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| author | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
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| committer | Thomas Voss <mail@thomasvoss.com> | 2024-11-27 20:54:24 +0100 |
| commit | 4bfd864f10b68b71482b35c818559068ef8d5797 (patch) | |
| tree | e3989f47a7994642eb325063d46e8f08ffa681dc /doc/rfc/rfc8969.txt | |
| parent | ea76e11061bda059ae9f9ad130a9895cc85607db (diff) | |
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diff --git a/doc/rfc/rfc8969.txt b/doc/rfc/rfc8969.txt new file mode 100644 index 0000000..6d8805a --- /dev/null +++ b/doc/rfc/rfc8969.txt @@ -0,0 +1,2176 @@ + + + + +Internet Engineering Task Force (IETF) Q. Wu, Ed. +Request for Comments: 8969 Huawei +Category: Informational M. Boucadair, Ed. +ISSN: 2070-1721 Orange + D. Lopez + Telefonica I+D + C. Xie + China Telecom + L. Geng + China Mobile + January 2021 + + + A Framework for Automating Service and Network Management with YANG + +Abstract + + Data models provide a programmatic approach to represent services and + networks. Concretely, they can be used to derive configuration + information for network and service components, and state information + that will be monitored and tracked. Data models can be used during + the service and network management life cycle (e.g., service + instantiation, service provisioning, service optimization, service + monitoring, service diagnosing, and service assurance). Data models + are also instrumental in the automation of network management, and + they can provide closed-loop control for adaptive and deterministic + service creation, delivery, and maintenance. + + This document describes a framework for service and network + management automation that takes advantage of YANG modeling + technologies. This framework is drawn from a network operator + perspective irrespective of the origin of a data model; thus, it can + accommodate YANG modules that are developed outside the IETF. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are candidates for any level of Internet + Standard; see Section 2 of RFC 7841. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + https://www.rfc-editor.org/info/rfc8969. + +Copyright Notice + + Copyright (c) 2021 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (https://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction + 2. Terminology and Abbreviations + 2.1. Terminology + 2.2. Abbreviations + 3. Architectural Concepts and Goals + 3.1. Data Models: Layering and Representation + 3.2. Automation of Service Delivery Procedures + 3.3. Service Fulfillment Automation + 3.4. YANG Module Integration + 4. Functional Blocks and Interactions + 4.1. Service Life-Cycle Management Procedure + 4.1.1. Service Exposure + 4.1.2. Service Creation/Modification + 4.1.3. Service Assurance + 4.1.4. Service Optimization + 4.1.5. Service Diagnosis + 4.1.6. Service Decommission + 4.2. Service Fulfillment Management Procedure + 4.2.1. Intended Configuration Provision + 4.2.2. Configuration Validation + 4.2.3. Performance Monitoring + 4.2.4. Fault Diagnostic + 4.3. Multi-layer/Multi-domain Service Mapping + 4.4. Service Decomposition + 5. YANG Data Model Integration Examples + 5.1. L2VPN/L3VPN Service Delivery + 5.2. VN Life-Cycle Management + 5.3. Event-Based Telemetry in the Device Self Management + 6. Security Considerations + 6.1. Service Level + 6.2. Network Level + 6.3. Device Level + 7. IANA Considerations + 8. References + 8.1. Normative References + 8.2. Informative References + Appendix A. Layered YANG Module Examples Overview + A.1. Service Models: Definition and Samples + A.2. Schema Mount + A.3. Network Models: Samples + A.4. Device Models: Samples + A.4.1. Model Composition + A.4.2. Device Management + A.4.3. Interface Management + A.4.4. Some Device Model Examples + Acknowledgements + Contributors + Authors' Addresses + +1. Introduction + + Service management systems usually comprise service activation/ + provision and service operation. Current service delivery + procedures, from the processing of customer requirements and orders + to service delivery and operation, typically assume the manipulation + of data sequentially into multiple Operations Support System (OSS) or + Business Support System (BSS) applications that may be managed by + different departments within the service provider's organization + (e.g., billing factory, design factory, network operation center). + Many of these applications have been developed in house over the + years and operate in a silo mode. As a result: + + * The lack of standard data input/output (i.e., data model) raises + many challenges in system integration and often results in manual + configuration tasks. + + * Service fulfillment systems might have a limited visibility on the + network state and may therefore have a slow response to network + changes. + + Software-Defined Networking (SDN) becomes crucial to address these + challenges. SDN techniques are meant to automate the overall service + delivery procedures and typically rely upon standard data models. + These models are used not only to reflect service providers' savoir + faire, but also to dynamically instantiate and enforce a set of + service-inferred policies that best accommodate what has been defined + and possibly negotiated with the customer. [RFC7149] provides a + first tentative attempt to rationalize that service provider's view + on the SDN space by identifying concrete technical domains that need + to be considered and for which solutions can be provided. These + include: + + * Techniques for the dynamic discovery of topology, devices, and + capabilities, along with relevant information and data models that + are meant to precisely document such topology, devices, and their + capabilities. + + * Techniques for exposing network services [RFC8309] and their + characteristics. + + * Techniques used by service-derived dynamic resource allocation and + policy enforcement schemes, so that networks can be programmed + accordingly. + + * Dynamic feedback mechanisms that are meant to assess how + efficiently a given policy (or a set thereof) is enforced from a + service fulfillment and assurance perspective. + + Models are key for each of the four technical items above. Service + and network management automation is an important step to improve the + agility of network operations. Models are also important to ease + integrating multi-vendor solutions. + + YANG module [RFC7950] developers have taken both top-down and bottom- + up approaches to develop modules [RFC8199] and to establish a mapping + between a network technology and customer requirements at the top or + abstracting common constructs from various network technologies at + the bottom. At the time of writing this document (2020), there are + many YANG data models, including configuration and service models, + that have been specified or are being specified by the IETF. They + cover many of the networking protocols and techniques. However, how + these models work together to configure a function, manage a set of + devices involved in a service, or provide a service is something that + is not currently documented either within the IETF or other Standards + Development Organizations (SDOs). + + Many of the YANG modules listed in this document are used to exchange + data between NETCONF/RESTCONF clients and servers [RFC6241][RFC8040]. + Nevertheless, YANG is a transport-independent data modeling language. + It can thus be used independently of NETCONF/RESTCONF. For example, + YANG can be used to define abstract data structures [RFC8791] that + can be manipulated by other protocols (e.g., [DOTS-DDOS]). + + This document describes an architectural framework for service and + network management automation (Section 3) that takes advantage of + YANG modeling technologies and investigates how YANG data models at + different layers interact with each other (e.g., Service Mapping, + model composition) in the context of service delivery and fulfillment + (Section 4). Concretely, the following benefits can be provided: + + * Vendor-agnostic interfaces managing a service and the underlying + network are allowed. + + * Movement from deployment schemes where vendor-specific network + managers are required to a scheme where the entities that are + responsible for orchestrating and controlling services and network + resources provided by multi-vendor devices are unified is allowed. + + * Data inheritance and reusability among the various architecture + layers thus promoting a network-wise provisioning instead of + device-specific configuration is eased. + + * Dynamically feeding a decision-making process (e.g., Controllers, + Orchestrators) with notifications that will trigger appropriate + actions, allowing that decision-making process to continuously + adjust a network (and thus the involved resources) to deliver the + service that conforms to the intended parameters (service + objectives) is allowed. + + This framework is drawn from a network operator perspective + irrespective of the origin of a data model; it can also accommodate + YANG modules that are developed outside the IETF. The document + covers service models that are used by an operator to expose its + services and capture service requirements from the customers + (including other operators). Nevertheless, the document does not + elaborate on the communication protocol(s) that makes use of these + service models in order to request and deliver a service. Such + considerations are out of scope. + + The document identifies a list of use cases to exemplify the proposed + approach (Section 5), but it does not claim nor aim to be exhaustive. + Appendix A lists some examples to illustrate the layered YANG modules + view. + +2. Terminology and Abbreviations + + +2.1. Terminology + + The following terms are defined in [RFC8309] and [RFC8199] and are + not redefined here: + + * Network Operator + + * Customer + + * Service + + * Data Model + + * Service Model + + * Network Element Model + + In addition, the document makes use of the following terms: + + Network Model: + Describes a network-level abstraction (or a subset of aspects of a + network infrastructure), including devices and their subsystems, + and relevant protocols operating at the link and network layers + across multiple devices. This model corresponds to the network + configuration model discussed in [RFC8309]. + + It can be used by a network operator to allocate resources (e.g., + tunnel resource, topology resource) for the service or schedule + resources to meet the service requirements defined in a service + model. + + Network Domain: + Refers to a network partitioning that is usually followed by + network operators to delimit parts of their network. "access + network" and "core network" are examples of network domains. + + Device Model: + Refers to the Network Element YANG data model described in + [RFC8199] or the device configuration model discussed in + [RFC8309]. + + Device models are also used to refer to model a function embedded + in a device (e.g., Network Address Translation (NAT) [RFC8512], + Access Control Lists (ACLs) [RFC8519]). + + Pipe: + Refers to a communication scope where only one-to-one (1:1) + communications are allowed. The scope can be identified between + ingress and egress nodes, two service sites, etc. + + Hose: + Refers to a communication scope where one-to-many (1:N) + communications are allowed (e.g., one site to multiple sites). + + Funnel: + Refers to a communication scope where many-to-one (N:1) + communications are allowed. + +2.2. Abbreviations + + The following abbreviations are used in the document: + + ACL Access Control List + AS Autonomous System + AP Access Point + CE Customer Edge + DBE Data Border Element + E2E End-to-End + ECA Event Condition Action + L2VPN Layer 2 Virtual Private Network + L3VPN Layer 3 Virtual Private Network + L3SM L3VPN Service Model + L3NM L3VPN Network Model + NAT Network Address Translation + OAM Operations, Administration, and Maintenance + OWD One-Way Delay + PE Provider Edge + PM Performance Monitoring + QoS Quality of Service + RD Route Distinguisher + RT Route Target + SBE Session Border Element + SDN Software-Defined Networking + SP Service Provider + TE Traffic Engineering + VN Virtual Network + VPN Virtual Private Network + VRF Virtual Routing and Forwarding + + +3. Architectural Concepts and Goals + +3.1. Data Models: Layering and Representation + + As described in Section 2 of [RFC8199], layering of modules allows + for better reusability of lower-layer modules by higher-level modules + while limiting duplication of features across layers. + + Data models in the context of network management can be classified + into service, network, and device models. Different service models + may rely on the same set of network and/or device models. + + Service models traditionally follow a top-down approach and are + mostly customer-facing YANG modules providing a common model + construct for higher-level network services (e.g., Layer 3 Virtual + Private Network (L3VPN)). Such modules can be mapped to network + technology-specific modules at lower layers (e.g., tunnel, routing, + Quality of Service (QoS), security). For example, service models can + be used to characterize the network service(s) to be ensured between + service nodes (ingress/egress) such as: + + * the communication scope (pipe, hose, funnel, etc.), + * the directionality (inbound/outbound), + * the traffic performance guarantees expressed using metrics such as + One-Way Delay (OWD) [RFC7679] or One-Way Loss [RFC7680]; a summary + of performance metrics maintained by IANA can be found in [IPPM], + * link capacity [RFC5136] [METRIC-METHOD], + * etc. + + Figure 1 depicts the example of a Voice over IP (VoIP) service that + relies upon connectivity services offered by a network operator. In + this example, the VoIP service is offered to the network operator's + customers by Service Provider 1 (SP1). In order to provide global + VoIP reachability, SP1 Service Site interconnects with other Service + Providers service sites typically by interconnecting Session Border + Elements (SBEs) and Data Border Elements (DBEs) [RFC5486][RFC6406]. + For other VoIP destinations, sessions are forwarded over the + Internet. These connectivity services can be captured in a YANG + service model that reflects the service attributes that are shown in + Figure 2. This example follows the IP Connectivity Provisioning + Profile template defined in [RFC7297]. + + ,--,--,--. ,--,--,--. + ,-' SP1 `-. ,-' SP2 `-. + ( Service Site ) ( Service Site ) + `-. ,-' `-. ,-' + `--'--'--' `--'--'--' + x | o * * | + (2)x | o * * | + ,x-,--o-*-. (1) ,--,*-,--. + ,-' x o * * * * * * * * * `-. + ( x o +----( Internet ) + User---(x x x o o o o o o o o o o o o o o o o o o + `-. ,-' `-. ,-' (3) + `--'--'--' `--'--'--' + Network Operator + + **** (1) Inter-SP connectivity + xxxx (2) Customer-to-SP connectivity + oooo (3) SP to any destination connectivity + + Figure 1: An Example of Service Connectivity Components + + In reference to Figure 2, "Full traffic performance guarantees class" + refers to a service class where all traffic performance metrics + included in the service model (OWD, loss, delay variation) are + guaranteed, while "Delay traffic performance guarantees class" refers + to a service class where only OWD is guaranteed. + + Connectivity: Scope and Guarantees + (1) Inter-SP connectivity + - Pipe scope from the local to the remote SBE/DBE + - Full traffic performance guarantees class + (2) Customer-to-SP connectivity + - Hose/Funnel scope connecting the local SBE/DBE + to the customer access points + - Full traffic performance guarantees class + (3) SP to any destination connectivity + - Hose/Funnel scope from the local SBE/DBE to the + Internet gateway + - Delay traffic performance guarantees class + Flow Identification + * Destination IP address (SBE, DBE) + * DSCP marking + Traffic Isolation + * VPN + Routing & Forwarding + * Routing rule to exclude some ASes from the inter-domain + paths + Notifications (including feedback) + * Statistics on aggregate traffic to adjust capacity + * Failures + * Planned maintenance operations + * Triggered by thresholds + + Figure 2: Sample Attributes Captured in a Service Model + + Network models are mainly network-resource-facing modules; they + describe various aspects of a network infrastructure, including + devices and their subsystems, and relevant protocols operating at the + link and network layers across multiple devices (e.g., network + topology and traffic-engineering tunnel modules). + + Device (and function) models usually follow a bottom-up approach and + are mostly technology-specific modules used to realize a service + (e.g., BGP, ACL). + + Each level maintains a view of the supported YANG modules provided by + lower levels (see for example, Appendix A). Mechanisms such as the + YANG library [RFC8525] can be used to expose which YANG modules are + supported by nodes in lower levels. + + Figure 3 illustrates the overall layering model. The reader may + refer to Section 4 of [RFC8309] for an overview of "Orchestrator" and + "Controller" elements. All these elements (i.e., Orchestrator(s), + Controller(s), device(s)) are under the responsibility of the same + operator. + + + +-----------------------------------------------------------------+ + | Hierarchy Abstraction | + | | + | +-----------------------+ Service Model | + | | Orchestrator | (Customer Oriented) | + | |+---------------------+| Scope: "1:1" Pipe model | + | || Service Modeling || | + | |+---------------------+| | + | | | Bidirectional | + | |+---------------------+| +-+ Capacity, OWD +-+ | + | ||Service Orchestration|| | +----------------+ | | + | |+---------------------+| +-+ +-+ | + | +-----------------------+ Ingress Egress | + | | + | | + | +-----------------------+ Network Model | + | | Controller | (Operator Oriented) | + | |+---------------------+| +-+ +--+ +---+ +-+ | + | || Network Modeling || | | | | | | | | | + | |+---------------------+| | o----o--o----o---o---o | | + | | | +-+ +--+ +---+ +-+ | + | |+---------------------+| src dst | + | ||Network Orchestration|| L3VPN over TE | + | |+---------------------+| Instance Name/Access Interface | + | +-----------------------+ Protocol Type/Capacity/RD/RT/... | + | | + | | + | +-----------------------+ Device Model | + | | Device | | + | |+--------------------+ | | + | || Device Modeling | | Interface add, BGP Peer, | + | |+--------------------+ | Tunnel ID, QoS/TE, ... | + | +-----------------------+ | + +-----------------------------------------------------------------+ + + Figure 3: Layering and Representation within a Network Operator + + + A composite service offered by a network operator may rely on + services from other operators. In such a case, the network operator + acts as a customer to request services from other networks. The + operators providing these services will then follow the layering + depicted in Figure 3. The mapping between a composite service and a + third-party service is maintained at the orchestration level. From a + data-plane perspective, appropriate traffic steering policies (e.g., + Service Function Chaining [RFC7665]) are managed by the network + controllers to guide how/when a third-party service is invoked for + flows bound to a composite service. + + The layering model depicted in Figure 3 does not make any assumption + about the location of the various entities (e.g., Controller, + Orchestrator) within the network. As such, the architecture does not + preclude deployments where, for example, the Controller is embedded + on a device that hosts other functions that are controlled via YANG + modules. + + In order to ease the mapping between layers and data reuse, this + document focuses on service models that are modeled using YANG. + Nevertheless, fully compliant with Section 3 of [RFC8309], Figure 3 + does not preclude service models to be modeled using data modeling + languages other than YANG. + +3.2. Automation of Service Delivery Procedures + + Service models can be used by a network operator to expose its + services to its customers. Exposing such models allows automation of + the activation of service orders and thus the service delivery. One + or more monolithic service models can be used in the context of a + composite service activation request (e.g., delivery of a caching + infrastructure over a VPN). Such models are used to feed a decision- + making intelligence to adequately accommodate customer needs. + + Also, such models may be used jointly with services that require + dynamic invocation. An example is provided by the service modules + defined by the DOTS WG to dynamically trigger requests to handle + Distributed Denial-of-Service (DDoS) attacks [RFC8783]. The service + filtering request modeled using [RFC8783] will be translated into + device-specific filtering (e.g., ACLs defined in [RFC8519]) that + fulfills the service request. + + Network models can be derived from service models and used to + provision, monitor, and instantiate the service. Also, they are used + to provide life-cycle management of network resources. Doing so is + meant to: + + * expose network resources to customers (including other network + operators) to provide service fulfillment and assurance. + + * allow customers (or network operators) to dynamically adjust the + network resources based on service requirements as described in + service models (e.g., Figure 2) and the current network + performance information described in the telemetry modules. + + Note that it is out of the scope of this document to elaborate on the + communication protocols that are used to implement the interface + between the service ordering (customer) and service order handling + (provider). + +3.3. Service Fulfillment Automation + + To operate a service, the settings of the parameters in the device + models are derived from service models and/or network models and are + used to: + + * Provision each involved network function/device with the proper + configuration information. + + * Operate the network based on service requirements as described in + the service model(s) and local operational guidelines. + + In addition, the operational state including configuration that is in + effect together with statistics should be exposed to upper layers to + provide better network visibility and assess to what extent the + derived low-level modules are consistent with the upper-level inputs. + + Filters are enforced on the notifications that are communicated to + Service layers. The type and frequency of notifications may be + agreed upon in the service model. + + Note that it is important to correlate telemetry data with + configuration data to be used for closed loops at the different + stages of service delivery, from resource allocation to service + operation, in particular. + +3.4. YANG Module Integration + + To support top-down service delivery, YANG modules at different + levels or at the same level need to be integrated for proper service + delivery (including proper network setup). For example, the service + parameters captured in service models need to be decomposed into a + set of configuration/notification parameters that may be specific to + one or more technologies; these technology-specific parameters are + grouped together to define technology-specific device-level models or + network-level models. + + In addition, these technology-specific device or network models can + be further integrated with each other using the schema mount + mechanism [RFC8528] to provision each involved network function/ + device or each involved network domain to support newly added modules + or features. A collection of integrated device models can be loaded + and validated during implementation. + + High-level policies can be defined at service or network models + (e.g., "Autonomous System Number (ASN) Exclude" in the example + depicted in Figure 2). Device models will be tweaked accordingly to + provide policy-based management. Policies can also be used for + telemetry automation, e.g., policies that contain conditions to + trigger the generation and pushing of new telemetry data. + +4. Functional Blocks and Interactions + + The architectural considerations described in Section 3 lead to the + life-cycle management architecture illustrated in Figure 4 and + described in the following subsections. + + +------------------+ + ............... | | + Service level | | + V | + E2E E2E E2E E2E + Service --> Service ---------> Service ------------> Service + Exposure Creation ^ Optimization ^ Diagnosis + /Modification | | | + ^ | |Diff | | + E2E | | | E2E | | + Service ----+ | | Service | | + Decommission | +------ Assurance --+ | + | ^ | + Multi-layer | | | + Multi-domain | | | + Service Mapping| | | + ............... |<-----------------+ | | + Network level | | +-------+ v + V | | Specific + Specific Specific | Service + Service --------> Service <--+ | Diagnosis + Creation ^ Optimization | | | + /Modification | | | | + | |Diff | | | + | | Specific --+ | | + Service | | Service | | + Decomposition | +----- Assurance ----+ | + | ^ | + ............... | | Aggregation | + Device level | +------------+ | + V | | + Service Intent | v + Fulfillment Config ----> Config ----> Performance ----> Fault + Provision Validation Monitoring Diagnostic + + Figure 4: Service and Network Life-Cycle Management + +4.1. Service Life-Cycle Management Procedure + + Service life-cycle management includes end-to-end service life-cycle + management at the service level and technology-specific network life- + cycle management at the network level. + + The end-to-end service life-cycle management is technology- + independent service management and spans across multiple network + domains and/or multiple layers while technology-specific service + life-cycle management is technology domain-specific or layer-specific + service life-cycle management. + +4.1.1. Service Exposure + + A service in the context of this document (sometimes called "Network + Service") is some form of connectivity between customer sites and the + Internet or between customer sites across the operator's network and + across the Internet. + + Service exposure is used to capture services offered to customers + (ordering and order handling). One example is that a customer can + use an L3VPN Service Model (L3SM) to request L3VPN service by + providing the abstract technical characterization of the intended + service between customer sites. + + Service model catalogs can be created to expose the various services + and the information needed to invoke/order a given service. + +4.1.2. Service Creation/Modification + + A customer is usually unaware of the technology that the network + operator has available to deliver the service, so the customer does + not make requests specific to the underlying technology but is + limited to making requests specific to the service that is to be + delivered. This service request can be filled using a service model. + + Upon receiving a service request, and assuming that appropriate + authentication and authorization checks have been made with success, + the service Orchestrator/management system should verify whether the + service requirements in the service request can be met (i.e., whether + there are sufficient resources that can be allocated with the + requested guarantees). + + If the request is accepted, the service Orchestrator/management + system maps such a service request to its view. This view can be + described as a technology-specific network model or a set of + technology-specific device models, and this mapping may include a + choice of which networks and technologies to use depending on which + service features have been requested. + + In addition, a customer may require a change in the underlying + network infrastructure to adapt to new customers' needs and service + requirements (e.g., service a new customer site, add a new access + link, or provide disjoint paths). This service modification can be + issued following the same service model used by the service request. + + Withdrawing a service is discussed in Section 4.1.6. + +4.1.3. Service Assurance + + The performance measurement telemetry (Section 4.2.3) can be used to + provide service assurance at service and/or network levels. The + performance measurement telemetry model can tie with service or + network models to monitor network performance or Service Level + Agreements. + +4.1.4. Service Optimization + + Service optimization is a technique that gets the configuration of + the network updated due to network changes, incident mitigation, or + new service requirements. One example is once a tunnel or a VPN is + set up, performance monitoring information or telemetry information + per tunnel (or per VPN) can be collected and fed into the management + system. If the network performance doesn't meet the service + requirements, the management system can create new VPN policies + capturing network service requirements and populate them into the + network. + + Both network performance information and policies can be modeled + using YANG. With Policy-based management, self-configuration and + self-optimization behavior can be specified and implemented. + + The overall service optimization is managed at the service level, + while the network level is responsible for the optimization of the + specific network services it provides. + +4.1.5. Service Diagnosis + + Operations, Administration, and Maintenance (OAM) are important + networking functions for service diagnosis that allow network + operators to: + + * monitor network communications (i.e., reachability verification + and Continuity Check) + + * troubleshoot failures (i.e., fault verification and localization) + + * monitor service level agreements and performance (i.e., + performance management) + + When the network is down, service diagnosis should be in place to + pinpoint the problem and provide recommendations (or instructions) + for network recovery. + + The service diagnosis information can be modeled as technology- + independent Remote Procedure Call (RPC) operations for OAM protocols + and technology-independent abstraction of key OAM constructs for OAM + protocols [RFC8531][RFC8533]. These models can be used to provide + consistent configuration, reporting, and presentation for the OAM + mechanisms used to manage the network. + + Refer to Section 4.2.4 for the device-specific side. + +4.1.6. Service Decommission + + Service decommission allows a customer to stop the service by + removing the service from active status, thus releasing the network + resources that were allocated to the service. Customers can also use + the service model to withdraw the subscription to a service. + +4.2. Service Fulfillment Management Procedure + +4.2.1. Intended Configuration Provision + + Intended configuration at the device level is derived from network + models at the network level or service models at the service level + and represents the configuration that the system attempts to apply. + Take L3SM as a service model example to deliver an L3VPN service; + there is a need to map the L3VPN service view defined in the service + model into a detailed intended configuration view defined by specific + configuration models for network elements. The configuration + information includes: + + * Virtual Routing and Forwarding (VRF) definition, including VPN + policy expression + + * Physical Interface(s) + + * IP layer (IPv4, IPv6) + + * QoS features such as classification, profiles, etc. + + * Routing protocols: support of configuration of all protocols + listed in a service request, as well as routing policies + associated with those protocols + + * Multicast support + + * Address sharing + + * Security (e.g., access control, authentication, encryption) + + These specific configuration models can be used to configure