Transport Network Slice YANG Data Model
draft-liu-teas-transport-network-slice-yang-00

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Network Working Group                                             X. Liu
Internet-Draft                                            Volta Networks
Intended status: Standards Track                             J. Tantsura
Expires: May 7, 2020                                     Apstra Networks
                                                              I. Bryskin
                                                              Individual
                                                            L. Contreras
                                                              Telefonica
                                                                   Q. Wu
                                                                  Huawei
                                                        November 4, 2019

                Transport Network Slice YANG Data Model
             draft-liu-teas-transport-network-slice-yang-00

Abstract

   This document describes a YANG data model for managing and
   controlling transport network slices.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 7, 2020.

Copyright Notice

   Copyright (c) 2019 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

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   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     1.2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Modeling Considerations . . . . . . . . . . . . . . . . . . .   3
     2.1.  Relationships to Related Topology Models  . . . . . . . .   3
     2.2.  Network Slice with TE . . . . . . . . . . . . . . . . . .   4
     2.3.  ACTN for Network Slicing  . . . . . . . . . . . . . . . .   5
   3.  Model Applicability . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Network Slicing by Virtualization . . . . . . . . . . . .   5
     3.2.  Network Slicing by TE Overlay . . . . . . . . . . . . . .   7
   4.  Model Tree Structure  . . . . . . . . . . . . . . . . . . . .   9
   5.  YANG Module . . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  19
   Appendix A.  Data Tree for the Example in Section 3.1.  . . . . .  21
     A.1.  Native Topology . . . . . . . . . . . . . . . . . . . . .  21
     A.2.  Network Slice Blue  . . . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Introduction

   This document defines a YANG [RFC7950] data model for for
   representing, managing, and controlling transport network slices.

   The defined data model is an interface between clients and providers
   for configurations and state retrievals, so as to support transport
   network slicing as a service.  Through this model, a client can learn
   the slicing capabilities and the available resources of the provider.
   A client can request or negotiate with a transport network slicing
   provider to create an instance.  The client can incrementally update
   its requirements on individual topology elements in the slice
   instance, and retrieve the operational states of these elements.
   With the help of other mechanisms and data models defined in IETF,
   the telemetry information can be published to the client.

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

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1.1.  Terminology

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

   The following terms are defined in [RFC7950] and are not redefined
   here:

   o  augment

   o  data model

   o  data node

1.2.  Tree Diagrams

   Tree diagrams used in this document follow the notation defined in
   [RFC8340].

2.  Modeling Considerations

   A transport network slice is modeled as network topology defined in
   [RFC8345], with augmentations.  A new network type "network-slice" is
   defined in this document.  When a network topology data instance
   contains the network-slice network type, it represents an instance of
   a transport network slice.

2.1.  Relationships to Related Topology Models

   There are several related YANG data models that have been defined in
   IETF.  Some of these are:

   Network Topology Model:
      Defined in [RFC8345].

   OTN Topology Model:
      Defined in [I-D.ietf-ccamp-otn-topo-yang].

   L2 Topology Model:
      Defined in [I-D.ietf-i2rs-yang-l2-network-topology].

   L3 Topology Model:
      Defined in [RFC8346].

   TE Topology Model:

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      Defined in [I-D.ietf-teas-yang-te-topo].

   Figure 1 shows the relationships among these models.  The box of
   dotted lines denotes the model defined in this document.

                        +------------------------+
                        |                        |
                        | Network Topology Model |
                        |        RFC 8345        |
                        +------------------------+
                                     |
         +-------------+-------------+-------------+-------------+
         |             |             |             |             |
         V             V             V             V             V
   +----------+  +----------+  +----------+  +----------+  ............
   |    OTN   |  |    L2    |  |    L3    |  |    TE    |  :  Network :
   | Topology |  | Topology |  | Topology |  | Topology |  :   Slice  :
   |   Model  |  |   Model  |  |   Model  |  |   Model  |  :   Model  :
   +----------+  +----------+  +----------+  +----------+  ''''''''''''

                       Figure 1: Model Relationships

2.2.  Network Slice with TE

   In many situations, a transport network slide needs to have TE
   (Traffic Engineering) capabilities to achieve certain network
   characteristics.  The TE Topology Model defined in
   [I-D.ietf-teas-yang-te-topo] can be used to make a transport network
   slice TE capable.  To achieve this, a transport network slice
   instance will be configured to have both "network-slice" and "te-
   topology" network types, taking advantage of the multiple inheritance
   capability featured by the network topology model [RFC8345].  The
   following diagram shows their relations.

