Internet DRAFT - draft-nordman-power-locator
draft-nordman-power-locator
Network Working Group B. Nordman
Internet-Draft S. Lanzisera
Intended status: Standards Track Lawrence Berkeley National
Expires: April 26, 2012 Laboratory
October 24, 2011
Power Locator
draft-nordman-power-locator-00
Abstract
This specification addresses how to request that a device should
enter a "power locator" mode for a limited period of time. The mode
involves a device cycling between a low and high power level in a
predictable manner so that a power metering device upstream in the
power distribution system can sense the signal and so determine where
the device draws its power from. This will be useful in many types
of buildings, particularly data centers and large commercial
buildings. This draft addresses operation of the device carrying out
the request, but not detailed operation of the device that makes the
request and interprets the results.
This draft is an initial discussion document to generate feedback and
improvement.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 26, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
Nordman & Lanzisera Expires April 26, 2012 [Page 1]
Internet-Draft Power Locator October 2011
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. Overview
Management of energy use in buildings is often impeded by not knowing
basic information about where the energy is used and for what
purpose. The quantity of electricity used is being addressed by the
Energy Management Working Group, but there is no existing mechanism
to help identify where in a power distribution tree a particular
device is located. In data centers, Power Distribution Units
commonly have metering capability for each individual outlet.
Metering for commercial buildings is becoming less expensive each
year, so that measurement of entire electrical panels, or individual
circuits, is increasingly common.
As metering within buildings becomes more sophisticated, it is
important to know what devices are on each metered circuit. While
this can be entered into a management system manually (if known), an
automated solution would be much less costly, more reliable, and much
easier to keep current.
Many devices and components can modulate their own power use
dynamically. For example, processors can be sped up or slowed down;
disks can be spun up or spun down; displays can be made brighter or
dimmer (or even not lit at all); heaters in a printer can be engaged
or disengaged; fans can be turned on or off, etc. These changes
normally occur for functional purposes, with components powered up as
needed, and down when not, to save energy or reduce thermal burdens.
However, they can be engaged for other purposes; in this case, to
create a very low bit rate signal on the power line.
This mechanism is cleanest if the device in question is otherwise
completely idle, but can still be usefully invoked if it is engaging
in modest, random utilization that induces power levels above the
normal idle level.
This draft describes a simple mechanism to aid device location for
any device that has the ability to modulate its own power consumption
on a timely basis.
Nordman & Lanzisera Expires April 26, 2012 [Page 2]
Internet-Draft Power Locator October 2011
The scope of this draft is any entity which is reachable via SNMP.
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].
2.1. Theory of Operation
This mechanism covers a building which has a management system (MS),
meters, and individual devices. The devices can receive power
locator requests.
2.1.1. Devices
Devices that support this mechanism recieve an SNMP request, and if
granted, alter their behavior for a specified period of time.
2.1.2. Meters
Meters may measure power for an individual outlet, an individual
circuit breaker, or an entire section of a building. That is, they
may power one device, or many. The meter reports power or energy
data to the MS on a known fixed periodic basis.
2.1.3. Management System
The management system has the ability to identify devices that are or
may be in the target building, has access to the data reported by
meters in the building, and can send power locator requests to
individual devices.
2.1.4. Request
The SNMP request is accomplished by a SET of each of the following
values:
Bitmap: A 8 byte value for which each 1 bit indicates that the
device should maximize power and each 0 bit indicates that it
should minimize it.
Length: A one byte value which indicated the length of the bitmap;
may be in the range 2..64.
Nordman & Lanzisera Expires April 26, 2012 [Page 3]
Internet-Draft Power Locator October 2011
Period: A [ 3 / 4 ] byte value indicating the length of time of each
bit period, measured in [ milliseconds / microseconds ].
Duration: The number of periods for the entire test. The Duration
value can be read to track the progress of the test, as the device
will decrement it as the periods pass. When the test is complete,
duration is zero. If the device refuses to grant the test
request, then the duration is set immediately to zero. If the
request is granted, the activity begins immediately.
2.1.5. Reporting
The device may return any of the data items above via in SNMP GET.
