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A Common YANG Data Model for Attachment Circuits
draft-ietf-opsawg-teas-common-ac-12

Document Type Active Internet-Draft (opsawg WG)
Authors Mohamed Boucadair , Richard Roberts , Oscar Gonzalez de Dios , Samier Barguil , Bo Wu
Last updated 2024-07-24
Replaces draft-boro-opsawg-teas-common-ac
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication
Document shepherd Reza Rokui
Shepherd write-up Show Last changed 2024-05-15
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draft-ietf-opsawg-teas-common-ac-12
OPSAWG                                                 M. Boucadair, Ed.
Internet-Draft                                                    Orange
Intended status: Standards Track                         R. Roberts, Ed.
Expires: 25 January 2025                                         Juniper
                                                           O. G. D. Dios
                                                              Telefonica
                                                           S. B. Giraldo
                                                                   Nokia
                                                                   B. Wu
                                                     Huawei Technologies
                                                            24 July 2024

            A Common YANG Data Model for Attachment Circuits
                  draft-ietf-opsawg-teas-common-ac-12

Abstract

   The document specifies a common Attachment Circuits (ACs) YANG
   module, which is designed with the intent to be reusable by other
   models.  For example, this common model can be reused by service
   models to expose ACs as a service, service models that require
   binding a service to a set of ACs, network and device models to
   provision ACs, etc.

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.

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on 25 January 2025.

Copyright Notice

   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
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Editorial Note (To be removed by RFC Editor)  . . . . . .   4
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   5
   3.  Relationship to Other AC Data Models  . . . . . . . . . . . .   6
   4.  Description of the AC Common YANG Module  . . . . . . . . . .   7
     4.1.  Features  . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Identities  . . . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  Reusable Groupings  . . . . . . . . . . . . . . . . . . .   8
   5.  Common Attachment Circuit YANG Module . . . . . . . . . . . .  16
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  51
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  52
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  53
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  53
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  55
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  58
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  58
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  59

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1.  Introduction

   Connectivity services are provided by networks to customers via
   dedicated terminating points (e.g., Service Functions (SFs), Customer
   Premises Equipment (CPEs), 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 that belong to the same customer/service, an interconnection
   node, or an ancillary node.  A set of objectives for the connectivity
   service may eventually be negotiated and agreed upon between a
   customer a network provider.  For that data transfer to take place
   within the provider network, it is assumed that adequate setup is
   provisioned over the links that connect customer terminating points
   and a provider network (a Provider Edge (PE), typically) so that data
   can be successfully exchanged over these links.  The required setup
   is referred to in this document as Attachment Circuits (ACs), while
   the underlying link is referred to as "bearer".

   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.  Whether these attachment circuits are
   specific to a given service or be shared to deliver a variety of
   services is deployment-specific.

   An example of attachment circuits is depicted in Figure 1.  A
   Customer Edge (CE) may be a physical node or a logical entity.  A CE
   is seen by the network as a peer Service Attachment Point (SAP)
   [RFC9408].  CEs may be dedicated to one single service (e.g., Layer 3
   Virtual Private Network (VPN) or Layer 2 VPN) or host multiple
   services (e.g., Service Functions [RFC7665]).  A single AC (as seen
   by a network provider) may be bound to one or multiple peer SAPs
   (e.g., "CE1" and "CE2").  For example, and as discussed in [RFC4364],

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   multiple CEs can be attached to a PE over the same attachment
   circuit.  This is typically implemented if the Layer 2 infrastructure
   between the CE and the network provides a multipoint service.  The
   same CE may terminate multiple ACs.  These ACs may be over the same
   or distinct bearers.

                             .--------------------.
      .-------.              |                   .--.  (b1)  .------.
      |       +----.         |                   |  +---AC---+      |
      |  CE1  |    |         |                   |PE+---AC---+  CE3 |
      '-------'    |       .--.                  '--'  (b2)  '------'
                   +---AC--+PE|     Network       |
      .-------.    |       '--'                  .--.  (b3)  .------.
      |       |    |         |                   |  +---AC---+      |
      |  CE2  +----'         |                   |PE+---AC---+  CE4 |
      '-------'              |          .--.     '--'  (b3)  '---+--'
                             '----------+PE|------'              |
                                        '--'                     |
                                         |                       |
                                         '-----------AC----------'
      (bx) = bearer Id x

                         Figure 1: Examples of ACs

   This document specifies a common module ("ietf-ac-common") for
   attachment circuits (Section 5).  The model is designed with the
   intent to be reusable by other models and, therefore, ensure
   consistent AC structures among modules that manipulate ACs.  For
   example, the common model can be reused by service models to expose
   AC-as-a-Service (ACaaS) (e.g.,
   [I-D.ietf-opsawg-teas-attachment-circuit]), service models that
   require binding a service to a set of ACs (e.g., Network Slice
   Service [I-D.ietf-teas-ietf-network-slice-nbi-yang])), network models
   to provision ACs (e.g., [I-D.ietf-opsawg-ntw-attachment-circuit]),
   device models, etc.

   The common AC module eases data inheritance between modules (e.g.,
   from service to network models as per [RFC8969]).

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

1.1.  Editorial Note (To be removed by RFC Editor)

   Note to the RFC Editor: This section is to be removed prior to
   publication.

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   This document contains placeholder values that need to be replaced
   with finalized values at the time of publication.  This note
   summarizes all of the substitutions that are needed.

   Please apply the following replacements:

   *  XXXX --> the assigned RFC number for this I-D

   *  2023-11-13 --> the actual date of the publication of this document

2.  Conventions and Definitions

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

   LxSM refers to both the Layer 2 Service Model (L2SM) [RFC8466] and
   the Layer 3 Service Model (L3SM) [RFC8299].

   LxNM refers to both the Layer 2 Network Model (L2NM) [RFC9291] and
   the Layer 3 Network Model (L3NM) [RFC9182].

   This document uses the following term:

   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 then 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 Virtual Local Area Networks (VLANs) on the
      same bearer that is provided by a physical link).

   The names of data nodes are prefixed using the prefix associated with
   the corresponding imported YANG module as shown in Table 1:

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        +============+==================+========================+
        | Prefix     | Module           | Reference              |
        +============+==================+========================+
        | inet       | ietf-inet-types  | Section 4 of [RFC6991] |
        +------------+------------------+------------------------+
        | key-chain  | ietf-key-chain   | [RFC8177]              |
        +------------+------------------+------------------------+
        | nacm       | ietf-netconf-acm | [RFC8341]              |
        +------------+------------------+------------------------+
        | vpn-common | ietf-vpn-common  | [RFC9181]              |
        +------------+------------------+------------------------+
        | yang       | ietf-yang-types  | Section 3 of [RFC6991] |
        +------------+------------------+------------------------+

              Table 1: Modules and Their Associated Prefixes

3.  Relationship to Other AC Data Models

   Figure 2 depicts the relationship between the various AC data models:

   *  "ietf-ac-common" (Section 5)

   *  "ietf-bearer-svc" (Section 5.1 of
      [I-D.ietf-opsawg-teas-attachment-circuit])

   *  "ietf-ac-svc" (Section 5.2 of
      [I-D.ietf-opsawg-teas-attachment-circuit])

   *  "ietf-ac-ntw" ([I-D.ietf-opsawg-ntw-attachment-circuit])

   *  "ietf-ac-glue" ([I-D.ietf-opsawg-ac-lxsm-lxnm-glue])

                               ietf-ac-common
                                ^     ^     ^
                                |     |     |
                     +----------+     |     +----------+
                     |                |                |
                     |                |                |
               ietf-ac-svc <--> ietf-bearer-svc        |
                  ^    ^                               |
                  |    |                               |
                  |    +------------------------ ietf-ac-ntw
                  |                                    ^
                  |                                    |
                  |                                    |
                  +----------- ietf-ac-glue -----------+

                          Figure 2: AC Data Models

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   "ietf-ac-common" is imported by "ietf-bearer-svc", "ietf-ac-svc", and
   "ietf-ac-ntw".  Bearers managed using "ietf-bearer-svc" may be
   referenced in the service ACs managed using "ietf-ac-svc".
   Similarly, a bearer managed using "ietf-bearer-svc" may list the set
   of ACs that use that bearer.  In order to ease correlation between an
   AC service requests and the actual AC provisioned in the network,
   "ietf-ac-ntw" uses the AC references exposed by "ietf-ac-svc".  To
   bind Layer 2 VPN or Layer 3 VPN services with ACs, "ietf-ac-glue"
   augments the LxSM and LxNM with AC service references exposed by
   "ietf-ac-svc" and AC network references exposed by "ietf-ac-ntw".

