| Internet-Draft | Schedule Framework | July 2024 |
| Ma, et al. | Expires 26 January 2025 | [Page] |
This document presents a framework that elucidates various scheduling scenarios and identifies the entities involved in requesting scheduled changes of network resources or policy/action execution. It also addresses additional challenges such as conflict resolution, priority handling, and synchronization of scheduled tasks, ultimately enhancing the reliability and performance of network services.¶
This document also describes the applicability of various network management tools and data models may be used, to meet the requirements of a set of representative use cases.¶
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 26 January 2025.¶
Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights 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.¶
Scheduling-related tasks are usually considered for efficient and deterministic network management. Such scheduling may be characterized as simple recurrent tasks such as planned activation/deactivation of some network accesses, or can be more complex such as scheduling placement of requests and planned invocation of resources to satisfy service demands or adhere to local networks policies. Many common building blocks are required for all these cases for adequate management of schedules and related scheduled actions.¶
This document presents a framework for the scheduled use of resources within network environments, utilizing the IETF YANG models designed for scheduling of network resources.¶
The framework describes how IETF data models (e.g., [I-D.ietf-netmod-schedule-yang]) can streamline the management and orchestration of network events, policies, services, and resources based on precise date and time parameters. By leveraging these YANG modules, this framework facilitates interoperable and efficient scheduling mechanisms that enhance the predictability, coordination, and optimization of network operations.¶
The document also provides guidelines for implementing scheduling capabilities across diverse network architectures, ensuring that resources are allocated and utilized in a timely and effective manner.¶
In addition, the document outlines several challenges that must be considered when deploying control mechanisms for scheduling network resources, including:¶
Discover where and what scheduling state is held.¶
Specify to apply schedule policies and detect and resolve conflicts.¶
Ensure synchronization of scheduled resources across distributed systems.¶
Establish a scalable and resilient scheduling system.¶
Ensure that a scheduling system can scale to accommodate complex networks with numerous resources and scheduling requests.¶
Ensure that the a scheduling system remains operational and can recover from failures or disruptions, providing redundancy, failover mechanisms, and robust error handling.¶
Secure scheduled resources.¶
Identify what mechanisms and policies could be applied to protect scheduling data and operations from unauthorized access and ensuring that only authorized entities can create, modify, or retrieve schedules.¶
Editors Note: pointers to sections where each of these items is described will be provided in future version.¶
Key use cases highlight how the proposed framework can be used for scheduling scenarios. The applicable IETF YANG modules are described, as well as other dependencies that are needed.¶
[Editors Note] In future versions of this document, an appendix will also provide JSON examples.¶
Efficient and coordinated use of resources is paramount for maintaining optimal performance and reliability of many network environments. Networks are increasingly complex, supporting a wide variety of services and applications that require precise timing and resource allocation. Despite advancements in networking techniques and the richness of protocols machinery, there is still a lack of reference architectures for scheduling resources based on specific date and time parameters. This gap often leads to inefficiencies, conflicts, and suboptimal utilization of network capabilities.¶
Typically, network administrators rely upon disparate and often proprietary tools to manage scheduling for various network activities such as maintenance events, policy enforcement, and resource allocation. These tools genrally operate in isolation, lacking interoperability and integration with other network management systems. As a result, administrators face significant challenges in coordinating schedules, resolving conflicts, and ensuring that critical tasks are executed without disruption. The absence of a unified scheduling framework exacerbates these issues, leading to increased operational overhead and potential service degradation (e.g., lack of integration with service impact analysis).¶
Furthermore, the dynamic nature of some networks demands a flexible and adaptive scheduling solution that can respond to changing conditions and requirements. Existing scheduling approaches are often rigid and static, unable to accommodate the fluid demands of network services and applications. This rigidity hinders the ability to optimize resource use and respond proactively to network events, impacting the overall efficiency and effectiveness of network operations.¶
