A YANG Data Model for Scheduled Attributes
draft-ietf-tvr-schedule-yang-09

Internet                                                           Y. Qu
Internet-Draft                                    Futurewei Technologies
Intended status: Standards Track                               A. Lindem
Expires: 10 December 2026                                   Arrcus, Inc.
                                                               E. Kinzie
                                                                D. Fedyk
                                                 LabN Consulting, L.L.C.
                                                             M. Blanchet
                                                                Viagenie
                                                             8 June 2026

               A YANG Data Model for Scheduled Attributes
                    draft-ietf-tvr-schedule-yang-09

Abstract

   The YANG data 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 10 December 2026.

Copyright Notice

   Copyright (c) 2026 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.

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   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  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  . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  TVR Schedule YANG Tree  . . . . . . . . . . . . . . . . .   5
     4.2.  TVR Node YANG Tree  . . . . . . . . . . . . . . . . . . .   5
     4.3.  TVR Topology YANG Tree  . . . . . . . . . . . . . . . . .   7
   5.  TVR Schedule YANG Modules . . . . . . . . . . . . . . . . . .   8
     5.1.  TVR Schedule YANG Module  . . . . . . . . . . . . . . . .   8
     5.2.  TVR Schedule Node Module  . . . . . . . . . . . . . . . .  10
     5.3.  TVR Network Topology Module . . . . . . . . . . . . . . .  14
   6.  Operational Considerations  . . . . . . . . . . . . . . . . .  19
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  19
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  20
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  21
   10. Normative References  . . . . . . . . . . . . . . . . . . . .  21
   11. Informative References  . . . . . . . . . . . . . . . . . . .  22
   Appendix A.  Example: Add a scheduled cost to OSPF interface  . .  23
   Appendix B.  Example: TVR Schedule Node Configuration . . . . . .  24
   Appendix C.  Example: TVR Network Topology Configuration  . . . .  27
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  30

1.  Overview

   There are use cases where changes to the routing topology are
   expected as part of network operations.  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 refer to
   TVR (Time-Variant Routing) Use Cases [RFC9657].

   The YANG [RFC7950] data model in this document can be used to manage
   network resources and topologies with scheduled attributes.  There
   are three YANG modules in this document.

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   Module ietf-tvr-schedule.yang contains the schedule YANG definitions.
   Module ietf-tvr-node.yang is to be used to manage scheduled
   attributes of a single node.  Module ietf-tvr-topology.yang defines a
   network topology with time-variant availability, and it augments the
   ietf-network.yang and ietf-network-topology.yang modules defined in
   [RFC8345].

1.1.  Requirements Language

   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.

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 [RFC9922].

   Users can supply attributes or containers that augment the schedule.
   For example, the "tvr-node" has a container "scheduled-attributes"
   that uses the "tvr-schedule".

   When an attribute's schedule ends, the "value-default" MAY be used,
   when present.  Alternatively, values can remain as set until another
   schedule alters values.

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   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 schedule of A1 may contain a list
   of 3 time periods with different values.  The attribute A2 will take
   on the value vv1 from time t0 until t1, default value va2 from t1
   until t2, and vv2 from t1 until t3.  The schedule of A2 may contain a
   list of two time periods, and the default value is used between
   scheduled values.

   Attributes
             +-------------------+----------+------+
         A1  |       v1          |   v2     |  v3  |
             +-------------------+----------+------+
         A2  |      vv1          |  va2     |  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, scheduled bandwidth,
   and scheduled neighbors.

3.3.  TVR Topology YANG Module

   Defined in [RFC8345], the ietf-network.yang module provides a generic
   model for representing network instances and their nodes, and the
   ietf-network-topology.yang module extends that module with links and
   termination points to describe the connectivity and topology of those
   networks.

   Module ietf-tvr-topology.yang augments the ietf-network.yang and
   ietf-network-topology.yang modules to support the specification of
   time-varying availability schedules for network nodes and links.

