]> Huawei

chengen@huawei.com

Orange

mohamed.boucadair@orange.com

Huawei

bill.wu@huawei.com

Telefonica

luismiguel.contrerasmurillo@telefonica.com

Individual

marisol.ietf@gmail.com

Operations and Management GREEN Working Group Energy Efficient Energy Saving Energy Management Energy-efficient network management is primarily meant to enhance conventional network management with energy-related management capabilities that optimize overall network energy consumption. To that aim, specific features and capabilities are required to control (and thus optimize) the energy use of involved network elements and their components. This document defines a set of key terms used within the IETF when discussing energy efficiency in network management. Such reference document helps framing discussion and agreeing upon a set of main concepts in this area. Discussion Venues Discussion of this document takes place on the Getting Ready for Energy-Efficient Networking Working Group mailing list (green@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction With rising energy costs and increasing awareness of the environmental impact of running networks, servers, and various equipment, Energy Efficiency is considered by operators as a critical component to be integrated in the overall Network Management systems. Such integration is ambitioned to feed strategies for achieving environmental objectives but also mastering related operational cost. Energy Efficiency Management is thus complementing conventional network management. defines a set of terms used within the IETF when discussing energy-efficient networks. The purpose is to (1) ensure consistent use of a set of terms in this area, (2) help with the characterization of Energy Efficiency (and relevant aspects), (3) assist in the development of the YANG data models at the different levels in the IETF, and (4) bring clarity to the Energy Efficiency related discussions between different groups within the IETF, in particular. This document does not intend to define an exhaustive list of energy-related terms. Only key terms are defined. Some of these terms are extracted from existing IETF documents and beyond. Also, provides an inventory of currently used metrics to assess/compute energy-related consumption, efficiency ratio, etc. provides a list of SDOs where relevant energy efficiency effort is ongoing.

Abbreviations The following abbreviations are used in the document:

CLEE:

Component Level Energy Efficiency

DLEE:

Device Level Energy Efficiency

DSLAM:

Digital Subscriber Line Access Multiplexer

EER

Energy Efficiency Ratio

GEPON:

Gigabit Ethernet Passive Optical Network

GPON:

Gigabit-capable Passive Optical Network

MSAN:

Multiservice Access Node

NDR:

Non-Drop Rate

NLEE:

Network Level Energy Efficiency

PUE:

Power Usage Effectiveness

SLEE:

Service Level Energy Efficiency

Definitions Terms are listed so that terms that are needed to understand other terms are listed first.

Energy:

Is generally a reference to electrical energy and is measured in kilowatt-hours (kWh) .

Energy Object:

Represents an equipment that is part of, or attached to, a communication network that is monitored or controlled or that aids in the management of another device for Energy Management.

Power:

Refers to the time rate at which energy is emitted, transferred, or received. Power is usually expressed in watts (joules per second) .

Nameplate Power:

The maximum continuous power a hardware component is designed to consume or deliver, as specified by the manufacturer. It is a rated design value, not an expected operating one, and does not change during operation. For any supported Power State, the power drawn in that state must not exceed the Nameplate Power of the component.

Device:

A piece of electrical or non-electrical equipment. Adapted from .

Component:

Is a part of electrical or non-electrical equipment (device). Adapted from .

Meter (Energy Meter):

Is a device (or component) that is intended to measure electrical energy by integrating power with respect to time. Adapted from .

Power Inlet (inlet, for short):

Is an interface at which a device (or component) receives energy from another device (or component) .

Power Outlet (outlet, for short):

Is an interface at which a device (or component) provides energy to another device (or component) .

Power Interface:

Is a power inlet, outlet, or both .

Power State:

Is a condition or mode of a device (or component) that broadly characterizes its capabilities, power, and responsiveness to input. Adapted from .

Power State Set:

Is a collection of Power States that comprises a named or logical control grouping.

Power Source:

Is any device, component that generates, stores, or supplies electrical or mechanical energy to a circuit or device.

Power Factor:

Is the percent value between 0 and 1 that measures how effectively electrical power is being converted into useful work. It represents the ratio of real power (work done) to apparent power (total power supplied) on a scale from 0 to 1. For energy objects powered by a Direct Current (DC)' power source, the power factor is typically considered to be 1. This information is important for understanding the electrical characteristics of the energy object and for correctly interpreting the power data.