4.  Description of the AC Common YANG Module

   The full tree diagram of the module can be generated using the
   "pyang" tool [PYANG] with "-f tree --tree-print-groupings" command-
   line parameters.  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.

      The full tree of the "ietf-ac-common" module is available at
      [AC-Common-Tree].

4.1.  Features

   The module defines the following features:

   'layer2-ac':  Used to indicate support of ACs with Layer 2
      properties.

   'layer3-ac':  Used to indicate support of ACs with Layer 3
      properties.

   'server-assigned-reference':  Used to indicate support of server-
      generated references to access relevant resources.

      For example, a bearer request is first created using a name which
      is assigned by the client, but if this feature is supported, the
      request will also include a server-generated reference.  That
      reference can be used when requesting the creating of an AC over
      the existing bearer.

4.2.  Identities

   The module defines a set of identities, including the following:

   'address-allocation-type':  Used to specify the IP address allocation

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      type in an AC.  For example, this identity can used to indicate
      whether the provider network provides DHCP service, DHCP relay, or
      static addressing.  Note that for the IPv6 case, Stateless Address
      Autoconfiguration (SLAAC) [RFC4862] can be used.

   'local-defined-next-hop':  Used to specify next hop actions.  For
      example, this identity can be used to indicate an action to
      discard traffic for a given destination or treat traffic towards
      addresses within the specified next-hop prefix as though they are
      connected to a local link.

   'l2-tunnel-type':  Uses to control the Layer 2 tunnel selection for
      an AC.  The current version supports indicating pseudowire,
      Virtual Private LAN Service (VPLS), and Virtual eXtensible Local
      Area Network (VXLAN).

   'precedence-type':  Used to indicate the redundancy type when
      requesting ACs.  For example, this identity can be used to tag
      primary and secondary ACs.

   'bgp-capability':  Used to indicate a BGP capability [RFC5492].
      Examples of BGP capabilities are Multiprotocol extensions for
      BGP-4 [RFC4760], route refresh [RFC2918], graceful restart
      [RFC4724], ADD-PATH [RFC7911], or BGP Role [RFC9234]}.

   'role':  Used to indicate the type of an AC: User-to-Network
      Interface (UNI), Network-to-Network Interface (NNI), or public
      NNI.

   New administrative status types:  In addition to the status types
      already defined in [RFC9181], this document defines:

      *  'awaiting-validation' to report that a request is pending an
         adiministrator approval.

      *  'awaiting-processing' to report that a request was approved and
         validated, but is awaiting more processing before activation.

      *  'admin-prohibited' to report that a request cannot be handled
         because of administrative policies.

      *  'rejected' to report that a request was rejected reasons not
         covered by the other status types.

4.3.  Reusable Groupings

   The module also defines a set of reusable groupings, including the
   following:

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   'op-instructions' (Figure 3):  Defines a set of parameters to specify
      scheduling instructions and report related events for a service
      request (e.g., AC or bearer).

     grouping service-status:
       +-- status
          +-- admin-status
          |  +-- status?        identityref
          |  +--ro last-change?   yang:date-and-time
          +--ro oper-status
             +--ro status?        identityref
             +--ro last-change?   yang:date-and-time
     grouping op-instructions:
       +-- requested-start?   yang:date-and-time
       +-- requested-stop?    yang:date-and-time
       +--ro actual-start?      yang:date-and-time
       +--ro actual-stop?       yang:date-and-time

                Figure 3: Operational Instructions Grouping

   Layer 2 encapsulations (Figure 4):  Groupings for the following
      encapsulation schemes are supported: dot1Q, QinQ, and priority-
      tagged.

   Layer 2 tunnel services (Figure 4):  These groupings are used to
      define Layer 2 tunnel services that may be needed for the
      activation of an AC.  Examples of supported Layer 2 services are
      the pseudowire (Section 6.1 of [RFC8077]), VPLS, or VXLAN
      [RFC7348].

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     grouping dot1q:
       +-- tag-type?   identityref
       +-- cvlan-id?   uint16
     grouping priority-tagged:
       +-- tag-type?   identityref
     grouping qinq:
       +-- tag-type?   identityref
       +-- svlan-id?   uint16
       +-- cvlan-id?   uint16
     grouping pseudowire:
       +-- vcid?      uint32
       +-- far-end?   union
     grouping vpls:
       +-- vcid?      uint32
       +-- far-end*   union
     grouping vxlan:
       +-- vni-id?            uint32
       +-- peer-mode?         identityref
       +-- peer-ip-address*   inet:ip-address
     grouping l2-tunnel-service:
       +-- type?         identityref
       +-- pseudowire
       |  +-- vcid?      uint32
       |  +-- far-end?   union
       +-- vpls
       |  +-- vcid?      uint32
       |  +-- far-end*   union
       +-- vxlan
          +-- vni-id?            uint32
          +-- peer-mode?         identityref
          +-- peer-ip-address*   inet:ip-address

                   Figure 4: Layer 2 Connection Groupings

   Layer 3 address allocation (Figure 5):  Defines both IPv4 and IPv6
      groupings to specify IP address allocation over an AC.  Both
      dynamic and static address schemes are supported.

   IP connections (Figure 5)::  Defines IPv4 and IPv6 groupings for
      managing Layer 3 connectivity over an AC.  Both basic and more
      elaborated IP connection groupings are supported.

     grouping ipv4-allocation-type:
       +-- prefix-length?             uint8
       +-- address-allocation-type?   identityref
     grouping ipv6-allocation-type:
       +-- prefix-length?             uint8
       +-- address-allocation-type?   identityref

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

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

                   Figure 5: Layer 3 Connection Groupings

   Routing parameters & OAM (Figure 6):  In addition to static routing,
      the module supports the following routing protocols: BGP
      [RFC4271], OSPF [RFC4577] or [RFC6565], IS-IS
      [ISO10589][RFC1195][RFC5308], and RIP [RFC2453].  For all
      supported routing protocols, '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].  More details about supported routing groupings are
      provided hereafter:

      *  Authentication: These groupings include the required
         information to manage the authentication of OSPF, IS-IS, BGP,
         and RIP.  Similar to [RFC9182], this version of the common AC
         model assumes that parameters specific to the TCP-AO are

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         preconfigured as part of the key chain that is referenced in
         the model.  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]).

      *  BGP peer groups: Includes a set of parameters to identify a BGP
         peer group.  Such a group can be defined by providing a local
         AS Number (ASN), a customer's ASN, and the address families to
         be activated for this group.  BGP peer groups can be identified
         by a name.

      *  Basic parameters: These groupings include the minimal set of
         routing configuration that is required for the activation of
         OSPF, IS-IS, BGP, and RIP.

      *  Static routing: Parameters to configure an entry of a list of
         IP static routing entries.

