RFC 9731 | VN YANG Data Model | March 2025
Lee, et al. | Standards Track | [Page]

Stream:
  Internet Engineering Task Force (IETF)
RFC:
  9731
Category:
  Standards Track
Published:
  March 2025
ISSN:
  2070-1721
Authors:
  Y. Lee, Ed.
  Samsung Electronics
  D. Dhody, Ed.
  Huawei
  D. Ceccarelli
  Cisco
  I. Bryskin
  Individual
  B. Yoon
  ETRI

# RFC 9731

# A YANG Data Model for Virtual Network (VN) Operations

## 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 were 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 (RFC 8453).¶

## Status of This Memo

This is an Internet Standards Track document.¶

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

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc9731.¶

## Copyright Notice

Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved.¶

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

## 1. Introduction

Abstraction and Control of TE Networks (ACTN) describes a set of management and control functions used to operate one or more Traffic Engineered (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 data model [RFC7950] generally applicable to any mode of VN operation. ACTN is the primary example of the usage of the VN YANG data model, but VN is 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. It can also work together with other customer service models such as the L3VPN Service Model (L3SM) [RFC8299], the L2VPN Service Model (L2SM) [RFC8466], and the L1 Connectivity Service Model (L1CSM) [L1CSM-YANG] to provide complete life-cycle service management and operations.¶

The YANG data 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 (VNAPs) 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 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 customized based on customer 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 (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 a 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 model [YANG-TE] will inevitably interact with the TE Topology model when setting up actual tunnels and Label Switched Paths (LSPs) under the tunnels.¶

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

The YANG data model for the CNC-MDSC Interface (CMI) is also known as the "customer service model" in [RFC8309]. The YANG data model discussed in this document is used to operate customer-driven VNs during the VN instantiation and computation as well as 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 and Conventions

This document borrows the following abbreviations from [RFC8453] and/or [RFC8795]:¶

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¶
LTP:
  Link Termination Point¶

This document borrows the terminology in Section 1.1 of [RFC7926], the term "Service Model" from [RFC8309], and the term "Connectivity Matrix" from [RFC8795].¶

Various examples in this document contain long lines that may be folded, as described in [RFC8792].¶

### 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.¶

Table 1: Prefixes and Corresponding YANG Modules
Prefix | YANG Module | Reference
--- | --- | ---
vn | ietf-vn | RFC 9731
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]

## 2. Use Case of VN YANG Data Model in the ACTN Context

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

           +-------+
           |  CNC  |
           +-------+
               |
               |    VN + TE Topology
               |
    +-----------------------+
    |         MDSC          |
    +-----------------------+

Figure 1: ACTN CMI

Both ACTN VN and TE Topology YANG data 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 VN is a customer view of the TE network. To recapitulate VN types from [RFC8453], a 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

Figure 2: VN Members (Type 1 VN)

Where L1, L2, L3, L4, L7, and L8 correspond to a Customer Endpoint (or AP).¶

This VN can be modeled as one abstract node representation as follows in Figure 3:¶

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

Figure 3: Abstract Node (Type 1 Topology)

Modeling a VN as one abstract node is the easiest way for customers to express their end-to-end connectivity as shown in Figure 3.¶

### 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. A Type 1 VN can be viewed as a higher-level abstraction of a Type 2 VN, which represents a single node abstract topology over the underlay topology and includes a mechanism to specify intended paths. These topologies could be mutually agreed upon between the CNC and the MDSC prior to VN creation or they 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)).¶

           +----------------------------------------------+
           |             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 4: Type 2 Topology

As shown in Figure 4, 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 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 YANG data models.¶

                +--------+                        +--------+
                |  CNC   |                        |  MDSC  |
                +--------+                        +--------+
                     |                                 |
                     |                                 |
    CNC POST TE Topo |  POST /nw:networks/nw:network/  |
    model (w/ 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 an
    model            |<--------------------------------| 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 5: Type 1 VN Illustration

### 3.2. Type 2 VN Illustration

For some VN members, the customer may want to "configure" an explicit path that connects its two endpoints. 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)

Figure 6: VN Members (Type 2 VN)

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

Case 1:¶

If the CNC creates the single abstract node topology, the message flow between the CNC and MDSC to instantiate this VN using a VN and TE Topology YANG data model would be as shown in the following diagram:¶

                +--------+                                +--------+
                |  CNC   |                                |  MDSC  |
                +--------+                                +--------+
                     |                                         |
                     |                                         |
    CNC POST TE Topo |  POST /nw:networks/nw:network/          |
    model (w/ 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        |
    model            |<----------------------------------------|
                     |                                         |
                     |                                         |
    CNC GET the      |  GET /virtual-network                   |
    VN YANG status   |---------------------------------------->|
                     |                                         |
                     |  HTTP 200 (VN with status)              |
                     |<----------------------------------------|
                     |                                         |

