Alef Edge

xufeng.liu.ietf@gmail.com

Microsoft

jefftant.ietf@gmail.com

Individual

i_bryskin@yahoo.com

Telefonica

luismiguel.contrerasmurillo@telefonica.com

Huawei

bill.wu@huawei.com

Nokia

Sergio.belotti@nokia.com

Ciena

rrokui@ciena.com

Futurewei

aihuaguo.ietf@gmail.com

Huawei

italo.busi@huawei.com

TEAS Working Group An RFC 9543 network slice customer may utilize intent-based topologies to express resource reservation intentions within the provider's network. These customer-defined intent topologies allow customers to request shared resources for future connections that can be flexibly allocated and customized. Additionally, they provide an extensive level of control over underlay service paths within the network slice. This document describes a YANG data model for expressing customer intent topologies which can be used to enhance the RFC 9543 Network Slice Services in specific use cases, such as Network wholesale scenarios, where both topology and connectivity intents need to be expressed.

Introduction Network service providers utilize topologies to convey controlled information about their networks, such as bandwidth availability and connectivity, with customers, to facilitates customer service requests. Customers can also define intent-based topologies to streamline their internal operations. When requesting provider support for such custom topologies, they are considered as customer intent topologies. In the context of network slicing, customer intent topologies enables customers to express resource reservation preferences. These topologies allow flexible configuration and activation of network slices on demand. By providing full control over resource allocation timing and methods, customer intent topologies ensure that resources are consistently available. Moreover, the resources reserved via customer intent topologies can be shared across network slices created at different times or between different connectivity constructs within the same slice. Compared to network slices with dedicated full-mesh connectivity constructs between endpoints, network slices utilizing customer intent topologies can reduce overall resource requirements, offering significant economic benefits to the customer. Consider a hub-and-spoke network slice scenario where multiple customer spoke sites dynamically connect to a central hub site, sharing available bandwidth. By designing a customer intent topology with two virtual nodes - one representing all the spoke sites and the other representing the hub site - connected via a shared link, we proactively reserve resources for the shared connection. This ensures that bandwidth is readily available whenever the customer requires it. In contrast, achieving equivalent bandwidth assurance through individual dedicated connectivity constructs would necessitate creating separate links between each spoke and the hub, which would lead to substantial bandwidth inefficiency. Customer intent topology complements connectivity-based network slicing by providing customers a mechanism to specify additional underlay service paths to gain extensive control over specific or all connectivity constructs within the network slice, as outlined in . A customer intent topology is defined within the customer's context. It can include pure customer information or may also refer to network resources identifiable within the provider's context. There is a minimum level of a-prior shared knowledge between the customer and the provider, and this is the same information needed to supported connectivity-based network slice services as desdribed in . The provider's responsibility lies in understanding the customer intent topology request and translating that into suitable realization within their domain. This document introduces a YANG data model, based on , for configuring customer intent topologies. The YANG model extends the existing data model from , allowing customers to express desired service-level objectives (SLOs) and service-level expectations (SLEs) across different elements within the customer intent topology. The defined data model serves as an interface between customers and providers, enabling configurations and state retrievals for network slicing as a service. Customers can use this model to request or negotiate the creation of network slice instances. Additionally, they can incrementally adjust requirements for individual topology elements within the slice - for instance, adding or removing nodes or links, updating link bandwidth - and retrieve operational states. Leveraging other IETF mechanisms and data models, telemetry information can also be convey to the customer. The YANG model encompasses constructs that are independent of specific technologies, accommodating network slicing across diverse layers (including IP/MPLS, MPLS-TP, OTN, and WDM optical). As a result, this model serves as a foundational framework upon which technology-specific network slicing models - such as - can be developed. Section 3 of outlines that the use of customer intent topologies and resource reservation control is optional within network slicing. These features complement the data model defined in . The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) .