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   The "termination-point" is to be mapped to an interface, and is
   augmented with the range of times during which it is available.
   Bandwidth and delay are predicted link attributes.  Delay is the link
   propagation time and does not include any queuing delays.
   "destination-node" of a link may follow a schedule as well.

4.  TVR YANG Trees

4.1.  TVR Schedule YANG Tree

   The following figure shows the tree diagram of the tvr-schedule
   grouping.

   module: ietf-tvr-schedule

     grouping tvr-schedule:
       +-- schedule* [schedule-id]
          +-- schedule-id                     uint32
          +-- (schedule-type)?
             +--:(period)
             |  +-- period-description?       string
             |  +-- period-start?             yang:date-and-time
             |  +-- time-zone-identifier?     sys:timezone-name
             |  +-- (period-type)?
             |     +--:(explicit)
             |     |  +-- period-end?         yang:date-and-time
             |     +--:(duration)
             |        +-- duration?           duration
             +--:(recurrence)
                +-- recurrence-first
                |  +-- start-time-utc?   yang:date-and-time
                |  +-- duration?         uint32
                +-- (recurrence-end)?
                |  +--:(until)
                |  |  +-- utc-until?          yang:date-and-time
                |  +--:(count)
                |     +-- count?              uint32
                +-- recurrence-description?   string
                +-- frequency?                identityref
                +-- interval?                 uint32

4.2.  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?               inet:uri
        +--rw node-power-schedule
        |  +--rw power-default?   boolean
        |  +--rw schedule* [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 start-time-utc?   yang:date-and-time
        |     |     |  +--rw duration?         uint32
        |     |     +--rw (recurrence-end)?
        |     |     |  +--:(until)
        |     |     |  |  +--rw utc-until?          yang:date-and-time
        |     |     |  +--:(count)
        |     |     |     +--rw count?              uint32
        |     |     +--rw recurrence-description?   string
        |     |     +--rw frequency?                identityref
        |     |     +--rw interval?                 uint32
        |     +--rw power-state?                    boolean
        +--rw interface-schedule
           +--rw interface* [name]
              +--rw name                  union
              +--rw default-available?    boolean
              +--rw default-bandwidth?    yang:gauge64
              +--rw attribute-schedule
                 +--rw schedule* [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?

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                    |  |     |          yang:date-and-time
                    |  |     +--:(duration)
                    |  |        +--rw duration?           duration
                    |  +--:(recurrence)
                    |     +--rw recurrence-first
                    |     |  +--rw start-time-utc?   yang:date-and-time
                    |     |  +--rw duration?         uint32
                    |     +--rw (recurrence-end)?
                    |     |  +--:(until)
                    |     |  |  +--rw utc-until?
                    |     |  |          yang:date-and-time
                    |     |  +--:(count)
                    |     |     +--rw count?              uint32
                    |     +--rw recurrence-description?   string
                    |     +--rw frequency?                identityref
                    |     +--rw interval?                 uint32
                    +--rw scheduled-attributes
                       +--rw available?   boolean
                       +--rw bandwidth?   yang:gauge64
                       +--rw neighbor?    inet:uri

4.3.  TVR Topology YANG Tree

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

   module: ietf-tvr-topology
     augment /nw:networks/nw:network/nw:node:
       +--rw available
          +--rw default-node-available?   boolean
          +--rw schedule* [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 start-time-utc?   yang:date-and-time
             |     |  +--rw duration?         uint32
             |     +--rw (recurrence-end)?
             |     |  +--:(until)