      The 'redundancy-group' grouping lists the groups to which an AC
      belongs [RFC9181].  For example, the 'group-id' is used to
      associate redundancy or protection constraints of ACs.

    grouping bgp-authentication:
       +-- authentication
          +-- enabled?           boolean
          +-- keying-material
             +-- (option)?
                +--:(ao)
                |  +-- enable-ao?          boolean
                |  +-- ao-keychain?        key-chain:key-chain-ref
                +--:(md5)
                |  +-- md5-keychain?       key-chain:key-chain-ref
                +--:(explicit)
                   +-- key-id?             uint32
                   +-- key?                string
                   +-- crypto-algorithm?   identityref
     grouping ospf-authentication:
       +-- authentication
          +-- enabled?           boolean
          +-- keying-material
             +-- (option)?
                +--:(auth-key-chain)
                |  +-- key-chain?          key-chain:key-chain-ref
                +--:(auth-key-explicit)
                   +-- key-id?             uint32
                   +-- key?                string
                   +-- crypto-algorithm?   identityref

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     grouping isis-authentication:
       +-- authentication
          +-- enabled?           boolean
          +-- keying-material
             +-- (option)?
                +--:(auth-key-chain)
                |  +-- key-chain?          key-chain:key-chain-ref
                +--:(auth-key-explicit)
                   +-- key-id?             uint32
                   +-- key?                string
                   +-- crypto-algorithm?   identityref
     grouping rip-authentication:
       +-- authentication
          +-- enabled?           boolean
          +-- keying-material
             +-- (option)?
                +--:(auth-key-chain)
                |  +-- key-chain?          key-chain:key-chain-ref
                +--:(auth-key-explicit)
                   +-- key?                string
                   +-- crypto-algorithm?   identityref
     grouping bgp-peer-group-without-name:
       +-- local-as?         inet:as-number
       +-- peer-as?          inet:as-number
       +-- address-family?   identityref
       +-- role?             identityref
     grouping bgp-peer-group-with-name:
       +-- name?             string
       +-- local-as?         inet:as-number
       +-- peer-as?          inet:as-number
       +-- address-family?   identityref
       +-- role?             identityref
     grouping ospf-basic:
       +-- address-family?   identityref
       +-- area-id           yang:dotted-quad
       +-- metric?           uint16
     grouping isis-basic:
       +-- address-family?   identityref
       +-- area-address      area-address
     grouping ipv4-static-rtg-entry:
       +-- lan?        inet:ipv4-prefix
       +-- lan-tag?    string
       +-- next-hop?   union
       +-- metric?     uint32
     grouping ipv4-static-rtg:
       +-- ipv4-lan-prefixes* [lan next-hop] {vpn-common:ipv4}?
          +-- lan         inet:ipv4-prefix
          +-- lan-tag?    string

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          +-- next-hop    union
          +-- metric?     uint32
          +-- status
             +-- admin-status
             |  +-- status?        identityref
             |  +--ro last-change?   yang:date-and-time
             +--ro oper-status
                +--ro status?        identityref
                +--ro last-change?   yang:date-and-time
     grouping ipv6-static-rtg-entry:
       +-- lan?        inet:ipv6-prefix
       +-- lan-tag?    string
       +-- next-hop?   union
       +-- metric?     uint32
     grouping ipv6-static-rtg:
       +-- ipv6-lan-prefixes* [lan next-hop] {vpn-common:ipv6}?
          +-- lan         inet:ipv6-prefix
          +-- lan-tag?    string
          +-- next-hop    union
          +-- metric?     uint32
          +-- status
             +-- admin-status
             |  +-- status?        identityref
             |  +--ro last-change?   yang:date-and-time
             +--ro oper-status
                +--ro status?        identityref
                +--ro last-change?   yang:date-and-time
     grouping bfd:
       +-- holdtime?   uint32
     grouping redundancy-group:
       +-- group* [group-id]
          +-- group-id?     string
          +-- precedence?   identityref

                   Figure 6: Layer 3 Connection Groupings

   Bandwidth parameters (Figure 7):  Bandwidth parameters can be
      represented using the Committed Information Rate (CIR), the Excess
      Information Rate (EIR), or the Peak Information Rate (PIR).

      These parameters can be provided per bandwidth type.  Type values
      are taken from [RFC9181], e.g.,:

      *  'bw-per-cos':  The bandwidth is per Class of Service (CoS).

      *  'bw-per-site':  The bandwidth is to all ACs that belong to the
            same site.

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     grouping bandwidth-parameters:
       +-- cir?   uint64
       +-- cbs?   uint64
       +-- eir?   uint64
       +-- ebs?   uint64
       +-- pir?   uint64
       +-- pbs?   uint64
     grouping bandwidth-per-type:
       +-- bandwidth* [bw-type]
          +-- bw-type      identityref
          +-- (type)?
             +--:(per-cos)
             |  +-- cos* [cos-id]
             |     +-- cos-id    uint8
             |     +-- cir?      uint64
             |     +-- cbs?      uint64
             |     +-- eir?      uint64
             |     +-- ebs?      uint64
             |     +-- pir?      uint64
             |     +-- pbs?      uint64
             +--:(other)
                +-- cir?   uint64
                +-- cbs?   uint64
                +-- eir?   uint64
                +-- ebs?   uint64
                +-- pir?   uint64
                +-- pbs?   uint64

                       Figure 7: Bandwidth Groupings

5.  Common Attachment Circuit YANG Module

   This module uses types defined in [RFC6991], [RFC8177], and
   [RFC9181].

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

     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 {

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       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-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types, Section 3";
     }
     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>

        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 common attachment circuit (AC)
        YANG model.

        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

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        (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: A Common YANG Data Model for Attachment Circuits";
     }

     /****************************Features************************/

     feature layer2-ac {
       description
         "Indicates support of Layer 2 ACs.";
     }

     feature layer3-ac {
       description
         "Indicates support of Layer 3 ACs.";
     }

     feature server-assigned-reference {
       description
         "This feature indicates support for server-generated references
          and use of such references to access related resources.";
     }

     /****************************Identities************************/
     // IP address allocation types

     identity address-allocation-type {
       description
         "Base identity for address allocation type in the AC.";
     }

     identity provider-dhcp {
       base address-allocation-type;
       description
         "The provider's network provides a DHCP service to the
          customer.";
     }

     identity provider-dhcp-relay {
       base address-allocation-type;
       description

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         "The provider's network provides a DHCP relay service to the
          customer.";
     }

     identity provider-dhcp-slaac {
       if-feature "vpn-common:ipv6";
       base address-allocation-type;
       description
         "The provider's network provides a DHCP service to the customer
          as well as IPv6 Stateless Address Autoconfiguration (SLAAC).";
       reference
         "RFC 4862: IPv6 Stateless Address Autoconfiguration";
     }

     identity static-address {
       base address-allocation-type;
       description
         "The provider's network provides static IP addressing to the
          customer.";
     }

     identity slaac {
       if-feature "vpn-common:ipv6";
       base address-allocation-type;
       description
         "The provider's network uses IPv6 SLAAC to provide addressing
          to the customer.";
       reference
         "RFC 4862: IPv6 Stateless Address Autoconfiguration";
     }

     identity dynamic-infra {
       base address-allocation-type;
       description
         "The IP address is dynamically allocated by the hosting
          infrastrcture.";
     }

     // next-hop actions

     identity local-defined-next-hop {
       description
         "Base identity of local defined next hops.";
     }

     identity discard {
       base local-defined-next-hop;
       description

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         "Indicates an action to discard traffic for the corresponding
          destination. For example, this can be used to black-hole
          traffic.";
     }

     identity local-link {
       base local-defined-next-hop;
       description
         "Treat traffic towards addresses within the specified next-hop
          prefix as though they are connected to a local link.";
     }

