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Network Working Group J. Quittek
Internet-Draft NEC Europe Ltd.
Intended status: Informational B. Nordman
Expires: September 1, 2011 Lawrence Berkeley National
Laboratory
February 28, 2011
Reference Model for Energy Management
draft-quittek-eman-reference-model-01
Abstract
This memo discusses suggest a reference model for energy consumption
monitoring and control. It defines entities involved in energy
management, their roles, and relationships among them. Considered
entities include powered devices, power monitors, and power
controllers, and energy management systems.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 1, 2011.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Energy Management . . . . . . . . . . . . . . . . . . . . 4
2.2. Energy Monitoring . . . . . . . . . . . . . . . . . . . . 5
2.3. Power, Energy, and Energy Consumption . . . . . . . . . . 5
2.4. Identity . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Energy Monitoring Reference Model . . . . . . . . . . . . . . 5
3.1. Introduction to Energy Monitoring . . . . . . . . . . . . 6
3.1.1. Basic Energy Monitoring (local metering) . . . . . . . 6
3.1.2. External Metering . . . . . . . . . . . . . . . . . . 6
3.1.3. Functions and Entities . . . . . . . . . . . . . . . . 7
3.1.4. Power Monitors . . . . . . . . . . . . . . . . . . . . 7
3.2. Energy Monitoring Entities . . . . . . . . . . . . . . . . 8
3.2.1. Powered Device . . . . . . . . . . . . . . . . . . . . 9
3.2.2. Power Source . . . . . . . . . . . . . . . . . . . . . 9
3.2.3. Power Meter . . . . . . . . . . . . . . . . . . . . . 9
3.2.4. Power Monitors . . . . . . . . . . . . . . . . . . . . 9
3.2.4.1. Power State Monitor . . . . . . . . . . . . . . . 10
3.2.4.2. Power Source Monitor . . . . . . . . . . . . . . . 10
3.2.4.3. Power Usage Monitor . . . . . . . . . . . . . . . 10
3.2.5. Energy Monitoring System . . . . . . . . . . . . . . . 10
3.3. Standardization Scope . . . . . . . . . . . . . . . . . . 10
3.4. Entity Relationships . . . . . . . . . . . . . . . . . . . 11
3.5. Energy Monitoring Scenarios . . . . . . . . . . . . . . . 11
3.5.1. Simple Device with Power Meter . . . . . . . . . . . . 11
3.5.2. External Power Meter . . . . . . . . . . . . . . . . . 12
3.5.3. External Power Meter for Multiple Powered Devices . . 13
3.5.4. Powered Device with Dual Power Supply . . . . . . . . 14
3.5.5. Two energy monitoring systems . . . . . . . . . . . . 15
3.5.6. Power over Ethernet Switch . . . . . . . . . . . . . . 16
3.5.7. Power Distribution Unit . . . . . . . . . . . . . . . 17
3.5.8. Aggregator . . . . . . . . . . . . . . . . . . . . . . 17
3.5.9. Energy Monitoring Gateway . . . . . . . . . . . . . . 18
3.5.10. Further Scenarios . . . . . . . . . . . . . . . . . . 19
4. Energy Management Reference Model . . . . . . . . . . . . . . 19
4.1. Energy Management Entities . . . . . . . . . . . . . . . . 20
4.1.1. Powered Device . . . . . . . . . . . . . . . . . . . . 20
4.1.2. Power Source . . . . . . . . . . . . . . . . . . . . . 21
4.1.3. Power Meter . . . . . . . . . . . . . . . . . . . . . 21
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4.1.4. Power Controllers . . . . . . . . . . . . . . . . . . 21
4.1.4.1. Power State Controller . . . . . . . . . . . . . . 21
4.1.4.2. Power Source Controller . . . . . . . . . . . . . 21
4.1.4.3. Power Meter Controller . . . . . . . . . . . . . . 21
4.1.5. Energy Management System . . . . . . . . . . . . . . . 21
4.2. Reference Points . . . . . . . . . . . . . . . . . . . . . 22
4.3. Entity Relationships . . . . . . . . . . . . . . . . . . . 22
4.4. Energy Management Scenarios . . . . . . . . . . . . . . . 22
4.4.1. Simple Self-Managed Device . . . . . . . . . . . . . . 22
4.4.2. Simple Managed Device . . . . . . . . . . . . . . . . 24
4.4.3. Power over Ethernet Switch . . . . . . . . . . . . . . 26
4.4.4. Power Distribution Unit . . . . . . . . . . . . . . . 27
4.4.5. Energy Management Gateway . . . . . . . . . . . . . . 27
4.4.6. Further Scenarios . . . . . . . . . . . . . . . . . . 28
5. Security Considerations . . . . . . . . . . . . . . . . . . . 28
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 29
8. Open Isues . . . . . . . . . . . . . . . . . . . . . . . . . . 29
8.1. Short name for the protocol . . . . . . . . . . . . . . . 29
8.2. Identity Monitor . . . . . . . . . . . . . . . . . . . . . 29
8.3. Interactions with the EMS . . . . . . . . . . . . . . . . 29
8.4. Third basic state for power source? . . . . . . . . . . . 30
8.5. Collector and Aggregator . . . . . . . . . . . . . . . . . 30
8.6. Gateways and Proxies . . . . . . . . . . . . . . . . . . . 30
9. Informative References . . . . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31
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1. Introduction
Managing energy consumption of devices with network connections is
different from several well understood network management functions
because of the special nature of energy supply and consumption.
