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



   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",
   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

   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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   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

   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

   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

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

   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

   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

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
   ( and Priya Mahadevan
   ( 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

   Phone: 408-400-1900

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