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+Internet Engineering Task Force (IETF)                   J. Quittek, Ed.
+Request for Comments: 6988                               NEC Europe Ltd.
+Category: Informational                                  M. Chandramouli
+ISSN: 2070-1721                                      Cisco Systems, Inc.
+                                                               R. Winter
+                                                                T. Dietz
+                                                         NEC Europe Ltd.
+                                                               B. Claise
+                                                     Cisco Systems, Inc.
+                                                          September 2013
+
+
+                   Requirements for Energy Management
+
+Abstract
+
+   This document defines requirements for standards specifications for
+   Energy Management.  The requirements defined in this document are
+   concerned with monitoring functions as well as control functions.
+   Monitoring functions include identifying energy-managed devices and
+   their components, as well as monitoring their Power States, Power
+   Inlets, Power Outlets, actual power, Power Attributes, received
+   energy, provided energy, and contained batteries.  Control functions
+   include such functions as controlling power supply and Power State of
+   energy-managed devices and their components.
+
+   This document does not specify the features that must be implemented
+   by compliant implementations but rather lists features that must be
+   supported by standards for Energy Management.
+
+Status of This Memo
+
+   This document is not an Internet Standards Track specification; it is
+   published for informational purposes.
+
+   This document is a product of the Internet Engineering Task Force
+   (IETF).  It represents the consensus of the IETF community.  It has
+   received public review and has been approved for publication by the
+   Internet Engineering Steering Group (IESG).  Not all documents
+   approved by the IESG are a candidate for any level of Internet
+   Standard; see Section 2 of RFC 5741.
+
+   Information about the current status of this document, any errata,
+   and how to provide feedback on it may be obtained at
+   http://www.rfc-editor.org/info/rfc6988.
+
+
+
+
+
+
+Quittek, et al.               Informational                     [Page 1]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+Copyright Notice
+
+   Copyright (c) 2013 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
+   (http://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 Simplified BSD License text as described in Section 4.e of
+   the Trust Legal Provisions and are provided without warranty as
+   described in the Simplified BSD License.
+
+Table of Contents
+
+   1. Introduction ....................................................3
+      1.1. Conventional Requirements for Energy Management ............3
+      1.2. Specific Requirements for Energy Management ................4
+   2. Terminology .....................................................5
+   3. General Considerations Related to Energy Management .............6
+      3.1. Power States ...............................................7
+      3.2. Saving Energy versus Maintaining Service Level .............7
+      3.3. Local versus Network-Wide Energy Management ................7
+      3.4. Energy Monitoring versus Energy Saving .....................8
+      3.5. Overview of Energy Management Requirements .................8
+   4. Identification of Entities ......................................9
+   5. Information on Entities ........................................10
+      5.1. General Information on Entities ...........................10
+      5.2. Power Interfaces ..........................................11
+      5.3. Power .....................................................13
+      5.4. Power State ...............................................15
+      5.5. Energy ....................................................17
+      5.6. Battery State .............................................18
+      5.7. Time Series of Measured Values ............................19
+   6. Control of Entities ............................................21
+   7. Reporting on Other Entities ....................................21
+   8. Controlling Other Entities .....................................22
+      8.1. Controlling Power States of Other Entities ................22
+      8.2. Controlling Power Supply ..................................23
+   9. Security Considerations ........................................23
+   10. Acknowledgments ...............................................25
+   11. References ....................................................25
+      11.1. Normative References .....................................25
+      11.2. Informative References ...................................26
+
+
+
+
+
+Quittek, et al.               Informational                     [Page 2]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+1.  Introduction
+
+   With rising energy costs and an increasing awareness of the
+   ecological impact of running information technology equipment, Energy
+   Management (EMAN) functions and interfaces are becoming an additional
+   basic requirement for network management systems and devices
+   connected to a network.
+
+   This document defines requirements for standards specifications for
+   Energy Management, both monitoring functions and control functions.
+   Energy Management functions focus mainly on devices and their
+   components that receive and provide electrical energy.  Devices such
+   as hosts, routers, and middleboxes may have an IP address or may be
+   connected indirectly to the Internet via a proxy with an IP address
+   providing a management interface for the device, for example, devices
+   in a building infrastructure using non-IP protocols and a gateway to
+   the Internet.
+
+   These requirements are concerned with the standards specification
+   process and not the implementation of specified standards.  All
+   requirements in this document must be reflected by standards
+   specifications to be developed.  However, which of the features
+   specified by these standards will be mandatory, recommended, or
+   optional for compliant implementations is to be defined by Standards
+   Track document(s) and not in this document.
+
+   Section 3 elaborates on a set of general needs for Energy Management.
+   Requirements for an Energy Management standard are specified in
+   Sections 4 through 8.
+
+   Sections 4 through 6 contain conventional requirements specifying
+   information on entities and control functions.
+
+   Sections 7 and 8 contain requirements specific to Energy Management.
+   Due to the nature of power supply, some monitoring and control
+   functions are not conducted by interacting with the entity of
+   interest but rather with other entities, for example, entities
+   upstream in a power distribution tree.
+
+1.1.  Conventional Requirements for Energy Management
+
+   The specification of requirements for an Energy Management standard
+   starts with Section 4, which addresses the identification of entities
+   and the granularity of reporting of energy-related information.  A
+   standard must support the unique identification of entities,
+   reporting per entire device, and reporting energy-related information
+   on individual components of a device or attached devices.
+
+
+
+
+Quittek, et al.               Informational                     [Page 3]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Section 5 specifies requirements related to the monitoring of
+   entities.  This includes general (type, context) information and
+   specific information on Power States, Power Inlets, Power Outlets,
+   power, energy, and batteries.  The control of Power State and power
+   supply by entities is covered by requirements specified in Section 6.
