path: root/doc/rfc/rfc9408.txt

Internet Engineering Task Force (IETF)                 M. Boucadair, Ed.
Request for Comments: 9408                                        Orange
Category: Standards Track                            O. Gonzalez de Dios
ISSN: 2070-1721                                               Telefonica
                                                              S. Barguil
                                                                   Nokia
                                                                   Q. Wu
                                                                  Huawei
                                                                V. Lopez
                                                                   Nokia
                                                               June 2023


     A YANG Network Data Model for Service Attachment Points (SAPs)

Abstract

   This document defines a YANG data model for representing an abstract
   view of the provider network topology that contains the points from
   which its services can be attached (e.g., basic connectivity, VPN,
   network slices).  Also, the model can be used to retrieve the points
   where the services are actually being delivered to customers
   (including peer networks).

   This document augments the 'ietf-network' data model defined in RFC
   8345 by adding the concept of Service Attachment Points (SAPs).  The
   SAPs are the network reference points to which network services, such
   as Layer 3 Virtual Private Network (L3VPN) or Layer 2 Virtual Private
   Network (L2VPN), can be attached.  One or multiple services can be
   bound to the same SAP.  Both User-to-Network Interface (UNI) and
   Network-to-Network Interface (NNI) are supported in the SAP data
   model.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9408.

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.  Terminology
   3.  Sample SAP Network Model Usage
   4.  Relationship to Other YANG Data Models
   5.  SAP Module Tree Structure
   6.  SAP YANG Module
   7.  IANA Considerations
   8.  Security Considerations
   9.  References
     9.1.  Normative References
     9.2.  Informative References
   Appendix A.  A Simplified SAP Network Example
   Appendix B.  A Simple Example of the SAP Network Model: Node Filter
   Appendix C.  An Example of an NNI SAP: Inter-AS VPN Option A
   Appendix D.  Examples of Using the SAP Network Model in Service
           Creation
   Acknowledgements
   Authors' Addresses

1.  Introduction

   Service providers offer a variety of network services to their
   customers.  Such services include, but are not limited to, Virtual
   Private Networks (VPNs), Software-Defined Wide-Area Network (SD-WAN)
   overlay networks [BGP-SDWAN-USAGE], and network slices
   [IETF-NETWORK-SLICES].  In order to rationalize the overall service
   operations and allow for more automated service provisioning
   procedures, service providers need to maintain a view on where
   services can be delivered to customers.  For example, such a view can
   be used to feed an intelligence entity that is responsible for
   service order handling, service feasibility checks, tracking per-
   service coverage, etc. (e.g., Section 3.2 of [RFC8969]).  To that
   aim, this document introduces the concept of Service Attachment
   Points (SAPs).

   The SAPs represent the network reference points where network
   services can be delivered to customers.  For example, this concept is
   used to decide where to attach and thus deliver the service in the
   Layer 3 VPN Service Model (L3SM) [RFC8299] and the Layer 2 VPN
   Service Model (L2SM) [RFC8466].  It can also be used to retrieve
   where such services are delivered to customers through the network
   configuration described in the Layer 3 VPN Network Model (L3NM)
   [RFC9182] and the Layer 2 VPN Network Model (L2NM) [RFC9291].

   This document defines a YANG network model (Section 6) for
   representing, managing, and controlling the SAPs.  The data model
   augments the 'ietf-network' module [RFC8345] by adding the concept of
   SAPs.  Section 3 provides a sample usage of the model.  This document
   explains the scope and purpose of a SAP network model and its
   relationship to other models (Section 4).

   A network may support multiple services, potentially of different
   types.  Whether a SAP topology is dedicated to services of a specific
   service type or an individual service, or is shared among many
   services of different types, is deployment specific.  This document
   supports all of these deployment schemes.

   This document does not make any assumptions about the services
   provided by a network to its users.  VPN services (e.g., Layer 3
   Virtual Private Network (L3VPN) or Layer 2 Virtual Private Network
   (L2VPN)) [RFC4026] are used for illustration purposes (Appendices A
   and B).

   Given that User-to-Network Interface (UNI) and Network-to-Network
   Interface (NNI) are reference points that are widely used by
   operators to indicate the demarcation points when delivering
   services, both UNI and NNI SAPs are supported in this document.  The
   reader may refer to [MEF6], [MEF17], [RFC6004], or [RFC6215] for
   examples of discussions regarding the use of UNI and NNI reference
   points.  An example of NNI usage in a VPN context is provided in
   Appendix C.

   The YANG data model in Section 6 conforms to the Network Management
   Datastore Architecture (NMDA) [RFC8342].

2.  Terminology

   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.

   This document assumes that the reader is familiar with the contents
   of [RFC6241], [RFC7950], [RFC8345], and [RFC8309], as it uses terms
   from those RFCs.

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

   This document uses the term "network model" as defined in Section 2.1
   of [RFC8969].

   This document uses the following terms:

   Service provider:  The organization responsible for operating the
      network that offers a service (e.g., a VPN) to customers.

   Attachment Circuit (AC):  A channel that connects a Customer Edge
      (CE) to a Provider Edge (PE).

   Customer Edge (CE):  Equipment that is dedicated to a particular
      customer and is directly connected to one or more PEs via ACs.  A
      CE is usually located at the customer premises.  A CE may be
      dedicated to a single service (e.g., an L3VPN), although it may
      support multiple VPNs if each one has separate ACs.  A CE can be a
      router, a bridge, a switch, etc.

   Provider Edge (PE):  Equipment owned and managed by the service
      provider that can support multiple services (e.g., VPNs) for
      different customers.  A PE is directly connected to one or more
      CEs via ACs.

   Service Attachment Points (SAPs):  An abstraction of the network
      reference points (e.g., the PE side of an AC, or the CE side of an
      AC for a provider-managed CE) where network services can be
      delivered and/or are delivered to customers.  A SAP can be bound
      to one or multiple ACs.

3.  Sample SAP Network Model Usage

   A service provider network's management operations can be automated
   using a variety of means such as interfaces based on YANG modules
   [RFC8969] [RFC6241] [RFC8040].  From that standpoint, and considering
   the architecture depicted in Figure 1, a goal of this document is to
   provide a mechanism to show, via a YANG-based interface, an
   abstracted network view from the network controller to the service
   orchestration layer with a focus on where a service can be delivered
   to customers.  The model is also used to retrieve the network
   reference points where a service is being delivered to customers.
   For services that require resources from peer networks, the model can
   also be used to expose NNIs.

