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YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service (ACaaS)
draft-ietf-opsawg-teas-attachment-circuit-07

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This is an older version of an Internet-Draft whose latest revision state is "Active".
Authors Mohamed Boucadair , Richard Roberts , Oscar Gonzalez de Dios , Samier Barguil , Bo Wu
Last updated 2024-03-04 (Latest revision 2024-02-09)
Replaces draft-boro-opsawg-teas-attachment-circuit
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draft-ietf-opsawg-teas-attachment-circuit-07
OPSAWG                                                 M. Boucadair, Ed.
Internet-Draft                                                    Orange
Intended status: Standards Track                         R. Roberts, Ed.
Expires: 5 September 2024                                        Juniper
                                                           O. G. D. Dios
                                                              Telefonica
                                                           S. B. Giraldo
                                                                   Nokia
                                                                   B. Wu
                                                     Huawei Technologies
                                                            4 March 2024

  YANG Data Models for Bearers and 'Attachment Circuits'-as-a-Service
                                (ACaaS)
              draft-ietf-opsawg-teas-attachment-circuit-07

Abstract

   This document specifies a YANG service data model for Attachment
   Circuits (ACs).  This model can be used for the provisioning of ACs
   before or during service provisioning (e.g., Network Slice Service).
   The document also specifies a service model for managing bearers over
   which ACs are established.

   Also, the document specifies a set of reusable groupings.  Whether
   other service models reuse structures defined in the AC models or
   simply include an AC reference is a design choice of these service
   models.  Utilizing the AC service model to manage ACs over which a
   service is delivered has the advantage of decoupling service
   management from upgrading AC components to incorporate recent AC
   technologies or features.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Discussion of this document takes place on the Operations and
   Management Area Working Group Working Group mailing list
   (opsawg@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/opsawg/.

   Source for this draft and an issue tracker can be found at
   https://github.com/boucadair/attachment-circuit-model.

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Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on 5 September 2024.

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   Copyright (c) 2024 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
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   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
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   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Scope and Intended Use  . . . . . . . . . . . . . . . . .   3
     1.2.  Position ACaaS vs. Other Data Models  . . . . . . . . . .   6
       1.2.1.  Why Not Using the L2SM as Reference Data Model for
               ACaaS?  . . . . . . . . . . . . . . . . . . . . . . .   6
       1.2.2.  Why Not Using the L3SM as Reference Data Model for
               ACaaS?  . . . . . . . . . . . . . . . . . . . . . . .   7
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   7
   3.  Sample Uses of the Data Models  . . . . . . . . . . . . . . .   8
     3.1.  ACs Terminated by One or Multiple Customer Edges (CEs)  .   8
     3.2.  Separate AC Provisioning vs. Actual Service
           Provisioning  . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Description of the Data Models  . . . . . . . . . . . . . . .  11
     4.1.  The Bearer Service ("ietf-bearer-svc") YANG Module  . . .  11

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     4.2.  The Attachment Circuit Service ("ietf-ac-svc") YANG
           Module  . . . . . . . . . . . . . . . . . . . . . . . . .  15
       4.2.1.  Overall Structure . . . . . . . . . . . . . . . . . .  15
       4.2.2.  Service Profiles  . . . . . . . . . . . . . . . . . .  17
       4.2.3.  Attachment Circuits Profiles  . . . . . . . . . . . .  19
       4.2.4.  AC Placement Contraints . . . . . . . . . . . . . . .  19
       4.2.5.  Attachment Circuits . . . . . . . . . . . . . . . . .  20
   5.  YANG Modules  . . . . . . . . . . . . . . . . . . . . . . . .  42
     5.1.  The Bearer Service ("ietf-bearer-svc") YANG Module  . . .  42
     5.2.  The AC Service ("ietf-ac-svc") YANG Module  . . . . . . .  51
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  74
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  76
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  76
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  76
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  79
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .  82
     A.1.  Create A New Bearer . . . . . . . . . . . . . . . . . . .  82
     A.2.  Create An AC over An Existing Bearer  . . . . . . . . . .  83
     A.3.  Create An AC for a Known Peer SAP . . . . . . . . . . . .  85
     A.4.  One CE, Two ACs . . . . . . . . . . . . . . . . . . . . .  85
     A.5.  Control Precedence over Multiple ACs  . . . . . . . . . .  92
     A.6.  Create Multiple ACs Bound to Multiple CEs . . . . . . . .  93
     A.7.  Binding Attachment Circuits to an IETF Network Slice  . .  95
     A.8.  Connecting a Virtualized Environment Running in a Cloud
           Provider  . . . . . . . . . . . . . . . . . . . . . . . . 102
     A.9.  Connect Customer Network (CE) Through BGP . . . . . . . . 107
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 110
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . . 110
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . 110

1.  Introduction

1.1.  Scope and Intended Use

   Connectivity services are provided by networks to customers via
   dedicated terminating points, such as Service Functions [RFC7665],
   customer edges (CEs), peer Autonomous System Border Routers (ASBRs),
   data centers gateways, or Internet Exchange Points.  A connectivity
   service is basically about ensuring data transfer received from or
   destined to a given terminating point to or from other terminating
   points within the same customer/service, an interconnection node, or
   an ancillary node.  The objectives for the connectivity service can
   be negotiated and agreed upon between the customer and the network
   provider.  To facilitate data transfer within the provider network,
   it is assumed that the appropriate setup is provisioned over the
   links that connect customer terminating points and a provider
   network, allowing successfully data exchanged over these links.  The
   required setup is referred to in this document as Attachment Circuits

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   (ACs), while the underlying link is referred to as "bearers".

   This document adheres to the definition of an Attachment Circuit as
   provided in Section 1.2 of [RFC4364], especially:

      Routers can be attached to each other, or to end systems, in a
      variety of different ways: PPP connections, ATM Virtual Circuits
      (VCs), Frame Relay VCs, ethernet interfaces, Virtual Local Area
      Networks (VLANs) on ethernet interfaces, GRE tunnels, Layer 2
      Tunneling Protocol (L2TP) tunnels, IPsec tunnels, etc.  We will
      use the term "attachment circuit" to refer generally to some such
      means of attaching to a router.  An attachment circuit may be the
      sort of connection that is usually thought of as a "data link", or
      it may be a tunnel of some sort; what matters is that it be
      possible for two devices to be network layer peers over the
      attachment circuit.

   When a customer requests a new value-added service, the service can
   be bound to existing attachment circuits or trigger the instantiation
   of new attachment circuits.  The provisioning of a value-added
   service should, thus, accommodate both deployments.

   Also, because the instantiation of an attachment circuit requires
   coordinating the provisioning of endpoints that might not belong to
   the same administrative entity (customer vs. provider or distinct
   operational teams within the same provider, etc.), *providing
   programmatic means to expose 'attachment circuits'-as-a-service will
   greatly simplify the provisioning of value-added services* delivered
   over an attachment circuits.  For example, management systems of
   adjacent domains that need to connect via an AC will use such means
   to agree on the resources that are required for the activation of
   both sides of an AC (e.g., Layer 2 tags, IP address family, or IP
   subnets).

   This document specifies a YANG service data model ("ietf-ac-svc") for
   managing attachment circuits that are exposed by a network to its
   customers, such as an enterprise site, a network function, a hosting
   infrastructure, or a peer network provider.  The model can be used
   for the provisioning of ACs prior or during advanced service
   provisioning (e.g., Network Slice Service).

   The "ietf-ac-svc" module (Section 5.2) includes a set of reusable
   groupings.  Whether a service model reuses structures defined in the
   "ietf-ac-svc" or simply includes an AC reference (that was
   communicated during AC service instantiation) is a design choice of
   these service models.  Relying upon the AC service model to manage
   ACs over which services are delivered has the merit to decorrelate
   the management of the (core) service vs. upgrade the AC components to

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   reflect recent AC technologies or new features (e.g., new encryption
   scheme, additional routing protocol). *This document favors the
   approach of completely relying upon the AC service model instead of
   duplicating data nodes into specific modules of advanced services
   that are delivered over an Attachment Circuit.*

   Since the provisioning of an AC requires a bearer to be in place,
   this document introduces a new module called "ietf-bearer-svc" that
   enables customers to manage their bearer requests (Section 5.1).  The
   customers can then retrieve a provider-assigned bearer reference that
   they will include in their AC service requests.  Likewise, the
   customer may retrieve whether this bearer supports a synchronization
   mechanism such as Sync Ethernet (SyncE) [ITU-T-G.781].  An example to
   retrieve a bearer reference is provided in Appendix A.1.

   An AC service request can provide a reference to a bearer or a set of
   peer SAPs.  Both schemes are supported in the AC service model.  When
   several bearers are available, the AC service request may filter them
   based on the bearer type, synchronization support, etc.

   Each AC is identified with a unique identifier within a (provider)
   domain.  From a network provider standpoint, an AC can be bound to a
   single or multiple Service Attachment Points (SAPs) [RFC9408].
   Likewise, the same SAP can be bound to one or multiple ACs.  However,
   the mapping between an AC and a PE in the provider network that
   terminates that AC is hidden to the application that makes use of the
   AC service model.  Such mapping information is internal to the
   network controllers.  As such, the details about the (node-specific)
   attachment interfaces are not exposed in the AC service model.

   The AC service model *does not make any assumptions about the
   internal structure or even the nature or the services that will be
   delivered over an attachment circuit or a set of attachment
   circuits*. Customers do not have access to that network view other
   than the ACs that the ordered.  For example, the AC service model can
   be used to provision a set of ACs to connect multiple sites (Site1,
   Site2, ..., SiteX) for customer who also requested VPN services.  If
   these provisioning of these services require specific configuration
   on ASBR nodes, such configuration is handled at the network level and
   is not exposed to the customer at the service level.  However, the
   network controller will have access to such a view as the service
   points in these ASBRs will be exposed as SAPs with "role" set to
   "ietf-sap-ntw:nni" [RFC9408].

   The AC service model can be used in a variety of contexts, such as
   (but not limited to) those provided in Appendix A:

   *  Create an AC over an existing bearer Appendix A.2.

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   *  Request an attachment circuit for a known peer SAP (Appendix A.3).

   *  Instantiate multiple attachment circuits over the same bearer
      (Appendix A.4).

   *  Control the precedence over multiple attachment circuits
      (Appendix A.5).

   *  Create Multiple ACs bound to Multiple CEs (Appendix A.6).

   *  Bind a slice service to a set of pre-provisioned attachment
      circuits (Appendix A.7).

   *  Connect a Cloud Infrastructure to a service provider network
      (Appendix A.8).  Note that the AC model can be used between
      service providers for other interconnection purposes.

   The examples provided in Appendix A use the IPv4 address blocks
   reserved for documentation [RFC5737], the IPv6 prefix reserved for
   documentation [RFC3849], and the Autonomous System (AS) numbers
   reserved for documentation [RFC5398].

   The YANG data models in this document conform to the Network
   Management Datastore Architecture (NMDA) defined in [RFC8342].

1.2.  Position ACaaS vs. Other Data Models

   The AC model specified in this document *is not a network model*
   [RFC8969].  As such, the model does not expose details related to
   specific nodes in the provider's network that terminate an AC (e.g.,
   network node identifiers).  The mapping between an AC as seen by a
   customer and the network implementation of an AC is maintained by the
   network controllers and is not exposed to the customer.  This mapping
   can be maintained using a variety of network models, such as
   augmented SAP AC network model
   [I-D.ietf-opsawg-ntw-attachment-circuit].

   The AC service model *is not a device model*. A network provider may
   use a variety of device models (e.g., Routing management [RFC8349] or
   BGP [I-D.ietf-idr-bgp-model]) to provision an AC service in relevant
   network nodes.

1.2.1.  Why Not Using the L2SM as Reference Data Model for ACaaS?

   The L2SM [RFC8466] covers some AC-related considerations.
   Nevertheless, the L2SM structure is primarily focused on Layer 2
   aspects.  For example, the L2SM does not cover Layer 3 provisioning,
   which is required for the typical AC instantiation.

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1.2.2.  Why Not Using the L3SM as Reference Data Model for ACaaS?

   Like the L2SM, the L3SM [RFC8299] addresses certain AC-related
   aspects.  However, the L3SM structure does not sufficiently address
   Layer 2 provisioning requirements.  Additionally, the L3SM is
   primarily designed for conventional L3VPN deployments and, as such,
   has some limitations for instantiating ACs in other deployment
   contexts (e.g., cloud environments).  For example, the L3SM does not
   provide the capability to provision multiple BGP peer groups over the
   same AC.

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The meanings of the symbols in the YANG tree diagrams are defined in
   [RFC8340].

   This document uses the following terms:

   Bearer:  A physical or logical link that connects a customer node (or
      site) to a provider network.  A bearer can be a wireless or wired
      link.  One or multiple technologies can be used to build a bearer.
      The bearer type can be specified by a customer.

      The operator allocates a unique bearer reference to identify a
      bearer within its network (e.g., customer line identifier).  Such
      a reference can be retrieved by a customer and used in subsequent
      service placement requests to unambiguously identify where a
      service is to be bound.

      The concept of bearer can be generalized to refer to the required
      underlying connection for the provisioning of an attachment
      circuit.  One or multiple attachment circuits may be hosted over
      the same bearer (e.g., multiple VLANs on the same bearer that is
      provided by a physical link).

   Network controller:  Denotes a functional entity responsible for the
      management of the service provider network.

   Service orchestrator:  Refers to a functional entity that interacts

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      with the customer of a network service.  The service orchestrator
      is typically responsible for the attachment circuits, the Provider
      Edge (PE) selection, and requesting the activation of the
      requested service to a network controller.

   Service provider network:  A network that is able to provide network
      services (e.g., Layer 2 VPN, Layer 3, and Network Slice Services).

   Service provider:  A service provider that offers network services
      (e.g., Layer 2 VPN, Layer 3, and Network Slice Services).

3.  Sample Uses of the Data Models

3.1.  ACs Terminated by One or Multiple Customer Edges (CEs)

   Figure 1 depicts two target topology flavors that involve ACs.  These
   topologies have the following characteristics:

   *  A Customer Edges (CEs) can be either a physical device or a
      logical entity.  Such logical entity is typically a software
      component (e.g., a virtual service function that is hosted within
      the provider's network or a third-party infrastructure).  A CE is
      seen by the network as a peer SAP.

   *  An AC service request may include one or multiple ACs, which may
      be associated to a single CE or multiple CEs.

   *  CEs may be either dedicated to one single connectivity service or
      host multiple connectivity services (e.g., CEs with roles of
      service functions [RFC7665]).

   *  A network provider may bind a single AC to one or multiple peer
      SAPs (e.g., CE#1 and CE#2 are tagged as peer SAPs for the same
      AC).  For example, and as discussed in [RFC4364], multiple CEs can
      be attached to a PE over the same attachment circuit.  This
      scenario is typically implemented when the Layer 2 infrastructure
      between the CE and the network is a multipoint service.

   *  A single CE may terminate multiple ACs, which can be associated
      with the same bearer or distinct bearers.

   *  Customers may request protection schemes in which the ACs
      associated with their endpoints are terminated by the same PE
      (e.g., CE#3), distinct PEs (e.g., CE#34), etc.  The network
      provider uses this request to decide where to terminate the AC in
      the network provider network and also whether to enable specific
      capabilities (e.g., Virtual Router Redundancy Protocol (VRRP)).

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     .-------.                .--------------------.         .-------.
     │       +------.         |                    +---AC----+       |
     │ CE#1  │      |         |                    +---AC----+ CE#3  |
     '-------'      |         |                    |         '-------'
                    +---AC----+     Network        |
     .-------.      |         |                    |
     |       |      |         |                    |         .-------.
     | CE#2  +------'         |                    +---AC----+ CE#4  |
     '-------'                |                    |         '----+--'
                              '-----------+--------'              |
                                          |                       |
                                          '-----------AC----------'

                         Figure 1: Examples of ACs

3.2.  Separate AC Provisioning vs. Actual Service Provisioning

   The procedure to provision a service in a service provider network
   may depend on the practices adopted by a service provider.  This
   includes the flow put in place for the provisioning of advanced
   network services and how they are bound to an attachment circuit.
   For example, a single attachment circuit may be used to host multiple
   connectivity services.  In order to avoid service interference and
   redundant information in various locations, a service provider may
   expose an interface to manage ACs network-wide.  Customers can then
   request a bearer or an attachment circuit to be put in place, and
   then refer to that bearer or AC when requesting services that are
   bound to the bearer or AC.

   Figure 2 shows the positioning of the AC service model is the overall
   service delivery process.

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                               .---------------.
                               |   Customer    |
                               '-------+-------'
               Customer Service Model  |
               e.g., slice-svc, ac-svc,| and bearer-svc
                               .-------+-------.
                               |    Service    |
                               | Orchestration |
                               '-------+-------'
                Network Model          |
       e.g., l3vpn-ntw, sap, and ac-ntw|
                               .-------+-------.
                               |   Network     |
                               | Orchestration |
                               '-------+-------'
         Network Configuration Model   |
                           .-----------+-----------.
                           |                       |
                  .--------+------.       .--------+------.
                  |    Domain     |       |     Domain    |
                  | Orchestration |       | Orchestration |
                  '---+-----------'       '--------+------'
       Device         |        |                   |
       Configuration  |        |                   |
       Model          |        |                   |
                 .----+----.   |                   |
                 | Config  |   |                   |
                 | Manager |   |                   |
                 '----+----'   |                   |
                      |        |                   |
                      | NETCONF/CLI..................
                      |        |                   |
                    .--------------------------------.
      .----. Bearer |                                | Bearer .----.
      |CE#1+--------+            Network             +--------+CE#2|
      '----'        |                                |        '----'
                    '--------------------------------'
       Site A                                                  Site B

                   Figure 2: An Example of AC Model Usage

   In order to ease the mapping between the service model and underlying
   network models (e.g., L3NM, SAP), the name conventions used in
   existing network data models are reused as much as possible.  For
   example, "local-address" is used rather than "provider-address" (or
   similar) to refer to an IP address used in the provider network.
   This approach is consistent with the automation framework defined in
   [RFC8969].