Use Case Applicability In Traffic Engineering (TE)-enabled networks like Layer-0/1 transport (OTN, MW, DWDM), customer intent topology is useful for routing RFC 9543 network slices across varied paths with TE constraints. Thus, most of the use cases for which this model target are transport oriented. Nonetheless, it is also relevant to non-transport networks like IP/MPLS, where customers may use intent topologies to influence the realization of network slices. These intents help build the logical view of the desired RFC 9543 Network Slice service (and its constituent parts), aiding providers in fulfilling slice requests and defining the service instantiation.

Use Case 1 : Multi-tenancy in Network Wholesaling A typical use case in which the customer intent topology is essential is the wholesale multi-tenant case. Here, customer C may acquire a network slice from provider P and resell sub-slices to other customers/tenants. The creation of these sub-slices within C's slice necessitates specifying a topology intent - reflecting the topology of C's purchased slice - as a key input parameter.

Use Case 2 : The current expression of slice requests leveraging on allows the customer to request distinct connectivity constructs as part of the same Network Resource Partition (NRP). The topology provided by the customer could imply different NRPs, instead. As an another example, from realization perspective even on the same NRP, a slice requests leveraging on without topology differentiation could imply the realization of all the connectivity constructs on the same manner. For instance, implementing all of them within the same VRF in a L3VPN. The usage of the topological views can help the provider to infer differentiated realization of some of the connectivity constructs, for instance, by implementing them on different VRFs. This can have operational advantages (e.g., adding new nodes / SDPs could affect / imply limit the necessary VRF reconfiguration only to the one including affected connectivity constructs). Finally, by using customer intent topology it can be easier for the slice provider to infer different technologies for sets of connectivity constructs of every topology segment (e.g., IP/MPLS, optical, microwave, etc).

Terminologies and Notations The following terminologies for describing network slices are defined in and are not redefined herein. Network Slice (NS) Network Slice Customer Network Slice Service Provider Network Slice Controller (NSC) Network Resource Partition (NRP) The following terms are defined and used in this document. Customer Intent Topology: A topology defined by the customer and provided as input to the network slice service provider (specifically, the Network Slice Controller or NSC). It represents the customer's desired network topology. Abstract Topology: A topology exposed to the customer by the network slice service provider prior to the creation of network slices. The provider may optionally uses an abstract topology to expose useful information, such as available resources to the customer, which can facilitate the build-up of customer intent topologies by the customer. NRP Topology: A topology internal to the NSC to facilitate the mapping of network slices to underlying network resources.

Tree Diagram Tree diagrams used in this document follow the notation defined in .

Prefixes in Data Node Names In this document, names of data nodes and other data model objects are prefixed using the standard prefix associated with the corresponding YANG imported modules, as shown in . Prefix YANG Module Reference yang ietf-yang-types inet ietf-inet-types nt ietf-network-topology nw ietf-network-topology tet ietf-te-topology ns-path ietf-ns-underlay-path RFC XXXX ns-topo ietf-ns-topo RFC XXXX ietf-nss ietf-network-slice-service RFC YYYY RFC Editor Note: Please replace XXXX with the RFC number assigned to this document. Please replace YYYY with the RFC number assigned to . Please remove this note.

Modeling Considerations A network slice topology is a cusomer intent topology modeled as network topology defined in , with augmentations. A new network type "network-slice" is defined in this document.
When a network topology data instance contains the network-slice network type, it represents an instance of a network slice topology. This data model augments the network topology model by incorporating intent-based Service-Level Objectives (SLOs) and Service-Level Expectations (SLEs). These apply to various components within the customer intent topology, including nodes, links, and termination points (TPs).

Relationship with Traffic Engineering (TE)-based Topology The model defined in this document can be combined through multi-inheritance with other topology data models, such as Traffic Engineering (TE) topologies described in or Optical Transport Network (OTN) topologies described in . This flexibility allows the creation of technology-specific customer intent topologies tailored to specific network requirements.