                               +-----------------+
                               |     Customer    |
                               +--------+--------+
               Customer Service Models  |
                  (e.g., L3SM, L2SM)    |
                               +--------+--------+
                               |    Service      |
                               |  Orchestration  |
                               +------+---+------+
                   Network Models     |   | SAP Network Model
                 (e.g., L3NM, L2NM)   |   |
                               +------+---+------+
                               |     Network     |
                               |   Controller    |
                               +--------+--------+
                                        |
                  +---------------------+---------------------+
                  |                  Network                  |
                  +-------------------------------------------+

                     Figure 1: SAP Network Model Usage

   The reader may refer to Section 5 of [RFC4026] for an overview of the
   building blocks that are usually invoked when characterizing a
   service provider network.

   The service orchestration layer does not need to know about all the
   internals of the underlying network (e.g., P nodes (Section 5.3.1 of
   [RFC4026])).  Figure 2 shows the abstract network view as seen by a
   service orchestrator.  However, this view is not enough to provide to
   the service orchestration layer the information to create services in
   the network.  The service topology needs to be able to expose the set
   of nodes and the attachment points associated with the nodes from
   which network services can be grafted (delivered).

                     .---------.          .---------.
                     |   PE1   |          |   PE2   |
                     '---------'          '---------'
                                \        /
                                 \------/
                                 (      )
                                (        )
                                 (      )
                                 /------\
                               /         \
                     .---------.          .---------.
                     |   PE3   |          |   PE4   |
                     '---------'          '---------'

                    Figure 2: Abstract Network Topology

   Typically, and focusing on the UNIs, the service orchestration layer
   would see a set of PEs and a set of client-facing interfaces
   (physical or logical) to which CEs can be connected (or are actually
   connected).  Such interfaces are also referred to as UNI-N (User-to-
   Network Interface, Network side) [RFC6215].  The service
   orchestration layer can use these interfaces to set up the requested
   services or to commit the delivery of a service.  Figure 3 depicts a
   sample SAP network topology that is maintained by the network
   controller and exposed to the service orchestration.

                 .-+-. .-+-. .-+-.              .-+-.       .-+-.
               .-|sap|-|sap|-|sap|-.          .-|sap|-------|sap|-.
               | '---' '---' '---' |          | '---'       '---' |
             .---.                 |          |                   |
             |sap|      PE1        |          |         PE2       |
             '---'                 |          |                   |
               |                   |          |                   |
               '-------------------'          '-------------------'


               .-------------------.          .-------------------.
               |                   |          |                   |
               |                   |          |                 .---.
               |         PE3       |          |        PE4      |sap|
               |                   |          |                 '---'
               | .---. .---. .---. |          | .---. .---. .---. |
               '-|sap|-|sap|-|sap|-'          '-|sap|-|sap|-|sap|-'
                 '-+-' '-+-' '-+-'              '-+-' '-+-' '-+-'

                      Figure 3: A SAP Network Topology

   A single SAP network topology can be used for one or multiple service
   types (e.g., L3VPN, Ethernet VPN (EVPN)).  The network controller can
   then expose the service types and associated interfaces via the SAPs.

   As shown in Figure 4, the service orchestration layer will also have
   access to a set of customer service models (e.g., the L3SM or the
   L2SM) in the customer-facing interface and a set of network models
   (e.g., the L3NM and network topology data models) in the resource-
   facing interface.  In this use case, it is assumed that the network
   controller is unaware of what happens beyond the PEs towards the CEs;
   it is only responsible for the management and control of the SAPs and
   the network between PEs.  In order to correlate between delivery
   points expressed in service requests and SAPs, the SAP model may
   include a peer customer point identifier.  That identifier can be a
   CE identifier, a site identifier, etc.

                                                        .---.
                                                        |CE2|
                                                        '-+-'
                                                          |
              .-+-. .-+-. .-+-.             .-+-.       .-+-.
            .-|sap|-|sap|-|sap|-.         .-|sap|-------|sap|-.
            | '---' '---' '---' |         | '---'       '---' |
   .---.  .---.                 |         |                   |
   |CE1+--+sap|      PE1        |         |         PE2       |
   '---'  '---'                 |         |                   |
            |                   |         |                   |
            '-------------------'         '-------------------'


            .-------------------.         .-------------------.
            |                   |         |                   |
            |                   |         |                 .---.  .---.
            |         PE3       |         |        PE4      |sap+--+CE5|
            |                   |         |                 '---'  '---'
            | .---. .---. .---. |         | .---. .---. .---. |
            '-|sap|-|sap|-|sap|-'         '-|sap|-|sap|-|sap|-'
              '-+-' '-+-' '-+-'             '-+-' '-+-' '-+-'
                            |                 |     |
                          .-+-.               |   .-+-.
                          |CE3+---------------'   |CE4|
                          '---'                   '---'

                Figure 4: Network Topology with CEs and ACs

   Refer to Appendix A for an example echoing the topology depicted in
   Figure 4.

4.  Relationship to Other YANG Data Models

   The SAP network model can be seen as inventory data associated with
   SAPs.  The model maintains an inventory of customer-facing nodes
   contained in a network relying upon [RFC8345].

   Figure 5 depicts the relationship of the SAP network model to other
   models.  The SAP network model augments the network model defined in
   [RFC8345] and imports the network topology model defined in
   [RFC8345], while other technology-specific topology models (e.g., the
   model for Traffic Engineering (TE) topologies [RFC8795] or the model
   for Layer 3 topologies [RFC8346]) augment the network topology model
   defined in [RFC8345].

                              +-------------------------+
                              |                         |
                              |  Abstract Network Model |
                              |                         |
                              +------------+------------+
                                           |
                                 +---------+---------+
                                 |                   |
                          +------V------+     +------V------+
                          |  Abstract   |     |  Inventory  |
                          |  Network    |     |    Models   |
                          |  Topology   |     |  (e.g., SAP |
                          |   Model     |     |   Network   |
                          |             |     |    Model)   |
                          +-----+-------+     +-------------+
                                |
                    +-----------+-----------+
                    |           |           |
               +----V----+ +----V----+ +----V----+
               |TE Topo  | |L3 Topo  | |L2 Topo  |
               |  Model  | |  Model  | |  Model  | ...
               +---------+ +---------+ +---------+

        Figure 5: Relationship of SAP Network Model to Other Models

   SAPs can be seen as customer-facing termination points (TPs) with
   specific service provisions.  However, one difference between SAPs
   and TPs is that links are terminated by a single TP (Section 4.4.6 of
   [RFC8345]) while an AC can be terminated by multiple SAPs.  Also, a
   SAP is neither a tunnel termination point (TTP) (Section 3.6 of
   [RFC8795]) nor a link.

