]> Huawei

101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China maqiufang1@huawei.com

Huawei

101 Software Avenue, Yuhua District Jiangsu 210012 China bill.wu@huawei.com

Operations and Management Network Modeling YANG template NMDA NETCONF and RESTCONF protocols provide programmatic operation interfaces for accessing configuration data modeled by YANG. This document defines the use of YANG-based configuration template mechanism so that the configuration data could be defined as template and applied repeatedly to avoid the redundant definition of identical Configuration and ensure consistency of it. Discussion Venues Discussion of this document takes place on the Network Modeling Working Group mailing list (netmod@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction It is not unusual for the YANG data model to define some shared profiles that could be referenced in order to simplify the configuration of network services or functionalities. For example, defines a set of profiles at the network level which could be referred to under the node level to factorize some common configuration shared by a group of attachment circuits (ACs). However, it is not trivial to always take care of the definition of shared profiles/policies/templates during the design of every data model. There is a desire to make use of common YANG-based templates without relying on specific definition in YANG data models. NMDA allows the configuration templates to be defined in <running> and expanded in <intended>, but it does not specify details about how configuration templates could be created and applied. This document defines the use of configuration templates in the context of YANG-driven network management protocols such as NETCONF and RESTCONF . By defining a common set of nodes as a configuration template and applying the configuration template repeatedly, it avoids the redundant definition of identical configuration and also ensures consistency of it. Configuration template could be used based on any existing YANG data models, this document doesn't make any assumption on the YANG data model design, i.e., it does not rely on the shared profile/group defined in the YANG data model.

Editorial Note (To be removed by RFC Editor) Note to the RFC Editor: This section is to be removed prior to publication. This document contains placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document. Please apply the following replacements:

• XXXX --> the assigned RFC number for this draft
• 2024-08-27 --> the actual date of the publication of this document

Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. The meanings of the symbols in tree diagrams are defined in . This document uses the YANG terminology defined in . Besides, this document defines the following terminology:

configuration template:

A chunk of reusable configuration data that could be applied to the configuration repeatedly, in order to simplify the delivery of network configuration and ensure the consistency of it. A configuration template can also be called "hierarchical template", or "template" for short.

inherited template:

A configuration template that is applied in the configuration data tree or reused by other templates.

parent template:

A configuration template that is an inherited template.

Hierarchical Template Overview A configuration template must first be defined before it can be inherited . The creation, modification, and deletion of configuration templates are achieved by network management operations via NETCONF or RESTCONF protocols. The content of the configuration template must be an instantiated chunk of data starting from any level node in the module hierarchies. For example, provides an interface configuration template that sets "mtu" as 1500 for ethernet interfaces:

Example of An Interface template ]]>

The YANG data model of configuration templates is defined in .

Validity of Templates The contents of the template alone is not always sufficient to enforce the constraints of the data model. Some constraints may depend on configuration outside of the templates to satisfy, e.g., a list may contain a mandatory leaf node which is not defined in the template but explicitly provided by the client. However, servers should parse the template and enforce the constraints if it is possible during the processing of template creation, e.g., servers may validate type constraints for the leaf, including those defined in the type's "range", "length", and "pattern" properties. That said, if a template is applied in the configuration data tree, the results of the template configuration merging with configuration explicitly provided by the client MUST always be valid, as defined in .

Inheriting Templates This document allows configuration templates to be inherited by configuration nodes in the data tree or new templates at corresponding level. A node inherits at most one configuration template. If a configuration template is inherited by a node in the data tree, it acts as if the configuration defined in the template is contained and is merged with the configuration provided explicitly at the corresponding level in the data tree with the explicitly provided configuration takes precedence. If a configuration template is inherited by another new template, the configuration of the new template is the merging result of configuration defined in both templates with the new template takes precedence over its parent template. This is useful when some additional configuration is intended to be defined on the basis of the parent template. Any modification to the parent template also applies where the template is inherited.

The "stmt-extend" Metadata Template inheritance is indicated by declaring the metadata object called "stmt-extend". If the template is inherited by a node in the data tree, the metadata object is added to that specific node. If the template is inherited by other templates, the metadata object is added to the node at corresponding level of the template contents. The "stmt-extend" metadata MUST have only one value to specify the parent template identifier that is inherited. The encoding of "stmt-extend" metadata object follows the way defined in . For example, a client may configure physically present interfaces "eth0" and "eth1" with the list node "interface" inheriting the template defined in : eth0 eth1 ]]> And the above interface configuration renders the following expanded configuration: eth0 ianaift:ethernetCsmacd 1500 MTU value is set by template eth1 ianaift:ethernetCsmacd 1500 MTU value is set by template ]]>

Template Extension If there is some further configuration data that needs to be created but not included in the parent template, it can be provided at the corresponding level when inheriting the configuration template. For example, the client may want to define another template and provide an additional "enabled" leaf value on the basis of template defined in : ]]> And the above interface configuration defined in the template "interface-type-mtu-enabled" renders the following expanded configuration: ianaift:ethernetCsmacd 1500 MTU value is set by template true ]]> provides more examples of inheriting an existing template by indicating the "stmt-extend" metadata object.

