Internet Engineering Task Force (IETF)
Request for Comments: 7326
Category: Informational
ISSN: 2070-1721

J. Parello
B. Claise
Cisco Systems, Inc.
B. Schoening
Independent Consultant
J. Quittek
NEC Europe Ltd.
September 2014

Energy Management Framework

Abstract

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.

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/rfc7326.

Copyright Notice

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.

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Target Devices ..................................................9
   4. Physical Reference Model .......................................10
   5. Areas Not Covered by the Framework .............................11
   6. Energy Management Abstraction ..................................12
      6.1. Conceptual Model ..........................................12
      6.2. Energy Object (Class) .....................................13
      6.3. Energy Object Attributes ..................................15
      6.4. Measurements ..............................................18
      6.5. Control ...................................................19
      6.6. Relationships .............................................25
   7. Energy Management Information Model ............................29
   8. Modeling Relationships between Devices .........................33
      8.1. Power Source Relationship .................................33
      8.2. Metering Relationship .....................................37
      8.3. Aggregation Relationship ..................................38
   9. Relationship to Other Standards ................................39
   10. Security Considerations .......................................39
      10.1. Security Considerations for SNMP .........................40
   11. IANA Considerations ...........................................41
      11.1. IANA Registration of New Power State Sets ................41
      11.2. Updating the Registration of Existing Power State Sets ...42
   12. References ....................................................43
      12.1. Normative References .....................................43
      12.2. Informative References ...................................44
   13. Acknowledgments ...............................................45
   Appendix A. Information Model Listing .............................46

1. Introduction

Network Management is often divided into the five main areas defined in the ISO Telecommunications Management Network model: Fault, Configuration, Accounting, Performance, and Security Management (FCAPS) [X.700]. Not covered by this traditional management model is Energy Management, which is rapidly becoming a critical area of concern worldwide, as seen in [ISO50001].

This document defines an Energy Management framework for devices within, or connected to, communication networks, per the Energy Management requirements specified in [RFC6988]. The devices, or the components of these devices (such as line cards, fans, and disks), can then be monitored and controlled. Monitoring includes measuring power, energy, demand, and attributes of power. Energy Control can be performed by setting a device's or component's state. The devices monitored by this framework can be either of the following:

consumers of energy (such as routers and computer systems) and components of such devices (such as line cards, fans, and disks)

producers of energy (like an uninterruptible power supply or renewable energy system) and their associated components (such as battery cells, inverters, or photovoltaic panels)

This framework further describes how to identify, classify, and provide context for such devices. While context information is not specific to Energy Management, some context attributes are specified in the framework, addressing the following use cases:

How important is a device in terms of its business impact?

How should devices be grouped for reporting and searching?

How should a device role be described?

Guidelines for using context for Energy Management are described.

The framework introduces the concept of a Power Interface that is analogous to a network interface. A Power Interface is defined as an interconnection among devices where energy can be provided, received, or both.

The most basic example of Energy Management is a single device reporting information about itself. In many cases, however, energy is not measured by the device itself but is measured upstream in the power distribution tree. For example, a Power Distribution Unit (PDU) may measure the energy it supplies to attached devices and report this to an Energy Management System. Therefore, devices often have relationships to other devices or components in the power network. An Energy Management System (EnMS) generally requires an understanding of the power topology (who provides power to whom), the Metering topology (who meters whom), and the potential Aggregation (who aggregates values of others).

The relationships build on the Power Interface concept. The different relationships among devices and components, as specified in this document, include power source, Metering, and Aggregation Relationships.

The framework does not cover non-electrical equipment, nor does it cover energy procurement and manufacturing.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].

In this document, these words will appear with the above interpretation only when in ALL CAPS. Lowercase uses of these words are not to be interpreted as carrying the significance of RFC 2119 key words.

In this section, some terms have a NOTE that is not part of the definition itself but accounts for differences between terminologies of different standards organizations or further clarifies the definition.

The terms are listed in an order that aids in reading where terms may build off a previous term, as opposed to an alphabetical ordering. Some terms that are common in electrical engineering or that describe common physical items use a lowercase notation.

Energy Management

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.

Reference:

Adapted from [TMN].

NOTES:

"Energy Management" refers to the activities, methods, procedures, and tools that pertain to measuring, modeling, planning, controlling, and optimizing the use of energy in networked systems [NMF].

Energy Management is a management domain that is congruent to any of the FCAPS areas of management in the ISO/OSI Network Management Model [TMN]. Energy Management for communication networks and attached devices is a subset or part of an organization's greater Energy Management Policies.

Energy Management System (EnMS)

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

NOTES:

      1. An Energy Management System according to [ISO50001] (ISO-EnMS)
      
         is a set of systems or procedures upon which organizations can
         develop and implement an energy policy, set targets and action
         plans, and take into account legal requirements related to
         energy use.  An ISO-EnMS allows organizations to improve energy
         performance and demonstrate conformity to requirements,
         standards, and/or legal requirements.

Example ISO-EnMS: Company A defines a set of policies and procedures indicating that there should exist multiple computerized systems that will poll energy measurements from their meters and pricing / source data from their local utility. Company A specifies that their CFO (Chief Financial Officer) should collect information and summarize it quarterly to be sent to an accounting firm to produce carbon accounting reporting as required by their local government.

For the purposes of EMAN, the definition herein is the preferred meaning of an EnMS. The definition from [ISO50001] can be referred to as an ISO Energy Management System (ISO-EnMS).

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

Energy Control: Energy Control is a part of Energy Management that deals with directing influence over devices.

electrical equipment

This is a general term that includes materials, fittings, devices, appliances, fixtures, apparatus, machines, etc., that are used as a part of, or in connection with, an electric installation.

Reference:

[IEEE100].

non-electrical equipment (mechanical equipment)

This is a general term that includes materials, fittings, devices, appliances, fixtures, apparatus, machines, etc., that are used as a part of, or in connection with, non-electrical power installations.

Reference:

Adapted from [IEEE100].

device

A device is a piece of electrical or non-electrical equipment.

Reference:

Adapted from [IEEE100].

component

A component is a part of electrical or non-electrical equipment (device).

Reference:

Adapted from [TMN].

power inlet: A power inlet (or simply "inlet") is an interface at which a device or component receives energy from another device or component.

power outlet: A power outlet (or simply "outlet") is an interface at which a device or component provides energy to another device or component.

energy

Energy is that which does work or is capable of doing work. As used by electric utilities, it is generally a reference to electrical energy and is measured in kilowatt-hours (kWh).

Reference:

[IEEE100].

NOTE:

Energy is the capacity of a system to produce external activity or perform work [ISO50001].

power

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

Reference:

[IEEE100].

demand

Demand is the average value of power or a related quantity over a specified interval of time. Note: Demand is expressed in kilowatts, kilovolt-amperes, kilovars, or other suitable units.

Reference:

[IEEE100].

NOTE:

While IEEE100 defines demand in kilo measurements, for EMAN we use watts with any suitable metric prefix.

provide energy: A device (or component) "provides" energy to another device if there is an energy flow from this device to the other one.

receive energy: A device (or component) "receives" energy from another device if there is an energy flow from the other device to this one.

meter (energy meter)

A meter is a device intended to measure electrical energy by integrating power with respect to time.

Reference:

Adapted from [IEC60050].

battery

A battery is one or more cells (consisting of an assembly of electrodes, electrolyte, container, terminals, and (usually) separators) that are a source and/or store of electric energy.

Reference:

Adapted from [IEC60050].

Power Interface: A Power Interface is a power inlet, outlet, or both.

Nameplate Power: The Nameplate Power is the nominal power of a device as specified by the device manufacturer.

Power Attributes

Power Attributes are measurements of the electrical current, voltage, phase, and frequencies at a given point in an electrical power system.

Reference:

Adapted from [IEC60050].

NOTE:

Power Attributes are not intended to provide any bounds or recommended range for the value. They are simply the reading of the value associated with the attribute in question.

Power Quality

"Power Quality" refers to characteristics of the electrical current, voltage, phase, and frequencies at a given point in an electric power system, evaluated against a set of reference technical parameters. These parameters might, in some cases, relate to the compatibility between electricity supplied in an electric power system and the loads connected to that electric power system.

Reference:

[IEC60050].

NOTE:

Electrical characteristics representing Power Quality information are typically required by customer facility Energy Management Systems. Electrical characteristics are not intended to satisfy the detailed requirements of Power Quality monitoring. Standards typically also give ranges of allowed values; the information attributes are the raw measurements, not the "yes/no" determination by the various standards.

Reference:

[ASHRAE-201].

Power State

A Power State is a condition or mode of a device (or component) that broadly characterizes its capabilities, power, and responsiveness to input.

Reference:

Adapted from [IEEE1621].

Power State Set: A Power State Set is a collection of Power States that comprises a named or logical control grouping.

3. Target Devices

With Energy Management, there exists a wide variety of devices that may be contained in the same deployment as a communication network but comprise a separate facility, home, or power distribution network.