     // Layer 2 tunnel types

     identity l2-tunnel-type {
       description
         "Base identity for Layer 2 tunnel selection for an AC.";
     }

     identity pseudowire {
       base l2-tunnel-type;
       description
         "Pseudowire tunnel termination for the AC.";
     }

     identity vpls {
       base l2-tunnel-type;
       description
         "Virtual Private LAN Service (VPLS) tunnel termination for
          the AC.";
     }

     identity vxlan {
       base l2-tunnel-type;
       description
         "Virtual eXtensible Local Area Network (VXLAN) tunnel
          termination for the AC.";
     }

     // Tagging precedence

     identity precedence-type {
       description
         "Redundancy type. The service can be created with primary and
          secondary tagging.";
     }

     identity primary {

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       base precedence-type;
       description
         "Identifies the main attachment circuit.";
     }

     identity secondary {
       base precedence-type;
       description
         "Identifies the secondary attachment circuit.";
     }

    /* BGP Capability Identities. */

     identity bgp-capability {
       description
         "Base identity for a BGP capability.";
       reference
         "RFC 5492: Capabilities Advertisement with BGP-4";
     }

     identity mp-bgp {
       base bgp-capability;
       description
         "Multi-protocol extensions to BGP.";
       reference
         "RFC 4760: Multiprotocol Extentions for BGP-4";
     }

     identity route-refresh {
       base bgp-capability;
       description
         "Route refresh capability.";
       reference
         "RFC 2918: Route Refresh Capability for BGP-4.";
     }

     identity graceful-restart {
       base bgp-capability;
       description
         "Graceful restart capability.";
       reference
         "RFC 4724: Graceful Restart Mechanism for BGP";
     }

     identity add-paths {
       base bgp-capability;
       description
         "A capability that allows the advertisement of multiple

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          paths for the same address prefix without the new paths
          implicitly replacing any previous ones.";
       reference
         "RFC 7911: Advertisement of Multiple Paths in BGP";
     }

     identity ebgp-role {
       base bgp-capability;
       description
         "A capability that allows the advertisement of the BGP
          role when establising a session.";
       reference
         "RFC 9234: Route Leak Prevention and Detection Using
                    Roles in UPDATE and OPEN Messages, Section 4.1";
     }

     // AC Type

     identity role {
       description
         "Base identity for the network role of an AC.";
     }

     identity uni {
       base role;
         description
           "User-to-Network Interface (UNI).";
     }

     identity nni {
       base role;
       description
         "Network-to-Network Interface (NNI).";
     }

     identity public-nni {
       base role;
       description
         "Public peering.";
     }

     // More Admin status types

     identity awaiting-validation {
       base vpn-common:administrative-status;
       description
         "This administrative status reflects that a request is
          pending an adiministrator approval.";

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     }

     identity awaiting-processing {
       base vpn-common:administrative-status;
       description
         "This administrative status reflects that a request was
          approved and validated, but is awaiting more processing
          before activation.";
     }

     identity admin-prohibited {
       base vpn-common:administrative-status;
       description
         "This administrative status reflects that a request cannot
          be handled because of administrative policies.";
     }

     identity rejected {
       base vpn-common:administrative-status;
       description
         "This administrative status reflects that a request was
          rejected because, e.g., there are no sufficient resources
          or other reasons not covered by the other status types.";
     }

     identity bgp-role {
       description
         "Used to indicate BGP role when establishing a BGP session.";
       reference
         "RFC 9234: Route Leak Prevention and Detection Using
                    Roles in UPDATE and OPEN Messages, Section 4";
     }

     identity provider {
       base bgp-role;
       description
         "The local AS is a transit provider of the remote AS.";
     }

     identity client {
       base bgp-role;
       description
         "The local AS is a transit provider of the remote AS.";
     }

     identity rs {
       base bgp-role;
       description

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         "The local AS is a Route Server (RS).";
     }

     identity rs-client {
       base bgp-role;
       description
         "The local AS is a client of an RS and the RS is the
          remote AS.";
     }

     identity peer {
       base bgp-role;
       description
         "The local and remote ASes have a peering relationship.";
     }

     /****************************Typedefs************************/

     typedef predefined-next-hop {
       type identityref {
         base local-defined-next-hop;
       }
       description
         "Predefined next-hop designation for locally generated
          routes.";
     }

     typedef area-address {
       type string {
         pattern '[0-9A-Fa-f]{2}(\.[0-9A-Fa-f]{4}){0,6}';
       }
       description
         "This type defines the area address format.";
     }

     /************************Reusable groupings********************/
     /**** Service Status ****/

     grouping service-status {
       description
         "Service status grouping.";
       container status {
         description
           "Service status.";
         container admin-status {
           description
             "Administrative service status.";
           leaf status {

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             type identityref {
               base vpn-common:administrative-status;
             }
             description
               "Administrative service status.";
           }
           leaf last-change {
             type yang:date-and-time;
             config false;
             description
               "Indicates the actual date and time of the service
                status change.";
           }
         }
         container oper-status {
           config false;
           description
             "Operational service status.";
           uses vpn-common:oper-status-timestamp;
         }
       }
     }

     /**** A set of profiles ****/

     grouping ac-profile-cfg {
       description
         "Grouping for AC profile configuration.";
       container valid-provider-identifiers {
         description
           "Container for valid provider profile identifiers.
            The profiles only have significance within the service
            provider's administrative domain.";
         list encryption-profile-identifier {
           key "id";
           description
             "List of encryption profile identifiers.";
           leaf id {
             type string;
             description
               "Identification of the encryption profile to be used.";
           }
         }
         list qos-profile-identifier {
           key "id";
           description
             "List of QoS profile identifiers.";

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           leaf id {
             type string;
             description
               "Identification of the QoS profile to be used.";
           }
         }
         list failure-detection-profile-identifier {
           key "id";
           description
             "List of BFD profile identifiers.";
           leaf id {
             type string;
             description
               "Identification of the a failure detection (e.g., BFD)
                profile to be used.";
           }
         }
         list forwarding-profile-identifier {
           key "id";
           description
             "List of forwarding profile identifiers.";
           leaf id {
             type string;
             description
               "Identification of the forwarding profile to be used.";
           }
         }
         list routing-profile-identifier {
           key "id";
           description
             "List of routing profile identifiers.";
           leaf id {
             type string;
             description
               "Identification of the routing profile to be used by
                the routing protocols over an AC.";
           }
         }
         nacm:default-deny-write;
       }
     }

     /**** Operational instructions ****/

     grouping op-instructions {
       description
         "Scheduling instructions.";
       leaf requested-start {

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         type yang:date-and-time;
         description
           "Indicates the requested date and time when the service is
            expected to be active.";
       }
       leaf requested-stop {
         type yang:date-and-time;
         description
           "Indicates the requested date and time when the service is
            expected to be disabled.";
       }
       leaf actual-start {
         type yang:date-and-time;
         config false;
         description
           "Indicates the actual date and time when the service
            actually was enabled.";
       }
       leaf actual-stop {
         type yang:date-and-time;
         config false;
         description
           "Indicates the actual date and time when the service
            actually was disabled.";
       }
     }

     /**** Layer 2 encapsulations ****/
     // Dot1q

     grouping dot1q {
       description
         "Defines a grouping for tagged interfaces.";
       leaf tag-type {
         type identityref {
           base vpn-common:tag-type;
         }
         description
           "Tag type.";
       }
       leaf cvlan-id {
         type uint16 {
           range "1..4094";
         }
         description
           "VLAN identifier.";
       }
     }

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     // priority-tagged

     grouping priority-tagged {
       description
         "Priority tagged.";
       leaf tag-type {
         type identityref {
           base vpn-common:tag-type;
         }
         description
           "Tag type.";
       }
     }