+
+1.2.  Specific Requirements for Energy Management
+
+   While the conventional requirements summarized above seem to be all
+   that would be needed for Energy Management, there are significant
+   differences between Energy Management and most well-known network
+   management functions.  The most significant difference is the need
+   for some devices to report on other entities.  There are three major
+   reasons for this.
+
+   o  For monitoring a particular entity, it is not always sufficient to
+      communicate only with that entity.  When the entity has no
+      instrumentation for determining power, it might still be possible
+      to obtain power values for the entity via communication with other
+      entities in its power distribution tree.  A simple example of this
+      would be the retrieval of power values from a power meter at the
+      power line into the entity.  A Power Distribution Unit (PDU) and a
+      Power over Ethernet (PoE) switch are common examples.  Both supply
+      power to other entities at sockets or ports, respectively, and are
+      often instrumented to measure power per socket or port.
+
+   o  Similar considerations apply to controlling the power supply of an
+      entity that often needs direct or indirect communications with
+      another entity upstream in the power distribution tree.  Again, a
+      PDU and a PoE switch are common examples, if they have the
+      capability to switch power on or off at their sockets or ports,
+      respectively.
+
+   o  Energy Management often extends beyond entities with IP network
+      interfaces to non-IP building systems accessed via a gateway
+      (sometimes called an Energy Management System or controller).
+      Requirements in this document do not cover the details of these
+      networks and energy devices but specify means for opening IP
+      network management towards them.
+
+   These specific issues of Energy Management, as well as other issues,
+   are covered by requirements specified in Sections 7 and 8.
+
+   The requirements in these sections need a new Energy Management
+   framework that deals with the specific nature of Energy Management.
+   The actual standards documents, such as MIB module specifications,
+   address conformance by specifying which features must, should, or may
+   be implemented by compliant implementations.
+
+
+
+Quittek, et al.               Informational                     [Page 4]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+2.  Terminology
+
+   The terms specified in the terminology section are capitalized
+   throughout the document; the exceptions are the well-known terms
+   "energy" and "power".  These terms are generic and are used in
+   generated terms such as "energy-saving", "low-power", etc.
+
+   Energy
+
+      Energy is the capacity of a system to do work.  As used by
+      electric utilities, it is generally a reference to electrical
+      energy and is measured in kilowatt-hours (kWh) [IEEE-100].
+
+   Power
+
+      Power is the time rate at which energy is emitted, transferred, or
+      received; power is usually expressed in watts (or in joules per
+      second) [IEEE-100].  (The term "power" does not refer to the
+      concept of demand, which is an averaged power value.)
+
+   Power Attributes
+
+      Power Attributes are measurements of electric current, voltage,
+      phase, and frequencies at a given point in an electrical power
+      system (adapted from [IEC.60050]).
+
+      NOTE: Power Attributes are not intended to be "judgmental" with
+      respect to a reference or technical value and are independent of
+      any usage context.
+
+   Energy Management
+
+      Energy Management is a set of functions for measuring, modeling,
+      planning, and optimizing networks to ensure that the network
+      elements and attached devices use energy efficiently and in a
+      manner appropriate to the nature of the application and the cost
+      constraints of the organization [ITU-M.3400].
+
+   Energy Management System
+
+      An Energy Management System is a combination of hardware and
+      software used to administer a network with the primary purpose
+      being Energy Management.
+
+
+
+
+
+
+
+
+Quittek, et al.               Informational                     [Page 5]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Energy Monitoring
+
+      Energy Monitoring is a part of Energy Management that deals with
+      collecting or reading information from network elements and
+      attached devices and their components to aid in Energy Management.
+
+   Energy Control
+
+      Energy Control is a part of Energy Management that deals with
+      controlling energy supply and Power State of network elements, as
+      well as attached devices and their components.
+
+   Power Interface
+
+      A Power Interface is an interface at which a device is connected
+      to a power transmission medium, at which it can in turn receive
+      power, provide power, or both.
+
+   Power Inlet
+
+      A Power Inlet is a Power Interface at which a device can receive
+      power from other devices.
+
+   Power Outlet
+
+      A Power Outlet is a Power Interface at which a device can provide
+      power to other devices.
+
+   Power State
+
+      A Power State is a condition or mode of a device that broadly
+      characterizes its capabilities, power consumption, and
+      responsiveness to input [IEEE-1621].
+
+3.  General Considerations Related to Energy Management
+
+   The basic objective of Energy Management is to operate sets of
+   devices using minimal energy, while maintaining a certain level of
+   service.  [EMAN-STATEMENT] presents the applicability of the EMAN
+   framework to a variety of scenarios and also lists use cases and
+   target devices.
+
+
+
+
+
+
+
+
+
+
+Quittek, et al.               Informational                     [Page 6]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+3.1.  Power States
+
+   Entities can be set to an operational state that results in the
+   lowest power level that still meets the service-level performance
+   objectives.  In principle, there are three basic types of Power
+   States for an entity or for a whole system:
+
+   o  full Power State
+
+   o  sleep state (not functional but immediately available)
+
+   o  off state (may require significant time to become operational)
+
+   In specific devices, the number of Power States and their properties
+   vary considerably.  Simple entities may only have the extreme states:
+   full Power State and off state.  Many devices have three basic Power
+   States: on, off, and sleep.  However, more finely grained Power
+   States can be implemented.  Examples are various operational low
+   Power States in which a device requires less energy than in the full
+   power "on" state, but -- compared to the sleep state -- is still
+   operational with reduced performance or functionality.
+
+3.2.  Saving Energy versus Maintaining Service Level
+
+   One of the objectives of Energy Management is to reduce energy
+   consumption.  While this objective is clear, attaining that goal is
+   often difficult.  In many cases, there is no way to reduce power
+   without the consequence of a potential service (performance or
+   capacity) degradation.  In this case, a trade-off needs to be made
+   between service-level objectives and energy minimization.  In other
+   cases, a reduction of power can easily be achieved while still
+   maintaining sufficient service-level performance, for example, by
+   switching entities to lower Power States when higher performance is
+   not needed.
