Network Working Group V. Manral
Internet-Draft IPInfusion Inc.
Intended status: Informational January 2, 2011
Expires: July 4, 2011
Benchmarking Power usage of networking devices
draft-manral-bmwg-power-usage-02
Abstract
With the rapid growth of networks around the globe there is an ever
increasing need to improve the energy efficiency of devices.
Operators begining to seek more information of power consumption in
the network, have no standard mechanism to measure, report and
compare power usage of different networking equipment under different
network configuration and conditions exist.
This document provides suggestions for measuring power usage of live
networks under different traffic loads and various switch router
configuration settings. It provides a suite which can be deployed on
any networking device .
Requirements Language
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].
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 July 4, 2011.
Copyright Notice
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Challenges in defining benchmarks . . . . . . . . . . . . . . . 3
3. Factors for power consumption . . . . . . . . . . . . . . . . . 4
3.1. Network Factors affecting power consumption . . . . . . . . 5
3.2. Device Factors affecting power consumption . . . . . . . . 5
3.3. Traffic Factors affecting power consumption . . . . . . . . 6
4. Network Energy Consumption Rate (NECR) . . . . . . . . . . . . 6
5. Network Energy Proportionality Index (NEPI) . . . . . . . . . . 6
6. Benchmark details . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
Energy Efficiency is becoming increasing important in the operation
of network infrastructure. Data traffic is exploding at an
accelerated rate. Networks provide communication channels that
facilitates components of the infrastructues to exchange critical
information and are always on. On the other hand, a lot of devices
run at very low average utlization rates. Various strategies are
being defined to improve network utilization of these devices and
thus improve power consumption.
The first step to obtain a network wide view is to start with an
individual device view of the system and address different devices in
the network on a per device basis. The easiest way to measure the
power consumption of a device is to use a power meter. This can be
used to measure power under a variety of conditions affecting power
usage on a networking device.
Various techniques have been defined for energy management of
networking devices. However, there is no common strategy to actually
benchmark power utilization of networking devices like routers or
switches. This document defines the mechanism to correctly
characterize and benchmark the power consumption of various
networking devices so as to be able to correctly measure and compare
the power usage of various devices. This will enable intelligent
decisions to optimize the power consumption for individual devices
and the network as a whole. Benchmark are also required to compare
effectiveness of various energy optimization techniques.
The Network Energy Consumption Rate (NECR) as well as Network Energy
Proportionality Index (NEPI) is also defined here.
The procedures/ metrics defined in this document have been used to
perform live measurement with a variety of networking equipment from
three large well known vendors.
2. Challenges in defining benchmarks
Using the "Maximum Rated Power" and spec sheets of devices and adding
the values for all devices are of little use because the measurement
gives the maximum power that can consumed by the device, however that
does not accurately reflect the power consumed by the device under a
normal work load. Typical energy requirements of a networking device
are dependent on device configuration and traffic.
The ratio of the actual power consumed by the device on an average,
to its maximum rated power varies widely across different device
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families. Thus, relying merely on the maximum rated power can
grossly overestimate the total energy consumed by networking
equipment.
There are a wide variety of networking equipment and finding a
general benchmark to work across a variety of devices, requires a lot
of flexibility in benchmarking methodology. the workload and test
conditions will also depend on the kind of device.
A network device consists of a lot of individual component, each of
which consume power. For example, only considering the power
consumption of the CPU/ data forwarding ASIC we may ignore the power
consumption of the other components like external memory.
Power instrumentation of a device in a live network involves
unplugging the device and plugging it into a power meter. This can
inturn lead to traffic loss. Unfortunately, most current equipment
is not equipped with internal instrumentation to report power usage
of the device or its components. It is for this reason the power
measurement is done on an individual device under different network
conditions using a traffic generator.
The network devices can also dissipate significant heat. Past
studies have shown dissipation rations of 2.5. Which means if the
power in is 2.5 Watt, only 1 Watt is used for actual work, the rest
is disspated as heat. This heating can lead to more power consumed
by fan/ compressor for cooling the devices. Though this methodology
does not measure the power consumed by external cooling
infrastructure, it measures the power consumed internally. It also
(optionally) measures the temperature change of the device which can
be correlated to the amount of external power consumed to cool the
device.
The amount of power used at startup can be more than the average
power usage of the device. This is also measured as part of the test
methodology.
3. Factors for power consumption
The metrics defined here will help operators get a more accurate idea
of power consumed by network equipment and hence forecast their power
budget. These will also help device vendors test and compare the new
power efficiency enhancements on various devices.