Relationship with Service Attachment Point (SAP) Topology introduces a YANG data model that represents an abstract view of the provider network topology. This model includes a list of Service Attachment Points (SAPs), where customer services can be connected. The SAP topology is made visible to customers by the provider before configuring network slice services. In contrast, the customer intent topology described in this document captures a customer's intentions, while the provider acts as the recipient of these intents. As a result, these two models serve distinct purposes. In certain scenarios, customers can leverage the SAP topology to construct customer intent topologies to aid in the realization of their intended network configurations. For instance, within a node of a customer intent topology, the Link Termination Point (LTP) identifiers may explicitly reference their supporting Termination Points (TPs), which correspond to the SAPs exposed in the provider's SAP model. However, the specifics of this mechanism fall beyond the scope of this document.

Relationship with ACTN Virtual Network (VN) and introduce the concept of a Virtual Network (VN), which can be presented to customers. These VNs are constructed from abstractions of the underlying networks, specifically those that are traffic-engineering (TE) capable. While VNs share similarities with RFC 9543 network slicing, they operate under the assumption of TE-capable networks. Two distinct types of VNs are defined: Type 1 VN: Modeled as a single abstract node with edge-to-edge connectivity between customer endpoints. Type 2 VN: Modeled as a single abstract node with an underlay topology, allowing configuration of intended underlay paths for connections within the single abstract node. The topologies for VNs, including both the single-node abstract topology and the underlay topology, can either be mutually agreed upon between the Customer Network Controller (CNC) and the Multi-Domain Service Coordinator (MDSC) prior to VN creation, or they can be created as part of VN instantiation by the customer. In the context of network slicing, defines a network slice service as a collection of connectivity constructs between pairs of Service Demarcation Points (SDPs). This concept closely resembles the Type 1 VN, which is implemented as a single abstract node. further elaborates on network slices by incorporating references to a customer intent topology based on . This approach aligns with the ACTN Type 2 VN, although without specifying the explicit use of such a topology. Consequently, the data model defined in this document serves as a complementary option to the data model outlined in . It empowers customers to define a customized intent topology specifically tailored for their network slices.

Consideration on Reusing ACTN VN for Network Slicing The ACTN VN model provides a self-consistent method for expressing connectivity intents (Type 1 VN) and optional path constraints (Type 2 VN) using TE metrics and TE objective functions defined in . Type 2 VN path constraints rely on Type 1 VN for expressing connectivity intents. On the other hand, RFC9543 network slice services provide connectivity intents equivalent to Type 1 VN, using SLO and SLE attributes in a technology-agnostic manner not tied to TE technologies. This distinction is detailed in Appendix D of . Reusing the Type 2 VN for defining customer intent topologies alongside the RFC9543 network slice service model would result in duplicated information for connectivity intents (SDPs and connectivity-constructs vs. LTPs and connectivity matrices), and additionally, would bind the network slice solution to TE technologies. The proposed models in this draft aim to deliver a solution equivalent to Type 2 VN within the context of network slicing. This complements the existing solution outlined in , while ensuring consistency.

Data Model Relationship The data model presented in this document builds upon the generic network topology model defined in . Other data models, including OTN Slicing (as defined in ), can leverage this extended model. The relationship of the related data models is illustrated in . Within this diagram, the box outlined with dotted lines specifically represents the data model defined in this document.

