





Internet Engineering Task Force (IETF)                        S. Bradner
Request for Comments: 6815                            Harvard University
Updates: 2544                                                  K. Dubray
Category: Informational                                 Juniper Networks
ISSN: 2070-1721                                               J. McQuaid
                                                            Turnip Video
                                                               A. Morton
                                                               AT&T Labs
                                                           November 2012


                 Applicability Statement for RFC 2544:
             Use on Production Networks Considered Harmful

Abstract

   The Benchmarking Methodology Working Group (BMWG) has been developing
   key performance metrics and laboratory test methods since 1990, and
   continues this work at present.  The methods described in RFC 2544
   are intended to generate traffic that overloads network device
   resources in order to assess their capacity.  Overload of shared
   resources would likely be harmful to user traffic performance on a
   production network, and there are further negative consequences
   identified with production application of the methods.  This memo
   clarifies the scope of RFC 2544 and other IETF BMWG benchmarking work
   for isolated test environments only, and it encourages new standards
   activity for measurement methods applicable outside that scope.

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/rfc6815.








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Copyright Notice

   Copyright (c) 2012 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
   (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.

Table of Contents

   1. Introduction ....................................................3
      1.1. Requirements Language ......................................4
   2. Scope and Goals .................................................4
   3. The Concept of an Isolated Test Environment .....................4
   4. Why the Methods of RFC 2544 Are Intended Only for ITE ...........4
      4.1. Experimental Control and Accuracy ..........................4
      4.2. Containing Damage ..........................................5
   5. Advisory on RFC 2544 Methods in Production Networks .............5
   6. Considering Performance Testing in Production Networks ..........6
   7. Security Considerations .........................................7
   8. Acknowledgements ................................................7
   9. References ......................................................8
      9.1. Normative References .......................................8
      9.2. Informative References .....................................8
   Appendix A. Example of RFC 2544 Method Failure in Production
               Network Measurement ....................................9


















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1.  Introduction

   This memo clarifies the scope and use of IETF Benchmarking
   Methodology Working Group (BMWG) tests including [RFC2544], which
   discusses and defines several tests that may be used to characterize
   the performance of a network interconnecting device.  All readers of
   this memo must read and fully understand [RFC2544].

   Benchmarking methodologies (beginning with [RFC2544]) have always
   relied on test conditions that can only be produced and replicated
   reliably in the laboratory.  These methodologies are not appropriate
   for inclusion in wider specifications such as:

   1.  Validation of telecommunication service configuration, such as
       the Committed Information Rate (CIR).

   2.  Validation of performance metrics in a telecommunication Service
       Level Agreement (SLA), such as frame loss and latency.

   3.  Telecommunication service activation testing, where traffic that
       shares network resources with the test might be adversely
       affected.

   Above, we distinguish "telecommunication service" (where a network
   service provider contracts with a customer to transfer information
   between specified interfaces at different geographic locations) from
   the generic term "service".  Below, we use the adjective "production"
   to refer to networks carrying live user traffic.  [RFC2544] used the
   term "real-world" to refer to production networks and to
   differentiate them from test networks.

   Although [RFC2544] has been held up as the standard reference for the
   testing listed above, we believe that the actual methods used vary
   from [RFC2544] in significant ways.  Since the only citation is to
   [RFC2544], the modifications are opaque to the standards community
   and to users in general.

   Since applying the test traffic and methods described in [RFC2544] on
   a production network risks causing overload in shared resources,
   there is direct risk of harming user traffic if the methods are
   misused in this way.  Therefore, the IETF BMWG developed this
   Applicability Statement for [RFC2544] to directly address the
   situation.








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1.1.  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].

2.  Scope and Goals

   This memo clarifies the scope of [RFC2544] with the goal of providing
   guidance to the industry on its applicability, which is limited to
   laboratory testing.

3.  The Concept of an Isolated Test Environment

   An Isolated Test Environment (ITE) used with the methods of [RFC2544]
   (as illustrated in Figures 1 through 3 of [RFC2544]) has the ability
   to:

   o  contain the test streams to paths within the desired setup

   o  prevent non-test traffic from traversing the test setup

   These features allow unfettered experimentation, while at the same
   time protecting lab equipment management/control LANs and other
   production networks from the unwanted effects of the test traffic.

4.  Why the Methods of RFC 2544 Are Intended Only for ITE

   The following sections discuss some of the reasons why [RFC2544]
   methods are applicable only for isolated laboratory use, and the
   consequences of applying these methods outside the lab environment.

4.1.  Experimental Control and Accuracy

   All of the tests described in RFC 2544 require that the tester and
   device under test are the only devices on the networks that are
   transmitting data.  The presence of other traffic (unwanted on the
   ITE network) would mean that the specified test conditions have not
   been achieved and flawed results are a likely consequence.

   If any other traffic appears and the amount varies over time, the
   repeatability of any test result will likely depend to some degree on
   the amount and variation of the other traffic.

   The presence of other traffic makes accurate, repeatable, and
   consistent measurements of the performance of the device under test
   very unlikely, since the complete details of test conditions will not
   be reported.



