]> YANG Data Model for Scheduled Attributes Futurewei Technologies
yingzhen.ietf@gmail.com
Arrcus, Inc.
acee.ietf@gmail.com
LabN Consulting, L.L.C.
ekinzie@labn.net
LabN Consulting, L.L.C.
dfedyk@labn.net
Viagenie
marc.blanchet@viagenie.ca
General Internet 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.
YANG is a data definition language used to define the contents of a conceptual data store that allows networked devices to be managed using NETCONF . 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. 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 reference TVR (Time-Variant Routing) Use Cases . 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) .
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 when, and only when, they appear in all capitals, as shown here.
This document uses the graphical representation of data models defined in .
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 . Users can supply attributes or containers that augment the schedule. 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. 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.
Time Varying Properties Attributes +-------------------+----------+------+ A1 | v1 | v2 | v3 | +-------------------+----------+------+ A2 | vv1 | va2 | vv2 | +-------------------+-----------------+ t0 t1 t2 t3 Time
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.
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. "destination-node" of a link may follow a schedule as well.
The following figure shows the tree diagram of the TVR Node scheduling. 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? | | | 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
The following figure shows the tree diagram of the TVR Topology scheduling. module: ietf-tvr-topology +--rw topology-schedule +--rw node* [node-id] | +--rw node-id inet:uri | +--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) | | | | +--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 +--rw link* [source-node source-link-id] +--rw source-node inet:uri +--rw source-link-id string +--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? uint32 | +--rw destination-node? inet:uri +--rw default-link-available? boolean +--rw default-bandwidth? yang:gauge64 +--rw default-delay? uint32
The following RFC is not referenced in the document text but is referenced in the "ietf-tvr-schedule.yang" module and "ietf-tvr-topology.yang" module: .
file "ietf-tvr-schedule@2025-06-30.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: WG List: Author: Yingzhen Qu Author: Acee Lindem Author: Marc Blanchet Author: Eric Kinzie Author: Don Fedyk "; 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) 2025 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Revised BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info). This version of this YANG module is part of RFC 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 2025-06-30 { description "Initial Version"; reference "RFC XXXX: 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."; } } ]]>
file "ietf-tvr-node@2026-02-09.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"; } organization "IETF TVR - Time Variant Routing Working Group"; contact "WG Web: WG List: Author: Yingzhen Qu Author: Acee Lindem Author: Marc Blanchet Author: Eric Kinzie Author: Don Fedyk "; 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) 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). 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 2022-02-09 { 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 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."; } 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 { 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."; } } } } } } } } } ]]>
file "ietf-tvr-topology@2026-02-09.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 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"; } organization "IETF Time-Variant Routing Working Group"; contact "WG Web: WG List: Author: Eric Kinzie Author: Don Fedyk Author: Yingzhen Qu Author: Acee Lindem Author: Marc Blanchet "; description "This YANG module contains YANG definitions for describing network topology with a time-variant availability 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). 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 2026-02-09 { description "Initial revision"; reference "RFC XXXX: YANG Data Model for Scheduled Attributes"; } container topology-schedule { description "Network topology schedules."; list node { 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 "schedule" { description "Augment scheduled node availability."; leaf node-available { type boolean; description "Node availability."; } } } } } list link { key "source-node source-link-id"; description "List of links."; leaf source-node { type inet:uri; description "A name refers to the source 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 "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 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 destination-node { type inet:uri; 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 uint32 { range "0..16777215"; } description "The default one-way delay in microseconds."; } } } } } ]]>
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. 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. Operators should consider the conflicting configurations between the scheduled and non-scheduled settings and how to handle the conflicts.
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 or RESTCONF . The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) . The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS . The NETCONF access control model 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 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.
This document registers a URI in the IETF XML registry . Following the format in , 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 . 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 name: ietf-tvr-topology namespace: urn:ietf:params:xml:ns:yang:ietf-tvr-topology prefix: tvr-topo reference: RFC XXXX
The YANG model was developed using the suite of YANG tools written and maintained by numerous authors.
&RFC2119; &RFC3688; &RFC6020; &RFC6241; &RFC6242; &RFC7950; &RFC8040; &RFC8174; &RFC8341; &RFC8342; &RFC8446; &RFC9911; &I-D.ietf-netmod-schedule-yang; &RFC8340; &RFC8792; &RFC9657;
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.
Example: TVR Schedule Node Configuration The following is an XML example using the ietf-tvr-node YANG module. 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 . node:1 true 1 pwr off 2025-07-26T17:00:00Z UTC 2025-07-26T18:00:00Z false eth 1 100 2025-07-20T23:00:00Z 7200 10 daily off schedule:daily 2 false ]]> The following is the same example using JSON format.
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 . node:1 true 101 node1 schedule 2025-07-26T17:00:00Z UTC P2DT04:30:00 false node:2 true 201 2025-07-20T23:00:00Z 7200 2025-08-20T23:00:00Z daily off schedule:daily 2 false ]]> The following is the same example using JSON format.