]> Telefonica

oscar.gonzalezdedios@telefonica.com

Nokia

samier.barguil_giraldo@nokia.com

Nokia

victor.lopez@nokia.com

Operations and Management nmop This document defines a YANG data model for representing an abstracted view of a network topology that contains Open Shortest Path First (OSPF) information. This document augments the 'ietf-network' data model by adding OSPF concepts and explains how the data model can be used to represent the OSPF topology. The YANG data model defined in this document conforms to the Network Management Datastore Architecture (NMDA).

Introduction Network operators perform the capacity planning for their networks and run regular what-if scenarios analysis based on representations of the real network. Those what-if analysis and capacity planning processes require, among other information, a topological view (domains, nodes, links, network interconnection) of the deployed network. This document defines a YANG data model representing an abstracted view of a network topology containing Open Shortest Path First (OSPF). It covers the topology of IP/MPLS networks running OSPF as Interior Gateway Protocol (IGP) protocol. The proposed YANG model augments the "A YANG Data Model for Network Topologies" and "A YANG Data Model for Layer 3 Topologies" by adding OSPF concepts. It is worth to highlight that the Yang model can also be used together with and when Traffic engineering characteristics are required in the topological view. This YANG data model can be used to export the OSPF related topology directly from a network controller to Operation Support System (OSS) tools or to a higher level controller. Note that the YANG model is in this document strictly adheres to the concepts (and the YANG module) in "A YANG Data Model for Network Topologies" and "A YANG Data Model for Layer 3 Topologies" . While investigating the OSFP topology, some limitations have discovered in , regarding how the digital map can be represented. Those limitations (and potential improvements) are covered in . This document explains the scope and purpose of the OSPF topology model and how the topology and service models fit together. The YANG data model defined in this document conforms to the Network Management Datastore Architecture .

Terminology and Notations This document assumes that the reader is familiar with OSPF and the contents of . The document uses terms from those documents. The terminology for describing YANG data models is found in , and . The term Digital Twin, Digital Map, Digital Map Modelling, Digital Map Model, Digital Map Data, and Topology are specified in .

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 , when, and only when, they appear in all capitals, as shown here.

Tree Diagram Authors include a simplified graphical representation of the data model specified in of this document. The meaning of the symbols in these diagrams is defined in .

Prefix 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 the following table. Prefixes and corresponding YANG modules

Prefix	Yang Module	Reference
ospfnt	ietf-l3-ospf-topology	RFCXXX
yang	ietf-yang-types

RFC Editor Note: Please replace XXXX with the RFC number assigned to this document. Please remove this note.

Use Cases Use cases for this document are the same than explained in . Here are included for completeness and discussion. Future versions may consider removing them. This information is required in the IP/MPLS planning process to properly assess the required network resources to meet the traffic demands in normal and failure scenarios. Network operators perform the capacity planning for their networks and run regular what-if scenarios analysis based on representations of the real network. Those what-if analysis and capacity planning processes require, among other information, a topological view (domains, nodes, links, network interconnection) of the deployed network. The standardization of an abstracted view of the OSPF topology model as NorthBound Interface (NBI) of Software Defined Networking (SDN) controllers allows the unified query of the OSFP topology in order to inject this information into third party tools covering specialized cases. The OSFP topological model should export enough OSFP information to permit these tools to simulate the IP routing. By mapping the traffic demand, ideally at the IP flow level, to the topology, we can simulate the traffic growth, evaluating this way its effect on the routing and quality of service. That is, simulating how IP-level traffic demands would be forwarded, after OSPF convergence is reached, and from there estimating, using appropriate mathematical models, related KPIs like the occupation in the links or end-to-end latencies. In summary, the network-wide view of the OSFP topology enables multiple use cases:

• Network design: verifying that the actual deployed OSFP network conforms to the planned design.
• Capacity planning. Dimensioning or redesign of the IP infrastructure to satisfy target KPI metrics under existing or forecasted traffic demands.
• What-if analysis. Estimation of the network KPIs in modified network situations. For instance, failure situations, traffic anomaly situations, addition or deletion of new adjacencies, IGP weight reconfigurations, etc.
• Failure analysis. Systematic and massive test of the network under multiple simulated failure situations, evaluating the network fault tolerance properties, and using mathematical models to derive statistical network availability metrics.