   In the context of Software-Defined Networking (SDN) [RFC7149]
   [RFC7426], the SAP YANG data model can be used to exchange
   information between control elements, so as to support VPN service
   provision and resource management as discussed in [RFC9182] and
   [RFC9291].  Through this data model, the service orchestration layer
   can learn the available endpoints (i.e., SAPs) of interconnection
   resources of the underlying network.  The service orchestration layer
   can determine which interconnection endpoints to add to an L2VPN or
   L3VPN service.  With the help of other data models (e.g., the L3SM
   [RFC8299] or the L2SM [RFC8466]), hierarchical control elements can
   also assess the feasibility of end-to-end IP connectivity or L2VPN
   connectivity and therefore can derive the sequence of domains and the
   points of interconnection to use.

   Advanced interface-specific data nodes are not included in the SAP
   model.  The interface identifiers listed in the SAP model can be used
   as filters to set or get such data using device models (e.g.,
   [RFC7224]).

5.  SAP Module Tree Structure

   The SAP network model 'ietf-sap-ntw' builds on the 'ietf-network'
   module [RFC8345] by augmenting the nodes with SAPs.

   The structure of the 'ietf-sap-ntw' module is shown in Figure 6.

   module: ietf-sap-ntw
     augment /nw:networks/nw:network/nw:network-types:
       +--rw sap-network!
          +--rw service-type*   identityref
     augment /nw:networks/nw:network/nw:node:
       +--rw service* [service-type]
          +--rw service-type                   identityref
          +--rw sap* [sap-id]
             +--rw sap-id                      string
             +--rw description?                string
             +--rw parent-termination-point?   nt:tp-id
             +--rw attachment-interface?       string
             +--rw interface-type?             identityref
             +--rw encapsulation-type?         identityref
             +--rw role?                       identityref
             +--rw allows-child-saps?          boolean
             +--rw peer-sap-id*                string
             +--ro sap-status
             |  +--ro status?        identityref
             |  +--ro last-change?   yang:date-and-time
             +--rw service-status
                +--rw admin-status
                |  +--rw status?        identityref
                |  +--rw last-change?   yang:date-and-time
                +--ro oper-status
                   +--ro status?        identityref
                   +--ro last-change?   yang:date-and-time

                  Figure 6: SAP YANG Module Tree Structure

   A SAP network topology can be used for one or multiple service types
   ('service-type').  Examples of supported service types are as
   follows:

   *  L3VPN [RFC4364]

   *  Virtual Private LAN Service (VPLS) [RFC4761] [RFC4762]

   *  Virtual Private Wire Service (VPWS) [RFC8214]

   *  BGP MPLS-based Ethernet VPN [RFC7432]

   *  VPWS in Ethernet VPN [RFC8214]

   *  Provider Backbone Bridging combined with Ethernet VPN (PBB-EVPN)
      [RFC7623]

   *  VXLAN-based EVPN [RFC8365] ("VXLAN" stands for "Virtual eXtensible
      Local Area Network")

   *  Virtual Network [RFC8453]

   *  Enhanced VPN (VPN+) [ENHANCED-VPN]

   *  Network slice service [IETF-NETWORK-SLICES]

   *  SD-WAN [BGP-SDWAN-USAGE]

   *  Basic IP connectivity

   These service types build on the types that are already defined in
   [RFC9181] and additional types that are defined in this document.
   Other service types can be defined in future YANG modules (including
   future revisions of the YANG module defined in this document), if
   needed.

      |  Leveraging the service types defined in [RFC9181] is meant to
      |  ease the correlation between the SAP topology and the
      |  corresponding network models that are used to provision a
      |  specific service over a provider's network.

   Filters based on the service type can be used to access per-service
   SAP topology.  An example is depicted in Figure 10 in Appendix B.

   A node in the topology can support one or multiple service types
   ('service-type') among those listed under the 'sap-network'
   container.  A list of SAPs is then bound to each service type that is
   supported by a given node.  Each SAP is characterized as follows:

   'sap-id':  Includes an identifier that uniquely identifies a SAP
      within a node.

      The same SAP may appear under distinct service types.  In such a
      case, the same identifier is used for a shared SAP for each of
      these service types.

      SAPs that are associated with the interfaces that are directly
      hosting services, interfaces that are ready to host per-service
      sub-interfaces (but are not yet activated), or services that are
      already instantiated on sub-interfaces are listed as SAPs.  For
      illustration purposes, Figure 9 in Appendix B depicts how to
      indicate interfaces that are capable of hosting per-service sub-
      interfaces.

      For example, 'sap-id' may be the VPN network access identifier
      defined in Section 7.6 of [RFC9182].  An example that illustrates
      the use of this attribute during service creation is provided in
      Appendix D.

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

   'parent-termination-point':  Includes a reference to the parent
      termination point to which the SAP is bound.  As per Section 4.2
      of [RFC8345], a termination point terminates a link in a node.  A
      termination point can be a physical port, an interface, etc.

      The referenced parent termination point is expected to be a
      customer-facing termination point, not a core-facing termination
      point.

      For example, this attribute is used to associate an interface with
      its sub-interfaces, as all these interfaces may be listed under
      the SAPs of a node.  It is also used to link a SAP with the
      physical topology.

      For example, this data node can be used to map the IETF Network
      Slice endpoints [IETF-NETWORK-SLICES] to the service/tunnel/path
      endpoints in the underlay network.

   'attachment-interface':  Indicates a reference to the interface to
      which the SAP is bound.  The same interface may host multiple
      services.

      Whether the attachment identifier echoes the content of the
      attachment interface is deployment specific.

      For example, this reference may be any of the identifiers ('l2-
      termination-point', 'local-bridge-reference', 'bearer-reference',
      or 'lag-interface-id') defined in Section 7.6.1 of [RFC9182] or
      'l3-termination-point' as defined in Section 7.6.2 of [RFC9182].
      The controller is responsible for ensuring that consistent
      references are used in the SAP and underlying device models or any
      other device inventory mechanism.

   'interface-type':  Indicates whether a SAP is bound to a physical
      port, a loopback interface, a Link Aggregation Group (LAG)
      interface [IEEE802.1AX], an Integrated Routing and Bridging (IRB)
      interface (e.g., [RFC9135]), a local bridge reference, etc.

      The mapping to the detailed interface types as per [RFC7224] is
      maintained by the controller.  That mapping is used, for example,
      when the controller translates this SAP network model into device
      models (Section 4.4 of [RFC8969]).

