]> Huawei

101 Software Avenue, Yuhua District Jiangsu 210012 China maqiufang1@huawei.com

Huawei

101 Software Avenue, Yuhua District Jiangsu 210012 China bill.wu@huawei.com

Orange

Rennes 35000 France mohamed.boucadair@orange.com

Lancaster University

United Kingdom d.king@lancaster.ac.uk

Operations and Management netmod calendaring scheduling YANG groupings This document defines common types and groupings that are meant to be used for scheduling purposes such as event, policy, services, or resources based on date and time. For the sake of better modularity, the YANG module includes a set of recurrence related groupings with varying levels of representation (i.e., from basic to advanced) to accommodate a variety of requirements. It also defines groupings for validating requested schedules and reporting scheduling status. Discussion Venues This note is to be removed before publishing as an RFC. Discussion of this document takes place on the Network Modeling (NETMOD) Working Group mailing list (netmod@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction This document defines a common schedule YANG module ("ietf-schedule") that can be used in several scheduling contexts, e.g., (but not limited to) , , and . The module includes a set of reusable groupings which are designed to be applicable for scheduling purposes such as event, policy, services or resources based on date and time. It also defines groupings for validating requested schedules and reporting scheduling status. This document does not make any assumption about the nature of actions that are triggered by the schedules. Detection and resolution of any schedule conflicts are beyond the scope of this document. discusses the relationship with the Management Information Base (MIB) managed objects for scheduling management operations defined in . describes a set of examples to illustrate the use of the common schedule groupings (). And provides sample modules to exemplify how future modules can use the extensibility provisions in "ietf-schedule" (). Also, provides an example of using "ietf-schedule" module for scheduled use of resources framework (e.g., ).

Editorial Note (To be removed by RFC Editor) Note to the RFC Editor: This section is to be removed prior to publication. This document contains placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. No other RFC Editor instructions are specified elsewhere in this document. Please apply the following replacements:

• XXXX --> the assigned RFC number for this draft
• 2025-05-30 --> the actual date of the publication of this document

Conventions and Definitions 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. The meanings of the symbols in tree diagrams are defined in . This document uses the YANG terminology defined in . The document makes use of the following terms:

Recurrence Rule:

Refers to a rule or repeating pattern for recurring events. See also for a comprehensive iCalendar recurrence rule specification.

Frequency:

Characterizes the type of a recurrence rule. Values are taken from "FREQ" rule in .

For example, repeating events based on an interval of a second or more are classified as recurrence with a frequency value of "SECONDLY". Frequency values defined as identities in the YANG module are used in lowercase.

iCalendar:

Refers to Internet Calendaring per .

Interval:

Refers to an integer that specifies at which interval a recurrence rule repeats. Values are taken from "INTERVAL" rule in .

For example, "1", means every second for a secondly rule, every minute for a minutely rule, every hour for an hourly rule, etc.

System:

Refers to an entity that hosts a schedule that is managed using the YANG module defined in this document.

Module Overview

Features The "ietf-schedule" data model defines the recurrence related groupings using a modular approach. To that aim, a variety of representations of recurrence groupings ranging from basic to advanced (iCalender like) are defined. To allow for different options, two features are defined in the data model:

• "basic-recurrence"
• "icalendar-recurrence"

Refer to Sections and for the use of these features.

Types and Identities The "ietf-schedule" module () defines the following identities:

• "schedule-type": Indicates the type of a schedule. The following types are defined so far:
  • one-shot: The schedule will trigger an action that has either the duration specified as 0 or the end time specified the same as start time, and then the schedule will disable itself ().
  • period: The schedule is a period-based schedule consisting either (1) a start and end or (2) a start and positive duration of time. If neither an end nor a duration is indicated, the period is considered to last forever.
  • recurrence: This type is used for a recurrence-based schedule. A recurrence may be periodic (i.e., repeat over the same period, e.g., every five minutes) or not (i.e., repeat in a non-regular manner, e.g., every day at 8 and 9 AM).
• "frequency-type": Characterizes the repeating interval rule of a recurrence schedule (secondly, minutely, etc.).
• "schedule-state": Indicates the status of a schedule (enabled, disabled, conflicted, finished, etc.). This identity can also be used to manage the state of individual instances of a recurrence-based schedule.
• "discard-action-type": Specifies the action for the responder to take (e.g., generate a warning or an error message) when a requested schedule cannot be accepted for any reason and is discarded.

Scheduling Groupings The "ietf-schedule" module () defines the following groupings:

• "generic-schedule-params" ()
• "period-of-time" ()
• "recurrence-basic" ()
• "recurrence-utc" ()
• "recurrence-with-time-zone" ()
• "recurrence-utc-with-periods" ()
• "recurrence-time-zone-with-periods" ()
• "icalendar-recurrence" ()
• "schedule-status", "schedule-status-with-time-zone", and "schedule-status-with-name" ()

Examples are provided in .

The "generic-schedule-params" Grouping A system accepts and handles schedule requests, which may help further automate the scheduling process of events, policy, services, or resources based on date and time. The "generic-schedule-params" grouping () specifies a set of configuration parameters that are used by a system for validating requested schedules.

Generic Schedule Configuration Tree Structure

The "description" includes a description of the schedule. No constraint is imposed on the structure nor the use of this parameter. The "time-zone-identifier" parameter, if provided, specifies the time zone reference of the local date and time values. This parameter MUST be specified if any of the date and time values are in the format of local time. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC. The "validity" parameter specifies the date and time after which a schedule will not be considered as valid. It determines the latest time that a schedule can be started to execute independent of when it ends and takes precedence over similar attributes that are provided at the schedule instance itself. A requested schedule may still be accepted but any occurrences that start later than the configured value will not be executed. The "max/min-allowed-start" parameters specify the maximum/minimum scheduled start date and time. A requested schedule will be rejected if the first occurrence of the schedule starts later/earlier than the configured values. The "max-allowed-end" parameter specifies the maximum allowed end time of the last occurrence. A requested schedule will be rejected if the end time of last occurrence is later than the configured "max-allowed-end" value. The "discard-action" parameter specifies the action if a requested schedule cannot be accepted for any reason and is discarded. Possible reasons include, but are not limited to, the requested schedule failing to satisfy the guards in this grouping, conflicting with existing schedules, or being out-of-date. These parameters apply to all schedules on a system and are meant to provide guards against stale configuration, too short schedule requests that would prevent validation by admins of some critical systems, etc.