Energy Management:

Is a set of functions for measuring, modeling, planning, and optimizing networks to ensure that the network and network-attached devices use energy efficiently and appropriately for the nature of the application and the cost constraints of the organization ().

Energy Management System (EnMS):

A combination of hardware and software used to administer a network, with the primary purpose of Energy Management.

Energy Monitoring:

Is a part of Energy Management that deals with collecting or reading information from devices to aid in Energy Management .

Energy Control:

Is a part of Energy Management that deals with directing influence over devices .

This control can span a network or a subset of it.

Energy Saving:

A reduction in total energy consumption, typically measured against a baseline or per unit of output, rather than just a month-on-month decrease.

Energy Efficiency:

Refers to optimizing energy usage in network components, devices, and across the network to minimize energy use as much as possible, thus eliminating energy waste. Examples to improve Energy efficiency include, but are not limited to, deactivation of some or all components of network nodes during specific periods (e.g., periods with low traffic), adjusting the speed of an interface based on network traffic load changes, switching to more efficient power supplies and silicon, or developing more efficient transmission or signal processing algorithms.

Energy Efficiency Management:

Refers to a set of processes used to maintain an inventory of capabilities, use specific metrics to measure, report, and assess energy consumption of the network, and control the use of available energy in an optimized manner. The overall goal is to ensure that the network and underlying devices use energy in a resource-conserving manner and at low cost for the nature of the the services it provides and the cost constraints while achieving the network's functional and performance requirements (e.g., improving overall network utilization).

Energy Efficiency Observability:

Is a component of Energy Efficiency Management that deals with collecting, reporting, and reading metrics information from devices and evaluating the effectiveness of energy-aware policies to aid in Energy Efficiency Management.

Energy Efficiency Control:

Is a component of Energy Efficiency Management that deals with directing influence over devices.

Energy Efficiency Capabilities:

Network Capabilities to optimize energy usage in network components, devices, and across the network through configurable static attributes (e.g., power saving capable attribute which can be applied to both component level and device level, or power setting attributes which specify absolute power, relative power, who provide power, who consume, who is the meter, measurement frequency, or temperature setting, voltage, ampere setting).

Energy Efficiency Metric:

Refers to a metric that is used for the assessment of energy consumption of a network, device, or component. One or more metrics can be defined. These metrics are also used for network performance purposes to characterize the effectiveness of an Energy Efficiency management strategy. Developing energy efficiency metrics for internetworking and associated measurement methodologies and conditions as well as consistently collecting this data over time are essential to demonstrating Energy Efficiency improvements. An example of a common outcome-oriented metric is energy consumption per data volume or traffic unit.

Energy Proportionality

Is the correlation between energy used and the associated useful output. In networking, this is generally interpreted as the proportionality of traffic or traffic throughput and energy used. This concept is broadly applicable to networking infrastructures, data centers, and other communication architectures. There might not be a one-to-one correlation between traffic and energy use, notably due to the materially significant idle power use by devices, as well as the overall network capacity being allocated to serve at times of highest traffic utilization.

Energy Efficiency/Energy Efficiency Ratio (EER):

The energy efficiency is expressed as the ratio between the useful output and input of an energy conversion process of a network, device, or component.

For instance, in relation with a networking device, it can be stated as the ratio of throughput to the weighted power consumed (bits/Joule). In this context, the throughput metric may be taken either as the aggregate maximum non-drop forwarding rate across all interfaces of a networking device or as a weighted sum of the above mentioned maximum non-drop throughputs, where the weights reflect the intended traffic load distribution.

A higher EER value indicates a better energy efficiency.

Energy-Aware Intent:

A declarative, technology-agnostic expression of an energy-related operational objective for the network. Unlike imperative configurations that specify exactly how to achieve a result, an energy-aware intent focuses on what energy behavior is desired (e.g., minimize power consumption or optimize energy-to-throughput ratios), leaving the system to determine the best enforcement method.

Energy-aware intents are interpreted by network management or orchestration systems, which translate them into actionable control logic, such as powering down interfaces, reducing link speeds. These intents enable policy-driven, automated, and potentially closed-loop energy optimization aligned with business goals.

Power Usage Effectiveness (PUE):

Refers to the metric used to measure the energy efficiency of an infrastructure.

This metric is calculated as the ratio between the total energy consumed by an infrastructure and the energy needed for a network element/component.

Network Level Energy Efficiency (NLEE):

Denotes the Energy Efficiency of an entire network or a subset part of it (e.g., access network).