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   For example, the RFC 2544 Throughput Test attempts to characterize a
   maximum reliable load; thus, there will be testing above the maximum
   that causes packet/frame loss.  Any other sources of traffic on the
   network will cause packet loss to occur at a tester data rate lower
   than the rate that would be achieved without the extra traffic.

4.2.  Containing Damage

   [RFC2544] methods, specifically to determine Throughput as defined in
   [RFC1242] and other benchmarks, may overload the resources of the
   device under test, and they may cause failure modes in the device
   under test.  Since failures can become the root cause of more
   widespread failure, it is clearly desirable to contain all test
   traffic within the ITE.

   In addition, such testing can have a negative effect on any traffic
   that shares resources with the test stream(s) since, in most cases,
   the traffic load will be close to the capacity of the network links.

   Appendix C.2.2 of [RFC2544] (as adjusted by errata) gives the private
   IPv4 address range for testing:

   "...The network addresses 198.18.0.0 through 198.19.255.255 have been
   assigned to the BMWG by the IANA for this purpose.  This assignment
   was made to minimize the chance of conflict in case a testing device
   were to be accidentally connected to part of the Internet.  The
   specific use of the addresses is detailed below."

   In other words, devices operating on the Internet may be configured
   to discard any traffic they observe in this address range, as it is
   intended for laboratory ITE use only.  Thus, if testers using the
   assigned testing address ranges are connected to the Internet and
   test packets are forwarded across the Internet, it is likely that the
   packets will be discarded and the test will not work.

   We note that a range of IPv6 addresses has been assigned to BMWG for
   laboratory test purposes, in [RFC5180] (as amended by errata).

   See the Security Considerations section below for further
   considerations on containing damage.

5.  Advisory on RFC 2544 Methods in Production Networks

   The tests in [RFC2544] were designed to measure the performance of
   network devices, not of networks, and certainly not production
   networks carrying user traffic on shared resources.  There will be
   undesirable consequences when applying these methods outside the
   isolated test environment.



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   One negative consequence stems from reliance on frame loss as an
   indicator of resource exhaustion in [RFC2544] methods.  In practice,
   link-layer and physical-layer errors prevent production networks from
   operating loss-free.  The [RFC2544] methods will not correctly assess
   Throughput when loss from uncontrolled sources is present.  Frame
   loss occurring at the SLA levels of some networks could affect every
   iteration of Throughput testing (when each step includes sufficient
   packets to experience facility-related loss).  Flawed results waste
   the time and resources of the testing service user and of the service
   provider when called to dispute the measurement.  These are
   additional examples of harm that compliance with this advisory should
   help to avoid.  See Appendix A for an example.

   The methods described in [RFC2544] are intended to generate traffic
   that overloads network device resources in order to assess their
   capacity.  Overload of shared resources would likely be harmful to
   user traffic performance on a production network.  These tests MUST
   NOT be used on production networks and as discussed above.  The tests
   will not produce a reliable or accurate benchmarking result on a
   production network.

   [RFC2544] methods have never been validated on a network path, even
   when that path is not part of a production network and carrying no
   other traffic.  It is unknown whether the tests can be used to
   measure valid and reliable performance of a multi-device, multi-
   network path.  It is possible that some of the tests may prove valid
   in some path scenarios, but that work has not been done or has not
   been shared with the IETF community.  Thus, such testing is
   contraindicated by the BMWG.

6.  Considering Performance Testing in Production Networks

   The IETF has addressed the problem of production network performance
   measurement by chartering a different working group: IP Performance
   Metrics (IPPM).  This working group has developed a set of standard
   metrics to assess the quality, performance, and reliability of
   Internet packet transfer services.  These metrics can be measured by
   network operators, end users, or independent testing groups.  We note
   that some IPPM metrics differ from RFC 2544 metrics with similar
   names, and there is likely to be confusion if the details are
   ignored.

   IPPM has not yet standardized methods for raw capacity measurement of
   Internet paths.  Such testing needs to adequately consider the strong
   possibility for degradation to any other traffic that may be present
   due to congestion.  There are no specific methods proposed for
   activation of a packet transfer service in IPPM at this time.  Thus,
   individuals who need to conduct capacity tests on production networks



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   should actively participate in standards development to ensure their
   methods receive appropriate industry review and agreement, in the
   IETF or in alternate standards development organizations.

   Other standards may help to fill gaps in telecommunication service
   testing.  For example, the IETF has many standards intended to assist
   with network Operations, Administration, and Maintenance (OAM).
   ITU-T Study Group 12 has a Recommendation on service activation test
   methodology [Y.1564].

   The world will not spin off axis while waiting for appropriate and
   standardized methods to emerge from the consensus process.

7.  Security Considerations

   This Applicability Statement intends to help preserve the security of
   the Internet by clarifying that the scope of [RFC2544] and other BMWG
   memos are all limited to testing in a laboratory ITE, thus avoiding
   accidental Denial-of-Service attacks or congestion due to high
   traffic volume test streams.

   All benchmarking activities are limited to technology
   characterization using controlled stimuli in a laboratory
   environment, with dedicated address space and the other constraints
   [RFC2544].