The "period-of-time" Grouping The "period-of-time" grouping () represents a time period using either a start date and time ("period-start") and end date and time ("period-end"), or a start date and time ("period-start") and a non-negative time duration ("duration"). For the first format, the start of the period MUST be no later the end of the period. If neither an end date and time ("period-end") nor a duration ("duration") is indicated, the period is considered to last forever. If the duration ("duration") value is 0 or the end time ("period-end") is the same as the start time ("period-start"), the period is considered as a one-shot schedule. If no start date and time ("period-start") is specified, the period is considered to start immediately. The "time-zone-identifier" parameter indicates the identifier for the time zone. This parameter MUST be specified if either the "period-start" or "period-end" value is reported in local time format. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC. The "period-description" includes a description of the period. No constraint is imposed on the structure nor the use of this parameter.

Period of Time Grouping Tree Structure

The "recurrence-basic" Grouping The "recurrence-basic" grouping () specifies a simple recurrence rule which starts immediately and repeats forever.

recurrence Grouping Tree Structure

The frequency parameter ("frequency") identifies the type of a recurrence rule. For example, a "daily" frequency value specifies repeating events based on an interval of a day or more. Consistent with , the interval ("interval") represents at which interval the recurrence rule repeats. For example, within a "daily" recurrence rule, an interval value of "8" means every eight days. Note that per , neither a "default" nor a "mandatory" substatement is defined here for both "frequency" and "interval" parameters because there are cases (e.g., profiling) where using these statements is problematic. YANG modules using this grouping SHOULD refine these two nodes with either a "mandatory" or a "default" statement, if they always need to be configured or have default values. This recommendation MAY be ignored in cases such as when this grouping is used by another grouping. The "recurrence-description" includes a description of the period. No constraint is imposed on the structure nor the use of this parameter.

The "recurrence-utc" Grouping The "recurrence-utc" grouping () uses the "recurrence-basic" grouping and specifies a simple recurrence rule in UTC format.

recurrence-utc Grouping Tree Structure

The "start-time-utc" indicates the start time in UTC format. The "duration" parameter specifies, in units of seconds, the time period of the first occurrence. Unless specified otherwise (e.g., through additional augmented parameters), the "duration" also applies to subsequent recurrence instances. When unspecified, each occurrence is considered as immediate completion (e.g., execute an immediate command that is considered to complete quickly) or hard to compute an exact duration (e.g., run a data analysis script whose execution time may depend on the data volume and computation resource availability). The behavior to follow when a task takes more time than specified by the "duration" is out of scope. Such considerations belong to task management, not schedule management. Note that the "interval" and "duration" cover two distinct properties of a schedule event. The interval specifies when a schedule will occur, combined with the frequency parameter; while the duration indicates how long an occurrence will last. This document allows the interval between occurrences to be shorter than the duration of each occurrence (e.g., a recurring event is scheduled to start every day for a duration of 2 days). The repetition can be scoped by a specified end time or by a count of occurrences, indicated by the "recurrence-end" choice. The value of the "count" node MUST be greater than 1, the "start-time-utc" value always counts as the first occurrence. The "recurrence-utc" grouping is designed to be reused in scheduling contexts where machine readability is more desirable.

The "recurrence-with-time-zone" Grouping The "recurrence-with-time-zone" grouping () uses the "recurrence-basic" grouping and specifies a simple recurrence rule with a time zone.

recurrence-with-time-zone Grouping Tree Structure

The "recurrence-first" container includes "start-time" and "duration" parameters to specify the start time and period of the first occurrence. Unless specified otherwise (e.g., through additional augmented parameters), the "duration" also applies to subsequent recurrence instances. When unspecified, each occurrence is considered as immediate completion (e.g., execute an immediate command that is considered to complete quickly) or hard to compute an exact duration (e.g., run a data analysis script whose execution time may depend on the data volume and computation resource availability). The grouping also includes a "time-zone-identifier" parameter which MUST be specified if either the "start-time" or "until" value is reported in local time format. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC. The repetition can be scoped by a specified end time or by a count of occurrences, indicated by the "recurrence-end" choice. The value of the "count" node MUST be greater than 1, the "start-time" value always counts as the first occurrence. Unlike the definition of "recurrence-utc" grouping (), "recurrence-with-time-zone" is intended to promote human readability over machine readability.

The "recurrence-utc-with-periods" Grouping The "recurrence-utc-with-periods" grouping () uses the "recurrence-utc" grouping () and adds a "period-timeticks" list to define an aggregate set of repeating occurrences.

recurrence-utc-with-periods Grouping Tree Structure

The recurrence instances are specified by the union of occurrences defined by both the recurrence rule and "period-timeticks" list. This list uses "yang:timeticks" type defined in . Duplicate instances are ignored. The value of the "period-start" instance MUST NOT exceed the value indicated by the value of "frequency" instance, i.e., the timeticks value must not exceed 100 in a secondly recurrence rule, and it must not exceed 6000 in a minutely recurrence rule, and so on.

The "recurrence-time-zone-with-periods" Grouping The "recurrence-time-zone-with-periods" grouping () uses the "recurrence-with-time-zone" grouping () and adds a "period" list to define an aggregate set of repeating occurrences.

recurrence-time-zone-with-periods Grouping Tree Structure

The recurrence instances are specified by the union of occurrences defined by both the recurrence rule and "period" list. Duplicate instances are ignored.