Energy Management has special challenges because a power distribution network supplies energy to devices and components, while a separate communications network monitors and controls the power distribution network.

The target devices for Energy Management are all devices that can be monitored or controlled (directly or indirectly) by an Energy Management System (EnMS). These target devices include, for example:

Simple electrical appliances and fixtures

Hosts, such as a PC, a server, or a printer

Switches, routers, base stations, and other network equipment such as middleboxes

Components within devices, e.g., a line card inside a switch

Batteries functioning as a device or component that is a store of energy

Devices or components that charge or produce energy, such as solar cells, charging stations, or generators

Power over Ethernet (PoE) endpoints

Power Distribution Units (PDUs)

Protocol gateway devices for Building Management Systems (BMS)

Electrical meters

Sensor controllers with subtended sensors

Target devices include devices that communicate via the Internet Protocol (IP) as well as devices using other means for communication. The latter are managed through gateways or proxies that can communicate using IP.

4. Physical Reference Model

The following reference model describes physical power topologies that exist in parallel with a communication topology. While many more topologies can be created with a combination of devices, the following are some basic ones that show how Energy Management topologies differ from Network Management topologies.

NOTE:

"###" is used to denote a transfer of energy.

"- >" is used to denote a transfer of information.

Basic Energy Management:

                        +--------------------------+
                        | Energy Management System |
                        +--------------------------+
                                    ^  ^
                         monitoring |  | control
                                    v  v
                                +---------+
                                | device  |
                                +---------+

Basic Power Supply:

                +-----------------------------------------+
                |         Energy Management System        |
                +-----------------------------------------+
                      ^  ^                       ^  ^
           monitoring |  | control    monitoring |  | control
                      v  v                       v  v
                +--------------+        +-----------------+
                | power source |########|      device     |
                +--------------+        +-----------------+

Single Power Supply with Multiple Devices:

                  +---------------------------------------+
                  |       Energy Management System        |
                  +---------------------------------------+
                     ^  ^                       ^  ^
          monitoring |  | control    monitoring |  | control
                     v  v                       v  v
                  +--------+        +------------------+
                  | power  |########|         device 1 |
                  | source |   #    +------------------+-+
                  +--------+   #######|         device 2 |
                                 #    +------------------+-+
                                 #######|         device 3 |
                                        +------------------+

Multiple Power Supplies with Single Device:

             +----------------------------------------------+
             |          Energy Management System            |
             +----------------------------------------------+
                 ^  ^              ^  ^              ^  ^
            mon. |  | ctrl.   mon. |  | ctrl.   mon. |  | ctrl.
                 v  v              v  v              v  v
             +----------+      +----------+      +----------+
             | power    |######|  device  |######| power    |
             | source 1 |      |          |      | source 2 |
             +----------+      +----------+      +----------+

5. Areas Not Covered by the Framework

While this framework is intended as a framework for Energy Management in general, there are some areas that are not covered.

   Non-Electrical Equipment

The primary focus of this framework is the management of electrical equipment. Non-electrical equipment, which is not covered in this framework, could nevertheless be modeled by providing interfaces that comply with the framework: for example, using the same units for power and energy. Therefore, non-electrical equipment that does not "convert to" or "present as" an entity equivalent to electrical equipment is not addressed.

Energy Procurement and Manufacturing

While an EnMS may be a central point for corporate reporting, cost computation, environmental impact analysis, and regulatory compliance reporting, Energy Management in this framework excludes energy procurement and the environmental impact of energy use.

As such, the framework does not include:

Cost in currency or environmental units of manufacturing a device

Embedded carbon or environmental equivalences of a device

Cost in currency or environmental impact to dismantle or recycle a device

Supply chain analysis of energy sources for device deployment

Conversion of the usage or production of energy to units expressed from the source of that energy (such as the greenhouse gas emissions associated with the transfer of energy from a diesel source)

6. Energy Management Abstraction

This section describes a conceptual model of information that can be used for Energy Management. The classes and categories of attributes in the model are described, with a rationale for each.

6.1. Conceptual Model

This section describes an information model that addresses issues specific to Energy Management and complements existing Network Management models.

An information model for Energy Management will need to describe a means to monitor and control devices and components. The model will also need to describe the relationships among, and connections between, devices and components.

This section defines a conceptual model for devices and components that is similar to the model used in Network Management: devices, components, and interfaces. This section then defines the additional attributes specific to Energy Management for those entities that are not available in existing Network Management models.

For modeling the devices and components, this section describes three classes denoted by a "(Class)" suffix: a Device (Class), a Component (Class), and a Power Interface (Class). These classes are sub-types of an abstract Energy Object (Class).

Summary of Notation for Modeling Physical Equipment

Physical Modeling (Metadata) Model Instance

---------------------------------------------------------

equipment Energy Object (Class) Energy Object

device Device (Class) Device

component Component (Class) Component

inlet/outlet Power Interface (Class) Power Interface

This section then describes the attributes of an Energy Object (Class) for identification, classification, context, control, power, and energy.

Since the interconnections between devices and components for Energy Management may have no relation to the interconnections for Network Management, the Energy Object (Classes) contain a separate Relationships (Class) as an attribute to model these types of interconnections.

The next sections describe each of the classes and categories of attributes in the information model.

Not all of the attributes are mandatory for implementations. Specifications describing implementations of the information model in this framework need to be explicit about which are mandatory and which are optional to implement.

The formal definitions of the classes and attributes are specified in Section 7.

6.2. Energy Object (Class)

An Energy Object (Class) represents a piece of equipment that is part of, or attached to, a communications network that is monitored or controlled or that aids in the management of another device for Energy Management.

The Energy Object (Class) is an abstract class that contains the base attributes to represent a piece of equipment for Energy Management. There are three types of Energy Object (Class): Device (Class), Component (Class), and Power Interface (Class).

6.2.1. Device (Class)

The Device (Class) is a subclass of Energy Object (Class) that represents a physical piece of equipment.

A Device (Class) instance represents a device that is a consumer, producer, meter, distributor, or store of energy.

A Device (Class) instance may represent a physical device that contains other components.

6.2.2. Component (Class)

The Component (Class) is a subclass of Energy Object (Class) that represents a part of a physical piece of equipment.

6.2.3. Power Interface (Class)

A Power Interface (Class) represents the interconnections (inlet, outlet) among devices or components where energy can be provided, received, or both.

The Power Interface (Class) is a subclass of Energy Object (Class) that represents a physical inlet or outlet.

There are some similarities between Power Interfaces and network interfaces. A network interface can be set to different states, such as sending or receiving data on an attached line. Similarly, a Power Interface can be receiving or providing energy.

A Power Interface (Class) instance can represent (physically) an AC power socket, an AC power cord attached to a device, or an 8P8C (RJ45) PoE socket, etc.

6.3. Energy Object Attributes

This section describes categories of attributes for an Energy Object (Class).

6.3.1. Identification

A Universally Unique Identifier (UUID) [RFC4122] is used to uniquely and persistently identify an Energy Object.

Every Energy Object has an optional unique human-readable printable name. Possible naming conventions are textual DNS name, Media Access Control (MAC) address of the device, interface ifName, or a text string uniquely identifying the Energy Object. As an example, in the case of IP phones, the Energy Object name can be the device's DNS name.

Additionally, an alternate key is provided to allow an Energy Object to be optionally linked with models in different systems.

6.3.2. Context: General

In order to aid in reporting and in differentiation between Energy Objects, each object optionally contains information establishing its business, site, or organizational context within a deployment.

The Energy Object (Class) contains a category attribute that broadly describes how an instance is used in a deployment. The category indicates whether the Energy Object is primarily functioning as a consumer, producer, meter, distributor, or store of energy.

Given the category and context of an object, an EnMS can summarize or analyze measurements for the site.

6.3.3. Context: Importance

An Energy Object can provide an importance value in the range of 1 to 100 to help rank a device's use or relative value to the site. The importance range is from 1 (least important) to 100 (most important). The default importance value is 1.

For example, a typical office environment has several types of phones, which can be rated according to their business impact. A public desk phone has a lower importance (for example, 10) than a business-critical emergency phone (for example, 100). As another example, a company can consider that a PC and a phone for a customer service engineer are more important than a PC and a phone for lobby use.

Although EnMS and administrators can establish their own ranking, the following example is a broad recommendation for commercial deployments [CISCO-EW]:

      90 to 100  Emergency response
      80 to 90   Executive or business-critical
      70 to 79   General or average
      60 to 69   Staff or support
      40 to 59   Public or guest
      1  to 39   Decorative or hospitality

6.3.4. Context: Keywords

The Energy Object (Class) contains an attribute with context keywords.

An Energy Object can provide a set of keywords that is a list of tags that can be used for grouping, summary reporting (within or between Energy Management Domains), and searching. Potential examples are IT, lobby, HumanResources, Accounting, StoreRoom, CustomerSpace, router, phone, floor2, or SoftwareLab.