-----------------: Topology : | | : Model : +----------+ :..........: ]]>

Model Applicability Network slicing can be achieved through various technologies. The data model defined in this document serves as a means for configuring resource reservation-based network slices. In this approach, resources for network slices are reserved and represented using a customer intent topology. This topology can then be mapped to a network resource partition (NRP) and realized based on the scenarios outlined in . Network slices can be abstracted in various ways, depending on the specific requirements of the network slice customer. For instance, a customer might request a network slice with direct connectivity between pairs of Service Demarcation Points (SDPs). Within this network slice, each connectivity construct could be further supported by an end-to-end tunnel that follows a specific path defined in a customer intent topology, which the customer provides. The resources associated with each link are immediately commissioned during the network slice configuration process. Alternatively, a customer can request resources to be reserved for potential network slices through a customer intent topology. These reserved resources are not immediately commissioned at the time of the request. Instead, they serve as a pool of allocated resources that the customer can utilize to build network slices in the future. By adopting this approach, customers gain the flexibility to share resources across multiple endpoints and activate them on demand. In the example shown in , two topology intents named as Network Slice Blue and Network Slice Red, are created by separate customers and delivered to the network slice service provider. The provider maps the two intents to corresponding network resource partitions (NRPs) internally. In realizing the network resource partitions, node virtualization is used to separate and allocate resources in physical devices. Two virtual routers VR1 and VR2 are created over physical router R1, and two virtual routers VR3 and VR4 are created over physical router R2, respectively. Each of the virtual routers,as a partition of the physical router, takes a portion of the resources such as ports and memory in the physical router.
Depending on the requirements and the implementations, they may share certain resources such as processors, ASICs, and switch fabric. A network slice customer has the capability to configure customer intent topologies without needing any prior knowledge of the provider's network or resource availability. However, this approach could potentially create challenges for the provider in understanding and realizing the intended topology. Alternatively, the provider can choose to describe the available resources and capabilities in the form of an abstract topology, which is then exposed to the customer before network slice requests. By doing so, the provider empowers the customer to build their customized intent topologies based on this pre-exposed information. This approach streamlines the process, minimizing unnecessary negotiations between the customer and the provider. The process and the data models for the provider to expose abstract topologies are outside the scope of this document. The provider communicates the operational state of the customer intent topology, reflecting the allocated resources that result from negotiations between the customer and the provider. Subsequently, customers can process the requested customer intent topology and seamlessly integrate it into their own network topology. Importantly, this relationship between the customer and provider can be recursive. For instance, a customer who requests network slices can also serve as a provider, offering network slice services to its own customers further up the hierarchy. As an example, Appendix B. shows the JSON encoded data instances of the customer topology intent for Network Slice Blue.

YANG Model Overview The YANG data model in this draft consists of two modules for flexible use and augmentation: - The first YANG module defines a customer intent topology, with SLO and SLE associated with the topological constructs. - The second YANG module extends the YANG model defined in by adding underlay paths to the connectivity constructs. Within the YANG model, the following constructs and attributes are defined: - Network Topology: This represents a set of shared and reserved resources, organized as a virtual topology connecting all endpoints. Customers can utilize this network topology to define detailed connectivity paths traversing the topology. Additionally, it enables resource sharing between different endpoints. Service-Level Objectives (SLOs): These objectives are associated with various objects within the topology, including nodes, links, and termination points. SLOs provide guidelines for achieving specific performance or quality targets.

Model Tree Structure

Network Slice Topology Model Tree Structure

Network Slice Underlay Path Model Tree Structure

/nw:networks/network/network-id +--rw path-element* [index] +--rw index uint32 +--rw is-strict-hop? boolean +--rw (type)? +--:(node-hop) | +--rw node-id? nw:node-id +--:(link-hop) | +--rw link-id? nt:link-id +--:(tp-hop) +--rw tp-id? nt:tp-id augment /ietf-nss:network-slice-services/ietf-nss:slice-service /ietf-nss:connection-groups/ietf-nss:connection-group /ietf-nss:connectivity-construct/ietf-nss:slo-sle-policy /ietf-nss:custom/ietf-nss:service-slo-sle-policy /ietf-nss:sle-policy/ietf-nss:path-constraints: +--rw underlay-path +--rw network-ref? -> /nw:networks/network/network-id +--rw path-element* [index] +--rw index uint32 +--rw is-strict-hop? boolean +--rw (type)? +--:(node-hop) | +--rw node-id? nw:node-id +--:(link-hop) | +--rw link-id? nt:link-id +--:(tp-hop) +--rw tp-id? nt:tp-id augment /ietf-nss:network-slice-services/ietf-nss:slice-service /ietf-nss:connection-groups/ietf-nss:connection-group /ietf-nss:connectivity-construct/ietf-nss:type /ietf-nss:a2a/ietf-nss:a2a-sdp/ietf-nss:slo-sle-policy /ietf-nss:custom/ietf-nss:service-slo-sle-policy /ietf-nss:sle-policy/ietf-nss:path-constraints: +--rw underlay-path +--rw network-ref? -> /nw:networks/network/network-id +--rw path-element* [index] +--rw index uint32 +--rw is-strict-hop? boolean +--rw (type)? +--:(node-hop) | +--rw node-id? nw:node-id +--:(link-hop) | +--rw link-id? nt:link-id +--:(tp-hop) +--rw tp-id? nt:tp-id ]]>

