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A YANG Data Model for Virtual Network (VN) Operations
draft-ietf-teas-actn-vn-yang-29

Document Type Active Internet-Draft (teas WG)
Authors Young Lee , Dhruv Dhody , Daniele Ceccarelli , Igor Bryskin , Bin Yeong Yoon
Last updated 2024-07-02 (Latest revision 2024-06-22)
Replaces draft-lee-teas-actn-vn-yang
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draft-ietf-teas-actn-vn-yang-29
TEAS Working Group                                           Y. Lee, Ed.
Internet-Draft                                       Samsung Electronics
Intended status: Standards Track                           D. Dhody, Ed.
Expires: 24 December 2024                                         Huawei
                                                           D. Ceccarelli
                                                                   Cisco
                                                              I. Bryskin
                                                              Individual
                                                                 B. Yoon
                                                                    ETRI
                                                            22 June 2024

         A YANG Data Model for Virtual Network (VN) Operations
                    draft-ietf-teas-actn-vn-yang-29

Abstract

   A Virtual Network (VN) is a network provided by a service provider to
   a customer for the customer to use in any way it wants as though it
   was a physical network.  This document provides a YANG data model
   generally applicable to any mode of VN operations.  This includes VN
   operations as per the Abstraction and Control of TE Networks (ACTN)
   framework.

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
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   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 24 December 2024.

Copyright Notice

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

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Tree Diagram  . . . . . . . . . . . . . . . . . . . . . .   5
     1.3.  Prefixes in Data Node Names . . . . . . . . . . . . . . .   5
   2.  Use-case of VN YANG Model in the ACTN context . . . . . . . .   5
     2.1.  Type 1 VN . . . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Type 2 VN . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  High-Level Control Flows with Examples  . . . . . . . . . . .   8
     3.1.  Type 1 VN Illustration  . . . . . . . . . . . . . . . . .   8
     3.2.  Type 2 VN Illustration  . . . . . . . . . . . . . . . . .   9
       3.2.1.  VN and AP Usage . . . . . . . . . . . . . . . . . . .  12
   4.  VN Model Usage  . . . . . . . . . . . . . . . . . . . . . . .  12
     4.1.  Customer view of VN . . . . . . . . . . . . . . . . . . .  12
     4.2.  Auto-creation of VN by MDSC . . . . . . . . . . . . . . .  12
     4.3.  Innovative Services . . . . . . . . . . . . . . . . . . .  12
       4.3.1.  VN Compute  . . . . . . . . . . . . . . . . . . . . .  13
       4.3.2.  Multi-sources and Multi-destinations  . . . . . . . .  17
     4.4.  Others  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     4.5.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .  19
   5.  VN YANG Model (Tree Structure)  . . . . . . . . . . . . . . .  19
   6.  VN YANG Model . . . . . . . . . . . . . . . . . . . . . . . .  22
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  34
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  36
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  36
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  37
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  37
     10.2.  Informative References . . . . . . . . . . . . . . . . .  38
   Appendix A.  Performance Constraints  . . . . . . . . . . . . . .  40
   Appendix B.  JSON Example . . . . . . . . . . . . . . . . . . . .  40
     B.1.  VN JSON . . . . . . . . . . . . . . . . . . . . . . . . .  40
     B.2.  TE-topology JSON  . . . . . . . . . . . . . . . . . . . .  47
   Appendix C.  Contributors Addresses . . . . . . . . . . . . . . .  54
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  55

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1.  Introduction

   Abstraction and Control of Traffic Engineered (TE) Networks (ACTN)
   describes a set of management and control functions used to operate
   one or more TE networks to construct a Virtual Network (VN).  A VN is
   represented to customers and is built from the abstractions of the
   underlying TE networks [RFC8453].  This document provides a YANG
   [RFC7950] data model generally applicable to any mode of VN
   operation.  ACTN is the primary example of the usage of the VN YANG
   model but not limited to it.

   The VN model defined in this document is applicable in a generic
   sense as an independent model in and of itself.  The VN model defined
   in this document can also work together with other customer service
   models such as the Layer Three Virtual Private Network Service Model
   (L3SM) [RFC8299], the Layer Two Virtual Private Network Service Model
   (L2SM) [RFC8466] and the Layer One Connectivity Service Model (L1CSM)
   [I-D.ietf-ccamp-l1csm-yang] to provide a complete life-cycle service
   management and operations.

   The YANG model discussed in this document basically provides the
   following:

   *  Characteristics of Access Points (APs) that describe customer's
      endpoint characteristics;

   *  Characteristics of Virtual Network Access Points (VNAP) that
      describe how an AP is partitioned for multiple VNs sharing the AP
      and its reference to a Link Termination Point (LTP) of the
      Provider Edge (PE) Node;

   *  Characteristics of Virtual Networks (VNs) that describe the
      customer's VN in terms of multiple VN Members comprising a VN,
      multi-source and/or multi-destination characteristics of the VN
      Member, the VN's reference to TE-topology's Abstract Node;

   An abstract TE topology is a topology that contains abstract
   topological elements (nodes, links) created and customised based on
   customer's preference [RFC8795].  The actual VN instantiation and
   computation is performed with Connectivity Matrices of the TE-
   Topology Model [RFC8795] which provides a TE network topology
   abstraction and management operation.  As per [RFC8795], a TE node
   connectivity matrix is the TE node's switching limitations in the
   form of valid switching combinations of the TE node's LTPs and
   potential TE paths.  The VN representation relies on a single
   abstract TE node with a connectivity matrix.  The VN can be
   abstracted as a set of edge-to-edge links (a Type 1 VN).  Each link
   is the VN member that is mapped to the connectivity matrix entry

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   (Section 2.1).  The VN can also be abstracted as a topology of
   virtual nodes and virtual links (a Type 2 VN).  Alongside the mapping
   of VN members to connectivity matrix entry, an underlay path can also
   be specified (Section 2.2).

   Once the TE-topology Model is used in triggering VN instantiation
   over the networks, the TE-tunnel [I-D.ietf-teas-yang-te] Model will
   inevitably interact with the TE-Topology model for setting up actual
   tunnels and LSPs under the tunnels.

   Sections 2 and 3 provide a discussion of how the VN YANG model is
   applicable to the ACTN context where Virtual Network Service (VNS)
   operation is implemented for the Customer Network Controller (CNC)-
   Multi-Domain Service Coordinator (MDSC) interface (CMI).

   The YANG model on the CMI is also known as the customer service model
   in [RFC8309].  The YANG model discussed in this document is used to
   operate customer-driven VNs during the VN instantiation, VN
   computation, and its life-cycle service management and operations.

   The VN operational state is included in the same tree as the
   configuration consistent with Network Management Datastore
   Architecture (NMDA) [RFC8342].

1.1.  Terminology

   This document borrows the following terms from [RFC8453]:

   *  VN: Virtual Network

   *  AP: Access Point

   *  VNAP: VN Access Point

   *  ACTN: Abstraction and Control of TE Networks

   *  CNC: Customer Network Controller

   *  MDSC: Multi-Domain Service Coordinator

   *  CMI: CNC-MDSC Interface

   This document borrows the following terms from [RFC8795]:

   *  LTP: Link Termination Point

   *  Connectivity Matrix

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   This document borrows the terminology in Section 1.1 of [RFC7926].

   This document uses the term 'Service Model' as described in
   [RFC8309].

1.2.  Tree Diagram

   A simplified graphical representation of the data model is used in
   Section 5 of this document.  The meaning of the symbols in these
   diagrams is defined in [RFC8340].

1.3.  Prefixes in Data Node Names

   In this document, the names of data nodes and other data model
   objects are prefixed using the standard prefix associated with the
   corresponding YANG imported modules, as shown in Table 1.

             +==========+=======================+===========+
             | Prefix   | YANG module           | Reference |
             +==========+=======================+===========+
             | vn       | ietf-vn               | [RFCXXXX] |
             +----------+-----------------------+-----------+
             | yang     | ietf-yang-types       | [RFC6991] |
             +----------+-----------------------+-----------+
             | nw       | ietf-network          | [RFC8345] |
             +----------+-----------------------+-----------+
             | nt       | ietf-network-topology | [RFC8345] |
             +----------+-----------------------+-----------+
             | te-types | ietf-te-types         | [RFC8776] |
             +----------+-----------------------+-----------+
             | tet      | ietf-te-topology      | [RFC8795] |
             +----------+-----------------------+-----------+

             Table 1: Prefixes and corresponding YANG modules

   Note: The RFC Editor will replace XXXX with the number assigned to
   the RFC once this draft becomes an RFC.

2.  Use-case of VN YANG Model in the ACTN context

   In this section, ACTN is being used to illustrate the general usage
   of the VN YANG model.  The model presented in this section has the
   following ACTN context.

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                             +-------+
                             |  CNC  |
                             +-------+
                                 |
                                 |    VN YANG + TE-topology YANG
                                 |
                      +-----------------------+
                      |         MDSC          |
                      +-----------------------+

                             Figure 1: ACTN CMI

   Both ACTN VN YANG and TE-topology models are used over the CMI to
   establish a VN over TE networks as shown in Figure 1.