Overriding Templates It may be desired to override some configuration in an existing template when it is interited. This may be achieved by directly editing the configuration template that is inherited, however, the parent template may have also been inherited by other instance nodes or templates, and direct modification of the parent template may yield unexpected results. This document allows a configuration template to be overridden by other templates or configuration explicitly provided by the client.

Modification If there is some configuration values that need to be modified, the desired value can be provided at the corresponding level when inheriting the configuation template. For example, a client may configure physically present interfaces "eth0" and "eth1" inheriting the template defined in , but the "mtu" value of "eth1" needs to be 9122, and the "description" value also needs to be modified accordingly: eth0 eth1 9122 MTU value is set explicitly ]]>

Deletion The deletion of configuration data is flagged by declaring the metadata object called "operation-tag" with a value "delete". If some node instance defined in the configuration template is intended to be deleted in the configuration explicitly by the client or by new templates, the "operation-tag" metadata annotation is added to that specific node. Servers MUST ignore this metadata if the configuration identified currently does not exist in the configuration template. The "operation-tag" metadata MUST have only one value to specify the intended operation. The encoding of "operation-tag" metadata object follows the way defined in . For example, a client may want to delete the "description" node instance defined in for interface "eth1", and the following shows the example configuration: eth0 eth1 9122 MTU value is set by template ]]> And it renders the following expanded configuration: eth0 ianaift:ethernetCsmacd 1500 MTU value is set by template eth1 ianaift:ethernetCsmacd 9122 ]]>

List/leaf-list Reordering There may be a desire to reorder some existing list/leaf-list entries defined in an existing template, or specify the ordering of new instances when they are created. It only applies to lists and leaf-lists indicated with the "ordered-by user" statement. The reordering of list/leaf-list entry data is flagged by declaring the metadata object called "operation-tag" with different values. The "operation-tag" used for reordering has one of the following values:

• position-first:

  The attached entry is positioned as the first entry in the list/leaf-list. There must be no more than one entry that is annotated as "position-first" within the same operation request.

• position-last:

  The attached entry is positioned as the last entry in the list/leaf-list. There must be no more than one entry that is annotated as "position-last" within the same operation request.

• position-before:

  The attached entry is positioned before some other specified entries in the list/leaf-list. This value MUST be followed by one or more space-seperated key values to indicate the entries that the attached entry is just positioned before. The "position-before" metadata and key values are seperated by colon ":". There must not be any other entries that use "position-before" to target the entry attached as "position-first" within the same operation rquest.

• position-after:

  The attached entry is positioned after some other specified entries in the list/leaf-list. This value MUST be followed by one or more space-seperated key values to indicate the entries that the attached entry is just positioned after. The "position-after" metadata and key values are seperated by colon ":". There must not be any other entries that use "position-after" to target the entry attached as "position-last" within the same operation request.

For example, the following template provides the user-ordered ACL configuration: ]]> If the client wants to create another template with an additional ACL entry named "deny-traffic-from-ftp" ordered as the first entry and ACL entry named "allow-access-from-tcp" as the last one: ]]> The client may also deliver the configuration defined in template "acl-rule-template" with some other additional ACL entries that is properly ordered: deny-access-to-ipv4 192.0.2.0/24 deny-access-to-ipv6 2001:db8::/32 ]]> The applied ACL configuration renders the following expanded configuration: deny-access-to-ipv4 192.0.2.0/24 deny-access-to-ipv6 2001:db8::/32 allow-access-from-tcp tcp permit allow-access-from-udp udp permit ]]>

Interaction with NMDA datastores Some implementation may have predefined configuration templates for the convenience of clients, which are present in <system> (if implemented, see ). In addition, clients can always define their own templates in <running>. However, configuration template data defined by "ietf-template" YANG data model should not be visible in <operational> until being inherited by a node in the data tree. If a node in the data tree inherits a configuration template, the configuration template does not expand in <running>, a read back of <running> returns what is sent by the client with the "stmt-extend" metadata attached to the specific node. Configuration template which is inherited or overridden by the node instance MUST be expanded in <intended>.

• Editor's Note: The read-back of <running> might break legacy clients that don't understand template?

Different Levels of Templates The configuration templates may be defined at different levels, depending on where it is used and maintained. For exmaple, A network-level template maintained by the software-defined networking (SDN) controller defines configuration that may be shared by multiple network elements. While device-level template maintained by the network element defines configuration that can only be applied to specific network element. Refer to for examples of network-level templates.

