IBM Corporation

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 IETF network slice may use an abstract topology to describe intended underlay for connectivities between slice endpoints. Abstract topologies help the customer to request network slices with shared resources amongst connections, and connections can be activated within the slice as needed. This document describes a YANG data model for managing and controlling abstract topologies for IETF network slices defined in RFC YYYY. [RFC EDITOR NOTE: Please replace RFC YYYY with the RFC number of draft-ietf-teas-ietf-network-slices once it has been published.

Introduction This document defines a YANG data model for representing, managing, and controlling IETF network slices as abstract network topologies, where the network slices are defined in . The defined data model is an interface between customers and providers for configurations and state retrievals, so as to support network slicing as a service. Through this model, a customer can learn the slicing capabilities and the available resources of the provider. A customer can request or negotiate with a network slicing provider to create an instance. The customer can incrementally update its requirements on individual topology elements in the slice instance, e.g., adding or removing a node or link, updating desired bandwidth of a link, and retrieve the operational states of these elements. With the help of other mechanisms and data models defined in IETF, the telemetry information can be published to the customer. The YANG model defines technology-agnostic constructs common to network slicing at network layers of different technologies, e.g. IP/MPLS(-TP), OTN and WDM. Therefore, this model may be used as a common base model on which other network slicing models, such as , may augments with technology-specific constructs. As described in Section 3 of , the data model defined in this document complements the data model defined in . In addition to the provider's view, the data model defined in this document models the Type 2 service defined in . The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) .

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 te-types ietf-te-types ns-topo ietf-ns-topo RFCXXXX RFC Editor Note: Please replace XXXX with the RFC number assigned to this document. Please remove this note.

Modeling Considerations An IETF network slice topology is 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 an IETF network slice topology.

Relationships to Related Topology Models There are several related YANG data models that have been defined in IETF. Some of these are: Network Topology Model: Defined in . Network Slicing Model: Defined in . OTN Slicing: Defined in . shows the relationships among these models. The box of dotted lines denotes the model defined in this document.

------+ | Model | | Model | | | RFC 8345 | +----+-----+ | +-----+----+ | | | |augments |references |augments | | | +----^-----+ | ......^..... | OTN | +----------: Network : | Slicing | augments : Slice : | Model >-----------------: Topology : | | : Model : +----------+ '''''''''''' ]]>

ACTN for Network Slicing Since ACTN topology data models are based on the network topology model defined in , the augmentations defined in this document are effective augmentations to the ACTN topology data models, resulting in making the ACTN framework and data models capable of slicing networks with the required network characteristics.

Model Applicability There are many technologies to achieve network slicing. The data model defined in this document can be used to configure resource-based network slices, where the resources of a network slice is represented in the form of an abstract network topology, which can then be mapped to a network resource partition (NRP) according to the scenarios defined in . Network slices may be abstracted differently depending on the requirement contained in the configuration provided by the slice customer. A customer may request a network slice to provide just connectivity between specified endpoints, in which case the network slice can be represented as a set of endpoint-to-endpoint links, with each link formed by an end-to-end tunnel across the underlying transport networks. The resources associated with each link of the slice is reserved and commissioned in the underlying physical network upon the completion of configuring the network slice and all the links are active. Alternatively a network slice can also be represented as an abstract topology when the customer requests the slice to share resources between multiple endpoints and to use the resources on demand. The abstract topology may consist of virtual nodes and virtual links, and their associated resources are reserved but not commissioned across the underlying transport networks. The customer can later commission resources within the slice dynamically using the NBI provided by the service provider. According to , the IETF Network Slice service customer might ask for some level of control of, e.g., to customize the service paths in a network slice. The abstract topology defined in this draft could serve to enable this capability and optimize the resource utilization for network slice connections activated on top of the abstract topology. In the example shown in , two network resource partitions are created by the provider to support the two network slice topology requests from the customers. 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. The network slice topology intent requested by the customers is then mapped to a corresponding network resource partition. The provider also reports the operational state of the topology, which shows the resources that are allocated. Customers can process the requested topology and integrate it with their own topology. As an example, Appendix B. shows the JSON encoded data instances of the customer topology intent for Network Slice Blue.

YANG Model Overview The following constructs and attributes are defined within the YANG model: Network topology, which represent set of shared, reserved resources organized as a virtual topology between all of the endpoints. A customer could use such network topology to define detailed connectivity path traversing the topology, and allow sharing of resources between its multiple endpoint pairs. Service-level objectives (SLOs) associated with different objects, including node, link, termination point of the topology.

