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A YANG Data Model for Augmenting VPN Service and Network Models with Attachment Circuits
draft-ietf-opsawg-ac-lxsm-lxnm-glue-02

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 9836.
Authors Mohamed Boucadair , Richard Roberts , Samier Barguil , Oscar Gonzalez de Dios
Last updated 2023-11-28 (Latest revision 2023-11-27)
Replaces draft-boro-opsawg-ac-lxsm-lxnm-glue
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draft-ietf-opsawg-ac-lxsm-lxnm-glue-02
OPSAWG                                                 M. Boucadair, Ed.
Internet-Draft                                                    Orange
Intended status: Standards Track                              R. Roberts
Expires: 31 May 2024                                             Juniper
                                                           S. B. Giraldo
                                                                   Nokia
                                                           O. G. D. Dios
                                                              Telefonica
                                                        28 November 2023

  A YANG Data Model for Augmenting VPN Service and Network Models with
                          Attachment Circuits
                 draft-ietf-opsawg-ac-lxsm-lxnm-glue-02

Abstract

   The document specifies a module that updates existing service and
   network VPN modules with the required information to bind specific
   services to ACs that are created using the Attachment Circuit (AC)
   service and network models.

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/.

   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."

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   This Internet-Draft will expire on 31 May 2024.

Copyright Notice

   Copyright (c) 2023 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Sample Uses of the Data Models  . . . . . . . . . . . . . . .   3
     3.1.  ACs Terminated by One or Multiple Customer Edges (CEs)  .   3
     3.2.  Separate AC Provisioning vs. Actual VPN Service
           Provisioning  . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Module Tree Structure . . . . . . . . . . . . . . . . . . . .   6
   5.  The AC Glue ("ietf-ac-glue") YANG Module  . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Appendix A.  An Example . . . . . . . . . . . . . . . . . . . . .  13
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   The document specifies a YANG module (Section 5) that updates
   existing service and network Virtual Private Network (VPN) modules
   with the required information to bind specific services to Attachment
   Circuits (ACs) that are created using the AC service model
   [I-D.ietf-opsawg-teas-attachment-circuit], specifically the following
   modules are augmented:

   *  The Layer 2 Service Model (L2SM) [RFC8466]

   *  The Layer 3 Service Model (L3SM) [RFC8299]

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   *  The Layer 2 Network Model (L2NM) [RFC9291]

   *  The Layer 3 Network Model (L3NM) [RFC9182]

   Likewise, the document augments the L2NM and L3NM with references to
   the ACs that are managed using the AC network model
   [I-D.ietf-opsawg-ntw-attachment-circuit].

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

   An example to illustrate the use of the model is provided in
   Appendix A.

2.  Conventions and Definitions

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

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

   This document uses terms defined in
   [I-D.ietf-opsawg-teas-attachment-circuit].

   LxSM refers to both the L2SM and the L3SM.

   LxNM refers to both the L2NM and the L3NM.

3.  Sample Uses of the Data Models

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

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

   *  A Customer Edges (CEs) can be either a physical device or a
      logical entity.  Such logical entity is typically a software
      component (e.g., a virtual service function that is hosted within
      the provider's network or a third-party infrastructure).  A CE is
      seen by the network as a peer Service Attachment Point (SAP)
      [RFC9408].

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

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

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

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

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

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

                         Figure 1: Examples of ACs

3.2.  Separate AC Provisioning vs. Actual VPN Service Provisioning

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

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   bound to the bearer or AC.

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

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

                   Figure 2: An Example of AC Model Usage

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4.  Module Tree Structure

   [RFC8299] specifies that a "site-network-access" attachment is
   achieved through a "bearer" with an "ip-connection" on top.  From
   that standpoint, a "site-network-access" is mapped to an attachment
   circuit with both Layer 2 and 3 properties as per
   [I-D.ietf-opsawg-teas-attachment-circuit].  [RFC8466] specifies that
   a "site-network-access" represents an logical layer 2 connection to a
   site.  A "site-network-access" can thus be mapped to an attachment
   circuit with Layer 2 properties
   [I-D.ietf-opsawg-teas-attachment-circuit].  Similarly, "vpn-network-
   access" defined in both [RFC9182] and [RFC9282] is mapped to an
   attachment circuit as per [I-D.ietf-opsawg-teas-attachment-circuit]
   or [I-D.ietf-opsawg-ntw-attachment-circuit].