        +--------------------+  +--------------------+
        | Network Slice      |  | TE Topology        |
        | ietf-network-slice |  | ietf-te-topology   |
        +--------------------+  +--------------------+
                   \                      /
                    \                    /
                     \                  /
                      v                v
                  +------------------------+
                  | Network Slice with TE  |
                  |                        |
                  +------------------------+

                      Figure 2: Network Slice with TE

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   This method can be applied to other types of network topology models
   too.  For example, when a network topology instance is configured to
   have the types of "network-slice" defined in this document, "te-
   topology" defined in [I-D.ietf-teas-yang-te-topo], and "l3-unicast-
   topology" defined in [RFC8346], this network topology instance
   becomes a transport network slice instance that can perform layer 3
   traffic engineering.

2.3.  ACTN for Network Slicing

   Since ACTN topology data models are based on the network topology
   model defined in [RFC8345], the augmentations defined in this
   document are effective augmentations to the ACTN topology data
   models, resulting in making the ACTN framework [RFC8453] and data
   models [I-D.ietf-teas-actn-yang] capable of slicing networks with the
   required network characteristics.

3.  Model Applicability

   There are many technologies to achieve transport network slicing.
   The data model defined in this document can be applied to a wide
   ranges of cases.  This section describes how this data model is
   applied to a few cases.

3.1.  Network Slicing by Virtualization

   In the case shown in Figure 3, node virtualization is used to
   separate and allocate resources in physical devices.  Two virtual
   routers VR1 and VR2 are created over physical router R1.  Each of the
   virtual routers takes a portion of the resources such as ports and
   memory in the physical router.  Depending on the requirements and the
   implementations, they may share certain resources such as processors,
   ASICs, and switch fabric.

   As an example, Appendix A. shows the JSON encoded data instances of
   the native topology and the customized topology for Network Slice
   Blue.

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       Client Topology                     Client Topology
       Network Slice Blue                  Network Slice Red
                            +---+         +---+      +---+
                       -----|R3 |---   ---|R2 |------|R3 |
                      /     +---+         +---+      +---+
      +---+      +---+                                    \     +---+
   ---|R1 |------|R2 |                                     -----|R4 |---
      +---+      +---+                                          +---+

                                 Clients
   ---------------------------------------------------------------------
                                 Provider

        Customized Topology
        Provider Network with Virtual Devices

        Network Slice Blue: VR1, VR3, VR5         +---+
                                        ----------|VR5|------
                                       /          +---+
                    +---+         +---+
              ------|VR1|---------|VR3|
                    +---+         +---+
              ------|VR2|---------|VR4|
                    +---+         +---+
                                       \          +---+
                                        ----------|VR6|------
        Network Slice Red: VR2, VR4, VR6          +---+

                                 Virtual Devices
   ---------------------------------------------------------------------
                                 Physical Devices

        Native Topology
        Provider Network with Physical Devices
                                                  +---+
                                        ----------|R3 |------
                                       /          +---+
                    +---+         +---+
              ======|R1 |=========|R2 |
                    +---+         +---+
                                       \          +---+
                                        ----------|R4 |------
                                                  +---+

                Figure 3: Network Slicing by Virtualization

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3.2.  Network Slicing by TE Overlay

   Figure 5 shows a case where TE (Traffic Engineering) overlay is
   applied to achieve logically separated client transport network
   slices.  In the underlay TE capable network, TE tunnels are
   established to support the TE links in the overlay network.  These
   links and tunnels maintain the characteristics required by the
   clients.  The provider selects the proper logical nodes and links in
   the overlay network, assigns them to specific transport network
   slices, and uses the data model defined in this document to send the
   results to the clients.