The "icalendar-recurrence" Grouping The "icalendar-recurrence" grouping () uses the "recurrence-time-zone-with-periods" grouping () and define more data nodes to enrich the definition of recurrence. The structure of the "icalendar-recurrence" grouping refers to the definition of recurrence component defined in Sections and of .

icalendar-recurrence Grouping Tree Structure

An array of the "bysecond" (or "byminute", "byhour") specifies a list of seconds within a minute (or minutes within an hour, hours of the day). For example, within a "minutely" recurrence rule, the values of "byminute" node "10" and "20" means the occurrences generates at the 10th and 20th minute within an hour, reducing the number of recurrence instances from all minutes. The parameter "byday" specifies a list of days of the week, with an optional direction which indicates the nth occurrence of a specific day within the "monthly" or "yearly" frequency instance. Valid values of "direction" are 1 to 5 or -5 to -1 within a "monthly" recurrence rule; and 1 to 53 or -53 to -1 within a "yearly" recurrence rule. For example, within a "monthly" rule, the "weekday" with a value of "monday" and the "direction" with a value of "-1" represents the last Monday of the month. An array of the "bymonthday" (or byyearday", "byyearweek", or "byyearmonth") specifies a list of days of the month (or days of the year, weeks of the year, or months of the year). For example, within a "yearly" recurrence rule, the values of "byyearmonth" instance "1" and "2" means the occurrences generates in January and February, increasing the "yearly" recurrence from every year to every January and February of the year. The "bysetpos" conveys a list of values that corresponds to the nth occurrence within the set of recurrence instances to be specified. For example, in a "monthly" recurrence rule, the "byday" data node specifies every Monday of the week, the "bysetpos" with value of "-1" represents the last Monday of the month. Not setting the "bysetpos" data node represents every Monday of the month. The "workweek-start" data node specifies the day on which the week starts. This is significant when a "weekly" recurrence rule has an interval greater than 1, and a "byday" data node is specified. This is also significant when in a "yearly" rule and a "byyearweek" is specified. Note that per , neither a "default" nor a "mandatory" substatement is defined here because there are cases (e.g., profiling) where using these statements is problematic. YANG modules using this grouping SHOULD refine the "workweek-start" node with either a "mandatory" or a "default" statement, if it always needs to be configured or has a default value. This MAY be ignored in cases such as when this grouping is used by another grouping. The "exception-dates" data node specifies a list of exceptions for recurrence. The final recurrence set is generated by gathering all of the date and time values generated by any of the specified recurrence rule and date-times, and then excluding any start date and time values specified by "exception-dates" parameter.

The "schedule-status", "schedule-status-with-time-zone", and "schedule-status-with-name" Groupings The "schedule-status", "schedule-status-with-time-zone", and "schedule-status-with-name" groupings () define common parameters for scheduling management/status exposure. The "schedule-status-with-time-zone" grouping has the same structure as "schedule-status" but with an additional parameter to identify a time zone. Similarly, the "schedule-status-with-name" grouping has the same structure as "schedule-status" but with an additional parameter to identify a schedule "schedule-name". These structures are defined in the module to allow for better modularity and flexibility.

Schedule Status with and without Name Groupings Tree Structure

The "schedule-name" parameter is useful to uniquely identify a schedule in a network device or controller if multiple scheduling contexts exists. The "state" parameter is defined to configure/expose the scheduling state, depending on the use of the grouping. For a recurrence-based schedule, it represents the state of the overall recurrence. The "identityref" type is used for this parameter to allow extensibility in future modules. The "version" parameter is used to track the current schedule version information. The version can be bumped by the entity who create the schedule. The "last-update" parameter identifies when the schedule was last modified. In some contexts, this parameter can be used to track the configuration of a given schedule. In such cases, the "version" may not be used. The "schedule-type" parameter identifies the type of the current schedule. The "counter", "last-occurrence", and "upcoming-occurrence" data nodes are only available when the "schedule-type" is "recurrence". When no time zone is included, "local-time" reports the actual local time as seen by the entity that host a schedule. This parameter can be used by a controller to infer the offset to UTC. This use is similar to the use of "schedLocalTime" in . "last-failed-occurrence" and "failure-counter" report the last failure that occurred and the count of failures for this schedule. Unless new parameters/operations are defined to allow the count of failures to be reset, "failure-counter" is reset by default only when the schedule starts. The current groupings capture common parameters that are applicable to typical scheduling contexts known so far. Future modules can define other useful parameters as needed. For example, in a scheduling context with multiple system sources to feed the schedules, the "source" and "precedence" parameters may be needed to reflect how schedules from different sources should be prioritized.

Features Use and Augmentations provides an example about how the features defined in can be used. Implementations may support a basic recurrence rule or an advanced one as needed, by declaring different features. Whether only one or both features are supported is implementation specific and depend on specific scheduling context. The common schedule groupings () can also be augmented to support specific needs. As an example, demonstrates how additional parameters can be added to comply with specific schedule needs.

Some Usage Restrictions There are some restrictions that need to be followed when using groupings defined in the "ietf-schedule" YANG module ():

• The instant in time represented by "period-start" MUST be before the "period-end" for "period-of-time" grouping ().
• The combination of the day, month, and year represented for date and time values MUST be valid. See for the maximum day number based on the month and year.
• The second for date and time values MUST have the value "60" at the end of months in which a leap second occurs.
• Schedules received with a starting time in the past with respect to current time SHOULD be ignored. When a local policy is provided, an implementation MAY omit the past occurrences and start immediately (e.g., for a period-based schedule) or starts from the date and time when the recurrence pattern is first satisfied from the current time (e.g., for a recurrence-based schedule).