+
+3.3.  Local versus Network-Wide Energy Management
+
+   Many energy-saving functions are executed locally by an entity; it
+   monitors its usage and dynamically adapts its power according to the
+   required performance.  It may, for example, switch to a sleep state
+   when it is not in use, or outside of scheduled business hours.  An
+   Energy Management System may observe an entity's Power State and
+   configure its power-saving policies.
+
+   Energy savings can also be achieved with policies implemented by a
+   network management system that controls Power States of managed
+   entities.  Information about the power received and provided by
+
+
+
+
+Quittek, et al.               Informational                     [Page 7]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   entities in different Power States may be required in order to set
+   such policies.  Often, this information is best acquired through
+   monitoring.
+
+   Network-wide and local Energy Management methods both have advantages
+   and disadvantages, and it is often desirable to combine them.
+   Central management is often favorable for setting Power States of a
+   large number of entities at the same time, for example, at the
+   beginning and end of business hours in a building.  Local management
+   is often preferable for power-saving measures based on local
+   observations, such as the high or low functional load of an entity.
+
+3.4.  Energy Monitoring versus Energy Saving
+
+   Monitoring energy, power, and Power States alone does not reduce the
+   energy needed to run an entity.  In fact, it may even increase it
+   slightly due to monitoring instrumentation that needs energy.
+   Reporting measured quantities over the network may also increase
+   energy use, though the acquired information may be an essential input
+   to control loops that save energy.
+
+   Monitoring energy and Power States can also be required for other
+   purposes, including:
+
+   o  investigating energy-saving potential
+
+   o  evaluating the effectiveness of energy-saving policies and
+      measures
+
+   o  deriving, implementing, and testing power management strategies
+
+   o  accounting for the total power received and provided by an entity,
+      a network, or a service
+
+   o  predicting an entity's reliability based on power usage
+
+   o  choosing the time of the next maintenance cycle for an entity
+
+3.5.  Overview of Energy Management Requirements
+
+   The following basic management functions are required:
+
+   o  monitoring Power States
+
+   o  monitoring power (energy conversion rate)
+
+   o  monitoring (accumulated) received and provided energy
+
+
+
+
+Quittek, et al.               Informational                     [Page 8]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   o  monitoring Power Attributes
+
+   o  setting Power States
+
+   Power control is complementary to other energy-saving measures, such
+   as low-power electronics, energy-saving protocols, energy-efficient
+   device design (for example, low-power modes for components), and
+   energy-efficient network architectures.  Measurement of received and
+   provided energy can provide useful data for developing these
+   technologies.
+
+4.  Identification of Entities
+
+   Entities must be capable of being uniquely identified within the
+   context of the management system.  This includes entities that are
+   components of managed devices as well as entire devices.
+
+   Entities that report on or control other entities must identify the
+   entities they report on or control: see Section 7 or Section 8,
+   respectively, for the detailed requirements.
+
+   An entity may be an entire device or a component of it.  Examples of
+   components of interest are a hard drive, a battery, or a line card.
+   The ability to control individual components to save energy may be
+   required.  For example, server blades can be switched off when the
+   overall load is low, or line cards at switches may be powered down at
+   night.
+
+   Identifiers for devices and components are already defined in
+   standard MIB modules, such as the Link Layer Discovery Protocol
+   (LLDP) MIB module [IEEE-802.1AB] and the Link Layer Discovery
+   Protocol -- Media Endpoint Discovery (LLDP-MED) MIB module
+   [ANSI-TIA-1057] for devices, and the Entity MIB module [RFC6933] and
+   the power Ethernet MIB [RFC3621] for components of devices.  Energy
+   Management needs a means to link energy-related information to such
+   identifiers.
+
+   Instrumentation for measuring the received and provided energy of a
+   device is typically more expensive than instrumentation for
+   retrieving its Power State.  Many devices may provide Power State
+   information for all individual components separately, while reporting
+   the received and provided energy only for the entire device.
+
+4.1.  Identifying Entities
+
+   The standard must provide means for uniquely identifying entities.
+   Uniqueness must be preserved such that collisions of identities are
+   avoided at potential receivers of monitored information.
+
+
+
+Quittek, et al.               Informational                     [Page 9]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+4.2.  Persistence of Identifiers
+
+   The standard must provide means for indicating whether identifiers of
+   entities are persistent across a restart of the entity.
+
+4.3.  Change of Identifiers
+
+   The standard must provide means to indicate any change of entity
+   identifiers.
+
+4.4.  Using Entity Identifiers of Existing MIB Modules
+
+   The standard must provide means for reusing entity identifiers from
+   existing standards, including at least the following:
+
+   o  the entPhysicalIndex in the Entity MIB module [RFC6933]
+
+   o  the LldpPortNumber in the LLDP MIB module [IEEE-802.1AB] and in
+      the LLDP-MED MIB module [ANSI-TIA-1057]
+
+   o  the pethPsePortIndex and the pethPsePortGroupIndex in the Power
+      Ethernet MIB [RFC3621]
+
+   Generic means for reusing other entity identifiers must be provided.
+
+5.  Information on Entities
+
+   This section describes information on entities for which the standard
+   must provide means for retrieving and reporting.
+
+   Required information can be structured into seven groups.
+   Section 5.1 specifies requirements for general information on
+   entities, such as type of entity or context information.
+   Requirements for information on Power Inlets and Power Outlets of
+   entities are specified in Section 5.2.  The monitoring of power and
+   energy is covered by Sections 5.3 and 5.5, respectively.  Section 5.4
+   covers requirements related to entities' Power States.  Section 5.6
+   specifies requirements for monitoring batteries.  Finally, the
+   reporting of time series of values is covered by Section 5.7.
