Internet-Draft AC Glue for VPN Models February 2024
Boucadair, et al. Expires 12 August 2024 [Page]
Workgroup:
OPSAWG
Internet-Draft:
draft-ietf-opsawg-ac-lxsm-lxnm-glue-06
Published:
Intended Status:
Standards Track
Expires:
Authors:
M. Boucadair, Ed.
Orange
R. Roberts
Juniper
S. B. Giraldo
Nokia
O. G. D. Dios
Telefonica

A YANG Data Model for Augmenting VPN Service and Network Models with Attachment Circuits

Abstract

The document specifies a module that updates existing service and network Virtual Private 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."

This Internet-Draft will expire on 12 August 2024.

Table of Contents

1. Introduction

The document specifies a YANG module ("ietf-ac-glue", 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:

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 "ietf-ac-glue" 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.

  • 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 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

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 Layers 2 and 3 properties as per [I-D.ietf-opsawg-teas-attachment-circuit]. [RFC8466] specifies that a 'site-network-access' represents a 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 [RFC9291] 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 the "ietf-ac-ntw" module [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 are shown in Figure 3.

module: ietf-ac-glue

  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 /l2vpn-svc:l2vpn-svc/l2vpn-svc:sites/l2vpn-svc:site
            /l2vpn-svc:site-network-accesses
            /l2vpn-svc:site-network-access:
    +--rw ac-svc-ref?   ac-svc:attachment-circuit-reference {ac-glue}?
  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 /l3vpn-svc:l3vpn-svc/l3vpn-svc:sites/l3vpn-svc:site
            /l3vpn-svc:site-network-accesses
            /l3vpn-svc:site-network-access:
    +--rw ac-svc-ref?   ac-svc:attachment-circuit-reference {ac-glue}?
  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-ref]
       +--rw ac-ref         leafref
       +--rw node-ref?      leafref
       +--rw network-ref?   -> /nw:networks/network/network-id
  augment /l2nm:l2vpn-ntw/l2nm:vpn-services/l2nm:vpn-service
            /l2nm:vpn-nodes/l2nm:vpn-node/l2nm:vpn-network-accesses
            /l2nm:vpn-network-access:
    +--rw ac-svc-ref?   ac-svc:attachment-circuit-reference {ac-glue}?
    +--rw ac-ntw-ref {ac-glue}?
       +--rw ac-ref?        leafref
       +--rw node-ref?      leafref
       +--rw network-ref?   -> /nw:networks/network/network-id
  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-ref]
       +--rw ac-ref         leafref
       +--rw node-ref?      leafref
       +--rw network-ref?   -> /nw:networks/network/network-id
  augment /l3nm:l3vpn-ntw/l3nm:vpn-services/l3nm:vpn-service
            /l3nm:vpn-nodes/l3nm:vpn-node/l3nm:vpn-network-accesses
            /l3nm:vpn-network-access:
    +--rw ac-svc-ref?   ac-svc:attachment-circuit-reference {ac-glue}?
    +--rw ac-ntw-ref {ac-glue}?
       +--rw ac-ref?        leafref
       +--rw node-ref?      leafref
       +--rw network-ref?   -> /nw:networks/network/network-id
Figure 3: AC Glue Tree Structure

When an AC is referenced within a specific network access, then that AC information takes precedence over any overlapping information that is also enclosed for this network access.

The module includes provisions to reference ACs within or outside a VPN network access to accommodate deployment contexts where an AC reference may be created before or after a VPN instance is created. Appendix A.1 illustrates how an AC reference can be included as part of a specific VPN network access, while Appendix A.2 shows how AC references can be indicated outside individual VPN network access entries.

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;

  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
     and the LxNM with attachment circuit references.