The specifics of how this tag is represented are left to the MIB module or other object definition documents to be based on this framework.

There is no default value for a keyword. Multiple keywords can be assigned to an Energy Object.

6.3.5. Context: Role

The Energy Object (Class) contains a role attribute. The "role description" string indicates the primary purpose the Energy Object serves in the deployment. This could be a string representing the purpose the Energy Object fulfills in the deployment.

The specifics of how this tag is represented are left to the MIB module or other object definition documents to be based on this framework.

Administrators can define any naming scheme for the role. As guidance, a two-word role that combines the service the Energy Object provides, along with type, can be used [IPENERGY].

   Example types of devices: Router, Switch, Light, Phone, WorkStation,
   Server, Display, Kiosk, HVAC.

Example Services by Line of Business:

         Line of Business     Service
         ------------------------------------------------------
         Education            Student, Faculty, Administration,
                              Athletic

Finance Trader, Teller, Fulfillment

Manufacturing Assembly, Control, Shipping

         Retail               Advertising, Cashier
         
         Support              Helpdesk, Management

Medical Patient, Administration, Billing

   Role as a two-word string: "Faculty Desktop", "Teller Phone",
   "Shipping HVAC", "Advertising Display", "Helpdesk Kiosk",
   "Administration Switch".

The specifics of how this tag is represented are left to the MIB module or other object definition documents to be based on this framework.

6.3.6. Context: Domain

The Energy Object (Class) contains a string attribute to indicate membership in an Energy Management Domain. An Energy Management Domain can be any collection of Energy Objects in a deployment, but it is recommended to map 1:1 with a metered or sub-metered portion of the site.

In building management, a meter refers to the meter provided by the utility used for billing and measuring power to an entire building or unit within a building. A sub-meter refers to a customer- or user- installed meter that is not used by the utility to bill but is instead used to get measurements from portions of a building.

The specifics of how this tag is represented are left to the MIB module or other object definition documents to be based on this framework.

An Energy Object MUST be a member of a single Energy Management Domain; therefore, one attribute is provided.

6.4. Measurements

The Energy Object (Class) contains attributes to describe power, energy, and demand measurements.

An analogy for understanding power versus energy measurements can be made to speed and distance in automobiles. Just as a speedometer indicates the rate of change of distance (speed), a power measurement indicates the rate of transfer of energy. The odometer in an automobile measures the cumulative distance traveled; similarly, an energy measurement indicates the accumulated energy transferred.

Demand measurements are averages of power measurements over time. So, using the same analogy to an automobile: measuring the average vehicle speed over multiple intervals of time for a given distance traveled, demand is the average power measured over multiple time intervals for a given energy value.

Within this framework, energy will only be quantified in units of watt-hours. Physical devices measuring energy in other units must convert values to watt-hours or be represented by Energy Objects that convert to watt-hours.

6.4.1. Measurements: Power

The Energy Object (Class) contains a Nameplate Power Attribute that describes the nominal power as specified by the manufacturer of the device. The EnMS can use the Nameplate Power for provisioning, capacity planning, and (potentially) billing.

The Energy Object (Class) has attributes that describe the present power information, along with how that measurement was obtained or derived (e.g., actual, estimated, or static).

A power measurement is qualified with the units, magnitude, and direction of power flow and is qualified as to the means by which the measurement was made.

Power measurement magnitude conforms to the [IEC61850] definition of unit multiplier for the SI (System International) units of measure. Measured values are represented in SI units obtained by BaseValue * (10 ^ Scale). For example, if current power usage of an Energy Object is 17, it could be 17 W, 17 mW, 17 kW, or 17 MW, depending on the value of the scaling factor. 17 W implies that BaseValue = 17 and Scale = 0, whereas 17 mW implies that BaseValue = 17 and ScaleFactor = -3.

An Energy Object (Class) indicates how the power measurement was obtained with a caliber and accuracy attribute that indicates:

Whether the measurements were made at the device itself or at a remote source.

Description of the method that was used to measure the power and whether this method can distinguish actual or estimated values.

Accuracy for actual measured values.

6.4.2. Measurements: Power Attributes

The Energy Object (Class) contains an optional attribute that describes Power Attribute information reflecting the electrical characteristics of the measurement. These Power Attributes adhere to the [IEC61850-7-2] standard for describing AC measurements.

6.4.3. Measurements: Energy

The Energy Object (Class) contains optional attributes that represent the energy used, received, produced, and/or stored. Typically, only devices or components that can measure actual power will have the ability to measure energy.

6.4.4. Measurements: Demand

The Energy Object (Class) contains optional attributes that represent demand information over time. Typically, only devices or components that can report actual power are capable of measuring demand.

6.5. Control

The Energy Object (Class) contains a Power State Set (Class) attribute that represents the set of Power States a device or component supports.

A Power State describes a condition or mode of a device or component. While Power States are typically used for control, they may be used for monitoring only.

A device or component is expected to support at least one set of Power States consisting of at least two states: an on state and an off state.

There are many existing standards describing device and component Power States. The framework supports modeling a mixed set of Power States defined in different standards. A basic example is given by the three Power States defined in IEEE1621 [IEEE1621]: on, off, and sleep. The Distributed Management Task Force (DMTF) standards organization [DMTF], Advanced Configuration and Power Interface (ACPI) specification [ACPI], and Printer Working Group (PWG) all define larger numbers of Power States.

The semantics of a Power State are specified by:

a) The functionality provided by an Energy Object in this state.

b) A limitation of the power that an Energy Object uses in this: state.

c) A combination of a) and b).

The semantics of a Power State should be clearly defined. Limitation (curtailment) of the power used by an Energy Object in a state may be specified by:

An absolute power value.

A percentage value of power relative to the Energy Object's Nameplate Power.

An indication of power relative to another Power State. For example, specify that power in state A is less than in state B.

For supporting Power State management, an Energy Object provides statistics on Power States, including the time an Energy Object spent in a certain Power State and the number of times an Energy Object entered a Power State.

When requesting an Energy Object to enter a Power State, an indication of the Power State's name or number can be used. Optionally, an absolute or percentage of Nameplate Power can be provided to allow the Energy Object to transition to a nearest or equivalent Power State.

When an Energy Object is set to a particular Power State, the represented device or component may be busy. The Energy Object should set the desired Power State and then update the actual Power State when the device or component changes. There are then two Power State (Class) control attributes: actual and requested.

The following sections describe well-known Power States for devices and components that should be modeled in the information model.

6.5.1. Power State Sets

There are several standards and implementations of Power State Sets. The Energy Object (Class) supports modeling one or multiple Power State Set implementations on the device or component concurrently.

There are currently three Power State Sets specified by IANA:

      IEEE1621 (256) - [IEEE1621]
      DMTF (512)     - [DMTF]
      EMAN (768)     - [RFC7326]

The respective specific states related to each Power State Set are specified in the following sections. The guidelines for the modification of Power State Sets are specified in the IANA Considerations section.

6.5.2. Power State Set: IEEE1621

The IEEE1621 Power State Set [IEEE1621] consists of three rudimentary states: on, off, or sleep.

In IEEE1621, devices are limited to the three basic Power States -- on (2), sleep (1), and off (0). Any additional Power States are variants of one of the basic states, rather than a fourth state [IEEE1621].

6.5.3. Power State Set: DMTF

The DMTF [DMTF] standards organization has defined a power profile standard based on the CIM (Common Information Model), which consists of 15 Power States.

The DMTF standard is targeted for hosts and computers. Details of the semantics of each Power State within the DMTF Power State Set can be obtained from the DMTF Power State Management Profile specification [DMTF].

The DMTF power profile extends ACPI Power States. The following table provides a mapping between DMTF and ACPI Power State Sets:

       DMTF                                 ACPI
       ------------------------------------------------
       Reserved (0)
       Reserved (1)
       ON (2)                               G0/S0
       Sleep-Light (3)                      G1/S1 G1/S2
       Sleep-Deep (4)                       G1/S3
       Power Cycle (Off-Soft) (5)           G2/S5
       Off-Hard (6)                         G3
       Hibernate (Off-Soft) (7)             G1/S4
       Off-Soft (8)                         G2/S5
       Power Cycle (Off-Hard) (9)           G3
       Master Bus Reset (10)                G2/S5
       Diagnostic Interrupt (11)            G2/S5
       Off-Soft Graceful (12)               G2/S5
       Off-Hard Graceful (13)               G3
       MasterBus Reset Graceful (14)        G2/S5
       Power Cycle Off-Soft Graceful (15)   G2/S5
       Power Cycle Off-Hard Graceful (16)   G3

6.5.4. Power State Set: IETF EMAN

The EMAN Power States are an expansion of the basic Power States as defined in [IEEE1621] plus the addition of the Power States defined in [ACPI] and [DMTF]. Therefore, in addition to the non-operational states as defined in [ACPI] and [DMTF] standards, several intermediate operational states have been defined.

Physical devices and components are expected to support the EMAN Power State Set or to be modeled via an Energy Object the supports these states.