Relationship with the OSPF YANG Model specifies a YANG data model that can be used to configure and manage the OSPF protocol on network elements. This data model covers the configuration of an OSPF routing protocol instance, as well as the retrieval of OSPF operational states. is still expected to be used for individual network elements configuration and monitoring. On the other hand, the proposed YANG model in this document covers the abstracted view of the entire network topology containing OSPF. As such, this model is aimed at being available via the NBI of an SDN controller.

Relationship with Digital Map As described in , the Digital Map provides the core multi-layer topology model and data for the digital twin and connects them to the other digital twin models and data. The Digital Map Modelling defines the core topological entities, their role in the network, core properties, and relationships both inside each layer and between the layers. The Digital Map Model is a basic topological model that is linked to other functional parts of the digital twin and connects them all: configuration, maintenance, assurance (KPIs, status, health, symptoms), Traffic Engineering (TE), different behaviors and actions, simulation, emulation, mathematical abstractions, AI algorithms, etc. As such the IGP topology of the Digital Map (in this case, OSPF) is just one of the layers of the Digital Map, for specific user (the network operator in charge of the IGP) for specific IGP use cases as described before.

YANG Data Model for OSPF Topology The abstract (base) network data model is defined in the "ietf-network" module of . The OSPF-topology builds on the network data model defined in the "ietf-network" module , augmenting the nodes with OSPF information, which anchor the links and are contained in nodes. There is a set of parameters and augmentations that are included at the node level. Each parameter and description are detailed following:

• Network-types: Its presence identifies the OSPF topology type. Thus, the network type MUST be ospf-topology.
• OSPF timer attributes: Identifies the node timer attributes configured in the network element. They are wait timer, rapid delay, slow delay, and the timer type (linear or exponential back-off).
• OSPF status: contains the neighbours' information.

The following figure is based on the Figure 1 from , where the example-ospf-topology is replaced with ietf-l3-ospf-topology and where arrows show how the modules augment each other.

OSPF Topology module structure

A second set of parameters, along with augmentations, is included at the link and termination point level. Each parameter is listed as follows:

• Interface-type
• Area ID
• Metric
• Passive mode

RFC8345 Limitations for the OSPF Modeling There are some limitations in the that are explained in more detail in . The current version of the ietf-l3-ospf-topology module is based on the current version of .

OSPF Topology Tree Diagram below shows the tree diagram of the YANG data model defined in module ietf-l3-ospf-topology.yang ().

OSPF Topology tree diagram

YANG Model for OSPF topology Following the YANG model is presented.

