NETMOD Q. Ma, Ed. Internet-Draft Q. Wu Updates: 8342, 6241, 8526, 8040 (if approved) Huawei Intended status: Standards Track C. Feng Expires: 2 December 2024 31 May 2024 System-defined Configuration draft-ietf-netmod-system-config-06 Abstract This document defines how a management client and server handle YANG- modeled configuration data that is instantiated 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 expose system-defined configuration. 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." This Internet-Draft will expire on 2 December 2024. 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. Ma, et al. Expires 2 December 2024 [Page 1] Internet-Draft System-defined Configuration May 2024 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 2. Kinds of System Configuration . . . . . . . . . . . . . . . . 6 2.1. Immediately-Present . . . . . . . . . . . . . . . . . . . 6 2.2. Conditionally-Present . . . . . . . . . . . . . . . . . . 6 3. The System Configuration Datastore () . . . . . . . . 7 4. Static Characteristics of . . . . . . . . . . . . . 7 4.1. Read-only to Clients . . . . . . . . . . . . . . . . . . 7 4.2. May Change via Software Upgrades or Resource Changes . . 7 4.3. No Impact to . . . . . . . . . . . . . . . 8 5. Dynamic Behaviors . . . . . . . . . . . . . . . . . . . . . . 8 5.1. Conceptual Model of Datastores . . . . . . . . . . . . . 8 5.1.1. Origin Metadata Annotation . . . . . . . . . . . . . 10 5.2. Explicit Declaration of System Configuration . . . . . . 10 5.3. Servers Auto-configuring Referenced System Configuration ("resolve-system" parameter) . . . . . . . . . . . . . . 10 5.3.1. NETCONF Support for "resolve-system" Parameter . . . 11 5.3.2. RESTCONF Support for "resolve-system" Parameter . . . 12 5.3.2.1. Query Parameter . . . . . . . . . . . . . . . . . 12 5.4. Modifying (Overriding) System Configuration . . . . . . . 12 5.5. Examples . . . . . . . . . . . . . . . . . . . . . . . . 13 5.5.1. Server Configuring of Automatically . . . . 13 5.5.2. Declaring a System-defined Node in Explicitly . . . . . . . . . . . . . . . . . . . . . 18 5.5.3. Modifying a System-instantiated Leaf's Value . . . . 19 5.5.4. Configuring Descendant Nodes of a System-defined Node . . . . . . . . . . . . . . . . . . . . . . . . 20 6. Default Interactions . . . . . . . . . . . . . . . . . . . . 21 7. Relation to Other Datastores . . . . . . . . . . . . . . . . 21 7.1. The "factory-default" Datastore . . . . . . . . . . . . . 21 7.2. The "candidate" Datastore . . . . . . . . . . . . . . . . 21 8. The "ietf-system-datastore" Module . . . . . . . . . . . . . 22 8.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 22 8.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 23 8.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 24 9. The "ietf-netconf-resolve-system" Module . . . . . . . . . . 26 Ma, et al. Expires 2 December 2024 [Page 2] Internet-Draft System-defined Configuration May 2024 9.1. Data Model Overview . . . . . . . . . . . . . . . . . . . 26 9.2. Example Usage . . . . . . . . . . . . . . . . . . . . . . 26 9.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 26 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 10.1. The "IETF XML" Registry . . . . . . . . . . . . . . . . 29 10.2. The "YANG Module Names" Registry . . . . . . . . . . . . 29 10.3. NETCONF Capability URN Registry . . . . . . . . . . . . 29 10.4. RESTCONF Capability URN Registry . . . . . . . . . . . . 29 11. Security Considerations . . . . . . . . . . . . . . . . . . . 30 11.1. Regarding the "ietf-system-datastore" YANG Module . . . 30 11.2. Regarding the "ietf-netconf-resolve-system" YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 30 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30 12.1. Normative References . . . . . . . . . . . . . . . . . . 30 12.2. Informative References . . . . . . . . . . . . . . . . . 31 Appendix A. Key Use Cases . . . . . . . . . . . . . . . . . . . 33 A.1. Device Powers On . . . . . . . . . . . . . . . . . . . . 33 A.2. Client Commits Configuration . . . . . . . . . . . . . . 34 A.3. Operator Installs Card into a Chassis . . . . . . . . . . 35 Appendix B. Changes between Revisions . . . . . . . . . . . . . 36 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 38 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39 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 clients to reference a system-defined node which is not present in the datastore. 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 satisfy referential integrity constraints. Ma, et al. Expires 2 December 2024 [Page 3] Internet-Draft System-defined Configuration May 2024 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 Network Management Datastore Architecture (NMDA) defined in [RFC8342] with a read-only conventional configuration datastore called "system" to expose system-defined configuration. As an alternative to clients explicitly copying referenced system- defined configuration so that the datastore is valid, a "resolve- system" parameter is defined to allow the server to copy referenced system nodes automatically. This solution enables clients to reference nodes defined in , override system-provided values, and configure descendant nodes of system-defined configuration. 