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YANG Data Model for Scheduled Attributes
draft-ietf-tvr-schedule-yang-01

Document Type Active Internet-Draft (tvr WG)
Authors Yingzhen Qu , Acee Lindem , Eric Kinzie , Don Fedyk , Marc Blanchet
Last updated 2024-07-06
Replaces draft-united-tvr-schedule-yang
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status (None)
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Mar 2025
Data Model
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draft-ietf-tvr-schedule-yang-01
Internet                                                           Y. Qu
Internet-Draft                                    Futurewei Technologies
Intended status: Standards Track                               A. Lindem
Expires: 7 January 2025                                        E. Kinzie
                                                                D. Fedyk
                                                 LabN Consulting, L.L.C.
                                                             M. Blanchet
                                                                Viagenie
                                                             6 July 2024

                YANG Data Model for Scheduled Attributes
                    draft-ietf-tvr-schedule-yang-01

Abstract

   The YANG model in this document includes three modules, and can be
   used to manage network resources and topologies with scheduled
   attributes, such as predictable link loss and link connectivity as a
   function of time.  The intent is to have this information be utilized
   by Time-Variant Routing systems.

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 7 January 2025.

Copyright Notice

   Copyright (c) 2024 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

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

Table of Contents

   1.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Design of the model . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Schedule Definitions  . . . . . . . . . . . . . . . . . .   3
     3.2.  TVR Node YANG Module  . . . . . . . . . . . . . . . . . .   4
     3.3.  TVR Topology YANG Module  . . . . . . . . . . . . . . . .   4
   4.  TVR YANG Trees  . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  TVR Node YANG Tree  . . . . . . . . . . . . . . . . . . .   4
     4.2.  TVR Topology YANG Tree  . . . . . . . . . . . . . . . . .   6
   5.  TVR Schedule YANG Modules . . . . . . . . . . . . . . . . . .   7
     5.1.  TVR Schedule YANG Module  . . . . . . . . . . . . . . . .   7
     5.2.  TVR Schedule Node Module  . . . . . . . . . . . . . . . .  10
     5.3.  TVR Network Topology Module . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  19
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  19
   10. Informative References  . . . . . . . . . . . . . . . . . . .  20
   Appendix A.  Example: Add a scheduled cost to OSPF interface  . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Overview

   YANG [RFC7950] is a data definition language used to define the
   contents of a conceptual data store that allows networked devices to
   be managed using NETCONF [RFC6241].  YANG is proving relevant beyond
   its initial confines, as bindings to other interfaces (e.g., ReST)
   and encodings other than XML (e.g., JSON) are being defined.
   Furthermore, YANG data models can be used as the basis for
   implementation of other interfaces, such as CLI and programmatic
   APIs.

   In some network scenarios, it's possible to predict the times at
   which one router will be able to establish a link with another
   router.  Links can be predictably lost and re-established, and
   neighbors may change as a function of time.  For examples of such
   networks and scenarios, please reference TVR (Time-Variant Routing)
   Use Cases [I-D.ietf-tvr-use-cases].

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   The YANG model in this document can be used to manage network
   resources and topologies with scheduled attributes.  There are three
   YANG modules in this document.

   Module ietf-tvr-schedule.yang contains the schedule YANG definitions.
   Module ietf-tvr-topology.yang defines a network topology with time-
   variant availability.  Module ietf-tvr-node.yang is to be used to
   manage scheduled attributes of a single node.

   The YANG modules in this document conform to the Network Management
   Datastore Architecture (NMDA) [RFC8342].

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119] [RFC8174].

2.  Tree Diagrams

   This document uses the graphical representation of data models
   defined in [RFC8340].

3.  Design of the model

3.1.  Schedule Definitions

   Module ietf-tvr-schedule.yang contains schedule definitions that can
   be used by other modules.

   The grouping "tvr-schedule" consists of a list of schedules, and each
   schedule is either a single time period or recurring time periods.
   For each schedule instance, it utilizes the groupings "period-of-
   time" and "recurrence-utc" as defined in
   [I-D.ietf-netmod-schedule-yang].

   The container "attr-value" is a place holder for a module that uses
   the "tvr-schedule", where attribute values can be augmented.

   When an attribute's schedule ends, the "value-default" SHOULD be
   used, if present.

