Huawei

101 Software Avenue Yuhua District Nanjing Jiangsu 210012 China bill.wu@huawei.com

Orange

Rennes 35000 France mohamed.boucadair@orange.com

Telefonica I+D

Spain diego.r.lopez@telefonica.com

China Telecom

Beijing China xiechf@chinatelecom.cn

China Mobile

gengliang@chinamobile.com

OPS Area OPSAWG Model Driven YANG Data Model automation service delivery notification SDN 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 .

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 () 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

• .  Introduction
• .  Terminology and Abbreviations
  • .  Terminology
  • .  Abbreviations
• .  Architectural Concepts and Goals
  • .  Data Models: Layering and Representation
  • .  Automation of Service Delivery Procedures
  • .  Service Fulfillment Automation
  • .  YANG Module Integration
• .  Functional Blocks and Interactions
  • .  Service Life-Cycle Management Procedure
    • .  Service Exposure
    • .  Service Creation/Modification
    • .  Service Assurance
    • .  Service Optimization
    • .  Service Diagnosis
    • .  Service Decommission
  • .  Service Fulfillment Management Procedure
    • .  Intended Configuration Provision
    • .  Configuration Validation
    • .  Performance Monitoring
    • .  Fault Diagnostic
  • .  Multi-layer/Multi-domain Service Mapping
  • .  Service Decomposition
• .  YANG Data Model Integration Examples
  • .  L2VPN/L3VPN Service Delivery
  • .  VN Life-Cycle Management
  • .  Event-Based Telemetry in the Device Self Management
• .  Security Considerations
  • .  Service Level
  • .  Network Level
  • .  Device Level
• .  IANA Considerations
• .  References
  • .  Normative References
  • .  Informative References
• .  Layered YANG Module Examples Overview
  • .  Service Models: Definition and Samples
  • .  Schema Mount
  • .  Network Models: Samples
  • .  Device Models: Samples
    • .  Model Composition
    • .  Device Management
    • .  Interface Management
    • .  Some Device Model Examples
• Acknowledgements
• Contributors
• Authors' Addresses

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. 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 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 developers have taken both top-down and bottom-up approaches to develop modules 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 . 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 that can be manipulated by other protocols (e.g., ). This document describes an architectural framework for service and network management automation () 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 (). 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 (), but it does not claim nor aim to be exhaustive. lists some examples to illustrate the layered YANG modules view.

Terminology and Abbreviations

Terminology The following terms are defined in and 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 . 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 or the device configuration model discussed in . Device models are also used to refer to model a function embedded in a device (e.g., Network Address Translation (NAT) , Access Control Lists (ACLs) ).

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.

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

Architectural Concepts and Goals

Data Models: Layering and Representation As described in , 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) or One-Way Loss ; a summary of performance metrics maintained by IANA can be found in ,
• link capacity ,
• etc.

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) . 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 . This example follows the IP Connectivity Provisioning Profile template defined in .

An Example of Service Connectivity Components ,--,--,--. ,--,--,--. ,-' 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

In reference to , "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.

Sample Attributes Captured in a Service Model 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

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, ). Mechanisms such as the YANG library can be used to expose which YANG modules are supported by nodes in lower levels. illustrates the overall layering model. The reader may refer to 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.

Layering and Representation within a Network 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, ... | | +-----------------------+ | +-----------------------------------------------------------------+

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 . 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 ) 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 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 , does not preclude service models to be modeled using data modeling languages other than YANG.

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 . The service filtering request modeled using will be translated into device-specific filtering (e.g., ACLs defined in ) 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., ) 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).

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.

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 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 ). 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.

Functional Blocks and Interactions The architectural considerations described in lead to the life-cycle management architecture illustrated in and described in the following subsections.

Service and Network Life-Cycle Management +------------------+ ............... | | 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

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.

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.

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 .

Service Assurance The performance measurement telemetry () 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.

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.

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 . These models can be used to provide consistent configuration, reporting, and presentation for the OAM mechanisms used to manage the network. Refer to for the device-specific side.

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.

Service Fulfillment Management Procedure

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 ().

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 .

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.

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 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 can be used to trigger Multi-Destination Tree Verification Messages (MTVMs) defined in to verify TRILL distribution tree integrity.

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 .

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.

YANG Data Model Integration Examples The following subsections provide some YANG data model integration examples.

L2VPN/L3VPN Service Delivery In reference to , the following steps are performed to deliver the L3VPN service within the network management automation architecture defined in :

1. The Customer requests to create two sites (as per Service Creation in ) 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 to translate them into orchestrated configuration parameters (e.g., RD, RT, and VRF) that are part of the L3NM specified in .
3. The Controller takes the orchestrated configuration parameters in the L3NM and translates them into an orchestrated (Service Decomposition in ) configuration of network elements that are part of, e.g., BGP, QoS, Network Instance, IP management, and interface models.

can be used for representing, managing, and controlling the User Network Interface (UNI) topology.

