| Internet-Draft | Digital Map Concept & Needs | October 2024 |
| Havel, et al. | Expires 24 April 2025 | [Page] |
This document defines the concept of Digital Map, and identifies a set of Digital Map requirements and use cases.¶
The document intends to be used as a reference for the assessment effort of the various topology modules to meet Digital Map requirements.¶
This note is to be removed before publishing as an RFC.¶
Discussion of this document takes place on the Network Management Operations Working Group mailing list (nmop@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/nmop/.¶
Source for this draft and an issue tracker can be found at https://github.com/ietf-wg-nmop/draft-ietf-nmop-digital-map-concept.¶
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Digital Map is a data model that provides a view of the operator's networks and services, including how it is connected to other models/data (e.g. inventory, observability sources, and operational knowledge). It specifically provides an approach to model multi-layered topology and appropriate mechanism to navigate amongs layers and correlate between them. This includes layers from physical topology to service topology. This model is applicable to multiple domains (access, core, data centers, etc.) and technologies (Optical, IP, etc.).¶
The Digital Map modelling defines the core topological entities (network, node, link, and interface) at each layer, their role in the network topology, core topological properties, and topological relationships both inside each layer and between the layers. It also defines how to access other external models from the topology.¶
The Digital Map model is a topological model that is linked to the other functional models and connects them all: configuration, maintenance, assurance (KPIs, status, health, and symptoms), Traffic-Engineering (TE), different behaviors and actions, simulation, emulation, mathematical abstractions, AI algorithms, etc. These other models exist outside of the digital map and are not defined during digital map modelling.¶
The Digital Map data consists of virtual instances of network and service topologies at different layers. The Digital Map provides access to this data via standard APIs for both read and write operations (write operations for offline simulations), with query capabilities and links to other YANG modules (e.g., Service Assurance for Intent-based Networking (SAIN) [RFC9417], Service Attachement Points (SAPs) [RFC9408], Inventory [I-D.ietf-ivy-network-inventory-yang], and non-YANG models.¶
The document makes use of the following terms:¶
Topology in this document refers to the network and service topology. Network topology defines how physical or logical nodes, links and interfaces are related and arranged. Service topology defines how service components (e.g., VPN instances, customer interfaces, and customer links) between customer sites are interrelated and arranged. There are at least 8 types of topologies: point to point, bus, ring, star, tree, mesh, hybrid and daisy chain. Topologies may be unidirectional or bidirectional (bus, some rings).¶
A multi-layered topology models relationships between different layers of topology, where each layer represents a connectivity aspect of the network and services that needs to be configured, controlled and monitored. Each layer of topology has a separate lifecycle.¶
Represents topology at a single layer in the multi-layered topology.¶
The topology layer can also represent what needs to be managed by a specific user, for example IGP layer can be of interest to the operator troubleshooting or optimizating the routing, while the optical layer may be of interest to the user managing the optical network.¶
Some topology layers may relate closely to OSI layers, like L1 topology for physical topology, Layer 2 for link topology and Layer 3 for IPv4 and IPv6 topologies.¶
Some topology layers represent the control aspects of Layer 3, like OSPF, IS-IS, or BGP.¶
The service layer represents the service view of the connectivity, that can differ for different types of services and for different providers/solutions.¶
The top layer represents the application/flow view of service connectivity.¶
The document defines the following terms:¶
Digital Map is a data model that provides a view of the operator's networks and services, including how it is connected to other models/data (e.g. inventory, observability sources, and operational knowledge). It specifically provides an approach to model multi-layered topology and appropriate mechanism to navigate amongs layers and correlate between them. This model is applicable to multiple domains (access, core, data centers, etc.) and technologies (Optical, IP, etc.).¶
The set of principles, guidelines, and conventions to model the Digital Map using the IETF [RFC8345] approach. They cover the network types (layers and sublayers), entity types, entity roles (network, node, termination point or link), entity properties, relationship types between entities and relationships to other entities.¶
Defines the core topological entities, their role in the network, core topological properties and relationships both inside each layer and between the layers.¶
It is the basic topological model with the links to other models and connects them all: configuration, maintenance, assurance (KPIs, status, health, symptoms, etc.), traffic engineering, different behaviors, simulation, emulation, mathematical abstractions, AI algorithms, etc.¶
Consists of instances of network and service topologies at different layers. This includes instances of networks, nodes, links and termination points, topological relationships between nodes, links and termination points inside a network, relationships between instances belonging to different networks, links to functional data for the instances, including configuration, health, symptoms.¶
The data can be historical, real-time, or future data for 'what-if' scenarios.¶
The following are sample use cases that require Digital Map:¶
Generic inventory queries¶
Service placement feasibility checks¶
Service-> subservice -> resource¶
Resource -> subservice -> service¶
Intent/service assurance¶
Service E2E and per-link KPIs on the Digital Map (connectivity status, high-availability, delay, jitter, and loss)¶
Capacity planning¶
Network design¶
Simulation¶
Closed loop¶
Digital Twin¶
Overall, the Digital Map is needed to provide the mechanism to connect data islands from the core multi-layered topology. It is a solution feasible and useful in the short-term for the existing operations use cases, but it is also a requirement for the Digital Twin.¶
