]> SIMAP: Concept, Requirements, and Use Cases Huawei
olga.havel@huawei.com
Huawei
benoit.claise@huawei.com
Telefonica
oscar.gonzalezdedios@telefonica.com
Swisscom
thomas.graf@swisscom.com
Operations and Management Network Management Operations Service & Infrastructure Maps Service emulation Automation Network Automation Orchestration service delivery Service provisioning service flexibility service simplification Network Service Digital Map Emulation Simulation Topology Multi-layer This document defines the concept of Service & Infrastructure Maps (SIMAP) and identifies a set of SIMAP requirements and use cases. The SIMAP was previously known as Digital Map in the old draft versions (draft-ietf-nmop-digital-map-concept). The document intends to be used as a reference for the assessment effort of the various topology modules to meet SIMAP requirements. Discussion Venues Discussion of this document takes place on the Network Management Operations Working Group mailing list (nmop@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .
Introduction Service & Infrastructure Maps (SIMAP) 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 SIMAP 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 SIMAP 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 SIMAP and are not defined during SIMAP modelling. The SIMAP data consists of virtual instances of network and service topologies at different layers. The SIMAP 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) , Service Attachement Points (SAPs) , Inventory , and non-YANG models.
Terminology The document makes use of the following terms:
Topology:
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).
Multi-layered topology:
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.
Topology layer:
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 optimizing 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:
Service & Infrastructure Maps (SIMAP):
SIMAP 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.).
SIMAP modelling:
The set of principles, guidelines, and conventions to model the Service & Infrastructure Maps (SIMAP) using the IETF 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.
SIMAP model:
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.
SIMAP data:
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.
Sample SIMAP Use Cases The following are sample use cases that require SIMAP:
  • Generic inventory queries
  • Service placement feasibility checks
  • Service-> subservice -> resource
  • Resource -> subservice -> service
  • Intent/service assurance
  • Service E2E and per-link KPIs on SIMAP (connectivity status, high-availability, delay, jitter, and loss)
  • Capacity planning
  • Network design
  • Simulation
  • Closed loop
  • Digital Twin
Overall, the SIMAP 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 SIMAP. The following sections includes some initial use case descriptions to initiate the discussion about what type of info is needed to describe the use cases in the context of SIMAP. The next version of the draft will include more info on these use cases and more input from the operators, from the perspective of what the value of the SIMAP for each use case is and how the SIMAP API can be used. This will also clarify if only read and if/when write interface is needed per use case.
Generic inventory queries The application will be able to retrieve physical topology from the controller via SIMAP 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 SIMAP API and and from the response it will be able to retrieve both physical and logical inventory. For Access network providers the ability to have linkage in the SIMAP of the complete network (active + passive) is essential as it provides many advantages for optimized customer service, reduced MTTR, and lower operational costs through truck roll reduction.
Service placement feasibility checks
Service-> subservice -> resource The application will be able to retrieve all services from the SIMAP API for selected network types. The application will be able to retrieve the topology for selected services via SIMAP 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.
Resource -> subservice -> 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 navigating the supporting relationship bottom-up come to the service and its nodes, tps and links.
Intent/service assurance The application will be able to retrieve topology layer and any network/node/tp/link instances from the controller via the SIMAP 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.
Service E2E and per-link KPIs The application will be able to retieve the topology at any layer from the controller via the SIMAP API and from the response it will be able to navigate any retrieve any KPIs for selected topology entity.
Capacity planning
Network design
Simulation
Closed Loop
Digital Twin
SIMAP Requirements
Core Requirements The following are the core requirements for the SIMAP (note that some of them are supported by default by ):
REQ-BASIC-MODEL-SUPPORT:
Basic model with network, node, link, and interface entity types.
This means that users of the SIMAP 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.
REQ-LAYERED-MODEL:
Layered SIMAP, from physical network (ideally optical, layer 2, layer 3) up to service and intent views.
REQ-PASSIVE-TOPO:
SIMAP must support topology of the complete network, including active and passive parts.
For Access network providers the ability to have linkage in the SIMAP of the complete network (active + passive) is essential as it provides many advantages for optimized customer service, reduced MTTR, and lower operational costs through truck roll reduction.
REQ-PROG-OPEN-MODEL:
Open and programmable SIMAP.