YANG Modules

YANG Module for Network Slice Topology

file "ietf-ns-topo@2024-07-02.yang" module ietf-ns-topo { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-ns-topo"; prefix "ns-topo"; import ietf-network { prefix "nw"; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-network-topology { prefix "nt"; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-network-slice-service { prefix "ietf-nss"; reference "draft-ietf-teas-ietf-network-slice-nbi-yang-10: IETF Network Slice Service YANG Model"; } organization "IETF TEAS Working Group"; contact "WG Web: WG List: Editor: Xufeng Liu Editor: Italo Busi Editor: Aihua Guo Editor: Sergio Belotti Editor: Luis M. Contreras "; description "This module defines a base YANG data model for configuring customer intent topologies for RFC9543 network slices. The model fully conforms to the Network Management Datastore Architecture (NMDA). Copyright (c) 2023 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; see the RFC itself for full legal notices."; revision 2024-07-02 { description "Initial revision"; reference "RFC XXXX: IETF Network Slice Topology YANG Data Model"; } /* * Augmented data nodes */ /* network type augments */ augment "/nw:networks/nw:network/nw:network-types" { description "Defines the Network Slice topology type."; container network-slice { presence "Indicates a Network Slice topology"; description "Its presence identifies the Network Slice type."; } } /* network topology augments */ augment "/nw:networks/nw:network" { when "./nw:network-types/ns-topo:network-slice" { description "Augmentation parameters apply only for networks of type Network Slice topology."; } description "SLO and SLE for topology."; uses ietf-nss:service-slo-sle-policy; } /* network node augments */ augment "/nw:networks/nw:network/nw:node" { when "../nw:network-types/ns-topo:network-slice" { description "Augmentation parameters apply only for networks of type Network Slice topology."; } description "SLO and SLE for nodes."; uses ietf-nss:service-slo-sle-policy; } /* network node's termination point augments */ augment "/nw:networks/nw:network/nw:node" + "/nt:termination-point" { when "../../nw:network-types/ns-topo:network-slice" { description "Augmentation parameters apply only for networks of type Network Slice topology."; } description "SLO and SLE for termination points."; uses ietf-nss:service-slo-sle-policy; } /* network link augments */ augment "/nw:networks/nw:network/nt:link" { when "../nw:network-types/ns-topo:network-slice" { description "Augmentation parameters apply only for networks of type Network Slice topology."; } description "SLO and SLE for links."; uses ietf-nss:service-slo-sle-policy; } } ]]>