L3VPN Service Delivery Example (Current) 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 | +-----+ +-----+ +-----+ +-----+

L3NM inherits some of the data elements from the L3SM. Nevertheless, the L3NM as designed in 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., . A target overall model is depicted in .

L3VPN Service Delivery Example (Target) 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 | +-----+ +-----+ +-----+ +-----+

Note that a similar analysis can be performed for Layer 2 VPNs (L2VPNs). An L2VPN Service Model (L2SM) is defined in , while the YANG L2VPN Network Model (L2NM) is specified in .

VN Life-Cycle Management In reference to , the following steps are performed to deliver the VN service within the network management automation architecture defined in :

1. A customer makes a request (Service Exposure in ) to create a VN. The association between the VN, APs, and VN members is defined in the VN YANG model .
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 . This information can be used to instantiate the VN and set up tunnels between source and destination endpoints (Service Creation in ).
4. In order to provide service assurance (Service Optimization in ), 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 .

A VN Service Delivery Example | VN | Service | Model | +----------------------|--------------------------+ | Orchestrator | | | +--------V--------+ | | | Service Mapping | | | +-----------------+ | +----------------------+--------------------^-----+ TE | Telemetry | Tunnel | Model | Model | | +----------------------V--------------------+-----+ | Controller | | | +-------------------------------------------------+ +-----+ +-----+ +-----+ +-----+ | CE1 +------+ PE1 | | PE2 +------+ CE2 | +-----+ +-----+ +-----+ +-----+

Event-Based Telemetry in the Device Self Management In reference to , 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 :

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., ).
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 , 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 ).

Event-Based Telemetry +----------------+ | <----+ | Controller | | +-------+--------+ | | | | | ECA | | ECA Model | | Notification | | | | +------------V-------------+-----+ |Device | | | +-------+ +---------+ +--+---+ | | | Event +-> Event +->Event | | | | Source| |Condition| |Action| | | +-------+ +---------+ +------+ | +--------------------------------+

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 or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The NETCONF access control model 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 in general, special care should be considered when translating between the various layers in 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 () 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 (). 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.

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 ). 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.

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 .
• 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 and its use in .

Device Level Network operators should monitor and audit their networks to detect misbehaving nodes and abnormal behaviors. For example, OAM, as discussed in , 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.

IANA Considerations This document has no IANA actions.

