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Keywords: Model Driven, YANG Data Model, automation, service delivery, notification, SDN

Internet Engineering Task Force (IETF) Q. Wu, Ed.
Request for Comments: 8969 Huawei
Category: Informational M. Boucadair, Ed.
ISSN: 2070-1721 Orange
D. Lopez
Telefonica I+D
C. Xie
China Telecom
L. Geng
China Mobile
January 2021
A Framework for Automating Service and Network Management with YANG
Abstract
Data models provide a programmatic approach to represent services and
networks. Concretely, they can be used to derive configuration
information for network and service components, and state information
that will be monitored and tracked. Data models can be used during
the service and network management life cycle (e.g., service
instantiation, service provisioning, service optimization, service
monitoring, service diagnosing, and service assurance). Data models
are also instrumental in the automation of network management, and
they can provide closed-loop control for adaptive and deterministic
service creation, delivery, and maintenance.
This document describes a framework for service and network
management automation that takes advantage of YANG modeling
technologies. This framework is drawn from a network operator
perspective irrespective of the origin of a data model; thus, it can
accommodate YANG modules that are developed outside the IETF.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8969.
Copyright Notice
Copyright (c) 2021 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 extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction
2. Terminology and Abbreviations
2.1. Terminology
2.2. Abbreviations
3. Architectural Concepts and Goals
3.1. Data Models: Layering and Representation
3.2. Automation of Service Delivery Procedures
3.3. Service Fulfillment Automation
3.4. YANG Module Integration
4. Functional Blocks and Interactions
4.1. Service Life-Cycle Management Procedure
4.1.1. Service Exposure
4.1.2. Service Creation/Modification
4.1.3. Service Assurance
4.1.4. Service Optimization
4.1.5. Service Diagnosis
4.1.6. Service Decommission
4.2. Service Fulfillment Management Procedure
4.2.1. Intended Configuration Provision
4.2.2. Configuration Validation
4.2.3. Performance Monitoring
4.2.4. Fault Diagnostic
4.3. Multi-layer/Multi-domain Service Mapping
4.4. Service Decomposition
5. YANG Data Model Integration Examples
5.1. L2VPN/L3VPN Service Delivery
5.2. VN Life-Cycle Management
5.3. Event-Based Telemetry in the Device Self Management
6. Security Considerations
6.1. Service Level
6.2. Network Level
6.3. Device Level
7. IANA Considerations
8. References
8.1. Normative References
8.2. Informative References
Appendix A. Layered YANG Module Examples Overview
A.1. Service Models: Definition and Samples
A.2. Schema Mount
A.3. Network Models: Samples
A.4. Device Models: Samples
A.4.1. Model Composition
A.4.2. Device Management
A.4.3. Interface Management
A.4.4. Some Device Model Examples
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
Service management systems usually comprise service activation/
provision and service operation. Current service delivery
procedures, from the processing of customer requirements and orders
to service delivery and operation, typically assume the manipulation
of data sequentially into multiple Operations Support System (OSS) or
Business Support System (BSS) applications that may be managed by
different departments within the service provider's organization
(e.g., billing factory, design factory, network operation center).
Many of these applications have been developed in house over the
years and operate in a silo mode. As a result:
* The lack of standard data input/output (i.e., data model) raises
many challenges in system integration and often results in manual
configuration tasks.
* Service fulfillment systems might have a limited visibility on the
network state and may therefore have a slow response to network
changes.
Software-Defined Networking (SDN) becomes crucial to address these
challenges. SDN techniques are meant to automate the overall service
delivery procedures and typically rely upon standard data models.
These models are used not only to reflect service providers' savoir
faire, but also to dynamically instantiate and enforce a set of
service-inferred policies that best accommodate what has been defined
and possibly negotiated with the customer. [RFC7149] provides a
first tentative attempt to rationalize that service provider's view
on the SDN space by identifying concrete technical domains that need
to be considered and for which solutions can be provided. These
include:
* Techniques for the dynamic discovery of topology, devices, and
capabilities, along with relevant information and data models that
are meant to precisely document such topology, devices, and their
capabilities.
* Techniques for exposing network services [RFC8309] and their
characteristics.
* Techniques used by service-derived dynamic resource allocation and
policy enforcement schemes, so that networks can be programmed
accordingly.
* Dynamic feedback mechanisms that are meant to assess how
efficiently a given policy (or a set thereof) is enforced from a
service fulfillment and assurance perspective.
Models are key for each of the four technical items above. Service
and network management automation is an important step to improve the
agility of network operations. Models are also important to ease
integrating multi-vendor solutions.
YANG module [RFC7950] developers have taken both top-down and bottom-
up approaches to develop modules [RFC8199] and to establish a mapping
between a network technology and customer requirements at the top or
abstracting common constructs from various network technologies at
the bottom. At the time of writing this document (2020), there are
many YANG data models, including configuration and service models,
that have been specified or are being specified by the IETF. They
cover many of the networking protocols and techniques. However, how
these models work together to configure a function, manage a set of
devices involved in a service, or provide a service is something that
is not currently documented either within the IETF or other Standards
Development Organizations (SDOs).
Many of the YANG modules listed in this document are used to exchange
data between NETCONF/RESTCONF clients and servers [RFC6241][RFC8040].
Nevertheless, YANG is a transport-independent data modeling language.
It can thus be used independently of NETCONF/RESTCONF. For example,
YANG can be used to define abstract data structures [RFC8791] that
can be manipulated by other protocols (e.g., [DOTS-DDOS]).
This document describes an architectural framework for service and
network management automation (Section 3) that takes advantage of
YANG modeling technologies and investigates how YANG data models at
different layers interact with each other (e.g., Service Mapping,
model composition) in the context of service delivery and fulfillment
(Section 4). Concretely, the following benefits can be provided:
* Vendor-agnostic interfaces managing a service and the underlying
network are allowed.
* Movement from deployment schemes where vendor-specific network
managers are required to a scheme where the entities that are
responsible for orchestrating and controlling services and network
resources provided by multi-vendor devices are unified is allowed.
* Data inheritance and reusability among the various architecture
layers thus promoting a network-wise provisioning instead of
device-specific configuration is eased.
* Dynamically feeding a decision-making process (e.g., Controllers,
Orchestrators) with notifications that will trigger appropriate
actions, allowing that decision-making process to continuously
adjust a network (and thus the involved resources) to deliver the
service that conforms to the intended parameters (service
objectives) is allowed.
This framework is drawn from a network operator perspective
irrespective of the origin of a data model; it can also accommodate
YANG modules that are developed outside the IETF. The document
covers service models that are used by an operator to expose its
services and capture service requirements from the customers
(including other operators). Nevertheless, the document does not
elaborate on the communication protocol(s) that makes use of these
service models in order to request and deliver a service. Such
considerations are out of scope.
The document identifies a list of use cases to exemplify the proposed
approach (Section 5), but it does not claim nor aim to be exhaustive.
Appendix A lists some examples to illustrate the layered YANG modules
view.
2. Terminology and Abbreviations
2.1. Terminology
The following terms are defined in [RFC8309] and [RFC8199] and are
not redefined here:
* Network Operator
* Customer
* Service
* Data Model
* Service Model
* Network Element Model
In addition, the document makes use of the following terms:
Network Model:
Describes a network-level abstraction (or a subset of aspects of a
network infrastructure), including devices and their subsystems,
and relevant protocols operating at the link and network layers
across multiple devices. This model corresponds to the network
configuration model discussed in [RFC8309].
It can be used by a network operator to allocate resources (e.g.,
tunnel resource, topology resource) for the service or schedule
resources to meet the service requirements defined in a service
model.
Network Domain:
Refers to a network partitioning that is usually followed by
network operators to delimit parts of their network. "access
network" and "core network" are examples of network domains.
Device Model:
Refers to the Network Element YANG data model described in
[RFC8199] or the device configuration model discussed in
[RFC8309].
Device models are also used to refer to model a function embedded
in a device (e.g., Network Address Translation (NAT) [RFC8512],
Access Control Lists (ACLs) [RFC8519]).
Pipe:
Refers to a communication scope where only one-to-one (1:1)
communications are allowed. The scope can be identified between
ingress and egress nodes, two service sites, etc.
Hose:
Refers to a communication scope where one-to-many (1:N)
communications are allowed (e.g., one site to multiple sites).
Funnel:
Refers to a communication scope where many-to-one (N:1)
communications are allowed.
2.2. Abbreviations
The following abbreviations are used in the document:
ACL Access Control List
AS Autonomous System
AP Access Point
CE Customer Edge
DBE Data Border Element
E2E End-to-End
ECA Event Condition Action
L2VPN Layer 2 Virtual Private Network
L3VPN Layer 3 Virtual Private Network
L3SM L3VPN Service Model
L3NM L3VPN Network Model
NAT Network Address Translation
OAM Operations, Administration, and Maintenance
OWD One-Way Delay
PE Provider Edge
PM Performance Monitoring
QoS Quality of Service
RD Route Distinguisher
RT Route Target
SBE Session Border Element
SDN Software-Defined Networking
SP Service Provider
TE Traffic Engineering
VN Virtual Network
VPN Virtual Private Network
VRF Virtual Routing and Forwarding
3. Architectural Concepts and Goals
3.1. Data Models: Layering and Representation
As described in Section 2 of [RFC8199], layering of modules allows
for better reusability of lower-layer modules by higher-level modules
while limiting duplication of features across layers.