To address these challenges, there is a clear need for a standardized framework that can provide a cohesive approach to scheduling network resources. Such a framework leverages existing YANG models to ensure compatibility and ease of integration with current network management practices. By standardizing the scheduling process, network operators can achieve greater predictability, reduce conflicts, and optimize the use of network resources, thereby enhancing the performance and reliability of their networks.¶
There is an existing framework [RFC8413] for the use of scheduled resources. This document outlines a framework detailing the architecture for supporting the scheduled reservation of Traffic Engineering (TE) resources. It focuses on the conceptual and architectural aspects, without delving into specific protocols or protocol extensions required to implement this service.¶
More recently, several specifications include a provision for scheduling. Examples of such specifications are (but not limited to) [I-D.ietf-opsawg-ucl-acl], [I-D.contreras-opsawg-scheduling-oam-tests], and [I-D.ietf-tvr-schedule-yang]. The development of [I-D.ietf-netmod-schedule-yang] is intended to be served as common building blocks and provides a common schedule YANG module that can be reused in scheduling contexts such as event, policy, services, or resources based on date and time.¶
Combined, [I-D.ietf-netmod-schedule-yang] and other documents built on top of it (e.g., [I-D.ietf-opsawg-ucl-acl], [I-D.contreras-opsawg-scheduling-oam-tests], and [I-D.ietf-tvr-schedule-yang]) provide powerful capabilities for the control and scheduling of network resources for several use cases, including key examples outlined in this document.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The following terms are used in this document:¶
An entity that issues a scheduling request of network events, policies, services, and resources.¶
An entity that handles scheduling requests from a Schedule Service Requester.¶
A functional entity that is managing the scheduling operations.¶
A functional entity that is responsible for enforcing a set of polices or rules in the network.¶
Figure 1 presents the referenced architecture for the control scheduling of network resources.¶
+-------------------------------------------------+
| Schedule Service Requester |
+-----+------------------------------------^------+
| |
|Request |Response
| |
+-----v------------------------------------+------+
| Schedule Service Responder |
| |
| +---------+ +---------+ |
| | | | | |
| | Schedule| | Conflict| |
| | Manager | | Resolver| |
| | | | | |
| +---------+ +---------+ |
| |
| +---------+ +---------+ |
| | | | | |
| | Resource| | Policy | |
| | Manager | | Engine | |
| | | | | |
| +---------+ +---------+ |
| |
+----------------------+--------------------------+
|
|
|
|
+---------------------------+-----------------------------+
| Network Resources and Inventory |
+---------------------------------------------------------+
The entity requesting a resource schedule change can vary widely. For example, a network administrator may seek to restrict or limit access to specific network resources based on day or time to optimize performance and enhance security.¶
Additionally, higher-layer Operations Support System (OSS) components may impose restrictions on network resources in response to changing network conditions, ensuring service continuity and compliance with operational policies. Automated systems and AI-driven components can also request dynamic adjustments based on real-time data, facilitating predictive maintenance and optimizing resource usage to maintain peak network efficiency.¶
This component is responsibile handling scheduling orders. That is, this entity manages and coordinates all network scheduling activities. The extact internal structure of this entity is deployment-specific; however this document describes an example internla decomposition of this entity:¶
Manages the network resources that are subject to scheduling.¶
Handles creation, modification, deletion, and querying of schedules.¶
Detects and resolves scheduling conflicts based on predefined policies and priorities.¶
Enforces scheduling policies and rules, ensuring compliance with organizational requirements.¶
Examples of a schedule service responder may be a network controller, network management system or the network device itself.¶
To support the scheduling of network resources effectively, several functional interfaces are required. These interfaces interconnect different components of the network scheduling system, ensuring seamless integration and operation, these include:¶
Schedule resource order creation, order modification, and deletion requests and responses. Querying of current and upcoming schedules, conflict and alert notifications.¶
Manages interactions with the network resources, inventory systems, planning systems, etc. Capable of querying available resources, allocating and deallocating resources based on current schedule plan, and monitoring resource utilization.¶
When scheduling network resources, a variety of data sources are required to accurately assess the network state and make informed scheduling decisions. Here are some example data sources that will be required:¶
Connection details about the physical and logical layout of the network, including nodes, ports/links, and interconnections.¶
A comprehensive list of deployed network resources that are not currently in service, but may be available if enabled.¶
Real-time data on the current usage of network resources, including bandwidth consumption, CPU load, memory usage, and power consumption.¶