References Normative References The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes a method for invoking and running the Network Configuration Protocol (NETCONF) within a Secure Shell (SSH) session as an SSH subsystem. This document obsoletes RFC 4742. [STANDARDS-TRACK] YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model. This document obsoletes RFC 6536. This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. Informative References Samsung Electronics Huawei Technologies Ericsson Individual ETRI This document provides a YANG data model generally applicable to any mode of Virtual Network (VN) operation. Work in Progress Cisco Systems Huawei Technologies Xoriant Corporation Rtbrick ZTE Corporation This document defines a YANG data model that can be used to configure and manage Bidirectional Forwarding Detection (BFD). The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA). Work in Progress Orange McAfee, Inc. This document specifies the Distributed Denial-of-Service Open Threat Signaling (DOTS) signal channel, a protocol for signaling the need for protection against Distributed Denial-of-Service (DDoS) attacks to a server capable of enabling network traffic mitigation on behalf of the requesting client. A companion document defines the DOTS data channel, a separate reliable communication layer for DOTS management and configuration purposes. This document obsoletes RFC 8782. Work in Progress Huawei Individual Fraunhofer SIT Volta Networks Cisco This document defines a YANG data model for Event Condition Action (ECA) policy management. The ECA policy YANG module provides the ability to delegate some network management functions to the server which can take simple and instant action when a trigger condition on the system state is met. Work in Progress Cisco System Ciena Corporation Infinera Corporation Juniper Networks Nokia This document describes a YANG data model for Ethernet VPN services. The model is agnostic of the underlay. It apply to MPLS as well as to VxLAN encapsulation. The model is also agnostic of the services including E-LAN, E-LINE and E-TREE services. This document mainly focuses on EVPN and Ethernet-Segment instance framework. Work in Progress Kloud Services Arrcus Huawei Juniper Networks This document defines a YANG data model for configuring and managing BGP, including protocol, policy, and operational aspects, such as RIB, based on data center, carrier, and content provider operational requirements. Work in Progress IANA Ciena Corporation Cisco Systems The MITRE Corporation Infinera Corporation Comcast Juniper Networks This document describes a YANG data model for Layer 2 VPN (L2VPN) services over MPLS networks. These services include point-to-point Virtual Private Wire Service (VPWS) and multipoint Virtual Private LAN service (VPLS) that uses LDP and BGP signaled Pseudowires. It is expected that this model will be used by the management tools run by the network operators in order to manage and monitor the network resources that they use to deliver L2VPN services. This document also describes the YANG data model for the Pseudowires. The independent definition of the Pseudowires facilitates its use in Ethernet Segment and EVPN data models defined in separate document. Work in Progress Cisco Arrcus, Inc Cisco Huawei Technologies Huawei Technologies Jabil Juniper Networks Juniper Networks Comcast This document defines a YANG data model that can be used to configure and manage BGP Layer 3 VPNs. Work in Progress AT&T Labs Deutsche Telekom AT&T Labs This memo revisits the problem of Network Capacity metrics first examined in RFC 5136. The memo specifies a more practical Maximum IP-layer Capacity metric definition catering for measurement purposes, and outlines the corresponding methods of measurement. Work in Progress China Mobile Huawei Cisco Volta Networks Juniper Juniper This document defines a YANG data model that can be used to configure and manage multicast in MPLS/BGP IP VPNs. Work in Progress Cisco Systems, Inc. Cisco Systems, Inc. This document specifies a YANG module that contains metadata related to YANG modules and vendor implementations of those YANG modules. Work in Progress Telefonica Telefonica Orange Vodafone Verizon China Unicom This document defines a YANG Data model (called, L2NM) that can be used to manage the provisioning of Layer 2 VPN services within a Service Provider Network. This YANG module provides representation of the Layer 2 VPN Service from a network standpoint. The module is meant to be used by a Network Controller to derive the configuration information that will be sent to relevant network devices. The L2NM YANG Data model complements the Layer 2 Service Model (RFC8466) by providing a network-centric view of the service that is internal to a Service Provider. Work in Progress Telefonica Telefonica Orange Vodafone Nokia This document defines a L3VPN Network YANG Model (L3NM) that can be used to manage the provisioning of Layer 3 Virtual Private Network (VPN) services within a Service Provider's network. The model provides a network-centric view of L3VPN services. L3NM is meant to be used by a Network Controller to derive the configuration information that will be sent to relevant network devices. The model can also facilitate the communication between a service orchestrator and a network controller/orchestrator. Work in Progress Telefonica Telefonica Orange Huawei This document defines a common YANG module that is meant to be reused by various VPN-related modules such as Layer 3 VPN and Layer 2 VPN network models. Editorial Note (To be removed by RFC Editor) Please update these statements within the document with the RFC number to be assigned to this document: o "This version of this YANG module is part of RFC XXXX;" o "RFC XXXX: A Layer 2/3 VPN Common YANG Model"; o reference: RFC XXXX Also, please update the "revision" date of the YANG module. Work in Progress Huawei Huawei Orange Telefonica Comcast China Unicom China Telecom The data model defined in RFC8345 introduces vertical layering relationships between networks that can be augmented to cover network/service topologies. This document defines a YANG model for both Network Performance Monitoring and VPN Service Performance Monitoring that can be used to monitor and manage network performance on the topology at higher layer or the service topology between VPN sites. This document does not define metrics for network performance or mechanisms for measuring network performance. The YANG model defined in this document is designed as an augmentation to the network topology YANG model defined in RFC 8345 and draws on relevant YANG types defined in RFC 6991, RFC 8299, RFC 8345, and RFC 8532. Work in Progress Volta Networks Metaswitch Networks Individual Juniper Networks Huawei Technologies ZTE Corporation This document defines a YANG data model that can be used to configure and manage devices supporting Protocol Independent Multicast (PIM). The model covers the PIM protocol configuration, operational state, and event notifications data. Work in Progress Cisco Systems