Data models in the context of network management can be classified
into service, network, and device models. Different service models
may rely on the same set of network and/or device models.
Service models traditionally follow a top-down approach and are
mostly customer-facing YANG modules providing a common model
construct for higher-level network services (e.g., Layer 3 Virtual
Private Network (L3VPN)). Such modules can be mapped to network
technology-specific modules at lower layers (e.g., tunnel, routing,
Quality of Service (QoS), security). For example, service models can
be used to characterize the network service(s) to be ensured between
service nodes (ingress/egress) such as:
* the communication scope (pipe, hose, funnel, etc.),
* the directionality (inbound/outbound),
* the traffic performance guarantees expressed using metrics such as
One-Way Delay (OWD) [RFC7679] or One-Way Loss [RFC7680]; a summary
of performance metrics maintained by IANA can be found in [IPPM],
* link capacity [RFC5136] [METRIC-METHOD],
* etc.
Figure 1 depicts the example of a Voice over IP (VoIP) service that
relies upon connectivity services offered by a network operator. In
this example, the VoIP service is offered to the network operator's
customers by Service Provider 1 (SP1). In order to provide global
VoIP reachability, SP1 Service Site interconnects with other Service
Providers service sites typically by interconnecting Session Border
Elements (SBEs) and Data Border Elements (DBEs) [RFC5486][RFC6406].
For other VoIP destinations, sessions are forwarded over the
Internet. These connectivity services can be captured in a YANG
service model that reflects the service attributes that are shown in
Figure 2. This example follows the IP Connectivity Provisioning
Profile template defined in [RFC7297].
,--,--,--. ,--,--,--.
,-' SP1 `-. ,-' SP2 `-.
( Service Site ) ( Service Site )
`-. ,-' `-. ,-'
`--'--'--' `--'--'--'
x | o * * |
(2)x | o * * |
,x-,--o-*-. (1) ,--,*-,--.
,-' x o * * * * * * * * * `-.
( x o +----( Internet )
User---(x x x o o o o o o o o o o o o o o o o o o
`-. ,-' `-. ,-' (3)
`--'--'--' `--'--'--'
Network Operator
**** (1) Inter-SP connectivity
xxxx (2) Customer-to-SP connectivity
oooo (3) SP to any destination connectivity
Figure 1: An Example of Service Connectivity Components
In reference to Figure 2, "Full traffic performance guarantees class"
refers to a service class where all traffic performance metrics
included in the service model (OWD, loss, delay variation) are
guaranteed, while "Delay traffic performance guarantees class" refers
to a service class where only OWD is guaranteed.
Connectivity: Scope and Guarantees
(1) Inter-SP connectivity
- Pipe scope from the local to the remote SBE/DBE
- Full traffic performance guarantees class
(2) Customer-to-SP connectivity
- Hose/Funnel scope connecting the local SBE/DBE
to the customer access points
- Full traffic performance guarantees class
(3) SP to any destination connectivity
- Hose/Funnel scope from the local SBE/DBE to the
Internet gateway
- Delay traffic performance guarantees class
Flow Identification
* Destination IP address (SBE, DBE)
* DSCP marking
Traffic Isolation
* VPN
Routing & Forwarding
* Routing rule to exclude some ASes from the inter-domain
paths
Notifications (including feedback)
* Statistics on aggregate traffic to adjust capacity
* Failures
* Planned maintenance operations
* Triggered by thresholds
Figure 2: Sample Attributes Captured in a Service Model
Network models are mainly network-resource-facing modules; they
describe various aspects of a network infrastructure, including
devices and their subsystems, and relevant protocols operating at the
link and network layers across multiple devices (e.g., network
topology and traffic-engineering tunnel modules).
Device (and function) models usually follow a bottom-up approach and
are mostly technology-specific modules used to realize a service
(e.g., BGP, ACL).
Each level maintains a view of the supported YANG modules provided by
lower levels (see for example, Appendix A). Mechanisms such as the
YANG library [RFC8525] can be used to expose which YANG modules are
supported by nodes in lower levels.
Figure 3 illustrates the overall layering model. The reader may
refer to Section 4 of [RFC8309] for an overview of "Orchestrator" and
"Controller" elements. All these elements (i.e., Orchestrator(s),
Controller(s), device(s)) are under the responsibility of the same
operator.
+-----------------------------------------------------------------+
| Hierarchy Abstraction |
| |
| +-----------------------+ Service Model |
| | Orchestrator | (Customer Oriented) |
| |+---------------------+| Scope: "1:1" Pipe model |
| || Service Modeling || |
| |+---------------------+| |
| | | Bidirectional |
| |+---------------------+| +-+ Capacity, OWD +-+ |
| ||Service Orchestration|| | +----------------+ | |
| |+---------------------+| +-+ +-+ |
| +-----------------------+ Ingress Egress |
| |
| |
| +-----------------------+ Network Model |
| | Controller | (Operator Oriented) |
| |+---------------------+| +-+ +--+ +---+ +-+ |
| || Network Modeling || | | | | | | | | |
| |+---------------------+| | o----o--o----o---o---o | |
| | | +-+ +--+ +---+ +-+ |
| |+---------------------+| src dst |
| ||Network Orchestration|| L3VPN over TE |
| |+---------------------+| Instance Name/Access Interface |
| +-----------------------+ Protocol Type/Capacity/RD/RT/... |
| |
| |
| +-----------------------+ Device Model |
| | Device | |
| |+--------------------+ | |
| || Device Modeling | | Interface add, BGP Peer, |
| |+--------------------+ | Tunnel ID, QoS/TE, ... |
| +-----------------------+ |
+-----------------------------------------------------------------+
Figure 3: Layering and Representation within a Network Operator
A composite service offered by a network operator may rely on
services from other operators. In such a case, the network operator
acts as a customer to request services from other networks. The
operators providing these services will then follow the layering
depicted in Figure 3. The mapping between a composite service and a
third-party service is maintained at the orchestration level. From a
data-plane perspective, appropriate traffic steering policies (e.g.,
Service Function Chaining [RFC7665]) are managed by the network
controllers to guide how/when a third-party service is invoked for
flows bound to a composite service.
The layering model depicted in Figure 3 does not make any assumption
about the location of the various entities (e.g., Controller,
Orchestrator) within the network. As such, the architecture does not
preclude deployments where, for example, the Controller is embedded
on a device that hosts other functions that are controlled via YANG
modules.
In order to ease the mapping between layers and data reuse, this
document focuses on service models that are modeled using YANG.
Nevertheless, fully compliant with Section 3 of [RFC8309], Figure 3
does not preclude service models to be modeled using data modeling
languages other than YANG.
3.2. Automation of Service Delivery Procedures
Service models can be used by a network operator to expose its
services to its customers. Exposing such models allows automation of
the activation of service orders and thus the service delivery. One
or more monolithic service models can be used in the context of a
composite service activation request (e.g., delivery of a caching
infrastructure over a VPN). Such models are used to feed a decision-
making intelligence to adequately accommodate customer needs.
Also, such models may be used jointly with services that require
dynamic invocation. An example is provided by the service modules
defined by the DOTS WG to dynamically trigger requests to handle
Distributed Denial-of-Service (DDoS) attacks [RFC8783]. The service
filtering request modeled using [RFC8783] will be translated into
device-specific filtering (e.g., ACLs defined in [RFC8519]) that
fulfills the service request.
Network models can be derived from service models and used to
provision, monitor, and instantiate the service. Also, they are used
to provide life-cycle management of network resources. Doing so is
meant to:
* expose network resources to customers (including other network
operators) to provide service fulfillment and assurance.
* allow customers (or network operators) to dynamically adjust the
network resources based on service requirements as described in
service models (e.g., Figure 2) and the current network
performance information described in the telemetry modules.
Note that it is out of the scope of this document to elaborate on the
communication protocols that are used to implement the interface
between the service ordering (customer) and service order handling
(provider).
3.3. Service Fulfillment Automation
To operate a service, the settings of the parameters in the device
models are derived from service models and/or network models and are
used to:
* Provision each involved network function/device with the proper
configuration information.
* Operate the network based on service requirements as described in
the service model(s) and local operational guidelines.
In addition, the operational state including configuration that is in
effect together with statistics should be exposed to upper layers to
provide better network visibility and assess to what extent the
derived low-level modules are consistent with the upper-level inputs.
Filters are enforced on the notifications that are communicated to
Service layers. The type and frequency of notifications may be
agreed upon in the service model.
Note that it is important to correlate telemetry data with
configuration data to be used for closed loops at the different
stages of service delivery, from resource allocation to service
operation, in particular.
3.4. YANG Module Integration
To support top-down service delivery, YANG modules at different
levels or at the same level need to be integrated for proper service
delivery (including proper network setup). For example, the service
parameters captured in service models need to be decomposed into a
set of configuration/notification parameters that may be specific to
one or more technologies; these technology-specific parameters are
grouped together to define technology-specific device-level models or
network-level models.