An Energy Object may implement fewer or more Power States than a particular EMAN Power State Set specifies. In that case, the Energy Object implementation can determine its own mapping to the predefined EMAN Power States within the EMAN Power State Set.

There are twelve EMAN Power States that expand on [IEEE1621]. The expanded list of Power States is derived from [CISCO-EW] and is divided into six operational states and six non-operational states.

The lowest non-operational state is 0, and the highest is 5. Each non-operational state corresponds to an [ACPI] Global and System state between G3 (hard-off) and G1 (sleeping). Each operational state represents a performance state and may be mapped to [ACPI] states P0 (maximum performance power) through P5 (minimum performance and minimum power).

In each of the non-operational states (from mechoff(0) to ready(5)), the Power State preceding it is expected to have a lower Power value and a longer delay in returning to an operational state:

mechoff(0): An off state where no Energy Object features are: available. The Energy Object is unavailable. No energy is being consumed, and the power connector can be removed.

      softoff(1): Similar to mechoff(0), but some components remain
         powered or receive trace power so that the Energy Object can be
         awakened from its off state.  In softoff(1), no context is
         saved, and the device typically requires a complete boot when
         awakened.

hibernate(2): No Energy Object features are available. The Energy: Object may be awakened without requiring a complete boot, but the time for availability is longer than sleep(3). An example for state hibernate(2) is a save-to-disk state where DRAM context is not maintained. Typically, energy consumption is zero or close to zero.

sleep(3): No Energy Object features are available, except for: out-of-band management, such as wake-up mechanisms. The time for availability is longer than standby(4). An example for state sleep(3) is a save-to-RAM state, where DRAM context is maintained. Typically, energy consumption is close to zero.

standby(4): No Energy Object features are available, except for: out-of-band management, such as wake-up mechanisms. This mode is analogous to cold-standby. The time for availability is longer than ready(5). For example, processor context may not be maintained. Typically, energy consumption is close to zero.

ready(5): No Energy Object features are available, except for: out-of-band management, such as wake-up mechanisms. This mode is analogous to hot-standby. The Energy Object can be quickly transitioned into an operational state. For example, processors are not executing, but processor context is maintained.

lowMinus(6): Indicates that some Energy Object features may not be: available and the Energy Object has taken measures or selected options to use less energy than low(7).

low(7): Indicates that some Energy Object features may not be: available and the Energy Object has taken measures or selected options to use less energy than mediumMinus(8).

mediumMinus(8): Indicates that all Energy Object features are: available but the Energy Object has taken measures or selected options to use less energy than medium(9).

medium(9): Indicates that all Energy Object features are available: but the Energy Object has taken measures or selected options to use less energy than highMinus(10).

highMinus(10): Indicates that all Energy Object features are: available and the Energy Object has taken measures or selected options to use less energy than high(11).

high(11): Indicates that all Energy Object features are available: and the Energy Object may use the maximum energy as indicated by the Nameplate Power.

6.5.5. Power State Sets Comparison

A comparison of Power States from different Power State Sets can be seen in the following tables:

Non-operational states:

      IEEE1621  DMTF           ACPI         EMAN
      --------------------------------------------------
      off       Off-Hard       G3/S5        mechoff(0)
      off       Off-Soft       G2/S5        softoff(1)
      off       Hibernate      G1/S4        hibernate(2)
      sleep     Sleep-Deep     G1/S3        sleep(3)
      sleep     Sleep-Light    G1/S2        standby(4)
      sleep     Sleep-Light    G1/S1        ready(5)

Operational states:

      IEEE1621  DMTF         ACPI           EMAN
      ----------------------------------------------------
      on        on           G0/S0/P5       lowMinus(6)
      on        on           G0/S0/P4       low(7)
      on        on           G0/S0/P3       mediumMinus(8)
      on        on           G0/S0/P2       medium(9)
      on        on           G0/S0/P1       highMinus(10)
      on        on           G0/S0/P0       high(11)

6.6. Relationships

The Energy Object (Class) contains a set of Relationship (Class) attributes to model the relationships between devices and components. Two Energy Objects can establish an Energy Object Relationship to model the deployment topology with respect to Energy Management.

Relationships are modeled with a Relationship (Class) that contains the UUID of the other participant in the relationship and a name that describes the type of relationship [CHEN]. The types of relationships are Power Source, Metering, and Aggregations.

A Power Source Relationship is a relationship where one Energy Object provides power to one or more Energy Objects. The Power Source Relationship gives a view of the physical wiring topology -- for example, a data center server receiving power from two specific Power Interfaces from two different PDUs.

Note: A Power Source Relationship may or may not change as the direction of power changes between two Energy Objects. The relationship may remain to indicate that the change of power direction was unintended or an error condition.

A Metering Relationship is a relationship where one Energy Object measures power, energy, demand, or Power Attributes of one or more other Energy Objects. The Metering Relationship gives the view of the Metering topology. Physical meters can be placed anywhere in a power distribution tree. For example, utility meters monitor and report accumulated power consumption of the entire building. Logically, the Metering topology overlaps with the wiring topology, as meters are connected to the wiring topology. A typical example is meters that clamp onto the existing wiring.

An Aggregation Relationship is a relationship where one Energy Object aggregates Energy Management information of one or more other Energy Objects. The Aggregation Relationship gives a model of devices that may aggregate (sum, average, etc.) values for other devices. The Aggregation Relationship is slightly different compared to the other relationships, as this refers more to a management function.

In some situations, it is not possible to discover the Energy Object Relationships, and an EnMS or administrator must set them. Given that relationships can be assigned manually, the following sections describe guidelines for use.

6.6.1. Relationship Conventions and Guidelines

This Energy Management framework does not impose many "MUST" rules related to Energy Object Relationships. There are always corner cases that can be excluded by making stricter specifications for relationships. However, the framework proposes a series of guidelines, indicated with "SHOULD" and "MAY".

6.6.2. Guidelines: Power Source

Power Source Relationships are intended to identify the connections between Power Interfaces. This is analogous to a Layer 2 connection in networking devices (a "one-hop connection").

The preferred modeling would be for Power Interfaces to participate in Power Source Relationships. In some cases, Energy Objects may not have the capability to model Power Interfaces. Therefore, a Power Source Relationship can be established between two Energy Objects or two non-connected Power Interfaces.

Strictly speaking, while components and Power Interfaces on the same Device do provide or receive energy from each other, the Power Source Relationship is intended to show energy transfer between Devices. Therefore, the relationship is implied when on the same Device.

An Energy Object SHOULD NOT establish a Power Source Relationship with a component.

A Power Source Relationship SHOULD be established with the next known Power Interface in the wiring topology.

The next known Power Interface in the wiring topology would be the next device implementing the framework. In some cases, the domain of devices under management may include some devices that do not implement the framework. In these cases, the Power Source Relationship can be established with the next device in the topology that implements the framework and logically shows the Power Source of the device.

Transitive Power Source Relationships SHOULD NOT be established. For example, if Energy Object A has a Power Source Relationship "Poweredby" with Energy Object B, and if Energy Object B has a Power Source Relationship "Poweredby" with Energy Object C, then Energy Object A SHOULD NOT have a Power Source Relationship "Poweredby" with Energy Object C.

6.6.3. Guidelines: Metering Relationship

Metering Relationships are intended to show when one device acting as a meter is measuring the power or energy at a point in a power distribution system. Since one point of a power distribution system may cover many devices within a wiring topology, this relationship type can be seen as a set.

Some devices may include hardware that can measure power for components, outlets, or the entire device. For example, some PDUs may have the ability to measure power for each outlet and are commonly referred to as metered-by-outlet. Others may be able to control power at each power outlet but can only measure power at the power inlet -- commonly referred to as metered-by-device.

While the Metering Relationship could be used to represent a device as metered-by-outlet or metered-by-device, the Metering Relationship SHOULD be used to model the relationship between a meter and all devices covered by the meter downstream in the power distribution system.

In general:

A Metering Relationship MAY be established with any other Energy Object, component, or Power Interface.

Transitive Metering Relationships MAY be used.

When there is a series of meters for one Energy Object, the Energy Object MAY establish a Metering Relationship with one or more of the meters.

6.6.4. Guidelines: Aggregation

Aggregation Relationships are intended to identify when one device is used to accumulate values from other devices. Typically, this is for energy or power values among devices and not for components or Power Interfaces on the same device.

The intent of Aggregation Relationships is to indicate when one device is providing aggregate values for a set of other devices when it is not obvious from the power source or simple containment within a device.

Establishing Aggregation Relationships within the same device would make modeling more complex, and the aggregated values can be implied from the use of power inlets, outlet, and Energy Object values on the same device.

Since an EnMS is naturally a point of Aggregation, it is not necessary to model Aggregation for Energy Management Systems.

The Aggregation Relationship is intended for power and energy. It MAY be used for Aggregation of other values from the information model, but the rules and logical ability to aggregate each attribute are out of scope for this document.