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 SIMAP 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 SIMAP for future simulation and a change that reflects the current reality of the network.
REQ-STD-API-BASED:
Standard based SIMAP Models and APIs, for multi-vendor support.
SIMAP 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.
REQ-COMMON-APP:
SIMAP models and APIs must be common over different network domains (campus, core, data center, etc.).
This means that clients of the SIMAP 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.
REQ-SEMANTIC:
SIMAP must provide semantics for layered network topologies and for linking external models/data.
REQ-LAYER-NAVIGATE:
SIMAP must provide intra-layer and inter-layer relationships.
REQ-EXTENSIBLE:
SIMAP must be extensible with metadata.
REQ-PLUGG:
SIMAP must be pluggable. That is,
  • Must connect to other YANG modules for inventory, configuration, assurance, etc.
  • Given that no all involved components can be available using YANG, there is a need to connect SIMAP YANG model with other modelling mechanisms.
REQ-GRAPH-TRAVERSAL:
SIMAP 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.
Design Requirements The following are design requirements for modelling the SIMAP. 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:
REQ-TOPO-ONLY:
SIMAP should contain only topological information.
SIMAP 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 SIMAP, they would be linked to the SIMAP
  • Dynamic paths may either be outside of the SIMAP or part of traffic engineering data/models
REQ-PROPERTIES:
SIMAP entities should mainly contain properties used to identify topological entities at different layers, identify their roles, and topological relationships between them.
REQ-RELATIONSHIPS:
SIMAP should contain all topological relationships inside each layer or between the layers (underlay/overlay)
SIMAP should contain links to other models/data to enable generic navigation to other YANG models in generic way.
REQ-CONDITIONAL:
Provide capability for conditional retrieval of parts of SIMAP.
REQ-TEMPO-HISTO:
Must support geo-spatial, temporal, and historical data. The temporal and historical can also be supported external to the SIMAP.
Architectural Requirements The following are the architectural requirements for the controller that provides SIMAP API:
REQ-DM-SCALES:
Scale, performance, ease of integration.
REQ-DM-DISCOVERY:
Initial discovery and dynamic (change only) synch with the physical network.
Security Considerations As this document covers the SIMAP 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.
IANA Considerations This document has no actions for IANA.
References Normative References A YANG Data Model for Network Topologies 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. Informative References Service Assurance for Intent-Based Networking Architecture This document describes an architecture that provides some assurance that service instances are running as expected. As services rely upon multiple subservices provided by a variety of elements, including the underlying network devices and functions, getting the assurance of a healthy service is only possible with a holistic view of all involved elements. This architecture not only helps to correlate the service degradation with symptoms of a specific network component but, it also lists the services impacted by the failure or degradation of a specific network component. A YANG Network Data Model for Service Attachment Points (SAPs) 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. A Base YANG Data Model for Network Inventory Huawei Technologies Nokia Vodafone TIM Cisco This document defines a base YANG data model for network inventory. The scope of this base model is set to be application- and technology-agnostic. However, the data model is designed with appropriate provisions to ease future augmentations with application- specific and technology-specific details. Overview and Principles of Internet Traffic Engineering This document describes the principles of traffic engineering (TE) in the Internet. The document is intended to promote better understanding of the issues surrounding traffic engineering in IP networks and the networks that support IP networking and to provide a common basis for the development of traffic-engineering capabilities for the Internet. The principles, architectures, and methodologies for performance evaluation and performance optimization of operational networks are also discussed. This work was first published as RFC 3272 in May 2002. This document obsoletes RFC 3272 by making a complete update to bring the text in line with best current practices for Internet traffic engineering and to include references to the latest relevant work in the IETF. A YANG Grouping for Geographic Locations This document defines a generic geographical location YANG grouping. The geographical location grouping is intended to be used in YANG data models for specifying a location on or in reference to Earth or any other astronomical object. YANG Data Model for Traffic Engineering (TE) 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. A YANG Data Model for Layer 2 Network Topologies This document defines a YANG data model for Layer 2 network topologies. In particular, this data model augments the generic network and network topology data models with topology attributes that are specific to Layer 