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 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 Ma, et al. Expires 2 December 2024 [Page 4] Internet-Draft System-defined Configuration May 2024 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 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 (Section 3), it also redefines the term "conventional configuration datastore" from [RFC8342] to add "system" to the list of conventional configuration datastores. Configuration in is merged with to create the contents of after the configuration transformations to (e.g., template expansion, removal of inactive configuration defined in [RFC8342]) have been performed (Section 5.1). The definition of "intended" origin metadata annotation identity is also updated (Section 5.1.1). Ma, et al. Expires 2 December 2024 [Page 5] Internet-Draft System-defined Configuration May 2024 1.4. Updates to RFC 6241 and RFC 8526 This document updates RFC 6241 to augment the NETCONF , , , and operations with an additional input parameter named "resolve-system", as specified in Section 5.3. This document also updates RFC 8526 to augment the NETCONF operation with the "resolve-system" parameter, as specified in Section 5.3. 1.5. Updates to RFC 8040 This document extends sections 4.8 and 9.1.1 in [RFC8040] to add a new query parameter "resolve-system" and corresponding query parameter capability URI (Section 5.3.2). 2. Kinds of System Configuration This document defines two types of system configuration: configuration that is generated in immediately when the device boots and configuration that is generated in only when specific conditions being met on a device, they 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 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. 2.2. Conditionally-Present Conditionally-present refers to system configuration which is generated in 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. Ma, et al. Expires 2 December 2024 [Page 6] Internet-Draft System-defined Configuration May 2024 3. The System Configuration Datastore () 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 . * 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" origin Metadata Annotation [RFC7952] is used to indicate the origin of a data item in system (Section 5.1.1). * 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. 4. Static Characteristics of 4.1. Read-only to Clients The system datastore is read-only (i.e., edits towards directly MUST be denied), though the client may be allowed to override the value of a system-initialized node (see Section 5.4). 4.2. May Change via Software Upgrades or Resource Changes The contents of 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) [RFC6470][RFC8639][RFC8641]. Ma, et al. Expires 2 December 2024 [Page 7] Internet-Draft System-defined Configuration May 2024 Generally speaking, any update of should not cause the automatic update of to not surprise clients with unexpected changes. In particular, the behavior of system data migration during software upgrade is outside the scope of this document. That said, here are some examples of how a server might handle this scenario ensuring remains accurate: * Servers migrate system configuration update in . * Servers reject the operation to change system configuration (e.g., software upgrade fails) and needs the client to update the configuration in as a prerequisite. Servers are recommended to include some hints in error responses to help clients understand how should be updated. 4.3. No Impact to This work intends to have no impact to and does not define any new origin identity beyond Section 5.3.4 of [RFC8342]. The existence of 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 Behaviors 5.1. Conceptual Model of Datastores Clients MAY reference nodes defined in , override system- provided values, and configure descendant nodes of system-defined configuration in . To ensure the validity of , configuration in is merged with to become , in which process, configuration appearing in takes precedence over the same node in . If 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 is merged with . Whenever configuration in changes, the server MUST also immediately update and validate . 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. Ma, et al. Expires 2 December 2024 [Page 8] Internet-Draft System-defined Configuration May 2024 +-------------+ +-----------+ | | | | | (ct, rw) |<---+ +---->| (ct, rw) | +-------------+ | | +-----------+ | | | | +-----------+ | +-----------+ | | | +------->| |<--------+ | (ct, ro) | | (ct, rw) | +-----------+ +-----------+ | | // configuration transformations, | | // e.g., removal of nodes marked | // merge | // 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 Figure 1: Architectural Model of Datastores Configuration in is non-deletable to clients, even though a client may delete a copied system node from . If system initializes a value for a particular leaf which is overridden by the client with a different value in , the client may delete it in , in which case system-initialized value defined in may still be in use and appear in . Ma, et al. Expires 2 December 2024 [Page 9] Internet-Draft System-defined Configuration May 2024 5.1.1. Origin Metadata Annotation This document does not define any new origin identity when interacts with and flows into . The "intended" identity of origin value defined in [RFC8342] to represent the origin of configuration provided by , this document updates its definition as origin source of configuration explicitly provided by , and allows a subset of configuration in that flows from yet is not configured or overridden explicitly in to use "system" as its origin value. Configuration copied from into has its origin value reported as "intended" when it flows into . 