   'encapsulation-type':  Indicates the encapsulation type for the
      interface indicated in the 'attachment-interface' attribute.  The
      types are taken from [RFC9181].

      This data node can be used, for example, to decide whether an
      existing SAP can be (re)used to host a service or if a new sub-
      interface has to be instantiated.

   'role':  Specifies the role of a SAP (e.g., a UNI or NNI).

      A SAP inherits the role of its parent interface ('parent-
      termination-point').

   'allows-child-saps':  When set to 'true', indicates that the
      attachment interface for this SAP is capable of hosting per-
      service sub-interfaces.

      Whether a service can be directly attached to the parent SAP in
      addition to child SAPs depends on the service.

   'peer-sap-id':  Includes references to the remote endpoints of an AC.
      This identifier may or may not be the same as the SAP identifier
      used in the peer's configuration.  Note that the use of identical
      identifiers eases the correlation between a peer's service request
      and a local SAP.

      Examples of such a reference are a site identifier (Section 6.3 of
      [RFC8299]), a Service Demarcation Point (SDP) identifier
      (Section 3.2 ("Core Terminology") of [IETF-NETWORK-SLICES]), and
      the IP address of a peer Autonomous System Border Router (ASBR).

   'sap-status':  Indicates the operational status of a SAP.  Values are
      taken from the values defined in [RFC9181].

      When both a sub-interface and its parent interface are present but
      the parent interface is disabled, the status of the parent
      interface takes precedence over the status indicated for the sub-
      interface.

   'service-status':  Indicates the administrative and operational
      status of the service for a given SAP.  This information is
      particularly useful when many services are provisioned for the
      same SAP but only a subset of these services is activated.  As
      such, the administrative 'service-status' MUST NOT be influenced
      by the value of the operational 'sap-status'.

      The service 'oper-status' reflects the operational status of the
      service only as observed at a specific SAP, not the overall
      network-level status of the service connecting many SAPs.  The
      network-level service status can be retrieved using specific
      network models, e.g., those listed in Section 7.3 of [RFC9182] or
      Section 7.3 of [RFC9291].

      In order to assess the service delivery status for a given SAP, it
      is recommended to check both the administrative and operational
      service status ('service-status') in addition to the 'sap-status'.
      In doing so, a network controller (or operator) can detect
      anomalies.  For example, if a service is administratively enabled
      for a SAP and the 'sap-status' of that SAP is reported as being
      down, the service 'oper-status' is also expected to be down.
      Retrieving a distinct service operational status under these
      conditions can be used as a trigger to detect an anomaly.
      Likewise, administrative status and operational status can be
      compared to detect service-specific SAP activation anomalies.  For
      example, a service that is administratively declared as inactive
      for a SAP but reported as operationally active for that SAP is an
      indication that some service provision actions are needed to align
      the observed service status with the expected service status.

6.  SAP YANG Module

   This module imports types from [RFC6991], [RFC8345], and [RFC9181].

   The 'sap-entry' and 'sap-list' are defined as groupings for the reuse
   of these nodes in service-specific YANG modules.

   <CODE BEGINS> file "ietf-sap-ntw@2023-06-20.yang"
   module ietf-sap-ntw {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-sap-ntw";
     prefix sap;

     import ietf-network-topology {
       prefix nt;
       reference
         "RFC 8345: A YANG Data Model for Network
                    Topologies, Section 6.2";
     }
     import ietf-network {
       prefix nw;
       reference
         "RFC 8345: A YANG Data Model for Network
                    Topologies, Section 6.1";
     }
     import ietf-vpn-common {
       prefix vpn-common;
       reference
         "RFC 9181: A Common YANG Data Model for Layer 2 and Layer 3
                    VPNs";
     }
     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types, Section 3";
     }

     organization
       "IETF OPSA (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:   Oscar Gonzalez de Dios
                  <mailto:oscar.gonzalezdedios@telefonica.com>

        Author:   Samier Barguil
                  <mailto:samier.barguil_giraldo@nokia.com>

        Author:   Qin Wu
                  <mailto:bill.wu@huawei.com>

        Author:   Victor Lopez
                  <mailto:victor.lopez@nokia.com>";
     description
       "This YANG module defines a model for representing, managing,
        and controlling the Service Attachment Points (SAPs) in the
        network topology.

        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 9408; see the
        RFC itself for full legal notices.";

     revision 2023-06-20 {
       description
         "Initial version.";
       reference
         "RFC 9408: A YANG Network Data Model for Service Attachment
                    Points (SAPs)";
     }

     identity virtual-network {
       base vpn-common:service-type;
       description
         "Virtual network.  Refers to a logical network instance
          that is built over a physical network.";
       reference
         "RFC 8453: Framework for Abstraction and Control of TE
                    Networks (ACTN)";
     }

     identity enhanced-vpn {
       base vpn-common:service-type;
       description
         "Enhanced VPN (VPN+).  VPN+ is an approach that is
          based on existing VPN and Traffic Engineering (TE)
          technologies but adds characteristics that specific
          services require over and above conventional VPNs.";
       reference
         "draft-ietf-teas-enhanced-vpn:
            A Framework for Enhanced Virtual Private Network
            (VPN+)";
     }

     identity network-slice {
       base vpn-common:service-type;
       description
         "IETF Network Slice.  An IETF Network Slice
          is a logical network topology connecting a number of
          endpoints using a set of shared or dedicated network
          resources that are used to satisfy specific service
          objectives.";
       reference
         "draft-ietf-teas-ietf-network-slices:
            A Framework for IETF Network Slices";
     }

     identity sdwan {
       base vpn-common:service-type;
       description
         "PE-based Software-Defined Wide-Area Network (SD-WAN).";
       reference
         "draft-ietf-bess-bgp-sdwan-usage:
            BGP Usage for SD-WAN Overlay Networks";
     }

     identity basic-connectivity {
       base vpn-common:service-type;
       description
         "Basic IP connectivity.  This is, for example, a plain
          form of connectivity offered to enterprises over a
          dedicated or shared MPLS infrastructure.";
     }

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

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

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

     identity interface-type {
       description
         "Base identity for the interface type.";
     }

     identity phy {
       base interface-type;
       description
         "Physical port.";
     }

     identity loopback {
       base interface-type;
       description
         "Loopback interface.";
     }

