NETMOD Q. Ma, Ed. Internet-Draft Q. Wu Updates: 8342, 6241, 8526, 8040 (if approved) C. Feng Intended status: Standards Track Huawei Expires: 5 January 2024 4 July 2023 System-defined Configuration draft-ietf-netmod-system-config-02 Abstract This document describes how a management client and server handle YANG-modeled configuration data that is defined by the server itself. The system-defined configuration can be referenced (e.g. leafref) by configuration explicitly created by a client. The Network Management Datastore Architecture (NMDA) defined in RFC 8342 is updated with a read-only conventional configuration datastore called "system" to hold system-defined configuration. As an alternative to clients explicitly copying referenced system-defined configuration into the target configuration datastore (e.g., ) so that the datastore is valid, a "resolve-system" parameter is defined to allow the server acting as a "system client" to copy referenced system-defined nodes automatically. This solution enables clients manipulating the target configuration datastore (e.g., ) to overlay (e.g., copy system configuration using the same key value as in ) and reference nodes defined in , override values of configurations defined in , and configure descendant nodes of system-defined nodes. This document updates RFC 8342, RFC 6241, RFC 8526 and RFC 8040. 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." Ma, et al. Expires 5 January 2024 [Page 1] Internet-Draft System-defined Configuration July 2023 This Internet-Draft will expire on 5 January 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.3. Updates to RFC 8342 . . . . . . . . . . . . . . . . . . . 5 1.4. Updates to RFC 6241 and RFC 8526 . . . . . . . . . . . . 6 1.5. Updates to RFC 8040 . . . . . . . . . . . . . . . . . . . 6 1.5.1. Query Parameter . . . . . . . . . . . . . . . . . . . 6 1.5.2. Query Parameter URI . . . . . . . . . . . . . . . . . 7 2. Kinds of System Configuration . . . . . . . . . . . . . . . . 7 2.1. Immediately-Active . . . . . . . . . . . . . . . . . . . 7 2.2. Conditionally-Active . . . . . . . . . . . . . . . . . . 8 2.3. Inactive-Until-Referenced . . . . . . . . . . . . . . . . 8 3. The System Configuration Datastore () . . . . . . . . 8 4. Static Characteristics of . . . . . . . . . . . . . 9 4.1. Read-only to Clients . . . . . . . . . . . . . . . . . . 9 4.2. May Change via Software Upgrades . . . . . . . . . . . . 9 4.3. No Impact to . . . . . . . . . . . . . . . 10 5. Dynamic Behavior . . . . . . . . . . . . . . . . . . . . . . 10 5.1. Conceptual Model of Datastores . . . . . . . . . . . . . 10 5.2. Explicit Declaration of System Configuration . . . . . . 12 5.3. Servers Auto-configuring Referenced System Configuration ("resolve-system" parameter) . . . . . . . . . . . . . . 13 5.4. Modifying (Overriding) System Configuration . . . . . . . 14 5.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . 15 5.5.1. Server Configuring of Automatically . . . . 15 5.5.2. Declaring a System-defined Node in Explicitly . . . . . . . . . . . . . . . . . . . . . 21 5.5.3. Modifying a System-instantiated Leaf's Value . . . . 24 5.5.4. Configuring Descendant Nodes of a System-defined Node . . . . . . . . . . . . . . . . . . . . . . . . 26 Ma, et al. Expires 5 January 2024 [Page 2] Internet-Draft System-defined Configuration July 2023 6. The "ietf-system-datastore" Module . . . . . . . . . . . . . 27 6.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 28 6.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 28 6.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 29 7. The "ietf-netconf-resolve-system" Module . . . . . . . . . . 30 7.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 31 7.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 32 7.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 35 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 8.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . . 37 8.2. The "YANG Module Names" Registry . . . . . . . . . . . . 38 8.3. RESTCONF Capability URN Registry . . . . . . . . . . . . 38 9. Security Considerations . . . . . . . . . . . . . . . . . . . 38 9.1. Regarding the "ietf-system-datastore" YANG Module . . . . 38 9.2. Regarding the "ietf-netconf-resolve-system" YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 39 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 39 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 40 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Normative References . . . . . . . . . . . . . . . . . . . . . 40 Informative References . . . . . . . . . . . . . . . . . . . . 41 Appendix A. Key Use Cases . . . . . . . . . . . . . . . . . . . 42 A.1. Device Powers On . . . . . . . . . . . . . . . . . . . . 42 A.2. Client Commits Configuration . . . . . . . . . . . . . . 43 A.3. Operator Installs Card into a Chassis . . . . . . . . . . 44 Appendix B. Changes between Revisions . . . . . . . . . . . . . 45 Appendix C. Open Issues tracking . . . . . . . . . . . . . . . . 46 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46 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 when it is in use (Figure 2 in [RFC8342]). However, there is a desire to enable a server to better structure and expose the system configuration. NETCONF/RESTCONF clients can benefit from a standard mechanism to retrieve what system configuration is available on a server. Some servers allow the NETCONF/RESTCONF client to reference a system- defined node which isn't present in the target datastore (e.g., ). The absence of the system configuration in the datastore can render the datastore invalid from the perspective of a client or offline tools (e.g., missing leafref targets). This document describes several approaches to bring the datastore to a valid state and ensuing that all referential integrity constraints are satisfied. Ma, et al. Expires 5 January 2024 [Page 3] Internet-Draft System-defined Configuration July 2023 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., "name" and "type" set by the system). This document updates the Network Management Datastore Architecture (NMDA) defined in RFC 8342 with a read-only conventional configuration datastore called "system" to hold