The following sections shows some example use case descriptions to initiate the discussion what type of info is needed to describe the use cases in the context of Digital Map. The next version of the draft will include more info on these use cases, from the perspective of what is the value of the digital map for each use case and how the Digital Map API can be used. This will also clarify if only read and if/when write interface is needed per use case.¶
The application will be able to retrieve physical topology from the controller via Digital Map API and from the response it will be able to retrieve physical inventory of individual devices and cables.¶
The application may request either one or multiple layers of topology via the Digital Map API and and from the response it will be able to retrieve both physical and logical inventory.¶
The application will be able to retrieve all services from the Digital Map API for selected network type. The application will be able to retrieve the topology for selected services via Digital Map API and from the response it will be able to navigate via the supporting relationship top-down to the lower layers. That way, it will be able to determine what logical resources are used by the service. The supporting relations to the lowest layer will help application to determine what physical resources are used by the service.¶
The application will be able to navigate from the Physical, L2 or L3 topology to the services that use specific resources. For example, the application will be able to select the resouce and by navigation the supporting relationship bottom-up come to the service and its nodes, tps and links.¶
The application will be able to retrieve topology layer and any network/node/tp/link instances from the controller via Digital Map API and from the response it will be able to determine the health of each instance by navigating to the SAIN subservices and its symptoms.¶
The application will be able to retieve the topology at any layer from the controller via Digital Map API and from the response it will be able to navigate any retrieve any KPIs for selected topology entity.¶
The following are the core requirements for the Digital Map (note that some of them are supported by default by [RFC8345]):¶
Basic model with network, node, link, and interface entity types.¶
This means that users of the Digital Map model must be able to understand topology model at any layer via these core concepts only, without having to go to the details of the specific augmentations to understand the topology.¶
Layered Digital Map, from physical network (ideally optical, layer 2, layer 3) up to service and intent views.¶
Open and programmable Digital Map.¶
This includes "read" operations to retrieve the view of the network, typically as application-facing interface of Software Defined Networking (SDN) controllers or orchestrators.¶
It also includes "write" operations, not for the ability to directly change the Digital Map data (e.g., changing the network or service parameters), but for offline simulations, also known as what-if scenarios.¶
Running a "what-if" analysis requires the ability to take snapshots and to switch easily between them.¶
Note that there is a need to distinguish between a change on the Digital Map for future simulation and a change that reflects the current reality of the network.¶
Standard based Digital Map Models and APIs, for multi-vendor support.¶
Digital Map must provide the standard YANG APIs that provide for read/write and queries. These APIs must also provide the capability to retrieve the links to external data/models.¶
Digital Map models and APIs must be common over different network domains (campus, core, data center, etc.).¶
This means that clients of the Digital Map API must be able to understand the topology model of layers of any domain without having to understand the details of any technologies and domains.¶
Digital Map must provide semantics for layered network topologies and for linking external models/data.¶
Digital Map must provide intra-layer and inter-layer relationships.¶
Digital Map must be extensible with metadata.¶
Digital Map must be pluggable. That is,¶
Digital Map must be optimized for graph traversal for paths. This means that only providing link nodes and source and sink relationships to termination-points may not be sufficient, we may need to have the direct relationship between the termination points or nodes.¶
The following are design requirements for modelling the Digital Map. Theey are derived from the core requerements collected from the operators and although there is some duplication, these are focused on summarizing the requirements for the design of the model and API:¶
Digital Map should contain only topological information.¶
Digital Map is not required to contain all models and data required for all the management and use cases. However, it should be designed to support adequate pointers to other functional data and models to ease navigating in the overall system. For example:¶
ACLs and Route Policies are not required to be supported in the Digital Map, they would be linked to Digital Map¶
Dynamic paths may either be outside of the Digital Map or part of traffic engineering data/models¶
Digital Map entities should mainly contain properties used to identify topological entities at different layers, identify their roles, and topological relationships between them.¶
Digital Map should contain all topological relationships inside each layer or between the layers (underlay/overlay)¶
Digital Map should contain links to other models/data to enable generic navigation to other YANG models in generic way.¶
Provide capability for conditional retrieval of parts of Digital Map.¶
Must support geo-spatial, temporal, and historical data. The temporal and historical can also be supported external to the Digital Map.¶
The following are the architectural requirements for the controller that provides Digital Map API:¶
As this document covers the Digital Map concepts, requirements, and use cases, there is no specific security considerations. However, the RFC 8345 Security Considerations aspects will be useful when designing the solution.¶
This document has no actions for IANA.¶
Many thanks to Mohamed Boucadair (mohamed.boucadair@orange.com) for his valuable contributions, reviews, and comments.¶
Many thanks to Nigel Davis ndavis@ciena.com for the valuable discussions and his confirmation of the modelling requirements.¶