The most basic example of energy management is a single device
reporting information about its own energy status.
However, in many cases, energy consumption is not measured by the
powered device itself, but by a power meter located upstream in the
power distribution tree. An example is a power distribution unit
(PDU) that measures energy consumption of attached devices and may
report this to an energy management system. Unlike many other
management functions, the powered device is not involved in this
process.
This memo aims to clarify roles of entities involved in energy
monitoring and control and the relationships among them.
There is already a reference model defined in section 4 of
[I-D.claise-power-management-arch]. The intention of this memo is to
refine this model based on recent discussions.
The reference model specification below describes several kinds of
entities and interactions between them. According to the current
scope of the EMAN WG, only reporting to the energy management system
are potential subjects of standardization in this WG.
The reference model is described in two stages. Stage one is an
energy monitoring model specified in Section 3. It covers only
monitoring of power states and energy consumption. On stage two the
monitoring model is extended to a full energy management reference
model by adding control functions for power supply and power states.
see Section 4.
2. Terminology
This section defines terms used for the description of the energy
management reference model. Names for entities of the model are not
defined here but in Section 3.2 and Section 4.1.
2.1. Energy Management
Energy management deals with assessing and influencing the
consumption of energy in a network of powered devices. A typical
objective of energy management is reducing the energy consumption in
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the network. This objective may be limited by other objectives of a
general network management system, such as service level objectives.
2.2. Energy Monitoring
Energy monitoring is a part of energy management. It only covers
monitoring and does not include influencing the consumption of
energy.
2.3. Power, Energy, and Energy Consumption
Power is the rate of energy conversion. In energy management
scenarios, electrical energy is delivered to a device that consumes
it by converting the energy to other forms.
Power and consumed energy are essential quantities for network
management. Power can be an instantaneous value of the current
energy conversion rate or an average value of power over a time
interval. Consumed energy is the total energy converted by a powered
device during a time interval.
The term 'energy consumption' is commonly used for both, for
referring to the amount of consumed energy and also for referring to
the process of consuming energy. In this document we use this
ambiguous term for addressing both power and consumed energy.
2.4. Identity
Identity is basic information about what a device is, in function, in
its specific instance of manufacture, and its specific local human-
readable name. Identity is not energy-specific, but essential for
useful interpretation of energy information.
Some identify information never changes. The rest of it rarely or
never changes. Thus, it needs to be queried much less frequently
than the energy data.
3. Energy Monitoring Reference Model
This section specifies a reference model for energy monitoring.
After introducing basic concepts of energy monitoring in Section 3.1
it defines entities of the model and their interactions in
Section 3.2. Examples of devices and scenarios are illustrated in
Section 3.5.
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3.1. Introduction to Energy Monitoring
In this section we introduce basic concepts of energy monitoring
starting with the most basic scenario and extending it stepwise to
our full reference model.
The main subject of energy monitoring is a powered device. An energy
monitoring system collects information about powered devices, their
current power state (for example: on, sleep, off) and their actual
power consumption.
3.1.1. Basic Energy Monitoring (local metering)
The most basic interaction in an energy monitoring system is a
powered device directly reporting its own energy-related information,
with no other devices involved, as shown below.
energy monitoring
system
^
|
device
3.1.2. External Metering
Reporting its current power state is a relatively easy task for a
powered device because usually information on the current power state
is locally available at the device and a reporting function just
needs some additional software to implement it.
Reporting the current power level of a device and its accumulated
energy consumption is a harder task, particularly if there are strict
requirements for accuracy. Today very few devices are instrumented
with means for measuring their own energy consumption as that usually
implies adding hardware for this purpose.
This can be addressed by external meters, that is, dedicated probes
that can meter energy consumption on a power source (line). Some
Power Distributions Units (PDUs) and Power over Ethernet (PoE)
[IEEE-802.3af] switches integrate power source and power metering for
individual devices.
For supporting scenarios with external meters we extend the basic
model from above by an external power meter and a power source as
shown below.
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energy monitoring system
^ ^ ^
| | |
power power powered
source meter device
###############
symbols ######### represent a power supply line
All three potentially report to the energy monitoring system. The
power meter may report the current power and accumulated energy
consumption and the power source may report if the power supply for
the device is switched on or if it is off.