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

     identity irb {
       base interface-type;
       description
         "Integrated Routing and Bridging (IRB) interface.  An IRB
          interface typically connects an IP Virtual Routing and
          Forwarding (IP-VRF) entity to a bridge domain.";
     }

     identity local-bridge {
       base interface-type;
       description
         "A local bridge reference to accommodate (for example)
          implementations that require internal bridging.
          When such a type is used, a reference to a local
          bridge domain is used to identify the interface.";
     }

     identity logical {
       base interface-type;
       description
         "Refers to a logical sub-interface that is typically
          used to bind a service.  This type is used only
          if none of the other more specific types (i.e.,
          'loopback', 'lag', 'irb', or 'local-bridge') can be used.";
     }

     grouping sap-entry {
       description
         "Service Attachment Point (SAP) entry information.";
       leaf sap-id {
         type string;
         description
           "Indicates an identifier that uniquely identifies
            a SAP.";
       }
       leaf description {
         type string;
         description
           "A textual description of the SAP.";
       }
       leaf parent-termination-point {
         type nt:tp-id;
         description
           "Indicates the parent termination point to
            which the SAP is attached.  A termination
            point can be a physical port, an interface, etc.";
       }
       leaf attachment-interface {
         type string;
         description
           "Indicates the interface to which the SAP is bound.";
       }
       leaf interface-type {
         type identityref {
           base interface-type;
         }
         description
           "The type of the interface to which the SAP is bound.";
       }
       leaf encapsulation-type {
         type identityref {
           base vpn-common:encapsulation-type;
         }
         description
           "Encapsulation type of the interface to which the
            SAP is bound.";
       }
       leaf role {
         type identityref {
           base interface-role;
         }
         description
           "Indicates the role of a SAP.";
       }
       leaf allows-child-saps {
         type boolean;
         description
           "Indicates whether the attachment interface of this
            SAP is capable of hosting per-service sub-interfaces.";
       }
       leaf-list peer-sap-id {
         type string;
         description
           "Indicates an identifier of the peer's termination
            identifier (e.g., a Customer Edge (CE)).  This
            information can be used for correlation purposes,
            such as identifying the SAP that is attached to
            an endpoint that is provided in a service request.";
       }
     }

     grouping sap-list {
       description
         "SAP information.";
       list sap {
         key "sap-id";
         description
           "The SAPs are an abstraction of the points to which
            network services such as L3VPNs, L2VPNs, or network
            slices can be attached.";
         uses sap-entry;
         container sap-status {
           config false;
           description
             "Indicates the operational status of the SAP,
              independent of any service provisioned over it.";

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

     augment "/nw:networks/nw:network/nw:network-types" {
       description
         "Introduces a new network type for a SAP network.";
       container sap-network {
         presence "Indicates the SAP network type.";
         description
           "The presence of the container node indicates the
            SAP network type.";
         leaf-list service-type {
           type identityref {
             base vpn-common:service-type;
           }
           description
             "Indicates the set of supported service types.";
         }
       }
     }

     augment "/nw:networks/nw:network/nw:node" {
       when '../nw:network-types/sap:sap-network' {
         description
           "Augmentation parameters apply only for SAP
            networks.";
       }
       description
         "SAP parameters for the node level.";
       list service {
         key "service-type";
         description
           "A list of supported service types for the node.";
         leaf service-type {
           type identityref {
             base vpn-common:service-type;
           }
           description
             "Indicates a service type.";
         }
         uses sap-list;
       }
     }
   }
   <CODE ENDS>

7.  IANA Considerations

   This document registers the following namespace URI in the "ns"
   subregistry within the "IETF XML Registry" [RFC3688]:

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

   This document registers the following YANG module in the "YANG Module
   Names" subregistry [RFC6020] within the "YANG Parameters" registry:

   Name:  ietf-sap-ntw
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-sap-ntw
   Maintained by IANA?  N
   Prefix:  sap
   Reference:  RFC 9408

8.  Security Considerations

   The YANG module specified in this document defines a 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)
   to these data nodes without proper protection can have a negative
   effect on network operations.  These are the subtrees and data nodes
   and their sensitivity/vulnerability:

   /nw:networks/nw:network/nw:node/sap:service/sap:sap
      This subtree specifies the configurations of the nodes in a SAP
      network model.  Unexpected changes to this subtree (e.g.,
      associating a SAP with another parent termination point) could
      lead to service disruption and/or network misbehavior.  Such
      network misbehavior results mainly from a network configuration
      that is inconsistent with the intended behavior as defined by the
      operator (e.g., Section 4.2.1 of [RFC8969]).

   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:

   /nw:networks/nw:network/nw:node/sap:service/sap:sap
      Unauthorized access to this subtree can disclose the operational
      state information of the nodes in a SAP network model (e.g., can
      disclose the identity of a customer 'peer-sap-id').

9.  References

9.1.  Normative References

   [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/info/rfc2119>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/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/info/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/info/rfc6241>.

   [RFC6242]  Wasserman, M., "Using the NETCONF Protocol over Secure
              Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
              <https://www.rfc-editor.org/info/rfc6242>.

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

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

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

   [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/info/rfc8174>.

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

   [RFC8345]  Clemm, A., Medved, J., Varga, R., Bahadur, N.,
              Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
              Network Topologies", RFC 8345, DOI 10.17487/RFC8345, March
              2018, <https://www.rfc-editor.org/info/rfc8345>.

   [RFC8346]  Clemm, A., Medved, J., Varga, R., Liu, X.,
              Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
              for Layer 3 Topologies", RFC 8346, DOI 10.17487/RFC8346,
              March 2018, <https://www.rfc-editor.org/info/rfc8346>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8795]  Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Gonzalez de Dios, "YANG Data Model for Traffic
              Engineering (TE) Topologies", RFC 8795,
              DOI 10.17487/RFC8795, August 2020,
              <https://www.rfc-editor.org/info/rfc8795>.

   [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/info/rfc9181>.

9.2.  Informative References

   [BGP-SDWAN-USAGE]
              Dunbar, L., Guichard, J., Sajassi, A., Drake, J., Najem,
              B., Banerjee, A., and D. Carrel, "BGP Usage for SD-WAN
              Overlay Networks", Work in Progress, Internet-Draft,
              draft-ietf-bess-bgp-sdwan-usage-09, 7 April 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-bess-
              bgp-sdwan-usage-09>.

   [ENHANCED-VPN]
              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Network (VPN+)",
              Work in Progress, Internet-Draft, draft-ietf-teas-
              enhanced-vpn-12, 23 January 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              enhanced-vpn-12>.