   As such, ACs created using the "ietf-ac-svc" module
   [I-D.ietf-opsawg-teas-attachment-circuit] can be referenced in other
   VPN-related modules (e.g., L2SM, L3SM, L2NM, and L3NM).  Also, ACs
   managed using "ietf-ac-ntw" [I-D.ietf-opsawg-ntw-attachment-circuit]
   can be referenced in VPN-related network modules (mainly, L2NM and
   L3NM).  The required augmentations to that aim as shown in Figure 3.

     augment /l2vpn-svc:l2vpn-svc/l2vpn-svc:sites/l2vpn-svc:site
               /l2vpn-svc:site-network-accesses:
       +--rw ac-svc-ref*   ac-svc:attachment-circuit-reference
     augment /l3vpn-svc:l3vpn-svc/l3vpn-svc:sites/l3vpn-svc:site
               /l3vpn-svc:site-network-accesses:
       +--rw ac-svc-ref*   ac-svc:attachment-circuit-reference
     augment /l2nm:l2vpn-ntw/l2nm:vpn-services/l2nm:vpn-service
               /l2nm:vpn-nodes/l2nm:vpn-node/l2nm:vpn-network-accesses:
       +--rw ac-svc-ref*   ac-svc:attachment-circuit-reference
       +--rw ac-ntw-ref*   ac-ntw:attachment-circuit-reference
     augment /l3nm:l3vpn-ntw/l3nm:vpn-services/l3nm:vpn-service
               /l3nm:vpn-nodes/l3nm:vpn-node/l3nm:vpn-network-accesses:
       +--rw ac-svc-ref*   ac-svc:attachment-circuit-reference
       +--rw ac-ntw-ref*   ac-ntw:attachment-circuit-reference

                      Figure 3: AC Glue Tree Structure

5.  The AC Glue ("ietf-ac-glue") YANG Module

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

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     import ietf-l3vpn-svc {
       prefix l3vpn-svc;
       reference
         "RFC 8299: YANG Data Model for L3VPN Service Delivery";
     }
     import ietf-l2vpn-svc {
       prefix l2vpn-svc;
       reference
         "RFC 8466: A YANG Data Model for Layer 2 Virtual Private
                    Network (L2VPN) Service Delivery";
     }
     import ietf-l3vpn-ntw {
       prefix l3nm;
       reference
         "RFC 9182: A YANG Network Data Model for Layer 3 VPNs";
     }
     import ietf-l2vpn-ntw {
       prefix l2nm;
       reference
         "RFC 9291: A YANG Network Data Model for Layer 2 VPNs";
     }
     import ietf-ac-svc {
       prefix ac-svc;
       reference
         "RFC SSSS: YANG Service Data Models for Attachment Circuits";
     }
     import ietf-ac-ntw {
       prefix ac-ntw;
       reference
         "RFC NNNN: A Network YANG Data Model for Attachment Circuits";
     }

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

        Editor:   Mohamed Boucadair
                  <mailto:mohamed.boucadair@orange.com>
        Author:   Richard Roberts
                  <mailto:rroberts@juniper.net>
        Author:   Samier Barguil
                  <mailto:ssamier.barguil_giraldo@nokia.com>
        Author:   Oscar Gonzalez de Dios
                  <mailto:oscar.gonzalezdedios@telefonica.com>";
     description
       "This YANG module defines a YANG model for augmenting the LxSM

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        and the LxNM with attachment circuit references.

        Copyright (c) 2023 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

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

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

     revision 2023-11-13 {
       description
         "Initial revision.";
       reference
         "RFC XXXX: A YANG Data Model for Augmenting VPN Service
                    and Network Models with Attachment Circuits";
     }

     grouping ac-svc-glue {
       description
         "A set of service-specific AC-related data.";
       leaf-list ac-svc-ref {
         type ac-svc:attachment-circuit-reference;
         description
           "A reference to the AC as exposed at the service that
            was provisionned using the ACaaS module.";
       }
     }

     grouping ac-glue {
       description
         "A set of AC-related data.";
       leaf-list ac-svc-ref {
         type ac-svc:attachment-circuit-reference;
         description
           "A reference to the AC as exposed at the service that
            was provisionned using the ACaaS module.";
       }
       leaf-list ac-ntw-ref {
         type ac-ntw:attachment-circuit-reference;
         description
           "A reference to the AC that  was provisionned
            using the AC network module.";