Provider + Edge (PE) and Customer Edge (CE) devices within a site, e.g., a BGP + policy model can be used to establish VPN membership between sites + and VPN service topology. + + Note that in networks with legacy devices (that support proprietary + modules or do not support YANG at all), an adaptation layer is likely + to be required at the network level so that these devices can be + involved in the delivery of the network services. + + This interface is also used to handle service withdrawal + (Section 4.1.6). + +4.2.2. Configuration Validation + + Configuration validation is used to validate intended configuration + and ensure the configuration takes effect. + + For example, if a customer creates an interface "eth-0/0/0" but the + interface does not physically exist at this point, then configuration + data appears in the <intended> status but does not appear in the + <operational> datastore. More details about <intended> and + <operational> datastores can be found in Section 5.1 of [RFC8342]. + +4.2.3. Performance Monitoring + + When a configuration is in effect in a device, the <operational> + datastore holds the complete operational state of the device, + including learned, system, default configuration, and system state. + However, the configurations and state of a particular device do not + have visibility on the whole network, nor can they show how packets + are going to be forwarded through the entire network. Therefore, it + becomes more difficult to operate the entire network without + understanding the current status of the network. + + The management system should subscribe to updates of a YANG datastore + in all the network devices for performance monitoring purposes and + build a full topological visibility of the network by aggregating + (and filtering) these operational states from different sources. + +4.2.4. Fault Diagnostic + + When configuration is in effect in a device, some devices may be + misconfigured (e.g., device links are not consistent in both sides of + the network connection) or network resources might be misallocated. + Therefore, services may be negatively affected without knowing the + root cause in the network. + + Technology-dependent nodes and RPC commands are defined in + technology-specific YANG data models, which can use and extend the + base model described in Section 4.1.5 to deal with these issues. + + These RPC commands received in the technology-dependent node can be + used to trigger technology-specific OAM message exchanges for fault + verification and fault isolation. For example, Transparent + Interconnection of Lots of Links (TRILL) Multi-destination Tree + Verification (MTV) RPC command [TRILL-YANG-OAM] can be used to + trigger Multi-Destination Tree Verification Messages (MTVMs) defined + in [RFC7455] to verify TRILL distribution tree integrity. + +4.3. Multi-layer/Multi-domain Service Mapping + + Multi-layer/Multi-domain Service Mapping allows the mapping of an + end-to-end abstract view of the service segmented at different layers + and/or different network domains into domain-specific views. + + One example is to map service parameters in the L3SM into + configuration parameters such as Route Distinguisher (RD), Route + Target (RT), and VRF in the L3VPN Network Model (L3NM). + + Another example is to map service parameters in the L3SM into Traffic + Engineered (TE) tunnel parameters (e.g., Tunnel ID) in TE model and + Virtual Network (VN) parameters (e.g., Access Point (AP) list and VN + members) in the YANG data model for VN operation [ACTN-VN-YANG]. + +4.4. Service Decomposition + + Service Decomposition allows to decompose service models at the + service level or network models at the network level into a set of + device models at the device level. These device models may be tied + to specific device types or classified into a collection of related + YANG modules based on service types and features offered, and they + may load at the implementation time before configuration is loaded + and validated. + +5. YANG Data Model Integration Examples + + The following subsections provide some YANG data model integration + examples. + +5.1. L2VPN/L3VPN Service Delivery + + In reference to Figure 5, the following steps are performed to + deliver the L3VPN service within the network management automation + architecture defined in Section 4: + + 1. The Customer requests to create two sites (as per Service + Creation in Section 4.1.2) relying upon L3SM with each site + having one network access connectivity, for example: + + * Site A: network-access A, link-capacity = 20 Mbps, class + "foo", guaranteed-capacity-percent = 10, average-one-way-delay + = 70 ms. + + * Site B: network-access B, link-capacity = 30 Mbps, class + "foo1", guaranteed-capacity-percent = 15, average-one-way- + delay = 60 ms. + + 2. The Orchestrator extracts the service parameters from the L3SM. + Then, it uses them as input to the Service Mapping in Section 4.3 + to translate them into orchestrated configuration parameters + (e.g., RD, RT, and VRF) that are part of the L3NM specified in + [OPSAWG-L3SM-L3NM]. + + 3. The Controller takes the orchestrated configuration parameters in + the L3NM and translates them into an orchestrated (Service + Decomposition in Section 4.4) configuration of network elements + that are part of, e.g., BGP, QoS, Network Instance, IP + management, and interface models. + + [UNI-TOPOLOGY] can be used for representing, managing, and + controlling the User Network Interface (UNI) topology. + + L3SM | + Service | + Model | + +------------------------+------------------------+ + | +--------V--------+ | + | | Service Mapping | | + | +--------+--------+ | + | Orchestrator | | + +------------------------+------------------------+ + L3NM | ^ UNI Topology Model + Network | | + Model | | + +------------------------+------------------------+ + | +-----------V-----------+ | + | | Service Decomposition | | + | +--++---------------++--+ | + | || || | + | Controller || || | + +---------------++---------------++---------------+ + || || + || BGP, || + || QoS, || + || Interface, || + +------------+| NI, |+------------+ + | | IP | | + +--+--+ +--+--+ +--+--+ +--+--+ + | CE1 +-------+ PE1 | | PE2 +-------+ CE2 | + +-----+ +-----+ +-----+ +-----+ + + Figure 5: L3VPN Service Delivery Example (Current) + + L3NM inherits some of the data elements from the L3SM. Nevertheless, + the L3NM as designed in [OPSAWG-L3SM-L3NM] does not expose some + information to the above layer such as the capabilities of an + underlying network (which can be used to drive service order + handling) or notifications (to notify subscribers about specific + events or degradations as per agreed SLAs). Some of this information + can be provided using, e.g., [OPSAWG-YANG-VPN]. A target overall + model is depicted in Figure 6. + + L3SM | ^ + Service | | Notifications + Model | | + +------------------------+------------------------+ + | +--------V--------+ | + | | Service Mapping | | + | +--------+--------+ | + | Orchestrator | | + +------------------------+------------------------+ + L3NM | ^ UNI Topology Model + Network| | L3NM Notifications + Model | | L3NM Capabilities + +------------------------+------------------------+ + | +-----------V-----------+ | + | | Service Decomposition | | + | +--++---------------++--+ | + | || || | + | Controller || || | + +---------------++---------------++---------------+ + || || + || BGP, || + || QoS, || + || Interface, || + +------------+| NI, |+------------+ + | | IP | | + +--+--+ +--+--+ +--+--+ +--+--+ + | CE1 +-------+ PE1 | | PE2 +-------+ CE2 | + +-----+ +-----+ +-----+ +-----+ + + Figure 6: L3VPN Service Delivery Example (Target) + + Note that a similar analysis can be performed for Layer 2 VPNs + (L2VPNs). An L2VPN Service Model (L2SM) is defined in [RFC8466], + while the YANG L2VPN Network Model (L2NM) is specified in + [OPSAWG-L2NM]. + +5.2. VN Life-Cycle Management + + In reference to Figure 7, the following steps are performed to + deliver the VN service within the network management automation + architecture defined in Section 4: + + 1. A customer makes a request (Service Exposure in Section 4.1.1) to + create a VN. The association between the VN, APs, and VN members + is defined in the VN YANG model [ACTN-VN-YANG]. + + 2. The Orchestrator creates the single abstract node topology based + on the information captured in the request. + + 3. The customer exchanges with the Orchestrator the connectivity + matrix on the abstract node topology and explicit paths using the + TE topology model [RFC8795]. This information can be used to + instantiate the VN and set up tunnels between source and + destination endpoints (Service Creation in Section 4.1.2). + + 4. In order to provide service assurance (Service Optimization in + Section 4.1.4), the telemetry model that augments the VN model + and corresponding TE tunnel model can be used by the Orchestrator + to subscribe to performance measurement data. The Controller + will then notify the Orchestrator with all the parameter changes + and network performance changes related to the VN topology and + the tunnels [TEAS-ACTN-PM]. + + | + VN | + Service | + Model | + +----------------------|--------------------------+ + | Orchestrator | | + | +--------V--------+ | + | | Service Mapping | | + | +-----------------+ | + +----------------------+--------------------^-----+ + TE | Telemetry | + Tunnel | Model | + Model | | + +----------------------V--------------------+-----+ + | Controller | + | | + +-------------------------------------------------+ + + +-----+ +-----+ +-----+ +-----+ + | CE1 +------+ PE1 | | PE2 +------+ CE2 | + +-----+ +-----+ +-----+ +-----+ + + Figure 7: A VN Service Delivery Example + +5.3. Event-Based Telemetry in the Device Self Management + + In reference to Figure 8, the following steps are performed to + monitor state changes of managed resources in a network device and + provide device self management within the network management + automation architecture defined in Section 4: + + 1. To control which state a network device should be in or is + allowed to be in at any given time, a set of conditions and + actions are defined and correlated with network events (e.g., + allow the NETCONF server to send updates only when the value + exceeds a certain threshold for the first time, but not again + until the threshold is cleared), which constitute an Event + Condition Action (ECA) policy or an event-driven policy control + logic that can be executed on the device (e.g., [EVENT-YANG]). + + 2. To provide a rapid autonomic response that can exhibit self- + management properties, the Controller pushes the ECA