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4.  Description of the Data Models

4.1.  The Bearer Service ("ietf-bearer-svc") YANG Module

   Figure 3 shows the tree for managing the bearers (that is, the
   properties of an attachment that are below Layer 3).  A bearer can be
   a physical or logical link (e.g., Link Aggregation Group (LAG)
   [IEEE802.1AX]).  Also, a bearer can be a wireless or wired link.  A
   reference to a bearer is generated by the operator.  Such a reference
   can be used, e.g., in a subsequent service request to create an AC.
   The anchoring of the AC can also be achieved by indicating (with or
   without a bearer reference), a peer SAP identifier (e.g., an
   identifier of a Service Function).

  module: ietf-bearer-svc

    +--rw bearers
       +--rw placement-constraints
       |  +--rw constraint* [constraint-type]
       |          {vpn-common:placement-diversity}?
       |     +--rw constraint-type    identityref
       |     +--rw target
       |        +--rw (target-flavor)?
       |           +--:(id)
       |           |  +--rw group* [group-id]
       |           |     +--rw group-id    string
       |           +--:(all-bearers)
       |           |  +--rw all-other-bearers?   empty
       |           +--:(all-groups)
       |              +--rw all-other-groups?    empty
       +--rw bearer* [name]
          +--rw name                 string
          +--rw description?         string
          +--rw groups
          |  +--rw group* [group-id]
          |     +--rw group-id    string
          +--rw op-comment?          string
          +--rw bearer-parent-ref?   bearer-svc:bearer-ref
          +--ro bearer-lag-member*   bearer-svc:bearer-ref
          +--ro sync-phy-capable?    boolean
          +--rw sync-phy-enabled?    boolean
          +--rw sync-phy-type?       identityref
          +--rw customer-point
          |  +--rw identified-by?   identityref
          |  +--rw device
          |  |  +--rw device-id?   string
          |  |  +--rw location
          |  |     +--rw location-name?   string

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          |  |     +--rw address?         string
          |  |     +--rw postal-code?     string
          |  |     +--rw state?           string
          |  |     +--rw city?            string
          |  |     +--rw country-code?    string
          |  +--rw site
          |  |  +--rw site-id?    string
          |  |  +--rw location
          |  |     +--rw location-name?   string
          |  |     +--rw address?         string
          |  |     +--rw postal-code?     string
          |  |     +--rw state?           string
          |  |     +--rw city?            string
          |  |     +--rw country-code?    string
          |  +--rw custom-id?       string
          +--rw type?                identityref
          +--rw test-only?           empty
          +--ro bearer-reference?    string
          |       {vpn-common:bearer-reference}?
          +--ro ac-svc-ref*          ac-svc:attachment-circuit-reference
          +--rw requested-start?     yang:date-and-time
          +--rw requested-stop?      yang:date-and-time
          +--ro actual-start?        yang:date-and-time
          +--ro actual-stop?         yang:date-and-time
          +--rw status
             +--rw admin-status
             |  +--rw status?        identityref
             |  +--ro last-change?   yang:date-and-time
             +--ro oper-status
                +--ro status?        identityref
                +--ro last-change?   yang:date-and-time

                 Figure 3: Bearer Service Tree Structure

   The same customer site (CE, NF, etc.) can terminate one or multiple
   bearers; each of them uniquely identified by a reference that is
   assigned by the network provider.  These bearers can terminate on the
   same or distinct network nodes.  CEs that terminate multiple bearers
   are called multi-homed CEs.

   A bearer can be created, modified, or discovered from the network.
   For example, the following deployment options can be considered:

   Greenfield creation:  In this scenario, bearers are created from
      scratch using specific requests made to a network controller.
      This method allows providers to tailor bearer creation to meet
      customer-specific needs.  For example, a bearer request may
      indicate some hints about the placement constraints ('placement-

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      constraints').  These constraints are used by a provider to
      determine how/where to terminate a bearer in the network side
      (e.g., PoP/PE selection).

   Auto-discovery using network protocols:  Devices can use specific
      protocols (e.g., Link Layer Discovery Protocol (LLDP)) to
      automatically discover and connect to available network resources.
      A network controller can use such reported information to expose
      discovered bearers from the network using the same bearer data
      model structure.

   A request to create a bearer may include a set of constraints
   ("placement-constraints") that are used by a controller to decide the
   network terminating side of a bearer (e.g., PE selection, PE
   redundancy, or PoP selection).  Future placement criteria
   ("constraint-type") may be defined in the future to accommodate
   specific deployment contexts.

   The descriptions of the bearer data nodes are as follows:

   'name':  Used to uniquely identify a bearer.  This name is typically
      selected by the client when requesting a bearer.

   'description':  Includes a textual description of the bearer.

   'group':  Tags a bearer with one ore more identifiers that are used
      to group a set of bearers.

   'op-comment':  Includes operational comments that may be useful for
      managing the bearer (building, level, etc.).  No structure is
      associated with this data node to accommodate all deployments.

   'bearer-parent-ref':  Specifies the parent bearer.  This data node
      can be used, e.g., if a bearer is a member of a LAG.

   'bearer-lag-member':  Lists the bearers that are members of a LAG.
      Members can be declared as part of a LAG using 'bearer-parent-
      ref'.

   'sync-phy-capable':  Reports whether a synchronization physical (Sync
      PHY) mechanism is supported for this bearer.

   'sync-phy-enabled':  Indicates whether a Sync PHY mechanism is
      enabled for a bearer.  Only applies when 'sync-phy-capable' is set
      to 'true'.

   'sync-phy-type':  Specifies the Sync PHY mechanism (e.g., SynchE
      [ITU-T-G.781]) enabled for the bearer.

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   'customer-point':  Specifies the customer terminating point for the
      bearer.  A bearer request can indicate a device, a site, a
      combination thereof, or a custom information when requesting a
      bearer.  All these schemes are supported in the model.

   'type':  Specifies the bearer type (Ethernet, wireless, LAG, etc.).

   'test-only':  Indicates that a request is only for test and not for
      setting, even if there are no errors.  This is used for
      feasibility checks.  This data node is applicable only when the
      data model is used with protocols which do not natively support
      such option.  For example, this data node is redundant with the
      "test-only" value of the <test-option> parameter in the NETCONF
      <edit-config> operation (Section 7.2 of [RFC6241]).

   'bearer-reference':  Returns an internal reference for the service
      provider to uniquely identify the bearer.  This reference can be
      used when requesting services.  Appendix A.1 provides an example
      about how this reference can be retrieved by a customer.

      Whether the 'bearer-reference' mirrors the content of the 'name'
      is deployment-specific.  The module does not assume nor preclude
      such schemes.

   'ac-svc-ref':  Specifies the set of attachment circuits that are
      bound to the bearer.

   'requested-start':  Specifies the requested date and time when the
      bearer is expected to be active.

   'requested-stop':  Specifies the requested date and time when the
      bearer is expected to be disabled.

   'actual-start':  Reports the actual date and time when the bearer
      actually was enabled.

   'actual-stop':  Reports the actual date and time when the bearer
      actually was disabled.

   'status':  Used to track the overall status of a given bearer.  Both
      operational and administrative status are maintained together with
      a timestamp.

      The "admin-status" attribute is typically configured by a network

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      operator to indicate whether the service is enabled, disabled, or
      subjected to additional testing or pre-deployment checks.  These
      additional options, such as 'admin-testing' and 'admin-pre-
      deployment', provide the operators the flexibility to conduct
      additional validations on the bearer before deploying services
      over that connection.

   'oper-status':  The "oper-status" of a bearer reflects its
      operational state as observed.  As a bearer can contain multiple
      services, the operational status should only reflect the status of
      the bearer connection.  To obtain network-level service status,
      specific network models such as those in Section 7.3 of [RFC9182]
      or Section 7.3 of [RFC9291] should be consulted.

      It is important to note that the "admin-status" attribute should
      remain independent of the "oper-status".  In other words, the
      setting of the intended administrative state (e.g., whether
      "admin-up" or "admin-testing") MUST NOT be influenced by the
      current operational state.  If the bearer is administratively set
      to 'admin-down', it is expected that the bearer will also be
      operationally 'op-down' as a result of this administrative
      decision.

      To assess the service delivery status for a given bearer
      comprehensively, it is recommended to consider both administrative
      and operational service status values in conjunction.  This
      holistic approach allows a network controller or operator to
      identify anomalies effectively.

      For instance, when a bearer is administratively enabled but the
      "operational-status" of that bearer is reported as "op-down", it
      should be expected that the "oper-status" of services transported
      over that bearer is also down.  If these status values differ, a
      trigger to detect an anomaly.

      See [RFC9181] for more details.

4.2.  The Attachment Circuit Service ("ietf-ac-svc") YANG Module

   The full tree diagram of the module can be generated using the
   "pyang" tool [PYANG].  That tree is not included here because it is
   too long (Section 3.3 of [RFC8340]).  Instead, subtrees are provided
   for the reader's convenience.

4.2.1.  Overall Structure

   The overall tree structure of the AC service module is shown in
   Figure 4.

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                    +--rw specific-provisioning-profiles
                    |  ...
                    +--rw service-provisioning-profiles
                    |  ...
                    +--rw attachment-circuits
                       +--rw ac-group-profile* [name]
                       |  ...
                       +--rw placement-constraints
                       |  ...
                       +--rw ac* [name]
                          ...
                          +--rw l2-connection
                          |  ...
                          +--rw ip-connection
                          |  ...
                          +--rw routing-protocols
                          |  ...
                          +--rw oam
                          |  ...
                          +--rw security
                          |  ...
                          +--rw service
                             ...

                Figure 4: Overall AC Service Tree Structure

   The rationale for deciding whether a reusable grouping should be
   maintained in this document or be moved into the AC common module
   [I-D.ietf-opsawg-teas-common-ac] is as follows:

   *  Groupings that are reusable among the AC service module, AC
      network module, other service models, and network models are
      included in the AC common module.

   *  Groupings that are reusable only by other service models are
      maintained in the "ietf-ac-svc" module.

   Each AC is identified with a unique name ('../ac/name') within a
   domain.  The mapping between this AC and a local PE that terminates
   the AC is hidden to the application that makes use of the AC service
   model.  This information is internal to the Network controller.  As
   such, the details about the (node-specific) attachment interfaces are
   not exposed in this service model.

   The AC service model uses groupings and types defined in the AC
   common model [I-D.ietf-opsawg-teas-common-ac].  Therefore, the
   description of these nodes are not reiterated in the following
   subsections.

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4.2.2.  Service Profiles

4.2.2.1.  Description

   The 'specific-provisioning-profiles' container (Figure 5) can be used
   by a service provider to maintain a set of reusable profiles.  The
   profiles definition are similar to those defined in [RFC9181],
   including: Quality of Service (QoS), Bidirectional Forwarding
   Detection (BFD), forwarding, and routing profiles.  The exact
   definition of the profiles is local to each service provider.  The
   model only includes an identifier for these profiles in order to
   facilitate identifying and binding local policies when building an
   AC.

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             module: ietf-ac-svc
               +--rw specific-provisioning-profiles
               |  +--rw valid-provider-identifiers
               |     +--rw encryption-profile-identifier* [id]
               |     |  +--rw id    string
               |     +--rw qos-profile-identifier* [id]
               |     |  +--rw id    string
               |     +--rw bfd-profile-identifier* [id]
               |     |  +--rw id    string
               |     +--rw forwarding-profile-identifier* [id]
               |     |  +--rw id    string
               |     +--rw routing-profile-identifier* [id]
               |        +--rw id    string
               +--rw service-provisioning-profiles
               |  +--rw service-profile-identifier* [id]
               |     +--rw id    string
               +--rw attachment-circuits
                  +--rw ac-group-profile* [name]
                  |  ...
                  +--rw placement-constraints
                  |  ...
                  +--rw ac* [name]
                     ...
                     +--rw l2-connection
                     |  ...
                     +--rw ip-connection
                     |  ...
                     +--rw routing-protocols
                     |  ...
                     +--rw oam
                     |  ...
                     +--rw security
                     |  ...
                     +--rw service
                        ...

                         Figure 5: Service Profiles

   As shown in Figure 5, two profile types can be defined: 'specific-
   provisioning-profiles' and 'service-provisioning-profiles'.  Whether
   only specific profiles, service profiles, or a combination thereof
   are used is local to each service provider.

   The following specific provisioning profiles can be defined:

   'encryption-profile-identifier':  Refers to a set of policies related
      to the encryption setup that can be applied when provisioning an
      AC.

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   'qos-profile-identifier':  Refers to a set of policies, such as
      classification, marking, and actions (e.g., [RFC3644]).

   'bfd-profile-identifier':  Refers to a set of Bidirectional
      Forwarding Detection (BFD) policies [RFC5880] that can be invoked
      when building an AC.

   'forwarding-profile-identifier':  Refers to the policies that apply
      to the forwarding of packets conveyed within an AC.  Such policies
      may consist, for example, of applying Access Control Lists (ACLs).

   'routing-profile-identifier':  Refers to a set of routing policies
      that will be invoked (e.g., BGP policies) when building an AC.

4.2.2.2.  Referencing Service/Specific Profiles

   All the abovementioned profiles are uniquely identified by the
   NETCONF/RESTCONF server by an identifier.  To ease referencing these
   profiles by other data models, specific typedefs are defined for each
   of these profiles.  Likewise, an attachment circuit reference typedef
   is defined when referencing a (global) attachment circuit by its name
   is required.  These typedefs SHOULD be used when other modules need a
   reference to one of these profiles or attachment circuits.

4.2.3.  Attachment Circuits Profiles

   The 'ac-group-profile' defines reusable parameters for a set of ACs.
   Each profile is identified by 'name'.  Some of the data nodes can be
   adjusted at the 'ac'.  These adjusted values take precedence over the
   global values.  The structure of 'ac-group-profile' is similar to the
   one used to model each 'ac' (Figure 7).

4.2.4.  AC Placement Contraints

   The 'placement-constraints' specifies the placement constraints of an
   AC.  For example, this container can be used to request avoiding to
   connecting two ACs to the same PE.  The full set of supported
   constraints is defined in [RFC9181] (see 'placement-diversity', in
   particular).

   The structure of 'placement-constraints' is shown in Figure 6.

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             +--rw specific-provisioning-profiles
             |  ...
             +--rw service-provisioning-profiles
             |  ...
             +--rw attachment-circuits
                +--rw ac-group-profile* [name]
                |  ...
                +--rw placement-constraints
                |  +--rw constraint* [constraint-type]
                |     +--rw constraint-type    identityref
                |     +--rw target
                |        +--rw (target-flavor)?
                |           +--:(id)
                |           |  +--rw group* [group-id]
                |           |     +--rw group-id    string
                |           +--:(all-accesses)
                |           |  +--rw all-other-accesses?   empty
                |           +--:(all-groups)
                |              +--rw all-other-groups?     empty
                +--rw ac* [name]
                   ...

             Figure 6: Placement Constraints Subtree Structure

4.2.5.  Attachment Circuits

   The structure of 'attachment-circuits' is shown in Figure 7.

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    +--rw specific-provisioning-profiles
    |  ...
    +--rw service-provisioning-profiles
    |  ...
    +--rw attachment-circuits
       +--rw ac-group-profile* [name]
       |  ...
       +--rw placement-constraints
       |  ...
       +--rw ac* [name]
          +--rw customer-name?       string
          +--rw description?         string
          +--rw test-only?          empty
          +--rw requested-start?     yang:date-and-time
          +--rw requested-stop?      yang:date-and-time
          +--ro actual-start?        yang:date-and-time
          +--ro actual-stop?         yang:date-and-time
          +--rw peer-sap-id*         string
          +--rw ac-group-profile*    ac-group-reference
          +--rw ac-parent-ref?       ac-svc:attachment-circuit-reference
          +--ro child-ac-ref*        ac-svc:attachment-circuit-reference
          +--rw group* [group-id]
          |  +--rw group-id      string
          |  +--rw precedence?   identityref
          +--ro service-ref* [service-type service-id]
          |  +--ro service-type    identityref
          |  +--ro service-id      string
          +--rw name                 string
          +--rw service-profile*     service-profile-reference
          +--rw l2-connection
          |  ...
          +--rw ip-connection
          |  ...
          +--rw routing-protocols
          |  ...
          +--rw oam
          |  ...
          +--rw security
          |  ...
          +--rw service
             ...

               Figure 7: Attachment Circuits Tree Structure

   The description of the data nodes is as follows:

   'customer-name':  Indicates the name of the customer who ordered the
      AC.

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   'description':  Includes a textual description of the AC.

   'test-only':  Indicates that a request is only for test and not for
      setting, even if there are no errors.  This is used for
      feasibility checks.  This data node is applicable only when the
      data model is used with protocols which do not natively support
      such option.

   'requested-start':  Specifies the requested date and time when the
      attachment circuit is expected to be active.

   'requested-stop':  Specifies the requested date and time when the
      attachment circuit is expected to be disabled.

   'actual-start':  Reports the actual date and time when the attachment
      circuit actually was enabled.

   'actual-stop':  Reports the actual date and time when the attachment
      circuit actually was disabled.

   'peer-sap-id':  Includes references to the remote endpoints of an
      attachment circuit [RFC9408].

   'ac-group-profile':  Indicates references to one or more profiles
      that are defined in Section 4.2.3.

   'ac-parent-ref':  Specifies an AC that is inherited by an attachment
      circuit.

      In contexts where dynamic terminating points are managed for a
      given AC, a parent AC can be defined with a set of stable and
      common information, while "child" ACs are defined to track dynamic
      information.  These "child" ACs are bound to the parent AC, which
      is exposed to services (as a stable reference).

      Whenever a parent AC is deleted, all its "child" ACs MUST be
      deleted.

   'child-ac-ref':  Lists one or more references of child ACs that rely
      upon this attachment circuit as a parent AC.

   'group':  Lists the groups to which an AC belongs [RFC9181].  For
      example, the 'group-id' is used to associate redundancy or
      protection constraints of ACs.  An example is provided in
      Appendix A.5.

   'service-ref':  Reports the set of services that are bound to the
      attachment circuit.  The services are indexed by their type.

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   'name':  Associates a name that uniquely identifies an AC within a
      service provider network.

   'service-profile':  References a set of service-specific profiles.