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       }
     }

     augment "/l2vpn-svc:l2vpn-svc"
           + "/l2vpn-svc:sites/l2vpn-svc:site"
           + "/l2vpn-svc:site-network-accesses" {
       description
         "Augments VPN network access with AC provisioning details.";

       uses ac-svc-glue;
     }

     augment "/l3vpn-svc:l3vpn-svc"
           + "/l3vpn-svc:sites/l3vpn-svc:site"
           + "/l3vpn-svc:site-network-accesses" {
       description
         "Augments VPN network access with AC provisioning details.";

       uses ac-svc-glue;
     }

     augment "/l2nm:l2vpn-ntw/l2nm:vpn-services/l2nm:vpn-service"
           + "/l2nm:vpn-nodes/l2nm:vpn-node"
           + "/l2nm:vpn-network-accesses" {
       description
         "Augments VPN network access with AC provisioning details.";

       uses ac-glue;
     }

     augment "/l3nm:l3vpn-ntw/l3nm:vpn-services/l3nm:vpn-service"
           + "/l3nm:vpn-nodes/l3nm:vpn-node"
           + "/l3nm:vpn-network-accesses" {
       description
         "Augments VPN network access with AC provisioning details.";

       uses ac-glue;
     }
   }
   <CODE ENDS>

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6.  Security Considerations

   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.

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

   *  TBC

   *  TBC

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  These are the subtrees and data
   nodes and their sensitivity/vulnerability in the "ietf-ac-glue"
   module:

   *  TBC

   *  TBC

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-glue
      Registrant Contact:  The IESG.
      XML:  N/A; the requested URI is an XML namespace.

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

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

8.  References

8.1.  Normative References

   [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-01, 27 November 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-
              ntw-attachment-circuit-01>.

   [I-D.ietf-opsawg-teas-attachment-circuit]
              Boucadair, M., Roberts, R., de Dios, O. G., Barguil, S.,
              and B. Wu, "YANG Data Models for 'Attachment Circuits'-as-
              a-Service (ACaaS)", Work in Progress, Internet-Draft,
              draft-ietf-opsawg-teas-attachment-circuit-02, 27 November
              2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
              opsawg-teas-attachment-circuit-02>.

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

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

   [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>.

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   [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>.

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

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

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC9282]  Rosen, B., "Responsibility Change for the RFC Series",
              BCP 9, RFC 9282, DOI 10.17487/RFC9282, June 2022,
              <https://www.rfc-editor.org/rfc/rfc9282>.

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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>.

8.2.  Informative References

   [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>.

   [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>.

   [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>.

Appendix A.  An Example

   Let's consider the example depicted in Figure 4 with two customer
   terminating points (CE1 and CE2).  Let's also assume that the bearers
   to attach these CEs to the provider network are already in place.
   References to the identify these bearers are shown in the figure.

                   .-----.   .--------------.   .-----.
       .----.      | PE1 +===+              +===+ PE2 |      .----.
       | CE1+------+"450"|   |     MPLS     |   |"451"+------+ CE2|
       '----'   ^  '-----'   |              |   '-----'   ^  '----'
                |            |     Core     |             |
           Bearer:1234       '--------------'         Bearer:5678

                         Figure 4: Topology Example

   The AC service model [I-D.ietf-opsawg-teas-attachment-circuit] can be
   used by the provider to manage and expose the ACs over existing
   bearers as shown in Figure 5.

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     {
        "ietf-ac-svc:attachment-circuits":{
           "ac-group-profile":[
              {
                 "name":"an-ac-profile",
                 "l2-connection":{
                    "encapsulation":{
                       "encap-type":"ietf-vpn-common:dot1q",
                       "dot1q":{
                          "tag-type":"ietf-vpn-common:c-vlan",
                          "cvlan-id":550
                       }
                    }
                 },
                 "service":{
                    "mtu":1550,
                    "svc-pe-to-ce-bandwidth":{
                       "pe-to-ce-bandwidth":[
                          {
                             "bw-type":"ietf-vpn-common:bw-per-port",
                             "cir":"20480000"
                          }
                       ]
                    },
                    "svc-ce-to-pe-bandwidth":{
                       "ce-to-pe-bandwidth":[
                          {
                             "bw-type":"ietf-vpn-common:bw-per-port",
                             "cir":"20480000"
                          }
                       ]
                    },
                    "qos":{
                       "qos-profile":{
                          "qos-profile":[
                             {
                                "profile":"QoS_Profile_A",
                                "direction":"ietf-vpn-common:both"
                             }
                          ]
                       }
                    }
                 }
              }
           ],
           "ac":[
              {
                 "name":"ac-1",