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             |     |  |  +--rw utc-until?          yang:date-and-time
             |     |  +--:(count)
             |     |     +--rw count?              uint32
             |     +--rw recurrence-description?   string
             |     +--rw frequency?                identityref
             |     +--rw interval?                 uint32
             +--rw node-available?                 boolean
     augment /nw:networks/nw:network/nw:node/nt:termination-point:
       +--rw available
          +--rw schedule* [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 start-time-utc?   yang:date-and-time
          |  |     |  +--rw duration?         uint32
          |  |     +--rw (recurrence-end)?
          |  |     |  +--:(until)
          |  |     |  |  +--rw utc-until?          yang:date-and-time
          |  |     |  +--:(count)
          |  |     |     +--rw count?              uint32
          |  |     +--rw recurrence-description?   string
          |  |     +--rw frequency?                identityref
          |  |     +--rw interval?                 uint32
          |  +--rw link-attributes
          |     +--rw link-available?     boolean
          |     +--rw bandwidth?          yang:gauge64
          |     +--rw delay?              uint64
          |     +--rw destination-node?   inet:uri
          +--rw default-link-available?   boolean
          +--rw default-bandwidth?        yang:gauge64
          +--rw default-delay?            uint64

5.  TVR Schedule YANG Modules

5.1.  TVR Schedule YANG Module

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   <CODE BEGINS> file "ietf-tvr-schedule@2026-05-19.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 9922: 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.

        Copyright (c) 2026 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).

        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This version of this YANG module is part of RFC XXXX; see

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        the RFC itself for full legal notices.";

     revision 2026-05-19 {
       description
         "Initial Version";
       reference
         "RFC XXXX: A YANG Data Model for Scheduled Attributes.";
     }

     grouping tvr-schedule {
       list schedule {
         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;
           }
         }

         description
           "list of schedules.";
       }
       description
         "A common grouping definition of schedules.";
     }

   }
   <CODE ENDS>

5.2.  TVR Schedule Node Module

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  <CODE BEGINS> file "ietf-tvr-node@2026-05-19.yang"
  module ietf-tvr-node {
    yang-version 1.1;
    namespace "urn:ietf:params:xml:ns:yang:ietf-tvr-node";
    prefix tvr-node;

    import ietf-inet-types {
      prefix inet;
      reference
        "RFC 9911: Common YANG Data Types";
    }

    import ietf-yang-types {
      prefix "yang";
      reference
        "RFC 9911: Common YANG Data Types";
    }

    import ietf-tvr-schedule {
      prefix "tvr-schd";
      reference
        "RFC XXXX: A YANG Data Model for Scheduled Attributes";
    }

    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.

       Copyright (c) 2026 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).

       All revisions of IETF and IANA published modules can be found
       at the YANG Parameters registry group
       (https://www.iana.org/assignments/yang-parameters).

       This version of this YANG module is part of RFC XXXX; see
       the RFC itself for full legal notices.";

    revision 2026-05-19 {
      description
        "Initial Version";
      reference
        "RFC XXXX: A 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 inet:uri;
        description
          "Identifier for a node, uniquely identifies 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 "schedule" {
            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 interface {
          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 {

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            description
              "Interface attributes with schedules.";

            uses tvr-schd:tvr-schedule {
              augment "schedule" {
                description
                  "Augment scheduled interface state.";
                container scheduled-attributes {
                  description
                    "Augmentation container for links.";
                  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";
                  }
                  leaf neighbor {
                    type inet:uri;
                    description
                      "The node expected to be this interface's neighbor
                      during this time.";
                  }
                }
              }
            }
          }
        }
      }
    }
  }
  <CODE ENDS>

5.3.  TVR Network Topology Module

  <CODE BEGINS> file "ietf-tvr-topology@2026-06-05.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 {

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      prefix inet;
      reference
        "RFC 9911: Common YANG Data Types";
    }
    import ietf-yang-types {
      prefix yang;
      reference
        "RFC 9911: Common YANG Data Types";
    }
    import ietf-tvr-schedule {
      prefix tvr-schd;
      reference
        "RFC XXXX: A YANG Data Model for Scheduled Attributes";
    }

    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";
    }

    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 a time-variant availability schedule.

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       Copyright (c) 2026 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).

       All revisions of IETF and IANA published modules can be found
       at the YANG Parameters registry group
       (https://www.iana.org/assignments/yang-parameters).