VMware Juniper Networks Juniper Networks The MITRE Corporation This document describes a YANG model for Quality of Service (QoS) configuration and operational parameters. Work in Progress This document provides a framework for the operation and management of Layer 3 Virtual Private Networks (L3VPNs). This framework intends to produce a coherent description of the significant technical issues that are important in the design of L3VPN management solutions. The selection of specific approaches, and making choices among information models and protocols are outside the scope of this document. This memo provides information for the Internet community. This document describes a method by which a Service Provider may use an IP backbone to provide IP Virtual Private Networks (VPNs) for its customers. This method uses a "peer model", in which the customers' edge routers (CE routers) send their routes to the Service Provider's edge routers (PE routers); there is no "overlay" visible to the customer's routing algorithm, and CE routers at different sites do not peer with each other. Data packets are tunneled through the backbone, so that the core routers do not need to know the VPN routes. [STANDARDS-TRACK] This document provides a framework for Layer 2 Provider Provisioned Virtual Private Networks (L2VPNs). This framework is intended to aid in standardizing protocols and mechanisms to support interoperable L2VPNs. This memo provides information for the Internet community. Virtual Private LAN Service (VPLS), also known as Transparent LAN Service and Virtual Private Switched Network service, is a useful Service Provider offering. The service offers a Layer 2 Virtual Private Network (VPN); however, in the case of VPLS, the customers in the VPN are connected by a multipoint Ethernet LAN, in contrast to the usual Layer 2 VPNs, which are point-to-point in nature. This document describes the functions required to offer VPLS, a mechanism for signaling a VPLS, and rules for forwarding VPLS frames across a packet switched network. [STANDARDS-TRACK] This document describes a Virtual Private LAN Service (VPLS) solution using pseudowires, a service previously implemented over other tunneling technologies and known as Transparent LAN Services (TLS). A VPLS creates an emulated LAN segment for a given set of users; i.e., it creates a Layer 2 broadcast domain that is fully capable of learning and forwarding on Ethernet MAC addresses and that is closed to a given set of users. Multiple VPLS services can be supported from a single Provider Edge (PE) node. This document describes the control plane functions of signaling pseudowire labels using Label Distribution Protocol (LDP), extending RFC 4447. It is agnostic to discovery protocols. The data plane functions of forwarding are also described, focusing in particular on the learning of MAC addresses. The encapsulation of VPLS packets is described by RFC 4448. [STANDARDS-TRACK] Measuring capacity is a task that sounds simple, but in reality can be quite complex. In addition, the lack of a unified nomenclature on this subject makes it increasingly difficult to properly build, test, and use techniques and tools built around these constructs. This document provides definitions for the terms 'Capacity' and 'Available Capacity' related to IP traffic traveling between a source and destination in an IP network. By doing so, we hope to provide a common framework for the discussion and analysis of a diverse set of current and future estimation techniques. This memo provides information for the Internet community. This document defines the terminology that is to be used in describing Session PEERing for Multimedia INTerconnect (SPEERMINT). This memo provides information for the Internet community. This document describes a protocol intended to detect faults in the bidirectional path between two forwarding engines, including interfaces, data link(s), and to the extent possible the forwarding engines themselves, with potentially very low latency. It operates independently of media, data protocols, and routing protocols. [STANDARDS-TRACK] This document defines a peering architecture for the Session Initiation Protocol (SIP) and its functional components and interfaces. It also describes the components and the steps necessary to establish a session between two SIP Service Provider (SSP) peering domains. This document is not an Internet Standards Track specification; it is published for informational purposes. Software-Defined Networking (SDN) has been one of the major buzz words of the networking industry for the past couple of years. And yet, no clear definition of what SDN actually covers has been broadly admitted so far. This document aims to clarify the SDN landscape by providing a perspective on requirements, issues, and other considerations about SDN, as seen from within a service provider environment. It is not meant to endlessly discuss what SDN truly means but rather to suggest a functional taxonomy of the techniques that can be used under an SDN umbrella and to elaborate on the various pending issues the combined activation of such techniques inevitably raises. As such, a definition of SDN is only mentioned for the sake of clarification. This document defines the initial version of the iana-if-type YANG module. Operations, Administration, and Maintenance (OAM) is a general term that refers to a toolset for fault detection and isolation, and for performance measurement. Over the years, various OAM tools have been defined for various layers in the protocol stack. This document summarizes some of the OAM tools defined in the IETF in the context of IP unicast, MPLS, MPLS Transport Profile (MPLS-TP), pseudowires, and Transparent Interconnection of Lots of Links (TRILL). This document focuses on tools for detecting and isolating failures in networks and for performance monitoring. Control and management aspects of OAM are outside the scope of this document. Network repair functions such as Fast Reroute (FRR) and protection switching, which are often triggered by OAM protocols, are also out of the scope of this document. The target audience of this document includes network equipment vendors, network operators, and standards development organizations. This document can be used as an index to some of the main OAM tools defined in the IETF. At the end of the document, a list of the OAM toolsets and a list of the OAM functions are presented as a summary. This document describes the Connectivity Provisioning Profile (CPP) and proposes a CPP template to capture IP/MPLS connectivity requirements to be met within a service delivery context (e.g., Voice over IP or IP TV). The CPP defines the set of IP transfer parameters to be supported by the underlying transport network together with a reachability scope and bandwidth/capacity needs. Appropriate performance metrics, such as one-way delay or one-way delay variation, are used to characterize an IP transfer service. Both global and restricted reachability scopes can be captured in the CPP. Such a generic CPP template is meant to (1) facilitate the automation of the service negotiation and activation procedures, thus accelerating service provisioning, (2) set (traffic) objectives of Traffic Engineering functions and service management functions, and (3) improve service and network management systems with 'decision- making' capabilities based upon negotiated/offered CPPs. This document defines a YANG data model for the configuration and identification of some common system properties within a device containing a Network Configuration Protocol (NETCONF) server. This document also includes data node definitions for system identification, time-of-day management, user management, DNS resolver configuration, and some protocol operations for system management. This document specifies Transparent Interconnection of Lots of Links (TRILL) Operations, Administration, and Maintenance (OAM) fault management. Methods in this document follow the CFM (Connectivity Fault Management) framework defined in IEEE 802.1 and reuse OAM tools where possible. Additional messages and TLVs are defined for TRILL-specific applications or for cases where a different set of information is required other than CFM as defined in IEEE 802.1. This document updates RFC 6325. This document describes an architecture for the specification, creation, and ongoing maintenance of Service Function Chains (SFCs) in a network. It includes architectural concepts, principles, and components used in the construction of composite services through deployment of SFCs, with a focus on those to be standardized in the IETF. This document does not propose solutions, protocols, or extensions to existing protocols. This memo defines a metric for one-way delay of packets across Internet paths. It builds on notions introduced and discussed in the IP Performance Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be familiar with that document. This memo makes RFC 2679 obsolete. This memo defines a metric for one-way loss of packets across Internet paths. It builds on notions introduced and discussed in the IP Performance Metrics (IPPM) Framework document, RFC 2330; the reader is assumed to be familiar with that document. This memo makes RFC 2680 obsolete. Layer 2 services (such as Frame Relay, Asynchronous Transfer Mode, and Ethernet) can be emulated over an MPLS backbone by encapsulating the Layer 2 Protocol Data Units (PDUs) and then transmitting them over pseudowires (PWs). It is also possible to use pseudowires to provide low-rate Time-Division Multiplexed and Synchronous Optical NETworking circuit emulation over an MPLS-enabled network. This document specifies a protocol for establishing and maintaining the pseudowires, using extensions to the Label Distribution Protocol (LDP). Procedures for encapsulating Layer 2 PDUs are specified in other documents. This document is a rewrite of RFC 4447 for publication as an Internet Standard. This document defines a data model for Large-Scale Measurement Platforms (LMAPs). The data model is defined using the YANG data modeling language. The YANG data modeling language is currently being considered for a wide variety of applications throughout the networking industry at large. Many standards development organizations (SDOs), open-source software projects, vendors, and users are using YANG to develop and publish YANG modules for a wide variety of applications. At the same time, there is currently no well-known terminology to categorize various types of YANG modules. A consistent terminology would help with the categorization of YANG modules, assist in the analysis of the YANG data modeling efforts in the IETF and other organizations, and bring clarity to the YANG- related discussions between the different groups. This document describes a set of concepts and associated terms to support consistent classification of YANG modules. This document defines a YANG data model that can be used for communication between customers and network operators and to deliver a Layer 3 provider-provisioned VPN service. This document is limited to BGP PE-based VPNs as described in RFCs 4026, 4110, and 4364. This model is intended to be instantiated at the management system to deliver the overall service. It is not a configuration model to be used directly on network elements. This model provides an abstracted view of the Layer 3 IP VPN service configuration components. It will be up to the management system to take this model as input and use specific configuration models to configure the different network elements to deliver the service. How the configuration of network elements is done is out of scope for this document. This document obsoletes RFC 8049; it replaces the unimplementable module in that RFC with a new module with the same name that is not backward compatible. The changes are a series of small fixes to the YANG module and some clarifications to the text. The IETF has produced many modules in the YANG modeling language. The majority of these modules are used to construct data models to model devices or monolithic functions. A small number of YANG modules have been defined to model services (for example, the Layer 3 Virtual Private Network Service Model (L3SM) produced by the L3SM working group and documented in RFC 8049). This document describes service models as used within the IETF and also shows where a service model might fit into a software-defined networking architecture. Note that service models do not make any assumption of how a service is actually engineered and delivered for a customer; details of how network protocols and devices are engineered to deliver a service are captured in other modules that are not exposed through the interface between the customer and the provider. Datastores are a fundamental concept binding the data models written in the YANG data modeling language to network management protocols such as the Network Configuration Protocol (NETCONF) and RESTCONF. This document defines an architectural framework for datastores based on the experience gained with the initial simpler model, addressing requirements that were not well supported in the initial model. This document updates RFC 7950. This document defines a YANG data model for the management of network interfaces. It is expected that interface-type-specific data models augment the generic interfaces data model defined in this document. The data model includes definitions for configuration and system state (status information and counters for the collection of statistics). The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342. This document obsoletes RFC 7223. This document defines an abstract (generic, or base) YANG data model for network/service topologies and inventories. The data model serves as a base model that is augmented with technology-specific details in other, more specific topology and inventory data models. This document defines a YANG data model for Layer 3 network topologies. This document defines a YANG data model for the management of hardware on a single server. This document specifies three YANG modules and one submodule. Together, they