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       Client Topology                     Client Topology
       Network Slice Blue                  Network Slice Red
                            +---+         +---+      +---+
                       -----|R3 |---   ---|R2 |------|R3 |
                      /     +---+         +---+      +---+
      +---+      +---+                                    \     +---+
   ---|R1 |------|R2 |                                     -----|R4 |---
      +---+      +---+                                          +---+

                                 Clients
   ---------------------------------------------------------------------
                                 Provider

        Customized Topology
        Provider Network with TE Isolation

        Network Slice Blue: R1, R2, R3
                                                  +---+
                                        ----------|R3 |------
                                       /          +---+
                    +---+         +---+
              ======|R1 |=========|R2 |
                    +---+         +---+
                                       \          +---+
                                        ----------|R4 |------
                                                  +---+
        Network Slice Red: R1, R2, R4

                                  Overlay
   ---------------------------------------------------------------------
                                  Underlay

        Native Topology
        Provider Network with TE Tunnels
                                                  +---+
       TE Tunnel for Network Slice Blue ----------|R3 |------
                      @@@@@@@@@@@@@@   /          +---+
                    +---+  +---+  +---+
              ======|R1 |--|R5 |--|R2 |
                    +---+  +---+  +---+
                      ##############   \          +---+
       TE Tunnel for Network Slice Red  ----------|R4 |------
                                                  +---+

                  Figure 4: Network Slicing by TE Overlay

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4.  Model Tree Structure

   module: ietf-network-slice
     augment /nw:networks/nw:network/nw:network-types:
       +--rw network-slice!
     augment /nw:networks/nw:network:
       +--rw network-slice
          +--rw optimization-criterion?   identityref
          +--rw delay-tolerance?          boolean
          +--rw periodicity*              uint64
          +--rw isolation-level?          identityref
     augment /nw:networks/nw:network/nw:node:
       +--rw network-slice
          +--rw isolation-level?   identityref
          +--rw compute-node-id?   string
          +--rw storage-id?        string
     augment /nw:networks/nw:network/nt:link:
       +--rw network-slice
          +--rw delay-tolerance?   boolean
          +--rw periodicity*       uint64
          +--rw isolation-level?   identityref

5.  YANG Module

   This module references [RFC8345], [I-D.ietf-teas-yang-te-types], and
   [GSMA-NS-Template]

   <CODE BEGINS> file "ietf-network-slice@2019-10-15.yang"
   module ietf-network-slice {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-network-slice";
     prefix "ns";

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

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       reference
         "I-D.ietf-teas-yang-te-types: Traffic Engineering Common YANG
          Types";
     }

     organization
       "IETF Traffic Engineering Architecture and Signaling (TEAS)
        Working Group";

     contact
       "WG Web:   <http://tools.ietf.org/wg/teas/>
        WG List:  <mailto:teas@ietf.org>

        Editor:   Xufeng Liu
                  <mailto:xufeng.liu.ietf@gmail.com>

        Editor:   Jeff Tantsura
                  <mailto:jefftant.ietf@gmail.com>

        Editor:   Igor Bryskin
                  <mailto:i_bryskin@yahoo.com>

        Editor:   Luis Miguel Contreras Murillo
                  <mailto:luismiguel.contrerasmurillo@telefonica.com>

        Editor:   Qin Wu
                  <mailto:bill.wu@huawei.com>
       ";

     description
       "YANG data model for representing and managing network
        slices.

        Copyright (c) 2019 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 Simplified BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (http://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 2019-10-15 {
       description "Initial revision";

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       reference
         "RFC XXXX: YANG Data Model for Network Slices";
     }

     /*
      * Identities
      */
     identity isolation-level {
       description
         "Base identity for the isolation-level.";
       reference
         "GSMA-NS-Template: Generic Network Slice Template,
          Version 1.0.";
     }
     identity no-isolation {
       base isolation-level;
       description
         "Network slices are not separated.";
     }
     identity physical-isolation {
       base isolation-level;
       description
         "Network slices are physically separated (e.g. different rack,
          different hardware, different location, etc.).";
     }
     identity logical-isolation {
       base isolation-level;
       description
         "Network slices are logically separated.";
     }
     identity process-isolation {
       base physical-isolation;
       description
         "Process and threads isolation.";
     }
     identity physical-memory-isolation {
       base physical-isolation;
       description
         "Process and threads isolation.";
     }
     identity physical-network-isolation {
       base physical-isolation;
       description
         "Process and threads isolation.";
     }
     identity virtual-resource-isolation {
       base logical-isolation;
       description

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         "A network slice has access to specific range of resources
          that do not overlap with other network slices
          (e.g. VM isolation).";
     }
     identity network-functions-isolation {
       base logical-isolation;
       description
         "NF (Network Function) is dedicated to the network slice, but
          virtual resources are shared.";
     }
     identity service-isolation {
       base logical-isolation;
       description
         "NSC data are isolated from other NSCs, but virtual
          resources and NFs are shared.";
     }