Device Level Energy Efficiency (DLEE):

Denotes the Energy Efficiency of a network element. It can be used, e.g., to compare network elements providing the same functionality or a target to optimize the configuration of a network element. In this context, "Device Level" is equivalent to "System Level", which is considered as a "single device" or "single entity" from the measurement and reporting perspective.

Component Level Energy Efficiency (CLEE):

Denotes the Energy Efficiency of a component of a network element. It can be used in the design, development, and manufacturing of energy efficient network elements. Here "Component Level" is equivalent to "Sub-System Level", which is considered as an "abstract " or "incomplete specification" of a portion of a system from the measurement and reporting perspective.

CLEE is useful to evaluate the energy efficiency performance of individual components of a network element.

Measuring and understanding the energy efficiency or energy consumption of each component within a network element may be used to identify key components in a system with regard to energy saving.

Service Level Energy Efficiency (SLEE):

Denotes the total energy consumption attributed to delivering a specific service or application within a network segment.

SLEE enables operators to measure and report the per-service energy footprint, providing valuable insights for operational benchmarking, and capacity planning.

Sample Energy Efficiency Metrics and Measurement Methods This section lists some metrics that are adopted by other SDOs.

• DISCUSS: Should we maintain this section?

Metrics for Access Equipment Access Equipment with line cards working at different profiles/states are characterized with different metric values for each specific profile/state. Where:

• 'Peq' is the power (in watts) of a fully equipped wireline network equipment with all its line cards working in a specific profile/state.
• 'Nports' is the maximum number of ports served by the broadband network equipment under test.

The formula is defined in .

Metric for Wireless Access Technologies The energy efficiency metric at Radio Frequency (RF) unit level is as follows: Where:

• 'Eoutput' is daily RF output energy consumption [Wh] under different load.
• 'Erfu' is daily RF units energy consumption [Wh] under different load.

The formula is defined in .

Metrics for Routers and Ethernet Switches The metric for routers and Ethernet switches is as follows: Where 'Ti' is NDR throughput, 'Pw' is weighted power (energy consumption rate). The formula is defined in . Where:

• 'a'/'b'/'c' are the relative weight at different usage percentage with a+b+c=1.
• 'Pu1'/'Pu2'/'Pu3' are the power at different usage percentage.

Metrics for Small Network Devices A metric for small networking devices intended for home/domestic or small office use is as follows: Where Ti is NDR throughput between wide area network (WAN) and local area network (LAN) ports in the ingress direction, Pw is the average power during Full load, Idle load and Low power, the formula is defined in . where:

• (0.35,0.5,0.15) is the relative weight at different usage mode.
• 'P_idle'/'P_lowpower'/'P_maximum' is the average power at different usage mode.
• 'T_idle'/'T_lowpower'/'T_maximum' is NDR throughput at different usage mode.

Metric for Power Equipment Where:

• 'Po' is output power.
• 'Pi' is input power.

This energy efficiency value is measured or calculated from the testing data over a given time period. The formula is defined in .

Metric for Cooling Equipment Where:

• 'η' is the energy efficiency of the air conditioner.
• 'Pi' is the input power.
• 'Qt' is the sum of the sensible cooling capacity and the latent cooling capacity.

The formula is defined in .

Operations and Manageability Considerations This document defines terminology intended to ensure consistency among various efforts and deployment levels. No other operations or manageability requirements are introduced by this document.

Security Considerations Security is not discussed in this document.

Informative References This document defines a framework for Energy Management (EMAN) for devices and device components within, or connected to, communication networks. The framework presents a physical reference model and information model. The information model consists of an Energy Management Domain as a set of Energy Objects. Each Energy Object can be attributed with identity, classification, and context. Energy Objects can be monitored and controlled with respect to power, Power State, energy, demand, Power Attributes, and battery. Additionally, the framework models relationships and capabilities between Energy Objects. Intent and Intent-Based Networking are taking the industry by storm. At the same time, terms related to Intent-Based Networking are often used loosely and inconsistently, in many cases overlapping and confused with other concepts such as "policy." This document clarifies the concept of "intent" and provides an overview of the functionality that is associated with it. The goal is to contribute towards a common and shared understanding of terms, concepts, and functionality that can be used as the foundation to guide further definition of associated research and engineering problems and their solutions. This document is a product of the IRTF Network Management Research Group (NMRG). It reflects the consensus of the research group, having received many detailed and positive reviews by research group participants. It is published for informational purposes.