2.1.  Type 1 VN

   As defined in [RFC8453], a Virtual Network is a customer view of the
   TE network.  To recapitulate VN types from [RFC8453], Type 1 VN is
   defined as follows:

   |  The VN can be seen as a set of edge-to-edge abstract links (a Type
   |  1 VN).  Each abstract link is referred to as a VN member and is
   |  formed as an end-to-end tunnel across the underlying networks.
   |  Such tunnels may be constructed by recursive slicing or
   |  abstraction of paths in the underlying networks and can encompass
   |  edge points of the customer's network, access links, intra-domain
   |  paths, and inter-domain links.

   If we were to create a VN where we have four VN-members as
   follows:

                  VN-member 1       L1-L4
                  VN-member 2       L1-L7
                  VN-member 3       L2-L4
                  VN-member 4       L3-L8

          Where L1, L2, L3, L4, L7, and L8 correspond to a Customer End-
          Point (or AP).

   This VN can be modelled as one abstract node representation as
   follows in Figure 2:

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              +----------------------------------------------+
              |                                              |
        L1----|..............................................|------L4
              |   .                                       .  |
              |    .                AN1                  .   |
              |     .                                   .    |
              |      ..................................*.....|------L7
              |                                       .      |
       L2-----|.......................................       |
              |                                              |
       L3-----|..............................................|------L8
              |                                              |
              +----------------------------------------------+

                Figure 2: Abstract Node (One node topology)

   Modelling a VN as one abstract node is the easiest way for customers
   to express their end-to-end connectivity as shown in Figure 2.

2.2.  Type 2 VN

   For some VN members, the customers are allowed to configure the
   intended path.  To achieve this, alongside the single node abstract
   topology, an underlay topology is also needed.  The underlay topology
   could be native TE topology or an abstract TE topology.  The intended
   path is set based on the nodes and links of the underlay topology.
   Type 1 VN can be seen as a higher abstraction of a Type 2 VN (which
   along with a single node abstract topology, an underlay topology and
   the intended path is specified).  These topologies could be mutually
   agreed between CNC and MDSC prior to VN creation or it could be
   created as part of VN instantiation.

   If a Type 2 VN is desired for some or all of the VN members of a Type
   1 VN (see the example in Section 2.1), the TE-topology model can
   provide the following abstract topologies (a single node topology AN1
   and an underlay topology (with nodes S1 to S11 and corresponding
   links)).

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              +----------------------------------------------+
              |             S1               S2              |
              |              O...............O               |
              |     ......... .......         .              |
              |    .                 .         .             |
              |S3 .                   . S4      . S5         |
        L1----|.O......................O.........O...........|------L4
              |   .                     .         .          |
              |    .                     .         .         |
              |     . S6                  . S7      . S8     |
              |      O     ................O.........O.......|------L7
              |     . .   .                 .   .....        |
              |S9  .   . .S10                . .             |
       L2-----|...O.....O.....................O..............|------L8
              |  .                          S11              |
       L3-----|..                                            |
              |                                          AN1 |
              +----------------------------------------------+

                         Figure 3: Type 2 topology

   As shown in Figure 3, the abstract node is AN1 and an underlay
   topology is depicted with nodes and links (S1 to S11).

   As an example, if VN-member 1 (L1-L4) is chosen to configure its own
   path over Type 2 topology, it can select, say, a path that consists
   of the explicit abstract path {S3,S4,S5} based on the underlay
   topology and its service requirement.  This capability is enacted via
   TE-topology configuration by the customer.

3.  High-Level Control Flows with Examples

3.1.  Type 1 VN Illustration

   If this VN is Type 1, the following diagram shows the message flow
   between CNC and MDSC to instantiate this VN using VN and TE-Topology
   Models.

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               +--------+                        +--------+
               |  CNC   |                        |  MDSC  |
               +--------+                        +--------+
                    |                                 |
                    |                                 |
   CNC POST TE-topo |  POST /nw:networks/nw:network/  |
   model(with Conn. |  nw:node/te-node-id/            |
   Matrix on one    |  tet:connectivity-matrices/     |
   Abstract node    |  tet:connectivity-matrix        |
                    |-------------------------------->|
                    |                   HTTP 200      |
                    |<--------------------------------|
                    |                                 |
   CNC POST the     |  POST /virtual-network          |
   VN identifying   |-------------------------------->| If there is
   AP, VNAP and VN- |                                 | multi-src/dest
   Members and maps |                                 | then MDSC
   to the TE-topo   |                 HTTP 200        | selects a
                    |<--------------------------------| src or dest
                    |                                 | and updates
                    |                                 | VN YANG
   CNC GET the      |  GET /virtual-network           |
   VN YANG status   |-------------------------------->|
                    |                                 |
                    |  HTTP 200 (VN with status:      |
                    |  selected VN-members            |
                    |  in case of multi-s-d)          |
                    |<--------------------------------|
                    |                                 |

                      Figure 4: Type 1 VN Illustration

3.2.  Type 2 VN Illustration

   For some VN members, the customer may want to "configure" explicit
   path that connects its two end-points.  Let us consider the following
   example.

      VN-member 1  L1-L4 (via S3, S4, and S5)

      VN-member 2  L1-L7 (via S3, S4, S7 and S8)

      VN-member 3  L2-L7 (via S9, S10, and S11)

      VN-member 4  L3-L8 (via S9, S10 and S11)

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   There are two options depending on whether CNC or MDSC creates the
   single abstract node topology.

   Case 1:

   If CNC creates the single-abstract-node topology, the following
   diagram shows the message flow between CNC and MDSC to instantiate
   this VN using VN and TE-Topology Model.

               +--------+                                +--------+
               |  CNC   |                                |  MDSC  |
               +--------+                                +--------+
                    |                                         |
                    |                                         |
   CNC POST TE-topo |  POST /nw:networks/nw:network/          |
   model(with Conn. |  nw:node/te-node-id/tet:connectivity-   |
   Matrix on one    |  matrices/tet:connectivity-matrix       |
   Abstract node and|---------------------------------------->|
   Explicit paths in|                                         |
   the conn. matrix)|                       HTTP 200          |
                    |<----------------------------------------|
                    |                                         |
   CNC POST the     |  POST /virtual-network                  |
   VN identifying   |---------------------------------------->|
   AP, VNAP and VN- |                                         |
   Members and maps |                                         |
   to the TE-topo   |                         HTTP 200        |
                    |<----------------------------------------|
                    |                                         |
                    |                                         |
   CNC GET the      |  GET /virtual-network                   |
   VN YANG status   |---------------------------------------->|
                    |                                         |
                    |  HTTP 200 (VN with status)              |
                    |<----------------------------------------|
                    |                                         |

                  Figure 5: Type 2 VN Illustration, Case 1

   Case 2:

   On the other hand, if MDSC create the single-abstract-node topology
   based on VN YANG posted by the CNC, the following diagram shows the
   message flow between CNC and MDSC to instantiate this VN using VN and
   TE-Topology Models.

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               +--------+                        +--------+
               |  CNC   |                        |  MDSC  |
               +--------+                        +--------+
                    |                                 |
                    |                                 |
   CNC POST VN      |                                 |
   Identifying AP,  |                                 |
   VNAP and VN-     |  POST /virtual-network          | MDSC populates
   Members          |-------------------------------->| a single Abst.
                    |                 HTTP 200        | node topology
                    |<--------------------------------| by itself
                    |                                 |
   CNC GET VN &     |  GET /virtual-network  &        |
   POST TE-Topo     |  POST /nw:networks/nw:network/  |
   Models (with     |  nw:node/te-node-id/tet:        |
   Conn. Matrix     |  connectivity-matrices/         |
   on the           |  tet:connectivity-matrix        |
   Abstract Node    |-------------------------------->|
   and explicit     |                                 |
   paths in the     |                                 |
   conn. matrix)    |                                 |
                    |                 HTTP 200        |
                    |<--------------------------------|
                    |                                 |
                    |                                 |
   CNC GET the      |  GET /virtual-network           |
   VN YANG status   |-------------------------------->|
                    |                                 |
                    |  HTTP 200 (VN with status)      |
                    |<--------------------------------|
                    |                                 |

                  Figure 6: Type 2 VN Illustration, Case 2

   Note that the underlay topology (which is referred to by the single-
   abstract-node topology) could be a Native/White topology or a Grey
   topology ([RFC8453]) that is further customised based on the
   requirements of the customer and configured at MDSC.

   Appendix B provides JSON examples for both VN model and TE-topology
   Connectivity Matrix sub-model to illustrate how a VN can be created
   by the CNC making use of the VN module as well as the TE-topology
   Connectivity Matrix module.

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3.2.1.  VN and AP Usage

   The customer access information may be known at the time of VN
   creation.  A shared logical AP identifier is used between the
   customer and the operator to identify the access link between
   Customer Edge (CE) and Provider Edge (PE).  This is described in
   Section 6 of [RFC8453].