     /*
      * Groupiings
      */
     grouping network-slice-topology-attributes {
       description "Network Slice topology scope attributes.";
       container network-slice {
         description
           "Containing Network Slice attributes.";
         leaf optimization-criterion {
           type identityref {
             base te-types:objective-function-type;
           }
           description
             "Optimization criterion applied to this topology.";
         }
         leaf delay-tolerance {
           type boolean;
           description
             "'true' if is not too critical how long it takes to deliver
              the amount of data.";
           reference
             "GSMA-NS-Template: Generic Network Slice Template,
              Version 1.0.";
         }
         leaf-list periodicity {
           type uint64;
           units seconds;
           description
             "A list of periodicities supported by the network slice.";
           reference
             "GSMA-NS-Template: Generic Network Slice Template,

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              Version 1.0.";
         }
         leaf isolation-level {
           type identityref {
             base isolation-level;
           }
           description
             "A network slice instance may be fully or partly, logically
              and/or physically, isolated from another network slice
              instance. This attribute describes different types of
              isolation:";
         }
       } // network-slice
     } // network-slice-topology-attributes

     grouping network-slice-node-attributes {
       description "Network Slice node scope attributes.";
       container network-slice {
         description
           "Containing Network Slice attributes.";
         leaf isolation-level {
           type identityref {
             base isolation-level;
           }
           description
             "A network slice instance may be fully or partly, logically
              and/or physically, isolated from another network slice
              instance. This attribute describes different types of
              isolation:";
         }
         leaf compute-node-id {
           type string;
           description
             "Reference to a compute node instance specified in
              a data model specifying the computing resources.";
         }
         leaf storage-id {
           type string;
           description
             "Reference to a storage instance specified in
              a data model specifying the storage resources.";
         }
       } // network-slice
     } // network-slice-node-attributes

     grouping network-slice-link-attributes {
       description "Network Slice link scope attributes";
       container network-slice {

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         description
           "Containing Network Slice attributes.";
         leaf delay-tolerance {
           type boolean;
           description
             "'true' if is not too critical how long it takes to deliver
              the amount of data.";
           reference
             "GSMA-NS-Template: Generic Network Slice Template,
              Version 1.0.";
         }
         leaf-list periodicity {
           type uint64;
           units seconds;
           description
             "A list of periodicities supported by the network slice.";
           reference
             "GSMA-NS-Template: Generic Network Slice Template,
              Version 1.0.";
         }
         leaf isolation-level {
           type identityref {
             base isolation-level;
           }
           description
             "A network slice instance may be fully or partly, logically
              and/or physically, isolated from another network slice
              instance. This attribute describes different types of
              isolation:";
         }
       } // network-slice
     } // network-slice-link-attributes

     /*
      * Data nodes
      */
     augment "/nw:networks/nw:network/nw:network-types" {
       description
         "Defines the Network Slice topology type.";
       container network-slice {
         presence "Indicates Network Slice topology";
         description
           "Its presence identifies the Network Slice type.";
       }
     }

     augment "/nw:networks/nw:network" {
       when "nw:network-types/ns:network-slice" {

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         description "Augment only for Network Slice topology.";
       }
       description "Augment topology configuration and state.";
       uses network-slice-topology-attributes;
     }

     augment "/nw:networks/nw:network/nw:node" {
       when "../nw:network-types/ns:network-slice" {
         description "Augment only for Network Slice topology.";
       }
       description "Augment node configuration and state.";
       uses network-slice-node-attributes;
     }

     augment "/nw:networks/nw:network/nt:link" {
       when "../nw:network-types/ns:network-slice" {
         description "Augment only for Network Slice topology.";
       }
       description "Augment link configuration and state.";
       uses network-slice-link-attributes;
     }

   }
   <CODE ENDS>

6.  IANA Considerations

   RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
   actual RFC number (and remove this note).

   This document registers the following namespace URIs in the IETF XML
   registry [RFC3688]:

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

   This document registers the following YANG modules in the YANG Module
   Names registry [RFC6020]:

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   --------------------------------------------------------------------
   name:         ietf-l3-te-topology
   namespace:    urn:ietf:params:xml:ns:yang:ietf-network-slice
   prefix:       ns
   reference:    RFC XXXX
   --------------------------------------------------------------------

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.