policy to + the network device and delegates the network control logic to the + network device. + + 3. The network device uses the ECA model to subscribe to the event + source, e.g., an event stream or datastore state data conveyed to + the server via YANG-Push subscription [RFC8641], monitors state + parameters, and takes simple and instant actions when an + associated event condition on state parameters is met. ECA + notifications can be generated as the result of actions based on + event stream subscription or datastore subscription (model-driven + telemetry operation discussed in Section 4.2.3). + + +----------------+ + | <----+ + | Controller | | + +-------+--------+ | + | | + | | + ECA | | ECA + Model | | Notification + | | + | | + +------------V-------------+-----+ + |Device | | + | +-------+ +---------+ +--+---+ | + | | Event +-> Event +->Event | | + | | Source| |Condition| |Action| | + | +-------+ +---------+ +------+ | + +--------------------------------+ + + Figure 8: Event-Based Telemetry + +6. Security Considerations + + Many of the YANG modules cited in this document define schema for + data that is designed to be accessed via network management protocols + such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF + layer is the secure transport layer, and the mandatory-to-implement + secure transport is Secure Shell (SSH) [RFC6242]. The lowest + RESTCONF layer is HTTPS, and the mandatory-to-implement secure + transport is TLS [RFC8446]. + + The NETCONF access control model [RFC8341] provides the means to + restrict access for particular NETCONF or RESTCONF users to a + preconfigured subset of all available NETCONF or RESTCONF protocol + operations and content. + + Security considerations specific to each of the technologies and + protocols listed in the document are discussed in the specification + documents of each of these protocols. + + In order to prevent leaking sensitive information and the "confused + deputy" problem [Hardy] in general, special care should be considered + when translating between the various layers in Section 4 or when + aggregating data retrieved from various sources. Authorization and + authentication checks should be performed to ensure that data is + available to an authorized entity. The network operator must enforce + means to protect privacy-related information included in customer- + facing models. + + To detect misalignment between layers that might be induced by + misbehaving nodes, upper layers should continuously monitor the + perceived service (Section 4.1.4) and should proceed with checks to + assess that the provided service complies with the expected service + and that the data reported by an underlying layer is matching the + perceived service by the above layer. Such checks are the + responsibility of the service diagnosis (Section 4.1.5). + + When a YANG module includes security-related parameters, it is + recommended to include the relevant information as part of the + service assurance to track the correct functioning of the security + mechanisms. + + Additional considerations are discussed in the following subsections. + +6.1. Service Level + + A provider may rely on services offered by other providers to build + composite services. Appropriate mechanisms should be enabled by the + provider to monitor and detect a service disruption from these + providers. The characterization of a service disruption (including + mean time between failures and mean time to repair), the escalation + procedure, and penalties are usually documented in contractual + agreements (e.g., as described in Section 2.1 of [RFC4176]). + Misbehaving peer providers will thus be identified and appropriate + countermeasures will be applied. + + The communication protocols that make use of a service model between + a customer and an operator are out of scope. Relevant security + considerations should be discussed in the specification documents of + these protocols. + +6.2. Network Level + + Security considerations specific to the network level are listed + below: + + * A controller may create forwarding loops by misconfiguring the + underlying network nodes. It is recommended to proceed with tests + to check the status of forwarding paths regularly or whenever + changes are made to routing or forwarding processes. Such checks + may be triggered from the service level owing to the means + discussed in Section 4.1.5. + + * Some service models may include a traffic isolation clause that is + passed down to the network level so that appropriate technology- + specific actions must be enforced at the underlying network (and + thus involved network devices) to avoid that such traffic is + accessible to non-authorized parties. In particular, network + models may indicate whether encryption is enabled and, if so, + expose a list of supported encryption schemes and parameters. + Refer, for example, to the encryption feature defined in + [OPSAWG-VPN-COMMON] and its use in [OPSAWG-L3SM-L3NM]. + +6.3. Device Level + + Network operators should monitor and audit their networks to detect + misbehaving nodes and abnormal behaviors. For example, OAM, as + discussed in Section 4.1.5, can be used for that purpose. + + Access to some data requires specific access privilege levels. + Devices must check that a required access privilege is provided + before granting access to specific data or performing specific + actions. + +7. IANA Considerations + + This document has no IANA actions. + +8. References + +8.1. Normative References + + [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., + and A. Bierman, Ed., "Network Configuration Protocol + (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, + <https://www.rfc-editor.org/info/rfc6241>. + + [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure + Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, + <https://www.rfc-editor.org/info/rfc6242>. + + [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", + RFC 7950, DOI 10.17487/RFC7950, August 2016, + <https://www.rfc-editor.org/info/rfc7950>. + + [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF + Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, + <https://www.rfc-editor.org/info/rfc8040>. + + [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration + Access Control Model", STD 91, RFC 8341, + DOI 10.17487/RFC8341, March 2018, + <https://www.rfc-editor.org/info/rfc8341>. + + [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol + Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, + <https://www.rfc-editor.org/info/rfc8446>. + +8.2. Informative References + + [ACTN-VN-YANG] + Lee, Y., Dhody, D., Ceccarelli, D., Bryskin, I., and B. Y. + Yoon, "A YANG Data Model for VN Operation", Work in + Progress, Internet-Draft, draft-ietf-teas-actn-vn-yang-10, + 2 November 2020, <https://tools.ietf.org/html/draft-ietf- + teas-actn-vn-yang-10>. + + [BFD-YANG] Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S., + and G. Mirsky, "YANG Data Model for Bidirectional + Forwarding Detection (BFD)", Work in Progress, Internet- + Draft, draft-ietf-bfd-yang-17, 2 August 2018, + <https://tools.ietf.org/html/draft-ietf-bfd-yang-17>. + + [DOTS-DDOS] + Boucadair, M., Shallow, J., and T. Reddy.K, "Distributed + Denial-of-Service Open Threat Signaling (DOTS) Signal + Channel Specification", Work in Progress, Internet-Draft, + draft-ietf-dots-rfc8782-bis-04, 3 December 2020, + <https://tools.ietf.org/html/draft-ietf-dots-rfc8782-bis- + 04>. + + [EVENT-YANG] + Wu, Q., Bryskin, I., Birkholz, H., Liu, X., and B. Claise, + "A YANG Data model for ECA Policy Management", Work in + Progress, Internet-Draft, draft-wwx-netmod-event-yang-10, + 1 November 2020, <https://tools.ietf.org/html/draft-wwx- + netmod-event-yang-10>. + + [EVPN-YANG] + Brissette, P., Shah, H., Hussain, I., Tiruveedhula, K., + and J. Rabadan, "Yang Data Model for EVPN", Work in + Progress, Internet-Draft, draft-ietf-bess-evpn-yang-07, 11 + March 2019, <https://tools.ietf.org/html/draft-ietf-bess- + evpn-yang-07>. + + [Hardy] Hardy, N., "The Confused Deputy: (or why capabilities + might have been invented)", DOI 10.1145/54289.871709, + October 1988, + <https://dl.acm.org/doi/10.1145/54289.871709>. + + [IDR-BGP-MODEL] + Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP + YANG Model for Service Provider Networks", Work in + Progress, Internet-Draft, draft-ietf-idr-bgp-model-10, 15 + November 2020, + <https://tools.ietf.org/html/draft-ietf-idr-bgp-model-10>. + + [IPPM] IANA, "Performance Metrics", March 2020, + <https://www.iana.org/assignments/performance-metrics/ + performance-metrics.xhtml>. + + [L2VPN-YANG] + Shah, H., Brissette, P., Chen, I., Hussain, I., Wen, B., + and K. Tiruveedhula, "YANG Data Model for MPLS-based + L2VPN", Work in Progress, Internet-Draft, draft-ietf-bess- + l2vpn-yang-10, 2 July 2019, <https://tools.ietf.org/html/ + draft-ietf-bess-l2vpn-yang-10>. + + [L3VPN-YANG] + Jain, D., Patel, K., Brissette, P., Li, Z., Zhuang, S., + Liu, X., Haas, J., Esale, S., and B. Wen, "Yang Data Model + for BGP/MPLS L3 VPNs", Work in Progress, Internet-Draft, + draft-ietf-bess-l3vpn-yang-04, 19 October 2018, + <https://tools.ietf.org/html/draft-ietf-bess-l3vpn-yang- + 04>. + + [METRIC-METHOD] + Morton, A., Geib, R., and L. Ciavattone, "Metrics and + Methods for One-way IP Capacity", Work in Progress, + Internet-Draft, draft-ietf-ippm-capacity-metric-method-04, + 10 September 2020, <https://tools.ietf.org/html/draft- + ietf-ippm-capacity-metric-method-04>. + + [MVPN-YANG] + Liu, Y., Guo, F., Litkowski, S., Liu, X., Kebler, R., and + M. Sivakumar, "Yang Data Model for Multicast in MPLS/BGP + IP VPNs", Work in Progress, Internet-Draft, draft-ietf- + bess-mvpn-yang-04, 30 June 2020, + <https://tools.ietf.org/html/draft-ietf-bess-mvpn-yang- + 04>. + + [NETMOD-MODEL] + Clarke, J. and B. Claise, "YANG module for + yangcatalog.org", Work in Progress, Internet-Draft, draft- + clacla-netmod-model-catalog-03, 3 April 2018, + <https://tools.ietf.org/html/draft-clacla-netmod-model- + catalog-03>. + + [OPSAWG-L2NM] + Barguil, S., Dios, O. G. D., Boucadair, M., Munoz, L. A., + Jalil, L., and J. Ma, "A Layer 2 VPN Network YANG Model", + Work in Progress, Internet-Draft, draft-ietf-opsawg-l2nm- + 01, 2 November 2020, + <https://tools.ietf.org/html/draft-ietf-opsawg-l2nm-01>. + + [OPSAWG-L3SM-L3NM] + Barguil, S., Dios, O. G. D., Boucadair, M., Munoz, L. A., + and A. Aguado, "A Layer 3 VPN Network YANG Model", Work in + Progress, Internet-Draft, draft-ietf-opsawg-l3sm-l3nm-05, + 16 October 2020, <https://tools.ietf.org/html/draft-ietf- + opsawg-l3sm-l3nm-05>. + + [OPSAWG-VPN-COMMON] + Barguil, S., Dios, O. G. D., Boucadair, M., and Q. Wu, "A + Layer 