   In some VN operations, the customer access may not be known at the
   initial VN creation.  The VN operation allows the creation of a VN
   with only a PE identifier as well.  The customer access information
   could be added later.

   To achieve this, the 'ap' container has a leaf for 'pe' node that
   allows AP to be created with PE information.  The vn-member (and vn)
   could use APs that only have PE information initially.

4.  VN Model Usage

4.1.  Customer view of VN

   The VN-YANG model allows to define a customer view, and allows the
   customer to communicate using the VN constructs as described in the
   [RFC8454].  It allows the grouping of edge-to-edge links (i.e., VN
   members) under a common umbrella of VN.  This allows the customer to
   instantiate and view the VN as one entity, making it easier for some
   customers to work on VN without worrying about the details of the
   provider-based YANG models.

   This is similar to the benefits offered by a separate YANG model for
   the customer services as described in [RFC8309], which states that
   service models do not make any assumption about how a service is
   actually engineered and delivered for a customer.

4.2.  Auto-creation of VN by MDSC

   The VN could be configured at the MDSC explicitly by the CNC using
   the VN YANG model.  In some other cases, the VN is not explicitly
   configured, but created automatically by the MDSC based on the
   customer service model and local policy, even in these cases, the VN
   YANG model can be used by the CNC to learn details of the underlying
   VN, created to meet the requirements of the customer service model.

4.3.  Innovative Services

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4.3.1.  VN Compute

   VN Model supports VN compute (pre-instantiation mode) to view the
   full VN as a single entity before instantiation.  Achieving this via
   path computation or "compute only" tunnel setup
   ([I-D.ietf-teas-yang-te]) does not provide the same functionality.

               +--------+                                +--------+
               |  CNC   |                                |  MDSC  |
               +--------+                                +--------+
                    |                                         |
                    |                                         |
   CNC POST TE-topo |  POST /nw:networks/nw:network/          |
   model(with Conn. |  nw:node/te-node-id/tet:connectivity-   |
   Matrix on one    |  matrices/tet:connectivity-matrix       |
   Abstract node and|---------------------------------------->|
   constraints in   |                                         |
   the conn. matrix)|                       HTTP 200          |
                    |<----------------------------------------|
                    |                                         |
                    |                                         |
   CNC calls RPC to |  RPC /vn-compute                        |
   compute the VN   |---------------------------------------->|
   as per the       |                                         |
   refered TE-Topo  |                                         |
                    |                                         |
                    |           HTTP 200 (Computed VN)        |
                    |<----------------------------------------|
                    |                                         |

                            Figure 7: VN Compute

   The VN compute RPC allows you to optionally include the constraints
   and the optimization criteria at the VN as well as at the individual
   VN-member level.  Thus, the RPC can be used independently to get the
   computed VN result without creating an abstract topology first.

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               +--------+                                +--------+
               |  CNC   |                                |  MDSC  |
               +--------+                                +--------+
                    |                                         |
                    |                                         |
   CNC calls RPC to |  RPC /vn-compute                        |
   compute the VN   |---------------------------------------->|
   as per the       |                                         |
   constraints and  |                                         |
   VN-members       |                                         |
                    |           HTTP 200 (Computed VN)        |
                    |<----------------------------------------|
                    |                                         |

                            Figure 8: VN Compute

   In either case the output includes a reference to the single node
   abstract topology with each VN-member including a reference to the
   connectivity-matrix-id where the path properties could be found.

   To achieve this the VN-compute RPC reuses the following common
   groupings:

   *  te-types:generic-path-constraints: This is used optionally in the
      RPC input at the VN and/or VN-member level.  The VN-member level
      overrides the VN-level data.  This also overrides any constraints
      in the referenced abstract node in the TE topology.

   *  te-types:generic-path-optimization: This is used optionally in the
      RPC input at the VN and/or VN-member level.  The VN-member level
      overrides the VN-level data.  This also overrides any optimization
      in the referenced abstract node in the TE topology.

   *  vn-member: This identifies the VN member in both RPC input and
      output.

   *  vn-policy: This is used optionally in the RPC input to apply any
      VN level policies.

   When MDSC receives this RPC it computes the VN based on the input
   provided in the RPC call.  This computation does not create a VN or
   reserve any resources in the system, it simply computes the resulting
   VN based on information at the MDSC or in coordination with the CNC.
   A single-node-abstract topology is used to convey the result of each
   VN member as a reference to the connectivity-matrix-id.  In case of
   an error, the error information is included.

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  rpcs:
    +---x vn-compute
       +---w input
       |  +---w te-topology-identifier
       |  |  +---w provider-id?   te-global-id
       |  |  +---w client-id?     te-global-id
       |  |  +---w topology-id?   te-topology-id
       |  +---w abstract-node?
       |  |       -> /nw:networks/network/node/tet:te-node-id
       |  +---w path-constraints
       |  |  +---w te-bandwidth
       |  |  |  +---w (technology)?
       |  |  |        ...
       |  |  +---w link-protection?          identityref
       |  |  +---w setup-priority?           uint8
       |  |  +---w hold-priority?            uint8
       |  |  +---w signaling-type?           identityref
       |  |  +---w path-metric-bounds
       |  |  |  +---w path-metric-bound* [metric-type]
       |  |  |        ...
       |  |  +---w path-affinities-values
       |  |  |  +---w path-affinities-value* [usage]
       |  |  |        ...
       |  |  +---w path-affinity-names
       |  |  |  +---w path-affinity-name* [usage]
       |  |  |        ...
       |  |  +---w path-srlgs-lists
       |  |  |  +---w path-srlgs-list* [usage]
       |  |  |        ...
       |  |  +---w path-srlgs-names
       |  |  |  +---w path-srlgs-name* [usage]
       |  |  |        ...
       |  |  +---w disjointness?             te-path-disjointness
       |  +---w cos?                      te-types:te-ds-class
       |  +---w optimizations
       |  |  +---w (algorithm)?
       |  |     +--:(metric) {path-optimization-metric}?
       |  |     |     ...
       |  |     +--:(objective-function)
       |  |              {path-optimization-objective-function}?
       |  |           ...
       |  +---w vn-member-list* [id]
       |  |  +---w id                        vnm-id
       |  |  +---w src
       |  |  |  +---w ap?          -> /access-point/ap/id
       |  |  |  +---w vn-ap-id?
       |  |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
       |  |  |  +---w multi-src?   boolean {multi-src-dest}?

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       |  |  +---w dest
       |  |  |  +---w ap?           -> /access-point/ap/id
       |  |  |  +---w vn-ap-id?
       |  |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
       |  |  |  +---w multi-dest?   boolean {multi-src-dest}?
       |  |  +---w connectivity-matrix-id?   leafref
       |  |  +---w underlay
       |  |  +---w path-constraints
       |  |  |  +---w te-bandwidth
       |  |  |  |     ...
       |  |  |  +---w link-protection?          identityref
       |  |  |  +---w setup-priority?           uint8
       |  |  |  +---w hold-priority?            uint8
       |  |  |  +---w signaling-type?           identityref
       |  |  |  +---w path-metric-bounds
       |  |  |  |     ...
       |  |  |  +---w path-affinities-values
       |  |  |  |     ...
       |  |  |  +---w path-affinity-names
       |  |  |  |     ...
       |  |  |  +---w path-srlgs-lists
       |  |  |  |     ...
       |  |  |  +---w path-srlgs-names
       |  |  |  |     ...
       |  |  |  +---w disjointness?             te-path-disjointness
       |  |  +---w cos?                      te-types:te-ds-class
       |  |  +---w optimizations
       |  |     +---w (algorithm)?
       |  |           ...
       |  +---w vn-level-diversity?       te-types:te-path-disjointness
       +--ro output
          +--ro te-topology-identifier
          |  +--ro provider-id?   te-global-id
          |  +--ro client-id?     te-global-id
          |  +--ro topology-id?   te-topology-id
          +--ro abstract-node?
          |       -> /nw:networks/network/node/tet:te-node-id
          +--ro vn-member-list* [id]
             +--ro id                        vnm-id
             +--ro src
             |  +--ro ap?          -> /access-point/ap/id
             |  +--ro vn-ap-id?
             |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
             |  +--ro multi-src?   boolean {multi-src-dest}?
             +--ro dest
             |  +--ro ap?           -> /access-point/ap/id
             |  +--ro vn-ap-id?
             |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id

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             |  +--ro multi-dest?   boolean {multi-src-dest}?
             +--ro connectivity-matrix-id?   leafref
             +--ro underlay
             +--ro if-selected?              boolean {multi-src-dest}?
             +--ro compute-status?           vn-compute-status
             +--ro error-info
                +--ro error-description?   string
                +--ro error-timestamp?     yang:date-and-time
                +--ro error-reason?        identityref

4.3.2.  Multi-sources and Multi-destinations

   In creating a virtual network, the list of sources or destinations or
   both may not be pre-determined by the customer.  For instance, for a
   given source, there may be a list of multiple-destinations to which
   the optimal destination may be chosen depending on the network
   resource situations.  Likewise, for a given destination, there may
   also be multiple-sources from which the optimal source may be chosen.
   In some cases, there may be a pool of multiple sources and
   destinations from which the optimal source-destination may be chosen.
   The following YANG tree shows how to model multi-sources and multi-
   destinations.

