SIMAP: Concept, Requirements, and Use Cases
draft-ietf-nmop-simap-concept-09
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
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|---|---|---|---|
| Authors | Olga Havel , Benoît Claise , Oscar Gonzalez de Dios , Thomas Graf | ||
| Last updated | 2026-03-18 (Latest revision 2026-02-23) | ||
| Replaces | draft-ietf-nmop-digital-map-concept | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Consensus: Waiting for Write-Up | |
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| Document shepherd | Reshad Rahman | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | mohamed.boucadair@orange.com, reshad@yahoo.com |
draft-ietf-nmop-simap-concept-09
Network Management Operations O. Havel
Internet-Draft Huawei
Intended status: Informational B. Claise
Expires: 19 September 2026 Everything OPS
O. G. D. Dios
Telefonica
T. Graf
Swisscom
18 March 2026
SIMAP: Concept, Requirements, and Use Cases
draft-ietf-nmop-simap-concept-09
Abstract
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. SIMAP evolves the
earlier ‘Digital Map’ concept by making explicit the ties between
service and infrastructure layers, clarifying expected outcomes for
operations and automation, and addressing ambiguity associated with
the term ‘digital.’
The document intends to be used as a reference for the assessment of
the various topology modules to meet SIMAP requirements.
Discussion Venues
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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 19 September 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Sample SIMAP Use Cases . . . . . . . . . . . . . . . . . . . 9
3.1. Common Enablers for SIMAP . . . . . . . . . . . . . . . . 9
3.1.1. Service -> Resource . . . . . . . . . . . . . . . . . 9
3.1.2. Resource -> Service . . . . . . . . . . . . . . . . . 9
3.1.3. Traffic Engineering (TE) . . . . . . . . . . . . . . 10
3.1.4. Closed Loop . . . . . . . . . . . . . . . . . . . . . 10
3.2. Inventory Queries . . . . . . . . . . . . . . . . . . . . 11
3.3. Service Placement Feasibility Checks . . . . . . . . . . 12
3.4. Intent/Service Assurance . . . . . . . . . . . . . . . . 13
3.5. Service E2E and Per-link KPIs . . . . . . . . . . . . . . 14
3.6. Network Capacity Planning . . . . . . . . . . . . . . . . 14
3.7. Network Design . . . . . . . . . . . . . . . . . . . . . 15
3.8. Network Simulation and Network Emulation . . . . . . . . 16
3.8.1. Types of Network Simulation . . . . . . . . . . . . . 17
3.8.2. Goals of Network Simulation . . . . . . . . . . . . . 17
3.9. Postmortem Replay . . . . . . . . . . . . . . . . . . . . 18
3.10. Network Digital Twin (NDT) . . . . . . . . . . . . . . . 19
4. SIMAP Operator Requirements . . . . . . . . . . . . . . . . . 20
4.1. Functional Requirements . . . . . . . . . . . . . . . . . 20
4.2. Design Requirements . . . . . . . . . . . . . . . . . . . 27
4.3. Architectural Requirements . . . . . . . . . . . . . . . 28
5. Positioning SIMAP in the Context of the IETF Work . . . . . . 29
6. Security Considerations . . . . . . . . . . . . . . . . . . . 31
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7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.1. Normative References . . . . . . . . . . . . . . . . . . 31
8.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Related IETF Activities . . . . . . . . . . . . . . 36
A.1. Network Topology . . . . . . . . . . . . . . . . . . . . 36
A.2. Topology Abstraction . . . . . . . . . . . . . . . . . . 37
A.3. Core SIMAP Components . . . . . . . . . . . . . . . . . . 37
A.4. Additional SIMAP Components . . . . . . . . . . . . . . . 38
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 38
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
1. Introduction
This document defines the concept of Service & Infrastructure Maps
(SIMAP) and outlines associated requirements and use cases.
SIMAP is a data model that provides a topological view of the
operator's networks and services, including how it is connected to
other models (e.g., inventory) and external data sources (e.g.,
observability data, and operational knowledge). This model
represents a multi-layered topology and offers mechanisms to navigate
amongst layers and correlate between them. This includes layers from
physical topology to service topology. This model is applicable to
multiple domains (access, core, data center, etc.) and technologies
(Optical, IP, etc.).
Specifically, the SIMAP modelling defines the core topological
entities at each layer, core topological properties, and topological
relationships (both inside each layer and between the layers), to
ensure a multi-layered topology can be reconstructed, validated and
queried in an unambiguous and interoperable manner. The core
topological entities are the minimal set of objects required to
represent a layer's topology (e.g., network, node, termination point,
and link). The core topological properties are the essential
attributes associated with these entities (e.g., identity, topology
type, entity role in topology, directionality, cardinality, and cost/
weight), enabling analysis of how the network structure affects
services and operations. For example, topological reasoning can
answer questions such as: 'If link X fails, what services are
impacted?' or 'What is the full end-to-end data path of the service
flow?'.
The additional concepts or attributes (such as capacity, operational
state, performance metrics, or inventory data) are modelled outside
of SIMAP, the core set provides the necessary structure to support
these extensions without losing architectural consistency.
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The SIMAP modelling also defines how to access other external models
from a topology. SIMAP is a topological model that is linked to
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 instances of network and service
topologies at different layers. There may be a separate topology
instance for each layer in a multi-layered network, or a single
topology instance that encompasses multiple layers. Since SIMAP is a
data model and data models can generate APIs [RFC3444][RFC7950], the
SIMAP provides access to this data via standard APIs for both read
and write access, typically from a controller, with query
capabilities and links to other data models (e.g., Service Assurance
for Intent-based Networking (SAIN) [RFC9417], Service Attachment
Points (SAPs) [RFC9408], Inventory
[I-D.ietf-ivy-network-inventory-yang], and potentially linking to
non-YANG models).
The SIMAP also provides write operations with the same set of APIs,
not to change a topology layer on the fly as a northbound interface
from the controller, but for both online and offline simulations,
before applying the changes to the network via the normal controller
operations.
Both real network, online simulation, and offline simulation APIs can
be built on the same data model. The real network API reflects
actual changes in the topology as reported by the SIMAP server.
Online simulation applies hypothetical changes to the current live
model to assess immediate impacts (e.g., if link X fails, what
services are disrupted), without altering the real network. Offline
simulation applies hypothetical changes to a saved or alternate
model, useful for planning, training, or evaluating changes before
deployment. Each data source is reported as a distinct topology
instance, but when desired the real network and online simulation
data can be merged into a single topology instance, while the offline
simulation remains separate. The simulated topology instance can be
matched directly to the corresponding real network topology for
comparison. This approach preserves independence between real and
simulated data while enabling side by side analysis.
This document does not specify a SIMAP implementation approach and
what modelling language to use. Also, how implementations are
connected to SIMAP is implementation- and deployment- specific.
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While the requirements described herein may require various modeling
strategies, the development of such models is outside the scope of
this document.
2. Terminology
This document makes use of the following terms:
Topology: Topology refers to the network and service topology. A
network topology defines how physical or logical nodes, links and
termination points are related and arranged. A Service topology
defines how service components (e.g., VPN instances, customer
interfaces, and customer links) between customer sites are
interrelated and arranged.
There are several types of topologies: point-to-point, bus, ring,
star, tree, mesh, hybrid, and daisy chain.
Topologies may be unidirectional (all links unidirectional) or
bidirectional (all links bidirectional), or contain combination of
unidirectional and bidirectional links.