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                 "description":"First attachment",
                 "ac-group-profile":["an-ac-profile"],
                 "l2-connection":{
                    "bearer-reference":"1234"
                 }
              },
              {
                 "name":"ac-2",
                 "description":"Second attachment",
                 "ac-group-profile": ["an-ac-profile"],
                 "l2-connection":{
                    "bearer-reference":"5678"
                 }
              }
           ]
        }
     }

                     Figure 5: ACs Created Using ACaaS

   Let's now consider that the customer wants to request a VPLS service
   between the sites as shown in Figure 6.

                   |----------  VPLS "1543" ----------|

                   .-----.   .--------------.   .-----.
       .----.  AC1 | PE1 +===+              +===+ PE2 |  AC2 .----.
       | CE1+------+"450"|   |     MPLS     |   |"451"+------+ CE2|
       '----'   ^  '-----'   |              |   '-----'   ^  '----'
                |            |     Core     |             |
           Bearer:1234       '--------------'         Bearer:5678

                         Figure 6: Example of VPLS

   To that aim, existing ACs are referenced during the creation of the
   VPLS instance using the L2NM and the "ietf-ac-glue" as shown in
   Figure 7.

      {
        "ietf-l2vpn-ntw:l2vpn-ntw": {
          "vpn-services": {
            "vpn-service": [
              {
                "vpn-id": "1543",
                "vpn-name": "CORPO-EXAMPLE",
                "customer-name": "EXAMPLE",
                "vpn-type": "ietf-vpn-common:vpls",
                "vpn-service-topology": "ietf-vpn-common:hub-spoke",

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                "bgp-ad-enabled": false,
                "signaling-type": "ietf-vpn-common:ldp-signaling",
                "global-parameters-profiles": {
                  "global-parameters-profile": [
                    {
                      "profile-id": "simple-profile",
                      "ce-vlan-preservation": true,
                      "ce-vlan-cos-preservation": true
                    }
                  ]
                },
                "vpn-nodes": {
                  "vpn-node": [
                    {
                      "vpn-node-id": "450",
                      "ne-id": "2001:db8:5::1",
                      "role": "ietf-vpn-common:hub-role",
                      "status": {
                        "admin-status": {
                          "status": "ietf-vpn-common:admin-up"
                        }
                      },
                      "active-global-parameters-profiles": {
                        "global-parameters-profile": [
                          {
                            "profile-id": "simple-profile"
                          }
                        ]
                      },
                      "signaling-option": {
                        "ldp-or-l2tp": {
                          "t-ldp-pw-type": "vpls-type",
                          "pw-peer-list": [
                            {
                              "peer-addr": "2001:db8:50::1",
                              "vc-id": "1543"
                            }
                          ]
                        }
                      },
                      "vpn-network-accesses": {
                        "ietf-ac-glue:ac-svc-ref": ["ac-1"]
                      }
                    },
                    {
                      "vpn-node-id": "451",
                      "ne-id": "2001:db8:50::1",
                      "role": "ietf-vpn-common:spoke-role",

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                      "status": {
                        "admin-status": {
                          "status": "ietf-vpn-common:admin-up"
                        }
                      },
                      "active-global-parameters-profiles": {
                        "global-parameters-profile": [
                          {
                            "profile-id": "simple-profile"
                          }
                        ]
                      },
                      "signaling-option": {
                        "ldp-or-l2tp": {
                          "t-ldp-pw-type": "vpls-type",
                          "pw-peer-list": [
                            {
                              "peer-addr": "2001:db8:5::1",
                              "vc-id": "1543"
                            }
                          ]
                        }
                      },
                      "vpn-network-accesses": {
                        "ietf-ac-glue:ac-svc-ref": ["ac-2"]
                      }
                    }
                  ]
                }
              }
            ]
          }
        }
      }

         Figure 7: Example of a VPLS Request Using L2NM and AC Glue
                               (Message Body)

   Note that before implementing the VPLS creation request, the provider
   service orchestrator may first check if the VPLS service can be
   provided to the customer using the target delivery locations.  The
   orchestrator will use the SAP model [RFC9408] as exemplified in
   Figure 8.  This example assumes that the query concerns only PE1.  A
   similar query can be issued for PE2.