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  module: ietf-vn
    +--rw virtual-network
       +--rw vn* [id]
          +--rw id                        vn-id
          +--rw te-topology-identifier
          |  +--rw provider-id?   te-global-id
          |  +--rw client-id?     te-global-id
          |  +--rw topology-id?   te-topology-id
          +--rw abstract-node?
          |       -> /nw:networks/network/node/tet:te-node-id
          +--rw vn-member* [id]
          |  +--rw id                        vnm-id
          |  +--rw src
          |  |  +--rw ap?          -> /access-point/ap/id
          |  |  +--rw vn-ap-id?
          |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
          |  |  +--rw multi-src?   boolean {multi-src-dest}?
          |  +--rw dest
          |  |  +--rw ap?           -> /access-point/ap/id
          |  |  +--rw vn-ap-id?
          |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
          |  |  +--rw multi-dest?   boolean {multi-src-dest}?
          |  +--rw connectivity-matrix-id?   leafref
          |  +--rw underlay
          |  +--ro oper-status?              te-types:te-oper-status
          |  +--ro if-selected?              boolean {multi-src-dest}?
          +--rw admin-status?             te-types:te-admin-status
          +--ro oper-status?              te-types:te-oper-status
          +--rw vn-level-diversity?       te-types:te-path-disjointness

4.4.  Others

   The VN YANG model can be easily augmented to support the mapping of
   VN to the Services such as L3SM and L2SM as described in
   [I-D.ietf-teas-te-service-mapping-yang].

   The VN YANG model can be extended to support telemetry, performance
   monitoring and network autonomics as described in
   [I-D.ietf-teas-actn-pm-telemetry-autonomics].

   Note that the YANG model is tightly coupled with the TE Topology
   model [RFC8795].  Any underlay technology not supported by [RFC8795]
   is also not supported by this model.  The model does include an empty
   container called "underlay" that can be augmented.  For example the
   Segment Routing (SR) Policy [RFC9256] information can be augmented
   for the SR underlay by a future model.

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   Apart from the te-types:generic-path-constraints and te-
   types:generic-path-optimization, an additional leaf cos for the class
   of service [RFC4124] is added to represent the Class-Type of traffic
   to be used as one of the path constraints.

4.5.  Summary

   This section summarizes the features of the VN YANG.

   *  Maintenance of AP and VNAP along with VN

   *  VN construct to group of edge-to-edge links

   *  Ability to support various VN and VNS Types

      -  VN Type 1: Customer configures the VN as a set of VN Members.
         No other details need to be set by the customer, making for a
         simplified operation for the customer.

      -  VN Type 2: Along with VN Members, the customer could also
         provide an abstract topology, this topology is provided by the
         Abstract TE Topology YANG Model.

      -  Note that the VN Type is not explicitly identified in the VN
         Yang model, as the VN Model is exactly the same for both VN
         Type 1 and 2.  The VN type can be implicitly known based on the
         referenced TE topology and whether the connectivity matrix
         includes the underlay path (Type 2) or not (Type 1).

   *  VN Compute (pre-instantiate)

   *  Multi-Source / Multi-Destination

5.  VN YANG Model (Tree Structure)

module: ietf-vn
  +--rw access-point
  |  +--rw ap* [id]
  |     +--rw id               ap-id
  |     +--rw pe?
  |     |       -> /nw:networks/network/node/tet:te-node-id
  |     +--rw max-bandwidth?   te-types:te-bandwidth
  |     +--rw avl-bandwidth?   te-types:te-bandwidth
  |     +--rw vn-ap* [id]
  |        +--rw id               ap-id
  |        +--rw vn?              -> /virtual-network/vn/id
  |        +--rw abstract-node?   -> /nw:networks/network/node/node-id
  |        +--rw ltp?             leafref

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  |        +--ro max-bandwidth?   te-types:te-bandwidth
  +--rw virtual-network
     +--rw vn* [id]
        +--rw id                        vn-id
        +--rw te-topology-identifier
        |  +--rw provider-id?   te-global-id
        |  +--rw client-id?     te-global-id
        |  +--rw topology-id?   te-topology-id
        +--rw abstract-node?
        |       -> /nw:networks/network/node/tet:te-node-id
        +--rw vn-member* [id]
        |  +--rw id                        vnm-id
        |  +--rw src
        |  |  +--rw ap?          -> /access-point/ap/id
        |  |  +--rw vn-ap-id?
        |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
        |  |  +--rw multi-src?   boolean {multi-src-dest}?
        |  +--rw dest
        |  |  +--rw ap?           -> /access-point/ap/id
        |  |  +--rw vn-ap-id?
        |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
        |  |  +--rw multi-dest?   boolean {multi-src-dest}?
        |  +--rw connectivity-matrix-id?   leafref
        |  +--rw underlay
        |  +--ro oper-status?              te-types:te-oper-status
        |  +--ro if-selected?              boolean {multi-src-dest}?
        +--rw admin-status?             te-types:te-admin-status
        +--ro oper-status?              te-types:te-oper-status
        +--rw vn-level-diversity?       te-types:te-path-disjointness

  rpcs:
    +---x vn-compute
       +---w input
       |  +---w te-topology-identifier
       |  |  +---w provider-id?   te-global-id
       |  |  +---w client-id?     te-global-id
       |  |  +---w topology-id?   te-topology-id
       |  +---w abstract-node?
       |  |       -> /nw:networks/network/node/tet:te-node-id
       |  +---w path-constraints
       |  |  +---w te-bandwidth
       |  |  |  +---w (technology)?
       |  |  |        ...
       |  |  +---w link-protection?          identityref
       |  |  +---w setup-priority?           uint8
       |  |  +---w hold-priority?            uint8
       |  |  +---w signaling-type?           identityref
       |  |  +---w path-metric-bounds

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       |  |  |  +---w path-metric-bound* [metric-type]
       |  |  |        ...
       |  |  +---w path-affinities-values
       |  |  |  +---w path-affinities-value* [usage]
       |  |  |        ...
       |  |  +---w path-affinity-names
       |  |  |  +---w path-affinity-name* [usage]
       |  |  |        ...
       |  |  +---w path-srlgs-lists
       |  |  |  +---w path-srlgs-list* [usage]
       |  |  |        ...
       |  |  +---w path-srlgs-names
       |  |  |  +---w path-srlgs-name* [usage]
       |  |  |        ...
       |  |  +---w disjointness?             te-path-disjointness
       |  +---w cos?                      te-types:te-ds-class
       |  +---w optimizations
       |  |  +---w (algorithm)?
       |  |     +--:(metric) {path-optimization-metric}?
       |  |     |     ...
       |  |     +--:(objective-function)
       |  |              {path-optimization-objective-function}?
       |  |           ...
       |  +---w vn-member-list* [id]
       |  |  +---w id                        vnm-id
       |  |  +---w src
       |  |  |  +---w ap?          -> /access-point/ap/id
       |  |  |  +---w vn-ap-id?
       |  |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
       |  |  |  +---w multi-src?   boolean {multi-src-dest}?
       |  |  +---w dest
       |  |  |  +---w ap?           -> /access-point/ap/id
       |  |  |  +---w vn-ap-id?
       |  |  |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
       |  |  |  +---w multi-dest?   boolean {multi-src-dest}?
       |  |  +---w connectivity-matrix-id?   leafref
       |  |  +---w underlay
       |  |  +---w path-constraints
       |  |  |  +---w te-bandwidth
       |  |  |  |     ...
       |  |  |  +---w link-protection?          identityref
       |  |  |  +---w setup-priority?           uint8
       |  |  |  +---w hold-priority?            uint8
       |  |  |  +---w signaling-type?           identityref
       |  |  |  +---w path-metric-bounds
       |  |  |  |     ...
       |  |  |  +---w path-affinities-values
       |  |  |  |     ...