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

   /nw:networks/nw:network/nw:network-types/ns:network-slice
      This subtree specifies the network slice type.  Modifying the
      configurations can make network slice type invalid and cause
      interruption to transport network slices.

   /nw:networks/nw:network/ns:network-slice
      This subtree specifies the topology-wide configurations.
      Modifying the configurations here can cause traffic
      characteristics changed in this transport network slice and
      related networks.

   /nw:networks/nw:network/nw:node/ns:network-slice
      This subtree specifies the configurations of the nodes in a
      transport network slice.  Modifying the configurations in this
      subtree can change the traffic characteristics on this node and
      the related networks.

   /nw:networks/nw:network/nt:link/ns:network-slice

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      This subtree specifies the configurations of the links in a
      transport network slice.  Modifying the configurations in this
      subtree can change the traffic characteristics on this link and
      the related networks.

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

   /nw:networks/nw:network/nw:network-types/ns:network-slice
      Unauthorized access to this subtree can disclose the network slice
      type.

   /nw:networks/nw:network/ns:network-slice
      Unauthorized access to this subtree can disclose the topology-wide
      states.

   /nw:networks/nw:network/nw:node/ns:network-slice
      Unauthorized access to this subtree can disclose the operational
      state information of the nodes in a transport network slice.

   /nw:networks/nw:network/nt:link/ns:network-slic
      Unauthorized access to this subtree can disclose the operational
      state information of the links in a transport network slice.

8.  Acknowledgements

   The TEAS Network Slicing Design Team (NSDT) members included Aijun
   Wang, Dong Jie, Eric Gray, Jari Arkko, Jeff Tantsura, John E Drake,
   Luis M.  Contreras, Rakesh Gandhi, Ran Chen, Reza Rokui, Ricard
   Vilalta, Ron Bonica, Sergio Belotti, Tomonobu Niwa, Xuesong Geng, and
   Xufeng Liu.

9.  References

9.1.  Normative References

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

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

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   [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>.

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

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

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

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

   [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>.

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

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   [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>.

   [I-D.ietf-teas-yang-te-types]
              Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin,
              "Traffic Engineering Common YANG Types", draft-ietf-teas-
              yang-te-types-11 (work in progress), October 2019.

   [I-D.ietf-teas-yang-te-topo]
              Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
              O. Dios, "YANG Data Model for Traffic Engineering (TE)
              Topologies", draft-ietf-teas-yang-te-topo-22 (work in
              progress), June 2019.

   [GSMA-NS-Template]
              GSM Association, "Generic Network Slice Template, Version
              1.0",  NG.116, May 2019.

9.2.  Informative References

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

   [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>.

   [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>.

   [I-D.ietf-ccamp-otn-topo-yang]
              Zheng, H., Guo, A., Busi, I., Sharma, A., Liu, X.,
              Belotti, S., Xu, Y., Wang, L., and O. Dios, "A YANG Data
              Model for Optical Transport Network Topology", draft-ietf-
              ccamp-otn-topo-yang-08 (work in progress), September 2019.

   [I-D.ietf-i2rs-yang-l2-network-topology]
              Dong, J., Wei, X., WU, Q., Boucadair, M., and A. Liu, "A
              YANG Data Model for Layer-2 Network Topologies", draft-
              ietf-i2rs-yang-l2-network-topology-12 (work in progress),
              October 2019.

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   [I-D.ietf-teas-actn-yang]
              Lee, Y., Zheng, H., Ceccarelli, D., Yoon, B., Dios, O.,
              Shin, J., and S. Belotti, "Applicability of YANG models
              for Abstraction and Control of Traffic Engineered
              Networks", draft-ietf-teas-actn-yang-04 (work in
              progress), August 2019.

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Appendix A.  Data Tree for the Example in Section 3.1.

A.1.  Native Topology

   This section contains an example of an instance data tree in the JSON
   encoding [RFC7951].  The example instantiates "ietf-network" for the
   native topology depicted in Figure 3.