   [IEEE802.1AX]
              IEEE, "IEEE Standard for Local and Metropolitan Area
              Networks--Link Aggregation", IEEE Std 802.1AX-2020,
              DOI 10.1109/IEEESTD.2020.9105034, 2020,
              <https://doi.org/10.1109/IEEESTD.2020.9105034>.

   [IETF-NETWORK-SLICES]
              Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S.,
              Makhijani, K., Contreras, L.M., and J. Tantsura, "A
              Framework for IETF Network Slices", Work in Progress,
              Internet-Draft, draft-ietf-teas-ietf-network-slices-19, 21
              January 2023, <https://datatracker.ietf.org/doc/html/
              draft-ietf-teas-ietf-network-slices-19>.

   [MEF17]    The Metro Ethernet Forum, "Technical Specification MEF 17,
              Service OAM Requirements & Framework - Phase 1", April
              2007, <https://www.mef.net/wp-content/uploads/2015/04/MEF-
              17.pdf>.

   [MEF6]     The Metro Ethernet Forum, "Technical Specification MEF 6,
              Ethernet Services Definitions - Phase I", June 2004,
              <https://www.mef.net/Assets/Technical_Specifications/PDF/
              MEF_6.pdf>.

   [RFC4026]  Andersson, L. and T. Madsen, "Provider Provisioned Virtual
              Private Network (VPN) Terminology", RFC 4026,
              DOI 10.17487/RFC4026, March 2005,
              <https://www.rfc-editor.org/info/rfc4026>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.

   [RFC4761]  Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007,
              <https://www.rfc-editor.org/info/rfc4761>.

   [RFC4762]  Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
              <https://www.rfc-editor.org/info/rfc4762>.

   [RFC6004]  Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Support
              for Metro Ethernet Forum and G.8011 Ethernet Service
              Switching", RFC 6004, DOI 10.17487/RFC6004, October 2010,
              <https://www.rfc-editor.org/info/rfc6004>.

   [RFC6215]  Bocci, M., Levrau, L., and D. Frost, "MPLS Transport
              Profile User-to-Network and Network-to-Network
              Interfaces", RFC 6215, DOI 10.17487/RFC6215, April 2011,
              <https://www.rfc-editor.org/info/rfc6215>.

   [RFC7149]  Boucadair, M. and C. Jacquenet, "Software-Defined
              Networking: A Perspective from within a Service Provider
              Environment", RFC 7149, DOI 10.17487/RFC7149, March 2014,
              <https://www.rfc-editor.org/info/rfc7149>.

   [RFC7224]  Bjorklund, M., "IANA Interface Type YANG Module",
              RFC 7224, DOI 10.17487/RFC7224, May 2014,
              <https://www.rfc-editor.org/info/rfc7224>.

   [RFC7426]  Haleplidis, E., Ed., Pentikousis, K., Ed., Denazis, S.,
              Hadi Salim, J., Meyer, D., and O. Koufopavlou, "Software-
              Defined Networking (SDN): Layers and Architecture
              Terminology", RFC 7426, DOI 10.17487/RFC7426, January
              2015, <https://www.rfc-editor.org/info/rfc7426>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7623]  Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W.
              Henderickx, "Provider Backbone Bridging Combined with
              Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623,
              September 2015, <https://www.rfc-editor.org/info/rfc7623>.

   [RFC7951]  Lhotka, L., "JSON Encoding of Data Modeled with YANG",
              RFC 7951, DOI 10.17487/RFC7951, August 2016,
              <https://www.rfc-editor.org/info/rfc7951>.

   [RFC8214]  Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
              Rabadan, "Virtual Private Wire Service Support in Ethernet
              VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
              <https://www.rfc-editor.org/info/rfc8214>.

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

   [RFC8309]  Wu, Q., Liu, W., and A. Farrel, "Service Models
              Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018,
              <https://www.rfc-editor.org/info/rfc8309>.

   [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/info/rfc8340>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8365]  Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
              Uttaro, J., and W. Henderickx, "A Network Virtualization
              Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365,
              DOI 10.17487/RFC8365, March 2018,
              <https://www.rfc-editor.org/info/rfc8365>.

   [RFC8453]  Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
              Abstraction and Control of TE Networks (ACTN)", RFC 8453,
              DOI 10.17487/RFC8453, August 2018,
              <https://www.rfc-editor.org/info/rfc8453>.

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

   [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/info/rfc8969>.

   [RFC9135]  Sajassi, A., Salam, S., Thoria, S., Drake, J., and J.
              Rabadan, "Integrated Routing and Bridging in Ethernet VPN
              (EVPN)", RFC 9135, DOI 10.17487/RFC9135, October 2021,
              <https://www.rfc-editor.org/info/rfc9135>.

   [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/info/rfc9182>.

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

Appendix A.  A Simplified SAP Network Example

   An example of a SAP topology that is reported by a network controller
   is depicted in Figure 7.  This example echoes the topology shown in
   Figure 4.  Only a minimum information set is provided for each SAP.
   Particularly, 'parent-termination-point', 'attachment-interface',
   'interface-type', 'encapsulation-type', and 'role' are not shown in
   the example.  SAPs that are capable of hosting a service but are not
   yet activated are identified by 'sap-status/status' set to 'ietf-vpn-
   common:op-down' and 'service-status/admin-status/status' set to
   'ietf-vpn-common:admin-down'.  SAPs that are enabled to deliver a
   service are identified by 'service-status/admin-status/status' set to
   'ietf-vpn-common:admin-up' and 'service-status/oper-status/status'
   set to 'ietf-vpn-common:op-up'.  Note that none of the anomalies
   discussed in Section 5 are detected for these SAPs.  The message body
   depicted in the figures below is encoded following the JSON encoding
   of YANG-modeled data as per [RFC7951].

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-types": {
             "ietf-sap-ntw:sap-network": {
               "service-type": [
                 "ietf-vpn-common:l3vpn",
                 "ietf-vpn-common:vpls"
               ]
             }
           },
           "network-id": "example:an-id",
           "node": [
             {
               "node-id": "example:pe1",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#11",
                       "peer-sap-id": ["ce-1"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#12",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#13",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#14",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     }
                   ]
                 }
               ]
             },
             {
               "node-id": "example:pe2",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#21",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#22",
                       "peer-sap-id": ["ce-2"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     }
                   ]
                 }
               ]
             },
             {
               "node-id": "example:pe3",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#31",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#32",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#33",
                       "peer-sap-id": ["ce-3"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     }
                   ]
                 }
               ]
             },
             {
               "node-id": "example:pe4",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#41",
                       "peer-sap-id": ["ce-3"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#42",
                       "peer-sap-id": ["ce-4"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#43",
                       "sap-status": {
                         "status": "ietf-vpn-common:op-down"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-down"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#44",
                       "peer-sap-id": ["ce-5"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     }
                   ]
                 }
               ]
             }
           ]
         }
       ]
     }
   }

                 Figure 7: A Simplified SAP Network Example

Appendix B.  A Simple Example of the SAP Network Model: Node Filter

   In the example shown in Figure 8, PE1 (with a "node-id" set to
   "example:pe1", as shown in Figure 7) has two physical interfaces
   "GE0/6/1" and "GE0/6/4".  Two sub-interfaces "GE0/6/4.1" and
   "GE0/6/4.2" are associated with the physical interface "GE0/6/4".
   Let us consider that four SAPs are exposed to the service
   orchestrator and mapped to these physical interfaces and sub-
   interfaces.