Relationship to the DISMAN-SCHEDULE-MIB specifies a Management Information Base (MIB) used to schedule management operations periodically or at specified dates and times. Although no data nodes are defined in this document, lists how the main objects in the DISMAN-SCHEDULE-MIB can be mapped to YANG parameters. YANG/MIB Mapping

MIB Object	YANG
schedLocalTime	local-time
schedType	schedule-type
schedName	schedule-name
schedOwner	Not Supported
schedDescr	description
schedInterval	interval
schedWeekDay	weekday
schedMonth	byyearmonth
schedDay	bymonthday
schedHour	byhour
schedMinute	byminute
schedContextName	Not Supported
schedAdminStatus	state
schedOperStatus	state
schedFailures	failure-counter
schedLastFailure	Not Supported
schedLastFailed	last-failed-occurrence
schedStorageType	Not Supported
schedVariable	Not applicable
schedValue	Not applicable
schedTriggers	counter/failure-counter

The "ietf-schedule" YANG Module This module imports types defined in and . WG List: Editor: Qiufang Ma Editor: Mohamed Boucadair Author: Daniel King "; description "This YANG module defines a set of common types and groupings which are applicable for scheduling purposes such as events, policy, services, or resources based on date and time. 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). 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 2025-05-30 { description "Initial revision."; reference "RFC XXXX: A Common YANG Data Model for Scheduling"; } feature basic-recurrence { description "Indicates that the server supports configuring a basic scheduled recurrence."; } feature icalendar-recurrence { description "Indicates that the server supports configuring a comprehensive scheduled icalendar recurrence"; reference "RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar), Sections 3.3.10 and 3.8.5"; } typedef weekday { type enumeration { enum sunday { value 0; description "Sunday of the week."; } enum monday { value 1; description "Monday of the week."; } enum tuesday { value 2; description "Tuesday of the week."; } enum wednesday { value 3; description "Wednesday of the week."; } enum thursday { value 4; description "Thursday of the week."; } enum friday { value 5; description "Friday of the week."; } enum saturday { value 6; description "Saturday of the week."; } } description "Seven days of the week."; } typedef duration { type string { pattern '((\+)?|\-)P((([0-9]+)D)?(T(0[0-9]|1[0-9]|2[0-3])' + ':[0-5][0-9]:[0-5][0-9]))|P([0-9]+)W'; } description "Duration of the time. The format can represent nominal durations (weeks designated by 'W' and days designated by 'D') and accurate durations (hours:minutes:seconds follows the designator 'T'). Note that this value type doesn't support the 'Y' and 'M' designators to specify durations in terms of years and months. Negative durations are typically used to schedule an alarm to trigger before an associated time."; reference "RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar), Sections 3.3.6 and 3.8.6.3"; } identity schedule-type { description "Base identity for schedule type."; } identity one-shot { base schedule-type; description "Indicates a one-shot schedule. That is a schedule that will trigger an action with the duration being specified as 0/end time being specified the same as start time, and then the schedule will disable itself."; } identity period { base schedule-type; description "Indicates a period-based schedule consisting either a start and end or a start and positive duration of time. If neither an end nor a duration is indicated, the period is considered to last forever."; } identity recurrence { base schedule-type; description "Indicates a recurrence-based schedule."; } identity frequency-type { description "Base identity for frequency type."; } identity secondly { base frequency-type; description "Indicates a repeating rule based on an interval of a second or more."; } identity minutely { base frequency-type; description "Indicates a repeating rule based on an interval of a minute or more."; } identity hourly { base frequency-type; description "Indicates a repeating rule based on an interval of an hour or more."; } identity daily { base frequency-type; description "Indicates a repeating rule based on an interval of a day or more."; } identity weekly { base frequency-type; description "Indicates a repeating rule based on an interval of a week or more."; } identity monthly { base frequency-type; description "Indicates a repeating rule based on an interval of a month or more."; } identity yearly { base frequency-type; description "Indicates a repeating rule based on an interval of a year or more."; } identity schedule-state { description "Base identity for schedule state."; } identity enabled { base schedule-state; description "Indicates a schedule with an enabled state."; } identity finished { base schedule-state; description "Indicates a schedule with a finished state. The finished state indicates that the schedule has ended."; } identity disabled { base schedule-state; description "Indicates a schedule with a disabled state."; } identity out-of-date { base schedule-state; description "Indicates a schedule with an out-of-date state."; } identity conflicted { base schedule-state; description "Indicates a schedule with a conflicted state with other schedules."; } identity discard-action-type { description "Indicates the action for the responder to take when a requested schedule cannot be accepted for any reason and is discarded."; } identity warning { base discard-action-type; description "Indicates that a warning message is generated when a schedule is discarded."; } identity error { base discard-action-type; description "Indicates that an error message is generated when a schedule is discarded."; } identity silently-discard { base discard-action-type; description "Indicates that a schedule that is not valid is silently discarded."; } grouping generic-schedule-params { description "Includes a set of generic parameters that are followed by the entity that supports schedules. Such parameters are used as guards to prevent, e.g., stale configuration."; leaf description { type string; description "Provides a description of the schedule."; } leaf time-zone-identifier { type sys:timezone-name; description "Indicates the identifier for the time zone. This parameter MUST be specified if any of the date and time values are in the format of local time. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC."; } leaf validity { type yang:date-and-time; description "Specifies the date and time after which a schedule will not be considered as valid. This parameter takes precedence over similar attributes that are provided at the schedule instance itself."; } leaf max-allowed-start { type yang:date-and-time; description "Specifies the maximum scheduled start date and time. A requested schedule whose first instance occurs after this value cannot be accepted by the entity. Specifically, a requested schedule will be rejected if the first occurrence of that schedule exceeds 'max-allowed-start'."; } leaf min-allowed-start { type yang:date-and-time; description "Specifies the minimum scheduled start date and time. A requested schedule whose first instance occurs before this value cannot be accepted by the entity. Specifically, a requested schedule will be rejected if the first occurrence of that schedule is scheduled before 'min-allowed-start'."; } leaf max-allowed-end { type yang:date-and-time; description "A requested schedule will be rejected if the end time of the last occurrence exceeds 'max-allowed-end'."; } leaf discard-action { type identityref { base discard-action-type; } description "Specifies the behavior when a schedule is discarded for any reason, e.g., failing to satisfy the guards in this grouping or it is received out-of-date."; } } grouping period-of-time { description "This grouping is defined for period of time property."; reference "RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar), Section 3.3.9"; leaf period-description { type string; description "Provides a description of the period."; } leaf period-start { type yang:date-and-time; description "Period start time."; } leaf time-zone-identifier { type sys:timezone-name; description "Indicates the identifier for the time zone in a time zone database. This parameter MUST be specified if either the 'period-start' or 'period-end' value is reported in local time format. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC."; } choice period-type { description "Indicates the type of the time period. Two types are supported. If no choice is indicated, the period is considered to last forever."; case explicit { description "A period of time is identified by its start and its end. 'period-start' indicates the period start."; leaf period-end { type yang:date-and-time; description "A period of time is defined by a start and end time. The start MUST be no later than the end. The period is considered as a one-shot schedule if the end time is the same as the start time."; } } case duration { description "A period of time is defined by a start and a non-negative duration of time."; leaf duration { type duration { pattern 'P((([0-9]+)D)?