5.2. Explicit Declaration of System Configuration It is possible for a client to explicitly declare system configuration nodes with the same values as in , by configuring a node (list/leaf-list entry, leaf, etc.) in the target datastore (e.g., and ) that matches the same node and value in . The explicit declaration of system-defined nodes can be useful, for example, when the client does not support the "resolve-system" parameter but needs the datastore to be referentially complete. The client can explicitly copy the list entries (with at least the keys) that are referenced elsewhere in the datastore. 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. 5.3. Servers Auto-configuring Referenced System Configuration ("resolve-system" parameter) This document defines a new parameter "resolve-system" to the input for some of the NETCONF and RESTCONF operations. Clients that are aware of the "resolve-system" parameter MAY use this parameter to avoid the requirement to provide a referentially complete configuration. The "resolve-system" parameter is optional and has no value. If it is present, and the server supports this capability, the server MUST copy referenced system nodes into the target datastore (e.g., and ) where it is missing from without the client doing the copy/paste explicitly, to resolve any references not resolved by the client. If any child node of the copied Ma, et al. Expires 2 December 2024 [Page 10] Internet-Draft System-defined Configuration May 2024 configuration has its value being set by the system that is not the schema default value, it MUST also be copied into the target datastore (Section 6). The copy operation MUST NOT overwrite any explicit configuration in . The server copies the referenced system-defined nodes only when triggered by the "resolve- system" parameter. Legacy clients don't see any changes in the server behaviors. The server may automatically configure the list entries (with at least the keys) 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 configuration valid. There is no distinction between the configuration automatically configured by the server and the one explicitly declared by the client, e.g., a read back of the datastore (e.g., NETCONF // operation, or RESTCONF GET method) returns automatically configured nodes. Note that even though an auto-configured node is allowed to be deleted from the target datastore by the client, the system may automatically recreate the deleted node to make configuration valid, when a "resolve-system" parameter is carried. It is also possible that the operation request (e.g., ) may not succeed due to incomplete referential integrity. Support for the "resolve-system" parameter is OPTIONAL. Servers not supporting NMDA [RFC8342] MAY also implement this parameter without implementing the system configuration datastore, which would only eliminate the ability to retrieve the system configuration via protocol operations. If a server implements , referenced system configuration is copied from into the target datastore when the "resolve-system" parameter is used; otherwise it is an implementation decision where to copy referenced system configuration. 5.3.1. NETCONF Support for "resolve-system" Parameter This document defines a NETCONF protocol capability to indicate support for this parameter. NETCONF server that supports "resolve- system" parameter MUST advertise the following capability identifier: urn:ietf:params:netconf:capability:resolve-system:1.0 Ma, et al. Expires 2 December 2024 [Page 11] Internet-Draft System-defined Configuration May 2024 5.3.2. RESTCONF Support for "resolve-system" Parameter 5.3.2.1. Query Parameter The "resolve-system" parameter may be present in the request URI of some RESTCONF operations as shown in Figure 2. 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. +----------------+---------+-----------------------------------------+ | 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 2: RESTCONF "resolve-system" Query Parameter 5.3.2.1.1. 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 [RFC8040]: urn:ietf:params:restconf:capability:resolve-system:1.0 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. For instance, descendant nodes in a system-defined list entry may be modifiable or not, even if some system configuration has been copied into earlier. If a system node is non-modifiable, then writing a different value for that node MUST return an error during a , or operation, depending on the target datastore. The immutability of system configuration is defined in [I-D.ietf-netmod-immutable-flag]. Ma, et al. Expires 2 December 2024 [Page 12] Internet-Draft System-defined Configuration May 2024 5.5. Examples This section presents some sample data models and corresponding contents of various datastores with different dynamical behaviors above. The XML snippets are used only for examples. 