   'l2-connection':  See Section 4.2.5.1.

   'ip-connection':  See Section 4.2.5.2.

   'routing':  See Section 4.2.5.3.

   'oam':  See Section 4.2.5.7.

   'security':  See Section 4.2.5.8.

   'service':  See Section 4.2.5.9.

4.2.5.1.  Layer 2 Connection Structure

   The 'l2-connection' container (Figure 8) is used to configure the
   relevant Layer 2 properties of an AC including: encapsulation details
   and tunnel terminations.  For the encapsulation details, the model
   supports the definition of the type as well as the Identifiers (e.g.,
   VLAN-IDs) of each of the encapsulation-type defined.  For the second
   case, attributes for pseudowire, Virtual Private LAN Service (VPLS),
   and Virtual eXtensible Local Area Network (VXLAN) tunnel terminations
   are included.

   'bearer-reference' is used to link an AC with a bearer over which the
   AC is instantiated.

   This structure relies upon the common groupings defined in
   [I-D.ietf-opsawg-teas-common-ac].

        +--rw specific-provisioning-profiles
        |  ...
        +--rw service-provisioning-profiles
        |  ...
        +--rw attachment-circuits
           +--rw ac-group-profile* [name]
           |  ...
           +--rw placement-constraints
           |  ...
           +--rw ac* [name]
              ...
              +--rw name                 string
              +--rw l2-connection
              |  +--rw encapsulation

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              |  |  +--rw type?              identityref
              |  |  +--rw dot1q
              |  |  |  +--rw tag-type?   identityref
              |  |  |  +--rw cvlan-id?   uint16
              |  |  +--rw priority-tagged
              |  |  |  +--rw tag-type?   identityref
              |  |  +--rw qinq
              |  |     +--rw tag-type?   identityref
              |  |     +--rw svlan-id    uint16
              |  |     +--rw cvlan-id    uint16
              |  +--rw (l2-service)?
              |  |  +--:(l2-tunnel-service)
              |  |  |  +--rw l2-tunnel-service
              |  |  |     +--rw type?         identityref
              |  |  |     +--rw pseudowire
              |  |  |     |  +--rw vcid?      uint32
              |  |  |     |  +--rw far-end?   union
              |  |  |     +--rw vpls
              |  |  |     |  +--rw vcid?      uint32
              |  |  |     |  +--rw far-end*   union
              |  |  |     +--rw vxlan
              |  |  |        +--rw vni-id             uint32
              |  |  |        +--rw peer-mode?         identityref
              |  |  |        +--rw peer-ip-address*   inet:ip-address
              |  |  +--:(l2vpn)
              |  |     +--rw l2vpn-id?            vpn-common:vpn-id
              |  +--rw bearer-reference?          string
              |          {vpn-common:bearer-reference}?
              +--rw ip-connection
              |  ...
              +--rw routing-protocols
              |  ...
              +--rw oam
              |  ...
              +--rw security
              |  ...
              +--rw service
                 ...

                Figure 8: Layer 2 Connection Tree Structure

4.2.5.2.  IP Connection Structure

   The 'ip-connection' container is used to configure the relevant IP
   properties of an AC.  The model supports the usage of dynamic and
   static addressing.  This structure relies upon the common groupings
   defined in [I-D.ietf-opsawg-teas-common-ac].  Both IPv4 and IPv6
   parameters are supported.

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   Figure 9 shows the structure of the IPv4 connection.

            | ...
            +--rw ip-connection
            |  +--rw ipv4 {vpn-common:ipv4}?
            |  |  +--rw local-address?
            |  |  |       inet:ipv4-address
            |  |  +--rw virtual-address?
            |  |  |       inet:ipv4-address
            |  |  +--rw prefix-length?                           uint8
            |  |  +--rw address-allocation-type?
            |  |  |       identityref
            |  |  +--rw (allocation-type)?
            |  |     +--:(dynamic)
            |  |     |  +--rw (address-assign)?
            |  |     |  |  +--:(number)
            |  |     |  |  |  +--rw number-of-dynamic-address?   uint16
            |  |     |  |  +--:(explicit)
            |  |     |  |     +--rw customer-addresses
            |  |     |  |        +--rw address-pool* [pool-id]
            |  |     |  |           +--rw pool-id          string
            |  |     |  |           +--rw start-address
            |  |     |  |           |       inet:ipv4-address
            |  |     |  |           +--rw end-address?
            |  |     |  |                   inet:ipv4-address
            |  |     |  +--rw (provider-dhcp)?
            |  |     |  |  +--:(dhcp-service-type)
            |  |     |  |     +--rw dhcp-service-type?
            |  |     |  |             enumeration
            |  |     |  +--rw (dhcp-relay)?
            |  |     |     +--:(customer-dhcp-servers)
            |  |     |        +--rw customer-dhcp-servers
            |  |     |           +--rw server-ip-address*
            |  |     |                   inet:ipv4-address
            |  |     +--:(static-addresses)
            |  |        +--rw address* [address-id]
            |  |           +--rw address-id          string
            |  |           +--rw customer-address?   inet:ipv4-address
            |  +--rw ipv6 {vpn-common:ipv6}?
            |     ...

             Figure 9: Layer 3 Connection Tree Structure (IPv4)

   Figure 10 shows the structure of the IPv6 connection.

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            | ...
            +--rw ip-connection
            |  +--rw ipv4 {vpn-common:ipv4}?
            |  |  ...
            |  +--rw ipv6 {vpn-common:ipv6}?
            |     +--rw local-address?
            |     |       inet:ipv6-address
            |     +--rw virtual-address?
            |     |       inet:ipv6-address
            |     +--rw prefix-length?                           uint8
            |     +--rw address-allocation-type?
            |     |       identityref
            |     +--rw (allocation-type)?
            |        +--:(dynamic)
            |        |  +--rw (address-assign)?
            |        |  |  +--:(number)
            |        |  |  |  +--rw number-of-dynamic-address?   uint16
            |        |  |  +--:(explicit)
            |        |  |     +--rw customer-addresses
            |        |  |        +--rw address-pool* [pool-id]
            |        |  |           +--rw pool-id          string
            |        |  |           +--rw start-address
            |        |  |           |       inet:ipv6-address
            |        |  |           +--rw end-address?
            |        |  |                   inet:ipv6-address
            |        |  +--rw (provider-dhcp)?
            |        |  |  +--:(dhcp-service-type)
            |        |  |     +--rw dhcp-service-type?
            |        |  |             enumeration
            |        |  +--rw (dhcp-relay)?
            |        |     +--:(customer-dhcp-servers)
            |        |        +--rw customer-dhcp-servers
            |        |           +--rw server-ip-address*
            |        |                   inet:ipv6-address
            |        +--:(static-addresses)
            |           +--rw address* [address-id]
            |              +--rw address-id          string
            |              +--rw customer-address?   inet:ipv6-address
               ...

            Figure 10: Layer 3 Connection Tree Structure (IPv6)

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4.2.5.3.  Routing

   As shown in the tree depicted in Figure 11, the 'routing-protocols'
   container defines the required parameters to enable the desired
   routing features for an AC.  One or more routing protocols can be
   associated with an AC.  Such routing protocols will be then enabled
   between a PE and the customer terminating points.  Each routing
   instance is uniquely identified by the combination of the 'id' and
   'type' to accommodate scenarios where multiple instances of the same
   routing protocol have to be configured on the same link.

   In addition to static routing (Section 4.2.5.3.1), the module
   supports BGP (Section 4.2.5.3.2), OSPF (Section 4.2.5.3.3), IS-IS
   (Section 4.2.5.4), and RIP (Section 4.2.5.5).  It also includes a
   reference to the 'routing-profile-identifier' defined in
   Section 4.2.2, so that additional constraints can be applied to a
   specific instance of each routing protocol.

           +--rw specific-provisioning-profiles
           |  ...
           +--rw service-provisioning-profiles
           |  ...
           +--rw attachment-circuits
              +--rw ac-group-profile* [name]
              |  ...
              +--rw placement-constraints
              |  ...
              +--rw ac* [name]
                 +--rw customer-name?       string
                 +--rw description?         string
                 +--rw requested-start?     yang:date-and-time
                 +--rw requested-stop?      yang:date-and-time
                 +--ro actual-start?        yang:date-and-time
                 +--ro actual-stop?         yang:date-and-time
                 +--rw peer-sap-id*         string
                 +--rw ac-group-profile*    ac-group-reference
                 +--rw group* [group-id]
                 |  +--rw group-id      string
                 |  +--rw precedence?   identityref
                 +--rw name                 string
                 +--rw l2-connection
                 | ...
                 +--rw ip-connection
                 |  ...
                 +--rw routing-protocols
                 |  +--rw routing-protocol* [id]
                 |     +--rw id                  string
                 |     +--rw type?               identityref

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                 |     +--rw routing-profiles* [id]
                 |     |  +--rw id      routing-profile-reference
                 |     |  +--rw type?   identityref
                 |     +--rw static
                 |     |  ...
                 |     +--rw bgp
                 |     |  ...
                 |     |  ...
                 |     +--rw isis
                 |     |  ...
                 |     +--rw rip
                 |     |  ...
                 |     +--rw vrrp
                 |        ...
                 +--rw oam
                 |  ...
                 +--rw security
                 |  ...
                 +--rw service
                    ...

                     Figure 11: Routing Tree Structure

4.2.5.3.1.  Static Routing

   The static tree structure is shown in Figure 12.

           |  ...
           +--rw routing-protocols
           |  +--rw routing-protocol* [id]
           |     +--rw id                  string
           |     +--rw type?               identityref
           |     +--rw routing-profiles* [id]
           |     |  +--rw id      routing-profile-reference
           |     |  +--rw type?   identityref
           |     +--rw static
           |     |  +--rw cascaded-lan-prefixes
           |     |     +--rw ipv4-lan-prefixes* [lan next-hop]
           |     |     |       {vpn-common:ipv4}?
           |     |     |  +--rw lan         inet:ipv4-prefix
           |     |     |  +--rw lan-tag?    string
           |     |     |  +--rw next-hop    union
           |     |     |  +--rw metric?     uint32
           |     |     |  +--rw bfd-profile?   bfd-profile-reference
           |     |     |  +--rw status
           |     |     |     +--rw admin-status
           |     |     |     |  +--rw status?        identityref
           |     |     |     |  +--ro last-change?   yang:date-and-time

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           |     |     |     +--ro oper-status
           |     |     |        +--ro status?        identityref
           |     |     |        +--ro last-change?   yang:date-and-time
           |     |     +--rw ipv6-lan-prefixes* [lan next-hop]
           |     |             {vpn-common:ipv6}?
           |     |        +--rw lan         inet:ipv6-prefix
           |     |        +--rw lan-tag?    string
           |     |        +--rw next-hop    union
           |     |        +--rw metric?     uint32
           |     |        +--rw bfd-profile?   bfd-profile-reference
           |     |        +--rw status
           |     |           +--rw admin-status
           |     |           |  +--rw status?        identityref
           |     |           |  +--ro last-change?   yang:date-and-time
           |     |           +--ro oper-status
           |     |              +--ro status?        identityref
           |     |              +--ro last-change?   yang:date-and-time
           |     +--rw bgp
           |     |  ...
           |     +--rw ospf
           |     |  ...
           |     +--rw isis
           |     |  ...
           |     +--rw rip
           |     |  ...
           |     +--rw vrrp
           |        ...

                  Figure 12: Static Routing Tree Structure

   As depicted in Figure 12, the following data nodes can be defined for
   a given IP prefix:

   'lan-tag':  Indicates a local tag (e.g., "myfavorite-lan") that is
      used to enforce local policies.

   'next-hop':  Indicates the next hop to be used for the static route.

      It can be identified by an IP address, a predefined next-hop type
      (e.g., 'discard' or 'local-link'), etc.

   'metric':  Indicates the metric associated with the static route
      entry.  This metric is used when the route is exported into an
      IGP.

   'bfd-profile':  Indicates a BFD profile that applies for this entry.

   'status':  Used to convey the status of a static route entry.  This

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      data node can also be used to control the (de)activation of
      individual static route entries.

4.2.5.3.2.  BGP

   The BGP tree structure is shown in Figure 13.

           |  ...
           +--rw routing-protocols
           |  +--rw routing-protocol* [id]
           |     +--rw id                  string
           |     +--rw type?               identityref
           |     +--rw routing-profiles* [id]
           |     |  +--rw id      routing-profile-reference
           |     |  +--rw type?   identityref
           |     +--rw static
           |     |  ...
           |     +--rw bgp
           |     |  +--rw peer-groups
           |     |  |  +--rw peer-group* [name]
           |     |  |     +--rw name              string
           |     |  |     +--ro local-as?         inet:as-number
           |     |  |     +--rw peer-as?          inet:as-number
           |     |  |     +--rw address-family?   identityref
           |     |  |     +--ro local-address?    inet:ip-address
           |     |  |     +--rw authentication
           |     |  |        +--rw enabled?            boolean
           |     |  |        +--rw keying-material
           |     |  |           +--rw (option)?
           |     |  |              +--:(ao)
           |     |  |              |  +--rw enable-ao?          boolean
           |     |  |              |  +--rw ao-keychain?
           |     |  |              |          key-chain:key-chain-ref
           |     |  |              +--:(md5)
           |     |  |              |  +--rw md5-keychain?
           |     |  |              |          key-chain:key-chain-ref
           |     |  |              +--:(explicit)
           |     |  |                 +--rw key-id?             uint32
           |     |  |                 +--rw key?                string
           |     |  |                 +--rw crypto-algorithm?
           |     |  |                         identityref
           |     |  +--rw neighbor* [id]
           |     |     +--rw id                string
           |     |     +--rw remote-address?   inet:ip-address
           |     |     +--ro local-address?    inet:ip-address
           |     |     +--rw peer-group?
           |     |     |       -> ../../peer-groups/peer-group/name
           |     |     +--rw bfd-profile?      bfd-profile-reference

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           |     |     +--ro local-as?         inet:as-number
           |     |     +--rw peer-as?          inet:as-number
           |     |     +--rw address-family?   identityref
           |     |     +--rw authentication
           |     |     |  +--rw enabled?            boolean
           |     |     |  +--rw keying-material
           |     |     |     +--rw (option)?
           |     |     |        +--:(ao)
           |     |     |        |  +--rw enable-ao?          boolean
           |     |     |        |  +--rw ao-keychain?
           |     |     |        |          key-chain:key-chain-ref
           |     |     |        +--:(md5)
           |     |     |        |  +--rw md5-keychain?
           |     |     |        |          key-chain:key-chain-ref
           |     |     |        +--:(explicit)
           |     |     |           +--rw key-id?             uint32
           |     |     |           +--rw key?                string
           |     |     |           +--rw crypto-algorithm?   identityref
           |     |     +--rw status
           |     |        +--rw admin-status
           |     |        |  +--rw status?        identityref
           |     |        |  +--ro last-change?   yang:date-and-time
           |     |        +--ro oper-status
           |     |           +--ro status?        identityref
           |     |           +--ro last-change?   yang:date-and-time
           |     +--rw ospf
           |     |  ...
           |     +--rw isis
           |     |  ...
           |     +--rw rip
           |     |  ...
           |     +--rw vrrp
           |        ...

                       Figure 13: BGP Tree Structure

   The following data nodes are supported for each BGP 'peer-group':

   'name':  Defines a name for the peer group.

   'local-as':  Indicates a local AS Number (ASN).

   'peer-as':  Indicates the peer's ASN.

   'address-family':  Indicates the address family of the peer.  It can
      be set to 'ipv4', 'ipv6', or 'dual-stack'.

      This address family might be used together with the service type

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      that uses an AC (e.g., 'vpn-type' [RFC9182]) to derive the
      appropriate Address Family Identifiers (AFIs) / Subsequent Address
      Family Identifiers (SAFIs) that will be part of the derived device
      configurations (e.g., unicast IPv4 MPLS L3VPN (AFI,SAFI = 1,128)
      as defined in Section 4.3.4 of [RFC4364]).

   'local-address':  Specifies an address or a reference to an interface
      to use when establishing the BGP transport session.

   'authentication':  The module adheres to the recommendations in
      Section 13.2 of [RFC4364], as it allows enabling the TCP
      Authentication Option (TCP-AO) [RFC5925] and accommodates the
      installed base that makes use of MD5.  In addition, the module
      includes a provision for using IPsec.

      Similar to [RFC9182], this version of the ACaaS assumes that
      parameters specific to the TCP-AO are preconfigured as part of the
      key chain that is referenced in the ACaaS.  No assumption is made
      about how such a key chain is preconfigured.  However, the
      structure of the key chain should cover data nodes beyond those in
      [RFC8177], mainly SendID and RecvID (Section 3.1 of [RFC5925]).

   For each neighbor, the following data nodes are supported in addition
   to similar parameters that are provided for a peer group:

   'remote-address':  Specifies the remote IP address of a BGP neighbor.

   'peer-group':  A name of a peer group.

      Parameters that are provided at the 'neighbor' level takes
      precedence over the ones provided in the peer group.

   'bfd-profile':  Indicates a BFD profile that applies for a BGP
      neighbor.

   'status':  Indicates the status of the BGP routing instance.

4.2.5.3.3.  OSPF

   The OSPF tree structure is shown in Figure 14.

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            |  ...
            +--rw routing-protocols
            |  +--rw routing-protocol* [id]
            |     +--rw id                  string
            |     +--rw type?               identityref
            |     +--rw routing-profiles* [id]
            |     |  +--rw id      routing-profile-reference
            |     |  +--rw type?   identityref
            |     +--rw static
            |     |  ...
            |     +--rw bgp
            |     |  ...
            |     +--rw ospf
            |     |  +--rw address-family?   identityref
            |     |  +--rw area-id           yang:dotted-quad
            |     |  +--rw metric?           uint16
            |     |  +--rw authentication
            |     |  |  +--rw enabled?            boolean
            |     |  |  +--rw keying-material
            |     |  |     +--rw (option)?
            |     |  |        +--:(auth-key-chain)
            |     |  |        |  +--rw key-chain?
            |     |  |        |          key-chain:key-chain-ref
            |     |  |        +--:(auth-key-explicit)
            |     |  |           +--rw key-id?             uint32
            |     |  |           +--rw key?                string
            |     |  |           +--rw crypto-algorithm?   identityref
            |     |  +--rw status
            |     |     +--rw admin-status
            |     |     |  +--rw status?        identityref
            |     |     |  +--ro last-change?   yang:date-and-time
            |     |     +--ro oper-status
            |     |        +--ro status?        identityref
            |     |        +--ro last-change?   yang:date-and-time
            |     +--rw isis
            |     |  ...
            |     +--rw rip
            |     |  ...
            |     +--rw vrrp
            |        ...