In general:

A Device SHOULD NOT establish an Aggregation Relationship with components contained on the same device.

A Device SHOULD NOT establish an Aggregation Relationship with the Power Interfaces contained on the same device.

A Device SHOULD NOT establish an Aggregation Relationship with an EnMS.

Aggregators SHOULD log or provide notification in the case of errors or missing values while performing Aggregation.

6.6.5. Energy Object Relationship Extensions

This framework for Energy Management is based on three relationship types: Aggregation, Metering, and Power Source.

This framework is defined with possible future extension of new Energy Object Relationships in mind.

For example:

Some Devices that may not be IP connected could be modeled with a proxy relationship to an Energy Object within the domain. This type of proxy relationship is left for further development.

A Power Distribution Unit (PDU) that allows devices and components like outlets to be "ganged" together as a logical entity for simplified management purposes could be modeled with an extension called a "gang relationship", whose semantics would specify the Energy Objects' grouping.

7. Energy Management Information Model

This section presents an information model expression of the concepts in this framework as a reference for implementers. The information model is implemented as MIB modules in the different related IETF EMAN documents. However, other programming structures with different data models could be used as well.

Data modeling specifications of this information model may, where needed, specify which attributes are required or optional.

   Syntax
   
      Unified Modeling
      Language (UML)
      Construct
      [ISO-IEC-19501-2005]  Equivalent Notation
      --------------------  ----------------------------------
      Notes                 // Notes
   
      Class
         (Generalization)   CLASS name {member..}
      Subclass
         (Specialization)   CLASS subclass
                                 EXTENDS superclass {member..}
      Class Member
         (Attribute)        attribute : type
   
   Model
   
      CLASS EnergyObject {
   
            // identification / classification
            index        : int
            name         : string
            identifier   : uuid
            alternatekey : string
   
            // context
            domainName      : string
            role            : string
            keywords [0..n] : string
            importance      : int
   
            // relationship
            relationships [0..n] : Relationship
   
            // measurements
            nameplate    : Nameplate
            power        : PowerMeasurement
            energy       : EnergyMeasurement
            demand       : DemandMeasurement
   
            // control
            powerControl [0..n] : PowerStateSet
      }
   
      CLASS PowerInterface EXTENDS EnergyObject {
            eoIfType : enum { inlet, outlet, both }
      }
   
      CLASS Device EXTENDS EnergyObject {
            eocategory             : enum { producer, consumer, meter,
      distributor, store }
            powerInterfaces [0..n] : PowerInterface
            components [0..n]      : Component
      }
   
      CLASS Component EXTENDS EnergyObject {
            eocategory             : enum { producer, consumer, meter,
      distributor, store }
            powerInterfaces [0..n] : PowerInterface
            components [0..n]      : Component
      }
      CLASS Nameplate {
            nominalPower : PowerMeasurement
            details      : URI
      }
   
      CLASS Relationship {
            relationshipType    : enum { meters, meteredby, powers,
      poweredby, aggregates, aggregatedby }
            relationshipObject  : uuid
      }
   
      CLASS Measurement {
            multiplier : enum { -24..24 }
            caliber    : enum { actual, estimated, static }
            accuracy   : enum { 0..10000 } // hundreds of percent
      }
   
      CLASS PowerMeasurement EXTENDS Measurement {
            value          : long
            units          : "W"
            powerAttribute : PowerAttribute
      }

CLASS EnergyMeasurement EXTENDS Measurement {

            startTime : time
            units     : "kWh"
            provided  : long
            used      : long
            produced  : long
            stored    : long
      
      }
      
      CLASS TimedMeasurement EXTENDS Measurement {
            startTime  : timestamp
            value      : Measurement
            maximum    : Measurement
      }
      
      CLASS TimeInterval {
            value      : long
            units      : enum { seconds, milliseconds,... }
      }
      CLASS DemandMeasurement EXTENDS Measurement {
            intervalLength      : TimeInterval
            intervals           : long
            intervalMode        : enum { periodic, sliding, total }
            intervalWindow      : TimeInterval
            sampleRate          : TimeInterval
            status              : enum { active, inactive }
            measurements [0..n] : TimedMeasurements
      }
      
      CLASS PowerStateSet {
            powerSetIdentifier : int
            name               : string
            powerStates [0..n] : PowerState
            operState          : int
            adminState         : int
            reason             : string
            configuredTime     : timestamp
      }
      
      CLASS PowerState {
            powerStateIdentifier : int
            name                 : string
            cardinality          : int
            maximumPower         : PowerMeasurement
            totalTimeInState     : time
            entryCount           : long
      }
      
      CLASS PowerAttribute {
            acQuality  : ACQuality
      }
      
      CLASS ACQuality {
            acConfiguration    : enum { SNGL, DEL, WYE }
            avgVoltage         : long
            avgCurrent         : long
            thdCurrent         : long
            frequency          : long
            unitMultiplier     : int
            accuracy           : int
            totalActivePower   : long
            totalReactivePower : long
            totalApparentPower : long
            totalPowerFactor   : long
      }
      CLASS DelPhase EXTENDS ACQuality {
            phaseToNextPhaseVoltage : long
            thdVoltage              : long
      }
      
      CLASS WYEPhase EXTENDS ACQuality {
            phaseToNeutralVoltage : long
            thdCurrent            : long
            thdVoltage            : long
            avgCurrent            : long
      }

8. Modeling Relationships between Devices

In this section, we give examples of how to use the EMAN information model to model physical topologies. Where applicable, we show how the framework can be applied when devices can be modeled with Power Interfaces. We also show how the framework can be applied when devices cannot be modeled with Power Interfaces but only monitored or controlled as a whole. For instance, a PDU may only be able to measure power and energy for the entire unit without the ability to distinguish among the inlets or outlets.

8.1. Power Source Relationship

The Power Source Relationship is used to model the interconnections between devices, components, and/or Power Interfaces to indicate the source of energy for a device.

In the following examples, we show variations on modeling the reference topologies using relationships.

Given for all cases:

Device W: A computer with one power supply. Power Interface 1 is an: inlet for Device W.

Device X: A computer with two power supplies. Power Interface 1 and: Power Interface 2 are both inlets for Device X.

Device Y: A PDU with multiple Power Interfaces numbered 0..10. Power: Interface 0 is an inlet, and Power Interfaces 1..10 are outlets.

Device Z: A PDU with multiple Power Interfaces numbered 0..10. Power: Interface 0 is an inlet, and Power Interfaces 1..10 are outlets.

Case 1: Simple Device with one Source

Physical Topology:

o Device W inlet 1 is plugged into Device Y outlet 8.

With Power Interfaces:

Device W has an Energy Object representing the computer itself as well as one Power Interface defined as an inlet.

Device Y would have an Energy Object representing the PDU itself (the Device), with Power Interface 0 defined as an inlet and Power Interfaces 1..10 defined as outlets.

The interfaces of the devices would have a Power Source Relationship such that:

Device W inlet 1 is powered by Device Y outlet 8.

+-------+------+ poweredBy +------+----------+

| PDU Y | PI 8 |-----------------| PI 1 | Device W |

+-------+------+ powers +------+----------+

Without Power Interfaces:

Device W has an Energy Object representing the computer.

Device Y would have an Energy Object representing the PDU.

The devices would have a Power Source Relationship such that:

Device W is powered by Device Y.

+----------+ poweredBy +------------+

| PDU Y |-----------------| Device W |

+----------+ powers +------------+

Case 2: Multiple Inlets

Physical Topology:

Device X inlet 1 is plugged into Device Y outlet 8.

Device X inlet 2 is plugged into Device Y outlet 9.

With Power Interfaces:

Device X has an Energy Object representing the computer itself. It contains two Power Interfaces defined as inlets.

Device Y would have an Energy Object representing the PDU itself (the Device), with Power Interface 0 defined as an inlet and Power Interfaces 1..10 defined as outlets.

The interfaces of the devices would have a Power Source Relationship such that:

Device X inlet 1 is powered by Device Y outlet 8.

Device X inlet 2 is powered by Device Y outlet 9.

            +-------+------+        poweredBy+------+----------+
            |       | PI 8 |-----------------| PI 1 |          |
            |       |      |powers           |      |          |
            | PDU Y +------+        poweredBy+------+ Device X |
            |       | PI 9 |-----------------| PI 2 |          |
            |       |      |powers           |      |          |
            +-------+------+                 +------+----------+

Without Power Interfaces:

Device X has an Energy Object representing the computer. Device Y has an Energy Object representing the PDU.

The devices would have a Power Source Relationship such that:

Device X is powered by Device Y.

+----------+ poweredBy +------------+

| PDU Y |-----------------| Device X |

+----------+ powers +------------+

Case 3: Multiple Sources

Physical Topology:

Device X inlet 1 is plugged into Device Y outlet 8.

Device X inlet 2 is plugged into Device Z outlet 9.

With Power Interfaces:

Device X has an Energy Object representing the computer itself. It contains two Power Interfaces defined as inlets.