Standards Bodies and Standards This appendix provides a list of SDOs where relevant energy efficiency effort is ongoing. This appendix does not aim to be comprehensive. The appendix may be removed in future versions of the document.

ITU-T SG5 ITU-T Study Group 5 (SG5) has already worked on developing standards on energy efficiency. ITU-T SG5 has many standards in the environment efficiency field. These standards include , , , and covering energy efficiency terminology, framework, metrics, and measurement methods. ITU-T SG5 is also responsible for other standards that might be of interest to protocol developers and network operators. For example:

• specifies assessment of mobile network energy efficiency.
• specifies the correlation between the carbon intensity indicator and energy efficiency metric. The carbon KPI defined in refers to the energy efficiency metric defined in ITU-T L.1331.
• focuses on the assessment of the environmental impact of information and communication technology (ICT) goods, networks and services. It provides specific guidance on energy and greenhouse gas (GHG) impacts.

ETSI TCEE ETSI Technical Committee (TC) Environment Engineering (EE) is collaborating with ITU-T SG5 to develop technically aligned standards on energy efficiency and environment aspect. These standards include energy efficiency, power feeding solution, circular economy and network efficiency KPI and eco-design requirement for ICT, with the aim to build an international eco-environmental standardization. defines the energy consumption metrics and measurement methods for router and Ethernet switch equipment. It specifies a methodology and the test conditions to measure the power consumption of router and switch equipment and is also applicable to Core, edge, and access routers.

3GPP SA5 3GPP SA5 has, in Release 17, extended its scope from RAN only to the whole 5G System (5GS) and worked on Energy Efficiency (EE) and Energy Saving (ES) of mobile networks. EE Key Performance Indicators (KPI) have been defined for the 5G Core network and Network Slices. The 3GPP Energy Efficiency in the RAN is defined by the performance divided by the Energy Consumption (EC), where the definition of the performance depends on the type of network entity it applies to. From this, SA5 work aimed at defining the best metrics for each of them, and their measurement method. In Rel-18, WG SA5 works with ETSI NFV to explore more accurate virtual CPU usage measurements from ETSI NFV MANO, Introduce additional metrics when estimating the Energy Consumption of Virtual Machines, e.g., their virtual disk or link usage. In addition new use cases for Energy Saving, applied to NG-RAN, 5GC, and Network Slicing, AI/ML assisted energy saving scenarios are also being investigated. Specifically, defines a number of energy efficiency KPIs, including a generic Network Slice Energy Efficiency KPI, defined as the ratio between the performance of the network slice and its energy consumption.

Changes between Revisions v02 - v03

• Remove powerbench reference, allow powerbench draft reference this draft.
• Update Nameplate power to align with YANG data model WG draft and Capability discovery discussion.
• Clarify the throught meric calculation and weight definition.
• Other Editorial changes.

v01 - v02

• Moving Power factor and EnMS from framework draft to terminology draft
• Add the Nameplate Power definition
• Add Power Source Definition
• Add remaining EnMS related terminologies to terminology draft
• Add missing external references

v00 - v01

• Add two terms including Energy Object and energy saving.
• Update powerbench reference into WG draft.
• Generalized DSLAM, MSAM GPON GEPON equipment into Access equipment.

v03 - v04

• Add Shailesh Prabhu as contributor.
• Add one new definition on Service Level Energy Efficiency (SLEE).
• Add one new definition on Energy-Aware Intent.
• Update Device Level Energy Efficiency definition and Component Level Energy Efficiency, clarify their relation with system level and sub-system level.
• Other Editorial changes.

v02 - v03

• Update Energy Efficiency Capability Definition.
• Change Marisol's affiliation.

v01 - v02

• Add one new section on Operations and Manageability Considerations;
• Add three new energy efficiency related terms based on comments raised during the interim meeting;
• Update 4 existing terms such as energy efficiency definition, energy efficiency metric, energy efficiency capabilities energy proportionality based on comments raised on the list.

Acknowledgments This work has benefited from the discussions that occurred during GREEN interim meeting and on GREEN mailing list. Thanks Benoit Claise, Gen Chen, Emile Stephan, Rob Wilton for valuable review and comments. Thanks Peter Liu for helping provide input to initial version of the draft.

Contributors Nokia

shailesh.prabhu@nokia.com