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

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

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

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

  feature ac-glue {
    description
      "The VPN implementation supports binding a specific VPN
       network access or site access to an attachment circuit.";
  }

  grouping single-ac-svc-ref {
    description
      "A grouping with single reference to a service AC.";
    leaf ac-svc-ref {
      type ac-svc:attachment-circuit-reference;
      description
        "A reference to the AC as exposed at the service that
         was provisioned using the ACaaS module.";
    }
  }

  grouping single-ac-svc-ntw-ref {
    description
      "A grouping with single AC references.";
    leaf ac-svc-ref {
      type ac-svc:attachment-circuit-reference;
      description
        "A reference to the AC as exposed at the service that
         was provisioned using the ACaaS module.";
    }
    container ac-ntw-ref {
      uses ac-ntw:attachment-circuit-reference;
      description
        "A reference to the AC that  was provisioned
         using the AC network module.";
    }
  }

  grouping ac-svc-ref {
    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 provisioned using the ACaaS module.";
    }
  }

  grouping ac-svc-ntw-ref {
    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 provisioned using the ACaaS module.";
    }
    list ac-ntw-ref {
      key "ac-ref";
      description
        "A reference to the AC that was provisioned
         using the AC network module.";
      uses ac-ntw:attachment-circuit-reference;
    }
  }

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

    uses ac-svc-ref;
  }

  augment "/l2vpn-svc:l2vpn-svc"
        + "/l2vpn-svc:sites/l2vpn-svc:site"
        + "/l2vpn-svc:site-network-accesses"
        + "/l2vpn-svc:site-network-access" {
    if-feature "ac-glue";
    description
      "Augments VPN site network access with a reference to
        a service AC.";

    uses single-ac-svc-ref;
  }

  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-ref;
  }

  augment "/l3vpn-svc:l3vpn-svc"
        + "/l3vpn-svc:sites/l3vpn-svc:site"
        + "/l3vpn-svc:site-network-accesses"
        + "/l3vpn-svc:site-network-access" {
    if-feature "ac-glue";
    description
      "Augments VPN site network access with a reference to
       a service AC.";

    uses single-ac-svc-ref;
  }

  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-svc-ntw-ref;
  }

  augment "/l2nm:l2vpn-ntw/l2nm:vpn-services/l2nm:vpn-service"
        + "/l2nm:vpn-nodes/l2nm:vpn-node"
        + "/l2nm:vpn-network-accesses"
        + "/l2nm:vpn-network-access" {
    if-feature "ac-glue";
    description
      "Augments VPN network access with service and network
       references to an AC.";

    uses single-ac-svc-ntw-ref;
  }

  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-svc-ntw-ref;
  }

  augment "/l3nm:l3vpn-ntw/l3nm:vpn-services/l3nm:vpn-service"
        + "/l3nm:vpn-nodes/l3nm:vpn-node"
        + "/l3nm:vpn-network-accesses"
        + "/l3nm:vpn-network-access" {
    if-feature "ac-glue";
    description
      "Augments VPN network access with service and network
       references to an AC.";

    uses single-ac-svc-ntw-ref;
  }
}

<CODE ENDS>

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:

'ac-svc-ref' and 'ac-ntw-ref':

An attacker who is able to access network nodes can undertake various attacks, such as deleting a running VPN service, interrupting all the traffic of a client. Specifically, an attacker may modify (including delete) the ACs that are bound to a running service, leading to malfunctioning of the service and therefore to Service Level Agreement (SLA) violations. : Such activity can be detected by adequately monitoring and tracking network configuration changes.

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:

'ac-svc-ref' and 'ac-ntw-ref':

These references do not expose per se privacy-related information, however 'ac-svc-ref' may be used to track the set of VPN instances in which a given customer is involved.

Note that, unlike 'ac-svc-ref', 'ac-ntw-ref' is unique within the scope of a node and may multiplex many peer CEs.

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.

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-04, , <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-ntw-attachment-circuit-04>.
[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-05, , <https://datatracker.ietf.org/doc/html/draft-ietf-opsawg-teas-attachment-circuit-05>.
[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3688]
Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc6241>.
[RFC6242]
Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, , <https://www.rfc-editor.org/rfc/rfc6242>.
[RFC8040]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, , <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, , <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, , <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, , <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, , <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, , <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, , <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, , <https://www.rfc-editor.org/rfc/rfc9182>.
[RFC9291]
Boucadair, M., Ed., Gonzalez de Dios, O., Ed., Barguil, S., and L. Munoz, "A YANG Network Data Model for Layer 2 VPNs", RFC 9291, DOI 10.17487/RFC9291, , <https://www.rfc-editor.org/rfc/rfc9291>.