Device Y would have an Energy Object representing the PDU itself (the Device), with Power Interface 0 defined as an inlet and Power Interfaces 1..10 defined as outlets.

Device Z would have an Energy Object representing the PDU itself (the Device), with Power Interface 0 defined as an inlet and Power Interfaces 1..10 defined as outlets.

The interfaces of the devices would have a Power Source Relationship such that:

Device X inlet 1 is powered by Device Y outlet 8.

Device X inlet 2 is powered by Device Z outlet 9.

            +-------+------+        poweredBy+------+----------+
            | PDU Y | PI 8 |-----------------| PI 1 |          |
            |       |      |powers           |      |          |
            +-------+------+                 +------+          |
                                                    | Device X |
            +-------+------+        poweredBy+------+          |
            | PDU Z | PI 9 |-----------------| PI 2 |          |
            |       |      |powers           |      |          |
            +-------+------+                 +------+----------+

Without Power Interfaces:

Device X has an Energy Object representing the computer. Devices Y and Z would both have respective Energy Objects representing each entire PDU.

The devices would have a Power Source Relationship such that:

Device X is powered by Device Y and powered by Device Z.

+----------+ poweredBy +------------+

| PDU Y |---------------------| Device X |

+----------+ powers +------------+

+----------+ poweredBy +------------+

| PDU Z |---------------------| Device X |

+----------+ powers +------------+

8.2. Metering Relationship

A meter in a power distribution system can logically measure the power or energy for all devices downstream from the meter in the power distribution system. As such, a Metering Relationship can be seen as a relationship between a meter and all of the devices downstream from the meter.

We define in this case a Metering Relationship between a meter and devices downstream from the meter.

     +-----+---+    meteredBy +--------+   poweredBy +-------+
     |Meter| PI|--------------| switch |-------------| phone |
     +-----+---+ meters       +--------+ powers      +-------+
             |                                           |
             |                                 meteredBy |
             +-------------------------------------------+
              meters

In cases where the Power Source topology cannot be discovered or derived from the information available in the Energy Management Domain, the Metering topology can be used to relate the upstream meter to the downstream devices in the absence of specific Power Source Relationships.

A Metering Relationship can occur between devices that are not directly connected, as shown in the following figure:

                          +---------------+
                          |   Device 1    |
                          +---------------+
                          |      PI       |
                          +---------------+
                                  |
                          +---------------+
                          |     Meter     |
                          +---------------+
                                  .
                                  .
                                  .
                 meters        meters           meters
           +----------+   +----------+   +-----------+
           | Device A |   | Device B |   | Device C  |
           +----------+   +----------+   +-----------+

An analogy to communications networks would be modeling connections between servers (meters) and clients (devices) when the complete Layer 2 topology between the servers and clients is not known.

8.3. Aggregation Relationship

Some devices can act as Aggregation points for other devices. For example, a PDU controller device may contain the summation of power and energy readings for many PDU devices. The PDU controller will have aggregate values for power and energy for a group of PDU devices.

This Aggregation is independent of the physical power or communication topology.

The functions that the Aggregation point may perform include the calculation of values such as average, count, maximum, median, minimum, or the listing (collection) of the Aggregation values, etc.

Based on IETF experience gained on Aggregations [RFC7015], the Aggregation function in the EMAN framework is limited to the summation.

When Aggregation occurs across a set of entities, values to be aggregated may be missing for some entities. The EMAN framework does not specify how these should be treated, as different implementations may have good reason to take different approaches. One common treatment is to define the Aggregation as missing if any of the constituent elements are missing (useful to be most precise). Another is to treat the missing value as zero (useful to have continuous data streams).

The specifications of Aggregation functions are out of the scope of the EMAN framework but must be clearly specified by the equipment vendor.

9. Relationship to Other Standards

This Energy Management framework uses, as much as possible, existing standards, especially with respect to information modeling and data modeling [RFC3444].

The data model for power- and energy-related objects is based on [IEC61850].

Specific examples include:

The scaling factor, which represents Energy Object usage magnitude, conforms to the [IEC61850] definition of unit multiplier for the SI (System International) units of measure.

The electrical characteristics are based on the ANSI and IEC Standards, which require that we use an accuracy class for power measurement. ANSI and IEC define the following accuracy classes for power measurement:

IEC 62053-22 and 60044-1 classes 0.1, 0.2, 0.5, 1, and 3.

ANSI C12.20 classes 0.2 and 0.5.

o The electrical characteristics and quality adhere closely to the

[IEC61850-7-4] standard for describing AC measurements.

o The Power State definitions are based on the DMTF Power State

Profile and ACPI models, with operational state extensions.

10. Security Considerations

Regarding the data attributes specified here, some or all may be considered sensitive or vulnerable in some network environments. Reading or writing these attributes without proper protection such as encryption or access authorization will have negative effects on network capabilities. Event logs for audit purposes on configuration and other changes should be generated according to current authorization, audit, and accounting principles to facilitate investigations (compromise or benign misconfigurations) or any reporting requirements.

The information and control capabilities specified in this framework could be exploited, to the detriment of a site or deployment. Implementers of the framework SHOULD examine and mitigate security threats with respect to these new capabilities.

"User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)" [RFC3414] presents a good description of threats and mitigations for SNMPv3 that can be used as a guide for implementations of this framework using other protocols.

10.1. Security Considerations for SNMP

Readable objects in MIB modules (i.e., objects with a MAX-ACCESS other than not-accessible) may be considered sensitive or vulnerable in some network environments. It is important to control GET and/or NOTIFY access to these objects and possibly to encrypt the values of these objects when sending them over the network via SNMP.

The support for SET operations in a non-secure environment without proper protection can have a negative effect on network operations.

For example:

Unauthorized changes to the Energy Management Domain or business context of a device will result in misreporting or interruption of power.

Unauthorized changes to a Power State will disrupt the power settings of the different devices and therefore the state of functionality of the respective devices.

Unauthorized changes to the demand history will disrupt proper accounting of energy usage.

With respect to data transport, SNMP versions prior to SNMPv3 did not include adequate security. Even if the network itself is secure (for example, by using IPsec), there is still no secure control over who on the secure network is allowed to access and GET/SET (read/change/create/delete) the objects in these MIB modules.

It is recommended that implementers consider the security features as provided by the SNMPv3 framework (see [RFC3411]), including full support for the SNMPv3 cryptographic mechanisms (for authentication and confidentiality).

Further, deployment of SNMP versions prior to SNMPv3 is not recommended. Instead, it is recommended to deploy SNMPv3 and to enable cryptographic security. It is then a customer/operator responsibility to ensure that the SNMP entity giving access to an instance of these MIB modules is properly configured to give access to the objects only to those principals (users) that have legitimate rights to GET or SET (change/create/delete) them.

11. IANA Considerations

11.1. IANA Registration of New Power State Sets

This document specifies an initial set of Power State Sets. The list of these Power State Sets with their numeric identifiers is given in Section 6. IANA maintains the lists of Power State Sets.

New assignments for a Power State Set are administered by IANA through Expert Review [RFC5226], i.e., review by one of a group of experts designated by an IETF Area Director. The group of experts must check the requested state for completeness and accuracy of the description. A pure vendor-specific implementation of a Power State Set shall not be adopted, since it would lead to proliferation of Power State Sets.

Power States in a Power State Set are limited to 255 distinct values. A new Power State Set must be assigned the next available numeric identifier that is a multiple of 256.

11.1.1. IANA Registration of the IEEE1621 Power State Set

This document specifies a set of values for the IEEE1621 Power State Set [IEEE1621]. The list of these values with their identifiers is given in Section 6.5.2. IANA created a new registry for IEEE1621 Power State Set identifiers and filled it with the initial list of identifiers.

New assignments (or, potentially, deprecation) for the IEEE1621 Power State Set are administered by IANA through Expert Review [RFC5226].

11.1.2. IANA Registration of the DMTF Power State Set

This document specifies a set of values for the DMTF Power State Set [DMTF]. The list of these values with their identifiers is given in Section 6.5.3. IANA has created a new registry for DMTF Power State Set identifiers and filled it with the initial list of identifiers.

New assignments (or, potentially, deprecation) for the DMTF Power State Set are administered by IANA through Expert Review [RFC5226].

The group of experts must check for conformance with the DMTF standard [DMTF] in addition to checking for completeness and accuracy of the description.

11.1.3. IANA Registration of the EMAN Power State Set

This document specifies a set of values for the EMAN Power State Set. The list of these values with their identifiers is given in Section 6.5.4. IANA has created a new registry for EMAN Power State Set identifiers and filled it with the initial list of identifiers.

New assignments (or, potentially, deprecation) for the EMAN Power State Set are administered by IANA through Expert Review [RFC5226].

11.2. Updating the Registration of Existing Power State Sets

With the evolution of standards, over time, it may be important to deprecate some of the existing Power State Sets, or to add or deprecate some Power States within a Power State Set.