Figure 7: 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 YANG data models.¶

                +--------+                        +--------+
                |  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 (w/       |  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 8: 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 customized based on the requirements of the customer and configured at the MDSC.¶

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

#### 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. The customer access information could be added later.¶

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

## 4. VN YANG Data Model Usage

### 4.1. Customer View of VN

The VN YANG data model allows the definition of a customer view and allows the customer to communicate using the VN constructs as described in [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 data models.¶

This is similar to the benefits offered by a separate YANG data model for customer services described in [RFC8309], which states that service models do not make any assumptions 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 data model. In some other cases, the VN is not explicitly configured but is instead created automatically by the MDSC based on the customer service model and local policy; even in these cases, the VN YANG data 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

#### 4.3.1. VN Compute

The 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 ([YANG-TE]) does not provide the same functionality.¶

                +--------+                                +--------+
                |  CNC   |                                |  MDSC  |
                +--------+                                +--------+
                     |                                         |
                     |                                         |
    CNC POST TE Topo |  POST /nw:networks/nw:network/          |
    model (w/ 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       |                                         |
    referred TE-Topo |                                         |
                     |                                         |
                     |           HTTP 200 (Computed VN)        |
                     |<----------------------------------------|
                     |                                         |

Figure 9: VN Compute with Reference to TE Topology YANG Data Model

The VN compute RPC allows the optional inclusion of 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.¶

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

Figure 10: VN Compute

Regardless of whether the TE Topology model is referenced, the RPC 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: is used optionally in the RPC input at the VN-level and/or VN-member level. The VN-member level overrides the VN-level data including any constraints in the referenced abstract node in the TE topology.¶
- te-types:generic-path-optimization: is used optionally in the RPC input at the VN-level and/or VN-member level. The VN-member level overrides the VN-level data including any optimization in the referenced abstract node in the TE topology.¶
- vn member: identifies the VN member in both RPC input and output.¶
- vn-policy: 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. 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.¶

    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}?
         |  |  +---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
               |  +--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. Multiple Sources and Multiple Destinations

In creating a VN, the list of sources or destinations or both may not be predetermined 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 multiple sources and multiple destinations.¶

    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 data model can easily be augmented to support the mapping of VN to the services such as L3SM and L2SM as described in [TE-SERVICE-MAPPING].¶

The VN YANG data model can be extended to support telemetry, performance monitoring, and network autonomics as described in [TEAS-ACTN-PM].¶

Note that the VN YANG data model is tightly coupled with the TE Topology model [RFC8795]. Any underlay technology not supported by the TE Topology model in [RFC8795] is also not supported by the VN model. However, the VN 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.¶

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

### 4.5. Summary

This section summarizes the features of the VN YANG data model.¶

- Maintenance of APs and VNAPs along with the 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 data model.¶

    - Note that the VN type is not explicitly identified in the VN YANG data model, as the VN YANG data model is exactly the same for both VN Type 1 and VN Type 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 Data 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
      |        +--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
           |  |  |  +---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
           |  |  |  |     ...
           |  |  |  +---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 Data Model

The VN YANG data model is as follows:¶

    <CODE BEGINS> file "ietf-vn@2025-03-27.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
        "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>
         Editor:  Dhruv Dhody <dhruv.ietf@gmail.com>";
      description
        "This 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 TE Networks (ACTN)
         architecture where the CNC is the actor of a VN
         instantiation/modification/deletion as per RFC 8453.

         Copyright (c) 2025 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 9731; see the
         RFC itself for full legal notices.";

      revision 2025-03-27 {
        description
          "The initial version.";
        reference
          "RFC 9731: A YANG Data Model for Virtual Network (VN)
                     Operations";
      }

      /* Features */

      feature multi-src-dest {
        description
          "Support for selection of one source 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 a VN identifier.";
      }

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

      typedef vnm-id {
        type string {
          length "1..max";
        }
        description
          "A type definition for a 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
           to be unknown.";
      }