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       |  |  |  +---w path-affinity-names
       |  |  |  |     ...
       |  |  |  +---w path-srlgs-lists
       |  |  |  |     ...
       |  |  |  +---w path-srlgs-names
       |  |  |  |     ...
       |  |  |  +---w disjointness?             te-path-disjointness
       |  |  +---w cos?                      te-types:te-ds-class
       |  |  +---w optimizations
       |  |     +---w (algorithm)?
       |  |           ...
       |  +---w vn-level-diversity?       te-types:te-path-disjointness
       +--ro output
          +--ro te-topology-identifier
          |  +--ro provider-id?   te-global-id
          |  +--ro client-id?     te-global-id
          |  +--ro topology-id?   te-topology-id
          +--ro abstract-node?
          |       -> /nw:networks/network/node/tet:te-node-id
          +--ro vn-member-list* [id]
             +--ro id                        vnm-id
             +--ro src
             |  +--ro ap?          -> /access-point/ap/id
             |  +--ro vn-ap-id?
             |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
             |  +--ro multi-src?   boolean {multi-src-dest}?
             +--ro dest
             |  +--ro ap?           -> /access-point/ap/id
             |  +--ro vn-ap-id?
             |  |       -> /access-point/ap[id=current()/../ap]/vn-ap/id
             |  +--ro multi-dest?   boolean {multi-src-dest}?
             +--ro connectivity-matrix-id?   leafref
             +--ro underlay
             +--ro if-selected?              boolean {multi-src-dest}?
             +--ro compute-status?           vn-compute-status
             +--ro error-info
                +--ro error-description?   string
                +--ro error-timestamp?     yang:date-and-time
                +--ro error-reason?        identityref

6.  VN YANG Model

   The YANG model is as follows:

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   <CODE BEGINS> file "ietf-vn@2024-06-22.yang"
   module ietf-vn {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-vn";
     prefix vn;

     /* Import common YANG types */

     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types";
     }

     /* Import network */

     import ietf-network {
       prefix nw;
       reference
         "RFC 8345: A YANG Data Model for Network Topologies";
     }

     /* Import network topology */

     import ietf-network-topology {
       prefix nt;
       reference
         "RFC 8345: A YANG Data Model for Network Topologies";
     }

     /* Import TE Common types */

     import ietf-te-types {
       prefix te-types;
       reference
         "RFC 8776: Common YANG Data Types for Traffic Engineering";
     }

     /* Import TE Topology */

     import ietf-te-topology {
       prefix tet;
       reference
         "RFC 8795: YANG Data Model for Traffic Engineering (TE)
          Topologies";
     }

     organization

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       "IETF Traffic Engineering Architecture and Signaling (TEAS)
        Working Group";
     contact
       "WG Web:  <https://datatracker.ietf.org/wg/teas/>
        WG List:  <mailto:teas@ietf.org>
        Editor: Young Lee <younglee.tx@gmail.com>
              : Dhruv Dhody <dhruv.ietf@gmail.com>";
     description
       "This module contains a YANG module for the Virtual Network
        (VN). It describes a VN operation module that can take place
        in the context of the Customer Network Controller (CNC)-
        Multi-Domain Service Coordinator (MDSC) interface (CMI) of
        the Abstraction and Control of Traffic Engineered (TE)
        Networks (ACTN) architecture where the CNC is the actor of
        a VN Instantiation/modification/deletion as per RFC 8453.

        This module uses following abbreviations:
        - VN: Virtual Network
        - AP: Access Point
        - VNAP: Virtual Network Access Point
        - LTP: Link Termination Point
        - PE: Provider Edge
        - COS: Class of Service

        Further, 'src' and 'dest' is used for source and destination
        respectively.

        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 2024-06-22 {
       description
         "The initial version.";
       reference
         "RFC XXXX: A YANG Data Model for Virtual Network (VN)
          Operations";
     }

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     /* Features */

     feature multi-src-dest {
       description
         "Support for selection of one src or destination
          among multiple.";
       reference
         "RFC 8453: Framework for Abstraction and Control of TE
          Networks (ACTN)";
     }

     /* Typedef */

     typedef vn-id {
       type string {
         length "1..max";
       }
       description
         "A type definition for Virtual Network (VN)
          identifier.";
     }

     typedef ap-id {
       type string {
         length "1..max";
       }
       description
         "A type definition for Access Point (AP) identifier.";
     }

     typedef vnm-id {
       type string {
         length "1..max";
       }
       description
         "A type definition for VN member identifier.";
     }

     typedef vn-compute-status {
       type te-types:te-common-status;
       description
         "A type definition for representing the VN compute status. Note
          that all statuses apart from up and down are considered as
          unknown.";
     }

     /* identities */

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     identity vn-computation-error-reason {
       description
         "Base identity for VN computation error reasons.";
     }

     identity vn-computation-error-not-ready {
       base vn-computation-error-reason;
       description
         "VN computation has failed because the MDSC is not
          ready.";
     }

     identity vn-computation-error-no-cnc {
       base vn-computation-error-reason;
       description
         "VN computation has failed because one or more dependent
          CNC are unavailable.";
     }

     identity vn-computation-error-no-resource {
       base vn-computation-error-reason;
       description
         "VN computation has failed because there is no
          available resource in one or more domains.";
     }

     identity vn-computation-error-path-not-found {
       base vn-computation-error-reason;
       description
         "VN computation failed as no path found.";
     }

     identity vn-computation-ap-unknown {
       base vn-computation-error-reason;
       description
         "VN computation failed as the source or destination Access
          Point (AP) not known.";
     }

     /* Groupings */

     grouping vn-member {
       description
         "The vn-member is described by this grouping.";
       leaf id {
         type vnm-id;
         description
           "A vn-member identifier.";

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       }
       container src {
         description
           "The source of VN Member.";
         leaf ap {
           type leafref {
             path "/access-point/ap/id";
           }
           description
             "A reference to source AP.";
         }
         leaf vn-ap-id {
           type leafref {
             path "/access-point/ap[id=current()/../ap]/vn-ap"
                + "/id";
           }
           description
             "A reference to source VNAP.";
         }
         leaf multi-src {
           if-feature "multi-src-dest";
           type boolean;
           default "false";
           description
             "Is the source part of multi-source, where
              only one of the sources is enabled.";
         }
       }
       container dest {
         description
           "the destination of VN Member.";
         leaf ap {
           type leafref {
             path "/access-point/ap/id";
           }
           description
             "A reference to destination AP.";
         }
         leaf vn-ap-id {
           type leafref {
             path "/access-point/ap[id=current()/../ap]/"
                + "vn-ap/id";
           }
           description
             "A reference to dest VNAP.";
         }
         leaf multi-dest {
           if-feature "multi-src-dest";

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           type boolean;
           default "false";
           description
             "Is destination part of multi-destination, where only one
              of the destinations is enabled.";
         }
       }
       leaf connectivity-matrix-id {
         type leafref {
           path "/nw:networks/nw:network/nw:node/tet:te/"
              + "tet:te-node-attributes/"
              + "tet:connectivity-matrices/"
              + "tet:connectivity-matrix/tet:id";
         }
         description
           "A reference to connectivity-matrix.";
         reference
           "RFC 8795: YANG Data Model for Traffic Engineering (TE)
            Topologies";
       }
       container underlay {
         description
           "An empty container that can be augmented with underlay
            technology information not supported by RFC 8795 (for
            example - Segment Routing (SR).";
       }
       reference
         "RFC 8454: Information Model for Abstraction and Control of TE
          Networks (ACTN)";
     }

     grouping vn-policy {
       description
         "policy for VN-level diversity";
       leaf vn-level-diversity {
         type te-types:te-path-disjointness;
         description
           "The type of disjointness on the VN level (i.e., across all
            VN members).";
       }
     }

     /* Configuration data nodes */

     container access-point {
       description
         "AP configurations";
       list ap {

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         key "id";
         description
           "access-point identifier.";
         leaf id {
           type ap-id;
           description
             "An AP identifier unique within the scope of the entity
              that controls the VN.";
         }
         leaf pe {
           type leafref {
             path "/nw:networks/nw:network/nw:node/tet:te-node-id";
           }
           description
             "A reference to the PE node in the native TE Topology.";
         }
         leaf max-bandwidth {
           type te-types:te-bandwidth;
           description
             "The max bandwidth of the AP.";
         }
         leaf avl-bandwidth {
           type te-types:te-bandwidth;
           description
             "The available bandwidth of the AP.";
         }
         list vn-ap {
           key "id";
           leaf id {
             type ap-id;
             description
               "A unique identifier for the VNAP.";
           }
           leaf vn {
             type leafref {
               path "/virtual-network/vn/id";
             }
             description
               "A reference to the VN.";
           }
           leaf abstract-node {
             type leafref {
               path "/nw:networks/nw:network/nw:node/nw:node-id";
             }
             must '/nw:networks/nw:network/nw:node[nw:node-id='
                + 'current()/../abstract-node]/tet:te-node-id' {
               description
                 "The associated network for the abstract-node

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                  must be TE enabled.";
             }
             description
               "A reference to the abstract node that represent
                the VN.";
           }
           leaf ltp {
             type leafref {
               path "/nw:networks/nw:network/nw:node[nw:node-id="
                  + "current()/../abstract-node]/nt:termination-point/"
                  + "tet:te-tp-id";
             }
             description
               "A reference to Link Termination Point (LTP) in the
                abstract-node i.e. the LTP should be in the abstract
                layer, and not the underlying layer.";
             reference
               "RFC 8795: YANG Data Model for Traffic Engineering (TE)
                Topologies";
           }
           leaf max-bandwidth {
             type te-types:te-bandwidth;
             config false;
             description
               "The max bandwidth of the VNAP.";
           }
           description
             "List of VNAP in this AP.";
         }
       }
       reference
         "RFC 8453: Framework for Abstraction and Control of TE
          Networks (ACTN), Section 6";
     }
     container virtual-network {
       description
         "VN configurations.";
       list vn {
         key "id";
         description
           "A virtual network is identified by a vn-id.";
         leaf id {
           type vn-id;
           description
             "An identifier unique within the scope of the entity
              that controls the VN.";
         }
         uses te-types:te-topology-identifier;