Multi-layered topology: A multi-layered topology models
relationships between different topology layers, where each layer
represents a connectivity aspect of the network and services that
needs to be configured, controlled and monitored. Each topology
layer has a separate lifecycle.
[RFC8345] also refers to this multi-layered topology as topology
hierarchy (stack). It also uses layers when describing supporting
relations (represent layered network topologies), underlay/
overlay, network nodes and layering information. [RFC8345] states
that the model can be used for representation of layered network
topologies.
[RFC8345] is flexible and can support both the same network
topology instance with multiple layers (e.g., Layer 2 and Layer 3)
or separate network topology instances with supporting relations
between them (e.g., separate Layer 2 and Layer 3). Therefore,
multiple topology layers can be grouped into the same network
topology instance, if solution requires.
Topology layer: A 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
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a specific user or client application, for example the 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 Layer
1 topology for physical topology, Layer 2 for link topology and
Layer 3 for IPv4 and IPv6 topologies.
Some topology layers represent the network topology of Layer 3
control protocols, 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 application/flow layer represents the view of Service data
flows for different classes of service - video, voice and data
traffic. The layers may differ depending on the solution, so the
bottom and top layers may not be the same across all solutions.
We can illustrate the concept of topology layers by listing the
common set — e.g.,
* physical: L1, one or multiple layers, if fully modelling
different optical layers. Used for WSON, OTN optical, OTN
digital),
* data link: L2 for Ethernet, LAGs and VLAN,
* network: L3 for IPv4 and IPv6,
* IGP/EGP: for routing inside or between ASs, different layers
for underlay and overlay, for ISIS, OSPF, iBGP. eBGP,
* tunnel: for transport tunnels and paths, for MPLS and SRv6,
* service: for different overlay services, like L2 VPNs, L3 VPNs,
slices, SD-WAN,
* application: for video, voice and data traffic flows.
However, this list is illustrative only; it is not a prescriptive
requirement. Different solutions may adopt alternative layering
schemes or combine layers differently. Therefore, we will present
the above as an example of one possible solution, while keeping
the definition flexible enough to accommodate flexible layering.
Service: A service represents network connectivity service provided
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over a network that enables devices, systems, or networks to
communicate and exchange data with each other. It provides the
underlying infrastructure and mechanisms necessary for
establishing, maintaining, and managing connections between
different endpoints. The example services are: L2VPN, L3VPN,
EVPN, VPLS, VPWS,
Resource: Defined in [I-D.ietf-nmop-terminology]
Termination Point: Defined in [RFC8345], as follows:
The network-topology module defines a topology graph and
components from which it is composed: nodes, edges, and
termination points. Nodes (from the "ietf-network" module)
represent graph vertices and links represent graph edges. Nodes
also contain termination points that anchor the links.
A node has a list of termination points that are used to terminate
links. An example of a termination point might be a physical or
logical port or, more generally, an interface. Like a node, a
termination point can in turn be supported by an underlying
termination point, contained in the supporting node of the
underlay network.
The document defines the following terms:
Service & Infrastructure Maps (SIMAP): SIMAP is a data model that
provides a topological view of the operator's networks and
services, including how it is connected to other models (e.g.,
inventory) and external data sources (e.g., observability data,
and operational knowledge). It specifically provides an approach
to model multi-layered topology and an appropriate mechanism to
navigate amongst 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.)
Therefore, SIMAP 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 a basic
topological model with references/pointers 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 modelling: SIMAP modelling is the set of principles,
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guidelines, and conventions to model the SIMAP. 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 data: 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 other non-topological data for the instances
(e.g., inventory, configuration, health, symptoms).
The SIMAP data can be historical, real-time, or future data for
'what-if' scenarios.
SIMAP API: SIMAP API is the set of interfaces that allow the client
applications to create, read, update, and delete data that
comforms to the SIMAP.
SIMAP client application: Consumer of the SIMAP API. An application
that consumes the SIMAP API. It sends requests to a SIMAP server,
receives responses, and uses the returned data to drive its own
logic. Typical clients include network management systems,
orchestration tools, monitoring dashboards, capacity management
applications, or any software that needs to read or modify the
topology information defined by the SIMAP. The client is
responsible for forming valid API calls, handling authentication/
authorization, parsing responses, and translating the SIMAP into
its own internal representation.
SIMAP server: Provider of the SIMAP API. An application or a system
that implements the API endpoints to expose the SIMAP data model
to external consumers, building it from live network state or
simulation scenarios. The server accepts requests to create,
read, update, delete, or query instances of the SIMAP topology,
validates input against the data model schema, persists changes
(if any), and returns responses that conform to the SIMAP API
specification. The server’s implementation may reside inside a
controller, orchestrator, device, service manager, or any other
application/system—or be a standalone application/system—depending
on the solution architecture. The server may offer ancillary
services such as authentication, rate limiting, versioning,
logging, and monitoring, but its primary role is to expose the
SIMAP via programmable interface.
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3. Sample SIMAP Use Cases
The following subsections provide a non-exhaustive list of SIMAP use
cases, with a focus on the related SIMAP client application
requirements and its interactions with SIMAP server, in order to
extract the SIMAP-related requirements (Section 4).
3.1. Common Enablers for SIMAP
This section identifies a set of enablers that are invoked when
providing the various business-oriented SIMAP use cases. These
enablers are grouped here to avoid duplication.
3.1.1. Service -> Resource
The SIMAP APIs can be invoked to retrieve all Services for selected
service types. A SIMAP client application that triggers such a
request will be able to retrieve the topology for selected Services
via the SIMAP APIs and, from the response, it will be able to
navigate top-down to the lower layers via the supporting relationship
provided by the SIMAP server. In doing so, the SIMAP client
application will be able to determine what logical resources are used
by a Service. The supporting relations to the lowest layer, provided
by the SIMAP server, will help the SIMAP client application to
determine what physical resources are used by the Service. This
addresses a requirement for systems to be able to provide topology
and resource views of services, at different levels of abstraction,
using the SIMAP [REF: ETSI ZSM 019 Clause 6]. Knowing the physical
resources a service uses enables capacity planning, fault isolation,
performance monitoring, and accurate billing.
3.1.2. Resource -> Service
A SIMAP client application can navigate from the physical, Layer 2,
or Layer 3 topology to the Services that rely upon specific
resources. For example, the application will be able to select the
resources and by navigating the supporting relationship bottom-up
come to the Service and its nodes, termination points and links.
This APIs can be invoked for Service impact analysis, for example.
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3.1.3. Traffic Engineering (TE)
Traffic Engineering (TE) [RFC9522] is a network optimization
technique designed to enhance network performance and resource
utilization by intelligently controlling the flow of data, for
example by enabling dynamic path selection based on constraints such
as bandwidth availability, latency, and link costs. Its primary
goals are to prevent network congestion, balance traffic loads, and
ensure efficient use of bandwidth while meeting performance
requirements.
The use cases for capacity planning, simulation, network simulation
and network emulation, closed loop, and potentially others, should
consider TE if configured in the network.
3.1.4. Closed Loop
A network closed loop refers to an automated and intelligent system
where network operations are continuously monitored, analyzed, and
optimized in real time through feedback mechanisms. This self-
adjusting cycle ensures that the network dynamically adapts to
changes, resolves issues proactively, and maintains optimal
performance without manual intervention.
Key Characteristics of a network closed loop:
* Real-time monitoring: Collects data from network devices, traffic
flows, and applications to build a comprehensive view of network
health and performance.