+
+5.1.  General Information on Entities
+
+   For Energy Management, understanding the role and context of an
+   entity may be required.  An Energy Management System may aggregate
+   values of received and provided energy according to a defined
+   grouping of entities.  When controlling and setting Power States, it
+   may be helpful to understand the grouping of the entity and role of
+
+
+
+
+Quittek, et al.               Informational                    [Page 10]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   an entity in a network.  For example, it may be important to exclude
+   some mission-critical network devices from being switched to lower
+   power or even from being switched off.
+
+5.1.1.  Type of Entity
+
+   The standard must provide means to configure, retrieve, and report a
+   textual name or a description of an entity.
+
+5.1.2.  Context of an Entity
+
+   The standard must provide means for retrieving and reporting context
+   information on entities, for example, tags associated with an entity
+   that indicate the entity's role.
+
+5.1.3.  Significance of Entities
+
+   The standard must provide means for retrieving and reporting the
+   significance of entities within its context, for example, how
+   important the entity is.
+
+5.1.4.  Power Priority
+
+   The standard must provide means for retrieving and reporting power
+   priorities of entities.  Power priorities indicate an order in which
+   Power States of entities are changed, for example, to lower Power
+   States for saving power.
+
+5.1.5.  Grouping of Entities
+
+   The standard must provide means for grouping entities.  This can be
+   achieved in multiple ways, for example, by providing means to tag
+   entities, assign them to domains, or assign device types to them.
+
+5.2.  Power Interfaces
+
+   A Power Interface is an interface at which a device is connected to a
+   power transmission medium, at which it can in turn receive power,
+   provide power, or both.
+
+   A Power Interface is either an inlet or an outlet.  Some Power
+   Interfaces change over time from being an inlet to being an outlet
+   and vice versa.  However, most Power Interfaces never change.
+
+   Devices have Power Inlets at which they are supplied with electric
+   power.  Most devices have a single Power Inlet, while some have
+   multiple inlets.  Different Power Inlets on a device are often
+   connected to separate power distribution trees.  For Energy
+
+
+
+Quittek, et al.               Informational                    [Page 11]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Monitoring, it is useful to retrieve information on the number of
+   inlets of a device, the availability of power at inlets, and which
+   inlets are actually in use.
+
+   Devices can have one or more Power Outlets for supplying other
+   devices with electric power.
+
+   For identifying and potentially controlling the source of power
+   received at an inlet, identifying the Power Outlet of another device
+   at which the received power is provided may be required.
+   Analogously, for each outlet, it is of interest to identify the Power
+   Inlets that receive the power provided at a certain outlet.  Such
+   information is also required for constructing the wiring topology of
+   electrical power distribution to devices.
+
+   Static properties of each Power Interface are required information
+   for Energy Management.  Static properties include the kind of
+   electric current (AC or DC), the nominal voltage, the nominal AC
+   frequency, and the number of AC phases.  Note that the nominal
+   voltage is often not a single value but a voltage range, such as, for
+   example, (100V-120V), (100V-240V), (100V-120V,220V-240V).
+
+5.2.1.  List of Power Interfaces
+
+   The standard must provide means for monitoring the list of Power
+   Interfaces of a device.
+
+5.2.2.  Operational Mode of Power Interfaces
+
+   The standard must provide means for monitoring the operational mode
+   of a Power Interface, which is either "Power Inlet" or "Power
+   Outlet".
+
+5.2.3.  Corresponding Power Outlet
+
+   The standard must provide means for identifying the Power Outlet that
+   provides the power received at a Power Inlet.
+
+5.2.4.  Corresponding Power Inlets
+
+   The standard must provide means for identifying the list of Power
+   Inlets that receive the power provided at a Power Outlet.
+
+
+
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 12]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+5.2.5.  Availability of Power
+
+   If the Power States allow it, the standard must provide means for
+   monitoring the availability of power at each Power Interface.  This
+   includes indicating whether a power supply at a Power Interface is
+   switched on or off.
+
+5.2.6.  Use of Power
+
+   The standard must provide means for monitoring each Power Interface
+   if it is actually in use.  For inlets, this means that the device
+   actually receives power at the inlet.  For outlets, this means that
+   power is actually provided from the outlet to one or more devices.
+
+5.2.7.  Type of Current
+
+   The standard must provide means for reporting the type of current (AC
+   or DC) for each Power Interface as well as for a device.
+
+5.2.8.  Nominal Voltage Range
+
+   The standard must provide means for reporting the nominal voltage
+   range for each Power Interface.
+
+5.2.9.  Nominal AC Frequency
+
+   The standard must provide means for reporting the nominal AC
+   frequency for each Power Interface.
+
+5.2.10.  Number of AC Phases
+
+   The standard must provide means for reporting the number of AC phases
+   for each Power Interface.
+
+5.3.  Power
+
+   Power is measured as an instantaneous value or as the average over a
+   time interval.
+
+   Obtaining highly accurate values for power and energy may be costly
+   if dedicated metering hardware is required.  Entities without the
+   ability to measure with high accuracy their power, received energy,
+   and provided energy may just report estimated values, for example,
+   based on load monitoring, Power State, or even just the entity type.
+
+   Depending on how power and energy values are obtained, the confidence
+   in a reported value and its accuracy will vary.  Entities reporting
+   such values should qualify the confidence in the reported values and
+
+
+
+Quittek, et al.               Informational                    [Page 13]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   quantify the accuracy of measurements.  For reporting accuracy, the
+   accuracy classes specified in IEC 62053-21 [IEC.62053-21] and
+   IEC 62053-22 [IEC.62053-22] should be considered.
+
+   Further properties of the power supplied to a device are also of
+   interest.  For AC power supply in particular, several Power
+   Attributes beyond the real power are of potential interest to Energy
+   Management Systems.  The set of these properties includes the complex
+   Power Attributes (apparent power, reactive power, and phase angle of
+   the current or power factor) as well as the actual voltage, the
+   actual AC frequency, the Total Harmonic Distortion (THD) of voltage
+   and current, and the impedance of an AC phase or of the DC supply.  A
+   new standard for monitoring these Power Attributes should be in line
+   with already-existing standards, such as [IEC.61850-7-4].