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         leaf abstract-node {
           type leafref {
             path "/nw:networks/nw:network/nw:node/tet:te-node-id";
           }
           description
             "A reference to the abstract node in TE Topology.";
         }
         list vn-member {
           key "id";
           description
             "List of vn-members in a VN.";
           uses vn-member;
           leaf oper-status {
             type te-types:te-oper-status;
             config false;
             description
               "The vn-member operational state.";
           }
           leaf if-selected {
             if-feature "multi-src-dest";
             type boolean;
             default "false";
             config false;
             description
               "Is the vn-member selected among the multi-src/dest
                options.";
           }
         }
         leaf admin-status {
           type te-types:te-admin-status;
           default "up";
           description
             "VN administrative state.";
         }
         leaf oper-status {
           type te-types:te-oper-status;
           config false;
           description
             "VN operational state.";
         }
         uses vn-policy;
       }
       reference
         "RFC 8453: Framework for Abstraction and Control of TE
          Networks (ACTN)";
     }

     /* RPC */

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     rpc vn-compute {
       description
         "The VN computation without actual instantiation. This is
          used by the CNC to get the VN results without actually
          creating it in the network.

          The input could include a reference to the single-node
          -abstract topology. It could optionally also include
          constraints and optimization criteria. The computation
          is done based on the list of VN-members.

          The output includes a reference to the single-node
          -abstract topology with each VN-member including a
          reference to the connectivity-matrix-id where the
          path properties could be found. Error information is
          also included.";
       input {
         uses te-types:te-topology-identifier;
         leaf abstract-node {
           type leafref {
             path "/nw:networks/nw:network/nw:node/tet:te-node-id";
           }
           description
             "A reference to the abstract node in TE Topology.";
         }
         uses te-types:generic-path-constraints;
         leaf cos {
           type te-types:te-ds-class;
           description
             "The class of service (COS).";
         }
         uses te-types:generic-path-optimization;
         list vn-member-list {
           key "id";
           description
             "List of VN-members in a VN.";
           uses vn-member;
           uses te-types:generic-path-constraints;
           leaf cos {
             type te-types:te-ds-class;
             description
               "The class of service.";
             reference
               "RFC 4124: Protocol Extensions for Support of
                Diffserv-aware MPLS Traffic Engineering,
                Section 4.3.1";
           }
           uses te-types:generic-path-optimization;

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         }
         uses vn-policy;
       }
       output {
         uses te-types:te-topology-identifier;
         leaf abstract-node {
           type leafref {
             path "/nw:networks/nw:network/nw:node/tet:te-node-id";
           }
           description
             "A reference to the abstract node in TE Topology.";
         }
         list vn-member-list {
           key "id";
           description
             "List of VN-members in a VN.";
           uses vn-member;
           leaf if-selected {
             if-feature "multi-src-dest";
             type boolean;
             default "false";
             description
               "Is the vn-member selected among the multi-src/dest
                options.";
             reference
               "RFC 8453: Framework for Abstraction and Control of TE
                Networks (ACTN), Section 7";
           }
           leaf compute-status {
             type vn-compute-status;
             description
               "The VN-member compute state.";
           }
           container error-info {
             description
               "Error information related to the VN member.";
             leaf error-description {
               type string {
                 length "1..max";
               }
               description
                 "Textual representation of the error occurred during
                  VN compute.";
             }
             leaf error-timestamp {
               type yang:date-and-time;
               description
                 "Timestamp of the attempt.";

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             }
             leaf error-reason {
               type identityref {
                 base vn-computation-error-reason;
               }
               description
                 "Reason for the VN computation error.";
             }
           }
         }
       }
     }
   }
   <CODE ENDS>

7.  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 NETCONF access control model [RFC8341] provides the means to
   restrict access for particular NETCONF or RESTCONF users to a
   preconfigured subset of all available NETCONF or RESTCONF protocol
   operations and content.

   The model presented in this document is used in the interface between
   the CNC and MDSC, which is referred to as CNC-MDSC Interface (CMI).
   Security risks such as malicious attack and rogue elements attempting
   to connect to the various ACTN components are possible.  Furthermore,
   some ACTN components (e.g., MDSC) represent a single point of failure
   and threat vector.  Also, there is a need to manage policy conflicts
   and eavesdropping of communication between different ACTN components.

   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:

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   *  ap: This list includes a set of sensitive data that influences how
      the access points in the VN service are attached.  By accessing
      the following data nodes, an attacker may be able to manipulate
      the VN.

      -  id

      -  pe

      -  max-bandwidth

      -  avl-bandwidth

   *  vn-ap: This list includes a set of sensitive data that influences
      how the VN service is delivered.  By accessing the following data
      nodes, an attacker may be able to manipulate the VN.

      -  id

      -  vn

      -  abstract-node

      -  ltp

      -  max-bandwidth

   *  vn: This list includes a set of sensitive data that influences how
      the VN service is delivered.  By accessing the following data
      nodes, an attacker may be able to manipulate the VN.

      -  id

      -  te-topology-identifier

      -  abstract-node

   *  vn-member: This list includes a set of sensitive data that
      influences how the VN member in the VN service is delivered.  By
      accessing the following data nodes, an attacker may be able to
      manipulate the VN member.

      -  id

      -  src/ap

      -  src/vn-ap-id

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      -  dest/ap

      -  dest/vn-ap-id

      -  connectivity-matrix-id

   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:

   *  oper-status: This leaf can reveal the current operational state of
      the VN.

   *  if-selected: This leaf can reveal which vn-member is selected
      among the various multi-src/dest options.

   Some of the RPC operations in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  These are the
   operations and their sensitivity/vulnerability:

   *  vn-compute: This RPC triggers the VN computation at the MDSC which
      can reveal the VN information.

8.  IANA Considerations

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

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

   IANA is requested to make the following allocation for the YANG
   module in the "YANG Module Names" registry [RFC6020]:

   name:         ietf-vn
   namespace:    urn:ietf:params:xml:ns:yang:ietf-vn
   prefix:       vn
   reference:    RFC XXXX

9.  Acknowledgments

   The authors would like to thank Xufeng Liu, Adrian Farrel, Tom Petch,
   Mohamed Boucadair, Italo Busi, Bo Wu and Daniel King for their
   helpful comments and valuable suggestions.

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   Thanks to Andy Bierman for YANGDIR review.  Thanks to Darren Dukes
   for RTGDIR review.  Thanks to Behcet Sarikaya for GENART review.
   Thanks to Bo Wu for OPSDIR review.  Thanks to Shivan Sahib for SECDIR
   review.  Thanks to Susan Hares for RTGDIR review.

   Thanks to Deb Cooley, Francesca Palombini, Gunter Van de Velde, and
   Mahesh Jethanandani for IESG review.

10.  References

10.1.  Normative References

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

   [RFC4124]  Le Faucheur, F., Ed., "Protocol Extensions for Support of
              Diffserv-aware MPLS Traffic Engineering", RFC 4124,
              DOI 10.17487/RFC4124, June 2005,
              <https://www.rfc-editor.org/info/rfc4124>.

   [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>.

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   [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>.

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC8776]  Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin,
              "Common YANG Data Types for Traffic Engineering",
              RFC 8776, DOI 10.17487/RFC8776, June 2020,
              <https://www.rfc-editor.org/info/rfc8776>.

   [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>.

10.2.  Informative References

   [I-D.ietf-ccamp-l1csm-yang]
              Lee, Y., Lee, K., Zheng, H., de Dios, O. G., and D.
              Ceccarelli, "A YANG Data Model for L1 Connectivity Service
              Model (L1CSM)", Work in Progress, Internet-Draft, draft-
              ietf-ccamp-l1csm-yang-26, 11 April 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-ccamp-
              l1csm-yang-26>.

   [I-D.ietf-teas-actn-pm-telemetry-autonomics]
              Lee, Y., Dhody, D., Vilalta, R., King, D., and D.
              Ceccarelli, "YANG models for Virtual Network (VN)/TE
              Performance Monitoring Telemetry and Scaling Intent

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              Autonomics", Work in Progress, Internet-Draft, draft-ietf-
              teas-actn-pm-telemetry-autonomics-12, 16 March 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-teas-
              actn-pm-telemetry-autonomics-12>.

   [I-D.ietf-teas-te-service-mapping-yang]
              Lee, Y., Dhody, D., Fioccola, G., Wu, Q., Ceccarelli, D.,
              and J. Tantsura, "Traffic Engineering (TE) and Service
              Mapping YANG Data Model", Work in Progress, Internet-
              Draft, draft-ietf-teas-te-service-mapping-yang-15, 16
              March 2024, <https://datatracker.ietf.org/doc/html/draft-
              ietf-teas-te-service-mapping-yang-15>.