5.5.1. Server Configuring of Automatically In this subsection, the following fictional module is used: 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 clients. The system-instantiated application entries may be present in as follows: Ma, et al. Expires 2 December 2024 [Page 13] Internet-Draft System-defined Configuration May 2024 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. module example-acl { yang-version 1.1; namespace "urn:example:acl"; prefix "acl"; import example-application { prefix "app"; } import ietf-inet-types { Ma, et al. Expires 2 December 2024 [Page 14] Internet-Draft System-defined Configuration May 2024 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 "/app:applications/app:application/app:name"; } } } } leaf packet-action { type enumeration { enum forward; enum drop; enum redirect; } } } } } If a client configures an ACL rule referencing system provided applications which are not present in , the client may issue an operation with the parameter "resolve-system" to the NETCONF server as follows: Ma, et al. Expires 2 December 2024 [Page 15] Internet-Draft System-defined Configuration May 2024 allow-access-to-ftp-tftp 198.51.100.0/24 192.0.2.0/24 ftp tftp my-app-1 forward The following gives the configuration of applications in which is returned in the response to a follow-up retrieval operation: Ma, et al. Expires 2 December 2024 [Page 16] Internet-Draft System-defined Configuration May 2024 my-app-1 tcp 2345 my-app-2 udp 69 ftp tftp And 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 2 December 2024 [Page 17] Internet-Draft System-defined Configuration May 2024 Since the configuration of application "smtp" is not referenced by the client, some implementation may consider it not to be "in use", hence it is omitted from but only present 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 instead of using the "resolve-system" parameter. 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": ftp tftp And the configuration of ACL rules referencing application "ftp" and "tftp" are as follows: allow-access-to-ftp-tftp 198.51.100.0/24 192.0.2.0/24 ftp tftp my-app-1 forward Once the data is written to , it makes no difference whether it is explicitly declared by the client or automatically copied by the server. The configuration for applications in and would be identical to the ones in Section 5.5.1. Ma, et al. Expires 2 December 2024 [Page 18] Internet-Draft System-defined Configuration May 2024 5.5.3. 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 "exif"; 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 a 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 as follows: lo0 65536 127.0.0.1 ::1 Ma, et al. Expires 2 December 2024 [Page 19] Internet-Draft System-defined Configuration May 2024 A client modifies the value of MTU to 9216 and adds the following configuration into : lo0 9216 Then the configuration of interfaces is present in as follows: lo0 65535 127.0.0.1 ::1 5.5.4. Configuring Descendant Nodes of a System-defined Node In the above example, image the client further configures the description node of a "lo0" interface in as follows: lo0 loopback The configuration of interface "lo0" is present in as follows: Ma, et al. Expires 2 December 2024 [Page 20] Internet-Draft System-defined Configuration May 2024 lo0 loopback 65535 127.0.0.1 ::1 6. Default Interactions should not contain the configuration using the schema default value, either specified in the "default" statement or described in the "description" statement. Any value provided by the system that is not the schema default value MUST be contained in . If system provides a value that is not the schema default value, and the node is not explicitly set by the client, it MUST be copied into the target datastore when its closest ancestor node needs to be copied to satisfy referential integrity constraints. 7. Relation to Other Datastores 7.1. The "factory-default" Datastore Any deletable system-provided configuration that is populated as part of 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. The RPC operation can reset to its factory default contents. 7.2. The "candidate" Datastore If the device supports the :candidate or :private-candidate [I-D.ietf-netconf-privcand] capability, a client may edit the candidate or private-candidate datastore without expecting it to be valid until a or operation takes place. The client may use the "resolve-system" parameter in one of the following situations: Ma, et al. Expires 2 December 2024 [Page 21] Internet-Draft System-defined Configuration May 2024 * The client makes an edit (e.g., NETCONF /, or RESTCONF edit operation) to the candidate/private-candidate datastore. This is possible, though may not be required. * The client issues a operation. * The client issues a operation. In particular, [I-D.ietf-netconf-privcand] defines the concept of conflict, the server's copy referenced system nodes triggered by "resolve-system" parameter might conflict with the contents of , the conflict resolution is no different than the resolution of conflict caused by configuration explicitly provided by the client. 8. The "ietf-system-datastore" Module 8.1. 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. 