Implementation may be incomplete. For example, an energy management
system may have access to only one or two of these three types of
data.
3.1.3. Functions and Entities
This reference model operates at two levels/layers. One is simple
basic functions that are implemented. The second is how they are
arranged in devices. A device in this model may implement only a
single function, or may implement many.
That is, having multiple entities does not require that all of them
need to be instantiated by individual devices. For example, the
power meter function may be co-located and integrated with the
powered device, with the power source, or it may be implemented by a
separate device.
3.1.4. Power Monitors
In the models above, the powered device and other components deliver
reports directly to an energy monitoring system. However, there are
energy monitoring scenarios where this is not possible or not
desirable.
Extreme examples are energy consumers that do not have IP interfaces
but can communicate by other means. For delivering their reports to
an IP-based energy monitoring system, it may be required to use a
gateway that can communicate with the energy monitoring system.
However, even if all involved devices (PDUs, power meters, and
powered devices) can communicate via IP, it may be desirable to have
mediation functions in place between powered devices and the energy
monitoring system. An example, is an aggregating device that
aggregates and reports information on several powered devices.
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There are several further useful scenarios. To generalize the model
(and to not exclude any kind of gateway, proxy, relay, mediator or
other device) we define reporting entities called 'monitors'. The
figure below shows three monitors, each of which reports to the
energy monitoring system. This figure is the most generic
representation of the energy monitoring reference model described by
this document.
Energy Monitoring Reference Model
+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^ ^ ^
| | |
+-------------------+ +-------------------+ +-------------------+
| power source | | power usage | | power state |
| monitor | | monitor | | monitor |
+-------------------+ +-------------------+ +-------------------+
| | |
+-------------------+ +-------------------+ +-------------------+
| power | | power meter | | powered |
| source | +-------------------+ | device |
+-------------------+###########################+-------------------+
symbols ######### represent a power supply line
A monitor function reports directly to the energy monitoring system
using the EMON protocol (an Internet protocol). A monitor must have
means to acquire the information it reports, but how this information
is acquired is not relevant for our model. That is, only the
interactions with a caret symbol in this and following diagrams is
the subject of standardization. Those with only the vertical bar
character are outside the scope of these documents; they may be IP or
non-IP.
The reference model defines the communication between power monitors
an the energy monitoring system. The communication lines between
these entities are reference points of our model described in more
detail in the following.
3.2. Energy Monitoring Entities
This section defines entities of the energy monitoring reference
model and describes interactions between them. Examples scenarios
are illustrated in Section 3.5.
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3.2.1. Powered Device
A powered device is provided with energy (typically electrical)
usuallly provided via power lines. Power state, power and consumed
energy of powered devices are subject to monitoring and control
functions of energy management.
3.2.2. Power Source
A power source provides a powered device with energy, typically via a
power line. It may have means to switch on and off the power for the
powered device. A power source does not necessarily generate power,
but it may do so. It may be as simple as a power switch or a power
plug, but it may also be a battery or a power generator. Regardless,
the nature of the source does not affect energy monitoring.
Note that an internal battery within a device, such as the battery of
a notebok PC or of a mobile phone are not considered to be a power
source. When a device runs on battery only, there is n flow of
energy into the device and consequently the power to be reported for
this device is zero. On the other hand, when a device charges its
battery, then the power supplied for charging needs to be accounted,
even if the device is not operational.
3.2.3. Power Meter
A power meter measures power and/or consumed energy, and typically is
electrically connected to power supply lines for powered devices.
However, many devices can also provide a reliable estimate of their
power consumption based on internal status information without having
dedicated metering hardware. Regardless, all metering information is
qualified by an indication of its accuracy.
The meter function also includes integrating power consumption over
time to provide a "meter reading" with a time stamp to enable an
energy monitoring system to track energy consumption over time.
3.2.4. Power Monitors
A power monitor has access to energy-related information concerning
powered devices and is able to report this information to energy
management systems.
A power monitor may also provide information on identity and
properties of a powered device to the management system.
A power monitor may store energy-related information and process it,
for example, for aggregating information or for extracting statistics
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that are provided to an energy management system.
There are three power monitor functions in the energy monitoring
reference model: power state monitors, power source monitors, and
power usage monitors.
3.2.4.1. Power State Monitor
A power state monitor has access to the power state of a powered
device and is able to report this information to an energy monitoring
system. For acquiring power state information it may interact with
powered devices.
3.2.4.2. Power Source Monitor
A power state monitor has access to information on the power supply
of powered devices and is able to report this information to an
energy monitoring system. Typically, it will just report either 'on'
or 'off'. In addition, it may report on power availability. For
acquiring power source information it may interact with the power
sources of powered devices.