The registrant shall post an Internet-Draft with the clear specification on deprecation of Power State Sets or Power States registered with IANA. The deprecation or addition shall be administered by IANA through Expert Review [RFC5226], i.e., review by one of a group of experts designated by an IETF Area Director. The process should also allow for a mechanism for cases where others have significant objections to claims regarding the deprecation of a registration.

12. References

12.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.
   
   [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.
   
   [RFC3414]  Blumenthal, U. and B. Wijnen, "User-based Security Model
              (USM) for version 3 of the Simple Network Management
              Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
   
   [RFC3444]  Pras, A. and J. Schoenwaelder, "On the Difference between
              Information Models and Data Models", RFC 3444,
              January 2003.
   
   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.
   
   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.
   
   [RFC6933]  Bierman, A., Romascanu, D., Quittek, J., and M.
              Chandramouli, "Entity MIB (Version 4)", RFC 6933,
              May 2013.
   
   [RFC6988]  Quittek, J., Ed., Chandramouli, M., Winter, R., Dietz, T.,
              and B. Claise, "Requirements for Energy Management",
              RFC 6988, September 2013.

[ISO-IEC-19501-2005]

              ISO/IEC 19501:2005, Information technology, Open
              Distributed Processing -- Unified Modeling Language (UML)
              Version 1.4.2, January 2005.

12.2. Informative References

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.
   
   [RFC7015]  Trammell, B., Wagner, A., and B. Claise, "Flow Aggregation
              for the IP Flow Information Export (IPFIX) Protocol",
              RFC 7015, September 2013.
   
   [ACPI]     "Advanced Configuration and Power Interface
              Specification", October 2006,
              <http://www.acpi.info/spec30b.htm>.

[IEEE1621] "Standard for User Interface Elements in Power Control of

Electronic Devices Employed in Office/Consumer

Environments", IEEE 1621, December 2004.

   [NMF]      Clemm, A., "Network Management Fundamentals",
              ISBN-10: 1-58720-137-2, Cisco Press, November 2006.
   
   [TMN]      International Telecommunication Union, "TMN management
              functions", ITU-T Recommendation M.3400, February 2000.
   
   [IEEE100]  "The Authoritative Dictionary of IEEE Standards Terms",
              <http://ieeexplore.ieee.org/xpl/
              mostRecentIssue.jsp?punumber=4116785>.

[ISO50001] "ISO 50001:2011 Energy management systems -- Requirements

with guidance for use", June 2011, <http://www.iso.org/>.

[IEC60050] "International Electrotechnical Vocabulary",

              <http://www.electropedia.org/iev/iev.nsf/
              welcome?openform>.

[IEC61850] "Power Utility Automation",

<http://www.iec.ch/smartgrid/standards/>.

[IEC61850-7-2]

              "Abstract communication service interface (ACSI)",
              <http://www.iec.ch/smartgrid/standards/>.

[IEC61850-7-4]

              "Compatible logical node classes and data classes",
              <http://www.iec.ch/smartgrid/standards/>.
   
   [DMTF]     "Power State Management Profile", DMTF DSP1027
              Version 2.0.0, December 2009,
              <http://www.dmtf.org/sites/default/files/standards/
              documents/DSP1027_2.0.0.pdf>.

[IPENERGY] Aldrich, R. and J. Parello, "IP-Enabled Energy Management:

A Proven Strategy for Administering Energy as a Service", 2010, Wiley Publishing.

   [X.700]    CCITT Recommendation X.700, "Management framework for Open
              Systems Interconnection (OSI) for CCITT applications",
              September 1992.

[ASHRAE-201]

              "ASHRAE Standard Project Committee 201 (SPC 201) Facility
              Smart Grid Information Model",
              <http://spc201.ashraepcs.org>.
   
   [CHEN]     Chen, P., "The Entity-Relationship Model: Toward a Unified
              View of Data", ACM Transactions on Database Systems
              (TODS), March 1976.
   
   [CISCO-EW] Parello, J., Saville, R., and S. Kramling, "Cisco
              EnergyWise Design Guide", Cisco Validated Design (CVD),
              September 2011,
              <http://www.cisco.com/en/US/docs/solutions/
              Enterprise/Borderless_Networks/Energy_Management/
              energywisedg.html>.

13. Acknowledgments

The authors would like to thank Michael Brown for his editorial work, which improved the text dramatically. Thanks to Rolf Winter for his feedback, and to Bill Mielke for his feedback and very detailed review. Thanks to Bruce Nordman for brainstorming, with numerous conference calls and discussions. Finally, the authors would like to thank the EMAN chairs: Nevil Brownlee, Bruce Nordman, and Tom Nadeau.

Appendix A. Information Model Listing

A. EnergyObject (Class):

   r  index         Integer            An [RFC6933] entPhysicalIndex
   
   w  name          String             An [RFC6933] entPhysicalName
   
   r  identifier    uuid               An [RFC6933] entPhysicalUUID
   
   rw alternatekey  String             A manufacturer-defined string
                                       that can be used to identify the
                                       Energy Object
   
   rw domainName    String             The name of an Energy Management
                                       Domain for the Energy Object
   
   rw role          String             An administratively assigned name
                                       to indicate the purpose an
                                       Energy Object serves in the
                                       network
   
   rw keywords      String             A list of keywords or [0..n] tags
                                       that can be used to group Energy
                                       Objects for reporting or
                                       searching
   
   rw importance    Integer            Specifies a ranking of how
                                       important the Energy Object is
                                       (on a scale of 1 to 100) compared
                                       with other Energy Objects
   
   rw relationships Relationship       A list of relationships between
      [0..n]                           this Energy Object and other
                                       Energy Objects
   
   r  nameplate     Nameplate          The nominal PowerMeasurement of
                                       the Energy Object as specified by
                                       the device manufacturer
   
   r  power         PowerMeasurement   The present power measurement of
                                       the Energy Object
   
   r  energy        EnergyMeasurement  The present energy measurement
                                       for the Energy Object
   
   r  demand        DemandMeasurement  The present demand measurement
                                       for the Energy Object
   
   r  powerControl  PowerStateSet      A list of Power States Sets the
      [0..n]                           Energy Object supports

B. PowerInterface (Class) inherits from EnergyObject:

   r  eoIfType      Enumeration        Indicates whether the Power
                                       Interface is an inlet, outlet,
                                       or both

C. Device (Class) inherits from EnergyObject:

   rw eocategory       Enumeration     Broadly indicates whether
                                       the Device is a producer,
                                       consumer, meter, distributor,
                                       or store of energy
   
   r  powerInterfaces  PowerInterface  A list of PowerInterfaces
      [0..n]                           contained in this Device
   
   r  components       Component       A list of components
      [0..n]                           contained in this Device

D. Component (Class) inherits from EnergyObject:

   rw eocategory       Enumeration     Broadly indicates whether the
                                       component is a producer,
                                       consumer, meter, distributor, or
                                       store of energy
   
   r  powerInterfaces  PowerInterface  A list of PowerInterfaces
      [0..n]                           contained in this component
   
   r  components       Component       A list of components contained
      [0..n]                           in this component

E. Nameplate (Class):

   r  nominalPower     PowerMeasurement  The nominal power of the Energy
                                         as specified by the device
                                         manufacturer
   
   rw details          URI               An [RFC3986] URI that links to
                                         manufacturer information about
                                         the nominal power of a device

F. Relationship (Class):

   rw relationshipType    Enumeration   A description of the
   
                                        relationship, indicating
                                        meters, meteredby, powers,
                                        poweredby, aggregates, or
                                        aggregatedby
   
   rw relationshipObject  uuid          An [RFC6933] entPhysicalUUID
                                        that indicates the other
                                        participating Energy Object in
                                        the relationship

G. Measurement (Class):

   r  multiplier  Enumeration    The magnitude of the Measurement
   
                                 in the range -24..24
   
   r  caliber     Enumeration    Specifies how the Measurement was
                                 obtained -- actual, estimated, or
                                 static
   
   r  accuracy    Enumeration    Specifies the accuracy of the
                                 measurement, if applicable, as
                                 0..10000, indicating hundreds of
                                 percent

H. PowerMeasurement (Class) inherits from Measurement:

   r value          Long             A measurement value of
                                     power
   
   r units          "W"              The units of measure for
                                     the power -- "Watts"
   
   r powerAttribute PowerAttribute   Measurement of the electrical
                                     current -- voltage, phase, and/or
                                     frequencies for the
                                     PowerMeasurement

I. EnergyMeasurement (Class) inherits from Measurement:

   r startTime  Time          Specifies the start time of the
   
                              EnergyMeasurement interval
   
   r units      "kWh"         The units of measure for the energy --
                              kilowatt-hours
   
   r provided   Long          A measurement of energy provided
   
   r used       Long          A measurement of energy used/consumed
   
   r produced   Long          A measurement of energy produced
   
   r stored     Long          A measurement of energy stored

J. TimedMeasurement (Class) inherits from Measurement:

   r  startTime timestamp     A start time of a measurement
   
   r  value     Measurement   A measurement value
   
   r  maximum   Measurement   A maximum value measured since a previous
                              timestamp

K. TimeInterval (Class):

   r  value     Long          A value of time
   
   r  units     Enumeration   A magnitude of time, expressed as seconds
                              with an SI prefix (milliseconds, etc.)