system-defined configuration. As an alternative to clients explicitly copying referenced system-defined configuration into the target configuration datastore (e.g., ) so that the datastore is valid, a "resolve-system" parameter has been defined to allow the server acting as a "system client" to copy referenced system-defined nodes automatically. This solution enables clients manipulating the target configuration datastore (e.g., ) to overlay (e.g., copy system configuration using the same key value as in ) and reference nodes defined in , override values of configurations defined in , and configure descendant nodes of system-defined nodes. If a system-defined node is referenced, it refers to one of the following cases throughout this document: * It is present in a leafref "path" statement and referred as the leafref value * It is used as an "instance-identifier" type value * It is present in an Xpath expression of "when" or "must" constraints * It is defined to satisfy the "mandatory" constraints * It is defined to exactly satisfy the "min-element" constraints Conformance to this document requires the NMDA servers to implement the "ietf-system-datastore" YANG module (Section 6). 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: Ma, et al. Expires 5 January 2024 [Page 4] Internet-Draft System-defined Configuration July 2023 System configuration: Configuration that is provided by the system itself. System configuration is present in the system configuration datastore (regardless of being applied by the device or referenced by other configuration nodes), and appears in the intended configuration datastore. System configuration that is considered active (according to the NMDA defined in RFC 8342) appears in with origin="system". It is a different and separate concept from factory default configuration defined in RFC 8808 (which represents a preset initial configuration that is used to initialize the configuration of a server). System configuration datastore: A configuration datastore holding configuration provided by the system itself. This datastore is referred to as "". 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: , , , , and . 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. 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, it also redefines the term "conventional configuration datastore" from RFC 8342 to add "system" to the list of conventional configuration datastores. The contents of are read-only to clients but may change dynamically. aware client may retrieve all three types of system configuration defined in Section 2, reference nodes defined in , override values of configurations defined in , and configure descendant nodes of system-defined nodes. Ma, et al. Expires 5 January 2024 [Page 5] Internet-Draft System-defined Configuration July 2023 The server will merge and to create . As always, system configuration will appear in with origin="system" when it is in use. The system datastore makes system configuration visible to clients in order for being referenced or configurable prior to present in . 1.4. Updates to RFC 6241 and RFC 8526 This document augments and RPC operations defined in [RFC6241] and [RFC8526] respectively, with a new additional input parameter "resolve-system". The RPC operation defined in [RFC6241] is also augmented to support "resolve- system" parameter. The "resolve-system" parameter is optional and has no value. When it is provided and the server detects that there is a reference to a system-defined node during the validation, the server will automatically copy the referenced system configuration into the validated datastore to make the configuration valid without the client doing so explicitly. Legacy clients interacting with servers that support this parameter don't see any changes in / and behaviors. The server's copy referenced nodes from to the target datastore MUST be enforced at the end of the / or operations, regardless of which target datastore it is. 1.5. Updates to RFC 8040 This document extends Sections 4.8 and 9.1.1 of [RFC8040] to add a new query parameter "resolve-system" and corresponding query parameter capability URI. 1.5.1. Query Parameter The "resolve-system" parameter controls whether to allow a server copy any referenced system-defined configuration automatically without the client doing so explicitly. This parameter is only allowed with no values carried. If this parameter has any unexpected value, then a "400 Bad Request" status-line is returned. Ma, et al. Expires 5 January 2024 [Page 6] Internet-Draft System-defined Configuration July 2023 +----------------+---------+-----------------------------------------+ | Name | Methods | Description | +----------------+---------+-----------------------------------------+ |resolve-system | POST, | resolve any references not resolved by | | | PUT | the client and copy referenced | | | PATCH | system configuration into | | | | automatically. This parameter can be | | | | given in any order. | +----------------+---------+-----------------------------------------+ Figure 1: RESTCONF "resolve-system" Query Parameter 1.5.2. Query Parameter URI To enable a RESTCONF client to discover if the "resolve-system" query parameter is supported by the server, the following capability URI is defined, which is advertised by the server if supported, using the "ietf-restconf-monitoring" module defined in RFC 8040: urn:ietf:params:restconf:capability:resolve-system:1.0 Comment: Should we define a similar capability identifier for NETCONF protocol? 