2. A YANG Data Model for Open Shortest Path First (OSPF) Topology Telefonica Nokia Nokia 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). A YANG Data Model for Intermediate System to intermediate System (IS-IS) Topology 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). A YANG Data Model for Service Assurance This document specifies YANG modules for representing assurance graphs. These graphs represent the assurance of a given service by decomposing it into atomic assurance elements called subservices. The companion document, "Service Assurance for Intent-Based Networking Architecture" (RFC 9417), presents an architecture for implementing the assurance of such services. The YANG data models in this document conform to the Network Management Datastore Architecture (NMDA) defined in RFC 8342. A YANG Data Model for Network Hardware Inventory Huawei Technologies Nokia Vodafone TIM Cisco This document defines a YANG data model for network hardware inventory data information. The YANG data model presented in this document is intended to be used as the basis toward a generic YANG data model for network hardware inventory data information which can be augmented, when required, with technology-specific (e.g., optical) inventory data, to be defined either in a future version of this document or in another document. The YANG data model defined in this document conforms to the Network Management Datastore Architecture (NMDA). A YANG Network Data Model of Network Inventory Huawei China Mobile Huawei Orange This document defines a base YANG data model for network inventory that is application- and technology-agnostic. This data model can be augmented with application-specific and technology-specific details in other, more specific network inventory data models. This document is meant to help IVY base Network Inventory model discussion and ease agreement on a base model that would be flexible enough to be augmented with components that are covered by the IVY Charter. The hardware components definition are adapted from draft-ietf-ccamp- network-inventory-yang-02. A Network Inventory Topology Model Huawei China Mobile Huawei Orange This document defines a YANG model for network inventory topology to correlate the network inventory data with the general topology model to form a base underlay network, which can facilitate the mapping and correlation of the layer (e.g. Layer 2, Layer3) topology information above to the inventory data of the underlay network for agile service provisioning and network maintenance analysis. A Network YANG Data Model for Attachment Circuits Orange Juniper Telefonica Nokia Huawei Technologies This document specifies a network model for attachment circuits. The model can be used for the provisioning of attachment circuits prior or during service provisioning (e.g., VPN, Network Slice Service). A companion service model is specified in the YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service (ACaaS) (I-D.ietf- opsawg-teas-attachment-circuit). The module augments the base network ('ietf-network') and the Service Attachment Point (SAP) models with the detailed information for the provisioning of attachment circuits in Provider Edges (PEs). YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service (ACaaS) Orange Juniper Telefonica Nokia Huawei Technologies This document specifies a YANG service data model for Attachment Circuits (ACs). This model can be used for the provisioning of ACs before or during service provisioning (e.g., Network Slice Service). The document also specifies a service model for managing bearers over which ACs are established. A YANG Data Model for Layer 2 Virtual Private Network (L2VPN) Service Delivery This document defines a YANG data model that can be used to configure a Layer 2 provider-provisioned VPN service. It is up to a management system to take this as an input and generate specific configuration models to configure the different network elements to deliver the service. How this configuration of network elements is done is out of scope for this document. The YANG data model defined in this document includes support for point-to-point Virtual Private Wire Services (VPWSs) and multipoint Virtual Private LAN Services (VPLSs) that use Pseudowires signaled using the Label Distribution Protocol (LDP) and the Border Gateway Protocol (BGP) as described in RFCs 4761 and 6624. The YANG data model defined in this document conforms to the Network Management Datastore Architecture defined in RFC 8342. YANG Data Model for L3VPN Service Delivery This document defines a YANG data model that can be used for communication between customers and network operators and to deliver a Layer 3 provider-provisioned VPN service. This document is limited to BGP PE-based VPNs as described in RFCs 4026, 4110, and 4364. This model is intended to be instantiated at the management system to deliver the overall service. It is not a configuration model to be used directly on network elements. This model provides an abstracted view of the Layer 3 IP VPN service configuration components. It will be up to the management system to take this model as input and use specific configuration models to configure the different network elements to deliver the service. How the configuration of network elements is done is out of scope for this document. This document obsoletes RFC 8049; it replaces the unimplementable module in