+
+   For some network management tasks, it is desirable to receive
+   notifications from entities when their power value exceeds or falls
+   below given thresholds.
+
+5.3.1.  Real Power / Power Factor
+
+   The standard must provide means for reporting the real power for each
+   Power Interface as well as for an entity.  Reporting power includes
+   reporting the direction of power flow.
+
+5.3.2.  Power Measurement Interval
+
+   The standard must provide means for reporting the corresponding time
+   or time interval for which a power value is reported.  The power
+   value can be measured at the corresponding time or averaged over the
+   corresponding time interval.
+
+5.3.3.  Power Measurement Method
+
+   The standard must provide means to indicate the method used to obtain
+   these values.  Based on how the measurement was conducted, it is
+   possible to associate a certain degree of confidence with the
+   reported power value.  For example, there are methods of measurement
+   such as direct power measurement, estimation based on performance
+   values, or hard-coding average power values for an entity.
+
+5.3.4.  Accuracy of Power and Energy Values
+
+   The standard must provide means for reporting the accuracy of
+   reported power and energy values.
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 14]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+5.3.5.  Actual Voltage and Current
+
+   The standard must provide means for reporting the actual voltage and
+   actual current for each Power Interface as well as for a device.  For
+   AC power supply, means must be provided for reporting the actual
+   voltage and actual current per phase.
+
+5.3.6.  High-Power/Low-Power Notifications
+
+   The standard must provide means for creating notifications if power
+   values of an entity rise above or fall below given thresholds.
+
+5.3.7.  Complex Power / Power Factor
+
+   The standard must provide means for reporting the complex power for
+   each Power Interface and for each phase at a Power Interface.  In
+   addition to the real power, at least two of the following three
+   quantities need to be reported: apparent power, reactive power, and
+   phase angle.  The phase angle can be substituted by the power factor.
+
+5.3.8.  Actual AC Frequency
+
+   The standard must provide means for reporting the actual AC frequency
+   for each Power Interface.
+
+5.3.9.  Total Harmonic Distortion
+
+   The standard must provide means for reporting the Total Harmonic
+   Distortion (THD) of voltage and current for each Power Interface.
+   For AC power supply, means must be provided for reporting the THD per
+   phase.
+
+5.3.10.  Power Supply Impedance
+
+   The standard must provide means for reporting the impedance of a
+   power supply for each Power Interface.  For AC power supply, means
+   must be provided for reporting the impedance per phase.
+
+5.4.  Power State
+
+   Many entities have a limited number of discrete Power States.
+
+   There is a need to report the actual Power State of an entity and to
+   provide the means for retrieving the list of all supported Power
+   States.
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 15]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Different standards bodies have already defined sets of Power States
+   for some entities, and others are creating new Power State sets.  In
+   this context, it is desirable that the standard support many of these
+   Power State standards.  In order to support multiple management
+   systems that possibly use different Power State sets while
+   simultaneously interfacing with a particular entity, the Energy
+   Management System must provide means for supporting multiple Power
+   State sets used simultaneously at an entity.
+
+   Power States have parameters that describe their properties.  It is
+   required to have a standardized means for reporting some key
+   properties, such as the typical power of an entity in a certain
+   state.
+
+   There is also a need to report statistics on Power States, including
+   the time spent as well as the received and provided energy in a Power
+   State.
+
+5.4.1.  Actual Power State
+
+   The standard must provide means for reporting the actual Power State
+   of an entity.
+
+5.4.2.  List of Supported Power States
+
+   The standard must provide means for retrieving the list of all
+   potential Power States of an entity.
+
+5.4.3.  Multiple Power State Sets
+
+   The standard must provide means for supporting multiple Power State
+   sets simultaneously at an entity.
+
+5.4.4.  List of Supported Power State Sets
+
+   The standard must provide means for retrieving the list of all Power
+   State sets supported by an entity.
+
+5.4.5.  List of Supported Power States within a Set
+
+   The standard must provide means for retrieving the list of all
+   potential Power States of an entity for each supported Power State
+   set.
+
+5.4.6.  Typical Power Per Power State
+
+   The standard must provide means for retrieving the typical power for
+   each supported Power State.
+
+
+
+Quittek, et al.               Informational                    [Page 16]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+5.4.7.  Power State Statistics
+
+   The standard must provide means for monitoring statistics per Power
+   State, including the total time spent in a Power State, the number of
+   times each state was entered, and the last time each state was
+   entered.  More Power State statistics are addressed by the
+   requirements in Section 5.5.3.
+
+5.4.8.  Power State Changes
+
+   The standard must provide means for generating a notification when
+   the actual Power State of an entity changes.
+
+5.5.  Energy
+
+   The monitoring of electrical energy received or provided by an entity
+   is a core function of Energy Management.  Since energy is an
+   accumulated quantity, it is always reported for a certain interval of
+   time.  This can be, for example, the time from the last restart of
+   the entity to the reporting time, the time from another past event to
+   the reporting time, the last given amount of time before the
+   reporting time, or a certain interval specified by two timestamps in
+   the past.
+
+   It is useful for entities to record their received and provided
+   energy per Power State and report these quantities.
+
+5.5.1.  Energy Measurement
+
+   The standard must provide means for reporting measured values of
+   energy and the direction of the energy flow received or provided by
+   an entity.  The standard must also provide the means to report the
+   energy passing through each Power Interface.
+
+5.5.2.  Time Intervals
+
+   The standard must provide means for reporting the time interval for
+   which an energy value is reported.
+
+5.5.3.  Energy Per Power State
+
+   The standard must provide means for reporting the received and
+   provided energy for each individual Power State.  This extends the
+   requirements on Power State statistics described in Section 5.4.7.