3.2.4.3. Power Usage Monitor
A power usage monitor has access to information on energy consumption
of powered devices and is able to report this information to energy
management systems. For acquiring information on energy consumption
it may interact with power meters.
3.2.5. Energy Monitoring System
An energy monitoring system receives information from power monitors,
such as: power states, power source states, and energy consumption.
An energy monitoring system may be centralized or distributed. In
most of the example scenarios illustrated in Section 3.5 a
centralized energy monitoring system is shown but in all cases can be
replaced by a distributed monitoring system.
3.3. Standardization Scope
The reference model specifies interactions of an energy monitoring
system with power monitors. They reference points of the model are
potential subjects of standardization (in the EMAN working group).
Interactions of power monitors with other entities are currently not
considered to be subject of standardization.
It is argued in [I-D.quittek-power-monitoring-requirements] that for
most of the relevant scenarios the best choice a management protocol
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for the reference points is SNMP [RFC3410]. The reference model
defined in this document does not assume a specific protocol between
energy monitoring system and power monitors. It is also applicable
if other protocols, such as, for example, Syslog [RFC5675] or IPFIX
[RFC5101] are used.
3.4. Entity Relationships
No restrictions on entity relationships have been identified for
interacting entities of the energy monitoring reference model
specified in this document. This means that all relationships
between entities may be one-to-one, one-to-many, many-to-one, or
many-to-many. For example,
o a single power state monitor may report the power state of
multiples powered entities,
o a single powered entity may have its power states reported by<
multiple power state monitors,
o a single powered device may receive power from several power
sources,
o a single power monitor may report to multiple energy monitoring
systems.
A few of scenarios with multiple instances of units are illustrated
by the examples in the following Section 3.5.
3.5. Energy Monitoring Scenarios
This section describes common example scenarios for energy monitoring
and how they are modeled with the entities and interactions described
in the previous sections.
3.5.1. Simple Device with Power Meter
A very basic example is a powered device that has a built-in meter
for measuring its own energy consumption and that reports its power
state and power usage directly to the energy monitoring system.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+-----------------------------------------------+
| | |
| +-----------+-----------+ |
| | | |
| +-------------------+ +-------------------+ |
| | power usage | | power state | |
| | monitor | | monitor | |
| +-------------------+ +-------------------+ |
| | | |
+-----------------+ | +-------------------+ +-------------------+ |
| power | | | power meter | | powered | |
| source | | +---------#---------+ | device | |
+-----------------+#|#########################+-------------------+ |
| |
| powered device with meter and power monitors |
+-----------------------------------------------+
Scenario 1: Powered device metering and self-reporting
Here four entities are combined in a single device: the powered
device, the power meter, and two power monitors.
3.5.2. External Power Meter
The second example shows a power meter that is attached to the power
line of a powered device that does not have means for measuring its
own energy consumption. The meter is integrated with a power usage
monitor that reports metered data. The powered device may report its
own power state by an integrated power state monitor.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+-----------------------+
| external | meter |
| +-------------------+ |
| | power usage | |
| | monitor | |
| +-------------------+ |
| | |
| +-------------------+ |
+-----------------+ | | power meter | | +-------------------+
| power | | +---------#---------+ | | powered |
| source | +-----------#-----------+ | device |
+-----------------+#############################+-------------------+
Scenario 2: An external meter
3.5.3. External Power Meter for Multiple Powered Devices
Power meters may be located at a power line that provides power for
multiple powered devices. In scenario 3, a single power meter
measures the accumulated power and energy consumption of multiple
powered devices. In general, In this scenario it is usually not
possible to derive power values for the individual powered devices
from the accumulated measurement.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+-----------------------+
| external | meter |
| +-------------------+ |
| | power usage | | +----------------+
| | monitor | | | powered |
| +-------------------+ | | device |
| | | ###+----------------+
| +-------------------+ | #
+-----------------+ | | power meter | | # +----------------+
| power | | +---------#---------+ | # | powered |
| source | +-----------#-----------+ # | device |
+-----------------+################################+----------------+
#
# +----------------+
# | powered |
# | device |
###+----------------+
Scenario 3: An external meter for multiple powered devices
3.5.4. Powered Device with Dual Power Supply
Some powered devices have dual power supply. It may be that one
supply comes from a power grid and the other one from a battery.
High-reliability devices may have two power sources from different
power distribution networks, as shown in scenarios 4 and 5.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+-----------------------------------------+
| | |
| +-------------------------------------+ |
| | power usage monitor | |
| +-------------------------------------+ |
| | | |
| +---------+ +-----------+ +---------+ |
+---------+ | | power | | powered | | power | | +---------+
| power | | | meter | | device | | meter | | | power |
| source | | +----#----+ | | +----#----+ | | source |
+---------+##|##############+-----------+##############|##+---------+
| |
| powered device with dual power supply |
| and dual metering |
+-----------------------------------------+
Scenario 4: powered device with dual power supply
In scenario 4 the device uses two meters, one for each power line and
reports from both to the energy monitoring system. If the two power
sources belong to different power distribution domains, it may be
necessary to report power and energy separately for each supply.