8.2. Informative References

[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 IETF Network Slice Service", Work in Progress, Internet-Draft, draft-ietf-teas-ietf-network-slice-nbi-yang-08, , <https://datatracker.ietf.org/doc/html/draft-ietf-teas-ietf-network-slice-nbi-yang-08>.
[RFC4364]
Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, , <https://www.rfc-editor.org/rfc/rfc4364>.
[RFC4664]
Andersson, L., Ed. and E. Rosen, Ed., "Framework for Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, DOI 10.17487/RFC4664, , <https://www.rfc-editor.org/rfc/rfc4664>.
[RFC7665]
Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, , <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, , <https://www.rfc-editor.org/rfc/rfc8340>.
[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, , <https://www.rfc-editor.org/rfc/rfc9408>.

Appendix A. Examples

A.1. A Service AC Reference within The VPN Network Access

Let's consider the example depicted in Figure 4 which is inspired from Section 2.1 of [RFC4664]. Each PE is servicing two CEs. Let's also assume that the service references to identify attachment circuits with these CEs are shown in the figure.

.-----.                                           .-----.
|     |  AC1                                AC2   |     |
| CE1 |--+                                     +--| CE2 |
|     |  |    .-----.   .-----.     .-----.    |  |     |
'-----'  +----|---- |   |  P  |     | ----+----+  '-----'
              |VPWS\----|-----|-----|/VPWS|
              | PE1 |===|=====|=====| PE2 |
              |    /|---|-----|-----|\\   |
.-----.  +----|---- |   |     |     | ----|----+  .-----.
|     |  |    '-----'   '-----'     '-----'    |  |     |
| CE3 |--+                                     +--| CE4 |
|     |  AC3                                 AC4  |     |
'-----'                                           '-----'
Figure 4: VPWS Topology Example

As shown in Figure 5, the service AC references can be explicitly indicated in the L2NM query for the realization of the Virtual Private Wire Service (VPWS) Section 3.1.1 of [RFC4664]).

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

{
   "ietf-l2vpn-ntw:l2vpn-ntw":{
      "vpn-services":{
         "vpn-service":[
            {
               "vpn-id":"vpws12345",
               "vpn-description":"Sample VPWS with AC service \
                                                         references",
               "customer-name":"customer-12345",
               "vpn-type":"ietf-vpn-common:vpws",
               "bgp-ad-enabled":true,
               "signaling-type":"ietf-vpn-common:ldp-signaling",
               "global-parameters-profiles":{
                  "global-parameters-profile":[
                     {
                        "profile-id":"simple-profile",
                        "local-autonomous-system":65550,
                        "rd-auto":{
                           "auto":[
                              null
                           ]
                        },
                        "vpn-target":[
                           {
                              "id":1,
                              "route-targets":[
                                 {
                                    "route-target":"0:65535:1"
                                 }
                              ],
                              "route-target-type":"both"
                           }
                        ]
                     }
                  ]
               },
               "vpn-nodes":{
                  "vpn-node":[
                     {
                        "vpn-node-id":"pe1",
                        "ne-id":"2001:db8:100::1",
                        "active-global-parameters-profiles":{
                           "global-parameters-profile":[
                              {
                                 "profile-id":"simple-profile"
                              }
                           ]
                        },
                        "bgp-auto-discovery":{
                           "vpn-id":"587"
                        },
                        "signaling-option":{
                           "advertise-mtu":true,
                           "ldp-or-l2tp":{
                              "saii":1,
                              "remote-targets":[
                                 {
                                    "taii":2
                                 }
                              ],
                              "t-ldp-pw-type":"ethernet"
                           }
                        },
                        "vpn-network-accesses":{
                           "vpn-network-access":[
                              {
                                 "id":"1/1/1.1",
                                 "interface-id":"1/1/1",
                                 "description":"Interface to CE1",
                                 "active-vpn-node-profile":"simple-\
                                                            profile",
                                 "status":{
                                    "admin-status":{
                                       "status":"ietf-vpn-common:\
                                                            admin-up"
                                    },
                                    "ietf-ac-glue:ac-svc-ref":"AC1"
                                 }
                              },
                              {
                                 "id":"1/1/3.1",
                                 "interface-id":"1/1/3",
                                 "description":"Interface to CE3",
                                 "active-vpn-node-profile":"simple-\
                                                            profile",
                                 "status":{
                                    "admin-status":{
                                       "status":"ietf-vpn-common:\
                                                            admin-up"
                                    },
                                    "ietf-ac-glue:ac-svc-ref":"AC3"
                                 }
                              }
                           ]
                        }
                     },
                     {
                        "vpn-node-id":"pe2",
                        "ne-id":"2001:db8:200::1",
                        "active-global-parameters-profiles":{
                           "global-parameters-profile":[
                              {
                                 "profile-id":"simple-profile"
                              }
                           ]
                        },
                        "bgp-auto-discovery":{
                           "vpn-id":"587"
                        },
                        "signaling-option":{
                           "advertise-mtu":true,
                           "ldp-or-l2tp":{
                              "saii":2,
                              "remote-targets":[
                                 {
                                    "taii":1
                                 }
                              ],
                              "t-ldp-pw-type":"ethernet"
                           }
                        },
                        "vpn-network-accesses":{
                           "vpn-network-access":[
                              {
                                 "id":"2/1/1.1",
                                 "interface-id":"2/1/1",
                                 "description":"Interface to CE2",
                                 "active-vpn-node-profile":"simple-\
                                                            profile",
                                 "status":{
                                    "admin-status":{
                                       "status":"ietf-vpn-common:\
                                                            admin-up"
                                    },
                                    "ietf-ac-glue:ac-svc-ref":"AC2"
                                 }
                              },
                              {
                                 "id":"2/1/2.1",
                                 "interface-id":"2/1/1",
                                 "description":"Interface to CE4",
                                 "active-vpn-node-profile":"simple-\
                                                            profile",
                                 "status":{
                                    "admin-status":{
                                       "status":"ietf-vpn-common:\
                                                            admin-up"
                                    },
                                    "ietf-ac-glue:ac-svc-ref":"AC4"
                                 }
                              }
                           ]
                        }
                     }
                  ]
               }
            }
         ]
      }
   }
}
Figure 5: Example of VPWS Creation with AC Service References