L. DemandMeasurement (Class) inherits from Measurement:

   rw intervalLength  TimeInterval     The length of time over which to
                                       compute average energy
   
   rw intervals       Long             The number of intervals that can
                                       be measured
   
   rw intervalMode    Enumeration      The mode of interval
                                       measurement -- periodic, sliding,
                                       or total
   
   rw intervalWindow  TimeInterval     The duration between the starting
                                       time of one sliding window and
                                       the next starting time
   
   rw sampleRate      TimeInterval     The sampling rate at which to
                                       poll power in order to compute
                                       demand
   
   rw status          Enumeration      A control to start or stop demand
                                       measurement -- active or inactive
   
   r  measurements    TimedMeasurement A collection of TimedMeasurements
      [0..n]                           to compute demand

M. PowerStateSet (Class):

   r  powerSetIdentifier Integer       An IANA-assigned value indicating
                                       a Power State Set
   
   r  name               String        A Power State Set name
   
   r  powerStates        PowerState    A set of Power States for the
      [0..n]                           given identifier
   
   rw operState          Integer       The current operational Power
                                       State
   
   rw adminState         Integer       The desired Power State
   
   rw reason             String        Describes the reason
                                       for the adminState
   
   r  configuredTime     timestamp     Indicates the time of
                                       the desired Power State

N. PowerState (Class):

   r  powerStateIdentifier Integer           An IANA-assigned value
                                             indicating a Power State
   
   r  name                 String            A name for the Power State
   r  cardinality          Integer           A value indicating an
                                             ordering of the Power State
   
   rw maximumPower         PowerMeasurement  Indicates the maximum power
                                             for the Energy Object at
                                             this Power State
   
   r  totalTimeInState     Time              Indicates the total time
                                             an Energy Object has been
                                             in this Power State since
                                             the last reset
   
   r  entryCount           Long              Indicates the number of
                                             times the Energy Object
                                             has entered or changed to
                                             this state

O. PowerAttribute (Class):

   r acQuality          ACQuality    Describes AC Power Attributes for
   
                                     a Measurement

P. ACQuality (Class):

   r acConfiguration    Enumeration  Describes the physical
                                     configuration of alternating
                                     current as single phase (SNGL),
                                     three-phase delta (DEL), or
                                     three-phase Y (WYE)
   
   r avgVoltage         Long         The average of the voltage measured
                                     over an integral number of AC
                                     cycles [IEC61850-7-4] 'Vol'
   
   r avgCurrent         Long         The current per phase
                                     [IEC61850-7-4] 'Amp'
   
   r thdCurrent         Long         A calculated value for the current
                                     Total Harmonic Distortion (THD).
                                     The method of calculation is not
                                     specified [IEC61850-7-4] 'ThdAmp'
   
   r frequency          Long         Basic frequency of the AC circuit
                                     [IEC61850-7-4] 'Hz'
   
   r unitMultiplier     Integer      Magnitude of watts for the usage
                                     value in this instance
   
   r accuracy           Integer      Percentage value in 100ths
                                     of a percent, representing the
                                     presumed accuracy of active,
                                     reactive, and apparent power
                                     in this instance
   
   r totalActivePower   Long         A measured value of the actual
                                     power delivered to or consumed by
                                     the load [IEC61850-7-4] 'TotW'
   
   r totalReactivePower Long         A measured value of the reactive
                                     portion of the apparent power
                                     [IEC61850-7-4] 'TotVAr'
   
   r totalApparentPower Long         A measured value of the voltage
                                     and current, which determines the
                                     apparent power as the vector sum of
                                     real and reactive power
                                     [IEC61850-7-4] 'TotVA'
   
   r totalPowerFactor   Long         A measured value of the ratio of
                                     the real power flowing to the load
                                     versus the apparent power
                                     [IEC61850-7-4] 'TotPF'

Q. DelPhase (Class) inherits from ACQuality:

   r phaseToNext      Long      A measured value of phase to
   
      PhaseVoltage              next phase voltages where the
                                next phase is [IEC61850-7-4]
                                'PPV'
   
   r thdVoltage       Long      A calculated value for the
                                voltage Total Harmonic Distortion
                                (THD) for phase to next phase.
                                The method of calculation is not
                                specified [IEC61850-7-4] 'ThdPPV'

R. WYEPhase (Class) inherits from ACQuality:

   r phaseToNeutral  Long   A measured value of phase to
   
      Voltage               neutral voltage [IEC61850-7-4]
                            'PhV'
   
   r thdCurrent      Long   A calculated value for the current
                            Total Harmonic Distortion (THD).
                            The method of calculation is not
                            specified [IEC61850-7-4] 'ThdA'
   
   r thdVoltage      Long   A calculated value of the voltage
                            THD for phase to neutral
                            [IEC61850-7-4] 'ThdPhV'
   
   r avgCurrent      Long   A measured value of phase currents
                            [IEC61850-7-4] 'A'

Authors' Addresses

   John Parello
   Cisco Systems, Inc.
   3550 Cisco Way
   San Jose, CA  95134
   US
   
   Phone: +1 408 525 2339
   EMail: jparello@cisco.com

Benoit Claise
Cisco Systems, Inc.
De Kleetlaan 6a b1
Diegem 1813
BE

   Phone: +32 2 704 5622
   EMail: bclaise@cisco.com
   
   Brad Schoening
   44 Rivers Edge Drive
   Little Silver, NJ  07739
   US
   
   EMail: brad.schoening@verizon.net

Juergen Quittek
NEC Europe Ltd.
Network Laboratories
Kurfuersten-Anlage 36
69115 Heidelberg
Germany

   Phone: +49 6221 90511 15
   EMail: quittek@netlab.nec.de

Energy Management Framework

Abstract

Status of This Memo

Copyright Notice

Table of Contents

1. Introduction

2. Terminology

3. Target Devices

4. Physical Reference Model

"###" is used to denote a transfer of energy.

"- >" is used to denote a transfer of information.

Basic Energy Management:

Basic Power Supply:

Single Power Supply with Multiple Devices:

Multiple Power Supplies with Single Device:

5. Areas Not Covered by the Framework

6. Energy Management Abstraction

6.1. Conceptual Model

Summary of Notation for Modeling Physical Equipment

Physical Modeling (Metadata) Model Instance

---------------------------------------------------------

equipment Energy Object (Class) Energy Object

device Device (Class) Device

component Component (Class) Component

inlet/outlet Power Interface (Class) Power Interface

6.2. Energy Object (Class)

6.2.1. Device (Class)

6.2.2. Component (Class)

6.2.3. Power Interface (Class)

6.3. Energy Object Attributes

6.3.1. Identification

6.3.2. Context: General

6.3.3. Context: Importance

6.3.4. Context: Keywords

6.3.5. Context: Role

Example Services by Line of Business:

Finance Trader, Teller, Fulfillment

Manufacturing Assembly, Control, Shipping

Medical Patient, Administration, Billing

6.3.6. Context: Domain

6.4. Measurements

6.4.1. Measurements: Power

6.4.2. Measurements: Power Attributes

6.4.3. Measurements: Energy

6.4.4. Measurements: Demand

6.5. Control

6.5.1. Power State Sets

6.5.2. Power State Set: IEEE1621

6.5.3. Power State Set: DMTF

6.5.4. Power State Set: IETF EMAN

6.5.5. Power State Sets Comparison

6.6. Relationships

6.6.1. Relationship Conventions and Guidelines

6.6.2. Guidelines: Power Source

6.6.3. Guidelines: Metering Relationship

6.6.4. Guidelines: Aggregation

6.6.5. Energy Object Relationship Extensions

7. Energy Management Information Model

8. Modeling Relationships between Devices

8.1. Power Source Relationship

o Device W inlet 1 is plugged into Device Y outlet 8.

Device W inlet 1 is powered by Device Y outlet 8.

+-------+------+ poweredBy +------+----------+

| PDU Y | PI 8 |-----------------| PI 1 | Device W |

+-------+------+ powers +------+----------+

+----------+ poweredBy +------------+

| PDU Y |-----------------| Device W |

+----------+ powers +------------+

Device X inlet 1 is powered by Device Y outlet 8.

Device X inlet 2 is powered by Device Y outlet 9.

+----------+ poweredBy +------------+

| PDU Y |-----------------| Device X |

+----------+ powers +------------+

Device X inlet 1 is powered by Device Y outlet 8.

Device X inlet 2 is powered by Device Z outlet 9.

Device X is powered by Device Y and powered by Device Z.

+----------+ poweredBy +------------+

| PDU Y |---------------------| Device X |

+----------+ powers +------------+

+----------+ poweredBy +------------+