+
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 17]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+5.6.  Battery State
+
+   Batteries are special entities that supply power.  The status of
+   these batteries is typically controlled by automatic functions that
+   act locally on the entity, and manually by users of the entity.
+   There is a need to monitor the battery status of these entities by
+   network management systems.
+
+   Devices containing batteries can be modeled in two ways.  The entire
+   device can be modeled as a single entity on which energy-related
+   information is reported, or the battery can be modeled as an
+   individual entity for which energy-related information is monitored
+   individually according to requirements in Sections 5.1 through 5.5.
+
+   Further information on batteries is of interest for Energy
+   Management, such as the current charge of the battery, the number of
+   completed charging cycles, the charging state of the battery, its
+   temperature, and additional static and dynamic battery properties.
+   It is desirable to receive notifications if the charge of a battery
+   becomes very low or if a battery needs to be replaced.
+
+5.6.1.  Battery Charge
+
+   The standard must provide means for reporting the current charge of a
+   battery, in units of milliampere-hours (mAh).
+
+5.6.2.  Battery Charging State
+
+   The standard must provide means for reporting the charging state
+   (charging, discharging, etc.) of a battery.
+
+5.6.3.  Battery Charging Cycles
+
+   The standard must provide means for reporting the number of completed
+   charging cycles of a battery.
+
+5.6.4.  Actual Battery Capacity
+
+   The standard must provide means for reporting the actual capacity of
+   a battery.
+
+5.6.5.  Actual Battery Temperature
+
+   The standard must provide means for reporting the actual temperature
+   of a battery.
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 18]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+5.6.6.  Static Battery Properties
+
+   The standard must provide means for reporting static properties of a
+   battery, including the nominal capacity, the number of cells, the
+   nominal voltage, and the battery technology.
+
+5.6.7.  Low Battery Charge Notification
+
+   The standard must provide means for generating a notification when
+   the charge of a battery decreases below a given threshold.  Note that
+   the threshold may depend on the battery technology.
+
+5.6.8.  Battery Replacement Notification
+
+   The standard must provide means for generating a notification when
+   the number of charging cycles of a battery exceeds a given threshold.
+
+5.6.9.  Multiple Batteries
+
+   If the battery technology allows, the standard must provide means for
+   meeting requirements in Sections 5.6.1 through 5.6.8 for each
+   individual battery contained in a single entity.
+
+5.7.  Time Series of Measured Values
+
+   For some network management tasks, obtaining time series of measured
+   values from entities, such as power, energy, battery charge, etc., is
+   required.
+
+   In general, time series measurements could be obtained in many
+   different ways.  Means should be provided to either push such values
+   from the location where they are available to the management system
+   or to have them stored locally for a sufficiently long period of time
+   such that a management system can retrieve the full time series.
+
+   The following issues are to be considered when designing time series
+   measurement and reporting functions:
+
+   1.  Which quantities should be reported?
+
+   2.  Which time interval type should be used (total, delta, sliding
+       window)?
+
+   3.  Which measurement method should be used (sampled, continuous)?
+
+   4.  Which reporting model should be used (push or pull)?
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 19]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   The most discussed and probably most needed quantity is energy.  But
+   a need for others, such as power and battery charge, can be
+   identified as well.
+
+   There are three time interval types under discussion for accumulated
+   quantities such as energy.  They can be reported as total values,
+   accumulated between the last restart of the measurement and a certain
+   timestamp.  Alternatively, energy can be reported as delta values
+   between two consecutive timestamps.  Another alternative is reporting
+   values for sliding windows as specified in [IEC.61850-7-4].
+
+   For non-accumulative quantities, such as power, different measurement
+   methods are considered.  Such quantities can be reported using values
+   sampled at certain timestamps or, alternatively, by mean values for
+   these quantities averaged between two (consecutive) timestamps or
+   over a sliding window.
+
+   Finally, time series can be reported using different reporting
+   models, particularly push-based or pull-based.  Push-based reporting
+   can, for example, be realized by reporting power or energy values
+   using the IP Flow Information Export (IPFIX) protocol [RFC7011]
+   [RFC7012].  The Simple Network Management Protocol (SNMP) [RFC3411]
+   is an example of a protocol that can be used for realizing pull-based
+   reporting of time series.
+
+   For reporting time series of measured values, the following
+   requirements have been identified.  Further decisions concerning
+   issues discussed above need to be made when developing concrete
+   Energy Management standards.
+
+5.7.1.  Time Series of Energy Values
+
+   The standard must provide means for reporting time series of energy
+   values.  If the comparison of time series between multiple entities
+   is required, then time synchronization between those entities must be
+   provided (for example, with the Network Time Protocol [RFC5905]).
+
+5.7.2.  Time Series Interval Types
+
+   The standard must provide means for supporting alternative interval
+   types.  The requirement in Section 5.5.2 applies to every reported
+   time value.
+
+5.7.3.  Time Series Storage Capacity
+
+   The standard should provide means for reporting the number of values
+   of a time series that can be stored for later reporting.
+
+
+
+
+Quittek, et al.               Informational                    [Page 20]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+6.  Control of Entities
+
+   Many entities control their Power State locally.  Other entities need
+   interfaces for an Energy Management System to control their Power
+   State.
+
+   A power supply is typically not self-managed by devices, and control
+   of a power supply is typically not conducted as an interaction
+   between an Energy Management System and the device itself.  It is
+   rather an interaction between the management system and a device
+   providing power at its Power Outlets.  Similar to Power State
+   control, power supply control may be policy driven.  Note that
+   shutting down the power supply abruptly may have severe consequences
+   for the device.
+
+6.1.  Controlling Power States
+
+   The standard must provide means for setting Power States of entities.
+
+6.2.  Controlling Power Supply
+
+   The standard must provide means for switching a power supply off or
+   turning a power supply on at Power Interfaces providing power to one
+   or more devices.