Model Tree Structure

YANG Modules

file "ietf-ns-topo@2023-03-11.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-te-types { prefix "te-types"; reference "RFC 8776: Traffic Engineering Common YANG Types"; } import ietf-network-slice-service { prefix "ietf-nss"; reference "draft-ietf-teas-ietf-network-slice-nbi-yang-00: IETF Network Slice Service YANG Model"; } organization "IETF CCAMP 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 generic network slices in optical transport networks, e.g., Optical Transport Network (OTN). 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 2023-03-11 { description "Initial revision"; reference "RFC XXXX: IETF Network Slice Topology YANG Data Model"; } /* * Identities */ identity resize-option { description "Base identity for link or connectivity resizing options"; } identity resize-none { base resize-option; description "Not resizable"; } identity resize-with-hit { base resize-option; description "Resizable with traffic hits"; } identity resize-hitless { base resize-option; description "Hitless resizable"; } /* * Groupings */ grouping ns-topo-slo-sle-policy { description "Policy grouping for Transport Network Slices."; leaf optimization-criterion { type identityref { base te-types:objective-function-type; } description "Optimization criterion applied to this topology."; } leaf resize-requirement { type identityref { base resize-option; } description "Indicates resizing requirments"; } leaf service-info { type string; description "Describe type of services running on the slice. It may be useful information to help the slice controller to optimize resource allocation"; } } grouping ns-topo-steering-constraints { description "Policy grouping for specifying steering constraints for Transport Network Slices."; leaf disjointness { type te-types:te-path-disjointness; description "Indicate the level of disjointness for slice resources."; } } /* * 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 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 "Augment only for Network Slice topology."; } description "Augment topology configuration and state."; uses ietf-nss:service-slo-sle-policy; } augment "/nw:networks/nw:network" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" { when "../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment topology configuration and state."; uses ns-topo-slo-sle-policy; } augment "/nw:networks/nw:network" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" + "/ns-topo:steering-constraints" { when "../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment topology configuration and state."; uses ns-topo-steering-constraints; } /* network node augments */ augment "/nw:networks/nw:network/nw:node" { when "../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment node configuration and state."; uses ietf-nss:service-slo-sle-policy; } augment "/nw:networks/nw:network/nw:node" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" { when "../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment node configuration and state."; uses ns-topo-slo-sle-policy; } augment "/nw:networks/nw:network/nw:node" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" + "/ns-topo:steering-constraints" { when "../../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment IETF network slice services to include steering constraints for nodes."; uses ns-topo-steering-constraints; } /* 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 "Augment only for Network Slice topology."; } description "Augment node configuration and state."; uses ietf-nss:service-slo-sle-policy; } augment "/nw:networks/nw:network/nw:node" + "/nt:termination-point" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" { when "../../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment node configuration and state."; uses ns-topo-slo-sle-policy; } /* network link augments */ augment "/nw:networks/nw:network/nt:link" { when "../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment link configuration and state."; uses ietf-nss:service-slo-sle-policy; } augment "/nw:networks/nw:network/nt:link" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" { when "../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment link configuration and state."; uses ns-topo-slo-sle-policy; } augment "/nw:networks/nw:network/nt:link" + "/ns-topo:slo-sle-policy" + "/ns-topo:custom" + "/ns-topo:service-slo-sle-policy" + "/ns-topo:steering-constraints" { when "../../../nw:network-types/ns-topo:network-slice" { description "Augment only for Network Slice topology."; } description "Augment IETF network slice services to include steering constraints for links within a resource-based transport network slice."; uses ns-topo-steering-constraints; } } ]]>

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 a YANG module in the YANG Module Names registry .

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). 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 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. 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 collection of common data types and groupings in YANG data modeling language. These derived common types and groupings are intended to be imported by modules that model Traffic Engineering (TE) configuration and state capabilities. 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. Old Dog Consulting Juniper Networks Ciena NTT Futurewei Telefonica Microsoft Inc. This document describes network slicing in the context of networks built from IETF technologies. It defines the term "IETF 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 how abstract requests can be mapped 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. Futurewei Technologies Telefonica Nokia Ciena CAICT China Mobile IBM Corporation 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 a YANG data model augmentation of the OTN topology model. 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 the 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. Huawei Technologies Huawei Technologies Ciena Cisco Systems, Inc China Mobile Cisco Systems, Inc This document defines a YANG data model for the IETF Network Slice Service. The model can be used in the IETF Network Slice Service interface between a customer and a provider that offers IETF Network Slices. 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. Samsung Huawei Cisco ETRI Nokia Abstraction and Control of TE Networks (ACTN) refers to the set of virtual network operations needed to orchestrate, control and manage large-scale multi-domain TE networks, so as to facilitate network programmability, automation, efficient resource sharing, and end-to- end virtual service aware connectivity and network function virtualization services. This document explains how the different types of YANG models defined in the Operations and Management Area and in the Routing Area are applicable to the ACTN framework. This document also shows how the ACTN architecture can be satisfied using classes of data model that have already been defined, and discusses the applicability of specific data models that are under development. It also highlights where new data models may need to be developed.

Acknowledgments The TEAS Network Slicing Design Team (NSDT) members included Aijun Wang, Dong Jie, Eric Gray, Jari Arkko, Jeff Tantsura, John E Drake, Luis M. Contreras, Rakesh Gandhi, Ran Chen, Reza Rokui, Ricard Vilalta, Ron Bonica, Sergio Belotti, Tomonobu Niwa, Xuesong Geng, and Xufeng Liu.

Data Tree for the Example in Section 3.1

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 .