   The following figure provides an illustration of two attributes and
   their scheduled value changes.  The attributes A1 and A2 take on
   different values at different times.  The attribute A1 will take on
   the value v1 from the time t0 until t1, the value v2 from t1 until
   t2, and v3 from t2 until t3.  The attribute A2 will take on the value
   vv1 from time t0 until t1 and vv2 from v1 until v3.

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   Attributes
             +-------------------+----------+------+
         A1  |       v1          |   v2     |  v3  |
             +-------------------+----------+------+
         A2  |      vv1          |      vv2        |
             +-------------------+-----------------+
            t0                  t1        t2      t3
                            Time

                     Figure 1: Time Varying Properties

3.2.  TVR Node YANG Module

   Module ietf-tvr-node.yang is a device model and designed to manage a
   single node with scheduled attributes.

   Each node has scheduled power at the node level.  At the interface
   level, a node has a list of interfaces, and each interface has its
   own schedule for availability/power up and down, as well as scheduled
   bandwidth.

3.3.  TVR Topology YANG Module

   Module ietf-tvr-topology.yang describes a network topology with a
   time-variant availability schedule.

   The module has a list of nodes, identified by a unique "node-id".
   Each node has a list of links.  Links are modeled as unidirectional.
   Link availability is described from the viewpoint of a particular
   source node (the transmitting node) and beginning at a particular
   time.  Each link in the list contains the range of times during which
   it is available.

   The "source-link-id" is a string and used to identify a link as
   viewed from the source-node.  Bandwidth and delay are predicted link
   attributes.  Delay is the link propagation time and does not include
   any queuing delays.

4.  TVR YANG Trees

4.1.  TVR Node YANG Tree

   The following figure shows the tree diagram of the TVR Node
   scheduling.

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module: ietf-tvr-node
  +--rw node-schedule
     +--rw node-id?               yang:dotted-quad
     +--rw node-power-schedule
     |  +--rw power-default?   boolean
     |  +--rw schedules* [schedule-id]
     |     +--rw schedule-id                     uint32
     |     +--rw (schedule-type)?
     |     |  +--:(period)
     |     |  |  +--rw period-description?       string
     |     |  |  +--rw period-start              yang:date-and-time
     |     |  |  +--rw time-zone-identifier?     sys:timezone-name
     |     |  |  +--rw (period-type)?
     |     |  |     +--:(explicit)
     |     |  |     |  +--rw period-end?         yang:date-and-time
     |     |  |     +--:(duration)
     |     |  |        +--rw duration?           duration
     |     |  +--:(recurrence)
     |     |     +--rw recurrence-first
     |     |     |  +--rw utc-start-time?   yang:date-and-time
     |     |     |  +--rw duration?         uint32
     |     |     +--rw (recurrence-bound)?
     |     |     |  +--:(until)
     |     |     |  |  +--rw utc-until?          yang:date-and-time
     |     |     |  +--:(count)
     |     |     |     +--rw count?              uint32
     |     |     +--rw recurrence-description?   string
     |     |     +--rw frequency                 identityref
     |     |     +--rw interval?                 uint32
     |     +--rw attr-value
     |        +--rw power-state?   boolean
     +--rw interface-schedule
        +--rw interfaces* [name]
           +--rw name                  union
           +--rw default-available?    boolean
           +--rw default-bandwidth?    yang:gauge64
           +--rw attribute-schedule
              +--rw schedules* [schedule-id]
                 +--rw schedule-id                     uint32
                 +--rw (schedule-type)?
                 |  +--:(period)
                 |  |  +--rw period-description?       string
                 |  |  +--rw period-start              yang:date-and-time
                 |  |  +--rw time-zone-identifier?     sys:timezone-name
                 |  |  +--rw (period-type)?
                 |  |     +--:(explicit)
                 |  |     |  +--rw period-end?         yang:date-and-time
                 |  |     +--:(duration)

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                 |  |        +--rw duration?           duration
                 |  +--:(recurrence)
                 |     +--rw recurrence-first
                 |     |  +--rw utc-start-time?   yang:date-and-time
                 |     |  +--rw duration?         uint32
                 |     +--rw (recurrence-bound)?
                 |     |  +--:(until)
                 |     |  |  +--rw utc-until?          yang:date-and-time
                 |     |  +--:(count)
                 |     |     +--rw count?              uint32
                 |     +--rw recurrence-description?   string
                 |     +--rw frequency                 identityref
                 |     +--rw interval?                 uint32
                 +--rw attr-value
                    +--rw available?   boolean
                    +--rw bandwidth?   yang:gauge64