+
+7.  Reporting on Other Entities
+
+   As discussed in Section 5, not all energy-related information may be
+   available at the entity in question.  Such information may be
+   provided by other entities.  This section covers only the reporting
+   of information.  See Section 8 for requirements on controlling other
+   entities.
+
+   There are cases where a power supply unit switches power for several
+   entities by turning power on or off at a single Power Outlet or where
+   a power meter measures the accumulated power of several entities at a
+   single power line.  Consequently, it should be possible to report
+   that a monitored value does not relate to just a single entity but is
+   an accumulated value for a set of entities.  All of the entities
+   belonging to that set need to be identified.
+
+7.1.  Reports on Other Entities
+
+   The standard must provide means for an entity to report information
+   on another entity.
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 21]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+7.2.  Identity of Other Entities on Which Information Is Reported
+
+   For entities that report on one or more other entities, the standard
+   must provide means for reporting the identity of other entities on
+   which information is reported.  Note that, in some situations, a
+   manual configuration might be required to populate this information.
+
+7.3.  Reporting Quantities Accumulated over Multiple Entities
+
+   The standard must provide means for reporting the list of all
+   entities from which contributions are included in an accumulated
+   value.
+
+7.4.  List of All Entities on Which Information Is Reported
+
+   For entities that report on one or more other entities, the standard
+   must provide means for reporting the complete list of all those
+   entities on which energy-related information can be reported.
+
+7.5.  Content of Reports on Other Entities
+
+   For entities that report on one or more other entities, the standard
+   must provide means for indicating what type or types of energy-
+   related information can be reported, and for which entities.
+
+8.  Controlling Other Entities
+
+   This section specifies requirements for controlling Power States and
+   power supply of entities by communicating with other entities that
+   have the means for doing that control.
+
+8.1.  Controlling Power States of Other Entities
+
+   Some entities have control over Power States of other entities.  For
+   example, a gateway to a building system may have the means to control
+   the Power State of entities in the building that do not have an IP
+   interface.  For this scenario and other similar cases, a way to make
+   this control accessible to the Energy Management System is needed.
+
+   In addition, it is required that an entity that has its state
+   controlled by other entities has the means to report the list of
+   these other entities.
+
+
+
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 22]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+8.1.1.  Control of Power States of Other Entities
+
+   The standard must provide means for an Energy Management System to
+   send Power State control commands to an entity that controls the
+   Power States of entities other than the entity to which the command
+   was sent.
+
+8.1.2.  Identity of Other Power State Controlled Entities
+
+   The standard must provide means for reporting the identities of the
+   entities for which the reporting entity has the means to control
+   their Power States.  Note that, in some situations, a manual
+   configuration might be required to populate this information.
+
+8.1.3.  List of All Power State Controlled Entities
+
+   The standard must provide means for an entity to report the list of
+   all entities for which it can control the Power State.
+
+8.1.4.  List of All Power State Controllers
+
+   The standard must provide means for an entity that receives commands
+   controlling its Power State from other entities to report the list of
+   all those entities.
+
+8.2.  Controlling Power Supply
+
+   Some entities may have control of the power supply of other entities,
+   for example, because the other entity is supplied via a Power Outlet
+   of the entity.  For this and similar cases, means are needed to make
+   this control accessible to the Energy Management System.  This need
+   is already addressed by the requirement in Section 6.2.
+
+   In addition, it is required that an entity that has its supply
+   controlled by other entities has the means to report the list of
+   these other entities.  This need is already addressed by requirements
+   in Sections 5.2.3 and 5.2.4.
+
+9.  Security Considerations
+
+   Controlling Power State and power supply of entities are considered
+   highly sensitive actions, since they can significantly affect the
+   operation of directly and indirectly connected devices.  Therefore,
+   all control actions addressed in Sections 6 and 8 must be
+   sufficiently protected through authentication, authorization, and
+   integrity protection mechanisms.
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 23]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Entities that are not sufficiently secure to operate directly on the
+   public Internet do exist and can be a significant cause of risk, for
+   example, if the remote control functions described in Sections 6 and
+   8 can be exercised on those devices from anywhere on the Internet.
+   The standard needs to provide means for dealing with such cases.  One
+   solution is providing means that allow the isolation of such devices,
+   e.g., behind a sufficiently secured gateway.  Another solution is to
+   allow compliant implementations to disable sensitive functions, or to
+   not implement such functions at all.
+
+   The monitoring of energy-related quantities of an entity as addressed
+   in Sections 5 through 8 can be used to derive more information than
+   just the received and provided energy; therefore, monitored data
+   requires protection.  This protection includes authentication and
+   authorization of entities requesting access to monitored data as well
+   as confidentiality protection during transmission of monitored data.
+   Privacy of stored data in an entity must be taken into account.
+   Monitored data may be used as input to control, accounting, and other
+   actions, so integrity of transmitted information and authentication
+   of the origin may be needed.
+
+9.1.  Secure Energy Management
+
+   The standard must provide privacy, integrity, and authentication
+   mechanisms for all actions addressed in Sections 5 through 8.  The
+   security mechanisms must meet the security requirements detailed in
+   Section 1.4 of [RFC3411].
+
+9.2.  Isolation of Insufficiently Secure Entities
+
+   The standard must provide means to allow the isolation of entities
+   that are not sufficiently secure to operate on the public Internet,
+   e.g., behind a gateway that implements sufficient security that the
+   vulnerable entities are not directly exposed to the Internet.
+
+9.3.  Optional Restriction of Functions
+
+   The standard must allow compliant implementations to disable
+   sensitive functions, or to not implement such functions at all, when
+   operating in environments that are not sufficiently secured.  This
+   applies particularly to the control functions described in Sections 6
+   and 8.