In addition, these technology-specific device or network models can
be further integrated with each other using the schema mount
mechanism [RFC8528] to provision each involved network function/
device or each involved network domain to support newly added modules
or features. A collection of integrated device models can be loaded
and validated during implementation.
High-level policies can be defined at service or network models
(e.g., "Autonomous System Number (ASN) Exclude" in the example
depicted in Figure 2). Device models will be tweaked accordingly to
provide policy-based management. Policies can also be used for
telemetry automation, e.g., policies that contain conditions to
trigger the generation and pushing of new telemetry data.
4. Functional Blocks and Interactions
The architectural considerations described in Section 3 lead to the
life-cycle management architecture illustrated in Figure 4 and
described in the following subsections.
+------------------+
............... | |
Service level | |
V |
E2E E2E E2E E2E
Service --> Service ---------> Service ------------> Service
Exposure Creation ^ Optimization ^ Diagnosis
/Modification | | |
^ | |Diff | |
E2E | | | E2E | |
Service ----+ | | Service | |
Decommission | +------ Assurance --+ |
| ^ |
Multi-layer | | |
Multi-domain | | |
Service Mapping| | |
............... |<-----------------+ | |
Network level | | +-------+ v
V | | Specific
Specific Specific | Service
Service --------> Service <--+ | Diagnosis
Creation ^ Optimization | | |
/Modification | | | |
| |Diff | | |
| | Specific --+ | |
Service | | Service | |
Decomposition | +----- Assurance ----+ |
| ^ |
............... | | Aggregation |
Device level | +------------+ |
V | |
Service Intent | v
Fulfillment Config ----> Config ----> Performance ----> Fault
Provision Validation Monitoring Diagnostic
Figure 4: Service and Network Life-Cycle Management
4.1. Service Life-Cycle Management Procedure
Service life-cycle management includes end-to-end service life-cycle
management at the service level and technology-specific network life-
cycle management at the network level.
The end-to-end service life-cycle management is technology-
independent service management and spans across multiple network
domains and/or multiple layers while technology-specific service
life-cycle management is technology domain-specific or layer-specific
service life-cycle management.
4.1.1. Service Exposure
A service in the context of this document (sometimes called "Network
Service") is some form of connectivity between customer sites and the
Internet or between customer sites across the operator's network and
across the Internet.
Service exposure is used to capture services offered to customers
(ordering and order handling). One example is that a customer can
use an L3VPN Service Model (L3SM) to request L3VPN service by
providing the abstract technical characterization of the intended
service between customer sites.
Service model catalogs can be created to expose the various services
and the information needed to invoke/order a given service.
4.1.2. Service Creation/Modification
A customer is usually unaware of the technology that the network
operator has available to deliver the service, so the customer does
not make requests specific to the underlying technology but is
limited to making requests specific to the service that is to be
delivered. This service request can be filled using a service model.
Upon receiving a service request, and assuming that appropriate
authentication and authorization checks have been made with success,
the service Orchestrator/management system should verify whether the
service requirements in the service request can be met (i.e., whether
there are sufficient resources that can be allocated with the
requested guarantees).
If the request is accepted, the service Orchestrator/management
system maps such a service request to its view. This view can be
described as a technology-specific network model or a set of
technology-specific device models, and this mapping may include a
choice of which networks and technologies to use depending on which
service features have been requested.
In addition, a customer may require a change in the underlying
network infrastructure to adapt to new customers' needs and service
requirements (e.g., service a new customer site, add a new access
link, or provide disjoint paths). This service modification can be
issued following the same service model used by the service request.
Withdrawing a service is discussed in Section 4.1.6.
4.1.3. Service Assurance
The performance measurement telemetry (Section 4.2.3) can be used to
provide service assurance at service and/or network levels. The
performance measurement telemetry model can tie with service or
network models to monitor network performance or Service Level
Agreements.
4.1.4. Service Optimization
Service optimization is a technique that gets the configuration of
the network updated due to network changes, incident mitigation, or
new service requirements. One example is once a tunnel or a VPN is
set up, performance monitoring information or telemetry information
per tunnel (or per VPN) can be collected and fed into the management
system. If the network performance doesn't meet the service
requirements, the management system can create new VPN policies
capturing network service requirements and populate them into the
network.
Both network performance information and policies can be modeled
using YANG. With Policy-based management, self-configuration and
self-optimization behavior can be specified and implemented.
The overall service optimization is managed at the service level,
while the network level is responsible for the optimization of the
specific network services it provides.
4.1.5. Service Diagnosis
Operations, Administration, and Maintenance (OAM) are important
networking functions for service diagnosis that allow network
operators to:
* monitor network communications (i.e., reachability verification
and Continuity Check)
* troubleshoot failures (i.e., fault verification and localization)
* monitor service level agreements and performance (i.e.,
performance management)
When the network is down, service diagnosis should be in place to
pinpoint the problem and provide recommendations (or instructions)
for network recovery.
The service diagnosis information can be modeled as technology-
independent Remote Procedure Call (RPC) operations for OAM protocols
and technology-independent abstraction of key OAM constructs for OAM
protocols [RFC8531][RFC8533]. These models can be used to provide
consistent configuration, reporting, and presentation for the OAM
mechanisms used to manage the network.
Refer to Section 4.2.4 for the device-specific side.
4.1.6. Service Decommission
Service decommission allows a customer to stop the service by
removing the service from active status, thus releasing the network
resources that were allocated to the service. Customers can also use
the service model to withdraw the subscription to a service.
4.2. Service Fulfillment Management Procedure
4.2.1. Intended Configuration Provision
Intended configuration at the device level is derived from network
models at the network level or service models at the service level
and represents the configuration that the system attempts to apply.
Take L3SM as a service model example to deliver an L3VPN service;
there is a need to map the L3VPN service view defined in the service
model into a detailed intended configuration view defined by specific
configuration models for network elements. The configuration
information includes:
* Virtual Routing and Forwarding (VRF) definition, including VPN
policy expression
* Physical Interface(s)
* IP layer (IPv4, IPv6)
* QoS features such as classification, profiles, etc.
* Routing protocols: support of configuration of all protocols
listed in a service request, as well as routing policies
associated with those protocols
* Multicast support
* Address sharing
* Security (e.g., access control, authentication, encryption)
These specific configuration models can be used to configure Provider
Edge (PE) and Customer Edge (CE) devices within a site, e.g., a BGP
policy model can be used to establish VPN membership between sites
and VPN service topology.
Note that in networks with legacy devices (that support proprietary
modules or do not support YANG at all), an adaptation layer is likely
to be required at the network level so that these devices can be
involved in the delivery of the network services.
This interface is also used to handle service withdrawal
(Section 4.1.6).
4.2.2. Configuration Validation
Configuration validation is used to validate intended configuration
and ensure the configuration takes effect.
For example, if a customer creates an interface "eth-0/0/0" but the
interface does not physically exist at this point, then configuration
data appears in the <intended> status but does not appear in the
<operational> datastore. More details about <intended> and
<operational> datastores can be found in Section 5.1 of [RFC8342].
4.2.3. Performance Monitoring
When a configuration is in effect in a device, the <operational>
datastore holds the complete operational state of the device,
including learned, system, default configuration, and system state.
However, the configurations and state of a particular device do not
have visibility on the whole network, nor can they show how packets
are going to be forwarded through the entire network. Therefore, it
becomes more difficult to operate the entire network without
understanding the current status of the network.
The management system should subscribe to updates of a YANG datastore
in all the network devices for performance monitoring purposes and
build a full topological visibility of the network by aggregating
(and filtering) these operational states from different sources.
4.2.4. Fault Diagnostic
When configuration is in effect in a device, some devices may be
misconfigured (e.g., device links are not consistent in both sides of
the network connection) or network resources might be misallocated.
Therefore, services may be negatively affected without knowing the
root cause in the network.
Technology-dependent nodes and RPC commands are defined in
technology-specific YANG data models, which can use and extend the
base model described in Section 4.1.5 to deal with these issues.
These RPC commands received in the technology-dependent node can be
used to trigger technology-specific OAM message exchanges for fault
verification and fault isolation. For example, Transparent
Interconnection of Lots of Links (TRILL) Multi-destination Tree
Verification (MTV) RPC command [TRILL-YANG-OAM] can be used to
trigger Multi-Destination Tree Verification Messages (MTVMs) defined
in [RFC7455] to verify TRILL distribution tree integrity.
4.3. Multi-layer/Multi-domain Service Mapping
Multi-layer/Multi-domain Service Mapping allows the mapping of an
end-to-end abstract view of the service segmented at different layers
and/or different network domains into domain-specific views.
One example is to map service parameters in the L3SM into
configuration parameters such as Route Distinguisher (RD), Route
Target (RT), and VRF in the L3VPN Network Model (L3NM).
Another example is to map service parameters in the L3SM into Traffic
Engineered (TE) tunnel parameters (e.g., Tunnel ID) in TE model and
Virtual Network (VN) parameters (e.g., Access Point (AP) list and VN
members) in the YANG data model for VN operation [ACTN-VN-YANG].