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]. Ma, et al. Expires 2 December 2024 [Page 22] Internet-Draft System-defined Configuration May 2024 8.2. Example Usage This section gives an example of data retrieval from . The fictional YANG module used following are from Appendix C.2 of [RFC8342]. container bgp { leaf local-as { type uint32; } leaf peer-as { type uint32; } list peer { key name; leaf name { type inet:ip-address; } leaf local-as { type uint32; description "... Defaults to ../local-as."; } leaf peer-as { type uint32; description "... Defaults to ../peer-as."; } leaf local-port { type inet:port; } leaf remote-port { type inet:port; default 179; } leaf state { config false; type enumeration { enum init; enum established; enum closing; } } } } All the messages are presented in a protocol-independent manner. JSON is used to not imply a preferred encoding in this document. Ma, et al. Expires 2 December 2024 [Page 23] Internet-Draft System-defined Configuration May 2024 Suppose the following BGP peer configuration is added to : { "bgp": { "local-as": "64501", "peer-as": "64502", "peer": { "name": "2001:db8::2:3", "local-as": "64501", "peer-as": "64502" } } } The local port and remote port are used when the BGP peer connection is established. Since both are not supplied explicitly in and , the default value for "bgp/peer/remote-port" is used, and there is no default statement for "bgp/peer/local-port", the system will select a value for it. So the contents of are shown as follows: { "bgp": { "peer": { "name": "2001:db8::2:3", "local-port": "60794" } } } 8.3. YANG Module file "ietf-system-datastore@2024-05-31.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 Ma, et al. Expires 2 December 2024 [Page 24] Internet-Draft System-defined Configuration May 2024 "WG Web: https://datatracker.ietf.org/wg/netmod/ WG List: NETMOD WG list Author: Qiufang Ma Author: Qin Wu Author: Chong Feng "; description "This module defines a new YANG identity that uses the ds:datastore 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. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2024-05-31 { 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."; } } Ma, et al. Expires 2 December 2024 [Page 25] Internet-Draft System-defined Configuration May 2024 9. The "ietf-netconf-resolve-system" Module This YANG module is optional to implement. 9.1. Data Model Overview 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 /nc:validate/nc:input: +---w resolve-system? empty augment /nc:commit/nc:input: +---w resolve-system? empty augment /ncds:edit-data/ncds:input: +---w resolve-system? empty 9.2. Example Usage Please refer to Section 5.5.1 for example usage of the "resolve- system" parameter. 9.3. YANG Module This module imports modules "ietf-netconf" and "ietf-netconf-nmda", defined in [RFC6241] and [RFC8526], respectively. file "ietf-netconf-resolve-system@2024-05-31.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; Ma, et al. Expires 2 December 2024 [Page 26] Internet-Draft System-defined Configuration May 2024 reference "RFC 8526: NETCONF Extensions to Support the Network Management Datastore Architecture"; } 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) 2024 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices. The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document are to be interpreted as described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here."; revision 2024-05-31 { description "Initial version."; reference Ma, et al. Expires 2 December 2024 [Page 27] Internet-Draft System-defined Configuration May 2024 "RFC XXXX: System-defined Configuration"; } grouping resolve-system-grouping { description "Define the resolve-system parameter grouping."; leaf resolve-system { type empty; description "When present, the server MUST copy referenced system configuration into the target configuration datastore where it is missing from without the client doing the copy/paste explicitly."; } } augment "/nc:edit-config/nc:input" { description "Adds the 'resolve-system' parameter to the input of the NETCONF operation."; uses resolve-system-grouping; } augment "/nc:copy-config/nc:input" { description "Adds the 'resolve-system' parameter to the input of the NETCONF operation."; uses resolve-system-grouping; } augment "/nc:validate/nc:input" { description "Adds the 'resolve-system' parameter to the input of the NETCONF operation."; uses resolve-system-grouping; } augment "/nc:commit/nc:input" { description "Adds the 'resolve-system' parameter to the input of the NETCONF operation."; uses resolve-system-grouping; } augment "/ncds:edit-data/ncds:input" { description "Adds the 'resolve-system' parameter to the input of the NETCONF operation."; uses resolve-system-grouping; } } Ma, et al. Expires 2 December 2024 [Page 28] Internet-Draft System-defined Configuration May 2024 10. IANA Considerations 10.1. 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. URI: urn:ietf:params:xml:ns:yang:ietf-netconf-resolve-system Registrant Contact: The IESG. XML: N/A, the requested URIs are XML namespaces. 10.2. 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 10.3. NETCONF Capability URN Registry This document registers the following capability identifier URN in the 'Network Configuration Protocol (NETCONF) Capability URNs' registry: urn:ietf:params:netconf:capability:resolve-system:1.0 10.4. RESTCONF Capability URN Registry This document registers a capability in the 'RESTCONF Capability URNs' registry [RFC8040]: Ma, et al. Expires 2 December 2024 [Page 29] Internet-Draft System-defined Configuration May 2024 Index Capability Identifier ----------------------------------------------------------------------- :resolve-system urn:ietf:params:restconf:capability:resolve-system:1.0 11. Security Considerations 11.1. 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]. 