2. Kinds of System Configuration There are three types of system configurations defined in this document: immediately-active system configuration, conditionally- active system configuration, and inactive-until-referenced system configuration. Active system configuration refers to configuration that is in use by a device. As per definition of the operational state datastore in [RFC8342], if system configuration is inactive, it should not appear in . However, system configuration is present in once it is generated, regardless of whether it is active or not. 2.1. Immediately-Active Immediately-active system configurations are those generated in and applied immediately when the device is powered on (e.g., a loopback interface), irrespective of physical resource present or not, a special functionality enabled or not. Ma, et al. Expires 5 January 2024 [Page 7] Internet-Draft System-defined Configuration July 2023 2.2. Conditionally-Active System configurations which are generated in and applied based on specific conditions being met in a system, e.g., if a physical resource is present (e.g., insert interface card), the system will automatically detect it and load pre-provisioned configuration; when the physical resource is not present(remove interface card), the system configuration will be automatically cleared. Another example is when a special functionality is enabled, e.g., when a QoS feature is enabled, related QoS policies are automatically created by the system. 2.3. Inactive-Until-Referenced There are some system configurations predefined (e.g., application ids, anti-x signatures, trust anchor certs, etc.) as a convenience for the clients, which must be referenced to be active. The clients can also define their own configurations for their unique requirements. Inactive-until-referenced system configurations are generated in immediately when the device is powered on, but they are not active until being referenced. 3. The System Configuration Datastore () NMDA servers compliant with this document MUST implement a system configuration datastore, and they SHOULD also implement . 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. * 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 content of the datastore is set by the server in an implementation dependent manner. The content can not be changed by management operations via protocols such as NETCONF, RESTCONF, but may change itself by upgrades and/or when resource- conditions are met. The datastore can be read using the standard network management protocols such as NETCONF and RESCTCONF. Ma, et al. Expires 5 January 2024 [Page 8] Internet-Draft System-defined Configuration July 2023 * Origin: This document does not define any new origin identity when it interacts with and flows into . The "system" origin Metadata Annotation [RFC7952] is used to indicate the origin of a data item is system. * Protocols: YANG-driven management protocols, such as NETCONF and RESTCONF. * Defining YANG module: "ietf-system-datastore". The datastore's content is defined by the server and read-only to clients. Upon the content is created or changed, it will be merged into . Unlike [RFC8808], it MAY change dynamically, e.g., depending on factors like device upgrade or system-controlled resources change (e.g., HW available). The system configuration datastore doesn't persist across reboots; the contents of will be lost upon reboot and recreated by the system with the same or changed contents. RPC operation defined in [RFC8808] can reset it to its factory default configuration without including configuration generated due to the system update or client-enabled functionality. The system datastore is defined as a conventional configuration datastore and shares a common datastore schema with other conventional datastores. 4. Static Characteristics of 4.1. Read-only to Clients The system datastore is a read-only configuration datastore (i.e., edits towards directly MUST be denied), though the client may be allowed to override the value of a system-initialized data node (see Section 5.4). 4.2. May Change via Software Upgrades System configuration may change dynamically, e.g., depending on factors like device upgrade or if system-controlled resources (e.g., HW available) change. In some implementations, when a QoS feature is enabled, QoS-related policies are created by the system. If the system configuration gets changed, YANG notifications (e.g., "push-change-update" notification) [RFC6470][RFC8639][RFC8641] can be used to notify the client. Any update of the contents in will not cause the automatic update of , even if some of the system configuration has already been copied into explicitly or automatically before the update. Ma, et al. Expires 5 January 2024 [Page 9] Internet-Draft System-defined Configuration July 2023 4.3. No Impact to This work intends to have no impact to . System configuration appears in with "origin=system". This document enables a subset of those 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 . "Config false" nodes are out of scope, hence existing "config false" nodes are not impacted by this work. 5. Dynamic Behavior 5.1. Conceptual Model of Datastores This document introduces a datastore named "system" which is used to hold all three types of system configurations defined in Section 2. When the device is powered on, immediately-active system configuration will be generated in and active immediately, but inactive-until-referenced system configuration only becomes active if it is referenced by client-defined configuration. While conditionally-active system configuration will only be created and active if the condition on system resources is met when the device is powered on or running. All above three types of system configurations will appear in . Clients MAY reference nodes defined in , override values of configurations defined in , and configure descendant nodes of system-defined nodes, by copying or writing intended configurations into the target configuration datastore (e.g., ). The server will merge and to create , in which process, the data node appears in takes precedence over the same node in if the server allows the node to be modifiable; additional nodes to a list entry or new list/leaf-list entries appear in extends the list entry or the whole list/ leaf-list defined in if the server allows the list/leaf-list to be updated. In addition, the intended configuration datastore represents the configuration after all configuration transformation to are performed (e.g., system-defined template expansion, removal of inactive system configuration). If a server implements , MUST be merged into . As a result, Figure 2 in Section 5 of RFC 8342 is updated with the below conceptual model of datastores which incorporates the system configuration datastore. Ma, et al. Expires 5 January 2024 [Page 10] Internet-Draft System-defined Configuration July 2023 +-------------+ +-----------+ | | | | | (ct, rw) |<---+ +--->| (ct, rw) | +-------------+ | | +-----------+ | | | | +-----------+ | +-----------+ | | | +-------->| |<--------+ | (ct, ro) | | (ct, rw) | +-----+-----+ +----+------+ | | +--------+ +------+ // configuration transformations, | | // e.g., removal of nodes marked | | // as "inactive", expansion of | | // templates V 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 Figure 2: Architectural Model of Datastores Servers MUST enforce that configuration references in are resolved within and ensure that contains any referenced system configuration. Clients MUST either explicitly copy system-defined nodes into or use the "resolve-system" parameter. The server MUST enforce that the referenced system nodes configured into by the client is consistent with . Note that aware clients know how to discover what nodes exist in . How clients unaware of the system datastore can find appropriate configurations is beyond the scope of this document. Ma, et al. Expires 5 January 2024 [Page 11] Internet-Draft System-defined Configuration July 2023 No matter how the referenced system configurations are copied into , the nodes copied into would always be returned after a read of , regardless if the client is aware. Configuration defined in is merged into . It is also present in if it is in use by the device, even if a client may delete the configuration which is copied from into . For example, system initializes a value for a particular leaf which is overridden by the client with a different value in . The client may delete that node in , in which case system-initialized value defined in can be still in use and appear in . Applied system configuration regardless of explicitly or automatically being copied into , appears in with origin="system". Comment: this might need further discussion: should the origin="system" be required for system configuration copied/pasted into ? Any deletable system-provided configuration that is placed into by the system at boot up, without being part of the contents of a datastore, must be defined in [RFC8808], which is used to initialize when the device is first-time powered on or reset to its factory default condition. 5.2. Explicit Declaration of System Configuration It is possible for a client to explicitly declare system configuration nodes in the target datastore (e.g., ) with the same values as in , by configuring a node (list/leaf-list entry, leaf, etc.) in the target datastore (e.g., ) that matches the same node and value in . The explicit configuration of system-defined nodes in the target datastore (e.g., ) can be useful, for example, when the client doesn't want a "system client" to have a role or hasn't implemented the "resolve-system" parameter but need the datastore to be valid. The client can explicitly declare (i.e., configure in the datastore like ) the list entries (with at least the keys) for any system configuration list entries that are referenced elsewhere in . The client does not necessarily need to declare all the contents of the list entry (i.e. the descendant nodes) , only the parts that are required to make the datastore appear valid. Ma, et al. Expires 5 January 2024 [Page 12] Internet-Draft System-defined Configuration July 2023 5.3. Servers Auto-configuring Referenced System Configuration ("resolve-system" parameter) This document defines a new parameter "resolve-system" to the input for the , , and operations. Clients that are aware of the "resolve-system" parameter MAY use this parameter to avoid the requirement to provide a referentially complete configuration in . If the "resolve-system" is present, and the server supports this capability, the server MUST copy relevant referenced system-defined nodes into the target datastore (e.g., ) without the client doing the copy/paste explicitly, to resolve any references not resolved by the client. The server acting as a "system client" like any other remote clients copies the referenced system-defined nodes when triggered by the "resolve-system" parameter. The server may automatically configure the list entries (with at least the keys) in the target datastore (e.g., ) for any system configuration list entries that are referenced elsewhere by the clients. Similarly, not all the contents of the list entry (i.e., the descendant nodes) are necessarily copied by the server - only the parts that are required to make valid. There is no distinction between the configuration in the target datastore (e.g., ) which is automatically configured by the server and the one explicitly declared by the client, e.g., a read back of the datastore (i.e., , or operation) returns automatically configured nodes. Note that even an auto-configured node is allowed to be deleted from the target datastore by the client, the operation request (e.g., ) may not succeed due to incomplete referential integrity, it is also possible that the system automatically configures the deleted node again to make configuration valid, when a "resolve-system" parameter is carried. A referenced system node onced auto-configured in the datastore, will not be removed or updated automatically by the server even in cases like all references to it are deleted by the client or system configuration is no longer present in due to factors like device upgrade or system-controlled resources (e.g., HW unavailable) change. Comment: Should the server update configuration in that is copied from automatically (and manually?) during an upgrade? Jason: I think maybe servers that convert configuration during upgrade (a common approach) would want to convert/upgrade system config as well as any copied system config that exists in running. Ma, et al. Expires 5 January 2024 [Page 13] Internet-Draft System-defined Configuration July 2023 If the "resolve-system" parameter is not given by the client, the server should not modify in any way otherwise not specified by the client. Not using capitalized "SHOULD NOT" in the previous sentence is intentional. The intention is to bring awareness to the general need to not surprise clients with unexpected changes. It is desirable for clients to always opt into using mechanisms having server-side changes. This