that RFC with a new module with the same name that is not backward compatible. The changes are a series of small fixes to the YANG module and some clarifications to the text. A YANG Network Data Model for Layer 2 VPNs This document defines an L2VPN Network Model (L2NM) that can be used to manage the provisioning of Layer 2 Virtual Private Network (L2VPN) services within a network (e.g., a service provider network). The L2NM complements the L2VPN Service Model (L2SM) by providing a network-centric view of the service that is internal to a service provider. The L2NM is particularly meant to be used by a network controller to derive the configuration information that will be sent to relevant network devices. Also, this document defines a YANG module to manage Ethernet segments and the initial versions of two IANA-maintained modules that include a set of identities of BGP Layer 2 encapsulation types and pseudowire types. A YANG Network Data Model for Layer 3 VPNs As a complement to the Layer 3 Virtual Private Network Service Model (L3SM), which is used for communication between customers and service providers, this document defines an L3VPN Network Model (L3NM) that can be used for the provisioning of Layer 3 Virtual Private Network (L3VPN) services within a service provider network. The model provides a network-centric view of L3VPN services. The L3NM is meant to be used by a network controller to derive the configuration information that will be sent to relevant network devices. The model can also facilitate communication between a service orchestrator and a network controller/orchestrator. A YANG Data Model for Network Incident Management CMCC Huawei Ciena A network incident refers to an unexpected interruption of a network service, degradation of a network service quality, or sub-health of a network service. Different data sources including alarms, metrics, and other anomaly information can be aggregated into a few amount of network incidents through data correlation analysis and the service impact analysis. This document defines a YANG Module for the network incident lifecycle management. This YANG module is meant to provide a standard way to report, diagnose, and help resolve network incidents for the sake of network service health and root cause analysis.
Related IETF Activities
Network Topology Interestingly, we could not find any network topology definition in IETF RFCs (not even in ) or Internet-Drafts. However, it is mentioned in multiple documents. As an example, in Overview and Principles of Internet Traffic Engineering , which mentions:
To conduct performance studies and to support planning of existing and future networks, a routing analysis may be performed to determine the paths the routing protocols will choose for various traffic demands, and to ascertain the utilization of network resources as traffic is routed through the network. Routing analysis captures the selection of paths through the network, the assignment of traffic across multiple feasible routes, and the multiplexing of IP traffic over traffic trunks (if such constructs exist) and over the underlying network infrastructure. A model of network topology is necessary to perform routing analysis. A network topology model may be extracted from:
  • Network architecture documents
  • Network designs
  • Information contained in router configuration files
  • Routing databases such as the link state database of an interior gateway protocol (IGP)
  • Routing tables
  • Automated tools that discover and collate network topology information.
Topology information may also be derived from servers that monitor network state, and from servers that perform provisioning functions.
Core SIMAP Components The following specifications are core for the SIMAP:
  • IETF network model and network topology model
  • A YANG grouping for geographic location
  • IETF modules that augment for different technologies:
    • A YANG data model for Traffic Engineering (TE) Topologies
    • A YANG data model for Layer 2 network topologies
    • A YANG data model for OSFP topology
    • A YANG data model for IS-IS topology
Additional SIMAP Components The SIMAP may need to link to the following models, some are already augmenting :
  • Service Attachment Point (SAP) , augments 'ietf-network' data model by adding the SAP.
  • SAIN
  • Network Inventory Model focuses on physical and virtual inventory. Logical inventory is currently outside of the scope. It does not augment RFC8345 like the two Internet-Drafts that it evolved from and . correlates the network inventory with the general topology via RFC8345 augmentations that reference inventory.
  • KPIs: delay, jitter, loss
  • Attachment Circuits (ACs) and
  • Configuration: L2SM , L3SM , L2NM , and L3NM
  • Incident Management for Network Services
Acknowledgments Many thanks to Mohamed Boucadair for his valuable contributions, reviews, and comments. Many thanks to Adrian Farrel for his SIMAP suggestion and helping to agree the terminology. Many thanks to Dan Voyer, Brad Peters, Diego Lopez, Ignacio Dominguez Martinez-Casanueva, Italo Busi, Wu Bo, Sherif Mostafa, Christopher Janz, Rob Evans, Danielle Ceccarelli, and many others for their contributions, suggestions and comments. Many thanks to Nigel Davis ndavis@ciena.com for the valuable discussions and his confirmation of the modelling requirements.
Contributors Swisscom
Ahmed.Elhassany@swisscom.com