4.2.  TVR Topology YANG Tree

   The following figure shows the tree diagram of the TVR Topology
   scheduling.

  module: ietf-tvr-topology
    +--rw topology-schedule
       +--rw nodes* [node-id]
       |  +--rw node-id      inet:uri
       |  +--rw available
       |     +--rw default-node-available?   boolean
       |     +--rw schedules* [schedule-id]
       |        +--rw schedule-id                     uint32
       |        +--rw (schedule-type)?
       |        |  +--:(period)
       |        |  |  +--rw period-description?       string
       |        |  |  +--rw period-start              yang:date-and-time
       |        |  |  +--rw time-zone-identifier?     sys:timezone-name
       |        |  |  +--rw (period-type)?
       |        |  |     +--:(explicit)
       |        |  |     |  +--rw period-end?         yang:date-and-time
       |        |  |     +--:(duration)
       |        |  |        +--rw duration?           duration
       |        |  +--:(recurrence)
       |        |     +--rw recurrence-first
       |        |     |  +--rw utc-start-time?   yang:date-and-time
       |        |     |  +--rw duration?         uint32
       |        |     +--rw (recurrence-bound)?
       |        |     |  +--:(until)
       |        |     |  |  +--rw utc-until?          yang:date-and-time
       |        |     |  +--:(count)

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       |        |     |     +--rw count?              uint32
       |        |     +--rw recurrence-description?   string
       |        |     +--rw frequency                 identityref
       |        |     +--rw interval?                 uint32
       |        +--rw attr-value
       |           +--rw node-available?   boolean
       +--rw links* [source-node source-link-id]
          +--rw source-node         inet:uri
          +--rw destination-node?   inet:uri
          +--rw source-link-id      string
          +--rw available
             +--rw schedules* [schedule-id]
             |  +--rw schedule-id                     uint32
             |  +--rw (schedule-type)?
             |  |  +--:(period)
             |  |  |  +--rw period-description?       string
             |  |  |  +--rw period-start              yang:date-and-time
             |  |  |  +--rw time-zone-identifier?     sys:timezone-name
             |  |  |  +--rw (period-type)?
             |  |  |     +--:(explicit)
             |  |  |     |  +--rw period-end?         yang:date-and-time
             |  |  |     +--:(duration)
             |  |  |        +--rw duration?           duration
             |  |  +--:(recurrence)
             |  |     +--rw recurrence-first
             |  |     |  +--rw utc-start-time?   yang:date-and-time
             |  |     |  +--rw duration?         uint32
             |  |     +--rw (recurrence-bound)?
             |  |     |  +--:(until)
             |  |     |  |  +--rw utc-until?          yang:date-and-time
             |  |     |  +--:(count)
             |  |     |     +--rw count?              uint32
             |  |     +--rw recurrence-description?   string
             |  |     +--rw frequency                 identityref
             |  |     +--rw interval?                 uint32
             |  +--rw attr-value
             |     +--rw link-available?   boolean
             |     +--rw bandwidth?        yang:gauge64
             |     +--rw delay?            uint32
             +--rw default-link-available?   boolean
             +--rw default-bandwidth?        yang:gauge64
             +--rw default-delay?            uint32

5.  TVR Schedule YANG Modules

5.1.  TVR Schedule YANG Module

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   <CODE BEGINS> file "ietf-tvr-schedule@2024-07-05.yang"
   module ietf-tvr-schedule {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tvr-schedule";
     prefix tvr-schd;

     import ietf-schedule {
       prefix "schedule";
       reference
         "RFC XXXX: A Common YANG Data Model for Scheduling";
     }

     organization
       "IETF TVR - Time Variant Routing Working Group";
     contact
       "WG Web:   <http://datatracker.ietf.org/wg/tvr>
        WG List:  <mailto:tvr@ietf.org>

        Author:   Yingzhen Qu
                  <mailto:yingzhen.ietf@gmail.com>
        Author:   Acee Lindem
                  <mailto:acee.ietf@gmail.com>
        Author:   Marc Blanchet
                  <mailto:marc.blanchet@viagenie.ca>
        Author:   Eric Kinzie
                  <mailto:ekinzie@labn.net>
        Author:   Don Fedyk
                  <mailto:dfedyk@labn.net>";

     description
       "The YANG module contains common YANG definitions for
        time-variant schedule.