                       Figure 14: OSPF Tree Structure

   The following OSPF data nodes are supported:

   'address-family':  Indicates whether IPv4, IPv6, or both address
      families are to be activated.

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   'area-id':  Indicates the OSPF Area ID.

   'metric':  Associates a metric with OSPF routes.

   'sham-links':  Used to create OSPF sham links between two ACs sharing
      the same area and having a backdoor link (Section 4.2.7 of
      [RFC4577] and Section 5 of [RFC6565]).

   'authentication':  Controls the authentication schemes to be enabled
      for the OSPF instance.  The following options are supported: IPsec
      for OSPFv3 authentication [RFC4552], and the Authentication
      Trailer for OSPFv2 [RFC5709][RFC7474] and OSPFv3 [RFC7166].

   'status':  Indicates the status of the OSPF routing instance.

4.2.5.4.  IS-IS

   The IS-IS tree structure is shown in Figure 15.

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            |  ...
            +--rw routing-protocols
            |  +--rw routing-protocol* [id]
            |     +--rw id                  string
            |     +--rw type?               identityref
            |     +--rw routing-profiles* [id]
            |     |  +--rw id      routing-profile-reference
            |     |  +--rw type?   identityref
            |     +--rw static
            |     |  ...
            |     +--rw bgp
            |     |  ...
            |     +--rw ospf
            |     |  ...
            |     +--rw isis
            |     |  +--rw address-family?   identityref
            |     |  +--rw area-address      area-address
            |     |  +--rw authentication
            |     |  |  +--rw enabled?            boolean
            |     |  |  +--rw keying-material
            |     |  |     +--rw (option)?
            |     |  |        +--:(auth-key-chain)
            |     |  |        |  +--rw key-chain?
            |     |  |        |          key-chain:key-chain-ref
            |     |  |        +--:(auth-key-explicit)
            |     |  |           +--rw key-id?             uint32
            |     |  |           +--rw key?                string
            |     |  |           +--rw crypto-algorithm?   identityref
            |     |  +--rw status
            |     |     +--rw admin-status
            |     |     |  +--rw status?        identityref
            |     |     |  +--ro last-change?   yang:date-and-time
            |     |     +--ro oper-status
            |     |        +--ro status?        identityref
            |     |        +--ro last-change?   yang:date-and-time
            |     +--rw rip
            |     |  ...
            |     +--rw vrrp
            |      ...

                      Figure 15: IS-IS Tree Structure

   The following IS-IS data nodes are supported:

   'address-family':  Indicates whether IPv4, IPv6, or both address
      families are to be activated.

   'area-address':  Indicates the IS-IS area address.

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   'authentication':  Controls the authentication schemes to be enabled
      for the IS-IS instance.  Both the specification of a key chain
      [RFC8177] and the direct specification of key and authentication
      algorithms are supported.

   'status':  Indicates the status of the IS-IS routing instance.

4.2.5.5.  RIP

   The RIP tree structure is shown in Figure 16.

            |  ...
            +--rw routing-protocols
            |  +--rw routing-protocol* [id]
            |     +--rw id                  string
            |     +--rw type?               identityref
            |     +--rw routing-profiles* [id]
            |     |  +--rw id      routing-profile-reference
            |     |  +--rw type?   identityref
            |     +--rw static
            |     |  ...
            |     +--rw bgp
            |     |  ...
            |     +--rw ospf
            |     |  ...
            |     +--rw isis
            |     |  ...
            |     +--rw rip
            |     |  +--rw address-family?   identityref
            |     |  +--rw authentication
            |     |  |  +--rw enabled?            boolean
            |     |  |  +--rw keying-material
            |     |  |     +--rw (option)?
            |     |  |        +--:(auth-key-chain)
            |     |  |        |  +--rw key-chain?
            |     |  |        |          key-chain:key-chain-ref
            |     |  |        +--:(auth-key-explicit)
            |     |  |           +--rw key?                string
            |     |  |           +--rw crypto-algorithm?   identityref
            |     |  +--rw status
            |     |     +--rw admin-status
            |     |     |  +--rw status?        identityref
            |     |     |  +--ro last-change?   yang:date-and-time
            |     |     +--ro oper-status
            |     |        +--ro status?        identityref
            |     |        +--ro last-change?   yang:date-and-time
            |     +--rw vrrp
            |      ...

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                       Figure 16: RIP Tree Structure

   'address-family' indicates whether IPv4, IPv6, or both address
   families are to be activated.  For example, this parameter is used to
   determine whether RIPv2 [RFC2453], RIP Next Generation (RIPng), or
   both are to be enabled [RFC2080].

4.2.5.6.  VRRP

   The model supports the Virtual Router Redundancy Protocol (VRRP)
   [RFC5798] on an AC (Figure 17).

              |  ...
              +--rw routing-protocols
              |  +--rw routing-protocol* [id]
              |     +--rw id                  string
              |     +--rw type?               identityref
              |     +--rw routing-profiles* [id]
              |     |  +--rw id      routing-profile-reference
              |     |  +--rw type?   identityref
              |     +--rw static
              |     |  ...
              |     +--rw bgp
              |     |  ...
              |     +--rw ospf
              |     |  ...
              |     +--rw isis
              |     |  ...
              |     +--rw rip
              |     |  ...
              |     +--rw vrrp
              |        +--rw address-family?   identityref
              |        +--rw status
              |           +--rw admin-status
              |           |  +--rw status?        identityref
              |           |  +--ro last-change?   yang:date-and-time
              |           +--ro oper-status
              |              +--ro status?        identityref
              |              +--ro last-change?   yang:date-and-time

                       Figure 17: VRRP Tree Structure

   The following data nodes are supported:

   'address-family':  Indicates whether IPv4, IPv6, or both address
      families are to be activated.  Note that VRRP version 3 [RFC5798]
      supports both IPv4 and IPv6.

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   'status':  Indicates the status of the VRRP instance.

   Note that no authentication data node is included for VRRP, as there
   isn't any type of VRRP authentication at this time (see Section 9 of
   [RFC5798]).

4.2.5.7.  OAM

   As shown in the tree depicted in Figure 18, the 'oam' container
   defines OAM-related parameters of an AC.

          +--rw specific-provisioning-profiles
          |  ...
          +--rw service-provisioning-profiles
          |  ...
          +--rw attachment-circuits
             +--rw ac-group-profile* [name]
             |  ...
             +--rw placement-constraints
             |  ...
             +--rw ac* [name]
                ...
                +--rw l2-connection
                |  ...
                +--rw ip-connection
                |  ...
                +--rw routing-protocols
                |  ...
                +--rw oam
                |  +--rw bfd {vpn-common:bfd}?
                |     +--rw profile?    bfd-profile-reference
                |     +--rw holdtime?   uint32
                |     +--rw status
                |        +--rw admin-status
                |        |  +--rw status?        identityref
                |        |  +--ro last-change?   yang:date-and-time
                |        +--ro oper-status
                |           +--ro status?        identityref
                |           +--ro last-change?   yang:date-and-time
                +--rw security
                |  ...
                +--rw service
                   ...

                       Figure 18: OAM Tree Structure

   This version of the module supports BFD.  The following BFD data
   nodes can be specified:

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   'profile':  Refers to a BFD profile.

   'holdtime':  Used to indicate the expected BFD holddown time, in
      milliseconds.

   'status':  Indicates the status of the BFD over an AC.

4.2.5.8.  Security

   As shown in the tree depicted in Figure 19, the 'security' container
   defines a set of AC security parameters.

           +--rw specific-provisioning-profiles
           |  ...
           +--rw service-provisioning-profiles
           |  ...
           +--rw attachment-circuits
              +--rw ac-group-profile* [name]
              |  ...
              +--rw placement-constraints
              |  ...
              +--rw ac* [name]
                 ...
                 +--rw l2-connection
                 |  ...
                 +--rw ip-connection
                 |  ...
                 +--rw routing-protocols
                 |  ...
                 +--rw oam
                 |  ...
                 +--rw security
                 |  +--rw encryption {vpn-common:encryption}?
                 |  |  +--rw enabled?   boolean
                 |  |  +--rw layer?     enumeration
                 |  +--rw encryption-profile
                 |     +--rw (profile)?
                 |        +--:(provider-profile)
                 |        |  +--rw provider-profile?
                 |        |          encryption-profile-reference
                 |        +--:(customer-profile)
                 |           +--rw customer-key-chain?
                 |                   key-chain:key-chain-ref
                 +--rw service
                    ...

                     Figure 19: Security Tree Structure

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   The 'security' container specifies the authentication and the
   encryption to be applied to traffic for a given AC.  Tthe model can
   be used to directly control the encryption to be applied (e.g., Layer
   2 or Layer 3 encryption) or invoke a local encryption profile.

4.2.5.9.  Service

   The structure of the 'service' container is depicted in Figure 20.

       +--rw specific-provisioning-profiles
       |  ...
       +--rw service-provisioning-profiles
       |  ...
       +--rw attachment-circuits
          +--rw ac-group-profile* [name]
          |  ...
          +--rw placement-constraints
          |  ...
          +--rw ac* [name]
             ...
             +--rw l2-connection
             |  ...
             +--rw ip-connection
             |  ...
             +--rw routing-protocols
             |  ...
             +--rw oam
             |  ...
             +--rw security
             |  ...
             +--rw service
                +--rw svc-pe-to-ce-bandwidth {vpn-common:inbound-bw}?
                |  +--rw bandwidth* [bw-type]
                |     +--rw bw-type      identityref
                |     +--rw (type)?
                |        +--:(per-cos)
                |        |  +--rw cos* [cos-id]
                |        |     +--rw cos-id    uint8
                |        |     +--rw cir?      uint64
                |        |     +--rw cbs?      uint64
                |        |     +--rw eir?      uint64
                |        |     +--rw ebs?      uint64
                |        |     +--rw pir?      uint64
                |        |     +--rw pbs?      uint64
                |        +--:(other)
                |           +--rw cir?   uint64
                |           +--rw cbs?   uint64
                |           +--rw eir?   uint64

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                |           +--rw ebs?   uint64
                |           +--rw pir?   uint64
                |           +--rw pbs?   uint64
                +--rw svc-ce-to-pe-bandwidth {vpn-common:outbound-bw}?
                |  +--rw bandwidth* [bw-type]
                |     +--rw bw-type      identityref
                |     +--rw (type)?
                |        +--:(per-cos)
                |        |  +--rw cos* [cos-id]
                |        |     +--rw cos-id    uint8
                |        |     +--rw cir?      uint64
                |        |     +--rw cbs?      uint64
                |        |     +--rw eir?      uint64
                |        |     +--rw ebs?      uint64
                |        |     +--rw pir?      uint64
                |        |     +--rw pbs?      uint64
                |        +--:(other)
                |           +--rw cir?   uint64
                |           +--rw cbs?   uint64
                |           +--rw eir?   uint64
                |           +--rw ebs?   uint64
                |           +--rw pir?   uint64
                |           +--rw pbs?   uint64
                +--rw qos {vpn-common:qos}?
                |  +--rw qos-profiles
                |     +--rw qos-profile* [profile]
                |        +--rw profile      qos-profile-reference
                |        +--rw direction?   identityref
                +--rw access-control-list
                   +--rw acl-profiles
                      +--rw acl-profile* [profile]
                         +--rw profile    forwarding-profile-reference

                    Figure 20: Bandwidth Tree Structure

   The 'service' container defines the following data nodes:

   'mtu':  Specifies the Layer 2 MTU, in bytes, for the AC.

   'svc-pe-to-ce-bandwidth' and'svc-ce-to-pe-bandwidth':

   'svc-pe-to-ce-bandwidth':  Indicates the inbound bandwidth of the AC
      (i.e., download bandwidth from the service provider to the
      customer site).

   'svc-ce-to-pe-bandwidth':  Indicates the outbound bandwidth of the AC
      (i.e., upload bandwidth from the customer site to the service
      provider).

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      Both 'svc-pe-to-ce-bandwidth' and 'svc-ce-to-pe-bandwidth' can be
      represented using the Committed Information Rate (CIR), the Excess
      Information Rate (EIR), or the Peak Information Rate (PIR).  Both
      reuse the 'bandwidth-per-type' grouping defined in
      [I-D.ietf-opsawg-teas-common-ac].

   'qos':  Specifies a list of QoS profiles to apply for this AC.

   'access-control-list':  Specifies a list of ACL profiles to apply for
      this AC.

5.  YANG Modules

5.1.  The Bearer Service ("ietf-bearer-svc") YANG Module

   This module uses types defined in [RFC6991] and [RFC9181].

   <CODE BEGINS> file "ietf-bearer-svc@2023-11-13.yang"
   module ietf-bearer-svc {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-bearer-svc";
     prefix bearer-svc;

     import ietf-vpn-common {
       prefix vpn-common;
       reference
         "RFC 9181: A Common YANG Data Model for Layer 2 and Layer 3
                    VPNs";
     }
     import ietf-ac-common {
       prefix ac-common;
       reference
         "RFC CCCC: A Common YANG Data Model for Attachment Circuits";
     }
     import ietf-ac-svc {
       prefix ac-svc;
       reference
         "RFC XXXX: YANG Service Data Models for Attachment Circuits";
     }

     organization
       "IETF OPSAWG (Operations and Management Area Working Group)";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/opsawg/>
        WG List:  <mailto:opsawg@ietf.org>

        Editor:   Mohamed Boucadair
                  <mailto:mohamed.boucadair@orange.com>

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        Author:   Richard Roberts
                  <mailto:rroberts@juniper.net>
        Author:   Oscar Gonzalez de Dios
                  <mailto:oscar.gonzalezdedios@telefonica.com>
        Author:   Samier Barguil
                  <mailto:ssamier.barguil_giraldo@nokia.com>
        Author:   Bo Wu
                  <mailto:lana.wubo@huawei.com>";
     description
       "This YANG module defines a generic YANG model for exposing
        network bearers as a service.

        Copyright (c) 2024 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC xxx; see the
        RFC itself for full legal notices.";

     revision 2023-11-13 {
       description
         "Initial revision.";
       reference
         "RFC xxxx: A YANG Service Data Model for Attachment Circuits";
     }

     // Typedef to ease referencing cross-modules

     typedef bearer-ref {
       type leafref {
         path "/bearer-svc:bearers/bearer-svc:bearer/bearer-svc:name";
       }
       description
         "Defines a type to reference a bearer.";
     }

     // Identities

     identity identification-type {
       description
         "Base identity for identification of bearers.";
     }

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     identity device-id {
       base identification-type;
       description
         "Identification of bearers based on device.";
     }

     identity site-id {
       base identification-type;
       description
         "Identification of bearers based on site.";
     }

     identity site-and-device-id {
       base identification-type;
       description
         "Identification of bearers based on site and device.";
     }

     identity custom {
       base identification-type;
       description
         "Identification of bearers based on other custom criteria.";
     }

     identity bearer-type {
       description
         "Base identity for bearers type.";
     }

     identity ethernet {
       base bearer-type;
       description
         "Ethernet.";
     }

     identity wireless {
       base bearer-type;
       description
         "Wireless.";
     }

     identity lag {
       base bearer-type;
       description
         "Link Aggregation Group (LAG).";
     }

     identity network-termination-hint {

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       base vpn-common:placement-diversity;
       description
         "A hint about the termination at the network side
          is provided (e.g., geoproximity).";
     }

     identity syncPHY-type {
       description
         "Base identity for physical layer synchronization.";
     }

     identity syncE {
       base syncPHY-type;
       description
         "Sync Ethernet (SyncE).";
       reference
         "ITU-T G.781: Synchronization layer functions for frequency
                       synchronization based on the physical layer";
     }

     grouping location-information {
       description
         "Basic location information";
       container location {
         description
           "Location of the node.";
         leaf location-name {
           type string;
           description
             "Provides a location name. This data node can be mapped,
              e.g., to the 3GPP NRM IOC ManagedElement.";
         }
         leaf address {
           type string;
           description
             "Address (number and street) of the device/site.";
         }
         leaf postal-code {
           type string;
           description
             "Postal code of the device/site.";
         }
         leaf state {
           type string;
           description
             "State of the device/site.  This leaf can also be
              used to describe a region for a country that
              does not have states.";

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         }
         leaf city {
           type string;
           description
             "City of the device/site.";
         }
         leaf country-code {
           type string {
             pattern '[A-Z]{2}';
           }
           description
             "Country of the device/site.
              Expressed as ISO ALPHA-2 code.";
         }
       }
     }

     grouping placement-constraints {
       description
         "Constraints related to placement of a bearer.";
       list constraint {
         if-feature vpn-common:placement-diversity;
         key "constraint-type";
         description
           "List of constraints.";
         leaf constraint-type {
           type identityref {
             base vpn-common:placement-diversity;
           }
           must "not(derived-from-or-self(current(), "
               + "'vpn-common:bearer-diverse') or "
               + "derived-from-or-self(current(), "
               + "'vpn-common:same-bearer'))" {
                error-message "Only bearer-specific diversity"
                            + "constraints must be provided.";
           }
           description
             "Diversity constraint type for bearers.";
         }
         container target {
           description
             "The constraint will apply against this list of
              groups.";
           choice target-flavor {
             description
               "Choice for the group definition.";
             case id {
               list group {

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                 key "group-id";
                 description
                   "List of groups.";
                 leaf group-id {
                   type string;
                    description
                      "The constraint will apply against this
                       particular group ID.";
                  }
                }
              }
              case all-bearers {
                leaf all-other-bearers {
                  type empty;
                  description
                    "The constraint will apply against all other
                     bearers of a site.";
                }
              }
              case all-groups {
                leaf all-other-groups {
                  type empty;
                  description
                    "The constraint will apply against all other
                     groups managed by the customer.";
               }
             }
           }
         }
       }
     }

     container bearers {
       description
         "Main container for the bearers.";

       container placement-constraints {
         description
           "Diversity constraint type.";
         uses placement-constraints;
       }

       list bearer {
         key "name";
         description
           "Maintains a list of bearers.";
         leaf name {
           type string;