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3.1. Network Factors affecting power consumption
The first and the most important factor from the network perspective
which can determine the power consumption is the traffic load.
Benchmarks must be performed with different traffic loads in the
network.
There are now various kinds of transcivers/ connectors on a network
device. For the same bandwidth the power usage of a device depends
on the kind of connector used. The connector/ interface type used
needs to be specified in the benchmark.
The length of the cable used also defines the amount of power
consumed by the system. Benchmarks should specify the cable length
used. For example, a 5 meter cable can be used wherever possible.
3.2. Device Factors affecting power consumption
Base Chassis Power - typically, higher end network devices come with
a chassis and card slots. Each slot may have a number of ports. For
the lower end devices there are no removable card slots. In both
these cases the base chassis power consists of processors, fans,
memory, etc.
Number of line cards - In switches that support inserting linecards,
there is a limit on the number of ports per linecard as well as the
aggregate bandwidth that each linecard can accommodate. This
mechanism allows network operators the flexibility to only plug in as
many linecards as they need. For each benchmark the total number of
line cards plugged into the system needs to be specified.
Number of active ports - This term refers to the total number of
ports on the switch (across all the linecards) that are active (with
cables plugged in). The remaining ports on the switch are explicitly
disabled using the switchs command line interface. For each
benchmark the number of active and passive ports must be specified.
Port settings - Setting this parameter limits the line rate
forwarding capacity of individual ports. For each benchmark the port
configuration and settings need to be specified.
Port Utilization - This term describes the actual throughput flowing
through a port relative to its specified capacity. For each
benchmark the port utilization of each port must be specified. The
actual traffic can use the information defined in RFC 2544 [RFC2544].
TCAM - Network vendors typically implement packet classification in
hardware. TCAMs are supported by most vendors as they have very fast
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look-up times. However, they are are notoriously power-hungry. The
size of the TCAM in a switch is widely variable. The size of the
TCAM needs to be reported in the benchmark document. The number of
TCAM entries does not affect power consumption.
Firmware - Vendors periodically release upgraded versions of their
switch/router firmware. Different versions of firmware may also
impact the device power consumption. The firmware version needs to
be reported in the benchmark document. Different firmware versions
have resulted in different power usage.
3.3. Traffic Factors affecting power consumption
Packet Size - Different packet sizes typically do not effect power
consumption.
Inter-Packet Delay - time between successive packets may affect power
usage but we do not measure the effects in detail.
CPU traffic - Percentage of CPU traffic. For our benchmarks we can
assume different values of CPU bound traffic. The different
percentage of CPU bound traffic must be specified in the benchmark.
4. Network Energy Consumption Rate (NECR)
To optimize the run time energy usage for different devices, the
additional energy consumption that will result as a factor of
additional traffic needs to be known. The NECR defines the power
usage increase in MilliWatts per Mbps of data at the physical layer.
The NECR will depend on the line card, the port and the other factors
defined earlier.
For the effective use of the NECR the base power of the chassis, a
line card and a port needs to be specified when there is no load.
The measurements must take into consideration power optimization
techniques when there is no traffic on any port of a line card.
5. Network Energy Proportionality Index (NEPI)
In the ideal case the power consumed by a device is proportional to
its network load. The average difference between the ideal(I) and
the measured (M) power consumption defines the EPI.
The ideal power is measured by assuming the power consumed by a
device at 100% traffic load and using that to derive the ideal power
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usage for different traffic loads.
EPIx = (Mx - Ix)/ Mx * 100
EPI = EPI1 + EPI2 + ....... EPIn / n
The EPI is independent of the actualy traffic load. It can thus be
used to define the energy efficiency of a networking device. A value
of 0 means the power usage is agnostic to traffic and a value of 100
means that the device has perfect energy proportionality.
6. Benchmark details
All power measurements are done in MilliWatts, except NECR which is
done in MilliWatts/ Mbps.
7. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
8. Security Considerations
This document raises no new security issues.
9. Acknowledgements
This document derives a lot of its text and content from "A Power
Benchmarking Framework for Network Devices" paper and the authors of
that are duly acknowledged.
The author would like to thank Srini Seetharaman
(srini.seetharaman@telekom.com) and Priya Mahadevan
(priya.mahadevan@hp.com) for their support with the draft. The
author would also like to thank Al Morton (AT&T) and Robert
Peglar(XioTech) for his careful reading and suggestions on the draft.
10. References
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10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
Author's Address
Vishwas Manral (editor)
IPInfusion Inc.
1188 E. Arques Ave.
Sunnyvale, CA 94085
US
Phone: 408-400-1900
Email: vishwas@ipinfusion.com
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