(T(0[0-9]|1[0-9]|2[0-3])' + ':[0-5][0-9]:[0-5][0-9]))|P([0-9]+)W'; } description "A non-negative duration of the time. This value is equivalent to the format of duration type except that the value cannot be negative. The period is considered as a one-shot schedule if the value is 0"; } } } } grouping recurrence-basic { description "A simple definition of recurrence."; leaf recurrence-description { type string; description "Provides a description of the recurrence."; } leaf frequency { type identityref { base frequency-type; } description "Specifies the frequency type of the recurrence rule."; } leaf interval { type uint32 { range "1..max"; } must '../frequency' { error-message "Frequency must be provided."; } description "A positive integer representing at which interval the recurrence rule repeats. For example, within a 'daily' recurrence rule, a value of '8' means every eight days."; } } grouping recurrence-utc { description "A simple definition of recurrence with time specified in UTC format."; container recurrence-first { description "Specifies the first instance of the recurrence. If unspecified, the recurrence is considered to start from the date and time when the recurrence pattern is first satisfied."; leaf start-time-utc { type yang:date-and-time; description "Defines the instant date and time of the first instance in the recurrence set. A UTC format MUST be used."; } leaf duration { type uint32; units "seconds"; description "When specified, it indicates how long the first occurrence last. Unless specified otherwise, it also applies to all the other instances in the recurrence set."; } } choice recurrence-end { description "Modes to control the end of a recurrence rule. If no choice is indicated, the recurrence rule is considered to repeat forever."; case until { description "This case defines a way that limits the end of a recurrence rule in an inclusive manner."; leaf utc-until { type yang:date-and-time; description "This parameter specifies a date and time value to inclusively terminate the recurrence in UTC format. If the value specified by this parameter is synchronized with the specified recurrence, it becomes the last instance of the recurrence."; } } case count { description "This case defines the number of occurrences at which to terminate the recurrence."; leaf count { type uint32 { range "1..max"; } description "The positive number of occurrences at which to terminate the recurrence."; } } } uses recurrence-basic; } grouping recurrence-with-time-zone { description "A simple definition of recurrence to specify a recurrence rule with a time zone."; container recurrence-first { description "Specifies the first instance of the recurrence. If unspecified, the recurrence is considered to start from the date and time when the recurrence pattern is first satisfied."; leaf start-time { type yang:date-and-time; description "Defines the instant date and time of the first instance in the recurrence set."; } leaf duration { type duration; description "When specified, it indicates how long the first occurrence last. Unless specified otherwise, it also applies to all the other instances in the recurrence set."; } } leaf time-zone-identifier { type sys:timezone-name; description "Indicates the identifier for the time zone in a time zone database. This parameter MUST be specified if either the 'start-time' or 'until' value is reported in local time format. It MUST NOT be applied to date and time values which are specified in the format of UTC or time zone offset to UTC."; } choice recurrence-end { description "Modes to terminate the recurrence rule. If no choice is indicated, the recurrence rule is considered to repeat forever."; case until { description "The end of the recurrence is indicated by a specific date-and-time value."; leaf until { type yang:date-and-time; description "Specifies a date and time value to terminate the recurrence. If the value specified by this parameter is synchronized with the specified recurrence, it becomes the last instance of the recurrence."; } } case count { description "The end of the recurrence is indicated by the number of occurrences."; leaf count { type uint32 { range "1..max"; } description "The positive number of occurrences at which to terminate the recurrence."; } } } uses recurrence-basic; } grouping recurrence-utc-with-periods { description "This grouping defines an aggregate set of repeating occurrences with UTC time format. The recurrence instances are specified by the occurrences defined by both the recurrence rule and 'period-timeticks' list. Duplicate instances are ignored."; uses recurrence-utc; list period-timeticks { key "period-start"; description "A list of periods with timeticks formats."; leaf period-start { type yang:timeticks; must "(not(derived-from(../../frequency," + "'schedule:secondly')) or (current() < 100)) and " + "(not(derived-from(../../frequency," + "'schedule:minutely')) or (current() < 6000)) and " + "(not(derived-from(../../frequency,'schedule:hourly'))" + " or (current() < 360000)) and " + "(not(derived-from(../../frequency,'schedule:daily'))" + " or (current() < 8640000)) and " + "(not(derived-from(../../frequency,'schedule:weekly'))" + " or (current() < 60480000)) and " + "(not(derived-from(../../frequency," + "'schedule:monthly')) or (current() < 267840000)) and " + "(not(derived-from(../../frequency,'schedule:yearly'))" + " or (current() < 3162240000))" { error-message "The period-start must not exceed the frequency interval."; } description "Start time of the schedule within one recurrence. Given that the value is in timeticks format (i.e., 1/100 of a second), the values in the must statement translate to: 100 = 1s (secondly), 6000 = 60 s = 1 min (minutely), and so on for all instances in the must statement invariant."; } leaf period-end { type yang:timeticks; description "End time of the schedule within one recurrence."; } } } grouping recurrence-time-zone-with-periods { description "This grouping defines an aggregate set of repeating occurrences with local time format and time zone specified. The recurrence instances are specified by the occurrences defined by both the recurrence rule and 'period' list. Duplicate instances are ignored."; uses recurrence-with-time-zone; list period { key "period-start"; description "A list of periods with date-and-time formats."; uses period-of-time; } } grouping icalendar-recurrence { description "This grouping specifies properties of a recurrence rule."; reference "RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar), Section 3.8.5"; uses recurrence-time-zone-with-periods; leaf-list bysecond { type uint32 { range "0..60"; } description "Specifies a list of seconds within a minute."; } leaf-list byminute { type uint32 { range "0..59"; } description "Specifies a list of minutes within an hour."; } leaf-list byhour { type uint32 { range "0..23"; } description "Specifies a list of hours of the day."; } list byday { key "weekday"; description "Specifies a list of days of the week."; leaf-list direction { when "derived-from(../../frequency, 'schedule:monthly') or " + "(derived-from(../../frequency, 'schedule:yearly') " + " and not(../../byyearweek))"; type int32 { range "-53..-1|1..53"; } description "When specified, it indicates the nth occurrence of a specific day within the monthly or yearly recurrence rule. For example, within a monthly rule, +1 monday represents the first monday within the month, whereas -1 monday represents the last monday of the month."; } leaf weekday { type schedule:weekday; description "Corresponds to seven days of the week."; } } leaf-list bymonthday { type int32 { range "-31..-1|1..31"; } description "Specifies a list of days of the month."; } leaf-list byyearday { type int32 { range "-366..-1|1..366"; } description "Specifies a list of days of the year."; } leaf-list byyearweek { when "derived-from(../frequency, 'schedule:yearly')"; type int32 { range "-53..-1|1..53"; } description "Specifies a list of weeks of the year."; } leaf-list byyearmonth { type uint32 { range "1..12"; } description "Specifies a list of months of the year."; } leaf-list bysetpos { type int32 { range "-366..-1|1..366"; } description "Specifies a list of values that corresponds to the nth occurrence within the set of recurrence instances specified by the rule. It must only be used in conjunction with another by the rule part."; } leaf workweek-start { type schedule:weekday; description "Specifies the day on which the workweek starts."; } leaf-list exception-dates { type yang:date-and-time; description "Defines a list of exceptions for recurrence."; } } grouping schedule-status { description "This grouping defines common properties of scheduling status."; leaf state { type identityref { base schedule-state; } description "Indicates the current state of the schedule."; } leaf version { type uint16; description "Indicates the version number of the schedule."; } leaf schedule-type { type identityref { base schedule-type; } description "Indicates the schedule type."; } leaf local-time { type yang:date-and-time; config false; description "Reports the local time as used by the entity that hosts the schedule."; } leaf last-update { type yang:date-and-time; config false; description "Reports the timestamp that the schedule is last updated."; } leaf counter { when "derived-from-or-self(../schedule-type, " + "'schedule:recurrence')"; type yang:counter32; config false; description "The number of occurrences while invoking the scheduled action successfully. The count wraps around when it reaches the maximum value."; } leaf last-occurrence { when "derived-from-or-self(../schedule-type, " + "'schedule:recurrence')"; type yang:date-and-time; config false; description "Indicates the timestamp of last occurrence."; } leaf upcoming-occurrence { when "derived-from-or-self(../schedule-type, " + "'schedule:recurrence')" + "and derived-from-or-self(../state, 'schedule:enabled')"; type yang:date-and-time; config false; description "Indicates the timestamp of next occurrence."; } leaf last-failed-occurrence { when "derived-from-or-self(../schedule-type, " + "'schedule:recurrence')"; type yang:date-and-time; config false; description "Indicates the timestamp of last failed action triggered by the schedule."; } leaf failure-counter { when "derived-from-or-self(../schedule-type, " + "'schedule:recurrence')"; type yang:counter32; config false; description "Counts the number of failures while invoking the scheduled action."; } } grouping schedule-status-with-time-zone { description "This grouping defines common properties of scheduling status, including timezone"; leaf time-zone-identifier { type sys:timezone-name; config false; description "Indicates the identifier for the time zone in a time zone database."; } uses schedule-status; } grouping schedule-status-with-name { description "This grouping defines common properties of scheduling status, including a schedule name."; leaf schedule-name { type string; description "The schedule identifier that uniquely identifies a schedule within a device, controller, network, etc. The unicity scope depends on the implementation."; } uses schedule-status; } } ]]>