document enables a client to opt into this behavior using the "resolve-system" parameter. An example of this type of opt-in behavior can also be found in RFC 7317, which enables a client to opt into its behavior using a "$0$" prefix (see ianach:crypt-hash type defined in [RFC7317]). Support for the "resolve-system" parameter is OPTIONAL. Non-NMDA servers MAY also implement this parameter without implementing the system configuration datastore, which would only eliminate the ability to expose the system configuration via protocol operations. If a server implements , referenced system configuration is copied from into the target datastore(e.g., ) when the "resolve-system" parameter is used; otherwise it is an implementation decision where to copy referenced system configuration into the target datastore (e.g., ). Comments from Jason: Overall the resolve-system function may mean an expensive (time consuming) operation on the server side. Conceptually it may mean doing a validation on the running, and then when an error is hit, searching the 'system' datastore for something that could resolve that invalid aspect. Then running validation again and hitting the next error. It may require multiple passes (since some errors are dependent on the previous error being present or 'fixed'). 5.4. Modifying (Overriding) System Configuration In some cases, a server may allow some parts of system configuration to be modified. Modification of system configuration is achieved by the client writing configuration to that overrides the system configuration. Configurations defined in take precedence over system configuration nodes in if the server allows the nodes to be modified. Ma, et al. Expires 5 January 2024 [Page 14] Internet-Draft System-defined Configuration July 2023 For instance, list keys in system configuration can't be changed by a client, but other descendant nodes in a list entry may be modifiable or non-modifiable. Leafs and leaf-lists outside of lists may also be modifiable or non-modifiable. Even if some system configuration has been copied into earlier, whether it is modifiable or not in follows general YANG constraints and NACM rules, and other server-internal restrictions. If a system configuration node is non-modifiable, then writing a different value for that node MUST return an error. The immutability of system configuration is further defined in [I-D.ma-netmod-immutable-flag]. A server may also allow a client to add data nodes to a list entry in by writing those additional nodes in . Those additional data nodes may not exist in (i.e., an *addition* rather than an override). Comment 1: What if contains a set of values for a leaf-list, and a client configures another set of values for that leaf-list in , will the set of values in completely replace the set of values in ? Or the two sets of values are merged together? Comment 2: how "ordered-by user" lists and leaf-lists are merged? Do values go before or after, or is this a case where a full- replace is needed. 5.5. Examples This section shows some examples of server-configuring of automatically, declaring a system-defined node in explicitly, modifying a system-instantiated leaf's value and configuring descendant nodes of a system-defined node. For each example, the corresponding XML snippets are provided. 5.5.1. Server Configuring of Automatically In this subsection, the following fictional module is used: Ma, et al. Expires 5 January 2024 [Page 15] Internet-Draft System-defined Configuration July 2023 module example-application { yang-version 1.1; namespace "urn:example:application"; prefix "app"; import ietf-inet-types { prefix "inet"; } container applications { list application { key "name"; leaf name { type string; } leaf protocol { type enumeration { enum tcp; enum udp; } } leaf destination-port { type inet:port-number; } } } } The server may predefine some applications as a convenience for the clients. These predefined configurations are active only after being referenced by other configurations, which fall into the "inactive- until-referenced" system configuration as defined in Section 2. The system-instantiated application entries may be present in as follows: Ma, et al. Expires 5 January 2024 [Page 16] Internet-Draft System-defined Configuration July 2023 ftp tcp 21 tftp udp 69 smtp tcp 25 ... The client may also define its customized applications. Suppose the configuration of applications is present in as follows: my-app-1 tcp 2345 my-app-2 udp 69 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. Ma, et al. Expires 5 January 2024 [Page 17] Internet-Draft System-defined Configuration July 2023 module example-acl { yang-version 1.1; namespace "urn:example:acl"; prefix "acl"; import example-application { prefix "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 source_address { type inet:ipv4-prefix; } leaf dest_address { type inet:ipv4-prefix; } } } choice applications { leaf-list application { type leafref { path "/app:applications/app:application/app:name"; } } } } leaf packet_action { type enumeration { enum forward; enum drop; enum redirect; } } } } } Ma, et al. Expires 5 January 2024 [Page 18] Internet-Draft System-defined Configuration July 2023 If a client configures an ACL rule referencing system predefined nodes which are not present in , the client may issue an operation with the parameter "resolve-system" as follows: allow_access_to_ftp_tftp 198.51.100.0/24 192.0.2.0/24 ftp tftp my-app-1 forward Then following gives the configuration of applications in which is returned in the response to a follow-up operation: Ma, et al. Expires 5 January 2024 [Page 19] Internet-Draft System-defined Configuration July 2023 my-app-1 tcp 2345 my-app-2 udp 69 ftp tftp Then the configuration of applications is present in as follows: my-app-1 tcp 2345 my-app-2 udp 69 ftp tcp 21 tftp udp 69 Ma, et al. Expires 5 January 2024 [Page 20] Internet-Draft System-defined Configuration July 2023 Since the configuration of application "smtp" is not referenced by the client, and the server treats application "smtp" configuration as "inactive-until-referenced", it does not appear in but only in . 