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-id":"example-native-topology",
           "network-types": {
           },
           "node": [
             {
               "node-id":"R1",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"1-0-1"
                 },
                 {
                   "tp-id":"1-0-2"
                 },
                 {
                   "tp-id":"1-2-1"
                 },
                 {
                   "tp-id":"1-2-2"
                 }
               ]
             },
             {
               "node-id":"R2",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"2-1-1"
                 },
                 {
                   "tp-id":"2-1-2"
                 },
                 {
                   "tp-id":"2-3-1"
                 },
                 {
                   "tp-id":"2-4-1"
                 }

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               ]
             },
             {
               "node-id":"R3",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"3-0-1"
                 },
                 {
                   "tp-id":"3-2-1"
                 }
               ]
             },
             {
               "node-id":"R4",
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"4-0-1"
                 },
                 {
                   "tp-id":"4-2-1"
                 }
               ]
             }
           ],
           "ietf-network-topology:link": [
             {
               "link-id":"R1,1-0-1,,",
               "source": {
                 "source-node":"R1",
                 "source-tp":"1-0-1"
               }
             },
             {
               "link-id":",,R1,1-0-1",
               "destination": {
                 "dest-node":"R1",
                 "dest-tp":"1-0-1"
               }
             },
             {
               "link-id":"R1,1-0-2,,",
               "source": {
                 "source-node":"R1",
                 "source-tp":"1-0-2"
               }
             },
             {

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               "link-id":",,R1,1-0-2",
               "destination": {
                 "dest-node":"R1",
                 "dest-tp":"1-0-2"
               }
             },
             {
               "link-id":"R1,1-2-1,R2,2-1-1",
               "source": {
                 "source-node":"R1",
                 "source-tp":"1-2-1"
               },
               "destination": {
                 "dest-node":"R2",
                 "dest-tp":"2-1-1"
               }
             },
             {
               "link-id":"R2,2-1-1,R1,1-2-1",
               "source": {
                 "source-node":"R2",
                 "source-tp":"2-1-1"
               },
               "destination": {
                 "dest-node":"R1",
                 "dest-tp":"1-2-1"
               }
             },
             {
               "link-id":"R1,1-2-2,R2,2-1-2",
               "source": {
                 "source-node":"R1",
                 "source-tp":"1-2-2"
               },
               "destination": {
                 "dest-node":"R2",
                 "dest-tp":"2-1-2"
               }
             },
             {
               "link-id":"R2,2-1-2,R1,1-2-2",
               "source": {
                 "source-node":"R2",
                 "source-tp":"2-1-2"
               },
               "destination": {
                 "dest-node":"R1",
                 "dest-tp":"1-2-2"

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               }
             },
             {
               "link-id":"R2,2-3-1,R3,3-2-1",
               "source": {
                 "source-node":"R2",
                 "source-tp":"2-3-1"
               },
               "destination": {
                 "dest-node":"R3",
                 "dest-tp":"3-2-1"
               }
             },
             {
               "link-id":"R3,3-2-1,R2,2-3-1",
               "source": {
                 "source-node":"R3",
                 "source-tp":"3-2-1"
               },
               "destination": {
                 "dest-node":"R2",
                 "dest-tp":"2-3-1"
               }
             },
             {
               "link-id":"R2,2-4-1,R4,4-2-1",
               "source": {
                 "source-node":"R2",
                 "source-tp":"2-4-1"
               },
               "destination": {
                 "dest-node":"R4",
                 "dest-tp":"4-2-1"
               }
             },
             {
               "link-id":"R4,4-2-1,R2,2-4-1",
               "source": {
                 "source-node":"R4",
                 "source-tp":"4-2-1"
               },
               "destination": {
                 "dest-node":"R2",
                 "dest-tp":"2-4-1"
               }
             },
             {
               "link-id":"R3,3-0-1,,",

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               "source": {
                 "source-node":"R3",
                 "source-tp":"3-0-1"
               }
             },
             {
               "link-id":",,R3,3-0-1",
               "destination": {
                 "dest-node":"R3",
                 "dest-tp":"3-0-1"
               }
             },
             {
               "link-id":"R4,4-0-1,,",
               "source": {
                 "source-node":"R4",
                 "source-tp":"4-0-1"
               }
             },
             {
               "link-id":",,R4,4-0-1",
               "destination": {
                 "dest-node":"R4",
                 "dest-tp":"4-0-1"
               }
             }
           ]
         }
       ]
     }
   }

A.2.  Network Slice Blue

   This section contains an example of an instance data tree in the JSON
   encoding [RFC7951].  The example instantiates "ietf-network-slice"
   for the topology customized for Network Slice Blue depicted in
   Figure 3.