Security Considerations This section uses the template described in . The "ietf-schedule" YANG module specified in this document defines schema for data that is designed to be accessed via YANG-based management protocols, such as NETCONF or RESTCONF . These YANG-based management protocols (1) have to use a secure transport layer (e.g., SSH , TLS , and QUIC ) and (2) have to use mutual authentication. The Network Configuration Access Control Model (NACM) provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. The "ietf-schedule" module defines a set of types and groupings. These nodes are intended to be reused by other YANG modules. The module by itself does not expose any data nodes that are writable, data nodes that contain read-only state, or RPCs. As such, there are no additional security issues related to the "ietf-schedule" module that need to be considered. Modules that use the groupings that are defined in this document should identify the corresponding security considerations, e.g.,:

• Scheduling depends on reliable and accurate time synchronization. Inaccurate date and time setting can lead to scheduling events being triggered at incorrect intervals, potentially causing system failures or security vulnerabilities.
• Recurring events may conceal abnormal behavior or security threats, which may be drowned out by normal events, especially when they are triggered frequently.
• The absence of detailed logs and audit records of each occurrence trigger time and action results, and so on, may make security incidents difficult to trace.
• Care must be taken when defining recurrences occurring very often and frequent that can be an additional source of attacks by keeping the system permanently busy with the management of scheduling.

IANA Considerations

The "IETF XML" Registry This document registers the following URI in the "IETF XML Registry" .

The "YANG Module Names" Registry This document registers the following YANG module in the "YANG Module Names" registry .