   The benchmarking network topology will be an independent test setup
   and MUST NOT be connected to devices that may forward the test
   traffic into a production network or misroute traffic to the test
   management network.

   Further, benchmarking is performed on a "black-box" basis, relying
   solely on measurements observable external to the device under test/
   system under test (DUT/SUT).

   Special capabilities SHOULD NOT exist in the DUT/SUT specifically for
   benchmarking purposes.  Any implications for network security arising
   from the DUT/SUT SHOULD be identical in the lab and in production
   networks.

8.  Acknowledgements

   Thanks to Matt Zekauskas, Bill Cerveny, Barry Constantine, Curtis
   Villamizar, David Newman, and Adrian Farrel for suggesting
   improvements to this memo.






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   Specifically, Al Morton would like to thank his coauthors, who
   constitute the complete set of Chairmen-Emeritus of the BMWG, for
   returning from other pursuits to develop this statement and see it
   through to approval.  This has been a rare privilege; one that likely
   will not be matched in the IETF again:

      Scott Bradner   served as Chairman from 1990 to 1993
      Jim McQuaid     served as Chairman from 1993 to 1995
      Kevin Dubray    served as Chairman from 1995 to 2006

   It's all about the band.

9.  References

9.1.  Normative References

   [RFC1242]  Bradner, S., "Benchmarking terminology for network
              interconnection devices", RFC 1242, July 1991.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544, March 1999.

   [RFC5180]  Popoviciu, C., Hamza, A., Van de Velde, G., and D.
              Dugatkin, "IPv6 Benchmarking Methodology for Network
              Interconnect Devices", RFC 5180, May 2008.

9.2.  Informative References

   [Bryant]   Bonica, R. and S. Bryant, "RFC2544 Testing in Production
              Network", Work in Progress, October 2012.

   [Y.1564]   ITU-T Recommendation Y.1564, "Ethernet Service Activation
              Test Methodology", March 2011.















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Appendix A.  Example of RFC 2544 Method Failure in Production Network
             Measurement

   This Appendix provides an example illustrating how [RFC2544] methods
   applied on production networks can easily produce a form of harm from
   flawed and misleading results.

   The [RFC2544] Throughput benchmarking method usually includes the
   following steps:

   a.  Set the offered traffic level, less than max of the ingress
       link(s).

   b.  Send the test traffic through the device under test (DUT) and
       count all frames successfully transferred.

   c.  If all frames are received, increment traffic level and repeat
       step b.

   d.  If one or more frames are lost, the level is in the DUT-overload
       region (step b may be repeated at a reduced traffic level to more
       exactly determine the maximum rate at which none of the frames
       are dropped by the DUT, defined as the Throughput [RFC1242]).

   e.  Report the Throughput values, the x-y of graph of frame size and
       Throughput, and other information in accordance with [RFC2544].

   In this method, frame loss is the sole indicator of overload and
   therefore the determining factor in the measurement of Throughput
   using the [RFC2544] methodology (even though the results may not
   report frame loss per se).

   Frame loss is subject to many factors in addition to operating above
   the Throughput traffic level.  These factors include optical
   interference (which may be due to dirty interfaces, crossover from
   other signals, fiber bend and temperature, etc.) and electrical
   interference (caused by local sources of radio signals, electrical
   spikes, solar particles, etc.).  In the laboratory environment many
   of these issues can be carefully controlled through cleaning and
   isolation.  Since [RFC2544] methodologies are primarily intended to
   test devices and not paths, the total length of path, the number of
   interfaces, and compound risk of random frame loss can be kept to a
   minimum.

   In a production network, however, there will be many interfaces and
   many kilometers of path under test.  This considerably increases the
   risk of random frame loss.




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   The risk of frame loss caused by outside effects is significantly
   higher in production networks, and significantly higher with long
   paths (both those with long physical path lengths, and those with
   large numbers of interfaces in the path).  Thus, the risk of falsely
   low reported Throughput using an [RFC2544] methodology test is
   considerably increased in a production network.

   Therefore, to successfully conduct tests with similar objectives to
   those in [RFC2544] in a production network, it will be necessary to
   develop modifications to the methodologies defined in [RFC2544] and
   standards to describe them.  See [Bryant] for an in-progress effort
   and [Y.1564] for an approved method adapted to production service
   activation.






































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Authors' Addresses

   Scott Bradner
   Harvard University
   1350 Mass. Ave., Room 760
   Cambridge, MA  02138
   USA

   Phone: +1 617 495 3864
   EMail: sob@harvard.edu
   URI:   http://www.sobco.com


   Kevin Dubray
   Juniper Networks


   Jim McQuaid
   Turnip Video
   6 Cobbleridge Court
   Durham, North Carolina  27713
   USA

   Phone: +1 919-619-3220
   EMail: jim@turnipvideo.com
   URI:   www.turnipvideo.com


   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown,, NJ  07748
   USA

   Phone: +1 732 420 1571
   Fax:   +1 732 368 1192
   EMail: acmorton@att.com
   URI:   http://home.comcast.net/~acmacm/













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