3.5.5. Two energy monitoring systems
Scenario 5 is more complex. Both meters are individual external
devices and there are even two separate energy monitoring systems
involved, one for each power distribution tree.
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+-------------------------------+ +-------------------------------+
| energy monitoring system | | energy monitoring system |
+-------------------------------+ +-------------------------------+
^ ^
| |
+-----------+ +-----------+
| | | | | |
| +-------+ | | +-------+ |
| |power | | | |power | |
| |usage | | | |usage | |
| |monitor| | | |monitor| |
| +-------+ | | +-------+ |
| | | | | |
| +-------+ | | +-------+ |
| | power | | | | power | |
+--------+ | | meter | | +-------------+ | | meter | | +--------+
| power | | +---#---+ | | powered | | +---#---+ | | power |
| source | +-----#-----+ | device | +-----#-----+ | source |
+--------+#################+-------------+#################+--------+
Scenario 5: powered device with dual power supply
from different power distribution trees
3.5.6. Power over Ethernet Switch
This example shows a Power over Ethernet (PoE) [IEEE-802.3af] switch
supplying a powered device. The switch contains a power source and a
meter for each of its ports.
There typically are multiple instances of power sources and power
meters in a PoE switch, but the drawing below shows only a single
instance. The same applies to the powered devices that are
represented by a single instance only.
Note that a typical PoE switch has also means to control power supply
for powered devices (not shown here). Control of power supply is a
subject of Section 4.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+---------------------------------------------+
| | |
| +----------+-----------+ |
| | | |
| +-----------------+ +-------------------+ |
| | power source | | power usage | |
| | monitor | | monitor | |
| +-----------------+ +-------------------+ |
| | | |
| +-----------------+ +-------------------+ | +-------------------+
| | power | | power meter | | | powered |
| | source | +---------#---------+ | | device |
| +-----------------+#########################|#+-------------------+
| |
| Power over Ethernet switch |
| or Power Distribution Unit |
+---------------------------------------------+
Scenarios 6 & 7: Power over Ethernet switch or Power Distribution
Unit reporting on power source and power usage of powered devices
In this scenario the identification of the powered device can be done
by the PoE switch by observing MAC and IP addresses of the powered
devices. The switch can report them to the energy management system
which then in turn can contact the devices directly to obtain further
information.
3.5.7. Power Distribution Unit
The same figure as used for the PoE switch in the previous section is
be used for scenario 7 modeling a power distribution unit (PDU). A
PDU with meters for every socket can report power for each.
Identifying the powered devices can more difficult in this scenario
than in the previous one with the PoE switch, because the PDU does
not necessarily communicate with the powered devices. In this case
the PDU or EMS needs to obtain this information by other means, for
example by manual configuration.
3.5.8. Aggregator
Scenario 8 shows a power usage monitor acting as an aggregator. It
collects power information from three powered devices and delivers
all of the information to the energy monitoring system. The
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aggregator may deliver the full information or aggregated
information, for example, just the sum of the power of all three
powered devices.
+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+-------------------------------------------------------------------+
| power usage monitor |
+-------------------------------------------------------------------+
| | |
+-------------------+ +-------------------+ +-------------------+
| | | | | | | | |
|+-------+ +-------+| |+-------+ +-------+| |+-------+ +-------+|
|| power | |powered|| || power | |powered|| || power | |powered||
|| meter | |device || || meter | |device || || meter | |device ||
|+-------##+-------+| |+-------##+-------+| |+-------##+-------+|
+--------#----------+ +--------#----------+ +--------#----------+
# # #
+-------------------------------------------------------------------+
| power source |
+-------------------------------------------------------------------+
Scenario 8: An aggregator collecting monitoring information
from three powered devices
3.5.9. Energy Monitoring Gateway
Some energy monitoring scenarios include a gateway between the
monitored units and the energy monitoring system. The powered device
and the power meter may use means of communication other than IP.
The gateway is a relay and protocol converter that delivers energy
information to a power monitor. A single device may implement
logically independent gateways for multiple devices.
Scenario 9 can easily extended to a gateway that also contains a
power source monitor.