YANG Module for Network Slice Underlay Path

file "ietf-ns-underlay-path@2024-07-02.yang" module ietf-ns-underlay-path { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-ns-underlay-path"; prefix "ns-path"; import ietf-network { prefix "nw"; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-network-topology { prefix "nt"; reference "RFC 8345: A YANG Data Model for Network Topologies"; } import ietf-network-slice-service { prefix "ietf-nss"; reference "draft-ietf-teas-ietf-network-slice-nbi-yang-05: IETF Network Slice Service YANG Model"; } organization "IETF TEAS Working Group"; contact "WG Web: WG List: Editor: Xufeng Liu Editor: Italo Busi Editor: Aihua Guo Editor: Sergio Belotti Editor: Luis M. Contreras "; description "This module defines a base YANG data model for configuring the underlay path of connectivity intent over a customer intent topology for RFC9543 network slices. The model fully conforms to the Network Management Datastore Architecture (NMDA). Copyright (c) 2023 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; see the RFC itself for full legal notices."; revision 2024-07-02 { description "Initial revision"; reference "RFC XXXX: IETF Network Slice Topology YANG Data Model"; } /* * Groupings */ grouping underlay-path { description "Underlay explicit path within a customer intent topology."; container underlay-path { description "Defines an underlay explicit path within specific customer intent topology."; uses nw:network-ref; list path-element { key "index"; description "List of path elements."; leaf index { type uint32; description "Index of the hop within the underlay path."; } leaf is-strict-hop { type boolean; description "Indicate whether the hop is strict or loose"; } choice type { description "Type of the hop."; case node-hop { leaf node-id { type nw:node-id; description "Node identifier."; } } case link-hop { leaf link-id { type nt:link-id; description "Link identifier."; } } case tp-hop { leaf tp-id { type nt:tp-id; description "Termination Point (TP) identifier."; } } } } } } /* * Augmented data nodes */ augment "/ietf-nss:network-slice-services" + "/ietf-nss:slice-service" + "/ietf-nss:connection-groups" + "/ietf-nss:connection-group" + "/ietf-nss:slo-sle-policy" + "/ietf-nss:custom" + "/ietf-nss:service-slo-sle-policy" + "/ietf-nss:sle-policy" + "/ietf-nss:path-constraints" { description "Underlay path for connection group."; uses underlay-path; } augment "/ietf-nss:network-slice-services" + "/ietf-nss:slice-service" + "/ietf-nss:connection-groups" + "/ietf-nss:connection-group" + "/ietf-nss:connectivity-construct" + "/ietf-nss:slo-sle-policy" + "/ietf-nss:custom" + "/ietf-nss:service-slo-sle-policy" + "/ietf-nss:sle-policy" + "/ietf-nss:path-constraints" { description "Underlay path for connectivity construct."; uses underlay-path; } augment "/ietf-nss:network-slice-services" + "/ietf-nss:slice-service" + "/ietf-nss:connection-groups" + "/ietf-nss:connection-group" + "/ietf-nss:connectivity-construct" + "/ietf-nss:type" + "/ietf-nss:a2a" + "/ietf-nss:a2a-sdp" + "/ietf-nss:slo-sle-policy" + "/ietf-nss:custom" + "/ietf-nss:service-slo-sle-policy" + "/ietf-nss:sle-policy" + "/ietf-nss:path-constraints" { description "Underlay path for a2a connectivity constructs."; uses underlay-path; } } ]]>

Manageability Considerations To ensure the security and controllability of physical resource isolation, slice-based independent operation and management are required to achieve management isolation. Each network slice typically requires dedicated accounts, permissions, and resources for independent access and O&M. This mechanism is to guarantee the information isolation among slice tenants and to avoid resource conflicts. The access to slice management functions will only be permitted after successful security checks.

Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The NETCONF access control model provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. Considerations in Section 8 of are also applicable to their subtrees in the module defined in this document. Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. Considerations in Section 8 of are also applicable to their subtrees in the module defined in this document.

IANA Considerations It is proposed to IANA to assign new URIs from the "IETF XML Registry" as follows:

This document registers two YANG modules in the YANG Module Names registry .