                  .-------------------------.
                  |                 GE0/6/4 |
                  | PE1                .----+----.
                  |                    |sap#2    |GE0/6/4.1
                  |                    |      .--+--.
                  |                    |      |sap#3|
                  |                    |      '--+--'
                  |                    |         |GE0/6/4.2
                  |                    |      .--+--.
                  |                    |      |sap#4|
                  |                    |      '--+--'
                  |                    |         |
                  |                    +----+----+
                  |                         |
                  |                  GE0/6/1|
                  |                    .----+----.
                  |                    |sap#1    |
                  |                    '----+----'
                  |                         |
                  '-------------------------'

      Figure 8: An Example of a PE and Its Physical/Logical Interfaces

   Let us assume that no service is enabled yet for the SAP associated
   with the physical interface "GE0/6/1".  Also, let us assume that, for
   the SAPs that are associated with the physical interface "GE0/6/4",
   VPLS and L3VPN services are activated on the two sub-interfaces
   "GE0/6/4.1" and "GE0/6/4.2", respectively.  Both "sap#1" and "sap#2"
   are tagged as being capable of hosting per-service sub-interfaces
   ('allows-child-saps' is set to 'true').

   For example, a service orchestrator can query what services are
   provided on which SAPs of PE1 from the network controller by sending
   a RESTCONF GET request.  Figure 9 shows an example of the body of the
   RESTCONF response that is received from the network controller.

   {
     "ietf-sap-ntw:service": [
       {
         "service-type": "ietf-vpn-common:l3vpn",
         "sap": [
           {
             "sap-id": "sap#1",
             "description": "Ready to host SAPs",
             "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#2",
             "description": "Ready to host SAPs",
             "attachment-interface": "GE0/6/4",
             "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#3",
             "description": "A first SAP description",
             "parent-termination-point": "GE0/6/4",
             "attachment-interface": "GE0/6/4.1",
             "interface-type": "ietf-sap-ntw:logical",
             "encapsulation-type": "ietf-vpn-common:vlan-type",
             "sap-status": {
               "status": "ietf-vpn-common:op-up"
             },
             "service-status": {
               "admin-status": {
                 "status": "ietf-vpn-common:admin-up"
               },
               "oper-status": {
                 "status": "ietf-vpn-common:op-up"
               }
             }
           }
         ]
       },
       {
         "service-type": "ietf-vpn-common:vpls",
         "sap": [
           {
             "sap-id": "sap#1",
             "description": "Ready to host SAPs",
             "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#2",
             "description": "Ready to host SAPs",
             "attachment-interface": "GE0/6/4",
             "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#4",
             "description": "Another description",
             "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"
             },
             "service-status": {
               "admin-status": {
                 "status": "ietf-vpn-common:admin-up"
               },
               "oper-status": {
                 "status": "ietf-vpn-common:op-up"
               }
             }
           }
         ]
       }
     ]
   }

      Figure 9: An Example of a Response Body to a Request with a Node
                                   Filter

   Figure 10 shows an example of the response message body that is
   received from the network controller if the request includes a filter
   on the service type for a particular node:

   {
     "ietf-sap-ntw:service": [
       {
         "service-type": "ietf-vpn-common:l3vpn",
         "sap": [
           {
             "sap-id": "sap#1",
             "description": "Ready to host SAPs",
             "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#2",
             "description": "Ready to host SAPs",
             "attachment-interface": "GE0/6/4",
             "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#3",
             "description": "A first SAP description",
             "parent-termination-point": "GE0/6/4",
             "attachment-interface": "GE0/6/4.1",
             "interface-type": "ietf-sap-ntw:logical",
             "encapsulation-type": "ietf-vpn-common:vlan-type",
             "sap-status": {
               "status": "ietf-vpn-common:op-up"
             },
             "service-status": {
               "admin-status": {
                 "status": "ietf-vpn-common:admin-up"
               },
               "oper-status": {
                 "status": "ietf-vpn-common:op-up"
               }
             }
           }
         ]
       }
     ]
   }

        Figure 10: An Example of a Response Body to a Request with a
                               Service Filter

Appendix C.  An Example of an NNI SAP: Inter-AS VPN Option A

   Section 10 of [RFC4364] discusses several options to extend a VPN
   service beyond the scope of a single Autonomous System (AS).  For
   illustration purposes, this section focuses on the so-called "Option
   A", but similar examples can be considered for other options.

   In this option, an AS Border Router (ASBR) of an AS is directly
   connected to an ASBR of a neighboring AS.  These two ASBRs are
   connected by multiple physical or logical interfaces.  Also, at least
   one sub-interface is maintained by these ASBRs for each of the VPNs
   that require their routes to be passed from one AS to the other AS.
   Each ASBR behaves as a PE and treats the other as if it were a CE.

   Figure 11 shows a simplified (excerpt) topology of two ASes A and B
   with a focus on the interconnection links between these two ASes.

    .--------------------.                      .--------------------.
    |                    |                      |                    |
    |              A  .--+--.                .--+--.  A              |
    |              S  |     +================+     |  S              |
    |              B  | (VRF1)----(VPN1)----(VRF1) |  B              |
    |              R  |     |                |     |  R              |
    |                 | (VRF2)----(VPN2)----(VRF2) |                 |
    |              a  |     +================+     |  b              |
    |              1  '--+--'                '--+--'  1              |
    |     AS A           |                      |         AS B       |
    |              A  .--+--.                .--+--.  A              |
    |              S  |     +================+     |  S              |
    |              B  | (VRF1)----(VPN1)----(VRF1) |  B              |
    |              R  |     |                |     |  R              |
    |                 | (VRF2)----(VPN2)----(VRF2) |                 |
    |              a  |     +================+     |  b              |
    |              2  '--+--'                '--+--'  2              |
    |                    |                      |                    |
    '--------------------'                      '--------------------'

            Figure 11: An Example of an Inter-AS VPN (Option A)

   Figure 12 shows an example of a message body that is received from
   the network controller of AS A (with a focus on the NNIs shown in
   Figure 11).