        This YANG model conforms to the Network Management
        Datastore Architecture (NMDA) as described in RFC 8342.

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

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

        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself

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        for full legal notices.";

     reference
       "RFC XXXX: YANG Data Model for Scheduled Attributes";

     revision 2024-07-05 {
       description
         "Initial Version";
       reference
         "RFC XXXX: YANG Data Model for Scheduled Attributes.";
     }

     grouping tvr-schedule {
       list schedules {
         key schedule-id;
         leaf schedule-id {
           type uint32;
           description
             "Identifies the schedule.";
         }
         choice schedule-type {
           description
             "Choice of schedule type.";
           case period {
             description
               "A schedule with a single instance.";
             uses schedule:period-of-time;
           }
           case recurrence {
             description
               "A schedule with recurrence. The time is defined in UTC
                format.";
             uses schedule:recurrence-utc;
           }
         }

         container attr-value {
           description
            "Attribute value(s). This container should be augmented
             with attributes that apply to the current interval.";
         }
         description
           "list of schedules.";
       }
       description
         "A common grouping definition of schedules.";
     }

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   }
   <CODE ENDS>

5.2.  TVR Schedule Node Module

   <CODE BEGINS> file "ietf-tvr-node@2024-07-05.yang"
   module ietf-tvr-node {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tvr-node";
     prefix tvr-node;

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

     import ietf-tvr-schedule {
       prefix "tvr-schd";
     }

     organization
       "IETF TVR - Time Variant Routing Working Group";
     contact
       "WG Web:   <http://datatracker.ietf.org/wg/tvr>
        WG List:  <mailto:tvr@ietf.org>

        Author:   Yingzhen Qu
                  <mailto:yingzhen.ietf@gmail.com>
        Author:   Acee Lindem
                  <mailto:acee.ietf@gmail.com>
        Author:   Marc Blanchet
                  <mailto:marc.blanchet@viagenie.ca>
        Author:   Eric Kinzie
                  <mailto:ekinzie@labn.net>
        Author:   Don Fedyk
                  <mailto:dfedyk@labn.net>";

     description
       "The YANG module is to configure and manage node attributes
        with schedules.

        This YANG model conforms to the Network Management
        Datastore Architecture (NMDA) as described in RFC 8342.

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

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

        This version of this YANG module is part of RFC XXXX
        (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
        for full legal notices.";

     reference
       "RFC XXXX: YANG Data Model for Scheduled Attributes";

     revision 2024-07-05 {
       description
         "Initial Version";
       reference
         "RFC XXXX: YANG Data Model for Scheduled Attributes.";
     }

     container node-schedule {
       description
         "This container defines a node's time variant attributes
          with schedules.";

       leaf node-id {
         type yang:dotted-quad;
         description
           "A 32-bit number used to identify a node.";
       }

       container node-power-schedule {
         description
           "Power schedule for the node. The node's power is
            represented by a boolean value with 'true' indicating
            the node is powered on and 'false' indicating the node
            is powered off.";

         leaf power-default {
           type boolean;
           default false;
           description
             "This indicates the default node power for the time
              periods when no specific power value is specified. If
              unspecified, the node is powered down by default.";
         }

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         uses tvr-schd:tvr-schedule {
           augment "schedules/attr-value" {
             description
               "Augment the power state within each period.";
             leaf power-state {
               type boolean;
               description
                 "Indicates whether the node is powered on.";
             }
           }
         }
       }

       container interface-schedule {
         description
           "Container for TVR node interface attributes.";

         list interfaces {
           key "name";
           description
             "List of interface with schedules.";
           leaf name {
             type union {
               type yang:xpath1.0;
               type string;
             }
             description
               "Name of the interface.
                If used with the ietf-interfaces module, the xpath name
                is to identify the interface.";
           }
           leaf default-available {
             type boolean;
             default false;
             description
               "By default, the link is not available.";
           }
           leaf default-bandwidth {
             type yang:gauge64;
             units "bits/second";
             default "0";
             description
               "The default interface bandwidth in bits
                per second";
           }

           container attribute-schedule {
             description

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               "Interface attributes with schedules.";

             uses tvr-schd:tvr-schedule {
               augment "schedules/attr-value" {
                 description
                   "Augment scheduled interface state.";
                 leaf available {
                   type boolean;
                   description
                     "Scheduled interface power state. This is to
                      work with the leaf 'enabled' for the configured
                      state of the interface.";
                 }
                 leaf bandwidth {
                   type yang:gauge64;
                   units "bits/second";
                   description
                     "The scheduled bandwidth in bits per second";
                 }
               }
             }
           }
         }
       }
     }
   }
   <CODE ENDS>