* Automated analysis: Identify anomalies, predict potential
failures, or detect security threats, for example leveraging AI
and machine learning.
* Proactive action: Automatically triggers corrective measures, such
as reconfiguring devices, isolating compromised endpoints, or
rerouting traffic.
* Continuous optimization: Uses feedback from previous cycles to
refine network policies and improve future responses.
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The SIMAP client application will be able to retrieve a topology
layer and any network/node/termination point/link instances from the
SIMAP server via the SIMAP APIs and from the response it will be able
to map the traffic analysis to the entities (typically links and
router) for automated analysis. The corrective measures would be
applied, either directly to the network by managing the SIMAP
entities (network/node/termination point/link instances) or by first
validating the corrective measure in an offline simulation (see the
simulation and traffic engineering use cases).
3.2. Inventory Queries
A network inventory refers to a comprehensive record or database that
tracks and documents all the network components and devices within an
organization's IT infrastructure.
Key elements typically found in a network inventory include:
* Hardware details: Descriptions of physical devices such as
routers (including their internal components such as cards,
power supply units, pluggables), switches, servers, network
cables, including model numbers, serial numbers, and
manufacturer information. This information will facilitate
locating additional details of the hardware in the manufacturer
systems and the correlation with the purchase catalog of the
company.
* Software and firmware: Versions of operating systems, network
management tools, and firmware running on network devices.
Note that a network device can have components with their own
software and firmware.
* Licensing information: For any licensed software or devices, the
network inventory will track license numbers, expiry dates, and
compliance.
A network inventory lifecycle refers to the stages a network device
or component goes through from its introduction to the network until
its removal or replacement. It encompasses everything from
acquisition and deployment to maintenance, upgrade, and eventually
decommissioning. Managing the network inventory lifecycle
efficiently is crucial for maintaining a secure, functional, and
cost-effective network.
A well-maintained network inventory helps organizations with network
management, troubleshooting, asset tracking, security, and ensuring
compliance with regulations. It also helps in scaling the network,
planning upgrades, and responding to issues quickly. In order to
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facilitate the planning and troubleshooting processes it is necessary
to be able to navigate from network inventory to network topology and
Services.
The SIMAP client application will be able to retrieve physical
topology from the SIMAP server via the SIMAP APIs and from the
response it will be able to retrieve the physical inventory of
individual devices and cables and the customer information, if
applicable.
The SIMAP client application may request either one or multiple
topology layers via the SIMAP APIs and from the response it will be
able to navigate to any other data modes outside of the core SIMAP
topology 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 Mean
Time To Repair (MTTR), and lower operational costs through truck roll
reduction. For example, operators may use custom-tags that are
readily available for a customer-facing device, then query the
inventory based on that tag to correlate it with the inventory and
then map it to the network/service topology. The mapping and
correlation can then be used for triggering appropriate Service
checks.
The IVY working group is a good source of information for inventory
information.
3.3. Service Placement Feasibility Checks
Service placement feasibility checks refer to the process of
evaluating whether a specific Service can be deployed and operated
effectively in a given network. This includes accessing the various
factors to ensure that the service will function as intended (e.g.,
based on traffic performance requirements) without causing network
disruptions or inefficiencies and effecting other Services already
provisioned on the network.
Some of the factors that need assesing are network capabilities,
status, limitations, resource usage and availability. The Service
could be simulated during the feasibility checks to identify if there
are any potential issues. The load testing could be done to evaluate
performance under stress.
The service placement feasibility check application will be able to
retrieve the topology at any layer from the SIMAP server via the
SIMAP APIs and from the response it will be able to navigate to any
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other data models outside of the core SIMAP topology to retrieve any
other information needed, such as resource usage, availability,
status, etc.
3.4. Intent/Service Assurance
Network intent and Service assurance work together to ensure that the
network aligns with business goals and that the Services provided
meet the agreed-upon Service Level Agreements (SLAs).
The Service Assurance for Intent-Based Networking Architecture (SAIN)
[RFC9417] approach emphasizes a comprehensive view of components
involved in Service delivery, including network devices and
functions, to effectively monitor and maintain Service health.
The key objectives of this architecture include:
* Holistic service monitoring: By considering all elements involved
in Service delivery, the architecture enables a thorough
assessment of service health.
* Correlation of Service degradation: It assists in linking Service
performance issues to specific network components, facilitating
precise identification of faults.
* Impact assessment: The architecture identifies which Services are
affected by the failure or degradation of particular network
components, aiding in prioritizing remediation efforts.
When a Service is degraded, the SAIN architecture will highlight
where to look in the assurance Service graph, as opposed to going hop
by hop to troubleshoot the issue. More precisely, the SAIN
architecture will associate a list of symptoms originating from
specific SAIN subservices to each Service instance, corresponding to
components of the network. These components are good candidates for
explaining the source of a Service degradation.
The SIMAP client application will be able to retrieve a topology
layer and any network/node/termination point/link instances from the
SIMAP server via the SIMAP APIs and from the response it will be able
to determine the health of each instance by navigating to the SAIN
subservices and its symptoms.
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3.5. Service E2E and Per-link KPIs
The SIMAP client application will be able to retrieve a topology at
any layer from a SIMAP server via the SIMAP APIs and from the
response it will be able to navigate to and retrieve any KPIs for
selected topology entity.
3.6. Network Capacity Planning
Network capacity planning refers to the process of analyzing,
predicting, and ensuring that the network has sufficient capacity
(e.g., [RFC5136]), resources, and infrastructure to meet current and
future demands. It involves evaluating the network's ability to
handle increasing (including forecasted) amounts of data, traffic,
and users' activity, while maintaining acceptable levels of
performance, reliability, and security.
The capacity planning primary goal is to ensure that a network can
support business operations, applications, and services without
interruptions, delays, or degradation in quality. This requires a
thorough understanding of the network's current state, as well as
future requirements and growth projections.
Key aspects of network capacity planning include:
* Traffic analysis: Monitoring and analyzing network traffic
patterns to identify trends, peak usage periods, and areas of
congestion. For example, by generating a core traffic matrix with
IPFIX flow record [RFC7011] or deducting an approximate traffic
matrix from the link utilization data.
* Resource utilization: Evaluating the link utilization throughout
the network for the current demand to identify bottlenecks and
potential QoS performance issues.
* Growth forecasting: Predicting future network growth based on
business expansion, new applications, or changes in users'
behavior.
* What-if scenarios: Creating models to assess the network behavior
under different scenarios, such as increased traffic, failure
conditions (link, router or Shared Risk Resource Group), and new
application deployments (such as a new Content Delivery Network
source, a new peering point, a new data center...).
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* Upgrade planning: Identifying areas where upgrades or additions
are needed to ensure that the network can minimize the effect of
node/link failures, mitigate QoS problems, or simply to support
growing demands.
* Cost-benefit analysis: Evaluating the costs and benefits of
upgrading or adding new resources to determine the most cost-
effective solutions.
By implementing a robust capacity planning process, organizations
can:
* Ensure better network reliability: Minimize downtime and ensure
that the network is always available when needed.
* Improve performance: Optimize network resources to support
business-critical applications and Services.
* Optimize costs: Avoid unnecessary over-provisioning by making
informed decisions based on data-driven insights.
* Support business growth: Scale the network to meet increasing
demands and support business expansion.