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-types": {
             "ietf-sap-ntw:sap-network": {
               "service-type": [
                 "ietf-vpn-common:l3vpn"
               ]
             }
           },
           "network-id": "example:an-id",
           "node": [
             {
               "node-id": "example:asbr-a1",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#11",
                       "description": "parent inter-as link#1",
                       "role": "ietf-sap-ntw:nni",
                       "allows-child-saps": true,
                       "peer-sap-id": ["asbr-b1"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       }
                     },
                     {
                       "sap-id": "sap#12",
                       "description": "parent inter-as link#2",
                       "role": "ietf-sap-ntw:nni",
                       "allows-child-saps": true,
                       "peer-sap-id": ["asbr-b1"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       }
                     },
                     {
                       "sap-id": "sap#13",
                       "description": "vpn1",
                       "role": "ietf-sap-ntw:nni",
                       "peer-sap-id": ["asbr-b1"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#14",
                       "description": "vpn2",
                       "role": "ietf-sap-ntw:nni",
                       "peer-sap-id": ["asbr-b1"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     }
                   ]
                 }
               ]
             },
             {
               "node-id": "example:asbr-a2",
               "ietf-sap-ntw:service": [
                 {
                   "service-type": "ietf-vpn-common:l3vpn",
                   "sap": [
                     {
                       "sap-id": "sap#11",
                       "description": "parent inter-as link#1",
                       "role": "ietf-sap-ntw:nni",
                       "allows-child-saps": true,
                       "peer-sap-id": ["asbr-b2"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       }
                     },
                     {
                       "sap-id": "sap#12",
                       "description": "parent inter-as link#2",
                       "role": "ietf-sap-ntw:nni",
                       "allows-child-saps": true,
                       "peer-sap-id": ["asbr-b2"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       }
                     },
                     {
                       "sap-id": "sap#21",
                       "description": "vpn1",
                       "role": "ietf-sap-ntw:nni",
                       "peer-sap-id": ["asbr-b2"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     },
                     {
                       "sap-id": "sap#22",
                       "description": "vpn2",
                       "role": "ietf-sap-ntw:nni",
                       "peer-sap-id": ["asbr-b2"],
                       "sap-status": {
                         "status": "ietf-vpn-common:op-up"
                       },
                       "service-status": {
                         "admin-status": {
                           "status": "ietf-vpn-common:admin-up"
                         },
                         "oper-status": {
                           "status": "ietf-vpn-common:op-up"
                         }
                       }
                     }
                   ]
                 }
               ]
             }
           ]
         }
       ]
     }
   }

               Figure 12: An Example of SAP Usage for an NNI

Appendix D.  Examples of Using the SAP Network Model in Service Creation

   This section describes examples that illustrate the use of the SAP
   model for service creation purposes.

   An example of a SAP topology is presented in Figure 7.  This example
   includes four PEs with their SAPs, as well as the customer
   information.

   Let us assume that an operator wants to create an L3VPN service
   between two PEs (PE3 and PE4) that are servicing two CEs (CE6 and
   CE7).  To that aim, the operator would query the SAP topology and
   would obtain a response similar to what is depicted in Figure 7.
   That response indicates that the SAPs having "sap#31" and "sap#43" as
   attachment identifiers do not have any installed services.  This is
   particularly inferred from (1) the administrative 'service-status'
   that is set to 'ietf-vpn-common:admin-down' for all the services that
   are supported by these two SAPs and (2) the absence of the anomalies
   discussed in Section 5.  Note that none of the anomalies discussed in
   Section 5 are detected.  Once the "free" SAPs are identified, the
   'interface-type' and 'encapsulation-type' are checked to see if the
   requested L3VPN service is compatible with the SAP characteristics.
   If they are compatible, the 'attachment-id' value can be used as the
   VPN network access identifier in an L3NM "create" query.

   A similar process can be followed for creating the so-called "Inter-
   AS VPN Option A" services.  Unlike the previous example, let us
   assume that an operator wants to create an L3VPN service between two
   PEs (PE3 and PE4) but these PEs are not in the same AS: PE3 belongs
   to AS A while PE4 belongs to AS B.  The NNIs between these ASes are
   represented in Figure 11.  The operator of AS A would query, via the
   controller of its AS, the SAP topology and would obtain not only the
   information that is depicted in Figure 7 but also the information
   shown in Figure 12 representing the NNIs.  The operator would create
   the service in the AS A between PE3 and a free, compatible SAP in the
   ASBR A1.  The same procedure is followed by the operator of AS B to
   create the service in the AS B between a free, compatible SAP in the
   ASBR B1 and PE4.  The services can be provisioned in each of these
   ASes using the L3NM.

   Let us now assume that, instead of the L3VPN service, the operator
   wants to set up an L2VPN service.  If the 'interface-type' is a
   physical port, a new logical SAP can be created using the SAP model
   to cope with the service's needs (e.g., the 'encapsulation-type'
   attribute can be set to 'ietf-vpn-common:vlan-type').  Once the
   logical SAP is created, the 'attachment-id' of the new SAP is used to
   create an L2NM instance (Section 7.6 of [RFC9291]).

Acknowledgements

   Thanks to Adrian Farrel, Daniel King, Dhruv Dhody, Benoit Claise, Bo
   Wu, Erez Segev, Raul Arco, Joe Clarke, Riyas Valiyapalathingal, Tom
   Petch, Olga Havel, and Richard Roberts for their comments.

   Thanks to Martin Björklund for the YANG Doctors review, Menachem
   Dodge for the opsdir review, Mach Chen for the rtgdir review, Linda
   Dunbar for the genart review, and Ivaylo Petrov for the secdir
   review.

   Special thanks to Adrian Farrel for the Shepherd review and Rob
   Wilton for the careful AD review.

   Thanks to Lars Eggert, Roman Danyliw, and Zaheduzzaman Sarker for
   their comments during the IESG review.

Authors' Addresses

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


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


   Samier Barguil
   Nokia
   Madrid
   Spain
   Email: samier.barguil_giraldo@nokia.com


   Qin Wu
   Huawei
   Yuhua District
   101 Software Avenue
   Nanjing
   Jiangsu, 210012
   China
   Email: bill.wu@huawei.com


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