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           description
             "A name that uniquely identifies a bearer for
              a given customer.";
         }
         leaf description {
           type string;
           description
             "A description of this bearer.";
         }
         uses vpn-common:vpn-components-group;
         leaf op-comment {
           type string;
           description
             "Includes comments that can be shared with operational
              teams and which may be useful for the activation of a
              bearer. This may include, for example, information
              about the building, level, etc.";
         }
         leaf bearer-parent-ref {
           type bearer-svc:bearer-ref;
           description
             "Specifies the parent bearer. This can be used, e.g.,
              for a Link Aggregation Group (LAG).";
         }
         leaf-list bearer-lag-member {
           type bearer-svc:bearer-ref;
           config false;
           description
             "Reports LAG members.";
         }
         leaf sync-phy-capable {
           type boolean;
           config false;
           description
            "Indicates when set to true that a mechanism for physical
             layer synchronization is supported for this bearer. No such
             mechanism is supported if set to false.";
         }
         leaf sync-phy-enabled {
           when "../sync-phy-capable='true'";
           type boolean;
           description
            "Indicates when set to true that a mechanism for physical
             layer synchronization is enabled for this bearer. No such
             mechanism is enabled if set to false.";
         }
         leaf sync-phy-type {
           when "../sync-phy-enabled='true'";

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           type identityref {
             base syncPHY-type;
           }
           description
             "Type of the physical layer synchronization.";
         }
         container customer-point {
           description
             "Base container to link the Bearer existence";
           leaf identified-by {
             type identityref {
               base identification-type;
             }
             description
               "Attribute used to identify the bearer";
           }
           container device {
             when
               "derived-from-or-self(../identified-by, "
             + "'bearer-svc:device-id') or "
             + "derived-from-or-self(../identified-by, "
             + "'bearer-svc:site-and-device-id')" {
               description
                 "Only applicable if identified-by is device.";
             }
             description
               "Bearer is linked to device.";
             leaf device-id {
               type string;
               description
                 "Identifier for the device where that bearer belongs.";
             }
             uses location-information;
           }
           container site {
             when
               "derived-from-or-self(../identified-by, "
             + "'bearer-svc:site-id') or "
             + "derived-from-or-self(../identified-by, "
             + "'bearer-svc:site-and-device-id')" {
               description
                 "Only applicable if identified-by is site.";
             }
             description
               "Bearer is linked to a site.";
             leaf site-id {
               type string;
               description

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                 "Identifier for the site or sites where that bearer
                  belongs.";
             }
             uses location-information;
           }
           leaf custom-id {
             when "derived-from-or-self(../identified-by, "
                + "'bearer-svc:custom')" {
               description
                 "Only enabled id identified-by is custom.";
             }
             type string;
             description
               "The semantic of this identifier is shared between the
                 customer/provider using out-of-band means.";
           }
         }
         leaf type {
           type identityref {
             base bearer-type;
           }
           description
             "Type of the bearer (e.g., Ethernet or wireless).";
         }
         leaf test-only {
           type empty;
           description
            "When present, this indicates that this is a feasibility
             check request. No resources are commited for such bearer
             requests.";
         }
         leaf bearer-reference {
           if-feature "vpn-common:bearer-reference";
           type string;
           config false;
           description
             "This is an internal reference for the service provider
              to identify the bearers.";
         }
         leaf-list ac-svc-ref {
           type ac-svc:attachment-circuit-reference;
           config false;
           description
             "Specifies the set of ACes that are bound to the bearer.";
         }
         uses ac-common:op-instructions;
         uses ac-common:service-status;
       }

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     }
   }
   <CODE ENDS>

5.2.  The AC Service ("ietf-ac-svc") YANG Module

   This module uses types defined in [RFC6991], [RFC9181], [RFC8177],
   and [I-D.ietf-opsawg-teas-common-ac].

   <CODE BEGINS> file "ietf-ac-svc@2023-11-13.yang"
   module ietf-ac-svc {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-ac-svc";
     prefix ac-svc;

     import ietf-ac-common {
       prefix ac-common;
       reference
         "RFC CCCC: A Common YANG Data Model for Attachment Circuits";
     }
     import ietf-vpn-common {
       prefix vpn-common;
       reference
         "RFC 9181: A Common YANG Data Model for Layer 2 and Layer 3
                    VPNs";
     }
     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";
     }
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types, Section 4";
     }
     import ietf-key-chain {
       prefix key-chain;
       reference
         "RFC 8177: YANG Data Model for Key Chains";
     }

     organization
       "IETF OPSAWG (Operations and Management Area Working Group)";
     contact
       "WG Web:   <https://datatracker.ietf.org/wg/opsawg/>
        WG List:  <mailto:opsawg@ietf.org>

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        Editor:   Mohamed Boucadair
                  <mailto:mohamed.boucadair@orange.com>
        Author:   Richard Roberts
                  <mailto:rroberts@juniper.net>
        Author:   Oscar Gonzalez de Dios
                  <mailto:oscar.gonzalezdedios@telefonica.com>
        Author:   Samier Barguil
                  <mailto:ssamier.barguil_giraldo@nokia.com>
        Author:   Bo Wu
                  <mailto:lana.wubo@huawei.com>";
     description
       "This YANG module defines a YANG model for exposing
        attachment circuits as a service (ACaaS).

        Copyright (c) 2024 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject
        to the license terms contained in, the Revised BSD License
        set forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC XXXX; see the
        RFC itself for full legal notices.";

     revision 2023-11-13 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: YANG Service Data Models for Attachment Circuits";
     }

     /* A set of typedefs to ease referencing cross-modules */

     typedef attachment-circuit-reference {
       type leafref {
         path "/ac-svc:attachment-circuits/ac-svc:ac/ac-svc:name";
       }
       description
         "Defines a reference to an attachment circuit that can be used
          by other modules.";
     }

     typedef ac-group-reference {
       type leafref {
         path "/ac-svc:attachment-circuits/ac-svc:ac-group-profile"

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            + "/ac-svc:name";
       }
       description
         "Defines a reference to an attachment circuit profile.";
     }

     typedef encryption-profile-reference {
       type leafref {
         path
           "/ac-svc:specific-provisioning-profiles"
         + "/ac-svc:valid-provider-identifiers"
         + "/ac-svc:encryption-profile-identifier/ac-svc:id";
       }
       description
         "Defines a type to an encryption profile for referencing
          purposes.";
     }

     typedef qos-profile-reference {
       type leafref {
         path
           "/ac-svc:specific-provisioning-profiles"
         + "/ac-svc:valid-provider-identifiers"
         + "/ac-svc:qos-profile-identifier/ac-svc:id";
       }
       description
         "Defines a type to a QoS profile for referencing purposes.";
     }

     typedef bfd-profile-reference {
       type leafref {
         path
           "/ac-svc:specific-provisioning-profiles"
         + "/ac-svc:valid-provider-identifiers"
         + "/ac-svc:bfd-profile-identifier/ac-svc:id";
       }
       description
         "Defines a type to a BFD profile for referencing purposes.";
     }

     typedef forwarding-profile-reference {
       type leafref {
         path
           "/ac-svc:specific-provisioning-profiles"
         + "/ac-svc:valid-provider-identifiers"
         + "/ac-svc:forwarding-profile-identifier/ac-svc:id";
       }
       description

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         "Defines a type to a forwarding profile for referencing
          purposes.";
     }

     typedef routing-profile-reference {
       type leafref {
         path
           "/ac-svc:specific-provisioning-profiles"
         + "/ac-svc:valid-provider-identifiers"
         + "/ac-svc:routing-profile-identifier/ac-svc:id";
       }
       description
         "Defines a type to a routing profile for referencing
          purposes.";
     }

     typedef service-profile-reference {
       type leafref {
         path
           "/ac-svc:service-provisioning-profiles"
         + "/ac-svc:service-profile-identifier"
         + "/ac-svc:id";
       }
       description
         "Defines a type to a service profile for referencing
          purposes.";
     }

     /******************** Reusable groupings ********************/
     // Basic Layer 2 connection

     grouping l2-connection-basic {
       description
         "Defines Layer 2 protocols and parameters that can be
          factorized when provisioning Layer 2 connectivity
          among multiple ACs.";
       container encapsulation {
         description
           "Container for Layer 2 encapsulation.";
         leaf type {
           type identityref {
             base vpn-common:encapsulation-type;
           }
           description
             "Encapsulation type.";
         }
         container dot1q {
           when "derived-from-or-self(../type, 'vpn-common:dot1q')" {

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             description
               "Only applies when the type of the tagged interface
                is 'dot1q'.";
           }
           description
             "Tagged interface.";
           uses ac-common:dot1q;
         }
         container qinq {
           when "derived-from-or-self(../type, 'vpn-common:qinq')" {
             description
               "Only applies when the type of the tagged interface
                is 'qinq'.";
           }
           description
             "Includes QinQ parameters.";
           uses ac-common:qinq;
         }
       }
     }

     // Full Layer 2 connection

     grouping l2-connection {
       description
         "Defines Layer 2 protocols and parameters that are used to
          enable AC connectivity.";
       container encapsulation {
         description
           "Container for Layer 2 encapsulation.";
         leaf type {
           type identityref {
             base vpn-common:encapsulation-type;
           }
           description
             "Indicates the encapsulation type.";
         }
         container dot1q {
           when "derived-from-or-self(../type, 'vpn-common:dot1q')" {
             description
               "Only applies when the type of the tagged interface
                is 'dot1q'.";
           }
           description
             "Tagged interface.";
           uses ac-common:dot1q;
         }
         container priority-tagged {

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           when "derived-from-or-self(../type, "
              + "'vpn-common:priority-tagged')" {
             description
               "Only applies when the type of the tagged interface is
                'priority-tagged'.";
           }
           description
             "Priority-tagged interface.";
           uses ac-common:priority-tagged;
         }
         container qinq {
           when "derived-from-or-self(../type, 'vpn-common:qinq')" {
             description
               "Only applies when the type of the tagged interface
                is 'qinq'.";
           }
           description
             "Includes QinQ parameters.";
           uses ac-common:qinq;
         }
       }
       choice l2-service {
         description
           "The Layer 2 connectivity service can be provided by
            indicating a pointer to an L2VPN or by specifying a
            Layer 2 tunnel service.";
         container l2-tunnel-service {
           description
             "Defines a Layer 2 tunnel termination.
              It is only applicable when a tunnel is required.";
           uses ac-common:l2-tunnel-service;
         }
         case l2vpn {
           leaf l2vpn-id {
             type vpn-common:vpn-id;
             description
               "Indicates the L2VPN service associated with an
                Integrated Routing and Bridging (IRB) interface.";
           }
         }
       }
       leaf bearer-reference {
         if-feature "vpn-common:bearer-reference";
         type string;
         description
           "This is an internal reference for the service provider
            to identify the bearer associated with this AC.";
       }

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     }

     // Basic IP connection

     grouping ip-connection-basic {
       description
         "Defines basic IP connection parameters.";
       container ipv4 {
         if-feature "vpn-common:ipv4";
         description
           "IPv4-specific parameters.";
         uses ac-common:ipv4-connection-basic;
       }
       container ipv6 {
         if-feature "vpn-common:ipv6";
         description
           "IPv6-specific parameters.";
         uses ac-common:ipv6-connection-basic;
       }
     }

     // Full IP connection

     grouping ip-connection {
       description
         "Defines IP connection parameters.";
       container ipv4 {
         if-feature "vpn-common:ipv4";
         description
           "IPv4-specific parameters.";
         uses ac-common:ipv4-connection;
       }
       container ipv6 {
         if-feature "vpn-common:ipv6";
         description
           "IPv6-specific parameters.";
         uses ac-common:ipv6-connection;
       }
     }

     // Routing protocol list

     grouping routing-protocol-list {
       description
         "List of routing protocols used on the AC.";
       leaf type {
         type identityref {
           base vpn-common:routing-protocol-type;

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         }
         description
           "Type of routing protocol.";
       }
       list routing-profiles {
         key "id";
         description
           "Routing profiles.";
         leaf id {
           type routing-profile-reference;
           description
             "Reference to the routing profile to be used.";
         }
         leaf type {
           type identityref {
             base vpn-common:ie-type;
           }
           description
             "Import, export, or both.";
         }
       }
     }

     // Static routing with BFD

     grouping ipv4-static-rtg-with-bfd {
       description
         "Configuration specific to IPv4 static routing with
          BFD.";
       list ipv4-lan-prefixes {
         if-feature "vpn-common:ipv4";
         key "lan next-hop";
         description
           "List of LAN prefixes for the site.";
         uses ac-common:ipv4-static-rtg-entry;
         leaf bfd-profile {
           type bfd-profile-reference;
           description
             "Points to a BFD profile.";
         }
         uses ac-common:service-status;
       }
     }

     grouping ipv6-static-rtg-with-bfd {
       description
         "Configuration specific to IPv6 static routing with
          BFD.";

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       list ipv6-lan-prefixes {
         if-feature "vpn-common:ipv4";
         key "lan next-hop";
         description
           "List of LAN prefixes for the site.";
         uses ac-common:ipv4-static-rtg-entry;
         leaf bfd-profile {
           type bfd-profile-reference;
           description
             "Points to a BFD profile.";
         }
         uses ac-common:service-status;
       }
     }

     //  BGP Service

     grouping bgp-svc {
       description
         "Configuration specific to BGP.";
       container peer-groups {
         description
           "Configuration for BGP peer-groups";
         list peer-group {
           key "name";
           description
             "List of BGP peer-groups configured on the local
              system - uniquely identified by peer-group
              name.";
           uses ac-common:bgp-peer-group-with-name;
           leaf local-address {
             type inet:ip-address;
             description
               "The local IP address that will be used to establish
                the BGP session.";
           }
           uses ac-common:bgp-authentication;
         }
       }
       list neighbor {
         key "id";
         description
           "List of BGP neighbors.";
         leaf id {
           type string;
           description
             "A neighbor identifier.";
         }

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         leaf remote-address {
           type inet:ip-address;
           description
             "The remote IP address of this entry's BGP peer.

              If this leaf is not present, this means that the primary
              customer IP address is used as remote IP address.";
         }
         leaf local-address {
           type inet:ip-address;
           description
             "The local IP address that will be used to establish
              the BGP session.";
         }
         leaf peer-group {
           type leafref {
             path "../../peer-groups/peer-group/name";
           }
           description
             "The peer-group with which this neighbor is associated.";
         }
         leaf bfd-profile {
           type bfd-profile-reference;
           description
             "Points to a BFD profile.";
         }
         uses ac-common:bgp-peer-group-without-name;
         uses ac-common:bgp-authentication;
         uses ac-common:service-status;
       }
     }

     //  OSPF Service

     grouping ospf-svc {
       description
         "Service configuration specific to OSPF.";
       uses ac-common:ospf-basic;
       uses ac-common:ospf-authentication;
       uses ac-common:service-status;
     }

     //  IS-IS Service

     grouping isis-svc {
       description
         "Service configuration specific to IS-IS.";
       uses ac-common:isis-basic;

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       uses ac-common:isis-authentication;
       uses ac-common:service-status;
     }

     //  RIP Service

     grouping rip-svc {
       description
         "Service configuration specific to RIP routing.";
       leaf address-family {
         type identityref {
           base vpn-common:address-family;
         }
         description
           "Indicates whether IPv4, IPv6, or both address families
            are to be activated.";
       }
       uses ac-common:rip-authentication;
       uses ac-common:service-status;
     }

     //  VRRP Service

     grouping vrrp-svc {
       description
         "Service configuration specific to VRRP.";
       reference
         "RFC 5798: Virtual Router Redundancy Protocol (VRRP)
                    Version 3 for IPv4 and IPv6";
       leaf address-family {
         type identityref {
           base vpn-common:address-family;
         }
         description
           "Indicates whether IPv4, IPv6, or both
            address families are to be enabled.";
       }
       uses ac-common:service-status;
     }

     // Basic routing parameters

     grouping routing-basic {
       description
         "Defines basic parameters for routing protocols.";
       list routing-protocol {
         key "id";
         description

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           "List of routing protocols used on the AC.";
         leaf id {
           type string;
           description
             "Unique identifier for the routing protocol.";
         }
         uses routing-protocol-list;
         container bgp {
           when
             "derived-from-or-self(../type, 'vpn-common:bgp-routing')" {
             description
               "Only applies when the protocol is BGP.";
           }
           description
             "Configuration specific to BGP.";
           container peer-groups {
             description
               "Configuration for BGP peer-groups";
             list peer-group {
               key "name";
               description
                 "List of BGP peer-groups configured on the local
                  system - uniquely identified by peer-group
                  name.";
               uses ac-common:bgp-peer-group-with-name;
             }
           }
         }
         container ospf {
           when "derived-from-or-self(../type, "
              + "'vpn-common:ospf-routing')" {
             description
               "Only applies when the protocol is OSPF.";
           }
           description
             "Configuration specific to OSPF.";
           uses ac-common:ospf-basic;
         }
         container isis {
           when "derived-from-or-self(../type, "
              + "'vpn-common:isis-routing')" {
             description
               "Only applies when the protocol is IS-IS.";
           }
           description
             "Configuration specific to IS-IS.";
           uses ac-common:isis-basic;
         }

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         container rip {
           when "derived-from-or-self(../type, "
              + "'vpn-common:rip-routing')" {
             description
               "Only applies when the protocol is RIP.
                For IPv4, the model assumes that RIP
                version 2 is used.";
           }
           description
             "Configuration specific to RIP routing.";
           leaf address-family {
             type identityref {
               base vpn-common:address-family;
             }
             description
               "Indicates whether IPv4, IPv6, or both
                address families are to be activated.";
           }
         }
         container vrrp {
           when "derived-from-or-self(../type, "
              + "'vpn-common:vrrp-routing')" {
             description
               "Only applies when the protocol is the
                Virtual Router Redundancy Protocol (VRRP).";
           }
           description
             "Configuration specific to VRRP.";
           leaf address-family {
             type identityref {
               base vpn-common:address-family;
             }
             description
               "Indicates whether IPv4, IPv6, or both address families
                are to be enabled.";
           }
         }
       }
     }