5.3.  TVR Network Topology Module

<CODE BEGINS> file "ietf-tvr-topology@2024-07-05.yang"
module ietf-tvr-topology {
  yang-version 1.1;
  namespace "urn:ietf:params:xml:ns:yang:ietf-tvr-topology";
  prefix tvr-topo;

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

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

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  import ietf-tvr-schedule {
    prefix "tvr-schd";
  }

  organization
    "IETF Time-Variant Routing Working Group";

  contact
    "WG Web:   <https://datatracker.ietf.org/wg/tvr/>
     WG List:  <mailto:tvr@ietf.org>

     Author:   Eric Kinzie
               <mailto:ekinzie@labn.net>
     Author:   Don Fedyk
               <mailto:dfedyk@labn.net>
     Author:   Yingzhen Qu
               <mailto:yingzhen.ietf@gmail.com>
     Author:   Acee Lindem
               <mailto:acee.ietf@gmail.com>
     Author:   Marc Blanchet
               <mailto:marc.blanchet@viagenie.ca>";

  description
    "This YANG module contains YANG definitions for describing
    network topology with an time-variant availability schedule.

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

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

    This version of this YANG module is part of RFC XXXX
    (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
    for full legal notices.

    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 (RFC 2119) (RFC 8174) when, and only when,
    they appear in all capitals, as shown here.";

  revision 2024-07-05 {
    description
      "Initial revision";

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    reference
      "RFC XXXX: YANG Data Model for Scheduled Attributes";
  }

  container topology-schedule {
    description
      "Network topology schedules.";
    list nodes {
      key "node-id";
      description
        "List of nodes with schedules.";
      leaf node-id {
        type inet:uri;
        description
          "Identifier for a node, uniquely identifies a node. This
           may be the same as the node-id defined in the ietf-network
           module defined in RFC 8345.";
      }
      container available {
        description
          "The time at which this node becomes available.";

        leaf default-node-available {
          type boolean;
          default false;
          description
            "By default, the node is powered off.";
        }

        uses tvr-schd:tvr-schedule {
          augment "schedules/attr-value" {
            description
              "Augment scheduled node availability.";
            leaf node-available {
              type boolean;
              description
                "Node availability.";
            }
          }
        }
      }
    }

    list links {
      key "source-node source-link-id";
      description
        "List of links.";
      leaf source-node {

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        type inet:uri;
        description
          "A name refers to the source node of the link.";
      }
      leaf destination-node {
        type inet:uri;
        description
          "A name refers to the destination node of the link.";
      }
      leaf source-link-id {
        type string;
        description
          "A name refers to the link of the source node.";
      }
      container available {
        description
          "The time at which this link  becomes available.";
        uses tvr-schd:tvr-schedule {
          augment "schedules/attr-value" {
            description
              "Augment scheduled values.";
            leaf link-available {
              type boolean;
              description
                "The predicted link availability.";
            }
            leaf bandwidth {
              type yang:gauge64;
              units "bits/second";
              description
                "The predicted link capacity. If the value measured
                 by the system is less than this value, the system
                 value is used. If the value measured by the system
                 is greater than this value the predicted value
                 SHOULD be used.";
            }
            leaf delay {
              type uint32 {
                range "0..16777215";
              }
              description
                "The predicted one-way delay or latency in
                microseconds. If the value measured by the system is
                less than this value the predicted value SHOULD be used.";
            }
          }
        }
        leaf default-link-available {

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          type boolean;
          default "false";
          description
            "The default link availibility.  During times when the schedule
            does not specifiy an availability, this value is used.";
        }
        leaf default-bandwidth {
          type yang:gauge64;
          units "bits/second";
          default "0";
          description
            "The default link capacity specified in a
             generic format.";
        }
        leaf default-delay {
          type uint32 {
            range "0..16777215";
          }
          description
            "The default link capacity specified in a
             generic format.";
        }
      }
    }
  }
}
<CODE ENDS>

6.  Security Considerations

   The YANG modules specified in this document define a schema for data
   that is designed to be accessed via network management protocols such
   as NETCONF [RFC6241] or RESTCONF [RFC8040].  The lowest NETCONF layer
   is the secure transport layer, and the mandatory-to-implement secure
   transport is Secure Shell (SSH) [RFC6242].  The lowest RESTCONF layer
   is HTTPS, and the mandatory-to-implement secure transport is TLS
   [RFC8446].