The capacity planning application will be able to retrieve a topology
layer and any network/node/termination point/link instances from the
SIMAP server via the SIMAP APIs and from the response it will be able
to map the traffic analysis to the entities (typically links and
router), evaluate their current utilization, evaluate which elements
to add to the network based on the growth forecasting, and finally
perform the 'what-if' failure analysis by simulating the removal of
link(s) and/or router(s) while evaluating the network performance.
3.7. Network Design
Network design involves defining both the logical structure, such as
access, aggregation, and core layers, and the physical layout,
including devices and links.
It serves as a blueprint, detailing how these elements interconnect
to deliver the intended network behavior and functionality. The
application will generate a candidate network topology, based on the
initial design and the current network topology; this candidate
network topology can then undergo further analysis (e.g., perform
traffic flow simulations to identify bottlenecks and redundancy
checks to ensure resilience) before being transformed into actionable
intent and, eventually, deployment actions.
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Throughout the network's lifecycle, the design rules embedded within
a topology can be continuously validated. For example, a link rule
might specify that a connection between core and aggregation layers
must have its source(s) and destination(s) located within the same
data center. Another example is to declare that a specific link type
should only exist between Core <-> Aggregation layer with certain
constraints on port optic speed, type (LR vs SR for instance), etc.
The network design application can (via SIMAP API):
* Write the intended network interconnect (topology + rules), this
is the intent of the network topology that cannot be retrieved
from the real network (e.g. our L2 topology interconnect intent,
or L3 topology interconnect intent). One network (in case of
small network) or interconnect of multiple networks (bigger
networks).
* Retrieve the proposed network interconnect (topology + rules)
- Use case can be for purpose of traffic simulation, testing
behavior under failures. Network simulation use case is
described in Section 3.8.
- Use case can be for purpose of comparing different proposed
network interconnects.
- Use case can be to build a simulated environment using this
design. Network simulation use case is described in
Section 3.8.
* Retrieve the intended network interconnect (topology + rules)
* At any point in time, compare the discovered topology with
intended one
- Potentially validating discovered device configurations with
intended ones assuming SIMAP has the external reference to
configuration from topology.
3.8. Network Simulation and Network Emulation
Network simulation is a process used to analyse the behaviour of
networks via software. It allows network engineers and researchers
to assess how the network protocols work under different conditions,
such as different topologies, traffic loads, network failures, or the
introduction of new devices. Network emulation, on the other hand,
replicates the behavior of a real-world network, allowing for more
realistic analysis compared to network simulation. While network
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simulation focuses on modeling and approximating network behavior,
network emulation involves creating a real-time, functional network
environment whose protocols behave exactly like a real network.
Ideally, network emulation uses the same software images as the real
network, but it could also be performed (with less accuracy) using
generic software.
3.8.1. Types of Network Simulation
There are several types of network simulations, each designed to
address specific needs and use cases. Below are the main categories
of network simulation:
1. Discrete event simulation: This is the most common type of
network simulation. It models a series of events that occur
at specific points in time. Each event triggers a change in
the state of a network component (e.g., a link is down, a card
fails, or a packet arrives).
2. Continuous simulation: In contrast to discrete event simulation,
continuous simulation models systems where variables change
continuously over time. Network parameters like bandwidth,
congestion, and throughput can be treated as continuous
functions.
The main use case is to model certain aspects of network
performance that evolve continuously, such as link speeds or
delay distributions in links that are impacted by
environmental conditions (such as microwave or satellite
links).
3. Monte Carlo simulation: This type of simulation uses statistical
methods to model and analyze networks under uncertain or
variable conditions. Monte Carlo simulations generate a large
number of random samples to predict the performance of a
network across multiple scenarios. It is used for
probabilistic analysis, risk assessment, and performance
evaluation under uncertain conditions.
3.8.2. Goals of Network Simulation
The simulations can be also classified depending on the goal of the
simulation.
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3.8.2.1. Network Protocol Analysis
This type of simulation focuses on simulating specific networking
protocols (IS-IS, OSPF, BGP, SR) to understand how they perform under
different conditions. It models the protocol operations and
interactions among devices in the network. For example, simulation
can be used to assess the impact of changing a link metric.
Moreover, specific features of the networking protocol can be tested.
For example, how fast-reroute performs in a given network topology.
3.8.2.2. Traffic Simulation
This simulation focuses on modelling traffic flow across the network,
including packet generation, flow control, routing, and congestion.
It aims to evaluate traffic's impact on network performance.
The main use is to model the impact of different types of traffic
(e.g., voice, video, mobile data, web browsing) and understand how
they affect the network's bandwidth and congestion levels. It can be
used to identify bottlenecks and assist the capacity planning
process.
3.8.2.3. Simulation of Different Topologies Under Normal and Failure
Scenarios
This type of simulation focuses on the structure and layout of the
network itself. It simulates different network topologies and their
impact on the network's performance. It can be used, together with
the traffic simulation, to evaluate the most efficient topology for a
network under normal conditions and considering factors like fault
tolerance.
3.9. Postmortem Replay
For the postmortem replay use case, the client application will use
the SIMAP APIs for the purpose of analysis of network Service
property evolution based on recorded changes. A collection of
relevant timestamped network events, such as routing updates,
configuration changes, link status modifications, traffic metrics
evolution, and Service characteristics, is being made accessible from
and/or within a SIMAP to support investigation and automated
processing. Using a structured format, the stored data can be
replayed in sequence, allowing network operators to examine
historical network behavior, diagnose issues, and assess the impact
of such events on Service assurance.
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The mechanism supports correlation with external data sources to
facilitate comprehensive post-mortem analysis. Beyond centralizing
and correlating such various sources of information, the SIMAP can
provide simulation of the network behaviour to assist investigations.
In essence, this use case builds upon a collection of other SIMAP use
cases, such as inventory queries, intent/service assurance, Service
KPIs, capacity planning, and simulation, to provide a thorough
understanding of a network event impacting Service assurance.
Note that this use case may serve as a component of Service
Disruption Detection fine tuning as described in
[I-D.ietf-nmop-network-anomaly-architecture].
3.10. Network Digital Twin (NDT)
Per [I-D.irtf-nmrg-network-digital-twin-arch], Network Digital Twin
(NDT) is a digital representation that is used in the context of
Networking and whose physical counterpart is a data network (e.g.,
provider network or enterprise network). Also, as discussed in
Section 9.2 of [I-D.irtf-nmrg-network-digital-twin-arch], network
element models and topology models help generate a virtual twin of
the network according to the network element configuration, operation
data, network topology relationship, link state and other network
information. The operation status can be monitored and displayed,
the network configuration change and optimization strategy can be
pre-verified and historical data can support e.g. postmorem replay
(Section 3.9))
Section 9.4 of [I-D.irtf-nmrg-network-digital-twin-arch] further
elaborates on the requirements on various interfaces:
* Network-facing interfaces are twin interfaces between the real
network and its twin entity. They are responsible for the
information exchange between a real network and NDT. SIMAP APIs
can be used within such interfaces.
* Application-facing interfaces are between the NDT and
applications. They are responsible for the information exchange
between Network Digital Twin and network applications. SIMAP APIs
can be used for specification of hypothetical network and service
states for 'what-if' analysis, e.g.. for feasibility checks
(Section 3.3), simulation or emulation (Section 3.8)). Such
analysis may be used in support of e.g. network capacity planning
(Section 3.6)) or network design (Section 3.7)).
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Section 9.4 of [I-D.irtf-nmrg-network-digital-twin-arch] recommends
that these interfaces are open and standardized so as to avoid either
hardware or software vendor lock and achieve interoperability.