A.2. Network and Service AC References

Let's consider the example depicted in Figure 6 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 6: 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 7.

{
   "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",
            "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 7: ACs Created Using ACaaS

Let's now consider that the customer wants to request a VPLS instance between the sites as shown in Figure 8.

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

            .-----.   .--------------.   .-----.
.----.  AC1 | PE1 +===+              +===+ PE2 |  AC2 .----.
| CE1+------+"450"|   |     MPLS     |   |"451"+------+ CE2|
'----'   ^  '-----'   |              |   '-----'   ^  '----'
         |            |     Core     |             |
    Bearer:1234       '--------------'         Bearer:5678
Figure 8: 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 9.

{
  "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",
          "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",
                "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 9: Example of a VPLS Request Using L2NM and AC Glue (Message Body)

Note that before implementing the VPLS instance 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 uses the SAP model [RFC9408] as exemplified in Figure 10. This example assumes that the query concerns only PE1. A similar query can be issued for PE2.

{
   "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 10: Example of SAP Response (Message Body)

The response in Figure 10 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 11).

{
   "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"
               }
            },
            {
               "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":[
                  {
                     "ac-ref":"ac-1",
                     "node-ref":"example:pe2",
                     "network-ref":"example:an-id"
                  }
               ]
            }
         ]
      }
   ]
}
Figure 11: Example of AC Network Response with SAP (Message Body)

The provisioned AC at PE1 can be retrieved using the AC network model as depicted in Figure 12.

{
   "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"
                  }
               ]
            },
            "svc-ce-to-pe-bandwidth":{
               "ce-to-pe-bandwidth":[
                  {
                     "cir":"20480000"
                  }
               ]
            },
            "qos":{
               "qos-profile":{
                  "qos-profile":[
                     {
                        "qos-profile-ref":"QoS_Profile_A",
                        "network-ref":"example:an-id",
                        "direction":"ietf-vpn-common:both"
                     }
                  ]
               }
            }
         }
      }
   ]
}
Figure 12: Example of AC Network Response (Message Body)

Acknowledgments

Thanks to Bo Wu for the review and comments.

Thanks to Martin Björklund for the yangdoctors review.

Authors' Addresses

Mohamed Boucadair (editor)
Orange
Richard Roberts
Juniper
Samier Barguil Giraldo
Nokia
Oscar Gonzalez de Dios
Telefonica