Past data on the current usage of network resources, including bandwidth consumption, CPU load, memory usage, and power consumption.¶
Information on planned maintenance activities, scheduled downtimes, and service windows.¶
It is critical to leverage these diverse data sources, so network administrators and automated systems can make well-informed scheduling decisions that optimize resource utilization, maintain network performance, and ensure service reliability.¶
The scheduling state is maintained in the schedule manager, which is responsible for the creation, deletion, modification, and query of scheduling information.¶
Groupings "schedule-status" and "schedule-status-with-name" in the "ietf-schedule" YANG module [I-D.ietf-netmod-schedule-yang] define common parameters for scheduling management, including status exposure.¶
Policies are a set of rules to administer, manage, and control access to network resources. For example, the following shows an example of a scheduled ACL policy:¶
drop TCP traffic source-port 16384 time 2025-12-01T08:00:00Z /2025-12-15T18:00:00Z¶
A set of scheduling policies and rules are maintained by the policy engine, which is responsible for the policy enforcement. Policies are triggered to execute at a certain time based on the scheduling parameters. Each policy might be executed multiple times, depending on the its scheduling type (one-shot vs. recurrence).¶
It is critical to ensure all network schedule entities, including controllers and management systems are synchronized to a common time reference. System instability and unpredictability might be caused if there is any time inconsistencies between entities that request/respond to policies or events based on time-varying parameters. Several methods are available to achieve this.¶
This document is not intended to define any YANG modules, but shows how existing schedule-related YANG modules could fit into this framework. The following provides a list of applicable YANG modules that can be used to exchange data between schedule service requester and responder:¶
[I-D.ietf-netmod-schedule-yang] defines "ietf-schedule" YANG module for scheduling that works as common building blocks for YANG modules described in this section. The module doesn't define any protocol-accessible nodes but a set of reusable groupings applicable to be used in any scheduling contexts.¶
The "ietf-ucl-acl" YANG module defined in [I-D.ietf-opsawg-ucl-acl] augments the IETF Access Ccontrol List (ACL) model [RFC8519] with schedule parameters to allow each Access Control Entry (ACE) to be activated based on date and time conditions.¶
The "ietf-tvr-node" YANG module in [I-D.ietf-tvr-schedule-yang] which is a device model, is designed to manage a single node with scheduled attributes (e.g., powered on/off).¶
The "ietf-tvr-topology" YANG module in [I-D.ietf-tvr-schedule-yang] is used to manage the network topology with time-varying attributes (e.g., node/link availability, link bandwidth, or delay).¶
The "ietf-oam-unitary-test" in [I-D.contreras-opsawg-scheduling-oam-tests] defines how to perform scheduled network diagnosis using (Operations, Administration, and Maintenance) OAM unitary test.¶
The "ietf-oam-test-sequence" in [I-D.contreras-opsawg-scheduling-oam-tests] is defined to perform a collection of OAM unitary tests based on date and time constraints.¶
Schedules execution means that a component (e.g., device) undertakes an action (e.g., allocates and deallocates resources) at specified time points. The schedule executor should fully understand the consequences of the schedule execution. For example, when a schedule's execution affects the network topology, the addition and deletion of the topology need to be considered carefully.¶
A link coming up or a node joining a topology should not have any functional change until the change is proven to be fully operational. The routing tables or paths could be pre-computed but should not be installed before all of the topology changes are confired to be operational. The benefits of this pre-computation appear to be very small. The network may choose to not do any pre-installation or pre-computation in reaction to topological additions, at a small cost of some operational efficiency.¶
Topological deletions are an entirely different matter. If a link or node is to be removed from the topology, then the network should act before the anticipated change to route traffic around the expected topological loss. Specifically, at some point before the topology change, the routing tables or paths should be pre-computated and installed before the topology change take place. The time necessary will vary depending on the exact network and configuration. When using IGP or other distributed routing protocols, the affected links may be set to a high metric to direct traffic to alternate paths. This type of change does require some time to propagate through the network, so the metric change should be initiated far enough in advance that the network converges before the actual topological change.¶
This sections presents some outstanding dependencies that need to be considered when deploying the scheduling mechanism. This may not be exhaustive.¶
Access control ensures only authorized control entities can have access to schedule information, including querying, creation, modification, and deletion of schedules. Unauthorized access may lead to unintended consequences.¶
The Network Access Control Model (NACM) [RFC8341] provides standard mechanisms to restrict access for particular uses to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.¶