   [I-D.ietf-teas-yang-te]
              Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I.
              Bryskin, "A YANG Data Model for Traffic Engineering
              Tunnels, Label Switched Paths and Interfaces", Work in
              Progress, Internet-Draft, draft-ietf-teas-yang-te-36, 2
              February 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-teas-yang-te-36>.

   [RFC7926]  Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
              Ceccarelli, D., and X. Zhang, "Problem Statement and
              Architecture for Information Exchange between
              Interconnected Traffic-Engineered Networks", BCP 206,
              RFC 7926, DOI 10.17487/RFC7926, July 2016,
              <https://www.rfc-editor.org/info/rfc7926>.

   [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>.

   [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>.

   [RFC8454]  Lee, Y., Belotti, S., Dhody, D., Ceccarelli, D., and B.
              Yoon, "Information Model for Abstraction and Control of TE
              Networks (ACTN)", RFC 8454, DOI 10.17487/RFC8454,
              September 2018, <https://www.rfc-editor.org/info/rfc8454>.

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

   [RFC9256]  Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
              A., and P. Mattes, "Segment Routing Policy Architecture",
              RFC 9256, DOI 10.17487/RFC9256, July 2022,
              <https://www.rfc-editor.org/info/rfc9256>.

Appendix A.  Performance Constraints

   At the time of creation of VN, it is natural to provide VN level
   constraints and optimization criteria.  It should be noted that this
   YANG module relies on the TE-Topology Model [RFC8795] by using a
   reference to an abstract node to achieve this.  Further, the
   connectivity-matrix structure is used to assign the constraints and
   optimization criteria including delay, jitter etc.  [RFC8776] defines
   some of the metric-types already and future documents are meant to
   augment it.

   Note that the VN compute allows the inclusion of the constraints and
   the optimization criteria directly in the RPC to allow it to be used
   independently.

Appendix B.  JSON Example

B.1.  VN JSON

   This section provides JSON examples of how VN YANG model and TE
   topology model are used together to instantiate VN.

   The example in this section includes the following VN

   *  VN1 (Type 1): Which maps to the single node topology abstract1 and
      consist of VN Members 104 (L1 to L4), 107 (L1 to L7), 204 (L2 to
      L4), 308 (L3 to L8) and 108 (L1 to L8).

   *  VN2 (Type 2): Which maps to the single node topology abstract2,
      this topology has an underlay topology (called underlay).  This VN
      has a single VN member 105 (L1 to L5) and an underlay path (S4 and
      S7) has been set in the connectivity matrix of abstract2 topology;

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   *  VN3 (Type 1): This VN has a multi-source and multi-destination
      feature enabled.  VN Member 106 (L1 to L6) and 107 (L1 to L7)
      showcase multi-dest and VN Member 108 (L1 to L8) and 308 (L3 to
      L8) showcase multi-src feature.  The selected VN-member is known
      via the field "if-selected" and the corresponding connectivity-
      matrix-id.

   L1---104---L4             L1---105---L5             L1---106---L6(md)
   L1---107---L7             Underlay Path:            L1---107---L7(md)
   L2---204---L4                (S4 and S7)            L1---108---L8(ms)
   L3---308---L8                                       L3---308---L8(ms)
   L1---108---L8

        ---                       ---                       ---
        VN1                       VN2                       VN3
        ---                       ---                       ---

   Note that the VN YANG model also includes the AP and VNAP which shows
   various VN using the same AP.

   {
     "ietf-vn:access-point": {
       "ap": [
         {
           "id": "101",
           "vn-ap": [
             {
               "id": "10101",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.11"
             },
             {
               "id": "10102",
               "vn": "2",
               "abstract-node": "192.0.2.2",
               "ltp": "203.0.113.12"
             },
             {
               "id": "10103",
               "vn": "3",
               "abstract-node": "192.0.2.3",
               "ltp": "203.0.113.13"
             }
           ]
         },
         {
           "id": "202",

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           "vn-ap": [
             {
               "id": "20201",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.21"
             }
           ]
         },
         {
           "id": "303",
           "vn-ap": [
             {
               "id": "30301",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.31"
             },
             {
               "id": "30303",
               "vn": "3",
               "abstract-node": "192.0.2.3",
               "ltp": "203.0.113.33"
             }
           ]
         },
         {
           "id": "404",
           "vn-ap": [
             {
               "id": "40401",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.41"
             }
           ]
         },
         {
           "id": "505",
           "vn-ap": [
             {
               "id": "50502",
               "vn": "2",
               "abstract-node": "192.0.2.2",
               "ltp": "203.0.113.52"
             }
           ]
         },

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         {
           "id": "606",
           "vn-ap": [
             {
               "id": "60603",
               "vn": "3",
               "abstract-node": "192.0.2.3",
               "ltp": "203.0.113.63"
             }
           ]
         },
         {
           "id": "707",
           "vn-ap": [
             {
               "id": "70701",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.71"
             },
             {
               "id": "70703",
               "vn": "3",
               "abstract-node": "192.0.2.3",
               "ltp": "203.0.113.73"
             }
           ]
         },
         {
           "id": "808",
           "vn-ap": [
             {
               "id": "80801",
               "vn": "1",
               "abstract-node": "192.0.2.1",
               "ltp": "203.0.113.81"
             },
             {
               "id": "80803",
               "vn": "3",
               "abstract-node": "192.0.2.3",
               "ltp": "203.0.113.83"
             }
           ]
         }
       ]
     },
     "ietf-vn:virtual-network": {

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       "vn": [
         {
           "id": "1",
           "te-topology-identifier": {
             "topology-id": "abstract1"
           },
           "abstract-node": "192.0.2.1",
           "vn-member": [
             {
               "id": "104",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10101"
               },
               "dest": {
                 "ap": "404",
                 "vn-ap-id": "40401"
               },
               "connectivity-matrix-id": 10104
             },
             {
               "id": "107",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10101"
               },
               "dest": {
                 "ap": "707",
                 "vn-ap-id": "70701"
               },
               "connectivity-matrix-id": 10107
             },
             {
               "id": "204",
               "src": {
                 "ap": "202",
                 "vn-ap-id": "20201"
               },
               "dest": {
                 "ap": "404",
                 "vn-ap-id": "40401"
               },
               "connectivity-matrix-id": 10204
             },
             {
               "id": "308",
               "src": {
                 "ap": "303",

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                 "vn-ap-id": "30301"
               },
               "dest": {
                 "ap": "808",
                 "vn-ap-id": "80801"
               },
               "connectivity-matrix-id": 10308
             },
             {
               "id": "108",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10101"
               },
               "dest": {
                 "ap": "808",
                 "vn-ap-id": "80801"
               },
               "connectivity-matrix-id": 10108
             }
           ]
         },
         {
           "id": "2",
           "te-topology-identifier": {
             "topology-id": "abstract2"
           },
           "abstract-node": "192.0.2.2",
           "vn-member": [
             {
               "id": "105",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10102"
               },
               "dest": {
                 "ap": "505",
                 "vn-ap-id": "50502"
               },
               "connectivity-matrix-id": 20105
             }
           ]
         },
         {
           "id": "3",
           "te-topology-identifier": {
             "topology-id": "abstract3"
           },

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           "abstract-node": "192.0.2.3",
           "vn-member": [
             {
               "id": "106",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10103"
               },
               "dest": {
                 "ap": "606",
                 "vn-ap-id": "60603",
                 "multi-dest": true
               },
               "connectivity-matrix-id": 30106,
               "if-selected": false
             },
             {
               "id": "107",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10103"
               },
               "dest": {
                 "ap": "707",
                 "vn-ap-id": "70703",
                 "multi-dest": true
               },
               "connectivity-matrix-id": 30107,
               "if-selected": true
             },
             {
               "id": "108",
               "src": {
                 "ap": "101",
                 "vn-ap-id": "10103",
                 "multi-src": true
               },
               "dest": {
                 "ap": "808",
                 "vn-ap-id": "80803",
               },
               "connectivity-matrix-id": 30108,
               "if-selected": false
             },
             {
               "id": "308",
               "src": {
                 "ap": "303",

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                 "vn-ap-id": "30303",
                 "multi-src": true
               },
               "dest": {
                 "ap": "808",
                 "vn-ap-id": "80803"
               },
               "connectivity-matrix-id": 30308,
               "if-selected": true
             }
           ]
         }
       ]
     }
   }

B.2.  TE-topology JSON

   This section provides JSON examples of the various TE topology
   instances.

   The example in this section includes the following TE Topologies

   *  abstract1: a single node TE topology referenced by VN1.  We also
      show how disjointness (node, link, Shared Risk Link Group (SRLG))
      is supported in the example on the connectivity matrices.

   *  abstract2: a single node TE topology referenced by VN2 with
      underlay path.

   *  underlay: the topology with multiple nodes (in the underlay path
      of abstract2).  For brevity, the example includes only the node
      and other parameters are not included.

   *  abstract3: a single node TE topology referenced by VN3.