   {
     "ietf-network:networks": {
       "network": [
         {
           "network-id":"example-customized-blue-topology",
           "network-types": {
             "ietf-network-slice:network-slice": {

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             }
           },
           "supporting-network": [
             {
               "network-ref":"example-native-topology"
             }
           ],
           "node": [
             {
               "node-id":"VR1",
               "supporting-node": [
                 {
                   "network-ref":"example-native-topology",
                   "node-ref":"R1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-memory-isolation"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"1-0-1"
                 },
                 {
                   "tp-id":"1-3-1"
                 }
               ]
             },
             {
               "node-id":"VR3",
               "supporting-node": [
                 {
                   "network-ref":"example-native-topology",
                   "node-ref":"R2"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-memory-isolation"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"3-1-1"
                 },
                 {
                   "tp-id":"3-5-1"
                 }

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               ]
             },
             {
               "node-id":"VR5",
               "supporting-node": [
                 {
                   "network-ref":"example-native-topology",
                   "node-ref":"R3"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-memory-isolation"
               },
               "ietf-network-topology:termination-point": [
                 {
                   "tp-id":"5-3-1"
                 },
                 {
                   "tp-id":"5-0-1"
                 }
               ]
             }
           ],
           "ietf-network-topology:link": [
             {
               "link-id":"VR1,1-0-1,,",
               "source": {
                 "source-node":"VR1",
                 "source-tp":"1-0-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R1,1-0-1,,"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":",,VR1,1-0-1",
               "destination": {
                 "dest-node":"VR1",
                 "dest-tp":"1-0-1"
               },

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               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":",,R1,1-0-1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":"VR1,1-3-1,VR3,3-1-1",
               "source": {
                 "source-node":"VR1",
                 "source-tp":"1-3-1"
               },
               "destination": {
                 "dest-node":"VR3",
                 "dest-tp":"3-1-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R1,1-2-1,R2,2-1-1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":"VR3,3-1-1,VR1,1-3-1",
               "source": {
                 "source-node":"VR3",
                 "source-tp":"3-1-1"
               },
               "destination": {
                 "dest-node":"R1",
                 "dest-tp":"1-3-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R2,2-1-1,R1,1-2-1"
                 }
               ],

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               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":"VR3,3-5-1,VR5,5-3-1",
               "source": {
                 "source-node":"VR3",
                 "source-tp":"3-5-1"
               },
               "destination": {
                 "dest-node":"VR5",
                 "dest-tp":"5-3-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R2,2-3-1,R3,3-2-1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":"VR5,5-3-1,VR3,3-5-1",
               "source": {
                 "source-node":"VR5",
                 "source-tp":"5-3-1"
               },
               "destination": {
                 "dest-node":"VR3",
                 "dest-tp":"3-5-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R3,3-2-1,R2,2-3-1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {

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               "link-id":"VR5,5-0-1,,",
               "source": {
                 "source-node":"VR5",
                 "source-tp":"5-0-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":"R3,3-0-1,,"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             },
             {
               "link-id":",,VR5,5-0-1",
               "destination": {
                 "dest-node":"VR5",
                 "dest-tp":"5-0-1"
               },
               "supporting-link": [
                 {
                   "network-ref":"example-native-topology",
                   "link-ref":",,R3,3-0-1"
                 }
               ],
               "ietf-network-slice:network-slice": {
                 "isolation-level":
                 "ietf-network-slice:physical-network-isolation"
               }
             }
           ],
           "ietf-network-slice:network-slice": {
             "optimization-criterion":
             "ietf-te-types:of-minimize-cost-path",
             "isolation-level":
             "ietf-network-slice:physical-isolation"
           }
         }
       ]
     }
   }

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Authors' Addresses

   Xufeng Liu
   Volta Networks

   EMail: xufeng.liu.ietf@gmail.com

   Jeff Tantsura
   Apstra Networks

   EMail: jefftant.ietf@gmail.com

   Igor Bryskin
   Individual

   EMail: i_bryskin@yahoo.com

   Luis Miguel Contreras Murillo
   Telefonica

   EMail: luismiguel.contrerasmurillo@telefonica.com

   Qin Wu
   Huawei

   EMail: bill.wu@huawei.com

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