configured in <running>. As a result, no interface configuration appears in <running>, and the content of <system> is as follows: lo0 loopback 127.0.0.1 ::1 system-defined interface ]]> In this case, the configuration of loopback interface is only present in <system>, and the configuration of interface in <intended> would be identical to the one in <system> shown above. In addition, <operational> will show the system-provided loopback interface. Note that <operational> also includes the default value specified in the YANG module: lo0 loopback true 127.0.0.1 ::1 system-defined interface ]]>
Client Commits Configuration If a client creates an interface "et-0/0/0" but the interface does not physically exist at this point, the content of <running> appears as follows: et-0/0/0 192.168.10.10 pre-provisioned interface ]]> And the content of <system> remains unchanged, only containing the "lo0" loopback interface since the interface "et-0/0/0" is not physically present: lo0 loopback 127.0.0.1 ::1 system-defined interface ]]> The content of <intended> represents the merged data of <system> and <running>: lo0 loopback 127.0.0.1 ::1 system-defined interface et-0/0/0 192.168.10.10 pre-provisioned interface ]]> Since the interface named "et-0/0/0" does not exist, the associated configuration is not present in <operational>, which appears as follows: lo0 loopback true 127.0.0.1 ::1 system-defined interface ]]>
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 content of <running> remains unchanged: et-0/0/0 192.168.10.10 pre-provisioned interface ]]> And <system> might appear as follows: lo0 loopback 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet system-defined interface ]]> Then, <intended> contains the merged configuration of <system> and <running>: lo0 loopback 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet 192.168.10.10 pre-provisioned interface ]]> And the content of <operational> appears as follows: lo0 loopback true 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet true 192.168.10.10 pre-provisioned interface ]]>
Client Further Commits Configuration If the client further sets the speed of interface "et-0/0/0" in <running>: et-0/0/0 10Mb ]]> The content of <system> remains unchanged: lo0 loopback 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet system-defined interface ]]> And the content of <intended>, which represents the merged result of <running> and <system>, is as follows: lo0 loopback 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet 192.168.10.10 10Mb pre-provisioned interface ]]> And <operational> would appear as follows: lo0 loopback true 127.0.0.1 ::1 system-defined interface et-0/0/0 ethernet true 192.168.10.10 10Mb pre-provisioned interface ]]>
Acknowledgements The authors would like to thank the following for discussions and providing input to this document: , , , , , , , , and .
Contributors Watsen Networks
kent+ietf@watsen.net
 Cisco Systems
jlindbla@cisco.com
 Nokia
jason.sterne@nokia.com
 China Telecom
Beijing China xiechf@chinatelecom.cn