While network emulation (Section 3.8) can be a component within an
NDT, the NDT itself is a broader construct that integrates multiple
modeling techniques, including emulation, simulation, and analytics,
to support intelligent network operations. NDT uses network
emulation and includes network emulation use case, but it also
interacts with the real network to support intelligent operations,
including predictive analytics, intent verification, and full
lifecycle management of network and services.
4. SIMAP Operator Requirements
The SIMAP operator requirements are split into three groups for
different target audiences:
* Functional requirements: These requirements are collected from
the operators and derived from the operators' use cases. Some
of the more specific semantic requirements were identified as
[RFC8345] gaps during the Hackathons with operators and added
as specific semantic requirements to the operator use cases.
* Design requirements: These requirements are derived from the
operator requirements. Although there is some duplication,
these are focused on summarizing the operators' requirements
for the design of the data model and API. These are functional
requirements translated into low-level requirements for the
model designers. The rationale for adopting this approach is
to ensure that the data model is designed according to the
operators' requirements and that they could be used for both
design and review of the candidate data models.
* Architecture requirements: Architectural (non-functional)
requirements are captured as well, as operators identified
performance needs, large scale support, and network discovery.
These are not data model requirements, but are requirements
either to drive the APIs design itself (e.g., to better
optimize performance) or for the SIMAP servers that expose a
SIMAP API. Although, they may be common sense requirements not
specific to SIMAP API, they are listed here for completeness.
4.1. Functional Requirements
The following are the operators' requirements for the SIMAP. Note
that some of these requirements are supported by default by
[RFC8345].
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REQ-BASIC-MODEL-SUPPORT: Basic model with network, node, link, and
termination point entity types.
This means that users of SIMAP must be able to reconstruct a
topology at any layer in an unambiguous manner via these core
concepts only, without the need to understand layer or technology
specific information.
REQ-LAYERED-MODEL: Topology layers from physical layer up to Service
layer.
SIMAP must provide views for all layers of network topology, from
physical network (ideally optical), Layer 2, Layer 3 up to Service
and intent views. It must provide flexibility to support both the
same network topology instance with multiple layers (e.g., Layer 2
and Layer 3) or separate network topology instances with
supporting relations between them (e.g., separate Layer 2 and
Layer 3). Multiple topology layers can be grouped into the same
network topology instance, if solution requires.
REQ-VIEWPOINTS: SIMAP should provide different views to different
client applications. For example, one client application may need
to see Layer 2 and Layer 3 layers in a single network topology
instance, while another client application may need to see them as
separate network topology instances.
REQ-PASSIVE-TOPO: SIMAP must support capability to model topology of
the complete network. If the implementation requires passive
topology to be part of the complete multi-layered topology, then
SIMAP must support the capability to model the passive part of the
network (in addition to the active part).
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.
The passive topology must be either implemented in the SIMAP (what
cannot be discovered can be added using the write API) or
accessible from the SIMAP. Whether the passive topology is
included as part of the SIMAP or accessible from the SIMAP is left
to the solutions.
REQ-PROG-OPEN-MODEL: Open and programmable SIMAP.
This includes "read" operations to retrieve the view of the
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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 live 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 and APIs, for multi-vendor
support.
SIMAP must provide the standard 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-API: SIMAP and common APIs, for multi-domain.
SIMAP and its APIs must be common over different network domains
(campus, core, data center, etc.).
This means that clients of the SIMAP APIs 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-GRAPH-TRAVERSAL: Topology graph traversal.
SIMAP must be optimized for graph traversal to support both
network path queries and other specific use case queries. This
means that the SIMAP must provide an efficient means to retrieve
network paths, to accommodate the difficulty operators experience
when retrieving network paths via the chain termination-
point->link->termination-point, without having a direct adjacency
relation. Additionally, SIMAP must enable efficient retrieval of
the data required by other use case queries.
REQ-TOPOLOGY-ABSTRACTION: Navigation across the abstraction levels.
A network (even a single layer network) can be represented in
multiple ways providing different abstraction views of the same
network. In such a case, it would be beneficial being able to
navigate amongst the different levels of abstractions (e.g. to
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understand which set of nodes in the native topology are actually
represented as a single node in an abstract topology being built
on top of the native topology). This navigation is different and
orthogonal to the multi-layer navigation where we need to report
which Layer 2 path is supporting a given Layer 3 node or link.
Nevertheless, it would not be the best practice to expose it via
different topology APIs and model. Please refer to the
Appendix A.2 for some background on the topology abstraction.
SIMAP must provide a mechanism to navigate across the abstraction
levels.
REQ-LIVE: Live network topology.
SIMAP must enable retrieval of multi-layered topology of a live
network.
Live network is the latest snapshot of the real network.
REQ-SNAPSHOT: Network snapshot topology.
SIMAP must enable retrieval of multi-layered topology of different
snapshots
Snapshot is the view of the network at any given point in time.
REQ-POTENTIAL: Potential new network topology.
SIMAP must enable both retrieval and write access to a potential
network topology.
A potential new network topology is a provisional view at a given
point in time that incorporates modifications relative to the
current snapshot. It may represent the full topology or only the
differences from the snapshot.
The view is needed for what-if analysis, pre-configuration, and
simulation.
REQ-INTENDED: Intended network topology.
SIMAP must enable both retrieval and write access to the intended
network topology that cannot be discovered from the real network
(e.g., intended Layer 2 Topology, intended Layer 3 Topology, and
passive topology that cannot be discovered).
The intended topology represents the desired topology, without
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always detailing the intermediate hops, devices or detailed links
that the current live topology contains. It can be used to verify
if the live topology complies with the intent.
REQ-SEMANTIC: Network topology semantics.
SIMAP must provide semantics for layered network topologies and
for linking external models/data.
The following requirements are more specific requirements for
semantics:
REQ-LAYER-NAVIGATE: SIMAP must provide capability to navigate both
within a topology layer and between topology layers.
Within-layer navigation means that SIMAP client applications
should be able to move among entities that belong to the same
layer. For example, in the IGP layer, the navigation should allow
moving between OSPF/IS-IS management domains, OSPF/IS-IS areas,
OSPF/IS-IS processes, OSPF/IS-IS interfaces, and OSPF/IS-IS links.
Between-layer navigation is the navigation across layers that
should display the dependencies of entities in one layer on those
in another. For instance, an IP interface that is supported by an
Ethernet interface should be visible when moving between the
corresponding layers.
REQ-EXTENSIBLE: SIMAP must be extensible with metadata. As
examples, a controller or the client application could add a
custom “location” attribute to a node to record its physical site,
or a controller could attach a “vendorId” field to a device node.
This demonstrates that arbitrary key-value metadata can be
appended to any element in the model without altering the core
schema.
REQ-PLUGG: SIMAP must be pluggable. That is,
* Must connect to other data models for device configuration,
inventory, configuration, assurance, etc. The SIMAP does not
contain the detailed device configuration, so a mechanism is
needed to be able to link it from SIMAP. SIMAP should also be
linked to a 'logical configuration inventory'. Several
examples of the type of logical information to be linked from
SIMAP: inventory of logical interfaces, inventory of ACLs,
inventory of routing policies, or geographic location.
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* Given that not all involved components can be available using
YANG, there is a need to connect SIMAP with other modelling
mechanisms.