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+-------------------------------------------------------------------+
| energy monitoring system |
+-------------------------------------------------------------------+
^
|
+---------------------------------------------+
| | |
| +-----------+----------+ |
| | | |
| +-------------------+ +-----------------+ |
| | power usage | | power state | |
| | monitor | | monitor | |
| +-------------------+ +-----------------+ |
| gateway | | |
+---------------------------------------------+
| |
+-------------------+ +-------------------+ +-----------------+
| power | | power meter | | powered |
| source | +---------#---------+ | device |
+-------------------+###########################+-----------------+
Scenario 9: A gateway between monitored devices
and energy monitoring system
Here again, the problem of identifying the powered device has become
very difficult, because neither can the power monitor provide an IP
address of the powered device to the energy management system nor can
the energy management system directly communicate with the powered
device. Identification must be provided by other means. The Proxy
can have a gateway function and relay identification between powered
device and energy management system or the energy management system
needs to acquire information on powered devices by other means, such
as manual configuration.
3.5.10. Further Scenarios
More scenarios may be added to future versions of this document.
Particularly, scenarios with multiple instances of an entity have not
been elaborated a lot. Section 4.4 shows scenarios for energy
control. They can also be considered as further monitoring scenarios
if only their power monitors are considered and power controllers are
ignored.
4. Energy Management Reference Model
This section extends the energy monitoring reference model specified
in the previous Section 3 by adding power control functions. The
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resulting model is a complete energy management reference model.
As in Section 3 we first discuss entities and their relationships and
then illustrate the model with example scenarios.
The extension from energy monitoring to energy management is straight
forward. To achieve the required control functions the power source,
power meter, and powered device have additional functions for
control. For each power monitor a corresponding power controller is
added as shown below.
Energy Management Reference Model
+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
^ | ^ | ^ |
| v | v | v
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| power | | power | | power | | power | | power | | power |
| source | | source | | usage | | meter | | state | | state |
| monitor| | ctrler | | monitor| | ctrler | | monitor| | ctrler |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
| | | | | |
+-------------------+ +-------------------+ +-------------------+
| power | | power meter | | powered |
| source | +-------------------+ | device |
+-------------------+###########################+-------------------+
symbols ######### represent a power line
4.1. Energy Management Entities
This section defines entities of the energy management reference
model and describes interactions between them. Examples scenarios
are illustrated in Section 4.4. For entities already specified in
Section 3.2 of the energy monitoring reference model, only their
additional properties are mentioned here. Power monitors are not
discussed here again, because their specification in the energy
management reference model do not change.
4.1.1. Powered Device
A powered device may be capable of changing its own power state from
a request from the energy management system. Some devices may not be
able to power up from an off state based on EMS request. Most
devices that are asleep will be able to wake on EMES request.
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4.1.2. Power Source
A power source may be capable of switching on and off power for
powered devices.
4.1.3. Power Meter
A power meter may be switched on or off or have its metering
parameters modified.
4.1.4. Power Controllers
A power controller receives commands from an energy management system
to change the status or parameters of power sources, power meters, or
powered devices.
There are three kinds of power controller entities: power state
controllers, power source controllers, and power meter controllers.
4.1.4.1. Power State Controller
A power state controller can initiate a change in the power state of
a powered device.
4.1.4.2. Power Source Controller
A power source controller can change the power supply of a powered
device. Typically, it has means for switching power supply on and
off. It may use these means without communicating with the affected
powered device.
4.1.4.3. Power Meter Controller
A power meter controller has means for influencing the operation of a
power meter. It may switch on and off the power meters and change
parameters of their operation. For this purpose it may interact with
power meters.
4.1.5. Energy Management System
An energy management system is an energy monitoring system extended
by control functions. It interacts with power monitors and power
controllers in order to achieve objectives of energy management.
It sends commands to power controllers. To power state controllers
it sends requested power states for powered devices. To power source
controllers it requests to switch on or off power for powered
devices. To power meter controllers it sends commands concerning the
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operation of power meters.
4.2. Reference Points
Relevant for our reference model are interactions of the energy
management system with power monitors and power controllers. They
are reference points of our model and potential subjects of
standardization in the EMAN working group. Interactions of power
monitors and power controllers with other entities are currently not
considered to be subject of standardization.
Monitoring protocols have already been discussed in Section 3.3.
There are several choices of control protocols to be used for energy
management. Among them are SNMP [RFC3410] and NETCONF [RFC4741].
4.3. Entity Relationships
The considerations on entity relationships for the energy monitoring
reference model described in Section 3.4. apply as well to the energy
management reference model: No restrictions on entity relationships
have been identified.
4.4. Energy Management Scenarios
This section describes example scenarios for energy management and
how they are modeled with the entities and interactions described
above.
4.4.1. Simple Self-Managed Device
The first two examples are expected to become very common scenarios.
Here, a powered device is managing its power state on its own based
on input other than from the energy management system. The device
may decide to change power state based on observation of its
environment (no current load, high temperature, not sufficient light,
scheduled time for service interruption, etc.) or it may receive
external triggers, such as by a human-operated remote control.