     // QinQ

     grouping qinq {
       description
         "Includes QinQ parameters.";
       leaf tag-type {
         type identityref {
           base vpn-common:tag-type;
         }
         description
           "Tag type.";
       }
       leaf svlan-id {
         type uint16 {
           range "1..4094";
         }
         description
           "Service VLAN (S-VLAN) identifier.";
       }
       leaf cvlan-id {
         type uint16 {
           range "1..4094";
         }
         description
           "Customer VLAN (C-VLAN) identifier.";
       }
     }

     /**** Layer 2 tunnel services ****/
     // pseudowire (PW)

     grouping pseudowire {
       description
         "Includes pseudowire termination parameters.";

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       leaf vcid {
         type uint32;
         description
           "Indicates a PW or virtual circuit (VC) identifier.";
       }
       leaf far-end {
         type union {
           type uint32;
           type inet:ip-address;
         }
         description
           "Neighbor reference.";
         reference
           "RFC 8077: Pseudowire Setup and Maintenance Using the Label
                      Distribution Protocol (LDP), Section 6.1";
       }
     }

     // VPLS

     grouping vpls {
       description
         "VPLS termination parameters.";
       leaf vcid {
         type uint32;
         description
           "VC identifier.";
       }
       leaf-list far-end {
         type union {
           type uint32;
           type inet:ip-address;
         }
         description
           "Neighbor reference.";
       }
     }

     // VXLAN

     grouping vxlan {
       description
         "VXLAN termination parameters.";
       leaf vni-id {
         type uint32;
         description
           "VXLAN Network Identifier (VNI).";
       }

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       leaf peer-mode {
         type identityref {
           base vpn-common:vxlan-peer-mode;
         }
         description
           "Specifies the VXLAN access mode. By default,
            the peer mode is set to 'static-mode'.";
       }
       leaf-list peer-ip-address {
         type inet:ip-address;
         description
           "List of a peer's IP addresses.";
       }
     }

     // Layer 2 Tunnel service

     grouping l2-tunnel-service {
       description
         "Defines a Layer 2 tunnel termination.";
       leaf type {
         type identityref {
           base l2-tunnel-type;
         }
         description
           "Selects the tunnel termination type for an AC.";
       }
       container pseudowire {
         when "derived-from-or-self(../type, 'ac-common:pseudowire')" {
           description
             "Only applies when the Layer 2 service type is
              'pseudowire'.";
         }
         description
           "Includes pseudowire termination parameters.";
         uses pseudowire;
       }
       container vpls {
         when "derived-from-or-self(../type, 'ac-common:vpls')" {
           description
             "Only applies when the Layer 2 service type is 'vpls'.";
         }
         description
           "VPLS termination parameters.";
         uses vpls;
       }
       container vxlan {
         when "derived-from-or-self(../type, 'ac-common:vxlan')" {

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           description
             "Only applies when the Layer 2 service type is 'vxlan'.";
         }
         description
           "VXLAN termination parameters.";
         uses vxlan;
       }
     }

     /**** Layer 3 connection *****/
     // IPv4 allocation type

     grouping ipv4-allocation-type {
       description
         "IPv4-specific parameters.";
       leaf prefix-length {
         type uint8 {
           range "0..32";
         }
         description
           "Subnet prefix length expressed in bits. It is applied to
            both local and customer addresses.";
       }
       leaf address-allocation-type {
         type identityref {
           base address-allocation-type;
         }
         must "not(derived-from-or-self(current(), 'ac-common:slaac') "
            + "or derived-from-or-self(current(), "
            + "'ac-common:provider-dhcp-slaac'))" {
           error-message "SLAAC is only applicable to IPv6.";
         }
         description
           "Defines how IPv4 addresses are allocated to the peer site.";
       }
     }

     // IPv6 allocation type

     grouping ipv6-allocation-type {
       description
         "IPv6-specific parameters.";
       leaf prefix-length {
         type uint8 {
           range "0..128";
         }
         description
           "Subnet prefix length expressed in bits. It is applied to

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             both local and customer addresses.";
       }
       leaf address-allocation-type {
         type identityref {
           base address-allocation-type;
         }
         description
           "Defines how IPv6 addresses are allocated to the peer site.";
       }
     }

     // Basic parameters for IPv4 connection

     grouping ipv4-connection-basic {
       description
         "Basic set fof IPv4-specific parameters for the connection.";
       uses ipv4-allocation-type;
       choice allocation-type {
         description
           "Choice of the IPv4 address allocation.";
         case dynamic {
           description
             "When the addresses are allocated by DHCP or other dynamic
              means local to the infrastructure.";
           choice provider-dhcp {
             description
               "Parameters related to DHCP-allocated addresses. IP
                addresses are allocated by DHCP, that is provided by
                the operator.";
             leaf dhcp-service-type {
               type enumeration {
                 enum server {
                   description
                     "Local DHCP server.";
                 }
                 enum relay {
                   description
                     "Local DHCP relay.  DHCP requests are relayed to
                      a provider's server.";
                 }
               }
               description
                 "Indicates the type of DHCP service to be enabled on
                  an AC.";
             }
           }
           choice dhcp-relay {
             description

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               "The DHCP relay is provided by the operator.";
             container customer-dhcp-servers {
               description
                 "Container for a list of the customer's DHCP servers.";
               leaf-list server-ip-address {
                 type inet:ipv4-address;
                 description
                   "IPv4 addresses of the customer's DHCP server.";
               }
             }
           }
         }
       }
     }

     // Basic parameters for IPv6 connection

     grouping ipv6-connection-basic {
       description
         "Basic set fof IPv6-specific parameters for the connection.";
       uses ipv6-allocation-type;
       choice allocation-type {
         description
           "Choice of the IPv6 address allocation.";
         case dynamic {
           description
             "When the addresses are allocated by DHCP or other dynamic
              means local to the infrastructure.";
           choice provider-dhcp {
             description
               "Parameters related to DHCP-allocated addresses.
                IP addresses are allocated by DHCP, that is provided
                by the operator.";
             leaf dhcp-service-type {
               type enumeration {
                 enum server {
                   description
                     "Local DHCP server.";
                 }
                 enum relay {
                   description
                     "Local DHCP relay.  DHCP requests are relayed to a
                      provider's server.";
                 }
               }
               description
                 "Indicates the type of DHCP service to be enabled on
                  the AC.";

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             }
           }
           choice dhcp-relay {
             description
               "The DHCP relay is provided by the operator.";
             container customer-dhcp-servers {
               description
                 "Container for a list of the customer's DHCP servers.";
               leaf-list server-ip-address {
                 type inet:ipv6-address;
                 description
                   "IPv6 addresses of the customer's DHCP server.";
               }
             }
           }
         }
       }
     }

     // Full parameters for the IPv4 connection

     grouping ipv4-connection {
       description
         "IPv4-specific parameters.";
       leaf local-address {
         type inet:ipv4-address;
         description
           "The IP address used at the provider's interface.";
       }
       leaf virtual-address {
         type inet:ipv4-address;
         description
           "This addresss may be used for redundancy purposes.";
       }
       uses ipv4-allocation-type;
       choice allocation-type {
         description
           "Choice of the IPv4 address allocation.";
         case dynamic {
           description
             "When the addresses are allocated by DHCP or other
              dynamic means local to the infrastructure.";
           choice address-assign {
             description
               "A choice for how IPv4 addresses are assigned.";
             case number {
               leaf number-of-dynamic-address {
                 type uint16;

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                 description
                   "Specifies the number of IP addresses to be assigned
                    to the customer on the AC.";
               }
             }
             case explicit {
               container customer-addresses {
                 description
                   "Container for customer addresses to be allocated
                    using DHCP.";
                 list address-pool {
                   key "pool-id";
                   description
                     "Describes IP addresses to be dyncamically
                      allocated.