      /* identities */

      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
           CNCs 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.";
        }
        container src {
          description
            "The source of VN member.";
          leaf ap {
            type leafref {
              path "/access-point/ap/id";
            }
            description
              "A reference to the source AP.";
          }
          leaf vn-ap-id {
            type leafref {
              path "/access-point/ap[id=current()/../ap]/vn-ap"
                 + "/id";
            }
            description
              "A reference to the source VNAP.";
          }
          leaf multi-src {
            if-feature "multi-src-dest";
            type boolean;
            default "false";
            description
              "Is the source part of a multi-source, where
               only one of the sources is enabled?";
          }
        }
        container dest {
          description
            "The destination of the VN member.";
          leaf ap {
            type leafref {
              path "/access-point/ap/id";
            }
            description
              "A reference to the destination AP.";
          }
          leaf vn-ap-id {
            type leafref {
              path "/access-point/ap[id=current()/../ap]/"
                 + "vn-ap/id";
            }
            description
              "A reference to the destination VNAP.";
          }
          leaf multi-dest {
            if-feature "multi-src-dest";
            type boolean;
            default "false";
            description
              "Is the destination part of a 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 the 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)
           RFC 8795: YANG Data Model for Traffic Engineering (TE)
                     Topologies";
      }

      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 {
          key "id";
          description
            "The 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
                   must be TE enabled.";
              }
              description
                "A reference to the abstract node that represents
                 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 the 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 VNAPs 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 VN 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;
          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-source
                 or multi-destination 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 */

      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;
          }
          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-source or
                 multi-destination 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 that occurred
                   during VN compute.";
              }
              leaf error-timestamp {
                type yang:date-and-time;
                description
                  "Timestamp of the attempt.";
              }
              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 Network Configuration Access Control Model (NACM) [RFC8341] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.¶

The 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 on 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:¶

- ap: This list includes a set of sensitive data that influences how the APs 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¶
  - 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-source / multi-destination 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 has made the following allocation for a URI in the "ns" registry within the "IETF XML Registry" registry group [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 has made the following allocation for the VN YANG data model (see Section 5 in the "YANG Module Names" registry [RFC6020]:¶

name:
  ietf-vn¶
namespace:
  urn:ietf:params:xml:ns:yang:ietf-vn¶
prefix:
  vn¶
reference:
  RFC 9731¶

## 9. References

### 9.1. 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>.
[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>.

### 9.2. Informative References

[L1CSM-YANG]
  Lee, Y., Lee, K., Zheng, H., Gonzalez de Dios, O., 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>.
[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>.
[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>.
[RFC8792]
  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu, "Handling Long Lines in Content of Internet-Drafts and RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020, <https://www.rfc-editor.org/info/rfc8792>.
[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>.
[TE-SERVICE-MAPPING]
  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-17, 29 January 2025, <https://datatracker.ietf.org/doc/html/draft-ietf-teas-te-service-mapping-yang-17>.
[TEAS-ACTN-PM]
  Lee, Y., Dhody, D., Vilalta, R., King, D., and D. Ceccarelli, "YANG models for Virtual Network (VN)/TE Performance Monitoring Telemetry and Scaling Intent Autonomics", Work in Progress, Internet-Draft, draft-ietf-teas-actn-pm-telemetry-autonomics-14, 19 October 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-teas-actn-pm-telemetry-autonomics-14>.
[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-37, 9 October 2024, <https://datatracker.ietf.org/doc/html/draft-ietf-teas-yang-te-37>.

## Appendix A. Performance Constraints

At the creation of a VN, it is natural to provide VN-level constraints and optimization criteria. It should be noted that the VN YANG data model described in this document relies on the TE Topology model in [RFC8795] by using a reference to an abstract node to provide VN-level constraints and optimization criteria. 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; 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 the VN YANG data model and TE Topology YANG data model are used together to instantiate a VN.¶

The example in this section includes the following VNs:¶

- VN1 (Type 1): This VN maps to the single node topology abstract1 and consists 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): This VN 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 the abstract2 topology;¶
- 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 the 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
         ---                       ---                       ---

Figure 11: Example

Note that the VN YANG data model also includes the AP and VNAP, which shows various VNs 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",
            "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"
              }
            ]
          },
          {
            "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": {
        "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",
                  "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"
            },
            "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",
                  "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 an underlay path.¶
- underlay: the topology with multiple nodes (in the underlay path of abstract2). For brevity, the example includes only the node: 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"
            },
            "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,
                          "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"
                          }
                        }
                      ]
                    }
                  }
                }
              }
            ]
          },
          {
            "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"
                        }
                      },
                      "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"
            },
            "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,
              "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": {
                            "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"
                          }
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        ]
      }
    }

¶

## 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.¶

Thanks to:¶

- Andy Bierman for the YANGDIR review.¶

- Darren Dukes and Susan Hares for the RTGDIR review.¶

- Behcet Sarikaya for the GENART review.¶

- Bo Wu for the OPSDIR review.¶

- Shivan Sahib for the SECDIR review.¶

- Deb Cooley, Francesca Palombini, Gunter Van de Velde, and Mahesh Jethanandani for the IESG review.¶

## Contributors

## Authors' Addresses