form the core routing data model that serves as a framework for configuring and managing a routing subsystem. It is expected that these modules will be augmented by additional YANG modules defining data models for control-plane protocols, route filters, and other functions. The core routing data model provides common building blocks for such extensions -- routes, Routing Information Bases (RIBs), and control-plane protocols. The YANG modules in this document conform to the Network Management Datastore Architecture (NMDA). This document obsoletes RFC 8022. This document defines a YANG data model that can be used to configure a Layer 2 provider-provisioned VPN service. It is up to a management system to take this as an input and generate specific configuration models to configure the different network elements to deliver the service. How this configuration of network elements is done is out of scope for this document. The YANG data model defined in this document includes support for point-to-point Virtual Private Wire Services (VPWSs) and multipoint Virtual Private LAN Services (VPLSs) that use Pseudowires signaled using the Label Distribution Protocol (LDP) and the Border Gateway Protocol (BGP) as described in RFCs 4761 and 6624. The YANG data model defined in this document conforms to the Network Management Datastore Architecture defined in RFC 8342. This document defines a YANG module for the Network Address Translation (NAT) function. 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 (EAM) for SIIT, IPv6-to-IPv6 Network Prefix Translation (NPTv6), and Destination NAT are covered in this document. This document defines a YANG module for the Dual-Stack Lite (DS-Lite) Address Family Transition Router (AFTR) and Basic Bridging BroadBand (B4) elements. This document defines a data model for Access Control Lists (ACLs). An ACL is a user-ordered set of rules used to configure the forwarding behavior in a device. Each rule is used to find a match on a packet and define actions that will be performed on the packet. This document describes a YANG library that provides information about the YANG modules, datastores, and datastore schemas used by a network management server. Simple caching mechanisms are provided to allow clients to minimize retrieval of this information. This version of the YANG library supports the Network Management Datastore Architecture (NMDA) by listing all datastores supported by a network management server and the schema that is used by each of these datastores. This document defines a mechanism that adds the schema trees defined by a set of YANG modules onto a mount point defined in the schema tree in another YANG module. This document 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 VPN Routing and Forwarding (VRF) instances and Virtual Switch Instances (VSIs). The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) defined in RFC 8342. This document defines a logical network element (LNE) YANG module that is compliant with the Network Management Datastore Architecture (NMDA). This module 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. The YANG model in this document conforms with NMDA as defined in RFC 8342. This document presents a base YANG data model for connection-oriented Operations, Administration, and Maintenance (OAM) protocols. It provides a technology-independent abstraction of key OAM constructs for such protocols. The model presented here can be extended to include technology-specific details. This guarantees uniformity in the management of OAM protocols and provides support for nested OAM workflows (i.e., performing OAM functions at different levels through a unified interface). The YANG data model in this document conforms to the Network Management Datastore Architecture. This document presents a base YANG Data model for the management of Operations, Administration, and Maintenance (OAM) protocols that use connectionless communications. The data model is defined using the YANG data modeling language, as specified in RFC 7950. It provides a technology-independent abstraction of key OAM constructs for OAM protocols that use connectionless communication. The base model presented here can be extended to include technology-specific details. There are two key benefits of this approach: First, it leads to uniformity between OAM protocols. Second, it supports both nested OAM workflows (i.e., performing OAM functions at the same level or different levels through a unified interface) as well as interactive OAM workflows (i.e., performing OAM functions at the same level through a unified interface). This document presents a retrieval method YANG data model for connectionless Operations, Administration, and Maintenance (OAM) protocols. It provides technology-independent RPC operations for OAM protocols that use connectionless communication. The retrieval methods model herein presented can be extended to include technology- specific details. There are two key benefits of this approach: First, it leads to uniformity between OAM protocols. Second, it supports both nested OAM workflows (i.e., performing OAM functions at different or the same levels through a unified interface) as well as interactive OAM workflows (i.e., performing OAM functions at the same levels through a unified interface). This document defines a YANG module for alarm management. It includes functions for alarm-list management, alarm shelving, and notifications to inform management systems. There are also operations to manage the operator state of an alarm and administrative alarm procedures. The module carefully maps to relevant alarm standards. This document describes a mechanism that allows subscriber applications to request a continuous and customized stream of updates from a YANG datastore. Providing such visibility into updates enables new capabilities based on the remote mirroring and monitoring of configuration and operational state. This document defines a YANG data model that can be used to configure and manage Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) devices. This document specifies the initial version of a YANG module "iana-tunnel-type", which contains a collection of IANA-maintained YANG identities used as interface types for tunnel interfaces. The module reflects the "tunnelType" registry maintained by IANA. The latest revision of this YANG module can be obtained from the IANA website. Tunnel type values are not directly added to the Tunnel Interface Types YANG module; they must instead be added to the "tunnelType" IANA registry. Once a new tunnel type registration is made by IANA for a new tunneling scheme or even an existing one that is not already listed in the current registry (e.g., LISP, NSH), IANA will update the Tunnel Interface Types YANG module accordingly. Some of the IETF-defined tunneling techniques are not listed in the current IANA registry. It is not the intent of this document to update the existing IANA registry with a comprehensive list of tunnel technologies. Registrants must follow the IETF registration procedure for interface types