2/3 VPN Common YANG Model", Work in Progress, + Internet-Draft, draft-ietf-opsawg-vpn-common-03, 14 + January 2021, <https://tools.ietf.org/html/draft-ietf- + opsawg-vpn-common-03>. + + [OPSAWG-YANG-VPN] + Wu, B., Wu, Q., Boucadair, M., Dios, O. G. D., Wen, B., + Liu, C., and H. Xu, "A YANG Model for Network and VPN + Service Performance Monitoring", Work in Progress, + Internet-Draft, draft-www-opsawg-yang-vpn-service-pm-03, + 21 January 2021, <https://tools.ietf.org/html/draft-www- + opsawg-yang-vpn-service-pm-03>. + + [PIM-YANG] Liu, X., McAllister, P., Peter, A., Sivakumar, M., Liu, + Y., and F. Hu, "A YANG Data Model for Protocol Independent + Multicast (PIM)", Work in Progress, Internet-Draft, draft- + ietf-pim-yang-17, 19 May 2018, + <https://tools.ietf.org/html/draft-ietf-pim-yang-17>. + + [QOS-MODEL] + Choudhary, A., Jethanandani, M., Strahle, N., Aries, E., + and I. Chen, "YANG Model for QoS", Work in Progress, + Internet-Draft, draft-ietf-rtgwg-qos-model-02, 9 July + 2020, <https://tools.ietf.org/html/draft-ietf-rtgwg-qos- + model-02>. + + [RFC4176] El Mghazli, Y., Ed., Nadeau, T., Boucadair, M., Chan, K., + and A. Gonguet, "Framework for Layer 3 Virtual Private + Networks (L3VPN) Operations and Management", RFC 4176, + DOI 10.17487/RFC4176, October 2005, + <https://www.rfc-editor.org/info/rfc4176>. + + [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private + Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February + 2006, <https://www.rfc-editor.org/info/rfc4364>. + + [RFC4664] Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer + 2 Virtual Private Networks (L2VPNs)", RFC 4664, + DOI 10.17487/RFC4664, September 2006, + <https://www.rfc-editor.org/info/rfc4664>. + + [RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private + LAN Service (VPLS) Using BGP for Auto-Discovery and + Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007, + <https://www.rfc-editor.org/info/rfc4761>. + + [RFC4762] Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private + LAN Service (VPLS) Using Label Distribution Protocol (LDP) + Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007, + <https://www.rfc-editor.org/info/rfc4762>. + + [RFC5136] Chimento, P. and J. Ishac, "Defining Network Capacity", + RFC 5136, DOI 10.17487/RFC5136, February 2008, + <https://www.rfc-editor.org/info/rfc5136>. + + [RFC5486] Malas, D., Ed. and D. Meyer, Ed., "Session Peering for + Multimedia Interconnect (SPEERMINT) Terminology", + RFC 5486, DOI 10.17487/RFC5486, March 2009, + <https://www.rfc-editor.org/info/rfc5486>. + + [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection + (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, + <https://www.rfc-editor.org/info/rfc5880>. + + [RFC6406] Malas, D., Ed. and J. Livingood, Ed., "Session PEERing for + Multimedia INTerconnect (SPEERMINT) Architecture", + RFC 6406, DOI 10.17487/RFC6406, November 2011, + <https://www.rfc-editor.org/info/rfc6406>. + + [RFC7149] Boucadair, M. and C. Jacquenet, "Software-Defined + Networking: A Perspective from within a Service Provider + Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014, + <https://www.rfc-editor.org/info/rfc7149>. + + [RFC7224] Bjorklund, M., "IANA Interface Type YANG Module", + RFC 7224, DOI 10.17487/RFC7224, May 2014, + <https://www.rfc-editor.org/info/rfc7224>. + + [RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. + Weingarten, "An Overview of Operations, Administration, + and Maintenance (OAM) Tools", RFC 7276, + DOI 10.17487/RFC7276, June 2014, + <https://www.rfc-editor.org/info/rfc7276>. + + [RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP + Connectivity Provisioning Profile (CPP)", RFC 7297, + DOI 10.17487/RFC7297, July 2014, + <https://www.rfc-editor.org/info/rfc7297>. + + [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for + System Management", RFC 7317, DOI 10.17487/RFC7317, August + 2014, <https://www.rfc-editor.org/info/rfc7317>. + + [RFC7455] Senevirathne, T., Finn, N., Salam, S., Kumar, D., Eastlake + 3rd, D., Aldrin, S., and Y. Li, "Transparent + Interconnection of Lots of Links (TRILL): Fault + Management", RFC 7455, DOI 10.17487/RFC7455, March 2015, + <https://www.rfc-editor.org/info/rfc7455>. + + [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function + Chaining (SFC) Architecture", RFC 7665, + DOI 10.17487/RFC7665, October 2015, + <https://www.rfc-editor.org/info/rfc7665>. + + [RFC7679] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, + Ed., "A One-Way Delay Metric for IP Performance Metrics + (IPPM)", STD 81, RFC 7679, DOI 10.17487/RFC7679, January + 2016, <https://www.rfc-editor.org/info/rfc7679>. + + [RFC7680] Almes, G., Kalidindi, S., Zekauskas, M., and A. Morton, + Ed., "A One-Way Loss Metric for IP Performance Metrics + (IPPM)", STD 82, RFC 7680, DOI 10.17487/RFC7680, January + 2016, <https://www.rfc-editor.org/info/rfc7680>. + + [RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and + Maintenance Using the Label Distribution Protocol (LDP)", + STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017, + <https://www.rfc-editor.org/info/rfc8077>. + + [RFC8194] Schoenwaelder, J. and V. Bajpai, "A YANG Data Model for + LMAP Measurement Agents", RFC 8194, DOI 10.17487/RFC8194, + August 2017, <https://www.rfc-editor.org/info/rfc8194>. + + [RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module + Classification", RFC 8199, DOI 10.17487/RFC8199, July + 2017, <https://www.rfc-editor.org/info/rfc8199>. + + [RFC8299] Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki, + "YANG Data Model for L3VPN Service Delivery", RFC 8299, + DOI 10.17487/RFC8299, January 2018, + <https://www.rfc-editor.org/info/rfc8299>. + + [RFC8309] Wu, Q., Liu, W., and A. Farrel, "Service Models + Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018, + <https://www.rfc-editor.org/info/rfc8309>. + + [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., + and R. Wilton, "Network Management Datastore Architecture + (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, + <https://www.rfc-editor.org/info/rfc8342>. + + [RFC8343] Bjorklund, M., "A YANG Data Model for Interface + Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, + <https://www.rfc-editor.org/info/rfc8343>. + + [RFC8345] Clemm, A., Medved, J., Varga, R., Bahadur, N., + Ananthakrishnan, H., and X. Liu, "A YANG Data Model for + Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March + 2018, <https://www.rfc-editor.org/info/rfc8345>. + + [RFC8346] Clemm, A., Medved, J., Varga, R., Liu, X., + Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model + for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346, + March 2018, <https://www.rfc-editor.org/info/rfc8346>. + + [RFC8348] Bierman, A., Bjorklund, M., Dong, J., and D. Romascanu, "A + YANG Data Model for Hardware Management", RFC 8348, + DOI 10.17487/RFC8348, March 2018, + <https://www.rfc-editor.org/info/rfc8348>. + + [RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for + Routing Management (NMDA Version)", RFC 8349, + DOI 10.17487/RFC8349, March 2018, + <https://www.rfc-editor.org/info/rfc8349>. + + [RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG + Data Model for Layer 2 Virtual Private Network (L2VPN) + Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October + 2018, <https://www.rfc-editor.org/info/rfc8466>. + + [RFC8512] Boucadair, M., Ed., Sivakumar, S., Jacquenet, C., + Vinapamula, S., and Q. Wu, "A YANG Module for Network + Address Translation (NAT) and Network Prefix Translation + (NPT)", RFC 8512, DOI 10.17487/RFC8512, January 2019, + <https://www.rfc-editor.org/info/rfc8512>. + + [RFC8513] Boucadair, M., Jacquenet, C., and S. Sivakumar, "A YANG + Data Model for Dual-Stack Lite (DS-Lite)", RFC 8513, + DOI 10.17487/RFC8513, January 2019, + <https://www.rfc-editor.org/info/rfc8513>. + + [RFC8519] Jethanandani, M., Agarwal, S., Huang, L., and D. Blair, + "YANG Data Model for Network Access Control Lists (ACLs)", + RFC 8519, DOI 10.17487/RFC8519, March 2019, + <https://www.rfc-editor.org/info/rfc8519>. + + [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., + and R. Wilton, "YANG Library", RFC 8525, + DOI 10.17487/RFC8525, March 2019, + <https://www.rfc-editor.org/info/rfc8525>. + + [RFC8528] Bjorklund, M. and L. Lhotka, "YANG Schema Mount", + RFC 8528, DOI 10.17487/RFC8528, March 2019, + <https://www.rfc-editor.org/info/rfc8528>. + + [RFC8529] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X. + Liu, "YANG Data Model for Network Instances", RFC 8529, + DOI 10.17487/RFC8529, March 2019, + <https://www.rfc-editor.org/info/rfc8529>. + + [RFC8530] Berger, L., Hopps, C., Lindem, A., Bogdanovic, D., and X. + Liu, "YANG Model for Logical Network Elements", RFC 8530, + DOI 10.17487/RFC8530, March 2019, + <https://www.rfc-editor.org/info/rfc8530>. + + [RFC8531] Kumar, D., Wu, Q., and Z. Wang, "Generic YANG Data Model + for Connection-Oriented Operations, Administration, and + Maintenance (OAM) Protocols", RFC 8531, + DOI 10.17487/RFC8531, April 2019, + <https://www.rfc-editor.org/info/rfc8531>. + + [RFC8532] Kumar, D., Wang, Z., Wu, Q., Ed., Rahman, R., and S. + Raghavan, "Generic YANG Data Model for the Management of + Operations, Administration, and Maintenance (OAM) + Protocols That Use Connectionless Communications", + RFC 8532, DOI 10.17487/RFC8532, April 2019, + <https://www.rfc-editor.org/info/rfc8532>. + + [RFC8533] Kumar, D., Wang, M., Wu, Q., Ed., Rahman, R., and S. + Raghavan, "A YANG Data Model for Retrieval Methods for the + Management of Operations, Administration, and Maintenance + (OAM) Protocols That Use Connectionless Communications", + RFC 8533, DOI 10.17487/RFC8533, April 2019, + <https://www.rfc-editor.org/info/rfc8533>. + + [RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm + Management", RFC 8632, DOI 10.17487/RFC8632, September + 2019, <https://www.rfc-editor.org/info/rfc8632>. + + [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications + for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, + September 2019, <https://www.rfc-editor.org/info/rfc8641>. + + [RFC8652] Liu, X., Guo, F., Sivakumar, M., McAllister, P., and A. + Peter, "A YANG Data Model for the Internet Group + Management Protocol (IGMP) and Multicast Listener + Discovery (MLD)", RFC 8652, DOI 10.17487/RFC8652, November + 2019, <https://www.rfc-editor.org/info/rfc8652>. + + [RFC8675] Boucadair, M., Farrer, I., and R. Asati, "A YANG Data + Model for Tunnel Interface Types", RFC 8675, + DOI 10.17487/RFC8675, November 2019, + <https://www.rfc-editor.org/info/rfc8675>. + + [RFC8676] Farrer, I., Ed. and M. Boucadair, Ed., "YANG Modules for + IPv4-in-IPv6 Address plus Port (A+P) Softwires", RFC 8676, + DOI 10.17487/RFC8676, November 