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            {
               "ietf-sap-ntw:service":[
                  {
                     "service-type":"ietf-vpn-common:vpls",
                     "sap":[
                        {
                           "sap-id":"sap#1",
                           "peer-sap-id":[
                              "ce-1"
                           ],
                           "description":"A parent SAP",
                           "attachment-interface":"GE0/6/1",
                           "interface-type":"ietf-sap-ntw:phy",
                           "role":"ietf-sap-ntw:uni",
                           "allows-child-saps":true,
                           "sap-status":{
                              "status":"ietf-vpn-common:op-up"
                           }
                        }
                     ]
                  }
               ]
            }

              Figure 8: Example of SAP Response (Message Body)

   The response in Figure 8 indicates that the VPLS service can be
   delivered to CE1.  [I-D.ietf-opsawg-ntw-attachment-circuit] can be
   also used to access AC-related details that are bound to the target
   SAP (Figure 9).

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

   {
      "ietf-sap-ntw:service":[
         {
            "service-type":"ietf-vpn-common:vpls",
            "sap":[
               {
                  "sap-id":"sap#1",
                  "peer-sap-id":[
                     "ce-1"
                  ],
                  "description":"A parent SAP",
                  "attachment-interface":"GE0/6/1",
                  "interface-type":"ietf-sap-ntw:phy",
                  "role":"ietf-sap-ntw:uni",
                  "allows-child-saps":true,

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                  "sap-status":{
                     "status":"ietf-vpn-common:op-up"
                  }
               },
               {
                  "sap-id":"sap#11",
                  "description":"A child SAP",
                  "parent-termination-point":"GE0/6/4",
                  "attachment-interface":"GE0/6/4.2",
                  "interface-type":"ietf-sap-ntw:logical",
                  "encapsulation-type":"ietf-vpn-common:vlan-type",
                  "sap-status":{
                     "status":"ietf-vpn-common:op-up"
                  },
                  "ietf-ac-ntw:ac":[
                     {
                        "name":"ac-11",
                        "ac-svc-ref":"ac-1",
                        "peer-sap-id":[
                           "ce-1"
                        ],
                        "status":{
                           "admin-status":{
                              "status":"ietf-vpn-common:admin-up"
                           },
                           "oper-status":{
                              "status":"ietf-vpn-common:op-up"
                           }
                        },
                        "l2-connection":{
                           "encapsulation":{
                              "encap-type":"ietf-vpn-common:dot1q",
                              "dot1q":{
                                 "tag-type":"ietf-vpn-common:c-vlan",
                                 "cvlan-id":550
                              }
                           },
                           "bearer-reference":"1234"
                        },
                        "service":{
                           "mtu":1550,
                           "svc-pe-to-ce-bandwidth":{
                              "pe-to-ce-bandwidth":[
                                 {
                                    "cir":"20480000"
                                 }
                              ]
                           },

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                           "svc-ce-to-pe-bandwidth":{
                              "ce-to-pe-bandwidth":[
                                 {
                                    "cir":"20480000"
                                 }
                              ]
                           },
                           "qos":{
                              "qos-profile":{
                                 "qos-profile":[
                                    {
                                       "profile":"QoS_Profile_A",
                                       "direction":"ietf-vpn-common:\
                                                                   both"
                                    }
                                 ]
                              }
                           }
                        }
                     }
                  ]
               }
            ]
         }
      ]
   }

          Figure 9: Example of AC Network Response (Message Body)

Acknowledgments

   Thanks to Bo Wu for the review and comments.

Authors' Addresses

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

   Richard Roberts
   Juniper
   Email: rroberts@juniper.net

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

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   Oscar Gonzalez de Dios
   Telefonica
   Email: oscar.gonzalezdedios@telefonica.com

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