     // Full routing parameters

     grouping routing {
       description
         "Defines routing protocols.";
       list routing-protocol {
         key "id";
         description

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           "List of routing protocols used on the AC.";
         leaf id {
           type string;
           description
             "Unique identifier for the routing protocol.";
         }
         uses routing-protocol-list;
         container static {
           when "derived-from-or-self(../type, "
              + "'vpn-common:static-routing')" {
             description
               "Only applies when the protocol is static routing
                protocol.";
           }
           description
             "Configuration specific to static routing.";
           container cascaded-lan-prefixes {
             description
               "LAN prefixes from the customer.";
             uses ipv4-static-rtg-with-bfd;
             uses ipv6-static-rtg-with-bfd;
           }
         }
         container bgp {
           when "derived-from-or-self(../type, "
              + "'vpn-common:bgp-routing')" {
             description
               "Only applies when the protocol is BGP.";
           }
           description
             "Configuration specific to BGP.";
           uses bgp-svc {
             refine "peer-groups/peer-group/local-address" {
               config false;
             }
             refine "neighbor/local-address" {
               config false;
             }
           }
         }
         container ospf {
           when "derived-from-or-self(../type, "
              + "'vpn-common:ospf-routing')" {
             description
               "Only applies when the protocol is OSPF.";
           }
           description
             "Configuration specific to OSPF.";

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           uses ospf-svc;
         }
         container isis {
           when "derived-from-or-self(../type, "
              + "'vpn-common:isis-routing')" {
             description
               "Only applies when the protocol is IS-IS.";
           }
           description
             "Configuration specific to IS-IS.";
           uses isis-svc;
         }
         container rip {
           when "derived-from-or-self(../type, "
              + "'vpn-common:rip-routing')" {
             description
               "Only applies when the protocol is RIP.
                For IPv4, the model assumes that RIP version 2 is
                used.";
           }
           description
             "Configuration specific to RIP routing.";
           uses rip-svc;
         }
         container vrrp {
           when "derived-from-or-self(../type, "
              + "'vpn-common:vrrp-routing')" {
             description
               "Only applies when the protocol is the Virtual Router
                Redundancy Protocol (VRRP).";
           }
           description
             "Configuration specific to VRRP.";
           uses vrrp-svc;
         }
       }
     }

     // Encryption choice

     grouping encryption-choice {
       description
         "Container for the encryption profile.";
       choice profile {
         description
           "Choice for the encryption profile.";
         case provider-profile {
           leaf provider-profile {

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             type encryption-profile-reference;
             description
               "Reference to a provider encryption profile.";
           }
         }
         case customer-profile {
           leaf customer-key-chain {
             type key-chain:key-chain-ref;
             description
               "Customer-supplied key chain.";
           }
         }
       }
     }

     // Basic security parameters

     grouping ac-security-basic {
       description
         "AC-specific security parameters.";
       container encryption {
         if-feature "vpn-common:encryption";
         description
           "Container for AC security encryption.";
         leaf enabled {
           type boolean;
           description
             "If set to 'true', traffic encryption on the connection
              is required.  Otherwise, it is disabled.";
         }
         leaf layer {
           when "../enabled = 'true'" {
             description
               "Included only when encryption is enabled.";
           }
           type enumeration {
             enum layer2 {
               description
                 "Encryption occurs at Layer 2.";
             }
             enum layer3 {
               description
                 "Encryption occurs at Layer 3.
                  For example, IPsec may be used when a customer
                  requests Layer 3 encryption.";
             }
           }
           description

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             "Indicates the layer on which encryption is applied.";
         }
       }
       container encryption-profile {
         when "../encryption/enabled = 'true'" {
           description
             "Indicates the layer on which encryption is enabled.";
         }
         description
           "Container for the encryption profile.";
         uses encryption-choice;
       }
     }

     // Bandwith parameters

     grouping bandwidth {
       description
         "Container for bandwidth.";
       container svc-pe-to-ce-bandwidth {
         if-feature "vpn-common:inbound-bw";
         description
           "From the customer site's perspective, the inbound
            bandwidth of the AC or download bandwidth from the
            service provider to the site.";
         uses ac-common:bandwidth-per-type;
       }
       container svc-ce-to-pe-bandwidth {
         if-feature "vpn-common:outbound-bw";
         description
           "From the customer site's perspective, the outbound
            bandwidth of the AC or upload bandwidth from
            the CE to the PE.";
         uses ac-common:bandwidth-per-type;
       }
     }

     // Basic AC parameters

     grouping ac-basic {
       description
         "Grouping for basic parameters for an attachment circuit.";
       leaf id {
         type string;
         description
           "An identifier of the AC.";
       }
       container l2-connection {

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         description
           "Defines Layer 2 protocols and parameters that are required
            to enable AC connectivity.";
         uses l2-connection-basic;
       }
       container ip-connection {
         description
           "Defines IP connection parameters.";
         uses ip-connection-basic;
       }
       container routing-protocols {
         description
           "Defines routing protocols.";
         uses routing-basic;
       }
       container oam {
         description
           "Defines the Operations, Administration, and Maintenance
            (OAM) mechanisms used.";
         container bfd {
           if-feature "vpn-common:bfd";
           description
             "Container for BFD.";
           uses ac-common:bfd;
         }
       }
       container security {
         description
           "AC-specific security parameters.";
         uses ac-security-basic;
       }
       container service {
         description
           "AC-specific bandwith parameters.";
         leaf mtu {
           type uint32;
           units "bytes";
           description
             "Layer 2 MTU.";
         }
         uses bandwidth;
       }
     }

     // Full AC parameters

     grouping ac {

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       description
         "Grouping for an attachment circuit.";
       leaf name {
         type string;
         description
           "A name of the AC. Data models that need to reference
            an attachment circuit should use
            attachment-circuit-reference.";
       }
       leaf-list service-profile {
         type service-profile-reference;
         description
           "A reference to a service profile.";
       }
       container l2-connection {
         description
           "Defines Layer 2 protocols and parameters that are required
            to enable AC connectivity.";
         uses l2-connection;
       }
       container ip-connection {
         description
           "Defines IP connection parameters.";
         uses ip-connection;
       }
       container routing-protocols {
         description
           "Defines routing protocols.";
         uses routing;
       }
       container oam {
         description
           "Defines the OAM mechanisms used.";
         container bfd {
           if-feature "vpn-common:bfd";
           description
             "Container for BFD.";
           leaf profile {
             type bfd-profile-reference;
             description
               "Points to a BFD profile.";
           }
           uses ac-common:bfd;
           uses ac-common:service-status;
         }
       }
       container security {
         description

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           "AC-specific security parameters.";
         uses ac-security-basic;
       }
       container service {
         description
           "AC-specific bandwith parameters.";
         uses bandwidth;
         container qos {
           if-feature "vpn-common:qos";
           description
             "QoS configuration.";
           container qos-profiles {
             description
               "QoS profile configuration.";
             list qos-profile {
               key "profile";
               description
                 "Points to a QoS profile.";
               leaf profile {
                 type qos-profile-reference;
                 description
                   "QoS profile to be used.";
               }
               leaf direction {
                 type identityref {
                   base vpn-common:qos-profile-direction;
                 }
                 description
                   "The direction to which the QoS profile
                    is applied.";
               }
             }
           }
         }
         container access-control-list {
           description
             "Container for the Access Control List (ACL).";
           container acl-profiles {
             description
               "ACL profile configuration.";
             list acl-profile {
               key "profile";
               description
                 "Points to an ACL profile.";
               leaf profile {
                 type forwarding-profile-reference;
                 description
                   "Forwarding profile to be used.";

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               }
             }
           }
         }
       }
     }

     /******************** Main AC containers ********************/

     container specific-provisioning-profiles {
       description
         "Contains a set of valid profiles to reference for an AC.";
       uses ac-common:ac-profile-cfg;
     }
     container service-provisioning-profiles {
       description
         "Contains a set of valid profiles to reference for an AC.";
       list service-profile-identifier {
         key "id";
         description
           "List of generic service profile identifiers.";
         leaf id {
           type string;
           description
             "Identification of the service profile to be used.
              The profile only has significance within the service
              provider's administrative domain.";
         }
       }
       nacm:default-deny-write;
     }
     container attachment-circuits {
       description
         "Main container for the attachment circuits.";
       list ac-group-profile {
         key "name";
         description
           "Maintains a list of profiles that are shared among
            a set of ACs.";
         uses ac;
       }
       container placement-constraints {
         description
           "Diversity constraint type.";
         uses vpn-common:placement-constraints;
       }
       list ac {
         key "name";

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         description
           "Global provisioning of attachment circuits.";
         leaf customer-name {
           type string;
           description
             "Indicates the name of the customer that requested this
              AC.";
         }
         leaf description {
           type string;
           description
             "Associates a description with an AC.";
         }
         leaf test-only {
           type empty;
           description
            "When present, this indicates that this is a feasibility
             check request. No resources are commited for such AC
             requests.";
         }
         uses ac-common:op-instructions;
         leaf-list peer-sap-id {
           type string;
           description
             "One or more peer SAPs can be indicated.";
         }
         leaf-list ac-group-profile {
           type ac-group-reference;
           description
             "A reference to an AC profile.";
         }
         leaf ac-parent-ref {
           type ac-svc:attachment-circuit-reference;
           description
             "Specifies the parent AC that is inherited by an AC.
              In contexts where dynamic terminating points are
              bound to the same AC, a parent AC with stable
              information is created with a set of child ACs
              to track dynamic AC information.";
         }
         leaf-list child-ac-ref {
           type ac-svc:attachment-circuit-reference;
           config false;
           description
             "Specifies a child AC that relies upon a parent AC.";
         }
         list group {
           key "group-id";

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           description
             "List of group-ids.";
           leaf group-id {
             type string;
             description
               "Indicates the group-id to which the network access
                belongs.";
           }
           leaf precedence {
             type identityref {
               base ac-common:precedence-type;
             }
             description
               "Defines redundancy of an AC.";
           }
         }
         list service-ref {
           key "service-type service-id";
           config false;
           description
             "Reports the set of services that are bound to the AC.";
           leaf service-type {
             type identityref {
               base vpn-common:service-type;
             }
             description
               "Indicates the service type (e.g., L3VPN, Network Slice
                Service).";
             reference
               "RFC 9408: A YANG Network Data Model for Service
                          Attachment Points (SAPs), Section 5";
           }
           leaf service-id {
             type string;
             description
               "Indicates an identifier of a service instance
                of a given type that uses the AC.";
           }
         }
         uses ac;
       }
     }
   }
   <CODE ENDS>

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6.  Security Considerations

   This section uses the template described in Section 3.7 of
   [I-D.ietf-netmod-rfc8407bis].

   The YANG modules specified 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 Network Configuration Access Control Model (NACM) [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.

   There are a number of data nodes defined in these YANG modules that
   are writable/creatable/deletable (i.e., config true, which is the
   default).  These data nodes may be considered sensitive or vulnerable
   in some network environments.  Write operations (e.g., edit-config)
   and delete operations to these data nodes without proper protection
   or authentication can have a negative effect on network operations.
   Specifically, the following subtrees and data nodes have particular
   sensitivities/vulnerabilities in the "ietf-bearer-svc" module:

   'placement-constraints':  An attacker who is able to access this data
      node can modify the attributes to influence how a service is
      delivered to a customer, and this lead to Service Level Agreement
      (SLA) violations.

   'bearer':  An attacker who is able to access this data node can
      modify the attributes of bearer and, thus, hinder how ACs are
      built.

      In addition, an attacker could attempt to add a new bearer or
      delete existing ones.  An attacker may also change the requested
      type or the activation scheduling.

   The following subtrees and data nodes have particular sensitivities/
   vulnerabilities in the "ietf-ac-svc" module:

   'specific-provisioning-profiles':  This container includes a set of
      sensitive data that influence how an AC will be delivered.  For
      example, an attacker who has access to these data nodes may be
      able to manipulate routing policies, QoS policies, or encryption
      properties.

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      These data nodes are defined with "nacm:default-deny-write"
      tagging [I-D.ietf-opsawg-teas-common-ac].

   'service-provisioning-profiles':  An attacker who has access to these
      data nodes may be able to manipulate service-specific policies to
      be applied for an AC.

      These data nodes are defined with "nacm:default-deny- write"
      tagging.

   'ac':  An attacker who is able to access this data node can modify
      the attributes of an AC (e.g., QoS, bandwidth, routing protocols,
      keying material), leading to malfunctioning of services that will
      be delivered over that AC and therefore to SLA violations.  In
      addition, an attacker could attempt to add a new AC.

   Some of the readable data nodes in these YANG modules may be
   considered sensitive or vulnerable in some network environments.  It
   is thus important to control read access (e.g., via get, get-config,
   or notification) to these data nodes.  Specifically, the following
   subtrees and data nodes have particular sensitivities/vulnerabilities
   in the "ietf-bearer-svc" module:

   'customer-point':  An attacker can retrieve privacy-related
      information about location from where the customer is connected.
      Disclosing such information may be used to infer the identity of
      the customer.

   The following subtrees and data nodes have particular sensitivities/
   vulnerabilities in the "ietf-ac-svc" module:

   'customer-name', 'l2-connection', and 'ip-connection':  An attacker
      can retrieve privacy-related information, which can be used to
      track a customer.  Disclosing such information may be considered a
      violation of the customer-provider trust relationship.

   'keying-material':  An attacker can retrieve the cryptographic keys
      protecting the underlying connectivity services (routing, in
      particular).  These keys could be used to inject spoofed routing
      advertisements.

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   Several data nodes ('bgp', 'ospf', 'isis', and 'rip') rely upon
   [RFC8177] for authentication purposes.  As such, the AC service
   module inherits the security considerations discussed in Section 5 of
   [RFC8177].  Also, these data nodes support supplying explicit keys as
   strings in ASCII format.  The use of keys in hexadecimal string
   format would afford greater key entropy with the same number of key-
   string octets.  However, such a format is not included in this
   version of the AC service model because it is not supported by the
   underlying device modules (e.g., [RFC8695]).

7.  IANA Considerations

   IANA is requested to register the following URIs in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

      URI:  urn:ietf:params:xml:ns:yang:ietf-bearer-svc
      Registrant Contact:  The IESG.
      XML:  N/A; the requested URI is an XML namespace.

      URI:  urn:ietf:params:xml:ns:yang:ietf-ac-svc
      Registrant Contact:  The IESG.
      XML:  N/A; the requested URI is an XML namespace.

   IANA is requested to register the following YANG modules in the "YANG
   Module Names" subregistry [RFC6020] within the "YANG Parameters"
   registry.

      Name:  ietf-bearer-svc
      Maintained by IANA?  N
      Namespace:  urn:ietf:params:xml:ns:yang:ietf-bearer-svc
      Prefix:  bearer-svc
      Reference:  RFC xxxx

      Name:  ietf-ac-svc
      Maintained by IANA?  N
      Namespace:  urn:ietf:params:xml:ns:yang:ietf-ac-svc
      Prefix:  ac-svc
      Reference:  RFC xxxx

8.  References

8.1.  Normative References

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   [I-D.ietf-opsawg-teas-common-ac]
              Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
              and B. Wu, "A Common YANG Data Model for Attachment
              Circuits", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-teas-common-ac-05, 9 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              teas-common-ac-05>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/rfc/rfc3688>.

   [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/rfc/rfc4364>.

   [RFC4552]  Gupta, M. and N. Melam, "Authentication/Confidentiality
              for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
              <https://www.rfc-editor.org/rfc/rfc4552>.

   [RFC4577]  Rosen, E., Psenak, P., and P. Pillay-Esnault, "OSPF as the
              Provider/Customer Edge Protocol for BGP/MPLS IP Virtual
              Private Networks (VPNs)", RFC 4577, DOI 10.17487/RFC4577,
              June 2006, <https://www.rfc-editor.org/rfc/rfc4577>.

   [RFC5709]  Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
              Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
              Authentication", RFC 5709, DOI 10.17487/RFC5709, October
              2009, <https://www.rfc-editor.org/rfc/rfc5709>.

   [RFC5798]  Nadas, S., Ed., "Virtual Router Redundancy Protocol (VRRP)
              Version 3 for IPv4 and IPv6", RFC 5798,
              DOI 10.17487/RFC5798, March 2010,
              <https://www.rfc-editor.org/rfc/rfc5798>.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
              <https://www.rfc-editor.org/rfc/rfc5880>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/rfc/rfc6020>.

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   [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/rfc/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/rfc/rfc6242>.

   [RFC6565]  Pillay-Esnault, P., Moyer, P., Doyle, J., Ertekin, E., and
              M. Lundberg, "OSPFv3 as a Provider Edge to Customer Edge
              (PE-CE) Routing Protocol", RFC 6565, DOI 10.17487/RFC6565,
              June 2012, <https://www.rfc-editor.org/rfc/rfc6565>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/rfc/rfc6991>.

   [RFC7166]  Bhatia, M., Manral, V., and A. Lindem, "Supporting
              Authentication Trailer for OSPFv3", RFC 7166,
              DOI 10.17487/RFC7166, March 2014,
              <https://www.rfc-editor.org/rfc/rfc7166>.

   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
              "Security Extension for OSPFv2 When Using Manual Key
              Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
              <https://www.rfc-editor.org/rfc/rfc7474>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/rfc/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

   [RFC8177]  Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
              Zhang, "YANG Data Model for Key Chains", RFC 8177,
              DOI 10.17487/RFC8177, June 2017,
              <https://www.rfc-editor.org/rfc/rfc8177>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8341>.

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   [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/rfc/rfc8342>.

   [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/rfc/rfc8446>.

   [RFC9181]  Barguil, S., Gonzalez de Dios, O., Ed., Boucadair, M.,
              Ed., and Q. Wu, "A Common YANG Data Model for Layer 2 and
              Layer 3 VPNs", RFC 9181, DOI 10.17487/RFC9181, February
              2022, <https://www.rfc-editor.org/rfc/rfc9181>.