REQ-BIDIR: SIMAP must provide a mechanism to model bidirectional
links. While data flows are unidirectional, the bidirectional
links are also common in networking. Examples are Ethernet
cables, bidirectional SONET rings, socket connection to the
server, etc., where a link is modeled as bidirectional, which in
turn might be supported as unidirectional links at the lower
layer.
REQ-MULTI-POINT: SIMAP must provide a mechanism to model multipoint
links. A topology model should be able to model any topology
type, including point to multipoint, bus, ring, star, tree, mesh,
hybrid and daisy chain. A topology model should also be able to
model any link cardinality, including point-to-point, point-to-
multipoint, multipoint-to-multipoint
REQ-MULTI-DOMAIN: SIMAP must provide a mechanism to model links and
nodes between networks when the implementation requires multi-
domain topologies, topologies with multiple IGP areas or any
network partitioning. This requirement is about covering
connectivity between different networks, sub-networks, or domains.
REQ-SUBNETWORK: SIMAP must provide a mechanism to model network
decomposition into sub-networks. The requirement is about
modelling hierarchical networks , Autonomous Systems (ASes) with
multiple areas, or a network with multiple domains (e.g., access,
core, data center).
The network can be partitioned by providing capability to have
multiple child network instances as part of a single parent
network, with a relation between the parent network and child
networks.
REQ-SUPPORTING: SIMAP must provide a mechanism to model supporting
relationships between different types of topological entities
(e.g., a termination point is supported by a node or a node is
supported by a network). This may be required to model supporting
relationships for termination points which are supported by
physical devices (e.g., a loopback interface on IP router).
REQ-STATUS: Links and nodes that are down must appear in the
topology. The status of the nodes and links must be either
implemented in the SIMAP or accessible from the SIMAP. Whether
the status is included as part of the SIMAP or accessible from the
SIMAP is left to the solutions.
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REQ-DATA-PLANE-FLOW: Provider data plane (Flow) needs to be
correlatable to underlay and customer data plane to overlay
topology
An SRv6 example:
In an SRv6-enabled network, the sourceIPv6Address field appears
twice in the IPFIX data-template/data-record for a captured flow
on an SRv6-enabled provider interface. Once in relation to
provider data plane in the underlay, and once as relation to the
customer data plane in the overlay.
SIMAP must provide the semantic capability that each
sourceIPv6Address can be mapped to the overlay and underlay
network topology. Both topologies might not be uniquely
addressed, the VPN context (in SRv6 these are the SID's, Section 3
of [RFC8986]) needs to be considered therefore as well.
IPFIX protocol, defined in [RFC7011], is the protocol for the
exchange of flow information from an Exporting Process to a
Collecting Process. Section 8 of [RFC7011] describes the
management of Templates and Option templates at the Exporting and
Collecting Processes, and states the following:
| If an Information Element is required more than once in a
| Template, the different occurrences of this Information Element
| SHOULD follow the logical order of their treatments by the
| Metering Process. For example, if a selected packet goes through
| two hash functions, and if the two hash values are sent within a
| single Template, the first occurrence of the hash value should
| belong to the first hash function in the Metering Process. For
| example, when exporting the two source IP addresses of an IPv4-in-
| IPv4 packet, the first sourceIPv4Address Information Element
| occurrence should be the IPv4 address of the outer header, while
| the second occurrence should be the address of the inner header.
| Collecting Processes MUST properly handle Templates with multiple
| identical Information Elements.
REQ-CONTROL-PLANE: Control-plane routing state must be correlatable
to the corresponding data-plane topology. For example, the
underlay control-plane routing state must correlate to the
underlay L3 topology, while the overlay control-plane routing
state must correlate to the overlay L3 network topology.
A BMP/BGP example:
The BMP peer distinguisher (Section 4.2 of [RFC7854]) needs to be
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correlateable to the VRF of a node and the next-hop attribute of
the NLRI in the BMP route-monitoring (Section 4.6 of [RFC7854])
encapsulated message to the underlay network topology while the
path attribute of the NLRI in the BMP route-monitoring
encapsulated message to the overlay topology.
4.2. Design Requirements
The following are the design requirements for the SIMAP data model:
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, depending on the solution, be either inside
or outside of the SIMAP. If outside of SIMAP, dynamic paths
could be linked to the SIMAP.
SIMAP should ensure that it is possible to represent the paths/
routes and leave the choice of what level of dynamics to represent
to the specific solution/implementations. The model needs to be
rich enough to represent any level of dynamics. However, from
experience, we suspect it can be the same model for all level of
dynamics.
REQ-PROPERTIES: SIMAP entities should mainly contain properties used
to identify topological entities at different layers, identify
their roles, and topological relationships between them.
SIMAP entities should also provide information required to define
semantics for layered network topologies, such as:
* link directionality,
* whether the links are multipoint or not and, if so, are whether
these links are point-to-multipoint or multipoint-to-multipoint,
* role of the termination points in the link (source, destination,
hub, spoke), and
* some generic mechanism to add metadata.
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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 data models in generic way.
The SIMAP relationships should also provide information required
to define semantics for layered network topologies, such as
providing:
* underlay and overlay relations between different types of
topological entities,
* additional information that helps with navigation inside a layer
and between the layers, for example, easy identification of
resources at the physical layer in primary versus backup paths, if
the underlay resources are used for load balancing or for backup,
* capability to model nodes, termination points, and links contained
in a network, but also nodes and links shared between networks,
and
* relationships between networks, either for modelling of underlay
and overlay or modelling network that contains multiple networks.
REQ-CONDITIONAL: Provide capability for conditional retrieval of
parts of SIMAP.
REQ-TEMPO-HISTO: Must support geo-spatial (geographic coordinates,
region, zone, etc.), temporal (when some fact is true, e.g., the
topology or topological entity created at 12:00 UTC), and
historical data (time-stamped historical changes, e.g. all changes
from 2019-01-01 to 2023-06-30).
The geo-spatial, temporal and historical can also be supported
external to the SIMAP.
4.3. Architectural Requirements
The following are the architectural requirements for the SIMAP server
implementations that provide SIMAP API, they are the non-functional
requirements for the SIMAP APIs and SIMAP server implementations:
REQ-SCALES: The SIMAP APIs and SIMAP server implementations must be
scalable, it must support any provider network, independent of its
size.
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REQ-PERFORMANCE: The SIMAP APIs and SIMAP server implementations
must be performant, and have acceptable response-time. Although
we are not to define the response time here.
REQ-USABILITY: The SIMAP APIs must be simple and easy to integrate
with the client applications, whose developers may not be
networking experts.
REQ-DISCOVERY: A network SIMAP server must perform the initial and
on-demand discovery of a network in order to provide the layered
topology via the SIMAP APIs to a client application.
REQ-SYNCH: The SIMAP server must perform the sync with the network
in order to provide up to date layered topology via SIMAP APIs to
a client application
REQ-SECURITY: The conventional NACM control access rules [RFC8341]
should apply. This includes module control access rules, protocol
operation control access rules, data node control access rules,
and notification control access rules.
5. Positioning SIMAP in the Context of the IETF Work
[RFC8199] advocates for a consistent classification of YANG modules
and introduces two abstraction layers for YANG modules:
* network element YANG modules
* network service YANG modules
The IRTF [RFC7426] defines the SDN layers and architecture and
proposes the following interfaces:
* southbound interfaces between the network devices and controllers/
managers
* service interface between controllers/managers and applications
[RFC8309] defines where service model might fit into the SDN
Architecture, although the service model does not require or preclude
the use of SDN. It shows the following models at different layers of
abstraction:
* device model, between network elements and controllers
* network model, between controllers and network orchestrators
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* service model, between network orchestrators and service
orchestrators
* customer service model, between service orchestrators and customer
[RFC8453] describes the ACTN architecture in the context of the YANG
service models. It shows how ACTN interfaces relate to device model,
network model and customer service model.