whenever a new tunnel type is needed. This document defines YANG modules for the configuration and operation of IPv4-in-IPv6 softwire Border Relays and Customer Premises Equipment for the Lightweight 4over6, Mapping of Address and Port with Encapsulation (MAP-E), and Mapping of Address and Port using Translation (MAP-T) softwire mechanisms. The document specifies a Distributed Denial-of-Service Open Threat Signaling (DOTS) data channel used for bulk exchange of data that cannot easily or appropriately communicated through the DOTS signal channel under attack conditions. This is a companion document to "Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal Channel Specification" (RFC 8782). This document describes YANG mechanisms for defining abstract data structures with YANG. This document defines a YANG data model for representing, retrieving, and manipulating Traffic Engineering (TE) Topologies. The model serves as a base model that other technology-specific TE topology models can augment. This document provides for the association of tags with YANG modules. The expectation is for such tags to be used to help classify and organize modules. A method for defining, reading, and writing modules tags is provided. Tags may be registered and assigned during module definition, assigned by implementations, or dynamically defined and set by users. This document also provides guidance to future model writers; as such, this document updates RFC 8407. This document defines a YANG data model for Layer 2 network topologies. In particular, this data model augments the generic network and network topology data models with topology attributes that are specific to Layer 2. This document contains a specification of the MPLS base YANG data model. The MPLS base YANG data model serves as a base framework for configuring and managing an MPLS switching subsystem on an MPLS-enabled router. It is expected that other MPLS YANG data models (e.g., MPLS Label Switched Path (LSP) static, LDP, or RSVP-TE YANG data models) will augment the MPLS base YANG data model. Futurewei Apstra Cisco Volta Networks This document defines a YANG data model for configuring and managing routing policies in a vendor-neutral way. The model provides a generic routing policy framework which can be extended for specific routing protocols using the YANG 'augment' mechanism. Work in Progress Ericsson Volta Networks China Mobile Juniper Individual This document defines a YANG data model that can be used to configure and manage Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping devices. The YANG module in this document conforms to Network Management Datastore Architecture (NMDA). Work in Progress Cisco Systems Futurewei Cisco Systems Arrcus Networks Apstra This document defines a YANG data model for segment routing configuration and operation, which is to be augmented by different segment routing data planes. The document also defines a YANG model that is intended to be used on network elements to configure or operate segment routing MPLS data plane, as well as some generic containers to be reused by IGP protocol modules to support segment routing. Work in Progress ZTE Corp. ZTE Corp. Ericsson This document specifies the data model for implementations of Session-Sender and Session-Reflector for Simple Two-way Active Measurement Protocol (STAMP) mode using YANG. Work in Progress Samsung Electronics Huawei Technologies Huawei Technologies CTTC Lancaster University Ericsson This document provides YANG data models that describe performance monitoring telemetry and scaling intent mechanism for TE-tunnels and Virtual Networks (VN). The models presented in this draft allow customers to subscribe to and monitor their key performance data of their interest on the level of TE-tunnel or VN. The models also provide customers with the ability to program autonomic scaling intent mechanism on the level of TE-tunnel as well as VN. Work in Progress Huawei Nokia Telefonica Google China Unicom There are scenarios, typically in a hierarchical SDN context, where the topology information provided by a TE network provider may not be sufficient for its client to perform end-to-end path computation. In these cases the client would need to request the provider to calculate some (partial) feasible paths. This document defines a YANG data model for an RPC to request path computation. This model complements the solution, defined in RFCXXXX, to configure a TE Tunnel path in "compute-only" mode. [RFC EDITOR NOTE: Please replace RFC XXXX with the RFC number of draft-ietf-teas-yang-te once it has been published. Moreover this document describes some use cases where a path computation request, via YANG-based protocols (e.g., NETCONF or RESTCONF), can be needed. Work in Progress Juniper Networks Juniper Networks Cisco Systems Volta Networks Huawei Technologies Ciena This document defines a YANG data model for the configuration and management of RSVP (Resource Reservation Protocol) to establish Traffic-Engineered (TE) Label-Switched Paths (LSPs) for MPLS (Multi- Protocol Label Switching) and other technologies. The model defines a generic RSVP-TE module for signaling LSPs that are technology agnostic. The generic RSVP-TE module is to be augmented by technology specific RSVP-TE modules that define technology specific data. This document also defines the augmentation for RSVP-TE MPLS LSPs model. This model covers data for the configuration, operational state, remote procedural calls, and event notifications. Work in Progress Juniper Networks Cisco Systems Inc Volta Networks Juniper Networks Individual This document defines a YANG data model for the configuration and management of Traffic Engineering (TE) tunnels, Label Switched Paths (LSPs). and interfaces. The model is divided into YANG modules that classify data into generic, device-specific, technology agnostic, and technology-specific elements. This model covers data for configuration, operational state, remote procedural calls, and event notifications. Work in Progress This document presents YANG Data model for TRILL OAM. It extends the Generic YANG model for OAM defined in with TRILL technology specifics. Table of Contents. Work in Progress Ciena Corporation AT&T Labs Cisco Systems Xoriant Corporation Travelping This document specifies a data model for client and server implementations of the Two-Way Active Measurement Protocol (TWAMP). The document defines the TWAMP data model through Unified Modeling Language (UML) class diagrams and formally specifies it using a NDMA- compliant YANG model. Work in Progress Telefonica Telefonica Huawei Orange This document defines a YANG data model for representing an abstract view of the Service Provider network topology containing the points from which its services can be attached (e.g., basic connectivity, VPN, SDWAN). The data model augments the 'ietf-network' data model by adding the concept of service-attachment-points. The service- attachment-points are an abstraction of the points to which network services (such as L3 VPN or L2 VPN) can be attached. Work in Progress