This document describes network slicing in the context of networks built from IETF technologies. It defines the term "IETF Network Slice" to describe this type of network slice and establishes the general principles of network slicing in the IETF context. The document discusses the general framework for requesting and operating IETF Network Slices, the characteristics of an IETF Network Slice, the necessary system components and interfaces, and the mapping of abstract requests to more specific technologies. The document also discusses related considerations with monitoring and security. This document also provides definitions of related terms to enable consistent usage in other IETF documents that describe or use aspects of IETF Network Slices. 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). This document defines an abstract (generic, or base) YANG data model for network/service topologies and inventories. The data model serves as a base model that is augmented with technology-specific details in other, more specific topology and inventory data models. 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 introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021. This document defines a YANG data model for representing, retrieving, and manipulating Traffic Engineering (TE) Topologies. The model serves as a base model that other technology-specific TE topology models can augment. This document defines a YANG data model for representing an abstract view of the provider network topology that contains the points from which its services can be attached (e.g., basic connectivity, VPN, network slices). Also, the model can be used to retrieve the points where the services are actually being delivered to customers (including peer networks). This document augments the 'ietf-network' data model defined in RFC 8345 by adding the concept of Service Attachment Points (SAPs). The SAPs are the network reference points to which network services, such as Layer 3 Virtual Private Network (L3VPN) or Layer 2 Virtual Private Network (L2VPN), can be attached. One or multiple services can be bound to the same SAP. Both User-to-Network Interface (UNI) and Network-to-Network Interface (NNI) are supported in the SAP data model. Traffic Engineered (TE) networks have a variety of mechanisms to facilitate the separation of the data plane and control plane. They also have a range of management and provisioning protocols to configure and activate network resources. These mechanisms represent key technologies for enabling flexible and dynamic networking. The term "Traffic Engineered network" refers to a network that uses any connection-oriented technology under the control of a distributed or centralized control plane to support dynamic provisioning of end-to- end connectivity. Abstraction of network resources is a technique that can be applied to a single network domain or across multiple domains to create a single virtualized network that is under the control of a network operator or the customer of the operator that actually owns the network resources. This document provides a framework for Abstraction and Control of TE Networks (ACTN) to support virtual network services and connectivity services. 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). This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK] This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model. This document obsoletes RFC 6536. 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] This document defines encoding rules for representing configuration data, state data, parameters of Remote Procedure Call (RPC) operations or actions, and notifications defined using YANG as JavaScript Object Notation (JSON) text. Futurewei Technologies Telefonica Nokia Ciena CAICT China Mobile Alef Edge The requirement of slicing network resources with desired quality of service is emerging at every network technology, including the Optical Transport Networks (OTN). As a part of the transport network, OTN can provide hard pipes with guaranteed data isolation and deterministic low latency, which are highly demanded in the Service Level Agreement (SLA). This document describes a framework for OTN network slicing and defines YANG data models with OTN technology-specific augments deployed at both the north and south bound of the OTN network slice controller. Additional YANG data model augmentations will be defined in a future version of this draft. Telefonica Ciena Microsoft Huawei IBM Corporation Huawei Nokia This document describes a potential division in major functional components of an IETF Network Slice Controller (NSC) as well as references the data models required for supporting the requests of IETF network slice services and their realization. This document describes a potential way of structuring the IETF Network Slice Controller as well as how to use different data models being defined for IETF Network Slice Service provision (and how they are related). It is not the purpose of this document to standardize or constrain the implementation the IETF Network Slice Controller. Huawei Technologies Huawei Technologies Ciena Cisco Systems, Inc Cisco Systems, Inc This document defines a YANG data model for RFC 9543 Network Slice Service. The model can be used in the Network Slice Service interface between a customer and a provider that offers RFC 9543 Network Slice Services. Huawei Technologies Huawei Technologies Ciena Cisco Systems, Inc Cisco Systems, Inc This document defines a YANG data model for RFC 9543 Network Slice Service. The model can be used in the Network Slice Service interface between a customer and a provider that offers RFC 9543 Network Slice Services. Huawei Technologies Huawei Technologies IBM Corporation Nokia Telefonica This document defines a YANG data model for representing, retrieving, and manipulating Optical Transport Network (OTN) topologies. It is independent of control plane protocols and captures topological and resource-related information pertaining to OTN. Samsung Electronics Huawei Cisco Individual ETRI A Virtual Network (VN) is a network provided by a service provider to a customer for the customer to use in any way it wants as though it was a physical network. This document provides a YANG data model generally applicable to any mode of VN operations. This includes VN operations as per the Abstraction and Control of TE Networks (ACTN) framework.

Acknowledgments The authors would like to thank Danielle Ceccarelli, Bo Wu, Mohamed Boucadair, and Vishnu Beeram for providing valuable insights.

Data Tree for the Example in Section 3

Native Topology This section contains an example of an instance data tree in the JSON encoding . The example instantiates "ietf-network" for the topology of Network Slice Blue depicted in .