The "ietf-template" YANG Module

Data Model Overview The following tree diagram illustrates the "ietf-template" module: +--ro last-modified? yang:timestamp +--ro parent-template* -> ../../template/id +--ro inherited-by* union ]]>

• Editor's Note: Should the 'stmt-extend' and 'operation-tag' metadata annotations be defined here?

YANG Module WG List: Author: Qiufang Ma "; description "This module defines a template list with a RPC to expand the template. 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 2024-08-27 { description "Initial revision."; reference "RFC XXXX: YANG Templates"; } container templates { description "Specifies the template parameters."; list template { key id; description "The list of templates managed on this device."; leaf id { type string; description "The identifier of the template that uniquely identifies a template."; } leaf description { type string; description "A textual description of the template."; } anydata content { description "inline template content."; } leaf last-modified { type yang:timestamp; config false; description "Timestamp when the template is modified last time."; } leaf-list parent-template { type leafref { path "../../template/id"; } config false; description "The identifier of the template that this template is inherited from."; } leaf-list inherited-by { type union { type instance-identifier; type leafref { path "../../template/id"; } } config false; description "The data tree node or an identifier of the template that inherits this template."; } } } } ]]>

Security Considerations TODO Security

IANA Considerations

The "IETF XML" Registry This document registers the following URI in the "IETF XML Registry" .

The "YANG Module Names" Registry This document registers the following YANG module in the "YANG Module Names" registry .

References Normative References YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] Informative References Orange Juniper Telefonica Nokia Huawei Technologies This document specifies a network model for attachment circuits. The model can be used for the provisioning of attachment circuits prior or during service provisioning (e.g., VPN, Network Slice Service). A companion service model is specified in the YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service (ACaaS) (I-D.ietf- opsawg-teas-attachment-circuit). The module augments the base network ('ietf-network') and the Service Attachment Point (SAP) models with the detailed information for the provisioning of attachment circuits in Provider Edges (PEs). Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950. This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language. This document defines a YANG extension that allows for defining metadata annotations in YANG modules. The document also specifies XML and JSON encoding of annotations and other rules for annotating instances of YANG data nodes. Huawei Huawei The Network Management Datastore Architecture (NMDA) in RFC 8342 defines several configuration datastores holding configuration. The contents of these configuration datastores are controlled by clients. This document introduces the concept of system configuration datastore holding configuration controlled by the system on which a server is running. The system configuration can be referenced (e.g., leafref) by configuration explicitly created by clients. This document updates RFC 8342. Software-Defined Networking (SDN) has been one of the major buzz words of the networking industry for the past couple of years. And yet, no clear definition of what SDN actually covers has been broadly admitted so far. This document aims to clarify the SDN landscape by providing a perspective on requirements, issues, and other considerations about SDN, as seen from within a service provider environment. It is not meant to endlessly discuss what SDN truly means but rather to suggest a functional taxonomy of the techniques that can be used under an SDN umbrella and to elaborate on the various pending issues the combined activation of such techniques inevitably raises. As such, a definition of SDN is only mentioned for the sake of clarification. Software-Defined Networking (SDN) refers to a new approach for network programmability, that is, the capacity to initialize, control, change, and manage network behavior dynamically via open interfaces. SDN emphasizes the role of software in running networks through the introduction of an abstraction for the data forwarding plane and, by doing so, separates it from the control plane. This separation allows faster innovation cycles at both planes as experience has already shown. However, there is increasing confusion as to what exactly SDN is, what the layer structure is in an SDN architecture, and how layers interface with each other. This document, a product of the IRTF Software-Defined Networking Research Group (SDNRG), addresses these questions and provides a concise reference for the SDN research community based on relevant peer-reviewed literature, the RFC series, and relevant documents by other standards organizations.

template Syntax Some implementations support richer syntax in the template definition so that the use of configuration template could be more flexible.

Variable Declaration TBD

Loop Statement TBD

If-Else Statement TBD

Usage Examples This section provides some examples to show the use of templates. JSON encodings are used to not imply a preference in this document. The fictional data model used throughout this section is shown as follows:

Creating Templates The NTP configuration on multiple network devices may be consistent. To create a template for NTP configuration, the following template configuration might be sent to a SDN controller:

Inheriting Templates The operator may create another template with an additional NTP server instance when inheriting the template created in . The configuration is shown as follows: The configuration of template "template-ntp2" renders the following expanded configuration: the following shows the network-level ntp configuration using "template-ntp" and "template-ntp2" that may be sent to a SDN controller: And it renders the following expanded configuration:

Overriding Templates The client may override the template created in to specify the NTP server named "ntp-server-2" as the perferred one for device "ne-4": It is equivalent to the configuration as follows:

Acknowledgments TODO acknowledge.