4.4. Service Decomposition
Service Decomposition allows to decompose service models at the
service level or network models at the network level into a set of
device models at the device level. These device models may be tied
to specific device types or classified into a collection of related
YANG modules based on service types and features offered, and they
may load at the implementation time before configuration is loaded
and validated.
5. YANG Data Model Integration Examples
The following subsections provide some YANG data model integration
examples.
5.1. L2VPN/L3VPN Service Delivery
In reference to Figure 5, the following steps are performed to
deliver the L3VPN service within the network management automation
architecture defined in Section 4:
1. The Customer requests to create two sites (as per Service
Creation in Section 4.1.2) relying upon L3SM with each site
having one network access connectivity, for example:
* Site A: network-access A, link-capacity = 20 Mbps, class
"foo", guaranteed-capacity-percent = 10, average-one-way-delay
= 70 ms.
* Site B: network-access B, link-capacity = 30 Mbps, class
"foo1", guaranteed-capacity-percent = 15, average-one-way-
delay = 60 ms.
2. The Orchestrator extracts the service parameters from the L3SM.
Then, it uses them as input to the Service Mapping in Section 4.3
to translate them into orchestrated configuration parameters
(e.g., RD, RT, and VRF) that are part of the L3NM specified in
[OPSAWG-L3SM-L3NM].
3. The Controller takes the orchestrated configuration parameters in
the L3NM and translates them into an orchestrated (Service
Decomposition in Section 4.4) configuration of network elements
that are part of, e.g., BGP, QoS, Network Instance, IP
management, and interface models.
[UNI-TOPOLOGY] can be used for representing, managing, and
controlling the User Network Interface (UNI) topology.
L3SM |
Service |
Model |
+------------------------+------------------------+
| +--------V--------+ |
| | Service Mapping | |
| +--------+--------+ |
| Orchestrator | |
+------------------------+------------------------+
L3NM | ^ UNI Topology Model
Network | |
Model | |
+------------------------+------------------------+
| +-----------V-----------+ |
| | Service Decomposition | |
| +--++---------------++--+ |
| || || |
| Controller || || |
+---------------++---------------++---------------+
|| ||
|| BGP, ||
|| QoS, ||
|| Interface, ||
+------------+| NI, |+------------+
| | IP | |
+--+--+ +--+--+ +--+--+ +--+--+
| CE1 +-------+ PE1 | | PE2 +-------+ CE2 |
+-----+ +-----+ +-----+ +-----+
Figure 5: L3VPN Service Delivery Example (Current)
L3NM inherits some of the data elements from the L3SM. Nevertheless,
the L3NM as designed in [OPSAWG-L3SM-L3NM] does not expose some
information to the above layer such as the capabilities of an
underlying network (which can be used to drive service order
handling) or notifications (to notify subscribers about specific
events or degradations as per agreed SLAs). Some of this information
can be provided using, e.g., [OPSAWG-YANG-VPN]. A target overall
model is depicted in Figure 6.
L3SM | ^
Service | | Notifications
Model | |
+------------------------+------------------------+
| +--------V--------+ |
| | Service Mapping | |
| +--------+--------+ |
| Orchestrator | |
+------------------------+------------------------+
L3NM | ^ UNI Topology Model
Network| | L3NM Notifications
Model | | L3NM Capabilities
+------------------------+------------------------+
| +-----------V-----------+ |
| | Service Decomposition | |
| +--++---------------++--+ |
| || || |
| Controller || || |
+---------------++---------------++---------------+
|| ||
|| BGP, ||
|| QoS, ||
|| Interface, ||
+------------+| NI, |+------------+
| | IP | |
+--+--+ +--+--+ +--+--+ +--+--+
| CE1 +-------+ PE1 | | PE2 +-------+ CE2 |
+-----+ +-----+ +-----+ +-----+
Figure 6: L3VPN Service Delivery Example (Target)
Note that a similar analysis can be performed for Layer 2 VPNs
(L2VPNs). An L2VPN Service Model (L2SM) is defined in [RFC8466],
while the YANG L2VPN Network Model (L2NM) is specified in
[OPSAWG-L2NM].
5.2. VN Life-Cycle Management
In reference to Figure 7, the following steps are performed to
deliver the VN service within the network management automation
architecture defined in Section 4:
1. A customer makes a request (Service Exposure in Section 4.1.1) to
create a VN. The association between the VN, APs, and VN members
is defined in the VN YANG model [ACTN-VN-YANG].
2. The Orchestrator creates the single abstract node topology based
on the information captured in the request.
3. The customer exchanges with the Orchestrator the connectivity
matrix on the abstract node topology and explicit paths using the
TE topology model [RFC8795]. This information can be used to
instantiate the VN and set up tunnels between source and
destination endpoints (Service Creation in Section 4.1.2).
4. In order to provide service assurance (Service Optimization in
Section 4.1.4), the telemetry model that augments the VN model
and corresponding TE tunnel model can be used by the Orchestrator
to subscribe to performance measurement data. The Controller
will then notify the Orchestrator with all the parameter changes
and network performance changes related to the VN topology and
the tunnels [TEAS-ACTN-PM].
|
VN |
Service |
Model |
+----------------------|--------------------------+
| Orchestrator | |
| +--------V--------+ |
| | Service Mapping | |
| +-----------------+ |
+----------------------+--------------------^-----+
TE | Telemetry |
Tunnel | Model |
Model | |
+----------------------V--------------------+-----+
| Controller |
| |
+-------------------------------------------------+
+-----+ +-----+ +-----+ +-----+
| CE1 +------+ PE1 | | PE2 +------+ CE2 |
+-----+ +-----+ +-----+ +-----+
Figure 7: A VN Service Delivery Example
5.3. Event-Based Telemetry in the Device Self Management
In reference to Figure 8, the following steps are performed to
monitor state changes of managed resources in a network device and
provide device self management within the network management
automation architecture defined in Section 4:
1. To control which state a network device should be in or is
allowed to be in at any given time, a set of conditions and
actions are defined and correlated with network events (e.g.,
allow the NETCONF server to send updates only when the value
exceeds a certain threshold for the first time, but not again
until the threshold is cleared), which constitute an Event
Condition Action (ECA) policy or an event-driven policy control
logic that can be executed on the device (e.g., [EVENT-YANG]).
2. To provide a rapid autonomic response that can exhibit self-
management properties, the Controller pushes the ECA policy to
the network device and delegates the network control logic to the
network device.
3. The network device uses the ECA model to subscribe to the event
source, e.g., an event stream or datastore state data conveyed to
the server via YANG-Push subscription [RFC8641], monitors state
parameters, and takes simple and instant actions when an
associated event condition on state parameters is met. ECA
notifications can be generated as the result of actions based on
event stream subscription or datastore subscription (model-driven
telemetry operation discussed in Section 4.2.3).
+----------------+
| <----+
| Controller | |
+-------+--------+ |
| |
| |
ECA | | ECA
Model | | Notification
| |
| |
+------------V-------------+-----+
|Device | |
| +-------+ +---------+ +--+---+ |
| | Event +-> Event +->Event | |
| | Source| |Condition| |Action| |
| +-------+ +---------+ +------+ |
+--------------------------------+
Figure 8: Event-Based Telemetry
6. Security Considerations
Many of the YANG modules cited in this document define schema for
data that is designed to be accessed via network management protocols
such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF
layer is the secure transport layer, and the mandatory-to-implement
secure transport is Secure Shell (SSH) [RFC6242]. The lowest
RESTCONF layer is HTTPS, and the mandatory-to-implement secure
transport is TLS [RFC8446].
The NETCONF access control model [RFC8341] provides the means to
restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.
Security considerations specific to each of the technologies and
protocols listed in the document are discussed in the specification
documents of each of these protocols.
In order to prevent leaking sensitive information and the "confused
deputy" problem [Hardy] in general, special care should be considered
when translating between the various layers in Section 4 or when
aggregating data retrieved from various sources. Authorization and
authentication checks should be performed to ensure that data is
available to an authorized entity. The network operator must enforce
means to protect privacy-related information included in customer-
facing models.
To detect misalignment between layers that might be induced by
misbehaving nodes, upper layers should continuously monitor the
perceived service (Section 4.1.4) and should proceed with checks to
assess that the provided service complies with the expected service
and that the data reported by an underlying layer is matching the
perceived service by the above layer. Such checks are the
responsibility of the service diagnosis (Section 4.1.5).
When a YANG module includes security-related parameters, it is
recommended to include the relevant information as part of the
service assurance to track the correct functioning of the security
mechanisms.
Additional considerations are discussed in the following subsections.
6.1. Service Level
A provider may rely on services offered by other providers to build
composite services. Appropriate mechanisms should be enabled by the
provider to monitor and detect a service disruption from these
providers. The characterization of a service disruption (including
mean time between failures and mean time to repair), the escalation
procedure, and penalties are usually documented in contractual
agreements (e.g., as described in Section 2.1 of [RFC4176]).
Misbehaving peer providers will thus be identified and appropriate
countermeasures will be applied.
The communication protocols that make use of a service model between
a customer and an operator are out of scope. Relevant security
considerations should be discussed in the specification documents of
these protocols.