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 . The reader may refer to the YANG Catalog (<>) or the public Github YANG repository (<>) to query existing YANG models. The YANG Catalog includes some metadata to indicate the module type ('module-classification') . Note that the mechanism defined in allows to associate tags with YANG modules in order to help classifying the modules.

Service Models: Definition and Samples As described in , 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" . 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 defines the L3VPN service ordered by a customer from a network operator.
• The L2SM defines the L2VPN service ordered by a customer from a network operator.
• The Virtual Network (VN) model provides a YANG data model applicable to any mode of VN operation.

L2SM and L3SM are customer service models as per .

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. 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.

Network Models: Samples L2NM and L3NM are examples of YANG network models. depicts a set of additional network models such as topology and tunnel models:

Sample Resource-Facing Network 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 | | | | +---------+ | | +-------------------------------+-------------------------------+

Examples of topology YANG modules are listed below:

Network Topologies Model:

defines a base model for network topology and inventories. Network topology data includes link, node, and terminate-point resources.

TE Topology Model:

defines a YANG data model for representing and manipulating TE topologies. This module is extended from the network topology model defined in 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:

defines a YANG data model for representing and manipulating Layer 3 topologies. This model is extended from the network topology model defined in and includes content related to Layer 3 topology specifics.

Layer 2 Topology Model:

defines a YANG data model for representing and manipulating Layer 2 topologies. This model is extended from the network topology model defined in and includes content related to Layer 2 topology specifics.

Examples of tunnel YANG modules are provided below:

Tunnel Identities:

defines a collection of YANG identities used as interface types for tunnel interfaces.

TE Tunnel Model:

defines a YANG module for the configuration and management of TE interfaces, tunnels, and LSPs.

Segment Routing (SR) Traffic Engineering (TE) Tunnel Model:

augments the TE generic and MPLS-TE model(s) and defines a YANG module for SR-TE-specific data.

MPLS-TE Model:

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:

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:

defines a YANG module for a stateless RPC that complements the stateful solution defined in .

OAM Models (including Fault Management (FM) and Performance Monitoring):

defines a base YANG module for the management of OAM protocols that use Connectionless Communications. defines a retrieval method YANG module for connectionless OAM protocols. 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. defines a YANG module for alarm management.

Device Models: Samples Network Element models (listed in ) 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
• BGP
• PIM
• NAT management
• QoS management
• ACLs

uses IETF-defined data models as an example.

Network Element Models Overview +------------------------+ +-+ 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| +-------+

Model Composition

Logical Network Element Model:

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:

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).

Device Management The following list enumerates some YANG modules that can be used for device management:

• defines a YANG module for the management of hardware.
• 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.
• defines a network configuration access control YANG module.

Interface Management The following provides some YANG modules that can be used for interface management:

• defines a YANG module for interface type definitions.
• defines a YANG module for the management of network interfaces.

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:

defines a YANG module for MPLS-based Layer 2 VPN services (L2VPN) 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 or BGP .

EVPN:

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:

defines a YANG module that can be used to configure and manage BGP L3VPNs . It contains VRF-specific parameters as well as BGP-specific parameters applicable for L3VPNs.

Core Routing:

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:

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:

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:

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:

defines a YANG module for segment routing configuration and operation.

BFD:

Bidirectional Forwarding Detection (BFD) is a network protocol that is used for liveness detection of arbitrary paths between systems. defines a YANG module that can be used to configure and manage BFD.

Multicast:

defines a YANG module that can be used to configure and manage Protocol Independent Multicast (PIM) devices. defines a YANG module that can be used to configure and manage Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) devices. defines a YANG module that can be used to configure and manage Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) snooping devices. defines a YANG data model to configure and manage Multicast in MPLS/BGP IP VPNs (MVPNs).

PM:

defines a YANG data model for client and server implementations of the Two-Way Active Measurement Protocol (TWAMP). defines the data model for implementations of Session-Sender and Session-Reflector for Simple Two-way Active Measurement Protocol (STAMP) mode using YANG. 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. describes a YANG data model of ACL basic building blocks.

QoS:

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. 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. specifies a Dual-Stack Lite (DS-Lite) YANG module.

Stateless Address Sharing:

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 , , , , , , , , and for the review. Many thanks to for the detailed AD review. Thanks to , , , and for the IESG review.

Contributors Orange

Rennes, 35000 France Christian.jacquenet@orange.com

Telefonica

luismiguel.contrerasmurillo@telefonica.com

Telefonica

Madrid Spain oscar.gonzalezdedios@telefonica.com

China Mobile

chengweiqiang@chinamobile.com

Sung Kyun Kwan University

younglee.tx@gmail.com

Authors' Addresses Huawei

101 Software Avenue Yuhua District Nanjing Jiangsu 210012 China bill.wu@huawei.com

Orange

Rennes 35000 France mohamed.boucadair@orange.com

Telefonica I+D

Spain diego.r.lopez@telefonica.com

China Telecom

Beijing China xiechf@chinatelecom.cn

China Mobile

gengliang@chinamobile.com