   [RFC9182]  Barguil, S., Gonzalez de Dios, O., Ed., Boucadair, M.,
              Ed., Munoz, L., and A. Aguado, "A YANG Network Data Model
              for Layer 3 VPNs", RFC 9182, DOI 10.17487/RFC9182,
              February 2022, <https://www.rfc-editor.org/rfc/rfc9182>.

   [RFC9291]  Boucadair, M., Ed., Gonzalez de Dios, O., Ed., Barguil,
              S., and L. Munoz, "A YANG Network Data Model for Layer 2
              VPNs", RFC 9291, DOI 10.17487/RFC9291, September 2022,
              <https://www.rfc-editor.org/rfc/rfc9291>.

   [RFC9408]  Boucadair, M., Ed., Gonzalez de Dios, O., Barguil, S., Wu,
              Q., and V. Lopez, "A YANG Network Data Model for Service
              Attachment Points (SAPs)", RFC 9408, DOI 10.17487/RFC9408,
              June 2023, <https://www.rfc-editor.org/rfc/rfc9408>.

8.2.  Informative References

   [I-D.ietf-idr-bgp-model]
              Jethanandani, M., Patel, K., Hares, S., and J. Haas, "YANG
              Model for Border Gateway Protocol (BGP-4)", Work in
              Progress, Internet-Draft, draft-ietf-idr-bgp-model-17, 5
              July 2023, <https://datatracker.ietf.org/doc/html/draft-
              ietf-idr-bgp-model-17>.

   [I-D.ietf-netmod-rfc8407bis]
              Bierman, A., Boucadair, M., and Q. Wu, "Guidelines for
              Authors and Reviewers of Documents Containing YANG Data
              Models", Work in Progress, Internet-Draft, draft-ietf-
              netmod-rfc8407bis-09, 28 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-09>.

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   [I-D.ietf-opsawg-ntw-attachment-circuit]
              Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
              and B. Wu, "A Network YANG Data Model for Attachment
              Circuits", Work in Progress, Internet-Draft, draft-ietf-
              opsawg-ntw-attachment-circuit-05, 9 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ntw-attachment-circuit-05>.

   [I-D.ietf-teas-ietf-network-slice-nbi-yang]
              Wu, B., Dhody, D., Rokui, R., Saad, T., and J. Mullooly,
              "A YANG Data Model for the RFC AAAA Network Slice
              Service", Work in Progress, Internet-Draft, draft-ietf-
              teas-ietf-network-slice-nbi-yang-09, 17 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              ietf-network-slice-nbi-yang-09>.

   [IEEE802.1AX]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks--Link Aggregation", May 2020,
              <https://doi.org/10.1109/IEEESTD.2020.9105034>.

   [Instance-Data]
              "Example of AC SVC Instance Data", 2024,
              <https://github.com/boucadair/attachment-circuit-
              model/blob/main/xml-examples/svc-full-instance.xml>.

   [ITU-T-G.781]
              ITU-T, "Synchronization layer functions for frequency
              synchronization based on the physical layer", January
              2024, <https://www.itu.int/rec/T-REC-G.781>.

   [PYANG]    "pyang", 2023, <https://github.com/mbj4668/pyang>.

   [RFC2080]  Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
              DOI 10.17487/RFC2080, January 1997,
              <https://www.rfc-editor.org/rfc/rfc2080>.

   [RFC2453]  Malkin, G., "RIP Version 2", STD 56, RFC 2453,
              DOI 10.17487/RFC2453, November 1998,
              <https://www.rfc-editor.org/rfc/rfc2453>.

   [RFC3644]  Snir, Y., Ramberg, Y., Strassner, J., Cohen, R., and B.
              Moore, "Policy Quality of Service (QoS) Information
              Model", RFC 3644, DOI 10.17487/RFC3644, November 2003,
              <https://www.rfc-editor.org/rfc/rfc3644>.

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   [RFC3849]  Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
              Reserved for Documentation", RFC 3849,
              DOI 10.17487/RFC3849, July 2004,
              <https://www.rfc-editor.org/rfc/rfc3849>.

   [RFC5398]  Huston, G., "Autonomous System (AS) Number Reservation for
              Documentation Use", RFC 5398, DOI 10.17487/RFC5398,
              December 2008, <https://www.rfc-editor.org/rfc/rfc5398>.

   [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
              Reserved for Documentation", RFC 5737,
              DOI 10.17487/RFC5737, January 2010,
              <https://www.rfc-editor.org/rfc/rfc5737>.

   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <https://www.rfc-editor.org/rfc/rfc5925>.

   [RFC6151]  Turner, S. and L. Chen, "Updated Security Considerations
              for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
              RFC 6151, DOI 10.17487/RFC6151, March 2011,
              <https://www.rfc-editor.org/rfc/rfc6151>.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013,
              <https://www.rfc-editor.org/rfc/rfc6952>.

   [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/rfc/rfc7665>.

   [RFC8299]  Wu, Q., Ed., Litkowski, S., Tomotaki, L., and K. Ogaki,
              "YANG Data Model for L3VPN Service Delivery", RFC 8299,
              DOI 10.17487/RFC8299, January 2018,
              <https://www.rfc-editor.org/rfc/rfc8299>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8340>.

   [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/rfc/rfc8349>.

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   [RFC8466]  Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG
              Data Model for Layer 2 Virtual Private Network (L2VPN)
              Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October
              2018, <https://www.rfc-editor.org/rfc/rfc8466>.

   [RFC8695]  Liu, X., Sarda, P., and V. Choudhary, "A YANG Data Model
              for the Routing Information Protocol (RIP)", RFC 8695,
              DOI 10.17487/RFC8695, February 2020,
              <https://www.rfc-editor.org/rfc/rfc8695>.

   [RFC8969]  Wu, Q., Ed., Boucadair, M., Ed., Lopez, D., Xie, C., and
              L. Geng, "A Framework for Automating Service and Network
              Management with YANG", RFC 8969, DOI 10.17487/RFC8969,
              January 2021, <https://www.rfc-editor.org/rfc/rfc8969>.

Appendix A.  Examples

   This section includes a non-exhaustive list of examples to illustrate
   the use of the service models defined in this document.  An example
   instance data can also be found at [Instance-Data].

A.1.  Create A New Bearer

   An example of a request message body to create a bearer is shown in
   Figure 21.

   {
     "ietf-bearer-svc:bearers": {
       "bearer": [
         {
           "name": "a-name-choosen-by-client",
           "description": "A bearer example",
           "customer-point": {
             "device": {
               "device-id": "CE_X_SITE_Y"
             }
           },
           "type": "ietf-bearer-svc:ethernet"
         }
       ]
     }
   }

        Figure 21: Example of a Message Body to Create A New Bearer

   A bearer-reference is then generated by the controller for this
   bearer.  Figure 22 shows the example of a response message body that
   is sent by the controller to reply to a GET request:

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   {
     "ietf-bearer-svc:bearers": {
       "bearer": [
         {
           "name": "a-name-choosen-by-client",
           "description": "A bearer example",
           "sync-phy-capable": true,
           "customer-point": {
             "device": {
               "device-id": "CE_X_SITE_Y"
             }
           },
           "type": "ietf-bearer-svc:ethernet",
           "bearer-reference": "line-156"
         }
       ]
     }
   }

       Figure 22: Example of a Response Message Body with the Bearer
                                 Reference

   Note that the response also indicates that Sync Phy is supported for
   this bearer.

A.2.  Create An AC over An Existing Bearer

   An example of a request message body to create a simple AC over an
   existing bearer is shown in Figure 23.  The bearer reference is
   assumed to be known to both the customer and the network provider.
   Such a reference can be retrieved, e.g., following the example
   described in Appendix A.1 or using other means (including, exchanged
   out-of-band or via proprietary APIs).

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   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac4585",
           "description": "An AC on an existing bearer",
           "requested-ac-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q"
             },
             "bearer-reference": "line-156"
           }
         }
       ]
     }
   }

       Figure 23: Example of a Message Body to Request an AC over an
                              Existing Bearer

   Figure 24 shows the message body of a response received from the
   controller and which indicates the "cvlan-id" that was assigned for
   the requested AC.

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac4585",
           "description": "An AC on an existing bearer",
           "requested-ac-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "tag-type": "ietf-vpn-common:c-vlan",
                 "cvlan-id": 550
               }
             },
             "bearer-reference": "line-156"
           }
         }
       ]
     }
   }

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       Figure 24: Example of a Message Body of a Response to Assign a
                                  CVLAN ID

A.3.  Create An AC for a Known Peer SAP

   An example of a request to create a simple AC, when the peer SAP is
   known, is shown in Figure 25.  In this example, the peer SAP
   identifier points to an identifier of a service function.  The
   (topological) location of that service function is assumed to be
   known to the network controller.  For example, this can be determined
   as part of an on-demand procedure to instantiate a service function
   in a cloud.  That instantiated service function can be granted a
   connectivity service via the provider network.

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac4585",
           "description": "An AC on an existing bearer",
           "requested-ac-start": "2023-12-12T05:00:00.00Z",
           "peer-sap-id": [
             "nf-termination-ip"
           ],
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "tag-type": "ietf-vpn-common:c-vlan",
                 "cvlan-id": 550
               }
             }
           }
         }
       ]
     }
   }

   Figure 25: Example of a Message Body to Request an AC with a Peer SAP

A.4.  One CE, Two ACs

   Let’s consider the example of an eNodeB (CE) that is directly
   connected to the access routers of the mobile backhaul (see
   Figure 26).  In this example, two ACs are needed to service the
   eNodeB (e.g., distinct VLANs for Control and User Planes).

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   .-------------.                  .------------------.
   |             |                  | PE               |
   |             |                  |  192.0.2.1       |
   |   eNodeB    |==================|  2001:db8::1     |
   |             |          VLAN 1  |                  |
   |             |==================|                  |
   |             |          VLAN 2  |                  |
   |             | Direct           |                  |
   '-------------' Routing          |                  |
                                    |                  |
                                    |                  |
                                    |                  |
                                    '------------------'

                     Figure 26: Example of a CE-PE ACs

   An example of a request to create the ACs to service the eNodeB is
   shown in Figure 27.  This example assumes that static addressing is
   used for both ACs.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
      "ietf-ac-svc:attachment-circuits":{
         "ac":[
            {
               "name":"ac1",
               "description":"a first ac with a same peer node",
               "l2-connection":{
                  "encapsulation":{
                     "type":"ietf-vpn-common:dot1q"
                  },
                  "bearer-reference":"line-156"
               },
               "ip-connection":{
                  "ipv4":{
                     "address-allocation-type":"ietf-ac-common:static-\
                                                                address"
                  },
                  "ipv6":{
                     "address-allocation-type":"ietf-ac-common:static-\
                                                                address"
                  },
                  "routing-protocols":{
                     "routing-protocol":[
                        {
                           "id":"1",
                           "type":"ietf-vpn-common:direct-routing"

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                        }
                     ]
                  }
               }
            },
            {
               "name":"ac2",
               "description":"a second ac with a same peer node",
               "l2-connection":{
                  "encapsulation":{
                     "type":"ietf-vpn-common:dot1q"
                  },
                  "bearer-reference":"line-156"
               },
               "ip-connection":{
                  "ipv4":{
                     "address-allocation-type":"ietf-ac-common:static-\
                                                                address"
                  },
                  "ipv6":{
                     "address-allocation-type":"ietf-ac-common:static-\
                                                                address"
                  },
                  "routing-protocols":{
                     "routing-protocol":[
                        {
                           "id":"1",
                           "type":"ietf-vpn-common:direct-routing"
                        }
                     ]
                  }
               }
            }
         ]
      }
   }

       Figure 27: Example of a Message Body to Request Two ACs on The
                        Same Link (Not Recommended)

   Figure 28 shows the message body of a response received from the
   controller.

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   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac1",
           "description": "a first ac with a same peer node",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "cvlan-id": 1
               }
             },
             "bearer-reference": "line-156"
           },
           "ip-connection": {
             "ipv4": {
               "local-address": "192.0.2.1",
               "prefix-length": 30,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.2"
                 }
               ]
             },
             "ipv6": {
               "local-address": "2001:db8::1",
               "prefix-length": 64,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "2001:db8::2"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:direct-routing"
               }
             ]
           }
         },
         {
           "name": "ac2",

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           "description": "a second ac with a same peer node",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "cvlan-id": 2
               }
             },
             "bearer-reference": "line-156"
           },
           "ip-connection": {
             "ipv4": {
               "local-address": "192.0.2.1",
               "prefix-length": 30,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.2"
                 }
               ]
             },
             "ipv6": {
               "local-address": "2001:db8::1",
               "prefix-length": 64,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "2001:db8::2"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:direct-routing"
               }
             ]
           }
         }
       ]
     }
   }

      Figure 28: Example of a Message Body of a Response to Create Two
                   ACs on The Same Link (Not Recommended)

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   The example shown Figure 28 is not optimal as it includes many
   redundant data.  Figure 29 shows a more compact request that
   factorizes all the redundant data.

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac-group-profile": [
         {
           "id": "simple-node-profile",
           "l2-connection": {
             "bearer-reference": "line-156"
           },
           "ip-connection": {
             "ipv4": {
               "local-address": "192.0.2.1",
               "prefix-length": 30,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.2"
                 }
               ]
             },
             "ipv6": {
               "local-address": "2001:db8::1",
               "prefix-length": 64,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "2001:db8::2"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:direct-routing"
               }
             ]
           }
         }
       ],
       "ac": [
         {
           "name": "ac1",
           "description": "a first ac with a same peer node",

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           "ac-group-profile": ["simple-node-profile"],
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "cvlan-id": 1
               }
             }
           }
         },
         {
           "name": "ac2",
           "description": "a second ac with a same peer node",
           "ac-group-profile": ["simple-node-profile"],
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "cvlan-id": 2
               }
             }
           }
        }
       ]
     }
   }

       Figure 29: Example of a Message Body to Request Two ACs on The
                          Same Link (Node Profile)

   A customer may request adding a new AC by simply referring to an
   existing per-node AC profile as shown in Figure 30.  This AC inherits
   all the data that was enclosed in the indicated per-node AC profile
   (IP addressing, routing, etc.).

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   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac3",
           "description": "a third AC with a same peer node",
           "ac-group-profile": [
             "simple-node-profile"
           ],
           "l2-connection": {
             "encapsulation": {
               "dot1q": {
                 "cvlan-id": 3
               }
             },
             "bearer-reference": "line-156"
           }
         }
       ]
     }
   }

        Figure 30: Example of a Message Body to Add a new AC over an
                        existing link (Node Profile)

A.5.  Control Precedence over Multiple ACs

   When multiple ACs are requested by the same customer for the same
   site, the request can tag one of these ACs as "primary" and the other
   ones as "secondary".  An example of such a request is shown in
   Figure 32.  In this example, both ACs are bound to the same "group-
   id", and the "precedence" data node is set as a function of the
   intended role of each AC (primary or secondary).

                                    .---.
                    ac1: primary    |   |
               .--------------------+PE1|
   .---.       |    bearerX@site1   |   |
   |   +-------'                    '---'
   |CE |
   |   +-------.                    .---.
   '---'       |    ac2: secondary  |   |
               '--------------------+PE2|
                    bearerY@site1   |   |
                                    '---'

        Figure 31: An Example Topology for AC Precedence Enforcement

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   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac1",
           "description": "Example to illustrate AC precedence usage",
           "group": [
             {
               "group-id": "1",
               "precedence": "ietf-ac-common:primary"
             }
           ],
           "l2-connection": {
             "bearer-reference": "bearerX@site1"
           }
         },
         {
           "name": "ac2",
           "description": "Example to illustrate AC precedence usage",
           "group": [
             {
               "group-id": "1",
               "precedence": "ietf-ac-common:secondary"
             }
           ],
           "l2-connection": {
             "bearer-reference": "bearerY@site1"
           }
         }
       ]
     }
   }

       Figure 32: Example of a Message Body to Associate a Precedence
                               Level with ACs

A.6.  Create Multiple ACs Bound to Multiple CEs

   Figure 33 shows an example of CEs that are interconnected by a
   service provider network.

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                      .----------------------------------.
         .----.       |                                  |       .----.
         | CE1+-------+                                  +-------+ CE3|
         '----'       |                                  |       '----'
                      |              Network             |
         .----.       |                                  |       .----.
         |CE2 +-------+                                  +-------+ CE4|
         '----'       |                                  |       '----'
                      '----------------------------------'

                    Figure 33: Network Topology Example

   Figure 34 depicts an example of the message body of a response to a
   request to instantiate the various ACs that are shown in Figure 33.

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac-group-profile": [
         {
           "id": "simple-profile",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "cvlan-id": 1
               }
             }
           }
         }
       ],
       "ac": [
         {
           "name": "ac1",
           "description": "First site",
           "ac-group-profile": [
             "simple-profile"
           ],
           "l2-connection": {
             "bearer-reference": "ce1-network"
           }
         },
         {
           "name": "ac2",
           "description": "Second Site",
           "ac-group-profile": [
             "simple-profile"
           ],
           "l2-connection": {

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             "bearer-reference": "ce2-network"
           }
         },
         {
           "name": "ac3",
           "description": "Third site",
           "ac-group-profile": [
             "simple-profile"
           ],
           "l2-connection": {
             "bearer-reference": "ce3-network"
           }
         },
         {
           "name": "ac4",
           "description": "Another site",
           "ac-group-profile": [
             "simple-profile"
           ],
           "l2-connection": {
             "bearer-reference": "ce4-network"
           }
         }
       ]
     }
   }

        Figure 34: Example of a Message Body of a Request to Create
                     Multiple ACs bound to Multiple CEs

A.7.  Binding Attachment Circuits to an IETF Network Slice

   This example shows how the AC service model complements
   [I-D.ietf-teas-ietf-network-slice-nbi-yang] to connect a site to a
   slice service.

   First, Figure 35 describes the end-to-end network topology as well
   the orchestration scopes:

   *  The topology is made up of two sites (site1 and site2),
      interconnected via a Transport Network (e.g.  IP/MPLS Network).  A
      Network Function is deployed within each site in a dedicated IP
      Subnet.