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. 11.2. 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. There is not any beyond the potential performance impacts of implementing the "resolve-system" parameter, which may mean employing some form of rate limiting or adapting the rate threshold might be a good idea to avoid DoS attacks. 12. References 12.1. Normative References Ma, et al. Expires 2 December 2024 [Page 30] Internet-Draft System-defined Configuration May 2024 [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, . [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, . 12.2. Informative References Ma, et al. Expires 2 December 2024 [Page 31] Internet-Draft System-defined Configuration May 2024 [I-D.ietf-netconf-privcand] Cumming, J. and R. Wills, "NETCONF Private Candidates", Work in Progress, Internet-Draft, draft-ietf-netconf- privcand-03, 30 May 2024, . [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-00, 18 March 2024, . [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, . [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, . [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, . Ma, et al. Expires 2 December 2024 [Page 32] Internet-Draft System-defined Configuration May 2024 [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 how interacts with other datastores (e.g., , , and ). The simple interface data model defined in Appendix C.3 of [RFC8342] is used. For each use case, corresponding sample configuration in , , and are shown. The XML snippets are used only for illustration purposes. A.1. Device Powers On When the device is powered on, suppose the system provides a loopback interface (named "lo0") which is not explicitly configured in . Thus, no configuration for interfaces appears in ; And the contents of are: lo0 127.0.0.1 ::1 In this case, the configuration of loopback interface is only present in , the exact configuration also shows up in . The contents of appear as follows: lo0 127.0.0.1 ::1 Ma, et al. Expires 2 December 2024 [Page 33] Internet-Draft System-defined Configuration May 2024 And will show the system-provided loopback interface: 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, what is in appears as follows: et-0/0/0 Test interface And the contents of keep unchanged since the interface is not physically present: lo0 127.0.0.1 ::1 The contents of represent the merged data of and : Ma, et al. Expires 2 December 2024 [Page 34] Internet-Draft System-defined Configuration May 2024 lo0 127.0.0.1 ::1 et-0/0/0 Test interface Since the interface named "eth-0/0/0" does not exist, the associated configuration is not present in , which appears as follows: lo0 127.0.0.1 ::1 A.3. Operator Installs Card into a Chassis When the interface is installed by the operator, the system will detect it and generate the associated configuration in . The contents of keep unchanged: et-0/0/0 Test interface And might appear as follows: Ma, et al. Expires 2 December 2024 [Page 35] Internet-Draft System-defined Configuration May 2024 lo0 127.0.0.1 ::1 et-0/0/0 1500 Then contains the merged configuration of and : lo0 127.0.0.1 ::1 et-0/0/0 Test interface 1500 And the contents of appear as follows: lo0 127.0.0.1 ::1 et-0/0/0 Test interface 1500 Appendix B. Changes between Revisions v05 - v06 Ma, et al. Expires 2 December 2024 [Page 36] Internet-Draft System-defined Configuration May 2024 * remove inactive-until-referenced system config * add a new section (sec.6) to clarify the interplay bewteen system config and defaults * add a new section (sec.7) to clarify relation to other datastores, which includes and / * leave the merge behavior of and unspecified * augment and PRC operation to support "resolve- system" parameter * editorial updates v04 - v05 * Explicitly state that system configuration copied from into have its origin value being reported as "intended" and update the examples accordingly to reflect it * Update the definition of "intended" origin identity in 8342 to allow a subset of configuration in to use "system" as origin value * State server behaviors of migrating updated system data into is beyond the scope of this document, and give a couple of implementation examples * Remove the related statement which mandates referenced system configuration must be copied into * Refine usage examples (e.g., fix validation errors, remove redundancy) v03 - v04 * Add some implementation consideration for "resolve-system" parameter * Define a NETCONF capability identifier for "resolve-system" parameter so that the client can discover if it is supported by the server. * state servers may upgrade copied system configuration in as well during device upgrade or licensing change. v02 - v03 Ma, et al. Expires 2 December 2024 [Page 37] Internet-Draft System-defined Configuration May 2024 * remove the merge mechanism related comments, as discussed in https://github.com/netconf-wg/netconf-next/issues/19 * Editorial changes 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 * 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 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, Alexander Clemm, and Timothy Carey. Contributors Ma, et al. Expires 2 December 2024 [Page 38] Internet-Draft System-defined Configuration May 2024 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 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 Ma, et al. Expires 2 December 2024 [Page 39]