5.5.2. Declaring a System-defined Node in Explicitly It's also possible for a client to explicitly declare the system- defined configurations that are referenced. For instance, in the above example, the client MAY also explicitly configure the following system defined applications "ftp" and "tftp" only with the list key "name" before referencing: ftp tftp Then the client issues an operation to configure an ACL rule referencing applications "ftp" and "tftp" without the parameter "resolve-system" as follows: Ma, et al. Expires 5 January 2024 [Page 21] Internet-Draft System-defined Configuration July 2023 allow_access_to_ftp_tftp 198.51.100.0/24 192.0.2.0/24 ftp tftp my-app-1 forward Then following gives the configuration of applications in which is returned in the response to a follow-up operation, all the configuration of applications are explicitly configured by the client: Ma, et al. Expires 5 January 2024 [Page 22] Internet-Draft System-defined Configuration July 2023 my-app-1 tcp 2345 my-app-2 udp 69 ftp tftp Then the configuration of applications is present in as follows: my-app-1 tcp 2345 my-app-2 udp 69 ftp tcp 21 tftp udp 69 Ma, et al. Expires 5 January 2024 [Page 23] Internet-Draft System-defined Configuration July 2023 Since the application names "ftp" and "tftp" are explicitly configured by the client, they take precedence over the values in , the "origin" attribute will be set to "intended". 5.5.3. Modifying a System-instantiated Leaf's Value In this subsection, we will use this fictional QoS data model: module example-qos-policy { yang-version 1.1; namespace "urn:example:qos"; prefix "qos"; container qos-policies { list policy { key "name"; leaf name { type string; } list queue { key "queue-id"; leaf queue-id { type int32 { range "1..32"; } } leaf maximum-burst-size { type int32 { range "0..100"; } } } } } } Suppose a client creates a qos policy "my-policy" with 4 system instantiated queues(1~4). The configuration of qos-policies is present in as follows: Ma, et al. Expires 5 January 2024 [Page 24] Internet-Draft System-defined Configuration July 2023 my-policy 1 50 2 60 3 70 4 80 A client modifies the value of maximum-burst-size to 55 in queue-id 1: my-policy 1 55 Then, the configuration of qos-policies is present in as follows: Ma, et al. Expires 5 January 2024 [Page 25] Internet-Draft System-defined Configuration July 2023 my-policy 1 55 2 60 3 70 4 80 5.5.4. Configuring Descendant Nodes of a System-defined Node This subsection also uses the fictional interface YANG module defined in Appendix C.3 of [RFC8342]. Suppose the system provides a loopback interface (named "lo0") with a default IPv4 address of "127.0.0.1" and a default IPv6 address of "::1". The configuration of "lo0" interface is present in as follows: lo0 127.0.0.1 ::1 The configuration of "lo0" interface is present in as follows: Ma, et al. Expires 5 January 2024 [Page 26] Internet-Draft System-defined Configuration July 2023 lo0 127.0.0.1 ::1 Later on, the client further configures the description node of a "lo0" interface as follows: lo0 loopback Then the configuration of interface "lo0" is present in as follows: lo0 loopback 127.0.0.1 ::1 6. The "ietf-system-datastore" Module Ma, et al. Expires 5 January 2024 [Page 27] Internet-Draft System-defined Configuration July 2023 6.1. Data Model Overview This YANG module defines a new YANG identity named "system" that uses the "ds:datastore" identity defined in [RFC8342]. A client can discover the system configuration datastore support on the server by reading the YANG library information from the operational state datastore. Note that no new origin identity is defined in this document, the "or:system" origin Metadata Annotation [RFC7952] is used to indicate the origin of a data item is system. Support for the "origin" annotation is identified with the feature "origin" defined in [RFC8526]. 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]. 6.2. Example Usage This section gives an example of data retrieval from . The YANG module used are shown in Appendix C.2 of [RFC8342]. All the messages are presented in a protocol-independent manner. JSON is used only for its conciseness. Suppose the following data is added to : { "bgp": { "local-as": "64501", "peer-as": "64502", "peer": { "name": "2001:db8::2:3" } } } Ma, et al. Expires 5 January 2024 [Page 28] Internet-Draft System-defined Configuration July 2023 REQUEST (a or GET request sent from the NETCONF or RESTCONF client): Datastore: Target:/bgp An example of RESTCONF request: GET /restconf/ds/system/bgp HTTP/1.1 Host: example.com Accept: application/yang-data+xml RESPONSE ("local-port" leaf value is supplied by the system): { "bgp": { "peer": { "name": "2001:db8::2:3", "local-port": "60794" } } } 6.3. YANG Module file "ietf-system-datastore@2023-07-04.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 NETDOD (Network Modeling) Working Group"; contact "WG Web: https://datatracker.ietf.org/wg/netmod/ WG List: NETMOD WG list Author: Qiufang Ma Author: Qin Wu Ma, et al. Expires 5 January 2024 [Page 29] Internet-Draft System-defined Configuration July 2023 Author: Chong Feng "; description "This module defines a new YANG identity that uses the ds:datastore identity defined in [RFC8342]. 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 HHHH (https://www.rfc-editor.org/info/rfcHHHH); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2023-07-04 { 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."; } } 7. The "ietf-netconf-resolve-system" Module This YANG module is optional to implement. Ma, et al. Expires 5 January 2024 [Page 30] Internet-Draft System-defined Configuration July 2023 7.1. Data Model Overview This YANG module augments NETCONF , and operations with a new parameter "resolve-system" in the input parameters. If the "resolve-system" parameter is present, the server will copy the referenced system configuration into target datastore automatically. A NETCONF client can discover the "resolve- system" parameter support on the server by checking the YANG library information with "ietf-netconf-resolve-system" YANG module included from the operational state datastore. The following tree diagram [RFC8340] illustrates the "ietf-netconf- resolve-system" module: module: ietf-netconf-resolve-system augment /nc:edit-config/nc:input: +---w resolve-system? empty augment /nc:copy-config/nc:input: +---w resolve-system? empty augment /ncds:edit-data/ncds:input: +---w resolve-system? empty The following tree diagram [RFC8340] illustrates "edit-config", "copy-config" and "edit-data" rpcs defined in "ietf-netconf" and "ietf-netconf-nmda" respectively, augmented by "ietf-netconf-resolve- system" YANG module: rpcs: +---x edit-config | +---w input | +---w target | | +---w (config-target) | | +--:(candidate) | | | +---w candidate? empty {candidate}? | | +--:(running) | | +---w running? empty {writable-running}? | +---w default-operation? enumeration | +---w test-option? enumeration {validate}? | +---w error-option? enumeration | +---w (edit-content) | | +--:(config) | | | +---w config? | | +--:(url) | | +---w url? inet:uri {url}? | +---w resolve-system? empty +---x copy-config | +---w input | +---w target Ma, et al. Expires 5 January 2024 [Page 31] Internet-Draft System-defined Configuration July 2023 | | +---w (config-target) | | +--:(candidate) | | | +---w candidate? empty {candidate}? | | +--:(running) | | | +---w running? empty {writable-running}? | | +--:(startup) | | | +---w startup? empty {startup}? | | +--:(url) | | +---w url? inet:uri {url}? | +---w source | | +---w (config-source) | | +--:(candidate) | | | +---w candidate? empty {candidate}? | | +--:(running) | | | +---w running? empty | | +--:(startup) | | | +---w startup? empty {startup}? | | +--:(url) | | | +---w url? inet:uri {url}? | | +--:(config) | | +---w config? | +---w resolve-system? empty +---x edit-data +---w input +---w datastore ds:datastore-ref +---w default-operation? enumeration +---w (edit-content) | +--:(config) | | +---w config? | +--:(url) | +---w url? inet:uri {nc:url}? +---w resolve-system? empty 7.2. Example Usage This section gives an example of an request to reference system-defined data nodes which are not present in with a "resolve-system" parameter. A retrieval of to show the auto-copied referenced system configurations after the request is also given. The YANG module used is shown as follows, leafrefs refer to an existing name and address of an interface: Ma, et al. Expires 5 January 2024 [Page 32] Internet-Draft System-defined Configuration July 2023 module example-interface-management { yang-version 1.1; namespace "urn:example:interfacemgmt"; prefix "inm"; container interfaces { list interface { key name; leaf name { type string; } leaf description { type string; } leaf mtu { type uint16; } leaf ip-address { type inet:ip-address; } } } container default-address { leaf ifname { type leafref { path "../../interfaces/interface/name"; } } leaf address { type leafref { path "../../interfaces/interface[name = current()/../ifname]" + "/ip-address"; } } } } Image that the system provides a loopback interface (named "lo0") with a predefined MTU value of "1500" and a predefined IP address of "127.0.0.1", shows the following configuration of loopback interface: Ma, et al. Expires 5 January 2024 [Page 33] Internet-Draft System-defined Configuration July 2023 lo0 1500 127.0.0.1 The client sends an operation to add the configuration of default-address with a "resolve-system" parameter: lo0
127.0.0.1
 Since the "resolve-system" parameter is provided, the server will resolve any leafrefs to system configurations and copy the referenced system-defined nodes into automatically with the same value (i.e., the name and ip-address data nodes of lo0 interface) in at the end of operation constraint enforcement. After the processing, a positive response is returned: Then the client sends a operation towards : Ma, et al. Expires 5 January 2024 [Page 34] Internet-Draft System-defined Configuration July 2023 Given that the referenced interface "name" and "ip-address" of lo0 are configured by the server, the following response is returned: lo0 127.0.0.1 7.3. YANG Module file "ietf-netconf-resolve-system@2023-07-04.yang" module ietf-netconf-resolve-system { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-netconf-resolve-system"; prefix ncrs; import ietf-netconf { prefix nc; reference "RFC 6241: Network Configuration Protocol (NETCONF)"; } import ietf-netconf-nmda { prefix ncds; reference "RFC 8526: NETCONF Extensions to Support the Network Management Datastore Architecture"; } Ma, et al. Expires 5 January 2024 [Page 35] Internet-Draft System-defined Configuration July 2023 organization "IETF NETMOD (Network Modeling) Working Group"; contact "WG Web: WG List: Author: Qiufang Ma Author: Qin Wu Author: Chong Feng "; description "This module defines an extension to the NETCONF protocol that allows the NETCONF client to control whether the server is allowed to copy referenced system configuration automatically without the client doing so explicitly. 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 HHHH (https://www.rfc-editor.org/info/rfcHHHH); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2023-07-04 { description "Initial version."; reference "RFC XXXX: System-defined Configuration"; } grouping resolve-system-grouping { description Ma, et al. Expires 5 January 2024 [Page 36] Internet-Draft System-defined Configuration July 2023 "Define the resolve-system parameter grouping."; leaf resolve-system { type empty; description "When present, the server is allowed to automatically configure referenced system configuration into the target configuration datastore."; } } augment "/nc:edit-config/nc:input" { description "Allows the server to automatically configure referenced system configuration to make configuration valid."; uses resolve-system-grouping; } augment "/nc:copy-config/nc:input" { description "Allows the server to automatically configure referenced system configuration to make configuration valid."; uses resolve-system-grouping; } augment "/ncds:edit-data/ncds:input" { description "Allows the server to automatically configure referenced system configuration to make configuration valid."; uses resolve-system-grouping; } } 8. IANA Considerations 8.1. The "IETF XML" Registry This document registers two XML namespace URNs in the 'IETF XML registry', following the format defined in [RFC3688]. Ma, et al. Expires 5 January 2024 [Page 37] Internet-Draft System-defined Configuration July 2023 URI: urn:ietf:params:xml:ns:yang:ietf-system-datastore Registrant Contact: The IESG. XML: N/A, the requested URIs are XML namespaces. URI: urn:ietf:params:xml:ns:yang:ietf-netconf-resolve-system Registrant Contact: The IESG. XML: N/A, the requested URIs are XML namespaces. 