   *  A 5G SMO is responsible for the deployment Network Functions and
      the indirect management of a local Gateway (i.e., CE device).

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   *  An IETF Network Slice Controller is responsible for the deployment
      of IETF Network Slices across the TN.

   Network Functions are deployed within each site.

         5G SMO                 IETF NSC                 5G SMO
            |               (TN Orchestrator)               |
            |                        |                      |
      <-----+----->        <---------+-------->        <----+---->
          Site1             Transport Network              Site2
      .---.                  .--------------.                 .---.
      │NF1│                  |              |                 │NF2│
      '-+-'   .---.        .---.          .---.        .---.  '-+-'
        |     |   |        │   │          │   │        │   │    |
      --+-----+GW1+--------+PE1│          │PE2+--------+GW2+----+--
          ^   |   |    ^   |   |          │   │   ^    │   │  ^
          |   '---'    |   '-+-'          '-+-'   |    '---'  |
          |            |     │              │     |           |
          |            |     '--------------'     |           |
        LAN1           |                          |          LAN2
   198.51.100.0/24     |                          |  203.0.113.0/24
                       |                          |
                       |                          |
               Physical Link ID:           Physical Link ID:
                 bearerX@site1               bearerX@site2

     Figure 35: An Example of a Network Topology Used to Deploy Slices

   Figure 36 describes the logical connectivity enforced thanks to both
   IETF Network Slice and Attachment Circuit models.

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                                AS 65536  <----BGP--> AS 65550
    .---.                     .--------.                    .---.
    │NF1│       192.0.2.0/30  |        |   192.0.2.4/30     │NF2│
    '-+-'   .---.          .--+.      .+--.          .---.  '-+-'
      |     |   |.1      .2|   |      |   |.6      .5|   |    |
    --+-----+GW1+----------+PE1|      |PE2+----------+GW2+----+----
            |   | vlan-id  |   |      |   | vlan-id  |   |
            '---'   100    '--+'      '+--'   200    '---'
   198.51.100.0/24            |        |             203.0.113.0/24
                              '--------+'
                            sdp1      sdp2
                <----------> <------------> <------->
                Attachment   Network Slice   Attachment
                Circuit "ac1"    EMBB_UP     Circuit "ac2"

    * "ac1" properties:
    - bearer-reference: bearerX@site1
    - vlan-id: 100
    - CE address (GW1): 192.0.2.1/30
    - PE address: 192.0.2.2/30
    - Routing: static 198.51.100.0/24 via
               192.0.2.1 tag primary_UP_slice

    * "ac2" properties:
    - bearer-reference: bearerY@site2
    - vlan-id: 200
    - CE address (GW2): 192.0.2.5/30
    - PE address: 192.0.2.6/30
    - Routing: BGP local-as: 65536
                   customer-as: 65550
                   customer-address: 192.0.2.5

                        Figure 36: Logical Overview

   Figure 37 shows the message body of the request to create the
   required ACs using the Attachment Circuit module.

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
      "ietf-ac-svc:attachment-circuits":{
         "ac":[
            {
               "name":"ac1",
               "description":"Connection to site1 on vlan 100",
               "requested-start":"2023-12-12T05:00:00.00Z",
               "l2-connection":{
                  "encapsulation":{

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                     "type":"ietf-vpn-common:dot1q",
                     "dot1q":{
                        "tag-type":"ietf-vpn-common:c-vlan"
                     },
                     "bearer-reference":"bearerX@site1"
                  },
                  "ip-connection":{
                     "ipv4":{
                        "address-allocation-type":"ietf-ac-common:\
                                                         static-address"
                     },
                     "routing-protocols":{
                        "routing-protocol":[
                           {
                              "id":"1",
                              "type":"ietf-vpn-common:static-routing",
                              "static":{
                                 "cascaded-lan-prefixes":{
                                    "ipv4-lan-prefixes":[
                                       {
                                          "lan":"198.51.100.0/24",
                                          "next-hop":"192.0.2.1",
                                          "lan-tag":"primary_UP_slice"
                                       }
                                    ]
                                 }
                              }
                           }
                        ]
                     }
                  }
               }
            },
            {
               "name":"ac2",
               "description":"Connection to site2 on vlan 200",
               "requested-start":"2023-12-12T05:00:00.00Z",
               "l2-connection":{
                  "encapsulation":{
                     "type":"ietf-vpn-common:dot1q",
                     "dot1q":{
                        "tag-type":"ietf-vpn-common:c-vlan"
                     }
                  },
                  "bearer-reference":"bearerY@site2"
               },
               "ip-connection":{
                  "ipv4":{

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                     "address-allocation-type":"ietf-ac-common:static-\
                                                                address"
                  },
                  "routing-protocols":{
                     "routing-protocol":[
                        {
                           "id":"1",
                           "type":"ietf-vpn-common:bgp-routing",
                           "bgp":{
                              "neighbor":[
                                 {
                                    "id":"1",
                                    "peer-as":65550
                                 }
                              ]
                           }
                        }
                     ]
                  }
               }
            }
         ]
      }
   }

        Figure 37: Message Body of a Request to Create Required ACs

   Figure 38 shows the message body of a reponse received from the
   controller.

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac1",
           "description": "Connection to site1 on vlan 100",
           "requested-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "tag-type": "ietf-vpn-common:c-vlan",
                 "cvlan-id": 100
               }
             },
             "bearer-reference": "bearerX@site1"
           },
           "ip-connection": {

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             "ipv4": {
               "local-address": "192.0.2.2",
               "prefix-length": 30,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.1"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:static-routing",
                 "static": {
                   "cascaded-lan-prefixes": {
                     "ipv4-lan-prefixes": [
                       {
                         "lan": "198.51.100.0/24",
                         "next-hop": "192.0.2.1",
                         "lan-tag": "primary_UP_slice"
                       }
                     ]
                   }
                 }
               }
             ]
           }
         },
         {
           "name": "ac2",
           "description": "Connection to site2 on vlan 200",
           "requested-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "tag-type": "ietf-vpn-common:c-vlan",
                 "cvlan-id": 200
               }
             },
             "bearer-reference": "bearerY@site2"
           },
           "ip-connection": {
             "ipv4": {
               "local-address": "192.0.2.6",

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               "prefix-length": 30,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.5"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:bgp-routing",
                 "bgp": {
                   "neighbor": [
                     {
                       "id": "1",
                       "peer-as": 65550,
                       "local-as": 65536
                     }
                   ]
                 }
               }
             ]
           }
         }
       ]
     }
   }

     Figure 38: Example of a Message Body of a Response Indicating the
                            Creation of the ACs

   Figure 39 shows the message body of the request to create the a slice
   service bound to the ACs created using Figure 37.  Only references to
   these ACs are included in the Slice Service request.  This example
   assumes that the module that "glues" the service/AC is also supported
   by the NSC.

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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-network-slice-service:network-slice-services": {
       "slo-sle-templates": {
         "slo-sle-template": [
           {
             "id": "low-latency-template",
             "template-description": "Lowest possible latencey \
                                                    forwarding behavior"
           }
         ]
       },
       "slice-service": [
         {
           "service-id": "Slice URLLC_UP",
           "service-description": "Dedicate TN Slice for URLLC-UP",
           "slo-sle-template": "low-latency-template",
           "status": {},
           "sdps": {
             "sdp": [
               {
                 "sdp-id": "sdp1",
                 "ac-svc-name": ["ac1"]
               },
               {
                 "sdp-id": "sdp2",
                 "ac-svc-name": ["ac2"]
               }
             ]
           }
         }
       ]
     }
   }

       Figure 39: Message Body of a Request to Create a Slice Service
                            Referring to the ACs

A.8.  Connecting a Virtualized Environment Running in a Cloud Provider

   This example (Figure 40) shows how the AC service model can be used
   to connect a Cloud Infrastructure to a service provider network.
   This example makes the following assumptions:

   1.  A customer (e.g., Mobile Network Team or partner) has a
       virtualized infrastructure running in a Cloud Provider.  A
       simplistic deployment is represented here with a set of Virtual

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       Machines running in a Virtual Private Environment.  The
       deployment and management of this infrastructure is achieved via
       private APIs that are supported by the Cloud Provider: this
       realization is out of the scope of this document.

   2.  The connectivity to the Data Center is achieved thanks to a
       service based on direct attachment (physical connection), which
       is delivered upon ordering via an API exposed by the Cloud
       Provider.  When ordering that connection, a unique "Connection
       Identifier" is generated and returned via the API.

   3.  The customer provisions the networking logic within the Cloud
       Provider based on that unique connection Identifier (i.e.,
       logical interfaces, IP addressing, and routing).

       .--------------------------------------------------------.
       |                                      Cloud Provider DC |
       |                                                        |
       |  .---. .---. .---.                                     |
       |  │VM1│ │VM2│ │VM3│  Virtual Private Cloud              |
       |  '-+-' '-+-' '-+-'                                     |
       |    │.2   │.5   │.12      198.51.100.0/24               |
       |   -+-----+-----+---+-----------------------            |
       |                    │.1                                 |
       |                .---+----.                              |
       |                │ CLOUD  │ BGP_ASN: 65536               |
       |                │PROVIDER│ BGP md5:                     |
       |                │   GW   │   "nyxNER_c5sdn608fFQl3331d" |
       |                '---+----'                              |
       |                    │ ^ .2                              |
       '--------------------│-│---------------------------------'
                            │ │
    Direct Interconnection  │ │
    connection_id:          │BGP       vlan-id:50
      1234-56789            │ │        192.0.2.0/24
                            │ │
                            │ │ .1
       .--------------------│-v---------------------------------.
       |             If-A.--+--.       Service Provider Network |
       |                 │     │                                |
       |                 │ PE1 │ BGP_ASN: 65550                 |
       |                 │     │                                |
       |                 '-----'                                |
       |                                                        |
       |                                                        |
       |                                                        |
       '--------------------------------------------------------'

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      Figure 40: An Example of Realization for Connecting a Cloud Site

   Figure 41 illustrates the pre-provisioning logic for the physical
   connection to the Cloud Provider.  After this connection is delivered
   to the service provider, the network inventory is updated with
   "bearer-reference" set to the value of the "Connection Identifier".

  Customer                                                       Cloud
Orchestration  DIRECT INTERCONNECTION ORDERING (API)            Provider
               ------------------------------------------------>

               Connection Created with "Connection ID:1234-56789"
               <------------------------------------------------
                                        x
                                        x
                                        x
                                        x

       Physical Connection 1234-56789 is delivered and
                         connected to PE1

       Network  Inventory Updated with:
         bearer-reference: 1234-56789 for PE1/Interface If-A

             Figure 41: Illustration of Pre-provisioning

   Next, API workflows can be initiated:

   *  Cloud Provider for the configuration as per (3) above.

   *  Service provider network via the Attachment Circuit model.  This
      request can be used in conjunction with additional requests based
      on L3SM (VPN provisioning) or Network Slice Service model (5G
      hybrid Cloud deployment).

   Figure 42 shows the message body of the request to create the
   required ACs to connect the Cloud Provider Virtualized (VM) using the
   Attachment Circuit module.

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   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac--BXT-DC-customer-VPC-foo",
           "description": "Connection to Cloud Provider BXT on \
                                                 connection 1234-56789",
           "requested-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q"
             },
             "bearer-reference": "1243-56789"
           },
           "ip-connection": {
             "ipv4": {
               "address-allocation-type": "ietf-ac-common:static-\
                                                                address"
             },
             "routing-protocols": {
               "routing-protocol": [
                 {
                   "id": "1",
                   "type": "ietf-vpn-common:bgp-routing",
                   "bgp": {
                     "neighbor": [
                       {
                         "id": "1",
                         "peer-as": 65536
                       }
                     ]
                   }
                 }
               ]
             }
           }
         }
       ]
     }
   }

         Figure 42: Message Body of a Request to Create the ACs for
                      Connecting to the Cloud Provider

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   Figure 43 shows the message body of the response received from the
   provider.  Note that this Cloud Provider mandates the use of MD5
   authentication for establishing BGP connections.

      The module supports MD5 to basically accommodate the installed BGP
      base (including by some Cloud Providers).  Note that MD5 suffers
      from the security weaknesses discussed in Section 2 of [RFC6151]
      and Section 2.1 of [RFC6952].

   =============== NOTE: '\' line wrapping per RFC 8792 ================

   {
     "ietf-ac-svc:attachment-circuits": {
       "ac": [
         {
           "name": "ac--BXT-DC-customer-VPC-foo",
           "description": "Connection to Cloud Provider BXT on \
                                                 connection 1234-56789",
           "requested-start": "2023-12-12T05:00:00.00Z",
           "l2-connection": {
             "encapsulation": {
               "type": "ietf-vpn-common:dot1q",
               "dot1q": {
                 "tag-type": "ietf-vpn-common:c-vlan",
                 "cvlan-id": 50
               }
             },
             "bearer-reference": "1243-56789"
           },
           "ip-connection": {
             "ipv4": {
               "local-address": "192.0.2.1",
               "prefix-length": 24,
               "address": [
                 {
                   "address-id": "1",
                   "customer-address": "192.0.2.2"
                 }
               ]
             }
           },
           "routing-protocols": {
             "routing-protocol": [
               {
                 "id": "1",
                 "type": "ietf-vpn-common:bgp-routing",
                 "bgp": {
                   "neighbor": [

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                     {
                       "id": "1",
                       "peer-as": 65536,
                       "local-as": 65550,
                       "authentication": {
                         "keying-material": {
                           "md5-keychain": "nyxNER_c5sdn608fFQl3331d"
                         }
                       }
                     }
                   ]
                 }
               }
             ]
           }
         }
       ]
     }
   }

       Figure 43: Message Body of a Response to the Request to Create
                  ACs for Connecting to the Cloud Provider

A.9.  Connect Customer Network (CE) Through BGP

   CE-PE routing using BGP is a common scenario in the context of MPLS
   VPNs and is widely used in enterprise networks.  In the example
   depicted in Figure 44, the CE routers are customer-owned devices
   belonging to an Autonomous System (ASN 65536).  CEs are located at
   the edge of the provider's network (PE, or Provider Edge) and use
   point-to-point interfaces to establish BGP sessions.  The point-to-
   point interfaces rely upon a physical bearer (Line-113) to reach the
   provider network.

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  +------------------------+                       +-------------------+
  |  Provider Network      |                       | Customer Network  |
  |                        |                       |                   |
  |        +------------+  |  Attachment-Circuit 1 | +-------+         |
  |        | PE1(VRF11) +----------------------------+ CE1   | AS65536 |
  |        |            |  |    Bearer=Line-113    | +-------+         |
  |        | PE1(VRF12) |  |                       |                   |
  |        |            |  |                       +-------------------+
  |        | PE1(VRF1n) |  |
  |        |            |  |
  |        +------------+  |
  | AS1                    |
  |        +------------+  |
  |        | PE2(VRF21) |  |
  |        +------------+  |
  |              .         |
  |              .         |
  |              .         |
  |        +------------+  |
  |        | PEm(VRFmn) |  |
  |        +------------+  |
  |                        |
  +------------------------+

           Figure 44: Illustration of Provider Network Scenario

   The attachment circuit in this case uses a SAP identifier to refer to
   the physical interface used for the connection between the PE and the
   CE.  The attachment circuit includes all the additional logical
   attributes to describe the connection between the two ends, including
   VLAN information and IP addressing.  Also, the configuration details
   of the BGP session makes use of peer group details instead of
   defining the entire configuration inside the 'neighbor' data node.

   {
      "attachment-circuits":{
         "ac":{
            "name":"IPT-CUST-ABC",
            "customer-name":"CUST-ABC",
            "description":"CUST-ABC-113",
            "peer-sap-id":"sap#113",
            "ip-connection":{
               "ipv4":{
                  "local-address":"192.0.2.1",
                  "prefix-length":30,
                  "address-allocation-type":"ac-common:static-address"
               }
            },

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            "l2-connection":{
               "encapsulation":{
                  "dot1q":{
                     "tag-type":"vpn-common:c-vlan",
                     "cvlan-id":"113"
                  }
               },
               "bearer-reference":"line-113"
            },
            "routing-protocols":{
               "routing-protocol":{
                  "id":"BGP-Single-Access",
                  "type":"vpn-common:bgp-routing",
                  "bgp":{
                     "peer-groups":{
                        "peer-group":{
                           "name":"IPT-CUST-ABC",
                           "peer-as":65536,
                           "address-family":"vpn-common:ipv4"
                        }
                     },
                     "neighbor":{
                        "id":"BGP-DIA-Single-1",
                        "remote-address":"192.0.2.2",
                        "peer-group":"IPT-CUST-ABC",
                        "status":{
                           "admin-status":{
                              "status":"vpn-common:admin-up"
                           }
                        }
                     }
                  }
               }
            }
         }
      }
   }

     Figure 45: Message Body of a Request to Create ACs for Connecting
                         CEs to a Provider Network

   This scenario allows the provider to maintain a list of ACs belonging
   to the same customer without requiring the full service
   configuration.

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Acknowledgments

   The document leverages [RFC9182] and [RFC9291].

   Thanks to Ebben Aries for the YANG Doctors review and for providing
   [Instance-Data].

Contributors

   Victor Lopez
   Nokia
   Email: victor.lopez@nokia.com

   Ivan Bykov
   Ribbon Communications
   Email: Ivan.Bykov@rbbn.com

   Qin Wu
   Huawei
   Email: bill.wu@huawei.com

   Kenichi Ogaki
   KDDI
   Email: ke-oogaki@kddi.com

   Luis Angel Munoz
   Vodafone
   Email: luis-angel.munoz@vodafone.com

Authors' Addresses

   Mohamed Boucadair (editor)
   Orange
   Email: mohamed.boucadair@orange.com

   Richard Roberts (editor)
   Juniper
   Email: rroberts@juniper.net

   Oscar Gonzalez de Dios
   Telefonica

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   Email: oscar.gonzalezdedios@telefonica.com

   Samier Barguil Giraldo
   Nokia
   Email: samier.barguil_giraldo@nokia.com

   Bo Wu
   Huawei Technologies
   Email: lana.wubo@huawei.com

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