                      When only 'start-address' is present, it
                      represents a single address.

                      When both 'start-address' and 'end-address' are
                      specified, it implies a range inclusive of both
                      addresses.";
                   leaf pool-id {
                     type string;
                     description
                       "A pool identifier for the address range from
                        'start-address' to 'end-address'.";
                   }
                   leaf start-address {
                     type inet:ipv4-address;
                     mandatory true;
                     description
                       "Indicates the first address in the pool.";
                   }
                   leaf end-address {
                     type inet:ipv4-address;
                     description
                       "Indicates the last address in the pool.";
                   }
                 }
               }
             }
           }
           choice provider-dhcp {
             description
               "Parameters related to DHCP-allocated addresses. IP
                addresses are allocated by DHCP, which is provided by
                the operator.";

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             leaf dhcp-service-type {
               type enumeration {
                 enum server {
                   description
                     "Local DHCP server.";
                 }
                 enum relay {
                   description
                     "Local DHCP relay.  DHCP requests are relayed to
                      a provider's server.";
                 }
               }
               description
                 "Indicates the type of DHCP service to be enabled on
                  this AC.";
             }
           }
           choice dhcp-relay {
             description
               "The DHCP relay is provided by the operator.";
             container customer-dhcp-servers {
               description
                 "Container for a list of the customer's DHCP servers.";
               leaf-list server-ip-address {
                 type inet:ipv4-address;
                 description
                   "IPv4 addresses of the customer's DHCP server.";
               }
             }
           }
         }
         case static-addresses {
           description
             "Lists the IPv4 addresses that are used.";
           list address {
             key "address-id";
             ordered-by user;
             description
               "Lists the IPv4 addresses that are used. The first
                address of the list is the primary address of the
                connection.";
             leaf address-id {
               type string;
               description
                 "An identifier of the static IPv4 address.";
             }
             leaf customer-address {
               type inet:ipv4-address;

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               description
                 "An IPv4 address of the customer side.";
             }
           }
         }
       }
     }

     // Full parameters for the IPv6 connection

     grouping ipv6-connection {
       description
         "IPv6-specific parameters.";
       leaf local-address {
         type inet:ipv6-address;
         description
           "IPv6 address of the provider side.";
       }
       leaf virtual-address {
         type inet:ipv6-address;
         description
           "This addresss may be used for redundancy purposes.";
       }
       uses ipv6-allocation-type;
       choice allocation-type {
         description
           "Choice of the IPv6 address allocation.";
         case dynamic {
           description
             "When the addresses are allocated by DHCP or other
              dynamic means local to the infrastructure.";
           choice address-assign {
             description
               "A choice for how IPv6 addresses are assigned.";
             case number {
               leaf number-of-dynamic-address {
                 type uint16;
                 description
                   "Specifies the number of IP addresses to be
                    assigned to the customer on this access.";
               }
             }
             case explicit {
               container customer-addresses {
                 description
                   "Container for customer addresses to be allocated
                    using DHCP.";
                 list address-pool {

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                   key "pool-id";
                   description
                     "Describes IP addresses to be dyncamically
                      allocated.

                      When only 'start-address' is present, it
                      represents a single address.

                      When both 'start-address' and 'end-address' are
                      specified, it implies a range inclusive of both
                      addresses.";
                   leaf pool-id {
                     type string;
                     description
                       "A pool identifier for the address range from
                        'start-address' to 'end-address'.";
                   }
                   leaf start-address {
                     type inet:ipv6-address;
                     mandatory true;
                     description
                       "Indicates the first address in the pool.";
                   }
                   leaf end-address {
                     type inet:ipv6-address;
                     description
                       "Indicates the last address in the pool.";
                   }
                 }
               }
             }
           }
           choice provider-dhcp {
             description
               "Parameters related to DHCP-allocated addresses.
                IP addresses are allocated by DHCP, which is provided
                by the operator.";
             leaf dhcp-service-type {
               type enumeration {
                 enum server {
                   description
                     "Local DHCP server.";
                 }
                 enum relay {
                   description
                     "Local DHCP relay.  DHCP requests are relayed
                      to a provider's server.";
                 }

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               }
               description
                 "Indicates the type of DHCP service to
                  be enabled on this access.";
             }
           }
           choice dhcp-relay {
             description
               "The DHCP relay is provided by the operator.";
             container customer-dhcp-servers {
               description
                 "Container for a list of the customer's DHCP servers.";
               leaf-list server-ip-address {
                 type inet:ipv6-address;
                 description
                   "IPv6 addresses of the customer's DHCP server.";
               }
             }
           }
         }
         case static-addresses {
           description
             "Lists the IPv6 addresses that are used.";
           list address {
             key "address-id";
             ordered-by user;
             description
               "Lists the IPv6 addresses that are used. The first
                address of the list is the primary IP address of
                the connection.";
             leaf address-id {
               type string;
               description
                 "An identifier of the static IPv6 address.";
             }
             leaf customer-address {
               type inet:ipv6-address;
               description
                 "An IPv6 address of the customer side.";
             }
           }
         }
       }
     }

     /**** Routing ****/
     // Routing authentication

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     grouping bgp-authentication {
       description
         "Grouping for BGP authentication parameters.";
       container authentication {
         description
           "Container for BGP authentication  parameters.";
         leaf enabled {
           type boolean;
           description
             "Enables or disables authentication.";
         }
         container keying-material {
           when "../enabled = 'true'";
           description
             "Container for describing how a BGP routing session is to
              be secured on an AC.";
           choice option {
             description
               "Choice of authentication options.";
             case ao {
               description
                 "Uses the TCP Authentication Option (TCP-AO).";
               reference
                 "RFC 5925: The TCP Authentication Option";
               leaf enable-ao {
                 type boolean;
                 description
                   "Enables the TCP-AO.";
               }
               leaf ao-keychain {
                 type key-chain:key-chain-ref;
                 description
                   "Reference to the TCP-AO key chain.";
                 reference
                   "RFC 8177: YANG Data Model for Key Chains";
               }
             }
             case md5 {
               description
                 "Uses MD5 to secure the session.";
               reference
                 "RFC 4364: BGP/MPLS IP Virtual Private Networks
                            (VPNs), Section 13.2";
               leaf md5-keychain {
                 type key-chain:key-chain-ref;
                 description
                   "Reference to the MD5 key chain.";
                 reference

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                   "RFC 8177: YANG Data Model for Key Chains";
               }
             }
             case explicit {
               leaf key-id {
                 type uint32;
                 description
                   "Key identifier.";
               }
               leaf key {
                 type string;
                 description
                   "BGP authentication key.

                    This model only supports the subset of keys that
                    are representable as ASCII strings.";
               }
               leaf crypto-algorithm {
                 type identityref {
                   base key-chain:crypto-algorithm;
                 }
                 description
                   "Indicates the cryptographic algorithm associated
                    with the key.";
               }
             }
           }
         }
       }
     }

     grouping ospf-authentication {
       description
         "Authentication configuration.";
       container authentication {
         description
           "Container for OSPF authentication  parameters.";
         leaf enabled {
           type boolean;
           description
             "Enables or disables authentication.";
         }
         container keying-material {
           when "../enabled = 'true'";
           description
             "Container for describing how an OSPF session is to be
              secured for this AC.";
           choice option {

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             description
               "Options for OSPF authentication.";
             case auth-key-chain {
               leaf key-chain {
                 type key-chain:key-chain-ref;
                 description
                   "Name of the key chain.";
               }
             }
             case auth-key-explicit {
               leaf key-id {
                 type uint32;
                 description
                   "Key identifier.";
               }
               leaf key {
                 type string;
                 description
                   "OSPF authentication key.