References Normative References This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes a set of managed objects that are used to schedule management operations periodically or at specified dates and times. [STANDARDS-TRACK] In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. YANG is a data modeling language used to model configuration data, state data, Remote Procedure Calls, and notifications for network management protocols. This document describes the syntax and semantics of version 1.1 of the YANG language. YANG version 1.1 is a maintenance release of the YANG language, addressing ambiguities and defects in the original specification. There are a small number of backward incompatibilities from YANG version 1. This document also specifies the YANG mappings to the Network Configuration Protocol (NETCONF). This document defines the iCalendar data format for representing and exchanging calendaring and scheduling information such as events, to-dos, journal entries, and free/busy information, independent of any particular calendar service or protocol. [STANDARDS-TRACK] This document defines a YANG data model for the configuration and identification of some common system properties within a device containing a Network Configuration Protocol (NETCONF) server. This document also includes data node definitions for system identification, time-of-day management, user management, DNS resolver configuration, and some protocol operations for system management. This document introduces a collection of common data types to be used with the YANG data modeling language. This document obsoletes RFC 6021. The standardization of network configuration interfaces for use with the Network Configuration Protocol (NETCONF) or the RESTCONF protocol requires a structured and secure operating environment that promotes human usability and multi-vendor interoperability. There is a need for standard mechanisms to restrict NETCONF or RESTCONF protocol access for particular users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. This document defines such an access control model. This document obsoletes RFC 6536. This document describes an IANA maintained registry for IETF standards which use Extensible Markup Language (XML) related items such as Namespaces, Document Type Declarations (DTDs), Schemas, and Resource Description Framework (RDF) Schemas. YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications. [STANDARDS-TRACK] Informative References Huawei Huawei Orange Lancaster University This document defines a YANG data model for policy-based network access control, which provides consistent and efficient enforcement of network access control policies based on group identity. Moreover, this document defines a mechanism to ease the maintenance of the mapping between a user group identifier and a set of IP/MAC addresses to enforce policy-based network access control. In addition, the document defines a Remote Authentication Dial-in User Service (RADIUS) attribute that is used to communicate the user group identifier as part of identification and authorization information. Telefonica Nokia This document defines a YANG data model for network diagnosis on- demand relying upon Operations, Administration, and Maintenance (OAM) tests. This document defines both 'oam-unitary-test' and 'oam-test- sequence' YANG modules to manage the lifecycle of network diagnosis procedures. Futurewei Technologies LabN Consulting, L.L.C. LabN Consulting, L.L.C. LabN Consulting, L.L.C. Viagenie 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. Time-Scheduled (TS) reservation of Traffic Engineering (TE) resources can be used to provide resource booking for TE Label Switched Paths so as to better guarantee services for customers and to improve the efficiency of network resource usage at any moment in time, including network usage that is planned for the future. This document provides a framework that describes and discusses the architecture for supporting scheduled reservation of TE resources. This document does not describe specific protocols or protocol extensions needed to realize this service. This document captures the current syntax used in YANG module tree diagrams. The purpose of this document is to provide a single location for this definition. This syntax may be updated from time to time based on the evolution of the YANG language. YumaWorks Orange Huawei This document provides guidelines for authors and reviewers of specifications containing YANG data models, including IANA-maintained modules. Recommendations and procedures are defined, which are intended to increase interoperability and usability of Network Configuration Protocol (NETCONF) and RESTCONF Protocol implementations that utilize YANG modules. This document obsoletes RFC 8407. Also, this document updates RFC 8126 by providing additional guidelines for writing the IANA considerations for RFCs that specify IANA-maintained modules. This document defines a date and time format for use in Internet protocols that is a profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar. The Network Configuration Protocol (NETCONF) defined in this document provides mechanisms to install, manipulate, and delete the configuration of network devices. It uses an Extensible Markup Language (XML)-based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs). This document obsoletes RFC 4741. [STANDARDS-TRACK] This document describes an HTTP-based protocol that provides a programmatic interface for accessing data defined in YANG, using the datastore concepts defined in the Network Configuration Protocol (NETCONF). The Secure Shell Protocol (SSH) is a protocol for secure remote login and other secure network services over an insecure network. This document describes the SSH authentication protocol framework and public key, password, and host-based client authentication methods. Additional authentication methods are described in separate documents. The SSH authentication protocol runs on top of the SSH transport layer protocol and provides a single authenticated tunnel for the SSH connection protocol. [STANDARDS-TRACK] This document specifies version 1.3 of the Transport Layer Security (TLS) protocol. TLS allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. This document updates RFCs 5705 and 6066, and obsoletes RFCs 5077, 5246, and 6961. This document also specifies new requirements for TLS 1.2 implementations. This document defines the core of the QUIC transport protocol. QUIC provides applications with flow-controlled streams for structured communication, low-latency connection establishment, and network path migration. QUIC includes security measures that ensure confidentiality, integrity, and availability in a range of deployment circumstances. Accompanying documents describe the integration of TLS for key negotiation, loss detection, and an exemplary congestion control algorithm. This document defines encoding rules for representing configuration data, state data, parameters of Remote Procedure Call (RPC) operations or actions, and notifications defined using YANG as JavaScript Object Notation (JSON) text. This document introduces use cases where Time-Variant Routing (TVR) computations (i.e., routing computations that take into consideration time-based or scheduled changes to a network) could improve routing protocol convergence and/or network performance. Huawei Individual Fraunhofer SIT Volta Networks Cisco This document defines a YANG data model for Event Condition Action (ECA) policy management. The ECA policy YANG module provides the ability to delegate some network management functions to the server (e.g., a NETCONF or RESTCONF server) which can take simple and instant action when a trigger condition on the managed objects is met. Jabil Huawei Technologies Juniper Networks Cisco Systems Inc Ciena Telefonica This document describes a data model for configuration scheduling.

Examples of Scheduling Format Representation This section provides some examples to illustrate the use of the period and recurrence formats defined in . The following modules are used for illustration purposes and make examples verifiable: For each example, only the message body is provided with JSON used for encoding per the guidance in .

The "generic-schedule-params" Grouping illustrates the example of a requested schedule that needs to start no earlier than 08:00 AM, January 1, 2025 and end no later than 8:00 PM, January 31, 2025 (Beijing time). Schedule requests that fail to meet the requirements are ignored by the system as indicated by "discard-action".