       This version of this YANG module is part of RFC XXXX; 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 2026-06-05 {
      description
        "Initial revision";
      reference
        "RFC XXXX: A YANG Data Model for Scheduled Attributes";
    }

    grouping node-availability-schedule {
      description
        "Node availability scheduling - reusable grouping specifying
         node availability scheduling.";
      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 "schedule" {
            description
              "Augment scheduled node availability.";
            leaf node-available {
              type boolean;

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              description
                "Node availability.";
            }
          }
        }
      }
    }

    grouping link-availability-schedule {
      description
        "Link availability scheduling - reusable grouping specifying
         link availability scheduling.";
      container available {
        description
          "The time at which this link becomes available.";
        uses tvr-schd:tvr-schedule {
          augment "schedule" {
            description
              "Augment scheduled values.";
            container link-attributes {
              description
                "Augmentation container for links.";
              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 uint64;
                units "microseconds";
                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 destination-node {
                type inet:uri;

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                description
                  "A name refers to the destination node of the link.";
              }
            }
          }
        }
        leaf default-link-available {
          type boolean;
          default "false";
          description
            "The default link availability.  During times when the
             schedule does not specify 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 uint64;
          units "microseconds";
          description
            "The default one-way delay in microseconds.";
        }
      }
    }

    augment "/nw:networks/nw:network/nw:node" {
      description
        "Augment network node with schedules.";
      uses node-availability-schedule;
    }

    augment "/nw:networks/nw:network/nw:node/nt:termination-point" {
      description
        "Augment network link with schedules.";
      uses link-availability-schedule;
    }
  }
  <CODE ENDS>

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6.  Operational Considerations

   The TVR Schedule YANG modules provide a structured mechanism to
   represent time-variant attributes of network elements and topologies.
   The following aspects should be considered by operators deploying the
   modules.

   Operators should be aware that these scheduled attributes represent
   planned state changes, not instantaneous configuration changes or
   unplanned breakages.

   A schedule can be defined using a series of periods or intervals with
   recurrence.  The model defined in this document doesn't prevent a
   configuration to mix both styles.  However, it's NOT RECOMMENDED for
   simplicity and easy readability.

   There should be synchronized clocks between controllers and devices.
   The time sources (e.g., NTP, PTP) should be accurate to avoid
   unintended time/schedule offsets.  Inconsistent time bases can lead
   to network misbehavior, such as routing loops or network instability.

   The modules are to support TVR use cases where topology and
   attributes vary as a function of time.  How control plane and data
   plane are impacted by the schedules should be considered by the
   operators.

   The TVR schedule modules are meant to work together with other models
   that manage node or interface attributes, and the name of these nodes
   and interfaces SHOULD be configured consistently.  Operators should
   consider the conflicting configurations between the scheduled and
   non-scheduled settings and how to handle the conflicts.

7.  Security Considerations

   The YANG modules sepcified in this document define a data model that
   is designed to be accessed via YANG-based management protocols, such
   as the Network Configuration Protocol (NETCONF) [RFC6241] and
   RESTCONF [RFC8040].  These YANG-based management protocols (1) have
   to use a secure transport layer (e.g., Secure Shell (SSH) [RFC4252],
   TLS [RFC8446], and QUIC [RFC9000]) and (2) have to use mutual
   authentication.

   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.

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   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).  All writable data nodes
   are likely to be sensitive or vulnerable in some network
   environments.  Write operations (e.g., edit-config) and delete
   operations to these data nodes without proper protection or
   authentication can have a negative effect on network operations.  The
   following subtrees and data nodes have particular sensitivities/
   vulnerabilities:

      /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.

8.  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

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

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

9.  Acknowledgements

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

10.  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>.

   [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>.

   [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>.

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   [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>.