The following are also available:
PowerDelta: A value which indicates the estimated difference between
the minimum and maximum power levels, measured in milliwatts.
This is read-only.
Duration: As above, this counts down to zero over the course of the
test.
3. Discussion
A management system has access to data from a series of meters that
measure discrete portions of the electricity distribution system in a
building. It also has access to a list of IP addresses that may
correspond to devices in the building. Usually a subnet will cover a
building (or portion thereof) and so all addresses in the subnet can
be queried. Alternatively, the router can be queried for all
addresses it knows of, etc.
The management system will direct one or more devices to modulate
their power with a Period value typically twice the length of each
meter reading period. This ensures that every other reading will
reflect only a maximum or minimum for the target device (the
intermediate readings will be some combination of adjacent periods).
If timing of devices and meters can be aligned, then devices may have
a Period value equal to the meter reading period.
The simplest bitmap would be simply "01" so that the device would
alternate between low and high on a fixed period. However, more
complex patterns will provide a better signal, particularly in the
face of periodic ordinary consumption. In addition, complex patterns
facilitate searching for multiple devices at the same time.
Once a device is in its modulation mode, the management system will
scan data from each meter to try to find which meter the signal is
visible on. The signal processing algorithm(s) used by management
Nordman & Lanzisera Expires April 26, 2012 [Page 4]
Internet-Draft Power Locator October 2011
systems are outside the scope of this draft. Once the device is
localized to a particular meter, the management system may set the
duration value to zero to terminate the test, or may simply let it
run its course. If the device cannot be located, the test can be re-
run.
A management system may periodically re-run the test to track any
devices that have moved. The type of device may inform how often the
test is re-run.
For devices with internal batteries, there is the possibility of
going to battery-only mode for low-power, and to battery charging for
high power? This would make the delta much larger for something like
a notebook.
This draft does not address how a device could or should modulate its
power use.
4. Open Issues
SNMP uses a series of SETs. I assume that the various values should
be set with the duration being the last one. The duration will count
down to zero during the course of operation. Is this the right way
to use SNMP for this purpose?
Should Period be measured in milliseconds or microseconds? Four
bytes at 1ms is a really long time; three bytes is odd. Options seem
to be milliseconds at 3B or 4B, or microseconds at 4B. Note that one
AC cycle is 17 or 20 ms long (60 Hz and 50 Hz), so presumably no
value less than this would be used, at least for AC power
distribution. The microsecond case would be the same but a higher
starting value. Should there be a aximum value for "Period"?
Should any facility be provided for an IP device to proxy this
ability for a non-IP device? (Probably not) .
How about devices with multiple power supplies? Generally the signal
will show up on both meters (if they are fed by different meters).
If the device has the ability to shut off all but one supply, then
each could be located separately, but this draft does not consider
how to signal that behavior.
SNMP is convenient, but alternative protocols could also be used.
Are there any particularly suited to this?
Should there be an explicit error variable? In addition to the
device rejecting the request, it may be or become disconnected from
Nordman & Lanzisera Expires April 26, 2012 [Page 5]
Internet-Draft Power Locator October 2011
mains power distribution (e.g. a notebook running on battery).
Is "test" the right word to use?
5. Security Considerations
This mechanism introduces no information security vulnerabilities.
It does create the possibility of limited extra energy use when
invoked. Invoking this mechanism on a large number of devices in
synchrony could introduce instability into the local power
distribution system.
6. Privacy Considerations
TBD
7. Acknowledgement
We would like to thank <get your name here>.
8. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Bruce Nordman
Lawrence Berkeley National Laboratory
1 Cyclotron Road
Berkeley, CA 94720
USA
Email: BNordman@LBL.gov
Nordman & Lanzisera Expires April 26, 2012 [Page 6]
Internet-Draft Power Locator October 2011
Steven Lanzisera
Lawrence Berkeley National Laboratory
1 Cyclotron Road
Berkeley, CA 94720
USA
Email: SMLanzisera@LBL.gov
Nordman & Lanzisera Expires April 26, 2012 [Page 7]