6.2. Network Level
Security considerations specific to the network level are listed
below:
* A controller may create forwarding loops by misconfiguring the
underlying network nodes. It is recommended to proceed with tests
to check the status of forwarding paths regularly or whenever
changes are made to routing or forwarding processes. Such checks
may be triggered from the service level owing to the means
discussed in Section 4.1.5.
* Some service models may include a traffic isolation clause that is
passed down to the network level so that appropriate technology-
specific actions must be enforced at the underlying network (and
thus involved network devices) to avoid that such traffic is
accessible to non-authorized parties. In particular, network
models may indicate whether encryption is enabled and, if so,
expose a list of supported encryption schemes and parameters.
Refer, for example, to the encryption feature defined in
[OPSAWG-VPN-COMMON] and its use in [OPSAWG-L3SM-L3NM].
6.3. Device Level
Network operators should monitor and audit their networks to detect
misbehaving nodes and abnormal behaviors. For example, OAM, as
discussed in Section 4.1.5, can be used for that purpose.
Access to some data requires specific access privilege levels.
Devices must check that a required access privilege is provided
before granting access to specific data or performing specific
actions.
7. IANA Considerations
This document has no IANA actions.
8. References
8.1. Normative References
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[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/info/rfc8341>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
8.2. Informative References
[ACTN-VN-YANG]
Lee, Y., Dhody, D., Ceccarelli, D., Bryskin, I., and B. Y.
Yoon, "A YANG Data Model for VN Operation", Work in
Progress, Internet-Draft, draft-ietf-teas-actn-vn-yang-10,
2 November 2020, <https://tools.ietf.org/html/draft-ietf-
teas-actn-vn-yang-10>.
[BFD-YANG] Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S.,
and G. Mirsky, "YANG Data Model for Bidirectional
Forwarding Detection (BFD)", Work in Progress, Internet-
Draft, draft-ietf-bfd-yang-17, 2 August 2018,
<https://tools.ietf.org/html/draft-ietf-bfd-yang-17>.
[DOTS-DDOS]
Boucadair, M., Shallow, J., and T. Reddy.K, "Distributed
Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel Specification", Work in Progress, Internet-Draft,
draft-ietf-dots-rfc8782-bis-04, 3 December 2020,
<https://tools.ietf.org/html/draft-ietf-dots-rfc8782-bis-
04>.
[EVENT-YANG]
Wu, Q., Bryskin, I., Birkholz, H., Liu, X., and B. Claise,
"A YANG Data model for ECA Policy Management", Work in
Progress, Internet-Draft, draft-wwx-netmod-event-yang-10,
1 November 2020, <https://tools.ietf.org/html/draft-wwx-
netmod-event-yang-10>.
[EVPN-YANG]
Brissette, P., Shah, H., Hussain, I., Tiruveedhula, K.,
and J. Rabadan, "Yang Data Model for EVPN", Work in
Progress, Internet-Draft, draft-ietf-bess-evpn-yang-07, 11
March 2019, <https://tools.ietf.org/html/draft-ietf-bess-
evpn-yang-07>.
[Hardy] Hardy, N., "The Confused Deputy: (or why capabilities
might have been invented)", DOI 10.1145/54289.871709,
October 1988,
<https://dl.acm.org/doi/10.1145/54289.871709>.
[IDR-BGP-MODEL]
Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP
YANG Model for Service Provider Networks", Work in
Progress, Internet-Draft, draft-ietf-idr-bgp-model-10, 15
November 2020,
<https://tools.ietf.org/html/draft-ietf-idr-bgp-model-10>.
[IPPM] IANA, "Performance Metrics", March 2020,
<https://www.iana.org/assignments/performance-metrics/
performance-metrics.xhtml>.
[L2VPN-YANG]
Shah, H., Brissette, P., Chen, I., Hussain, I., Wen, B.,
and K. Tiruveedhula, "YANG Data Model for MPLS-based
L2VPN", Work in Progress, Internet-Draft, draft-ietf-bess-
l2vpn-yang-10, 2 July 2019, <https://tools.ietf.org/html/
draft-ietf-bess-l2vpn-yang-10>.
[L3VPN-YANG]
Jain, D., Patel, K., Brissette, P., Li, Z., Zhuang, S.,
Liu, X., Haas, J., Esale, S., and B. Wen, "Yang Data Model
for BGP/MPLS L3 VPNs", Work in Progress, Internet-Draft,
draft-ietf-bess-l3vpn-yang-04, 19 October 2018,
<https://tools.ietf.org/html/draft-ietf-bess-l3vpn-yang-
04>.
[METRIC-METHOD]
Morton, A., Geib, R., and L. Ciavattone, "Metrics and
Methods for One-way IP Capacity", Work in Progress,
Internet-Draft, draft-ietf-ippm-capacity-metric-method-04,
10 September 2020, <https://tools.ietf.org/html/draft-
ietf-ippm-capacity-metric-method-04>.
[MVPN-YANG]
Liu, Y., Guo, F., Litkowski, S., Liu, X., Kebler, R., and
M. Sivakumar, "Yang Data Model for Multicast in MPLS/BGP
IP VPNs", Work in Progress, Internet-Draft, draft-ietf-
bess-mvpn-yang-04, 30 June 2020,
<https://tools.ietf.org/html/draft-ietf-bess-mvpn-yang-
04>.
[NETMOD-MODEL]
Clarke, J. and B. Claise, "YANG module for
yangcatalog.org", Work in Progress, Internet-Draft, draft-
clacla-netmod-model-catalog-03, 3 April 2018,
<https://tools.ietf.org/html/draft-clacla-netmod-model-
catalog-03>.
[OPSAWG-L2NM]
Barguil, S., Dios, O. G. D., Boucadair, M., Munoz, L. A.,
Jalil, L., and J. Ma, "A Layer 2 VPN Network YANG Model",
Work in Progress, Internet-Draft, draft-ietf-opsawg-l2nm-
01, 2 November 2020,
<https://tools.ietf.org/html/draft-ietf-opsawg-l2nm-01>.
[OPSAWG-L3SM-L3NM]
Barguil, S., Dios, O. G. D., Boucadair, M., Munoz, L. A.,
and A. Aguado, "A Layer 3 VPN Network YANG Model", Work in
Progress, Internet-Draft, draft-ietf-opsawg-l3sm-l3nm-05,
16 October 2020, <https://tools.ietf.org/html/draft-ietf-
opsawg-l3sm-l3nm-05>.
[OPSAWG-VPN-COMMON]
Barguil, S., Dios, O. G. D., Boucadair, M., and Q. Wu, "A
Layer 2/3 VPN Common YANG Model", Work in Progress,
Internet-Draft, draft-ietf-opsawg-vpn-common-03, 14
January 2021, <https://tools.ietf.org/html/draft-ietf-
opsawg-vpn-common-03>.
[OPSAWG-YANG-VPN]
Wu, B., Wu, Q., Boucadair, M., Dios, O. G. D., Wen, B.,
Liu, C., and H. Xu, "A YANG Model for Network and VPN
Service Performance Monitoring", Work in Progress,
Internet-Draft, draft-www-opsawg-yang-vpn-service-pm-03,
21 January 2021, <https://tools.ietf.org/html/draft-www-
opsawg-yang-vpn-service-pm-03>.
[PIM-YANG] Liu, X., McAllister, P., Peter, A., Sivakumar, M., Liu,
Y., and F. Hu, "A YANG Data Model for Protocol Independent
Multicast (PIM)", Work in Progress, Internet-Draft, draft-
ietf-pim-yang-17, 19 May 2018,
<https://tools.ietf.org/html/draft-ietf-pim-yang-17>.
[QOS-MODEL]
Choudhary, A., Jethanandani, M., Strahle, N., Aries, E.,
and I. Chen, "YANG Model for QoS", Work in Progress,
Internet-Draft, draft-ietf-rtgwg-qos-model-02, 9 July
2020, <https://tools.ietf.org/html/draft-ietf-rtgwg-qos-
model-02>.
[RFC4176] El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan, K.,
and A. Gonguet, "Framework for Layer 3 Virtual Private
Networks (L3VPN) Operations and Management", RFC 4176,
DOI 10.17487/RFC4176, October 2005,
<https://www.rfc-editor.org/info/rfc4176>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer
2 Virtual Private Networks (L2VPNs)", RFC 4664,
DOI 10.17487/RFC4664, September 2006,
<https://www.rfc-editor.org/info/rfc4664>.
[RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
LAN Service (VPLS) Using BGP for Auto-Discovery and
Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
<https://www.rfc-editor.org/info/rfc4761>.
[RFC4762] Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
LAN Service (VPLS) Using Label Distribution Protocol (LDP)
Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
<https://www.rfc-editor.org/info/rfc4762>.
[RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity",
RFC 5136, DOI 10.17487/RFC5136, February 2008,
<https://www.rfc-editor.org/info/rfc5136>.