   [RFC9911]  Schönwälder, J., Ed., "Common YANG Data Types", RFC 9911,
              DOI 10.17487/RFC9911, December 2025,
              <https://www.rfc-editor.org/info/rfc9911>.

   [RFC9922]  Ma, Q., Ed., Wu, Q., Boucadair, M., Ed., and D. King, "A
              Common YANG Data Model for Scheduling", RFC 9922,
              DOI 10.17487/RFC9922, March 2026,
              <https://www.rfc-editor.org/info/rfc9922>.

11.  Informative References

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/info/rfc4252>.

   [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>.

   [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>.

   [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>.

   [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>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

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   [RFC9129]  Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem,
              "YANG Data Model for the OSPF Protocol", RFC 9129,
              DOI 10.17487/RFC9129, October 2022,
              <https://www.rfc-editor.org/info/rfc9129>.

   [RFC9657]  Birrane, III, E., Kuhn, N., Qu, Y., Taylor, R., and L.
              Zhang, "Time-Variant Routing (TVR) Use Cases", RFC 9657,
              DOI 10.17487/RFC9657, October 2024,
              <https://www.rfc-editor.org/info/rfc9657>.

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 example-tvr-ospf-schedule {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:example-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" {
       description
         "Augment OSPF interface configuration.";
       container scheduled-cost {
         description
           "Augment OSPF interface with a scheduled interface cost.";
         uses tvr-schd:tvr-schedule {
           augment "schedule" {
             leaf cost {
               type uint32;
               description
                "interface cost";
             }
             description
               "Augment schedule with an interface cost.";
           }
         }
       }
     }
   }

Appendix B.  Example: TVR Schedule Node Configuration

   The following is an XML example using the ietf-tvr-node YANG module.

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   In this example, the node has a node-id of "node:1", and it's
   scheduled to be powered off starting from 2025-07-26T17:00:00Z to
   2025-07-26T18:00:00Z.  Interface "eth 1" has a recurrent schedule to
   be "not available (off)" which starts from 2025-07-20T23:00:00Z,
   lasts for 7200 seconds (2 hours) each time for 10 times every 2 days.

   Note: '\' line wrapping per [RFC8792].

   <node-schedule xmlns="urn:ietf:params:xml:ns:yang:ietf-tvr-node">
     <node-id>node:1</node-id>
     <node-power-schedule>
       <power-default>true</power-default>
       <schedule>
         <schedule-id>1</schedule-id>
         <period-description>pwr off</period-description>
         <period-start>2025-07-26T17:00:00Z</period-start>
         <time-zone-identifier>UTC</time-zone-identifier>
         <period-end>2025-07-26T18:00:00Z</period-end>
         <power-state>false</power-state>
       </schedule>
     </node-power-schedule>
     <interface-schedule>
       <interface>
         <name>eth 1</name>
         <attribute-schedule>
           <schedule>
             <schedule-id>100</schedule-id>
             <recurrence-first>
               <start-time-utc>2025-07-20T23:00:00Z</start-time-utc>
               <duration>7200</duration>
             </recurrence-first>
             <count>10</count>
             <recurrence-description>daily off</recurrence-description>
             <frequency xmlns:schedule="urn:ietf:params:xml:ns:yang:\
               ietf-schedule">schedule:daily</frequency>
             <interval>2</interval>
             <scheduled-attributes>
               <available>false</available>
             </scheduled-attributes>
           </schedule>
         </attribute-schedule>
       </interface>
     </interface-schedule>
   </node-schedule>

   The following is the same example using JSON format.