Generic Parameters with 'max-allowed-end' for Schedule Validation

To illustrate the difference between "max-allowed-end" and "validity" parameters, shows the example of a requested schedule that needs to start no earlier than 08:00 AM, January 1, 2025 (Beijing time), schedule requests that fail to meet the requirements are ignored by the system as indicated by "discard-action". The requested schedule may end after 8:00 PM, January 31, 2025, but any occurrences that are generated after that time would not be considered as valid.

Generic Parameters with 'validity' for Schedule Validation

The "period-of-time" Grouping shows an example of a period that starts at 08:00:00 UTC, on January 1, 2025 and ends at 18:00:00 UTC on December 31, 2027.

Simple Start/End Schedule

An example of a period that starts at 08:00:00 UTC, on January 1, 2025 and lasts 15 days and 5 hours and 20 minutes is encoded as shown in .

Simple Schedule with Duration

An example of a period that starts at 2:00 A.M. in Los Angeles on November 19, 2025 and lasts 20 weeks is depicted in .

Simple Schedule with Time Zone Indication

The "recurrence-basic" Grouping indicates a recurrence of every 2 days which starts immediately and repeats forever:

Simple Schedule with Recurrence

The "recurrence-utc" Grouping indicates a recurrence from 8:00 AM to 9:00 AM every day, from December 1 to December 31, 2025 in UTC:

Simple Schedule with Recurrence in UTC

The "recurrence-with-time-zone" Grouping indicates a recurrence of every 2 hours for 10 occurrences, lasting 10 minutes, and starting at 3 p.m. on December 1, 2025 in New York:

Simple Schedule with Recurrence with Time Zone Indication

The "recurrence-utc-with-periods" Grouping indicates a recurrence that occurs every two days starting at 9:00 AM and 3:00 PM for a duration of 30 minutes and 40 minutes respectively, from 2025-06-01 to 2025-06-30 in UTC:

Example of Recurrence With Date Times

The "recurrence-time-zone-with-periods" Grouping indicates a recurrence that occurs every 30 minutes and last for 15 minutes from 9:00 AM to 5:00 PM, and extra two occurrences at 6:00 PM and 6:30 PM with each lasting for 20 minutes on 2025-12-01 (New York):

Example of Advanced Recurrence Schedule

The "icalendar-recurrence" Grouping indicates 10 occurrences that occur at 8:00 AM (EST), every last Saturday of the month starting in January 2024:

Simple iCalendar Recurrence

is an example of a recurrence that occurs on the last workday of the month until December 25, 2025, from January 1, 2025:

Example of Advanced iCalendar Recurrence

indicates a recurrence that occurs every 20 minutes from 9:00 AM to 4:40 PM (UTC), with the occurrence starting at 10:20 AM being excluded on 2025-12-01:

Example of Advanced iCalendar Recurrence with Exceptions

The "schedule-status" Grouping indicates the scheduled recurrence status of at the time of 12:15 PM, 2025-12-01 (UTC):

Example of a Schedule Status

At the time of 12:15 PM, 2025-12-01 (UTC), the recurring event occurred at (note that occurrence at 10:20 AM is excluded): 9:00, 9:20, 9:40, 10:00, 10:40, 11:00, 11:20, 11:40, 12:00. The last occurrence was at 12:00, the upcoming one is at 12:20.

Examples of Using/Extending the "ietf-schedule" Module This non-normative section shows two examples for how the "ietf-schedule" module can be used or extended for scheduled events or attributes based on date and time.

Example: Schedule Tasks to Execute Based on a Recurrence Rule Scheduled tasks can be used to execute specific actions based on certain recurrence rules (e.g., every Friday at 8:00 AM). The following example module which "uses" the "icalendar-recurrence" grouping from "ietf-schedule" module shows how a scheduled task could be defined with different features used for options.

Example: Schedule Network Properties to Change Based on Date and Time Network properties may change over a specific period of time or based on a recurrence rule, e.g., . The following example module which augments the "recurrence-utc-with-periods" grouping from "ietf-schedule" module shows how a scheduled attribute could be defined. shows a configuration example of a link's bandwidth that is scheduled between 2025-12-01 0:00 UTC to the end of 2025-12-31 with a daily schedule. In each day, the bandwidth value is scheduled to be 500 Kbps between 1:00 AM to 6:00 AM and 800 Kbps between 10:00 PM to 11:00 PM. The bandwidth value that is not covered by the period above is 1000 Kbps.

Example of Scheduled Link's Bandwidth ne1 ne2 1000 2025-12-01T01:00:00Z schedule:daily 2025-12-31T23:59:59Z 360000 2160000 500 7920000 8280000 800 ]]>

Examples of Using "ietf-schedule" Module for Scheduled Use of Resources Framework This section exemplifies how the architecture for supporting scheduled reservation of Traffic Engineering (TE) resources in might leverage the "period-of-time" grouping defined in the "ietf-schedule" module to implement scheduled use of resources. The following example module shows how a scheduled link capacity reservation could be defined. defines the reference architecture for scheduled use of resources, the service requester sends a request to a Path Computation Element (PCE) and includes the parameters of the Label Switched Path (LSP) that the requester wishes to supply, the configuration example to provide the scheduled resource is shown in .

Example of Scheduled Link's Bandwidth Reservation 1 1-2-1 500 2025-03-10T08:00:00Z 2025-03-10T09:00:00Z 2 2-1-1 400 2025-04-01T00:00:00Z PT09:00:00 3 2-1-1 500 2025-04-01T09:00:00Z 2025-04-01T23:59:59Z ]]>

Acknowledgments This work is derived from the . There is a desire from the OPSAWG to see this model be separately defined for wide use in scheduling context. Thanks to Adrian Farrel, Wei Pan, Tianran Zhou, Joe Clarke, Steve Baillargeon, Dhruv Dhody, Robert Wilton, and Italo Busi for their valuable comments and inputs to this work. Many thanks to the authors of , , and for the constructive discussion during IETF#118. Other related efforts were explored in the past, e.g., . Thanks to Reshad Rahman for the great YANG Doctors review, Mahesh Jethanandani for the AD review, and Per Andersson for the OPSDIR review.