+
+
+
+
+
+
+
+
+
+Quittek, et al.               Informational                    [Page 24]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+10.  Acknowledgments
+
+   The authors would like to thank Ralf Wolter for his first essay on
+   this document.  Many thanks to William Mielke, John Parello,
+   JinHyeock Choi, Georgios Karagiannis, and Michael Suchoff for their
+   helpful comments on the document.  Many thanks to Stephen Farrell,
+   Robert Sparks, Adrian Farrel, Barry Leiba, Brian Haberman, Peter
+   Resnick, Sean Turner, Stewart Bryant, and Ralph Droms for their IESG
+   reviews.  Finally, special thanks to the document shepherd, Nevil
+   Brownlee, and to the EMAN working group chairs: Nevil Brownlee and
+   Bruce Nordman.
+
+11.  References
+
+11.1.  Normative References
+
+   [ANSI-TIA-1057]
+              Telecommunications Industry Association, ANSI-
+              TIA-1057-2006, "TIA Standard -- Telecommunications -- IP
+              Telephony Infrastructure -- Link Layer Discovery Protocol
+              for Media Endpoint Devices", April 2006.
+
+   [IEC.61850-7-4]
+              International Electrotechnical Commission, "Communication
+              networks and systems for power utility automation --
+              Part 7-4: Basic communication structure -- Compatible
+              logical node classes and data object classes", March 2010.
+
+   [IEC.62053-21]
+              International Electrotechnical Commission, "Electricity
+              metering equipment (a.c.) -- Particular requirements --
+              Part 21: Static meters for active energy (classes 1
+              and 2)", January 2003.
+
+   [IEC.62053-22]
+              International Electrotechnical Commission, "Electricity
+              metering equipment (a.c.) -- Particular requirements --
+              Part 22: Static meters for active energy (classes 0,2 S
+              and 0,5 S)", January 2003.
+
+   [IEEE-100] IEEE, "The Authoritative Dictionary of IEEE Standards
+              Terms, IEEE 100, Seventh Edition", December 2000.
+
+   [IEEE-1621]
+              Institute of Electrical and Electronics Engineers,
+              "IEEE 1621-2004 - IEEE Standard for User Interface
+              Elements in Power Control of Electronic Devices Employed
+              in Office/Consumer Environments", 2004.
+
+
+
+Quittek, et al.               Informational                    [Page 25]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   [IEEE-802.1AB]
+              IEEE Computer Society, "IEEE Std 802.1AB-2009 -- IEEE
+              Standard for Local and Metropolitan Area Networks --
+              Station and Media Access Control Discovery",
+              September 2009.
+
+   [RFC3411]  Harrington, D., Presuhn, R., and B. Wijnen, "An
+              Architecture for Describing Simple Network Management
+              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
+              December 2002.
+
+   [RFC3621]  Berger, A. and D. Romascanu, "Power Ethernet MIB",
+              RFC 3621, December 2003.
+
+   [RFC6933]  Bierman, A., Romascanu, D., Quittek, J., and M.
+              Chandramouli, "Entity MIB (Version 4)", RFC 6933,
+              May 2013.
+
+11.2.  Informative References
+
+   [EMAN-STATEMENT]
+              Schoening, B., Chandramouli, M., and B. Nordman, "Energy
+              Management (EMAN) Applicability Statement", Work in
+              Progress, April 2013.
+
+   [IEC.60050]
+              International Electrotechnical Commission, "Electropedia:
+              The World's Online Electrotechnical Vocabulary", 2013,
+              <http://www.electropedia.org/iev/iev.nsf/
+              welcome?openform>.
+
+   [ITU-M.3400]
+              International Telecommunication Union, "ITU-T
+              Recommendation M.3400 -- Series M: TMN and Network
+              Maintenance: International Transmission Systems, Telephone
+              Circuits, Telegraphy, Facsimile and Leased Circuits --
+              Telecommunications Management Network - TMN management
+              functions", February 2000.
+
+   [RFC7011]  Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
+              "Specification of the IP Flow Information Export (IPFIX)
+              Protocol for the Exchange of Flow Information", STD 77,
+              RFC 7011, September 2013.
+
+   [RFC7012]  Claise, B., Ed., and B. Trammell, Ed., "Information Model
+              for IP Flow Information Export (IPFIX)", RFC 7012,
+              September 2013.
+
+
+
+
+Quittek, et al.               Informational                    [Page 26]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
+              Time Protocol Version 4: Protocol and Algorithms
+              Specification", RFC 5905, June 2010.
+
+Authors' Addresses
+
+   Juergen Quittek (editor)
+   NEC Europe Ltd.
+   NEC Laboratories Europe
+   Network Research Division
+   Kurfuersten-Anlage 36
+   Heidelberg  69115
+   Germany
+
+   Phone: +49 6221 4342-115
+   EMail: quittek@neclab.eu
+
+
+   Mouli Chandramouli
+   Cisco Systems, Inc.
+   Sarjapur Outer Ring Road
+   Bangalore
+   India
+
+   Phone: +91 80 4426 3947
+   EMail: moulchan@cisco.com
+
+
+   Rolf Winter
+   NEC Europe Ltd.
+   NEC Laboratories Europe
+   Network Research Division
+   Kurfuersten-Anlage 36
+   Heidelberg  69115
+   Germany
+
+   Phone: +49 6221 4342-121
+   EMail: Rolf.Winter@neclab.eu
+
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+Quittek, et al.               Informational                    [Page 27]
+
+RFC 6988           Requirements for Energy Management     September 2013
+
+
+   Thomas Dietz
+   NEC Europe Ltd.
+   NEC Laboratories Europe
+   Network Research Division
+   Kurfuersten-Anlage 36
+   Heidelberg  69115
+   Germany
+
+   Phone: +49 6221 4342-128
+   EMail: Thomas.Dietz@neclab.eu
+
+
+   Benoit Claise
+   Cisco Systems, Inc.
+   De Kleetlaan 6a b1
+   Diegem  1831
+   Belgium
+
+   Phone: +32 2 704 5622
+   EMail: bclaise@cisco.com
+
+
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+Quittek, et al.               Informational                    [Page 28]
+