[RFC5486] Malas, D., Ed. and D. Meyer, Ed., "Session Peering for
Multimedia Interconnect (SPEERMINT) Terminology",
RFC 5486, DOI 10.17487/RFC5486, March 2009,
<https://www.rfc-editor.org/info/rfc5486>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC6406] Malas, D., Ed. and J. Livingood, Ed., "Session PEERing for
Multimedia INTerconnect (SPEERMINT) Architecture",
RFC 6406, DOI 10.17487/RFC6406, November 2011,
<https://www.rfc-editor.org/info/rfc6406>.
[RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
<https://www.rfc-editor.org/info/rfc7149>.
[RFC7224] Bjorklund, M., "IANA Interface Type YANG Module",
RFC 7224, DOI 10.17487/RFC7224, May 2014,
<https://www.rfc-editor.org/info/rfc7224>.
[RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y.
Weingarten, "An Overview of Operations, Administration,
and Maintenance (OAM) Tools", RFC 7276,
DOI 10.17487/RFC7276, June 2014,
<https://www.rfc-editor.org/info/rfc7276>.
[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP
Connectivity Provisioning Profile (CPP)", RFC 7297,
DOI 10.17487/RFC7297, July 2014,
<https://www.rfc-editor.org/info/rfc7297>.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC7317, August
2014, <https://www.rfc-editor.org/info/rfc7317>.
[RFC7455] Senevirathne, T., Finn, N., Salam, S., Kumar, D., Eastlake
3rd, D., Aldrin, S., and Y. Li, "Transparent
Interconnection of Lots of Links (TRILL): Fault
Management", RFC 7455, DOI 10.17487/RFC7455, March 2015,
<https://www.rfc-editor.org/info/rfc7455>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
[RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Delay Metric for IP Performance Metrics
(IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January
2016, <https://www.rfc-editor.org/info/rfc7679>.
[RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton,
Ed., "A One-Way Loss Metric for IP Performance Metrics
(IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January
2016, <https://www.rfc-editor.org/info/rfc7680>.
[RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
Maintenance Using the Label Distribution Protocol (LDP)",
STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
<https://www.rfc-editor.org/info/rfc8077>.
[RFC8194] Schoenwaelder, J. and V. Bajpai, "A YANG Data Model for
LMAP Measurement Agents", RFC 8194, DOI 10.17487/RFC8194,
August 2017, <https://www.rfc-editor.org/info/rfc8194>.
[RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module
Classification", RFC 8199, DOI 10.17487/RFC8199, July
2017, <https://www.rfc-editor.org/info/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/info/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/info/rfc8309>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/info/rfc8343>.
[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/info/rfc8345>.
[RFC8346] Clemm, A., Medved, J., Varga, R., Liu, X.,
Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346,
March 2018, <https://www.rfc-editor.org/info/rfc8346>.
[RFC8348] Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A
YANG Data Model for Hardware Management", RFC 8348,
DOI 10.17487/RFC8348, March 2018,
<https://www.rfc-editor.org/info/rfc8348>.
[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>.
[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/info/rfc8466>.
[RFC8512] Boucadair, M., Ed., Sivakumar, S., Jacquenet, C.,
Vinapamula, S., and Q. Wu, "A YANG Module for Network
Address Translation (NAT) and Network Prefix Translation
(NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019,
<https://www.rfc-editor.org/info/rfc8512>.
[RFC8513] Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG
Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513,
DOI 10.17487/RFC8513, January 2019,
<https://www.rfc-editor.org/info/rfc8513>.
[RFC8519] Jethanandani, M., Agarwal, S., Huang, L., and D. Blair,
"YANG Data Model for Network Access Control Lists (ACLs)",
RFC 8519, DOI 10.17487/RFC8519, March 2019,
<https://www.rfc-editor.org/info/rfc8519>.
[RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
and R. Wilton, "YANG Library", RFC 8525,
DOI 10.17487/RFC8525, March 2019,
<https://www.rfc-editor.org/info/rfc8525>.
[RFC8528] Bjorklund, M. and L. Lhotka, "YANG Schema Mount",
RFC 8528, DOI 10.17487/RFC8528, March 2019,
<https://www.rfc-editor.org/info/rfc8528>.
[RFC8529] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
Liu, "YANG Data Model for Network Instances", RFC 8529,
DOI 10.17487/RFC8529, March 2019,
<https://www.rfc-editor.org/info/rfc8529>.
[RFC8530] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X.
Liu, "YANG Model for Logical Network Elements", RFC 8530,
DOI 10.17487/RFC8530, March 2019,
<https://www.rfc-editor.org/info/rfc8530>.
[RFC8531] Kumar, D., Wu, Q., and Z. Wang, "Generic YANG Data Model
for Connection-Oriented Operations, Administration, and
Maintenance (OAM) Protocols", RFC 8531,
DOI 10.17487/RFC8531, April 2019,
<https://www.rfc-editor.org/info/rfc8531>.
[RFC8532] Kumar, D., Wang, Z., Wu, Q., Ed., Rahman, R., and S.
Raghavan, "Generic YANG Data Model for the Management of
Operations, Administration, and Maintenance (OAM)
Protocols That Use Connectionless Communications",
RFC 8532, DOI 10.17487/RFC8532, April 2019,
<https://www.rfc-editor.org/info/rfc8532>.
[RFC8533] Kumar, D., Wang, M., Wu, Q., Ed., Rahman, R., and S.
Raghavan, "A YANG Data Model for Retrieval Methods for the
Management of Operations, Administration, and Maintenance
(OAM) Protocols That Use Connectionless Communications",
RFC 8533, DOI 10.17487/RFC8533, April 2019,
<https://www.rfc-editor.org/info/rfc8533>.
[RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm
Management", RFC 8632, DOI 10.17487/RFC8632, September
2019, <https://www.rfc-editor.org/info/rfc8632>.
[RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
September 2019, <https://www.rfc-editor.org/info/rfc8641>.
[RFC8652] Liu, X., Guo, F., Sivakumar, M., McAllister, P., and A.
Peter, "A YANG Data Model for the Internet Group
Management Protocol (IGMP) and Multicast Listener
Discovery (MLD)", RFC 8652, DOI 10.17487/RFC8652, November
2019, <https://www.rfc-editor.org/info/rfc8652>.
[RFC8675] Boucadair, M., Farrer, I., and R. Asati, "A YANG Data
Model for Tunnel Interface Types", RFC 8675,
DOI 10.17487/RFC8675, November 2019,
<https://www.rfc-editor.org/info/rfc8675>.
[RFC8676] Farrer, I., Ed. and M. Boucadair, Ed., "YANG Modules for
IPv4-in-IPv6 Address plus Port (A+P) Softwires", RFC 8676,
DOI 10.17487/RFC8676, November 2019,
<https://www.rfc-editor.org/info/rfc8676>.
[RFC8783] Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed
Denial-of-Service Open Threat Signaling (DOTS) Data
Channel Specification", RFC 8783, DOI 10.17487/RFC8783,
May 2020, <https://www.rfc-editor.org/info/rfc8783>.
[RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
June 2020, <https://www.rfc-editor.org/info/rfc8791>.
[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/info/rfc8795>.
[RFC8819] Hopps, C., Berger, L., and D. Bogdanovic, "YANG Module
Tags", RFC 8819, DOI 10.17487/RFC8819, January 2021,
<https://www.rfc-editor.org/info/rfc8819>.
[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/info/rfc8944>.
[RFC8960] Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A
YANG Data Model for MPLS Base", RFC 8960,
DOI 10.17487/RFC8960, December 2020,
<https://www.rfc-editor.org/info/rfc8960>.
[RTGWG-POLICY]
Qu, Y., Tantsura, J., Lindem, A., and X. Liu, "A YANG Data
Model for Routing Policy", Work in Progress, Internet-
Draft, draft-ietf-rtgwg-policy-model-27, 10 January 2021,
<https://tools.ietf.org/html/draft-ietf-rtgwg-policy-
model-27>.
[SNOOPING-YANG]
Zhao, H., Liu, X., Liu, Y., Sivakumar, M., and A. Peter,
"A Yang Data Model for IGMP and MLD Snooping", Work in
Progress, Internet-Draft, draft-ietf-pim-igmp-mld-
snooping-yang-18, 14 August 2020,
<https://tools.ietf.org/html/draft-ietf-pim-igmp-mld-
snooping-yang-18>.
[SPRING-SR-YANG]
Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J.
Tantsura, "YANG Data Model for Segment Routing", Work in
Progress, Internet-Draft, draft-ietf-spring-sr-yang-29, 8
December 2020, <https://tools.ietf.org/html/draft-ietf-
spring-sr-yang-29>.
[STAMP-YANG]
Mirsky, G., Min, X., and W. S. Luo, "Simple Two-way Active
Measurement Protocol (STAMP) Data Model", Work in
Progress, Internet-Draft, draft-ietf-ippm-stamp-yang-06, 7
October 2020, <https://tools.ietf.org/html/draft-ietf-
ippm-stamp-yang-06>.
[TEAS-ACTN-PM]
Lee, Y., Dhody, D., Karunanithi, S., Vilalta, R., King,
D., and D. Ceccarelli, "YANG models for VN/TE Performance
Monitoring Telemetry and Scaling Intent Autonomics", Work
in Progress, Internet-Draft, draft-ietf-teas-actn-pm-
telemetry-autonomics-04, 2 November 2020,
<https://tools.ietf.org/html/draft-ietf-teas-actn-pm-
telemetry-autonomics-04>.