Atomic operations are guaranteed to be either executed completely or not executed at all. Deployments based on scheduling must ensure schedule changes based on recurrence rules are applied as atomic transactions. Either all changes are successfully applied, or none at all. For example, a network policy may be scheduled to be active every Tuesday in January of 2025. If the schedule is changed to every Wednesday in January 2025, the recurrence set is changed from January 7, 14, 21, 28 to January 1, 8, 15, 22, 29. If some occurrences can not be applied successfully (e.g., January 1 cannot be scheduled because of conflict), the others in the recurrence set will not be applied as well.¶
In addition, the scheduling management of network events, policies, services, and resources may involve operations that are performed at particular future time(s). Multiple operations might be involved for each instance in the recurrence set, either all operations are successfully performed, or none at all.¶
Rollback mechanism is useful to ensure that in case of an error, the system can revert back to its previous state. Deployments are required to save the checkpoints (manually or automatically) of network scheduling activities that can be used for rollback when necessary, to maintain network stability.¶
Enfrocement of some secheduled actions may depend on other schedules actions. Means to identify such dependency are needed.¶
This document does not make any assumption about the number of schedule service requester entities that interact with schedule service responder. This means that multiple schedule service requesters may send requests to the responder to schedule the same network resources, which may lead to conflicts. If scheduling conflicts occur, some predefined policies or priorities may be useful to reflect how schedules from different sources should be prioritized.¶
Time synchronization may potentially lead to security threats, e.g., attackers may modify the system time and it thus causes time inconsistencies and affects the normal functionalities for managing and coordinating network scheduling activities. In addition, 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.¶
This document has no IANA actions.¶
Operations, Administration, and Maintenance (OAM) are important networking functions for network monitoring and troubleshooting, as well as service-level agreements and performance monitoring. Some actions might need to be executed repeatedly or at a specific future time to carry out diagnostics. Scheduling-based OAM tools are able to invoke a specific OAM unitary test or a sequence of OAM tests based on some time-varying parameters, e.g., at a precise future time or repeatedly occur at specific intervals.¶
Suppose the following fictional module is used:¶
module example-oam-tests {
yang-version 1.1;
namespace "urn:example:oam-tests";
prefix "ex-oam";
import ietf-schedule {
prefix "schedule";
}
list oam-test {
key "test-name";
leaf test-name {
type string;
}
uses schedule:recurrence-utc;
}
}
¶
The following indicates the example of a scheduling OAM traceroute test that is executed at 3:00 AM, every other day, from December 1, 2025 in UTC. The JSON encoding is used only for illustration purposes.¶
{
"example-oam-tests:oam-test": [
{
"test-name": "traceroute",
"recurrence-first": {
"utc-start-time": "2025-12-01T03:00:00Z"
},
"frequency": "ietf-schedule:daily",
"interval": 2
}
]
}
¶
Tidal network is a typical scenario of Energy Efficient case. The tidal network means the volume of traffic in the network changes periodically like the ocean tide. This changes are mainly affected by human activities. Therefore, this tidal effect is obvious in human-populated areas, such as campuses and airport.¶
In the context of a tidal network, If the network maintains all the devices up to guarantee the maximum throughput all the time, a lot of power will be wasted. The energy-saving methods may include the deactivation of some or all components of network nodes. These activities have the potential to alter network topology and impact data routing in a variety of ways. Interfaces on network nodes can be selectively disabled or enabled based on traffic patterns, thereby reducing the energy consumption of nodes during periods of low network traffic.¶
The controlling of the interface states of each node can be achieved by using the ietf-tvr-node YANG module defined in [I-D.ietf-tvr-schedule-yang].¶
The following indicates the example of a scheduling node that is powered on from 12 AM, December 1, 2025 to 12 AM, December 1, 2026 in UTC and its interface named interface1 is scheduled to enable at 7:00 AM and disabled at 1:00 AM, every day, from December 1, 2025 to December 1, 2026 in UTC. The JSON encoding is used only for illustration purposes.¶
{
"ietf-tvr-node:node-schedule":[
{
"node-id":12345678,
"node-power-schedule":{
"power-default":false,
"schedules":[
{
"schedule-id":111111,
"period-start":"2025-12-01T00:00:00Z",
"period-end":"2026-12-01T00:00:00Z",
"attr-value":{
"power-state":true
}
}
]
},
"interface-schedule":[
{
"name":"interace1",
"default-available":false,
"default-bandwidth":1000000000,
"attribute-schedule":{
"schedules":[
{
"schedule-id":222222,
"recurrence-first":{
"utc-start-time":"2025-12-01T07:00:00Z",
"duration":64800
},
"utc-until":"2026-12-01T00:00:00Z",
"frequency":"ietf-schedule:daily",
"interval":1,
"attr-value":{
"available":true
}
}
]
}
}
]
}
]
}
¶
TODO acknowledge.¶