[RFC8969] describes a framework for Service and network management
automation that takes advantage of YANG modelling technologies. This
framework is drawn from a network operator perspective irrespective
of the origin of a data model. [RFC8969] introduces "network service
models" and describes the layering and representation of models
within a network operator as follows:
* device model, between device and controller
* network model (operator oriented), between controller (that
includes network orchestration function) and service orchestrator
* service model (customer oriented), between service orchestrator
and customer, this is network service model
The SIMAP can be used at different layers of abstraction and SIMAP
can provide topology at different interfaces. Although the SIMAP and
APIs is primarily positioned as northbound multi-layered topology
model from (SDN) Controllers, it can also be positioned as follows:
* In the context of [RFC8199], SIMAP can provide multi-layered
topology YANG module as part of both network element and network
service YANG modules
* In the context of [RFC7426], SIMAP can provide multi-layered
topology interface as part of both Southbound and Service
Interfaces
* In the context of [RFC8309], SIMAP can provide multi-layered
topology model as part of device model, network model, service
model and customer service model
* In the context of [RFC8453], SIMAP can provide multi-layered
topology model as part of SBI (southbound interface to network),
MPI (interface between multi-domain service coordinator and
network controller) and CMI (interface between customer network
controller and multi-domain service controller)
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* In the context of [RFC8969], SIMAP can provide multi-layered
topology model as part of device model, network model and network
service model
Appendix A documents some other IETF activities related to topology
modeling, it does not want to prescribe how SIMAP should be modeled
or which base models should be used, and it is added for
illustrational purposes only. Therefore it is not included in this
section, but added to the Appendix.
6. Security Considerations
As this document covers the SIMAP concepts, requirements, and use
cases, there is no specific security considerations other that those
discussed in Section 4.3.
Section 8 of [RFC8345] discusses security aspects that will be useful
when designing the SIMAP solution.
7. IANA Considerations
This document has no actions for IANA.
8. References
8.1. Normative References
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/rfc/rfc8341>.
8.2. Informative References
[I-D.ietf-ivy-network-inventory-topology]
Wu, B., Boucadair, M., Zhou, C., and Q. Wu, "A YANG
Network Data Model for Inventory Topology Mapping", Work
in Progress, Internet-Draft, draft-ietf-ivy-network-
inventory-topology-06, 28 February 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-ivy-
network-inventory-topology-06>.
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[I-D.ietf-ivy-network-inventory-yang]
Yu, C., Belotti, S., Bouquier, J., Peruzzini, F., and P.
Bedard, "A Base YANG Data Model for Network Inventory",
Work in Progress, Internet-Draft, draft-ietf-ivy-network-
inventory-yang-14, 5 February 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-ivy-
network-inventory-yang-14>.
[I-D.ietf-nmop-network-anomaly-architecture]
Graf, T., Du, W., Francois, P., and A. H. Feng, "A
Framework for a Network Anomaly Detection Architecture",
Work in Progress, Internet-Draft, draft-ietf-nmop-network-
anomaly-architecture-07, 18 January 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
network-anomaly-architecture-07>.
[I-D.ietf-nmop-network-incident-yang]
Hu, T., Contreras, L. M., Wu, Q., Davis, N., and C. Feng,
"A YANG Data Model for Network Incident Management", Work
in Progress, Internet-Draft, draft-ietf-nmop-network-
incident-yang-08, 13 February 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
network-incident-yang-08>.
[I-D.ietf-nmop-terminology]
Davis, N., Farrel, A., Graf, T., Wu, Q., and C. Yu, "Some
Key Terms for Network Fault and Problem Management", Work
in Progress, Internet-Draft, draft-ietf-nmop-terminology-
23, 18 August 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-nmop-
terminology-23>.
[I-D.ietf-opsawg-ntw-attachment-circuit]
Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
and B. Wu, "A Network YANG Data Model for Attachment
Circuits", Work in Progress, Internet-Draft, draft-ietf-
opsawg-ntw-attachment-circuit-16, 23 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
ntw-attachment-circuit-16>.
[I-D.ietf-opsawg-teas-attachment-circuit]
Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
and B. Wu, "YANG Data Models for Bearers and 'Attachment
Circuits'-as-a-Service (ACaaS)", Work in Progress,
Internet-Draft, draft-ietf-opsawg-teas-attachment-circuit-
20, 23 January 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
teas-attachment-circuit-20>.
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[I-D.ietf-teas-te-topo-and-tunnel-modeling]
Bryskin, I., Beeram, V. P., Saad, T., and X. Liu, "TE
Topology and Tunnel Modeling for Transport Networks", Work
in Progress, Internet-Draft, draft-ietf-teas-te-topo-and-
tunnel-modeling-06, 12 July 2020,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-te-
topo-and-tunnel-modeling-06>.
[I-D.irtf-nmrg-network-digital-twin-arch]
Zhou, C., Yang, H., Duan, X., Lopez, D., Pastor, A., Wu,
Q., Boucadair, M., and C. Jacquenet, "Network Digital
Twin: Concepts and Reference Architecture", Work in
Progress, Internet-Draft, draft-irtf-nmrg-network-digital-
twin-arch-12, 27 February 2026,
<https://datatracker.ietf.org/doc/html/draft-irtf-nmrg-
network-digital-twin-arch-12>.
[I-D.ogondio-nmop-isis-topology]
de Dios, O. G., Barguil, S., Lopez, V., Ceccarelli, D.,
and B. Claise, "A YANG Data Model for Intermediate System
to intermediate System (IS-IS) Topology", Work in
Progress, Internet-Draft, draft-ogondio-nmop-isis-
topology-01, 20 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ogondio-nmop-
isis-topology-01>.
[I-D.ogondio-opsawg-ospf-topology]
de Dios, O. G., Barguil, S., and V. Lopez, "A YANG Data
Model for Open Shortest Path First (OSPF) Topology", Work
in Progress, Internet-Draft, draft-ogondio-opsawg-ospf-
topology-01, 23 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ogondio-
opsawg-ospf-topology-01>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<https://www.rfc-editor.org/rfc/rfc3444>.
[RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity",
RFC 5136, DOI 10.17487/RFC5136, February 2008,
<https://www.rfc-editor.org/rfc/rfc5136>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<https://www.rfc-editor.org/rfc/rfc7011>.
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[RFC7426] Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
Defined Networking (SDN): Layers and Architecture
Terminology", RFC 7426, DOI 10.17487/RFC7426, January
2015, <https://www.rfc-editor.org/rfc/rfc7426>.
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/rfc/rfc7854>.
[RFC7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC7926, July 2016,
<https://www.rfc-editor.org/rfc/rfc7926>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/rfc/rfc7950>.
[RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", RFC 8199, DOI 10.17487/RFC8199, July
2017, <https://www.rfc-editor.org/rfc/rfc8199>.
[RFC8299] Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki,
"YANG Data Model for L3VPN Service Delivery", RFC 8299,
DOI 10.17487/RFC8299, January 2018,
<https://www.rfc-editor.org/rfc/rfc8299>.
[RFC8309] Wu, Q., Liu, W., and A. Farrel, "Service Models
Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
<https://www.rfc-editor.org/rfc/rfc8309>.