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
^
|
+-----------------------+
| | |
| +--------+ +--------+ |
| | power | | power | |
| | state | | state | |
| | monitor| | ctrler | |
| +--------+ +--------+ |
| | | |
+-----------------+ | +-------------------+ |
| power | | | powered | |
| source | | | device | |
+-----------------+#|#########################+-------------------+ |
| |
| powered device with |
| power state control |
+-----------------------+
Scenario 10: A self-managed powered device
In any way, it's power state control is independent of the energy
management system. The only interaction with the system is reporting
of power state to the energy management system in scenario 10, and in
addition reporting of its current power and/or accumulated consumed
energy in scenario 11.
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
^
|
+-----------------------------------------------+
| | |
| +-----------------+-----+ |
| | | |
| +--------+ +--------+ +--------+ +--------+ |
| | power | | power | | power | | power | |
| | usage | | meter | | state | | state | |
| | monitor| | ctrler | | monitor| | ctrler | |
| +--------+ +--------+ +--------+ +--------+ |
| | | | | |
+-----------------+ | +-------------------+ +-------------------+ |
| power | | | power meter | | powered | |
| source | | +---------#---------+ | device | |
+-----------------+#|#########################+-------------------+ |
| |
| powered device with built-in meter |
| and autonomous control |
+-----------------------------------------------+
Scenario 11: A self-managed powered device with built-in meter
In scenario 11 also the control of the power meter is handled by the
device itself.
4.4.2. Simple Managed Device
In our model, the scenario does not change much if the powered
devices are not self-managed but managed by the energy management
system. Scenarios 12 and 13 show that just an interaction between
the energy management system and the powered device is added that
serves for sending commands concerning power states to the device.
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
^ |
| |
+-----------------------+
| | v |
| +--------+ +--------+ |
| | power | | power | |
| | state | | state | |
| | monitor| | ctrler | |
| +--------+ +--------+ |
| | | |
+-----------------+ | +-------------------+ |
| power | | | powered | |
| source | | | device | |
+-----------------+#########################|#+-------------------+ |
| |
| powered device with |
| power state control |
+-----------------------+
Scenario 12: A managed powered device
Control of the power meter by the management system can easily added
to scenario 13. It is not included here, because for built-in meters
this seems not to be necessary in many common cases.
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
^ |
| |
+-----------------------------------------------+
| | | |
| +-----------------+-----+ | |
| | | v |
| +--------+ +--------+ +--------+ +--------+ |
| | power | | power | | power | | power | |
| | usage | | meter | | state | | state | |
| | monitor| | ctrler | | monitor| | ctrler | |
| +--------+ +--------+ +--------+ +--------+ |
| | | | | |
+-----------------+ | +-------------------+ +-------------------+ |
| power | | | power meter | | powered | |
| source | | +---------#---------+ | device | |
+-----------------+#|#########################+-------------------+ |
| |
| powered device with built-in meter |
| and autonomous control |
+-----------------------------------------------+
Scenario 13: A managed powered device with built-in meter
4.4.3. Power over Ethernet Switch
Scenario 14 adds control functions to the PoE switch of scenario 6 in
Section 3.5. Here the energy management system can explicitly
request the power for a powered device to be switched on or off. It
also can switch on and off metering and reporting of energy
consumption per port of the switch
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
| ^ | ^
| | | |
+-------------------------------------------+ +---------------------+
| | | | | | | |
| +----------------+----+ | | | | |
| | v | v | | | |
|+--------+ +--------+ +--------+ +--------+| |+--------+ +--------+|
|| power | | power | | power | | power || || power | | power ||
|| source | | source | | usage | | meter || || state | | state ||
|| monitor| | ctrler | | monitor| | ctrler || || monitor| | ctrler ||
|+--------+ +--------+ +--------+ +--------+| |+--------+ +--------+|
| | | | | | | | | |
|+-------------------+ +-------------------+| |+-------------------+|
|| power | | power meter || || powered ||
|| source | +---------#---------+| || device ||
|+-------------------+######################|#|+-------------------+|
| | | |
| Power over Ethernet switch | | powered device with |
| or Power Distribution Unit | | power state control |
+-------------------------------------------+ +---------------------+
Scenario 14 & 15: Power over Ethernet switch
or Power Distribution Unit
Still, the powered device in this scenario is self-managed
controlling its power state on its own and just reporting it to the
energy management system.
4.4.4. Power Distribution Unit
Again, as in Section 3.5 the scenario for a power distribution unit
looks exactly the same in our reference model as the scenario for a
power distribution unit.
4.4.5. Energy Management Gateway
Starting from an energy monitoring gateway in Section 3.5 the
extension towards an energy management gateway is again straight
forward.