OSPF Topology YANG module WG List: Editor: Oscar Gonzalez de Dios Editor: Samier Barguil Editor: Victor Lopez "; description "This module defines a model for Layer 3 OSPF topologies. 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."; revision 2022-03-07 { description "Initial version"; reference "RFC XXXX: A YANG Data Model for Open Shortest Path First (OSPF) Topology"; } typedef area-id-type { type yang:dotted-quad; description "An identifier for the OSPFv2 area."; reference "RFC 2328: OSPF Version 2"; } identity inf-type { description "Identity for the OSPF interface type."; reference "RFC 2328: OSPF Version 2"; } identity nbma { base inf-type; description "Identity for the NBMA interface."; reference "RFC 2328: OSPF Version 2"; } identity p2mp { base inf-type; description "Identity for the p2mp interface."; reference "RFC 2328: OSPF Version 2"; } identity p2mp-over-lan { base inf-type; description "Identity for the p2mp-over-lan interface."; reference "RFC 2328: OSPF Version 2"; } identity p2p { base inf-type; description "Identity for the p2p interface."; reference "RFC 2328: OSPF Version 2"; } grouping ospfv2-topology-type { description "Identifies the topology type to be OSPF v2."; container ospfv2-topology { presence "indicates OSPF v2 topology"; description "The presence of the container node indicates OSPF v2 topology"; } } grouping ospfv2-node-attributes { description "OSPF v2 node scope attributes"; container ospf-timer-attributes { description "Contains OSPFv2 node timer attributes"; leaf wait-timer { type uint32; units msec; description "The amount of time to wait without detecting SPF trigger events before going back to the rapid delay."; reference "RFC 8541: SPF Impact on IGP Micro-loops"; } leaf rapid-delay { type uint32; units msec; description "The amount of time to wait before running SPF after the initial SPF trigger event."; reference "RFC 8541: SPF Impact on IGP Micro-loops"; } leaf slow-delay { type uint32; units msec; description "The amount of time to wait before running an SPF."; reference "RFC 8541: SPF Impact on IGP Micro-loops"; } leaf timer-type { type enumeration { enum LINEAR_BACKOFF { description "The link state routing protocol uses linear back-off."; } enum EXPONENTIAL_BACKOFF { description "The link state routing protocol uses exponential back-off."; } } description "The timer mode that is utilised by the SPF algorithm."; reference "RFC 8541: SPF Impact on IGP Micro-loops"; } } } grouping ospfv2-termination-point-attributes { description "OSPF termination point scope attributes"; container ospfv2-termination-point-attributes { description "Indicates the termination point from the which the OSPF is configured. A termination point can be a physical port, an interface, etc."; leaf interface-type { type identityref { base inf-type ; } description "OSPF interface type."; reference "RFC 2328: OSPF Version 2"; } leaf area-id { type area-id-type; description "An identifier for the OSPFv2 area."; reference "RFC 2328: OSPF Version 2"; } leaf metric { type uint64; description "OSFP Protocol metric"; reference "RFC 2328: OSPF Version 2"; } leaf is-passive{ type boolean; description "Interface passive mode"; reference "RFC 2328: OSPF Version 2"; } } } augment "/nw:networks/nw:network/nw:network-types" { description "Introduces new network type for L3 Unicast topology"; uses ospfv2-topology-type; } augment "/nw:networks/nw:network/nw:node/" +"l3t:l3-node-attributes" { when "/nw:networks/nw:network/nw:network-types/" +"ospfnt:ospfv2-topology" { description "Augmentation parameters apply only for networks with OSPF topology"; } description "OSPF node-level attributes "; uses ospfv2-node-attributes; } augment "/nw:networks/nw:network/" + "nt:link/l3t:l3-link-attributes" { when "/nw:networks/nw:network/nw:network-types/" +"ospfnt:ospfv2-topology" { description "Augmentation parameters apply only for networks with OSFP topology"; } description "Augments topology link configuration"; uses ospfv2-termination-point-attributes; } augment "/nw:networks/nw:network/nw:node/" +"nt:termination-point/l3t:l3-termination-point-attributes" { when "/nw:networks/nw:network/nw:network-types/" +"ospfnt:ospfv2-topology" { description "Augmentation parameters apply only for networks with OSFP topology"; } description "Augments topology termination point configuration"; uses ospfv2-termination-point-attributes; } } ]]>

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 {!RFC6241}} 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 Network Configuration Access Control Model (NACM) 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.

IANA Considerations This document registers the following namespace URIs in the IETF XML registry : This document registers the following YANG module in the YANG Module Names registry :

Implementation Status This section will be used to track the status of the implementations of the model. It is aimed at being removed if the document becomes RFC.

References Normative References 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 Layer 3 network topologies. 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. Huawei Huawei Telefonica Swisscom Swisscom Orange This document shares experience in modelling Digital Map based on the IETF RFC 8345 topology YANG modules and some of its augmentations. First, the concept of Digital Map is defined and its connection to the Digital Twin is explained. Next to Digital Map requirements and use cases, the document identifies a set of open issues encountered during the modelling phases, the missing features in RFC 8345, and some perspectives on how to address them. Discussion Venues This note is to be removed before publishing as an RFC. Source for this draft and an issue tracker can be found at https://github.com/OlgaHuawei. 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. 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). 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 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 that can be used to configure and manage OSPF. The model is based on YANG 1.1 as defined in RFC 7950 and conforms to the Network Management Datastore Architecture (NMDA) as described in RFC 8342. 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] Informative References Alef Edge Individual Juniper Networks Cisco Systems Inc Ciena Telefonica This document defines a YANG data model for layer 3 traffic engineering topologies. Telefonica Nokia Nokia Cisco Huawei This document defines a YANG data model for representing an abstracted view of a network topology that contains Intermediate System to Intermediate System (IS-IS). This document augments the 'ietf-network' data model by adding IS-IS concepts and explains how the data model can be used to represent the IS-IS topology. The YANG data model defined in this document conforms to the Network Management Datastore Architecture (NMDA).

Acknowledgments This work is partially supported by the European Commission under Horizon 2020 ALLEGRO project.