[TEAS-YANG-PATH-COMP]
Busi, I., Belotti, S., Lopez, V., Sharma, A., and Y. Shi,
"Yang model for requesting Path Computation", Work in
Progress, Internet-Draft, draft-ietf-teas-yang-path-
computation-11, 16 November 2020,
<https://tools.ietf.org/html/draft-ietf-teas-yang-path-
computation-11>.
[TEAS-YANG-RSVP]
Beeram, V. P., Saad, T., Gandhi, R., Liu, X., Bryskin, I.,
and H. Shah, "A YANG Data Model for RSVP-TE Protocol",
Work in Progress, Internet-Draft, draft-ietf-teas-yang-
rsvp-te-08, 9 March 2020, <https://tools.ietf.org/html/
draft-ietf-teas-yang-rsvp-te-08>.
[TEAS-YANG-TE]
Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I.
Bryskin, "A YANG Data Model for Traffic Engineering
Tunnels, Label Switched Paths and Interfaces", Work in
Progress, Internet-Draft, draft-ietf-teas-yang-te-25, 27
July 2020,
<https://tools.ietf.org/html/draft-ietf-teas-yang-te-25>.
[TRILL-YANG-OAM]
Kumar, D., Senevirathne, T., Finn, N., Salam, S., Xia, L.,
and W. Hao, "YANG Data Model for TRILL Operations,
Administration, and Maintenance (OAM)", Work in Progress,
Internet-Draft, draft-ietf-trill-yang-oam-05, 31 March
2017, <https://tools.ietf.org/html/draft-ietf-trill-yang-
oam-05>.
[TWAMP-DATA-MODEL]
Civil, R., Morton, A., Rahman, R., Jethanandani, M., and
K. Pentikousis, "Two-Way Active Measurement Protocol
(TWAMP) Data Model", Work in Progress, Internet-Draft,
draft-ietf-ippm-twamp-yang-13, 2 July 2018,
<https://tools.ietf.org/html/draft-ietf-ippm-twamp-yang-
13>.
[UNI-TOPOLOGY]
Dios, O. G. D., Barguil, S., Wu, Q., and M. Boucadair, "A
YANG Model for User-Network Interface (UNI) Topologies",
Work in Progress, Internet-Draft, draft-ogondio-opsawg-
uni-topology-01, 2 April 2020,
<https://tools.ietf.org/html/draft-ogondio-opsawg-uni-
topology-01>.
Appendix A. Layered YANG Module Examples Overview
This appendix lists a set of YANG data models that can be used for
the delivery of connectivity services. These models can be
classified as service, network, or device models.
It is not the intent of this appendix to provide an inventory of
tools and mechanisms used in specific network and service management
domains; such inventory can be found in documents such as [RFC7276].
The reader may refer to the YANG Catalog
(<https://www.yangcatalog.org>) or the public Github YANG repository
(<https://github.com/YangModels/yang>) to query existing YANG models.
The YANG Catalog includes some metadata to indicate the module type
('module-classification') [NETMOD-MODEL]. Note that the mechanism
defined in [RFC8819] allows to associate tags with YANG modules in
order to help classifying the modules.
A.1. Service Models: Definition and Samples
As described in [RFC8309], the service is "some form of connectivity
between customer sites and the Internet or between customer sites
across the network operator's network and across the Internet". More
concretely, an IP connectivity service can be defined as the IP
transfer capability characterized by a (Source Nets, Destination
Nets, Guarantees, Scope) tuple where "Source Nets" is a group of
unicast IP addresses, "Destination Nets" is a group of IP unicast
and/or multicast addresses, and "Guarantees" reflects the guarantees
(expressed, for example, in terms of QoS, performance, and
availability) to properly forward traffic to the said "Destination"
[RFC7297]. The "Scope" denotes the network perimeter (e.g., between
Provider Edge (PE) routers or Customer Nodes) where the said
guarantees need to be provided.
For example:
* The L3SM [RFC8299] defines the L3VPN service ordered by a customer
from a network operator.
* The L2SM [RFC8466] defines the L2VPN service ordered by a customer
from a network operator.
* The Virtual Network (VN) model [ACTN-VN-YANG] provides a YANG data
model applicable to any mode of VN operation.
L2SM and L3SM are customer service models as per [RFC8309].
A.2. Schema Mount
Modularity and extensibility were among the leading design principles
of the YANG data modeling language. As a result, the same YANG
module can be combined with various sets of other modules and thus
form a data model that is tailored to meet the requirements of a
specific use case. [RFC8528] defines a mechanism, denoted "schema
mount", that allows for mounting one data model consisting of any
number of YANG modules at a specified location of another (parent)
schema.
A.3. Network Models: Samples
L2NM [OPSAWG-L2NM] and L3NM [OPSAWG-L3SM-L3NM] are examples of YANG
network models.
Figure 9 depicts a set of additional network models such as topology
and tunnel models:
+-------------------------------+-------------------------------+
| Topology YANG modules | Tunnel YANG modules |
+-------------------------------+-------------------------------+
| +------------------+ | |
| |Network Topologies| | +------+ +-----------+ |
| | Model | | |Other | | TE Tunnel | |
| +--------+---------+ | |Tunnel| +----+------+ |
| | +---------+ | +------+ | |
| +---+Service | | +----------+---------+ |
| | |Topology | | | | | |
| | +---------+ | | | | |
| | +---------+ |+----+---+ +----+---+ +---+---+|
| +---+Layer 3 | ||MPLS-TE | |RSVP-TE | | SR-TE ||
| | |Topology | || Tunnel | | Tunnel | |Tunnel ||
| | +---------+ |+--------+ +--------+ +-------+|
| | +---------+ | |
| +---+TE | | |
| | |Topology | | |
| | +---------+ | |
| | +---------+ | |
| +---+Layer 3 | | |
| |Topology | | |
| +---------+ | |
+-------------------------------+-------------------------------+
Figure 9: Sample Resource-Facing Network Models
Examples of topology YANG modules are listed below:
Network Topologies Model:
[RFC8345] defines a base model for network topology and
inventories. Network topology data includes link, node, and
terminate-point resources.
TE Topology Model:
[RFC8795] defines a YANG data model for representing and
manipulating TE topologies.
This module is extended from the network topology model defined in
[RFC8345] and includes content related to TE topologies. This
model contains technology-agnostic TE topology building blocks
that can be augmented and used by other technology-specific TE
topology models.
Layer 3 Topology Model:
[RFC8346] defines a YANG data model for representing and
manipulating Layer 3 topologies. This model is extended from the
network topology model defined in [RFC8345] and includes content
related to Layer 3 topology specifics.
Layer 2 Topology Model:
[RFC8944] defines a YANG data model for representing and
manipulating Layer 2 topologies. This model is extended from the
network topology model defined in [RFC8345] and includes content
related to Layer 2 topology specifics.
Examples of tunnel YANG modules are provided below:
Tunnel Identities:
[RFC8675] defines a collection of YANG identities used as
interface types for tunnel interfaces.
TE Tunnel Model:
[TEAS-YANG-TE] defines a YANG module for the configuration and
management of TE interfaces, tunnels, and LSPs.
Segment Routing (SR) Traffic Engineering (TE) Tunnel Model:
[TEAS-YANG-TE] augments the TE generic and MPLS-TE model(s) and
defines a YANG module for SR-TE-specific data.
MPLS-TE Model:
[TEAS-YANG-TE] augments the TE generic and MPLS-TE model(s) and
defines a YANG module for MPLS-TE configurations, state, RPC, and
notifications.
RSVP-TE MPLS Model:
[TEAS-YANG-RSVP] augments the RSVP-TE generic module with
parameters to configure and manage signaling of MPLS RSVP-TE LSPs.
Other sample network models are listed hereafter:
Path Computation API Model:
[TEAS-YANG-PATH-COMP] defines a YANG module for a stateless RPC
that complements the stateful solution defined in [TEAS-YANG-TE].
OAM Models (including Fault Management (FM) and Performance
Monitoring):
[RFC8532] defines a base YANG module for the management of OAM
protocols that use Connectionless Communications. [RFC8533]
defines a retrieval method YANG module for connectionless OAM
protocols. [RFC8531] defines a base YANG module for connection-
oriented OAM protocols. These three models are intended to
provide consistent reporting, configuration, and representation
for connectionless OAM and connection-oriented OAM separately.
Alarm monitoring is a fundamental part of monitoring the network.
Raw alarms from devices do not always tell the status of the
network services or necessarily point to the root cause.
[RFC8632] defines a YANG module for alarm management.
A.4. Device Models: Samples
Network Element models (listed in Figure 10) are used to describe how
a service can be implemented by activating and tweaking a set of
functions (enabled in one or multiple devices, or hosted in cloud
infrastructures) that are involved in the service delivery. For
example, the L3VPN service will involve many PEs and require
manipulating the following modules:
* Routing management [RFC8349]
* BGP [IDR-BGP-MODEL]
* PIM [PIM-YANG]
* NAT management [RFC8512]
* QoS management [QOS-MODEL]
* ACLs [RFC8519]
Figure 10 uses IETF-defined data models as an example.