2019, + <https://www.rfc-editor.org/info/rfc8676>. + + [RFC8783] Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed + Denial-of-Service Open Threat Signaling (DOTS) Data + Channel Specification", RFC 8783, DOI 10.17487/RFC8783, + May 2020, <https://www.rfc-editor.org/info/rfc8783>. + + [RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data + Structure Extensions", RFC 8791, DOI 10.17487/RFC8791, + June 2020, <https://www.rfc-editor.org/info/rfc8791>. + + [RFC8795] Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and + O. Gonzalez de Dios, "YANG Data Model for Traffic + Engineering (TE) Topologies", RFC 8795, + DOI 10.17487/RFC8795, August 2020, + <https://www.rfc-editor.org/info/rfc8795>. + + [RFC8819] Hopps, C., Berger, L., and D. Bogdanovic, "YANG Module + Tags", RFC 8819, DOI 10.17487/RFC8819, January 2021, + <https://www.rfc-editor.org/info/rfc8819>. + + [RFC8944] Dong, J., Wei, X., Wu, Q., Boucadair, M., and A. Liu, "A + YANG Data Model for Layer 2 Network Topologies", RFC 8944, + DOI 10.17487/RFC8944, November 2020, + <https://www.rfc-editor.org/info/rfc8944>. + + [RFC8960] Saad, T., Raza, K., Gandhi, R., Liu, X., and V. Beeram, "A + YANG Data Model for MPLS Base", RFC 8960, + DOI 10.17487/RFC8960, December 2020, + <https://www.rfc-editor.org/info/rfc8960>. + + [RTGWG-POLICY] + Qu, Y., Tantsura, J., Lindem, A., and X. Liu, "A YANG Data + Model for Routing Policy", Work in Progress, Internet- + Draft, draft-ietf-rtgwg-policy-model-27, 10 January 2021, + <https://tools.ietf.org/html/draft-ietf-rtgwg-policy- + model-27>. + + [SNOOPING-YANG] + Zhao, H., Liu, X., Liu, Y., Sivakumar, M., and A. Peter, + "A Yang Data Model for IGMP and MLD Snooping", Work in + Progress, Internet-Draft, draft-ietf-pim-igmp-mld- + snooping-yang-18, 14 August 2020, + <https://tools.ietf.org/html/draft-ietf-pim-igmp-mld- + snooping-yang-18>. + + [SPRING-SR-YANG] + Litkowski, S., Qu, Y., Lindem, A., Sarkar, P., and J. + Tantsura, "YANG Data Model for Segment Routing", Work in + Progress, Internet-Draft, draft-ietf-spring-sr-yang-29, 8 + December 2020, <https://tools.ietf.org/html/draft-ietf- + spring-sr-yang-29>. + + [STAMP-YANG] + Mirsky, G., Min, X., and W. S. Luo, "Simple Two-way Active + Measurement Protocol (STAMP) Data Model", Work in + Progress, Internet-Draft, draft-ietf-ippm-stamp-yang-06, 7 + October 2020, <https://tools.ietf.org/html/draft-ietf- + ippm-stamp-yang-06>. + + [TEAS-ACTN-PM] + Lee, Y., Dhody, D., Karunanithi, S., Vilalta, R., King, + D., and D. Ceccarelli, "YANG models for VN/TE Performance + Monitoring Telemetry and Scaling Intent Autonomics", Work + in Progress, Internet-Draft, draft-ietf-teas-actn-pm- + telemetry-autonomics-04, 2 November 2020, + <https://tools.ietf.org/html/draft-ietf-teas-actn-pm- + telemetry-autonomics-04>. + + [TEAS-YANG-PATH-COMP] + Busi, I., Belotti, S., Lopez, V., Sharma, A., and Y. Shi, + "Yang model for requesting Path Computation", Work in + Progress, Internet-Draft, draft-ietf-teas-yang-path- + computation-11, 16 November 2020, + <https://tools.ietf.org/html/draft-ietf-teas-yang-path- + computation-11>. + + [TEAS-YANG-RSVP] + Beeram, V. P., Saad, T., Gandhi, R., Liu, X., Bryskin, I., + and H. Shah, "A YANG Data Model for RSVP-TE Protocol", + Work in Progress, Internet-Draft, draft-ietf-teas-yang- + rsvp-te-08, 9 March 2020, <https://tools.ietf.org/html/ + draft-ietf-teas-yang-rsvp-te-08>. + + [TEAS-YANG-TE] + Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I. + Bryskin, "A YANG Data Model for Traffic Engineering + Tunnels, Label Switched Paths and Interfaces", Work in + Progress, Internet-Draft, draft-ietf-teas-yang-te-25, 27 + July 2020, + <https://tools.ietf.org/html/draft-ietf-teas-yang-te-25>. + + [TRILL-YANG-OAM] + Kumar, D., Senevirathne, T., Finn, N., Salam, S., Xia, L., + and W. Hao, "YANG Data Model for TRILL Operations, + Administration, and Maintenance (OAM)", Work in Progress, + Internet-Draft, draft-ietf-trill-yang-oam-05, 31 March + 2017, <https://tools.ietf.org/html/draft-ietf-trill-yang- + oam-05>. + + [TWAMP-DATA-MODEL] + Civil, R., Morton, A., Rahman, R., Jethanandani, M., and + K. Pentikousis, "Two-Way Active Measurement Protocol + (TWAMP) Data Model", Work in Progress, Internet-Draft, + draft-ietf-ippm-twamp-yang-13, 2 July 2018, + <https://tools.ietf.org/html/draft-ietf-ippm-twamp-yang- + 13>. + + [UNI-TOPOLOGY] + Dios, O. G. D., Barguil, S., Wu, Q., and M. Boucadair, "A + YANG Model for User-Network Interface (UNI) Topologies", + Work in Progress, Internet-Draft, draft-ogondio-opsawg- + uni-topology-01, 2 April 2020, + <https://tools.ietf.org/html/draft-ogondio-opsawg-uni- + topology-01>. + +Appendix A. Layered YANG Module Examples Overview + + This appendix lists a set of YANG data models that can be used for + the delivery of connectivity services. These models can be + classified as service, network, or device models. + + It is not the intent of this appendix to provide an inventory of + tools and mechanisms used in specific network and service management + domains; such inventory can be found in documents such as [RFC7276]. + + The reader may refer to the YANG Catalog + (<https://www.yangcatalog.org>) or the public Github YANG repository + (<https://github.com/YangModels/yang>) to query existing YANG models. + The YANG Catalog includes some metadata to indicate the module type + ('module-classification') [NETMOD-MODEL]. Note that the mechanism + defined in [RFC8819] allows to associate tags with YANG modules in + order to help classifying the modules. + +A.1. Service Models: Definition and Samples + + As described in [RFC8309], the service is "some form of connectivity + between customer sites and the Internet or between customer sites + across the network operator's network and across the Internet". More + concretely, an IP connectivity service can be defined as the IP + transfer capability characterized by a (Source Nets, Destination + Nets, Guarantees, Scope) tuple where "Source Nets" is a group of + unicast IP addresses, "Destination Nets" is a group of IP unicast + and/or multicast addresses, and "Guarantees" reflects the guarantees + (expressed, for example, in terms of QoS, performance, and + availability) to properly forward traffic to the said "Destination" + [RFC7297]. The "Scope" denotes the network perimeter (e.g., between + Provider Edge (PE) routers or Customer Nodes) where the said + guarantees need to be provided. + + For example: + + * The L3SM [RFC8299] defines the L3VPN service ordered by a customer + from a network operator. + + * The L2SM [RFC8466] defines the L2VPN service ordered by a customer + from a network operator. + + * The Virtual Network (VN) model [ACTN-VN-YANG] provides a YANG data + model applicable to any mode of VN operation. + + L2SM and L3SM are customer service models as per [RFC8309]. + +A.2. Schema Mount + + Modularity and extensibility were among the leading design principles + of the YANG data modeling language. As a result, the same YANG + module can be combined with various sets of other modules and thus + form a data model that is tailored to meet the requirements of a + specific use case. [RFC8528] defines a mechanism, denoted "schema + mount", that allows for mounting one data model consisting of any + number of YANG modules at a specified location of another (parent) + schema. + +A.3. Network Models: Samples + + L2NM [OPSAWG-L2NM] and L3NM [OPSAWG-L3SM-L3NM] are examples of YANG + network models. + + Figure 9 depicts a set of additional network models such as topology + and tunnel models: + + +-------------------------------+-------------------------------+ + | Topology YANG modules | Tunnel YANG modules | + +-------------------------------+-------------------------------+ + | +------------------+ | | + | |Network Topologies| | +------+ +-----------+ | + | | Model | | |Other | | TE Tunnel | | + | +--------+---------+ | |Tunnel| +----+------+ | + | | +---------+ | +------+ | | + | +---+Service | | +----------+---------+ | + | | |Topology | | | | | | + | | +---------+ | | | | | + | | +---------+ |+----+---+ +----+---+ +---+---+| + | +---+Layer 3 | ||MPLS-TE | |RSVP-TE | | SR-TE || + | | |Topology | || Tunnel | | Tunnel | |Tunnel || + | | +---------+ |+--------+ +--------+ +-------+| + | | +---------+ | | + | +---+TE | | | + | | |Topology | | | + | | +---------+ | | + | | +---------+ | | + | +---+Layer 3 | | | + | |Topology | | | + | +---------+ | | + +-------------------------------+-------------------------------+ + + Figure 9: Sample Resource-Facing Network Models + + + Examples of topology YANG modules are listed below: + + Network Topologies Model: + [RFC8345] defines a base model for network topology and + inventories. Network topology data includes link, node, and + terminate-point resources. + + TE Topology Model: + [RFC8795] defines a YANG data model for representing and + manipulating TE topologies. + + This module is extended from the network topology model defined in + [RFC8345] and includes content related to TE topologies. This + model contains technology-agnostic TE topology building blocks + that can be augmented and used by other technology-specific TE + topology models. + + Layer 3 Topology Model: + [RFC8346] defines a YANG data model for representing and + manipulating Layer 3 topologies. This model is extended from the + network topology model defined in [RFC8345] and includes content + related to Layer 3 topology specifics. + + Layer 2 Topology Model: + [RFC8944] defines a YANG data model for representing and + manipulating Layer 2 topologies. This model is extended from the + network topology model defined in [RFC8345] and includes content + related to Layer 2 topology specifics. + + Examples of tunnel YANG modules are provided below: + + Tunnel Identities: + [RFC8675] defines a collection of YANG identities used as + interface types for tunnel interfaces. + + TE Tunnel Model: + [TEAS-YANG-TE] defines a YANG module for the configuration and + management of TE interfaces, tunnels, and LSPs. + + Segment Routing (SR) Traffic Engineering (TE) Tunnel Model: + [TEAS-YANG-TE] augments the TE generic and MPLS-TE model(s) and + defines a YANG module for SR-TE-specific data. + + MPLS-TE Model: + [TEAS-YANG-TE] augments the TE generic and MPLS-TE model(s) and + defines a YANG module for MPLS-TE configurations, state, RPC, and + notifications. + + RSVP-TE MPLS Model: + [TEAS-YANG-RSVP] augments the RSVP-TE generic module with + parameters to configure and manage signaling of MPLS RSVP-TE LSPs. + + Other sample network models are listed hereafter: + + Path Computation API Model: + [TEAS-YANG-PATH-COMP] defines a YANG module for a stateless RPC + that complements the stateful