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-types": {
             "ietf-te-topology:te-topology": {}
           },
           "network-id": "example:abstract1",
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 0,
             "client-id": 0,
             "topology-id": "example:abstract1"

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           },
           "node": [
             {
               "node-id": "example:192.0.2.1",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:1-0-1",
                   "ietf-te-topology:te-tp-id": "203.0.113.11"
                 },
                 {
                   "tp-id": "example:1-0-2",
                   "ietf-te-topology:te-tp-id": "203.0.113.21"
                 },
                 {
                   "tp-id": "example:1-0-3",
                   "ietf-te-topology:te-tp-id": "203.0.113.31"
                 },
                 {
                   "tp-id": "example:1-0-4",
                   "ietf-te-topology:te-tp-id": "203.0.113.41"
                 },
                 {
                   "tp-id": "example:1-0-7",
                   "ietf-te-topology:te-tp-id": "203.0.113.71"
                 },
                 {
                   "tp-id": "example:1-0-8",
                   "ietf-te-topology:te-tp-id": "203.0.113.81"
                 }
               ],
               "ietf-te-topology:te-node-id": "192.0.2.1",
               "ietf-te-topology:te": {
                 "te-node-attributes": {
                   "domain-id": 1,
                   "is-abstract": [
                     null
                   ],
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "path-constraints": {
                       "te-bandwidth": {
                         "generic": "0x1p10"
                       },
                       "disjointness": "node link srlg"
                     },
                     "connectivity-matrix": [
                       {
                         "id": 10104,

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                         "from": {
                           "tp-ref": "example:1-0-1"
                         },
                         "to": {
                           "tp-ref": "example:1-0-4"
                         }
                       },
                       {
                         "id": 10107,
                         "from": {
                           "tp-ref": "example:1-0-1"
                         },
                         "to": {
                           "tp-ref": "example:1-0-7"
                         }
                       },
                       {
                         "id": 10204,
                         "from": {
                           "tp-ref": "example:1-0-2"
                         },
                         "to": {
                           "tp-ref": "example:1-0-4"
                         }
                       },
                       {
                         "id": 10308,
                         "from": {
                           "tp-ref": "example:1-0-3"
                         },
                         "to": {
                           "tp-ref": "example:1-0-8"
                         }
                       },
                       {
                         "id": 10108,
                         "from": {
                           "tp-ref": "example:1-0-1"
                         },
                         "to": {
                           "tp-ref": "example:1-0-8"
                         }
                       }
                     ]
                   }
                 }
               }
             }

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           ]
         },
         {
           "network-types": {
             "ietf-te-topology:te-topology": {}
           },
           "network-id": "example:abstract2",
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 0,
             "client-id": 0,
             "topology-id": "example:abstract2"
           },
           "node": [
             {
               "node-id": "example:192.0.2.2",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:2-0-1",
                   "ietf-te-topology:te-tp-id": "203.0.113.12"
                 },
                 {
                   "tp-id": "example:2-0-5",
                   "ietf-te-topology:te-tp-id": "203.0.113.52"
                 }
               ],
               "ietf-te-topology:te-node-id": "192.0.2.2",
               "ietf-te-topology:te": {
                 "te-node-attributes": {
                   "domain-id": 1,
                   "is-abstract": [
                     null
                   ],
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "underlay": {
                       "enabled": true
                     },
                     "path-constraints": {
                       "te-bandwidth": {
                         "generic": "0x1p10"
                       }
                     },
                     "optimizations": {
                       "objective-function": {
                         "objective-function-type":
                          "ietf-te-types:of-maximize-residual-bandwidth"
                       }
                     },

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                     "ietf-te-topology:connectivity-matrix": [
                       {
                         "id": 20105,
                         "from": {
                           "tp-ref": "example:2-0-1"
                         },
                         "to": {
                           "tp-ref": "example:2-0-5"
                         },
                         "underlay": {
                           "enabled": true,
                           "primary-path": {
                             "network-ref": "example:underlay",
                             "path-element": [
                               {
                                 "path-element-id": 1,
                                 "numbered-node-hop": {
                                   "node-id": "198.51.100.44",
                                   "hop-type": "strict"
                                 }
                               },
                               {
                                 "path-element-id": 2,
                                 "numbered-node-hop": {
                                   "node-id": "198.51.100.77",
                                   "hop-type": "strict"
                                 }
                               }
                             ]
                           }
                         }
                       }
                     ]
                   }
                 }
               }
             }
           ]
         },
         {
           "network-types": {
             "ietf-te-topology:te-topology": {}
           },
           "network-id": "example:underlay",
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 0,
             "client-id": 0,
             "topology-id": "example:underlay"

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           },
           "node": [
             {
               "node-id": "example:198.51.100.11",
               "ietf-te-topology:te-node-id": "198.51.100.11"
             },
             {
               "node-id": "example:198.51.100.22",
               "ietf-te-topology:te-node-id": "198.51.100.22"
             },
             {
               "node-id": "example:198.51.100.33",
               "ietf-te-topology:te-node-id": "198.51.100.33"
             },
             {
               "node-id": "example:198.51.100.44",
               "ietf-te-topology:te-node-id": "198.51.100.44"
             },
             {
               "node-id": "example:198.51.100.55",
               "ietf-te-topology:te-node-id": "198.51.100.55"
             },
             {
               "node-id": "example:198.51.100.66",
               "ietf-te-topology:te-node-id": "198.51.100.66"
             },
             {
               "node-id": "example:198.51.100.77",
               "ietf-te-topology:te-node-id": "198.51.100.77"
             },
             {
               "node-id": "example:198.51.100.88",
               "ietf-te-topology:te-node-id": "198.51.100.88"
             },
             {
               "node-id": "example:198.51.100.99",
               "ietf-te-topology:te-node-id": "198.51.100.99"
             }
           ]
         },
         {
           "network-types": {
             "ietf-te-topology:te-topology": {}
           },
           "network-id": "example:abstract3",
           "ietf-te-topology:te-topology-identifier": {
             "provider-id": 0,
             "client-id": 0,

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             "topology-id": "example:abstract3"
           },
           "node": [
             {
               "node-id": "example:192.0.2.3",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id": "example:3-0-1",
                   "ietf-te-topology:te-tp-id": "203.0.113.13"
                 },
                 {
                   "tp-id": "example:3-0-3",
                   "ietf-te-topology:te-tp-id": "203.0.113.33"
                 },
                 {
                   "tp-id": "example:3-0-6",
                   "ietf-te-topology:te-tp-id": "203.0.113.63"
                 },
                 {
                   "tp-id": "example:3-0-7",
                   "ietf-te-topology:te-tp-id": "203.0.113.73"
                 },
                 {
                   "tp-id": "example:3-0-8",
                   "ietf-te-topology:te-tp-id": "203.0.113.83"
                 }
               ],
               "ietf-te-topology:te-node-id": "192.0.2.3",
               "ietf-te-topology:te": {
                 "te-node-attributes": {
                   "domain-id": 3,
                   "is-abstract": [
                     null
                   ],
                   "connectivity-matrices": {
                     "is-allowed": true,
                     "path-constraints": {
                       "te-bandwidth": {
                         "generic": "0x1p10"
                       }
                     },
                     "connectivity-matrix": [
                       {
                         "id": 30107,
                         "from": {
                           "tp-ref": "example:3-0-1"
                         },
                         "to": {

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                           "tp-ref": "example:3-0-7"
                         }
                       },
                       {
                         "id": 30106,
                         "from": {
                           "tp-ref": "example:3-0-1"
                         },
                         "to": {
                           "tp-ref": "example:3-0-6"
                         }
                       },
                       {
                         "id": 30108,
                         "from": {
                           "tp-ref": "example:3-0-1"
                         },
                         "to": {
                           "tp-ref": "example:3-0-8"
                         }
                       },
                       {
                         "id": 30308,
                         "from": {
                           "tp-ref": "example:3-0-3"
                         },
                         "to": {
                           "tp-ref": "example:3-0-8"
                         }
                       }
                     ]
                   }
                 }
               }
             }
           ]
         }
       ]
     }
   }

Appendix C.  Contributors Addresses

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

   Peter Park
   KT
   Email: peter.park@kt.com

   Haomian Zheng
   Huawei Technologies
   Email: zhenghaomian@huawei.com

   Xian Zhang
   Huawei Technologies
   Email: zhang.xian@huawei.com

   Sergio Belotti
   Nokia
   Email: sergio.belotti@nokia.com

   Takuya Miyasaka
   KDDI
   Email: ta-miyasaka@kddi.com

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

Authors' Addresses

   Young Lee (editor)
   Samsung Electronics
   Email: younglee.tx@gmail.com

   Dhruv Dhody (editor)
   Huawei
   India
   Email: dhruv.ietf@gmail.com

   Daniele Ceccarelli
   Cisco
   Email: daniele.ietf@gmail.com

   Igor Bryskin
   Individual

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   Email: i_bryskin@yahoo.com

   Bin Yeong Yoon
   ETRI
   Email: byyun@etri.re.kr

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