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   {
     "ietf-tvr-node:node-schedule": {
       "node-id": "node:1",
       "node-power-schedule": {
         "power-default": true,
         "schedule": [
           {
             "schedule-id": 1,
             "period-description": "pwr off",
             "period-start": "2025-07-26T17:00:00Z",
             "time-zone-identifier": "UTC",
             "period-end": "2025-07-26T18:00:00Z",
             "power-state": false
           }
         ]
       },
       "interface-schedule": {
         "interface": [
           {
             "name": "eth 1",
             "attribute-schedule": {
               "schedule": [
                 {
                   "schedule-id": 100,
                   "recurrence-first": {
                     "start-time-utc": "2025-07-20T23:00:00Z",
                     "duration": 7200
                   },
                   "count": 10,
                   "recurrence-description": "daily off",
                   "frequency": "ietf-schedule:daily",
                   "interval": 2,
                   "scheduled-attributes": {
                     "available": false
                   }
                 }
               ]
             }
           }
         ]
       }
     }
   }

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Appendix C.  Example: TVR Network Topology Configuration

   The following is an XML example using the ietf-tvr-topology YANG
   module.

   In this example, the node with a node-id of "node:1" is scheduled to
   be powered off start from 2025-07-26T17:00:00Z, for 2 days and four
   and half hours.

   Node "node:2" is scheduled to be off starting from
   2025-07-20T23:00:00Z, lasting for 7200 seconds (2 hours) every two
   days until 2025-08-20T23:00:00Z.

   Note: '\' line wrapping per [RFC8792].

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 <networks xmlns="urn:ietf:params:xml:ns:yang:ietf-network">
   <network>
     <network-id>network:1</network-id>
     <node>
       <node-id>node:1</node-id>
       <available xmlns="urn:ietf:params:xml:ns:yang:ietf-tvr-topology">
         <default-node-available>true</default-node-available>
         <schedule>
           <schedule-id>101</schedule-id>
           <period-description>node1 schedule</period-description>
           <period-start>2025-07-26T17:00:00Z</period-start>
           <time-zone-identifier>UTC</time-zone-identifier>
           <duration>P2DT04:30:00</duration>
           <node-available>false</node-available>
         </schedule>
       </available>
     </node>
     <node>
       <node-id>node:2</node-id>
       <available xmlns="urn:ietf:params:xml:ns:yang:ietf-tvr-topology">
         <default-node-available>true</default-node-available>
         <schedule>
           <schedule-id>201</schedule-id>
           <recurrence-first>
             <start-time-utc>2025-07-20T23:00:00Z</start-time-utc>
             <duration>7200</duration>
           </recurrence-first>
           <utc-until>2025-08-20T23:00:00Z</utc-until>
           <recurrence-description>daily off</recurrence-description>
           <frequency xmlns:schedule="urn:ietf:params:xml:ns:yang:\
             ietf-schedule">schedule:daily</frequency>
           <interval>2</interval>
           <node-available>false</node-available>
         </schedule>
       </available>
     </node>
   </network>
 </networks>

   The following is the same example using JSON format.

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   {
     "ietf-network:networks": {
       "network": [
         {
           "network-id": "network:1",
           "node": [
             {
               "node-id": "node:1",
               "ietf-tvr-topology:available": {
                 "default-node-available": true,
                 "schedule": [
                   {
                     "schedule-id": 101,
                     "period-description": "node1 schedule",
                     "period-start": "2025-07-26T17:00:00Z",
                     "time-zone-identifier": "UTC",
                     "duration": "P2DT04:30:00",
                     "node-available": false
                   }
                 ]
               }
             },
             {
               "node-id": "node:2",
               "ietf-tvr-topology:available": {
                 "default-node-available": true,
                 "schedule": [
                   {
                     "schedule-id": 201,
                     "recurrence-first": {
                       "start-time-utc": "2025-07-20T23:00:00Z",
                       "duration": 7200
                     },
                     "utc-until": "2025-08-20T23:00:00Z",
                     "recurrence-description": "daily off",
                     "frequency": "ietf-schedule:daily",
                     "interval": 2,
                     "node-available": false
                   }
                 ]
               }
             }
           ]
         }
       ]
     }
   }

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Authors' Addresses

   Yingzhen Qu
   Futurewei Technologies
   Email: yingzhen.ietf@gmail.com

   Acee Lindem
   Arrcus, Inc.
   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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