                    This model only supports the subset of keys that
                    are representable as ASCII strings.";
               }
               leaf crypto-algorithm {
                 type identityref {
                   base key-chain:crypto-algorithm;
                 }
                 description
                   "Indicates the cryptographic algorithm associated
                    with the key.";
               }
             }
           }
         }
       }
     }

     grouping isis-authentication {
       description
         "IS-IS authentication configuration.";
       container authentication {
         description
           "Container for IS-IS authentication  parameters.";
         leaf enabled {
           type boolean;
           description
             "Enables or disables authentication.";
         }

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         container keying-material {
           when "../enabled = 'true'";
           description
             "Container for describing how an IS-IS session is secured
              over an AC.";
           choice option {
             description
               "Options for IS-IS authentication.";
             case auth-key-chain {
               leaf key-chain {
                 type key-chain:key-chain-ref;
                 description
                   "Name of the key chain.";
               }
             }
             case auth-key-explicit {
               leaf key-id {
                 type uint32;
                 description
                   "Key identifier.";
               }
               leaf key {
                 type string;
                 description
                   "IS-IS authentication key.

                    This model only supports the subset of keys that
                    are representable as ASCII strings.";
               }
               leaf crypto-algorithm {
                 type identityref {
                   base key-chain:crypto-algorithm;
                 }
                 description
                   "Indicates the cryptographic algorithm associated
                    with the key.";
               }
             }
           }
         }
       }
     }

     grouping rip-authentication {
       description
         "RIP authentication configuration.";
       container authentication {
         description

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           "Container for RIP authentication  parameters.";
         leaf enabled {
           type boolean;
           description
             "Enables or disables authentication.";
         }
         container keying-material {
           when "../enabled = 'true'";
           description
             "Container for describing how a RIP session is to be
              secured on this AC.";
           choice option {
             description
               "Specifies the authentication
                scheme.";
             case auth-key-chain {
               leaf key-chain {
                 type key-chain:key-chain-ref;
                 description
                   "Name of the key chain.";
               }
             }
             case auth-key-explicit {
               leaf key {
                 type string;
                 description
                   "RIP authentication key.

                    This model only supports the subset of keys that
                    are representable as ASCII strings.";
               }
               leaf crypto-algorithm {
                 type identityref {
                   base key-chain:crypto-algorithm;
                 }
                 description
                   "Indicates the cryptographic algorithm associated
                    with the key.";
               }
             }
           }
         }
       }
     }

     // Basic routing parameters

     grouping bgp-peer-group-without-name {

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       description
         "Identifies a BGP peer-group configured on the local system.";
       leaf local-as {
         type inet:as-number;
         description
           "Indicates a local AS Number (ASN). This ASN is exposed
            to a customer so that it knows which ASN to use
            to set up a BGP session.";
       }
       leaf peer-as {
         type inet:as-number;
         description
           "Indicates the customer's ASN when the customer
            requests BGP routing.";
       }
       leaf address-family {
         type identityref {
           base vpn-common:address-family;
         }
         description
           "This node contains the address families to be activated.
            'dual-stack' means that both IPv4 and IPv6 will be
            activated.";
       }
       leaf role {
         type identityref {
           base ac-common:bgp-role;
         }
         description
           "Specifies the BGP role (provider, customer, peer, etc.).";
         reference
           "RFC 9234: Route Leak Prevention and Detection Using
                      Roles in UPDATE and OPEN Messages, Section 4";
       }
     }

     grouping bgp-peer-group-with-name {
       description
         "Identifies a BGP peer-group configured on the local system -
          identified by a peer-group name.";
       leaf name {
         type string;
         description
           "Name of the BGP peer-group.";
       }
       uses bgp-peer-group-without-name;
     }

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     grouping ospf-basic {
       description
         "Configuration specific to OSPF.";
       leaf address-family {
         type identityref {
           base vpn-common:address-family;
         }
         description
           "Indicates whether IPv4, IPv6, or both are to be activated.";
       }
       leaf area-id {
         type yang:dotted-quad;
         mandatory true;
         description
           "Area ID.";
         reference
           "RFC 4577: OSPF as the Provider/Customer Edge Protocol
                      for BGP/MPLS IP Virtual Private Networks
                      (VPNs), Section 4.2.3
            RFC 6565: OSPFv3 as a Provider Edge to Customer Edge
                      (PE-CE) Routing Protocol, Section 4.2";
       }
       leaf metric {
         type uint16;
         description
           "Metric of the AC.  It is used in the routing state
            calculation and path selection.";
       }
     }

     grouping isis-basic {
       description
         "Basic configuration specific to IS-IS.";
       leaf address-family {
         type identityref {
           base vpn-common:address-family;
         }
         description
           "Indicates whether IPv4, IPv6, or both are to be activated.";
       }
       leaf area-address {
         type area-address;
         mandatory true;
         description
           "Area address.";
       }
     }

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     // Static routing

     grouping ipv4-static-rtg-entry {
       description
         "Paramters to configure a specific IPv4 static routing entry.";
       leaf lan {
         type inet:ipv4-prefix;
         description
           "LAN prefix.";
       }
       leaf lan-tag {
         type string;
         description
           "Internal tag to be used in service policies.";
       }
       leaf next-hop {
         type union {
           type inet:ip-address;
           type predefined-next-hop;
         }
         description
           "The next hop that is to be used for the static route.
            This may be specified as an IP address or a
            predefined next-hop type (e.g., 'discard' or
            'local-link').";
       }
       leaf metric {
         type uint32;
         description
           "Indicates the metric associated with the static route.";
       }
     }

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

     grouping ipv6-static-rtg-entry {
       description

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         "Paramters to configure a specific IPv6 static routing entry.";
       leaf lan {
         type inet:ipv6-prefix;
         description
           "LAN prefixes.";
       }
       leaf lan-tag {
         type string;
         description
           "Internal tag to be used in service (e.g., VPN) policies.";
       }
       leaf next-hop {
         type union {
           type inet:ip-address;
           type predefined-next-hop;
         }
         description
           "The next hop that is to be used for the static route.
            This may be specified as an IP address or a predefined
            next-hop type (e.g., 'discard' or 'local-link').";
       }
       leaf metric {
         type uint32;
         description
           "Indicates the metric associated with the static route.";
       }
     }

     grouping ipv6-static-rtg {
       description
         "Configuration specific to IPv6 static routing.";
       list ipv6-lan-prefixes {
         if-feature "vpn-common:ipv6";
         key "lan next-hop";
         description
           "List of LAN prefixes for the site.";
         uses ipv6-static-rtg-entry;
         uses ac-common:service-status;
       }
     }

     // OAM

     grouping bfd {
       description
         "A grouping for basic BFD.";
       leaf holdtime {
         type uint32;

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         units "milliseconds";
         description
           "Expected BFD holdtime.
            The customer may impose some fixed values
            for the holdtime period if the provider allows
            the customer to use this function.
            If the provider doesn't allow the customer to
            use this function, fixed values will not be set.";
         reference
           "RFC 5880: Bidirectional Forwarding Detection (BFD),
                      Section 6.8.18";
       }
     }

     // redundancy

     grouping redundancy-group {
       description
         "A grouping for redundancy group.";
       list group {
          key "group-id";
          description
            "List of group-ids.";
          leaf group-id {
            type string;
            description
              "Indicates the group-id to which the AC belongs.";
          }
          leaf precedence {
            type identityref {
              base ac-common:precedence-type;
            }
            description
              "Defines redundancy of an AC.";
          }
        }
      }

     // QoS

     grouping bandwidth-parameters {
       description
         "A grouping for bandwidth parameters.";
       leaf cir {
         type uint64;
         units "bps";
         description
           "Committed Information Rate (CIR). The maximum number of bits