solution defined in [TEAS-YANG-TE]. + + OAM Models (including Fault Management (FM) and Performance + Monitoring): + [RFC8532] defines a base YANG module for the management of OAM + protocols that use Connectionless Communications. [RFC8533] + defines a retrieval method YANG module for connectionless OAM + protocols. [RFC8531] defines a base YANG module for connection- + oriented OAM protocols. These three models are intended to + provide consistent reporting, configuration, and representation + for connectionless OAM and connection-oriented OAM separately. + + Alarm monitoring is a fundamental part of monitoring the network. + Raw alarms from devices do not always tell the status of the + network services or necessarily point to the root cause. + [RFC8632] defines a YANG module for alarm management. + +A.4. Device Models: Samples + + Network Element models (listed in Figure 10) are used to describe how + a service can be implemented by activating and tweaking a set of + functions (enabled in one or multiple devices, or hosted in cloud + infrastructures) that are involved in the service delivery. For + example, the L3VPN service will involve many PEs and require + manipulating the following modules: + + * Routing management [RFC8349] + + * BGP [IDR-BGP-MODEL] + + * PIM [PIM-YANG] + + * NAT management [RFC8512] + + * QoS management [QOS-MODEL] + + * ACLs [RFC8519] + + Figure 10 uses IETF-defined data models as an example. + + +------------------------+ + +-+ Device Model | + | +------------------------+ + | +------------------------+ + +---------------+ | | Logical Network | + | | +-+ Element Model | + | Architecture | | +------------------------+ + | | | +------------------------+ + +-------+-------+ +-+ Network Instance Model | + | | +------------------------+ + | | +------------------------+ + | +-+ Routing Type Model | + | +------------------------+ + +-------+----------+----+------+------------+-----------+------+ + | | | | | | | + +-+-+ +---+---+ +----+----+ +--+--+ +----+----+ +--+--+ | + |ACL| |Routing| |Transport| | OAM | |Multicast| | PM | Others + +---+ +-+-----+ +----+----+ +--+--+ +-----+---+ +--+--+ + | +-------+ | +------+ | +--------+ | +-----+ | +-----+ + +-+Core | +-+ MPLS | +-+ BFD | +-+IGMP | +-+TWAMP| + | |Routing| | | Base | | +--------+ | |/MLD | | +-----+ + | +-------+ | +------+ | +--------+ | +-----+ | +-----+ + | +-------+ | +------+ +-+LSP Ping| | +-----+ +-+OWAMP| + +-+ BGP | +-+ MPLS | | +--------+ +-+ PIM | | +-----+ + | +-------+ | | LDP | | +--------+ | +-----+ | +-----+ + | +-------+ | +------+ +-+MPLS-TP | | +-----+ +-+LMAP | + +-+ ISIS | | +------+ +--------+ +-+ MVPN| +-----+ + | +-------+ +-+ MPLS | +-----+ + | +-------+ |Static| + +-+ OSPF | +------+ + | +-------+ + | +-------+ + +-+ RIP | + | +-------+ + | +-------+ + +-+ VRRP | + | +-------+ + | +-------+ + +-+SR/SRv6| + | +-------+ + | +-------+ + +-+ISIS-SR| + | +-------+ + | +-------+ + +-+OSPF-SR| + +-------+ + + Figure 10: Network Element Models Overview + +A.4.1. Model Composition + + Logical Network Element Model: + [RFC8530] defines a logical network element model that can be used + to manage the logical resource partitioning that may be present on + a network device. Examples of common industry terms for logical + resource partitioning are Logical Systems or Logical Routers. + + Network Instance Model: + [RFC8529] defines a network instance module. This module can be + used to manage the virtual resource partitioning that may be + present on a network device. Examples of common industry terms + for virtual resource partitioning are VRF instances and Virtual + Switch Instances (VSIs). + +A.4.2. Device Management + + The following list enumerates some YANG modules that can be used for + device management: + + * [RFC8348] defines a YANG module for the management of hardware. + + * [RFC7317] defines the "ietf-system" YANG module that provides many + features such as the configuration and the monitoring of system or + system control operations (e.g., shutdown, restart, and setting + time) identification. + + * [RFC8341] defines a network configuration access control YANG + module. + +A.4.3. Interface Management + + The following provides some YANG modules that can be used for + interface management: + + * [RFC7224] defines a YANG module for interface type definitions. + + * [RFC8343] defines a YANG module for the management of network + interfaces. + +A.4.4. Some Device Model Examples + + The following provides an overview of some device models that can be + used within a network. This list is not comprehensive. + + L2VPN: + [L2VPN-YANG] defines a YANG module for MPLS-based Layer 2 VPN + services (L2VPN) [RFC4664] and includes switching between the + local attachment circuits. The L2VPN model covers point-to-point + Virtual Private Wire Service (VPWS) and Multipoint Virtual Private + LAN Service (VPLS). These services use signaling of Pseudowires + across MPLS networks using LDP [RFC8077][RFC4762] or BGP + [RFC4761]. + + EVPN: + [EVPN-YANG] defines a YANG module for Ethernet VPN services. The + model is agnostic of the underlay. It applies to MPLS as well as + to Virtual eXtensible Local Area Network (VxLAN) encapsulation. + The module is also agnostic to the services, including E-LAN, + E-LINE, and E-TREE services. + + L3VPN: + [L3VPN-YANG] defines a YANG module that can be used to configure + and manage BGP L3VPNs [RFC4364]. It contains VRF-specific + parameters as well as BGP-specific parameters applicable for + L3VPNs. + + Core Routing: + [RFC8349] defines the core routing YANG data model, which is + intended as a basis for future data model development covering + more-sophisticated routing systems. It is expected that other + Routing technology YANG modules (e.g., VRRP, RIP, ISIS, or OSPF + models) will augment the Core Routing base YANG module. + + MPLS: + [RFC8960] defines a base model for MPLS that serves as a base + framework for configuring and managing an MPLS switching + subsystem. It is expected that other MPLS technology YANG modules + (e.g., MPLS LSP Static, LDP, or RSVP-TE models) will augment the + MPLS base YANG module. + + BGP: + [IDR-BGP-MODEL] defines a YANG module for configuring and managing + BGP, including protocol, policy, and operational aspects based on + data center, carrier, and content provider operational + requirements. + + Routing Policy: + [RTGWG-POLICY] defines a YANG module for configuring and managing + routing policies based on operational practice. The module + provides a generic policy framework that can be augmented with + protocol-specific policy configuration. + + SR/SRv6: + [SPRING-SR-YANG] defines a YANG module for segment routing + configuration and operation. + + + BFD: + Bidirectional Forwarding Detection (BFD) [RFC5880] is a network + protocol that is used for liveness detection of arbitrary paths + between systems. [BFD-YANG] defines a YANG module that can be + used to configure and manage BFD. + + Multicast: + [PIM-YANG] defines a YANG module that can be used to configure and + manage Protocol Independent Multicast (PIM) devices. + + [RFC8652] defines a YANG module that can be used to configure and + manage Internet Group Management Protocol (IGMP) and Multicast + Listener Discovery (MLD) devices. + + [SNOOPING-YANG] defines a YANG module that can be used to + configure and manage Internet Group Management Protocol (IGMP) and + Multicast Listener Discovery (MLD) snooping devices. + + [MVPN-YANG] defines a YANG data model to configure and manage + Multicast in MPLS/BGP IP VPNs (MVPNs). + + PM: + [TWAMP-DATA-MODEL] defines a YANG data model for client and server + implementations of the Two-Way Active Measurement Protocol + (TWAMP). + + [STAMP-YANG] defines the data model for implementations of + Session-Sender and Session-Reflector for Simple Two-way Active + Measurement Protocol (STAMP) mode using YANG. + + [RFC8194] defines a YANG data model for Large-Scale Measurement + Platforms (LMAPs). + + ACL: + An Access Control List (ACL) is one of the basic elements used to + configure device-forwarding behavior. It is used in many + networking technologies such as Policy-Based Routing, firewalls, + etc. [RFC8519] describes a YANG data model of ACL basic building + blocks. + + QoS: + [QOS-MODEL] describes a YANG module of Differentiated Services for + configuration and operations. + + NAT: + For the sake of network automation and the need for programming + the Network Address Translation (NAT) function in particular, a + YANG data model for configuring and managing the NAT is essential. + + [RFC8512] defines a YANG module for the NAT function covering a + variety of NAT flavors such as Network Address Translation from + IPv4 to IPv4 (NAT44), Network Address and Protocol Translation + from IPv6 Clients to IPv4 Servers (NAT64), customer-side + translator (CLAT), Stateless IP/ICMP Translation (SIIT), Explicit + Address Mappings (EAMs) for SIIT, IPv6-to-IPv6 Network Prefix + Translation (NPTv6), and Destination NAT. + + [RFC8513] specifies a Dual-Stack Lite (DS-Lite) YANG module. + + Stateless Address Sharing: + [RFC8676] specifies a YANG module for Address plus Port (A+P) + address sharing, including Lightweight 4over6, Mapping of Address + and Port with Encapsulation (MAP-E), and Mapping of Address and + Port using Translation (MAP-T) softwire mechanisms. + +Acknowledgements + + Thanks to Joe Clark, Greg Mirsky, Shunsuke Homma, Brian Carpenter, + Adrian Farrel, Christian Huitema, Tommy Pauly, Ines Robles, and + Olivier Augizeau for the review. + + Many thanks to Robert Wilton for the detailed AD review. + + Thanks to Éric Vyncke, Roman Danyliw, Erik Kline, and Benjamin Kaduk + for the IESG review. + +Contributors + + Christian Jacquenet + Orange + Rennes, 35000 + France + + Email: Christian.jacquenet@orange.com + + + Luis Miguel Contreras Murillo + Telefonica + + Email: luismiguel.contrerasmurillo@telefonica.com + + + Oscar Gonzalez de Dios + Telefonica + Madrid + Spain + + Email: oscar.gonzalezdedios@telefonica.com + + + Weiqiang Cheng + China Mobile + + Email: chengweiqiang@chinamobile.com + + + Young Lee + Sung Kyun Kwan University + + Email: younglee.tx@gmail.com + + +Authors' Addresses + + Qin Wu (editor) + Huawei + 101 Software Avenue + Yuhua District + Nanjing + Jiangsu, 210012 + China + + Email: bill.wu@huawei.com + + + Mohamed Boucadair (editor) + Orange + Rennes 35000 + France + + Email: mohamed.boucadair@orange.com + + + Diego R. Lopez + Telefonica I+D + Spain + + Email: diego.r.lopez@telefonica.com + + + Chongfeng Xie + China Telecom + Beijing + China + + Email: xiechf@chinatelecom.cn + + + Liang Geng + China Mobile + + Email: gengliang@chinamobile.com |