[RFC8345] Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
2018, <https://www.rfc-editor.org/rfc/rfc8345>.
[RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC8453, August 2018,
<https://www.rfc-editor.org/rfc/rfc8453>.
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[RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
Data Model for Layer 2 Virtual Private Network (L2VPN)
Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
2018, <https://www.rfc-editor.org/rfc/rfc8466>.
[RFC8795] Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
O. Gonzalez de Dios, "YANG Data Model for Traffic
Engineering (TE) Topologies", RFC 8795,
DOI 10.17487/RFC8795, August 2020,
<https://www.rfc-editor.org/rfc/rfc8795>.
[RFC8944] Dong, J., Wei, X., Wu, Q., Boucadair, M., and A. Liu, "A
YANG Data Model for Layer 2 Network Topologies", RFC 8944,
DOI 10.17487/RFC8944, November 2020,
<https://www.rfc-editor.org/rfc/rfc8944>.
[RFC8969] Wu, Q., Ed., Boucadair, M., Ed., Lopez, D., Xie, C., and
L. Geng, "A Framework for Automating Service and Network
Management with YANG", RFC 8969, DOI 10.17487/RFC8969,
January 2021, <https://www.rfc-editor.org/rfc/rfc8969>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/rfc/rfc8986>.
[RFC9179] Hopps, C., "A YANG Grouping for Geographic Locations",
RFC 9179, DOI 10.17487/RFC9179, February 2022,
<https://www.rfc-editor.org/rfc/rfc9179>.
[RFC9182] Barguil, S., Gonzalez de Dios, O., Ed., Boucadair, M.,
Ed., Munoz, L., and A. Aguado, "A YANG Network Data Model
for Layer 3 VPNs", RFC 9182, DOI 10.17487/RFC9182,
February 2022, <https://www.rfc-editor.org/rfc/rfc9182>.
[RFC9291] Boucadair, M., Ed., Gonzalez de Dios, O., Ed., Barguil,
S., and L. Munoz, "A YANG Network Data Model for Layer 2
VPNs", RFC 9291, DOI 10.17487/RFC9291, September 2022,
<https://www.rfc-editor.org/rfc/rfc9291>.
[RFC9408] Boucadair, M., Ed., Gonzalez de Dios, O., Barguil, S., Wu,
Q., and V. Lopez, "A YANG Network Data Model for Service
Attachment Points (SAPs)", RFC 9408, DOI 10.17487/RFC9408,
June 2023, <https://www.rfc-editor.org/rfc/rfc9408>.
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[RFC9417] Claise, B., Quilbeuf, J., Lopez, D., Voyer, D., and T.
Arumugam, "Service Assurance for Intent-Based Networking
Architecture", RFC 9417, DOI 10.17487/RFC9417, July 2023,
<https://www.rfc-editor.org/rfc/rfc9417>.
[RFC9418] Claise, B., Quilbeuf, J., Lucente, P., Fasano, P., and T.
Arumugam, "A YANG Data Model for Service Assurance",
RFC 9418, DOI 10.17487/RFC9418, July 2023,
<https://www.rfc-editor.org/rfc/rfc9418>.
[RFC9522] Farrel, A., Ed., "Overview and Principles of Internet
Traffic Engineering", RFC 9522, DOI 10.17487/RFC9522,
January 2024, <https://www.rfc-editor.org/rfc/rfc9522>.
Appendix A. Related IETF Activities
Note: The models cited in this section are provided for
illustration purposes. It is out of scope to recomend which
models will be used as base to build the SIMAP.
A.1. Network Topology
Interestingly, we could not find any network topology definition in
IETF RFCs (not even in [RFC8345]) or Internet-Drafts. However, it is
mentioned in multiple documents. As an example, in Overview and
Principles of Internet Traffic Engineering [RFC9522], 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)
|
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| * 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.
Another example is [RFC8453] that defines native topology, abstract
topology, black topology, and grey topology, but all in the context
of actual topology and physical topology that are not specifically
defined.
A.2. Topology Abstraction
Please refer to the following documents for some background on
topology abstractions:
* [RFC7926] defines topology abstraction.
* Section 5 of [RFC8453] describes the topology abstraction methods
and discusses topology abstraction factors, types, and their
context in the ACTN architecture.
* Section 3.13 of [RFC8795] defines abstract TE topologies.
* Section 4.1 of [RFC8795] defines native TE topologies.
* Section 4.4 of [RFC8795] describes how to deal with multiple
abstract TE topologies provided by the same provider.
* Section 1.3 of [I-D.ietf-teas-te-topo-and-tunnel-modeling] gives
some background on topology abstraction.
A.3. Core SIMAP Components
The following specifications are relevant to the core functions
provided by the SIMAP:
* IETF network model and network topology model [RFC8345]
* A YANG grouping for geographic location [RFC9179]
* IETF modules that augment [RFC8345] for different technologies:
- A YANG data model for Traffic Engineering (TE) Topologies
[RFC8795]
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- A YANG data model for Layer 2 network topologies [RFC8944]
- A YANG data model for OSFP topology
[I-D.ogondio-opsawg-ospf-topology]
- A YANG data model for IS-IS topology
[I-D.ogondio-nmop-isis-topology]
A.4. Additional SIMAP Components
The SIMAP may need to link to the following models, some are already
augmenting [RFC8345]:
* Service Attachment Point (SAP) [RFC9408], augments 'ietf-network'
data model [RFC8345] by adding the SAP.
* SAIN [RFC9417] [RFC9418]
* Network Inventory Model [I-D.ietf-ivy-network-inventory-yang]
focuses on physical and virtual inventory. Logical inventory is
currently outside of the scope. It does not augment [RFC8345].
* [I-D.ietf-ivy-network-inventory-topology] correlates the network
inventory with the general topology via RFC8345 augmentations that
reference inventory.
* KPIs: delay, jitter, loss
* Attachment Circuits (ACs) [I-D.ietf-opsawg-ntw-attachment-circuit]
and [I-D.ietf-opsawg-teas-attachment-circuit]
* Configuration: The L2SM [RFC8466], L3SM [RFC8299], L2NM [RFC9291],
and L3NM [RFC9182]
* Incident Management for Network Services
[I-D.ietf-nmop-network-incident-yang]
Acknowledgments
Many thanks to Mohamed Boucadair and Reshad Rahman for their valuable
contributions, reviews, and comments. Many thanks to Adrian Farrel
for his SIMAP suggestion and helping to agree the terminology. Many
thanks to Chongfeng Xie, Dan Voyer, Brad Peters, Diego Lopez, Ignacio
Dominguez Martinez-Casanueva, Alex Huang Feng, Italo Busi, Wu Bo,
Sherif Mostafa, Christopher Janz, Rob Evans, Danielle Ceccarelli,
Sergio Belotti, Aihua Guo and many others for their contributions,
suggestions and comments.
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Many thanks to Nigel Davis ndavis@ciena.com (mailto:ndavis@ciena.com)
for the valuable discussions and his confirmation of the modelling
requirements.
Contributors
Ahmed Elhassany
Swisscom
Email: Ahmed.Elhassany@swisscom.com
Authors' Addresses
Olga Havel
Huawei
Email: olga.havel@huawei.com
Benoit Claise
Everything OPS
Email: benoit@everything-ops.net
Oscar Gonzalez de Dios
Telefonica
Email: oscar.gonzalezdedios@telefonica.com
Thomas Graf
Swisscom
Email: thomas.graf@swisscom.com
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