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

   There are a number of data nodes defined in ietf-tvr-node.yang module
   and ietf-tvr-topology.yang 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

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   proper protection can have a negative effect on network operations.
   There are the subtrees and data nodes and their sensitivity/
   vulnerability:

      /node-schedule/node-power-schedule
      /node-schedule/interface-schedule
      /topology-schedule/nodes/available
      /topology-schedule/links/available Modifications to these
      scheduled attributes may result in a denial of service.

   Some of the readable data nodes in the ietf-tvr-node.yang module and
   ietf-tvr-topolgy.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.

7.  IANA Considerations

   This document registers a URI in the IETF XML registry [RFC3688].
   Following the format in [RFC3688], the following registration is
   requested to be made:

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

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

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

   This document registers a YANG module in the YANG Module Names
   registry [RFC6020].

      name: ietf-tvr-schedule
      namespace: urn:ietf:params:xml:ns:yang:ietf-tvr-schedule
      prefix: tvr-schd
      reference: RFC XXXX

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

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      name: ietf-tvr-topology
      namespace: urn:ietf:params:xml:ns:yang:ietf-tvr-topology
      prefix: tvr-topo
      reference: RFC XXXX

8.  Acknowledgements

   The YANG model was developed using the suite of YANG tools written
   and maintained by numerous authors.

9.  Normative References

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

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

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

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

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

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

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

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   [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>.

   [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-netmod-schedule-yang]
              Ma, Q., Wu, Q., Boucadair, M., and D. King, "A Common YANG
              Data Model for Scheduling", Work in Progress, Internet-
              Draft, draft-ietf-netmod-schedule-yang-02, 25 June 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-netmod-
              schedule-yang-02>.

10.  Informative References

   [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>.

   [I-D.ietf-tvr-use-cases]
              Birrane, E. J., Kuhn, N., Qu, Y., Taylor, R., and L.
              Zhang, "TVR (Time-Variant Routing) Use Cases", Work in
              Progress, Internet-Draft, draft-ietf-tvr-use-cases-09, 29
              February 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-tvr-use-cases-09>.

Appendix A.  Example: Add a scheduled cost to OSPF interface

   In OSPF (Open Shortest Path First), the interface cost is a metric
   used to determine the preference or desirability of a particular link
   or interface.  By default, the OSPF interface cost is calculated
   based on the bandwidth of the interface, and it is also configurable.

   This example demonstrates how an OSPF interface can be extended with
   a cost that changes with a schedule.

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   module ietf-tvr-ospf-schedule {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-tvr-ospf-schedule";
     prefix ospf-schedule;

     import ietf-routing {
       prefix "rt";
       reference
         "RFC 8349: A YANG Data Model for Routing
          Management (NMDA Version)";
     }
     import ietf-ospf {
       prefix "ospf";
       reference
         "RFC 9129: A YANG Data Model for OSPF Protocol";
     }

     import ietf-tvr-schedule {
       prefix "tvr-schd";
     }

     augment "/rt:routing/rt:control-plane-protocols/"
       + "rt:control-plane-protocol/ospf:ospf/ospf:areas/ospf:area/"
       + "ospf:interfaces/ospf:interface" {
       container scheduled-cost {
         description
           "Augment OSPF interface with a scheduled interface cost.";
         uses tvr-schd:tvr-schedule {
           augment "schedules/attr-value" {
             leaf cost {
               type uint32;
               description
                "interface cost";
             }
           }
         }
       }
     }
   }

Authors' Addresses

   Yingzhen Qu
   Futurewei Technologies
   United States of America
   Email: yingzhen.ietf@gmail.com

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   Acee Lindem
   LabN Consulting, L.L.C.
   301 Midenhall Way
   Cary, NC 27513
   Email: acee.ietf@gmail.com

   Eric Kinzie
   LabN Consulting, L.L.C.
   Email: ekinzie@labn.net

   Don Fedyk
   LabN Consulting, L.L.C.
   Email: dfedyk@labn.net

   Marc Blanchet
   Viagenie
   Email: marc.blanchet@viagenie.ca

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