8.2. 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: sys namespace: urn:ietf:params:xml:ns:yang:ietf-system-datatstore maintained by IANA: N RFC: XXXX // RFC Ed.: replace XXXX and remove this comment name: ietf-netconf-resolve-system prefix: ncrs namespace: urn:ietf:params:xml:ns:yang:ietf-netconf-resolve-system maintained by IANA: N RFC: XXXX // RFC Ed.: replace XXXX and remove this comment 8.3. RESTCONF Capability URN Registry This document registers a capability in the "RESTCONF Capability URNs" registry [RFC8040]: Index Capability Identifier ----------------------------------------------------------------------- :resolve-system urn:ietf:params:restconf:capability:resolve-system:1.0 9. Security Considerations 9.1. Regarding the "ietf-system-datastore" YANG Module The YANG module defined in this document extends the base operations for NETCONF [RFC6241] and RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. Ma, et al. Expires 5 January 2024 [Page 38] Internet-Draft System-defined Configuration July 2023 The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF users to a preconfigured subset of all available NETCONF protocol operations and content. 9.2. Regarding the "ietf-netconf-resolve-system" YANG Module The YANG module defined in this document extends the base operations for NETCONF [RFC6241] and [RFC8526]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. The Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF users to a preconfigured subset of all available NETCONF protocol operations and content. The security considerations for the base NETCONF protocol operations (see Section 9 of [RFC6241] apply to the new extended RPC operations defined in this document. 10. Contributors Kent Watsen Watsen Networks Email: kent+ietf@watsen.net Jan Lindblad Cisco Systems Email: jlindbla@cisco.com Chongfeng Xie China Telecom Beijing China Email: xiechf@chinatelecom.cn Jason Sterne Nokia Email: jason.sterne@nokia.com Ma, et al. Expires 5 January 2024 [Page 39] Internet-Draft System-defined Configuration July 2023 Acknowledgements The authors would like to thank for following for discussions and providing input to this document (ordered by first name): Alex Clemm, Andy Bierman, Balazs Lengyel, Juergen Schoenwaelder, Martin Bjorklund, Mohamed Boucadair, Robert Wilton and Timothy Carey. References Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF) Base Notifications", RFC 6470, DOI 10.17487/RFC6470, February 2012, . [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [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, . [RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "NETCONF Extensions to Support the Network Management Datastore Architecture", RFC 8526, DOI 10.17487/RFC8526, March 2019, . Ma, et al. Expires 5 January 2024 [Page 40] Internet-Draft System-defined Configuration July 2023 [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, . [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, September 2019, . Informative References [I-D.ma-netmod-immutable-flag] Ma, Q., Wu, Q., Lengyel, B., and H. Li, "YANG Extension and Metadata Annotation for Immutable Flag", Work in Progress, Internet-Draft, draft-ma-netmod-immutable-flag- 07, 25 May 2023, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for System Management", RFC 7317, DOI 10.17487/RFC7317, August 2014, . [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG", RFC 7952, DOI 10.17487/RFC7952, August 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . Ma, et al. Expires 5 January 2024 [Page 41] Internet-Draft System-defined Configuration July 2023 [RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of Documents Containing YANG Data Models", BCP 216, RFC 8407, DOI 10.17487/RFC8407, October 2018, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., and R. Wilton, "YANG Library", RFC 8525, DOI 10.17487/RFC8525, March 2019, . [RFC8808] Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808, August 2020, . Appendix A. Key Use Cases Following provides three use cases related to system-defined configuration lifecycle management. The simple interface data model defined in Appendix C.3 of [RFC8342] is used. For each use case, snippets of , , and are shown. A.1. Device Powers On : No configuration for "lo0" appears in ; : lo0 127.0.0.1 ::1 : Ma, et al. Expires 5 January 2024 [Page 42] Internet-Draft System-defined Configuration July 2023 lo0 127.0.0.1 ::1 : lo0 127.0.0.1 ::1 A.2. Client Commits Configuration If a client creates an interface "et-0/0/0" but the interface does not physically exist at this point: : et-0/0/0 Test interface : lo0 127.0.0.1 ::1 : Ma, et al. Expires 5 January 2024 [Page 43] Internet-Draft System-defined Configuration July 2023 lo0 127.0.0.1 ::1 et-0/0/0 Test interface : lo0 127.0.0.1 ::1 A.3. Operator Installs Card into a Chassis : et-0/0/0 Test interface : lo0 127.0.0.1 ::1 et-0/0/0 1500 Ma, et al. Expires 5 January 2024 [Page 44] Internet-Draft System-defined Configuration July 2023 : lo0 127.0.0.1 ::1 et-0/0/0 Test interface 1500 : lo0 127.0.0.1 ::1 et-0/0/0 Test interface 1500 Appendix B. Changes between Revisions v01 - v02 * Define referenced system configuration * better clarify "resolve-system" parameter * update Figure 2 in NMDA RFC * Editorial changes v00 - v01 * Clarify why client's explicit copy is not preferred but cannot be avoided if resolve-system parameter is not defined Ma, et al. Expires 5 January 2024 [Page 45] Internet-Draft System-defined Configuration July 2023 * Clarify active system configuration * Update the timing when the server's auto copy should be enforced if a resolve-system parameter is used * Editorial changes Appendix C. Open Issues tracking * Should the "with-origin" parameter be supported for ? 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 Feng Chong Huawei 101 Software Avenue, Yuhua District Nanjing Jiangsu, 210012 China Email: frank.fengchong@huawei.com Ma, et al. Expires 5 January 2024 [Page 46]