+------------------------+
+-+ Device Model |
| +------------------------+
| +------------------------+
+---------------+ | | Logical Network |
| | +-+ Element Model |
| Architecture | | +------------------------+
| | | +------------------------+
+-------+-------+ +-+ Network Instance Model |
| | +------------------------+
| | +------------------------+
| +-+ Routing Type Model |
| +------------------------+
+-------+----------+----+------+------------+-----------+------+
| | | | | | |
+-+-+ +---+---+ +----+----+ +--+--+ +----+----+ +--+--+ |
|ACL| |Routing| |Transport| | OAM | |Multicast| | PM | Others
+---+ +-+-----+ +----+----+ +--+--+ +-----+---+ +--+--+
| +-------+ | +------+ | +--------+ | +-----+ | +-----+
+-+Core | +-+ MPLS | +-+ BFD | +-+IGMP | +-+TWAMP|
| |Routing| | | Base | | +--------+ | |/MLD | | +-----+
| +-------+ | +------+ | +--------+ | +-----+ | +-----+
| +-------+ | +------+ +-+LSP Ping| | +-----+ +-+OWAMP|
+-+ BGP | +-+ MPLS | | +--------+ +-+ PIM | | +-----+
| +-------+ | | LDP | | +--------+ | +-----+ | +-----+
| +-------+ | +------+ +-+MPLS-TP | | +-----+ +-+LMAP |
+-+ ISIS | | +------+ +--------+ +-+ MVPN| +-----+
| +-------+ +-+ MPLS | +-----+
| +-------+ |Static|
+-+ OSPF | +------+
| +-------+
| +-------+
+-+ RIP |
| +-------+
| +-------+
+-+ VRRP |
| +-------+
| +-------+
+-+SR/SRv6|
| +-------+
| +-------+
+-+ISIS-SR|
| +-------+
| +-------+
+-+OSPF-SR|
+-------+
Figure 10: Network Element Models Overview
A.4.1. Model Composition
Logical Network Element Model:
[RFC8530] defines a logical network element model that can be used
to manage the logical resource partitioning that may be present on
a network device. Examples of common industry terms for logical
resource partitioning are Logical Systems or Logical Routers.
Network Instance Model:
[RFC8529] defines a network instance module. This module can be
used to manage the virtual resource partitioning that may be
present on a network device. Examples of common industry terms
for virtual resource partitioning are VRF instances and Virtual
Switch Instances (VSIs).
A.4.2. Device Management
The following list enumerates some YANG modules that can be used for
device management:
* [RFC8348] defines a YANG module for the management of hardware.
* [RFC7317] defines the "ietf-system" YANG module that provides many
features such as the configuration and the monitoring of system or
system control operations (e.g., shutdown, restart, and setting
time) identification.
* [RFC8341] defines a network configuration access control YANG
module.
A.4.3. Interface Management
The following provides some YANG modules that can be used for
interface management:
* [RFC7224] defines a YANG module for interface type definitions.
* [RFC8343] defines a YANG module for the management of network
interfaces.
A.4.4. Some Device Model Examples
The following provides an overview of some device models that can be
used within a network. This list is not comprehensive.
L2VPN:
[L2VPN-YANG] defines a YANG module for MPLS-based Layer 2 VPN
services (L2VPN) [RFC4664] and includes switching between the
local attachment circuits. The L2VPN model covers point-to-point
Virtual Private Wire Service (VPWS) and Multipoint Virtual Private
LAN Service (VPLS). These services use signaling of Pseudowires
across MPLS networks using LDP [RFC8077][RFC4762] or BGP
[RFC4761].
EVPN:
[EVPN-YANG] defines a YANG module for Ethernet VPN services. The
model is agnostic of the underlay. It applies to MPLS as well as
to Virtual eXtensible Local Area Network (VxLAN) encapsulation.
The module is also agnostic to the services, including E-LAN,
E-LINE, and E-TREE services.
L3VPN:
[L3VPN-YANG] defines a YANG module that can be used to configure
and manage BGP L3VPNs [RFC4364]. It contains VRF-specific
parameters as well as BGP-specific parameters applicable for
L3VPNs.
Core Routing:
[RFC8349] defines the core routing YANG data model, which is
intended as a basis for future data model development covering
more-sophisticated routing systems. It is expected that other
Routing technology YANG modules (e.g., VRRP, RIP, ISIS, or OSPF
models) will augment the Core Routing base YANG module.
MPLS:
[RFC8960] defines a base model for MPLS that serves as a base
framework for configuring and managing an MPLS switching
subsystem. It is expected that other MPLS technology YANG modules
(e.g., MPLS LSP Static, LDP, or RSVP-TE models) will augment the
MPLS base YANG module.
BGP:
[IDR-BGP-MODEL] defines a YANG module for configuring and managing
BGP, including protocol, policy, and operational aspects based on
data center, carrier, and content provider operational
requirements.
Routing Policy:
[RTGWG-POLICY] defines a YANG module for configuring and managing
routing policies based on operational practice. The module
provides a generic policy framework that can be augmented with
protocol-specific policy configuration.
SR/SRv6:
[SPRING-SR-YANG] defines a YANG module for segment routing
configuration and operation.
BFD:
Bidirectional Forwarding Detection (BFD) [RFC5880] is a network
protocol that is used for liveness detection of arbitrary paths
between systems. [BFD-YANG] defines a YANG module that can be
used to configure and manage BFD.
Multicast:
[PIM-YANG] defines a YANG module that can be used to configure and
manage Protocol Independent Multicast (PIM) devices.
[RFC8652] defines a YANG module that can be used to configure and
manage Internet Group Management Protocol (IGMP) and Multicast
Listener Discovery (MLD) devices.
[SNOOPING-YANG] defines a YANG module that can be used to
configure and manage Internet Group Management Protocol (IGMP) and
Multicast Listener Discovery (MLD) snooping devices.
[MVPN-YANG] defines a YANG data model to configure and manage
Multicast in MPLS/BGP IP VPNs (MVPNs).
PM:
[TWAMP-DATA-MODEL] defines a YANG data model for client and server
implementations of the Two-Way Active Measurement Protocol
(TWAMP).
[STAMP-YANG] defines the data model for implementations of
Session-Sender and Session-Reflector for Simple Two-way Active
Measurement Protocol (STAMP) mode using YANG.
[RFC8194] defines a YANG data model for Large-Scale Measurement
Platforms (LMAPs).
ACL:
An Access Control List (ACL) is one of the basic elements used to
configure device-forwarding behavior. It is used in many
networking technologies such as Policy-Based Routing, firewalls,
etc. [RFC8519] describes a YANG data model of ACL basic building
blocks.
QoS:
[QOS-MODEL] describes a YANG module of Differentiated Services for
configuration and operations.
NAT:
For the sake of network automation and the need for programming
the Network Address Translation (NAT) function in particular, a
YANG data model for configuring and managing the NAT is essential.
[RFC8512] defines a YANG module for the NAT function covering a
variety of NAT flavors such as Network Address Translation from
IPv4 to IPv4 (NAT44), Network Address and Protocol Translation
from IPv6 Clients to IPv4 Servers (NAT64), customer-side
translator (CLAT), Stateless IP/ICMP Translation (SIIT), Explicit
Address Mappings (EAMs) for SIIT, IPv6-to-IPv6 Network Prefix
Translation (NPTv6), and Destination NAT.
[RFC8513] specifies a Dual-Stack Lite (DS-Lite) YANG module.
Stateless Address Sharing:
[RFC8676] specifies a YANG module for Address plus Port (A+P)
address sharing, including Lightweight 4over6, Mapping of Address
and Port with Encapsulation (MAP-E), and Mapping of Address and
Port using Translation (MAP-T) softwire mechanisms.
Acknowledgements
Thanks to Joe Clark, Greg Mirsky, Shunsuke Homma, Brian Carpenter,
Adrian Farrel, Christian Huitema, Tommy Pauly, Ines Robles, and
Olivier Augizeau for the review.
Many thanks to Robert Wilton for the detailed AD review.
Thanks to Éric Vyncke, Roman Danyliw, Erik Kline, and Benjamin Kaduk
for the IESG review.
Contributors
Christian Jacquenet
Orange
Rennes, 35000
France
Email: Christian.jacquenet@orange.com
Luis Miguel Contreras Murillo
Telefonica
Email: luismiguel.contrerasmurillo@telefonica.com
Oscar Gonzalez de Dios
Telefonica
Madrid
Spain
Email: oscar.gonzalezdedios@telefonica.com
Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com
Young Lee
Sung Kyun Kwan University
Email: younglee.tx@gmail.com
Authors' Addresses
Qin Wu (editor)
Huawei
101 Software Avenue
Yuhua District
Nanjing
Jiangsu, 210012
China
Email: bill.wu@huawei.com
Mohamed Boucadair (editor)
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Diego R. Lopez
Telefonica I+D
Spain
Email: diego.r.lopez@telefonica.com
Chongfeng Xie
China Telecom
Beijing
China
Email: xiechf@chinatelecom.cn
Liang Geng
China Mobile
Email: gengliang@chinamobile.com