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            that a port can receive or send during one second over
            an interface.";
       }
       leaf cbs {
         type uint64;
         units "bytes";
         description
           "Committed Burst Size (CBS). CBS controls the bursty nature
            of the traffic.  Traffic that does not use the configured
            CIR accumulates credits until the credits reach the
            configured CBS.";
       }
       leaf eir {
         type uint64;
         units "bps";
         description
           "Excess Information Rate (EIR), i.e., excess frame delivery
            allowed not subject to a Service Level Agreement (SLA).
            The traffic rate can be limited by EIR.";
       }
       leaf ebs {
         type uint64;
         units "bytes";
         description
           "Excess Burst Size (EBS).  The bandwidth available for burst
            traffic from the EBS is subject to the amount of bandwidth
            that is accumulated during periods when traffic allocated
            by the EIR policy is not used.";
       }
       leaf pir {
         type uint64;
         units "bps";
         description
           "Peak Information Rate (PIR), i.e., maximum frame delivery
            allowed. It is equal to or less than sum of CIR and EIR.";
       }
       leaf pbs {
         type uint64;
         units "bytes";
         description
           "Peak Burst Size (PBS).";
       }
     }

     grouping bandwidth-per-type {
       description
         "Grouping for bandwidth per type.";
       list bandwidth {

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         key "bw-type";
         description
           "List for bandwidth per type data nodes.";
         leaf bw-type {
           type identityref {
             base vpn-common:bw-type;
           }
           description
             "Indicates the bandwidth type.";
         }
         choice type {
           description
             "Choice based upon bandwidth type.";
           case per-cos {
             description
               "Bandwidth per CoS.";
             list cos {
               key "cos-id";
               description
                 "List of Class of Services.";
               leaf cos-id {
                 type uint8;
                 description
                   "Identifier of the CoS, indicated by a Differentiated
                    Services Code Point (DSCP) or a CE-CLAN CoS (802.1p)
                    value in the service frame.";
                 reference
                   "IEEE Std 802.1Q: Bridges and Bridged Networks";
               }
               uses bandwidth-parameters;
             }
           }
           case other {
             description
               "Other bandwidth types.";
             uses bandwidth-parameters;
           }
         }
       }
     }
   }
   <CODE ENDS>

6.  Security Considerations

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

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   The YANG module specified in this document defines 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.

   The "ietf-ac-common" module defines a set of identities, types, and
   groupings.  These nodes are intended to be reused by other YANG
   modules.  The module by itself does not expose any data nodes that
   are writable, data nodes that contain read-only state, or RPCs.

   YANG modules that use the groupings that are defined in this document
   should identify the corresponding security considerations.  For
   example, reusing some of these groupings will expose privacy-related
   information (e.g., 'ipv6-lan-prefixes' or 'ipv4-lan-prefixes').
   Disclosing such information may be considered a violation of the
   customer-provider trust relationship.

   Several groupings ('bgp-authentication', 'ospf-authentication',
   'isis-authentication', and 'rip-authentication') rely upon [RFC8177]
   for authentication purposes.  As such, modules that will reuse these
   groupings will inherit the security considerations discussed in
   Section 5 of [RFC8177].  Also, these groupings 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 common AC model, because it is not
   supported by the underlying device modules (e.g., [RFC8695]).

7.  IANA Considerations

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

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

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

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

8.  References

8.1.  Normative References

   [ISO10589] ISO, "Information technology - Telecommunications and
              information exchange between systems - Intermediate System
              to Intermediate System intra-domain routeing information
              exchange protocol for use in conjunction with the protocol
              for providing the connectionless-mode network service
              (ISO8473)", 2002,
              <https://www.iso.org/standard/30932.html>.

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, DOI 10.17487/RFC1195,
              December 1990, <https://www.rfc-editor.org/rfc/rfc1195>.

   [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>.

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

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/rfc/rfc4271>.

   [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>.

   [RFC5308]  Hopps, C., "Routing IPv6 with IS-IS", RFC 5308,
              DOI 10.17487/RFC5308, October 2008,
              <https://www.rfc-editor.org/rfc/rfc5308>.

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   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <https://www.rfc-editor.org/rfc/rfc5492>.

   [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>.

   [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>.

   [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>.

   [RFC7348]  Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
              L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
              eXtensible Local Area Network (VXLAN): A Framework for
              Overlaying Virtualized Layer 2 Networks over Layer 3
              Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
              <https://www.rfc-editor.org/rfc/rfc7348>.

   [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>.

   [RFC8077]  Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and
              Maintenance Using the Label Distribution Protocol (LDP)",
              STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017,
              <https://www.rfc-editor.org/rfc/rfc8077>.

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   [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>.

   [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>.

8.2.  Informative References

   [AC-Common-Tree]
              "Full Common Attachment Circuit Tree Structure", 2023,
              <https://github.com/boucadair/attachment-circuit-
              model/blob/main/yang/full-trees/ac-common-with-
              groupings.txt>.

   [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-14, 5 July 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              rfc8407bis-14>.

   [I-D.ietf-opsawg-ac-lxsm-lxnm-glue]
              Boucadair, M., Roberts, R., Barguil, S., and O. G. de
              Dios, "A YANG Data Model for Augmenting VPN Service and
              Network Models with Attachment Circuits", Work in
              Progress, Internet-Draft, draft-ietf-opsawg-ac-lxsm-lxnm-
              glue-10, 10 June 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ac-lxsm-lxnm-glue-10>.

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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-11, 15 May 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ntw-attachment-circuit-11>.

   [I-D.ietf-opsawg-teas-attachment-circuit]
              Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
              and B. Wu, "YANG Data Models for Bearers and 'Attachment
              Circuits'-as-a-Service (ACaaS)", Work in Progress,
              Internet-Draft, draft-ietf-opsawg-teas-attachment-circuit-
              13, 29 May 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-opsawg-teas-attachment-circuit-13>.

   [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 9543 Network Slice
              Service", Work in Progress, Internet-Draft, draft-ietf-
              teas-ietf-network-slice-nbi-yang-13, 9 May 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              ietf-network-slice-nbi-yang-13>.

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

   [RFC2918]  Chen, E., "Route Refresh Capability for BGP-4", RFC 2918,
              DOI 10.17487/RFC2918, September 2000,
              <https://www.rfc-editor.org/rfc/rfc2918>.

   [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>.

   [RFC4724]  Sangli, S., Chen, E., Fernando, R., Scudder, J., and Y.
              Rekhter, "Graceful Restart Mechanism for BGP", RFC 4724,
              DOI 10.17487/RFC4724, January 2007,
              <https://www.rfc-editor.org/rfc/rfc4724>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/rfc/rfc4760>.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862,
              DOI 10.17487/RFC4862, September 2007,
              <https://www.rfc-editor.org/rfc/rfc4862>.

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   [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>.

   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <https://www.rfc-editor.org/rfc/rfc7911>.

   [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>.

   [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>.

   [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>.

   [RFC9234]  Azimov, A., Bogomazov, E., Bush, R., Patel, K., and K.
              Sriram, "Route Leak Prevention and Detection Using Roles
              in UPDATE and OPEN Messages", RFC 9234,
              DOI 10.17487/RFC9234, May 2022,
              <https://www.rfc-editor.org/rfc/rfc9234>.

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   [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>.

Acknowledgments

   The document reuses many of the structures that were defined in
   [RFC9181] and [RFC9182].

   Thanks to Ebben Aries for the YANG Doctors review, Andy Smith and
   Gyanh Mishra for the rtg-dir reviews.

   Thanks to Reza Rokui for the Shepherd review.

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

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Authors' Addresses

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

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

   Oscar Gonzalez de Dios
   Telefonica
   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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