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+-------------------------------------------------------------------+
| energy management system |
+-------------------------------------------------------------------+
| ^ |
| | |
+-----------------------------------------------+
| | | | |
| +-----------------+-----+ | |
| | gateway v | v |
| +--------+ +--------+ +--------+ +--------+ |
| | power | | power | | power | | power | |
| | usage | | meter | | state | | state | |
| | monitor| | ctrler | | monitor| | ctrler | |
| +--------+ +--------+ +--------+ +--------+ |
| | | | | |
+-----------------------------------------------+
| | | |
+-----------------+ +-------------------+ +-------------------+
| power | | power meter | | powered |
| source | +---------#---------+ | device |
+-----------------+###########################+-------------------+
Scenario 16: A gateway between powered devices
and energy monitoring system
Here again, the problem of identifying the powered device has become
very difficult, because neither can the power monitor provide an IP
address of the powered device to the energy management system nor can
the energy management system directly communicate with the powered
device. Identification must be provided by other means. The Proxy
can have a gateway function and relay identification between powered
device and energy management system or the energy management system
needs to acquire information on powered devices by other means, such
as manual configuration.
4.4.6. Further Scenarios
More scenarios may be added to future versions of this document.
Particularly, scenarios with multiple instances of an entity have not
been elaborated, yet. Section 4.4 shows scenarios for energy
control. They can also be considered as further monitoring scenarios
if only their power monitors are considered and power controllers are
ignored.
5. Security Considerations
This memo currently does not impose any security considerations.
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6. IANA Considerations
This memo has no actions for IANA..
7. Acknowledgements
This memo was inspired by discussions with Benoit Claise, John
Parello, Mouli Chandramouli, Rolf Winter, Thomas Dietz, Bill Mielke,
and Chris Verges at IETF #79.
8. Open Isues
8.1. Short name for the protocol
We talk a lot in this document about reporting energy-related
information to an energy management system. For this purpose the
SNMP protocol will be used and required MIB modules are under
development at the EMAN WG. It may simplify the text if we can refer
to the process of reporting energy-related information with a
placeholder, for example, 'EMON' for energy monitoring.
8.2. Identity Monitor
Shall we add a new building block called 'identity Monitor'?. This
would tie in the work of the so-called POWER-AWARE-MIB.
8.3. Interactions with the EMS
Shall we discuss different kinds of interactions with the EMS? These
would include
o broadcasting to a subnet asking for all power monitors to report,
o addressing a specific device and asking for all power monitor
information it has,
o asking a specific device about itself,
o asking a specific device for specific information, which could
include particular proxied devices, or pieces of EMON (state,
meter, source, identity), aggregated data, or collected data.
Basically, these interactions are all cvered bythe IETF netwrk
management framework. The question is whether to mention it
explicitly in the reference model.
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8.4. Third basic state for power source?
So far, a power source has the two basic states 'on' and 'off'.
Should we describe a third basic state for a power source. This
would be minimal (?trickle) power to enable communications but not
activity. Would this model the way USB and PoE work? EMON would not
specify the quantity of this power, but an EMS will know typical
levels for relevant physical layer technologies.
8.5. Collector and Aggregator
It looks like we need to extend the model by a collctor function and
an agregators function. A collector would collect energy-related
information on other devices and report for multiple of them. An
aggregator would use information from several devices and exceute
operations n them, for example calculating a sum.
8.6. Gateways and Proxies
Is a gateway rather a scenario or a function? Scenarios 9 and 16 may
need to be revised. In scenario 9 we talk about a 'proxy'. We need
to explain what we mean with 'proxy'.
9. Informative References
[I-D.quittek-power-monitoring-requirements]
Quittek, J., Winter, R., Dietz, T., Claise, B., and M.
Chandramouli, "Requirements for Power Monitoring",
draft-quittek-power-monitoring-requirements-02 (work in
progress), October 2010.
[I-D.claise-power-management-arch]
Claise, B., Parello, J., and B. Schoening, "Power
Management Architecture",
draft-claise-power-management-arch-02 (work in progress),
October 2010.
[RFC3410] Case, J., Mundy, R., Partain, D., and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410, December 2002.
[RFC4741] Enns, R., "NETCONF Configuration Protocol", RFC 4741,
December 2006.
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
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[RFC5675] Marinov, V. and J. Schoenwaelder, "Mapping Simple Network
Management Protocol (SNMP) Notifications to SYSLOG
Messages", RFC 5675, October 2009.
[IEEE-802.3af]
IEEE 802.3 Working Group, "IEEE Std 802.3af-2003 - Data
Terminal Equipment (DTE) Power via Media Dependent
Interface (MDI)", July 2003.
Authors' Addresses
Juergen Quittek
NEC Europe Ltd.
Network Research Division
Kurfuersten-Anlage 36
Heidelberg 69115
DE
Phone: +49 6221 4342-115
Email: quittek@neclab.eu
Bruce Nordman
Lawrence Berkeley National Laboratory
1 Cyclotron Road
Berkeley 94720
US
Phone: +1 510 486 7089
Email: bnordman@lbl.gov
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