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RFC 2544 Applicability Statement: Use on Production Networks Considered Harmful
draft-ietf-bmwg-2544-as-02

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This is an older version of an Internet-Draft that was ultimately published as RFC 6815.
Authors Scott O. Bradner , Kevin Dubray , Jim McQuaid , Al Morton
Last updated 2012-04-25 (Latest revision 2012-03-12)
Replaces draft-chairs-bmwg-2544-as
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draft-ietf-bmwg-2544-as-02
Network Working Group                                         S. Bradner
Internet-Draft                                        Harvard University
Intended status: Informational                                 K. Dubray
Expires: September 13, 2012                             Juniper Networks
                                                              J. McQuaid
                                                            Turnip Video
                                                               A. Morton
                                                               AT&T Labs
                                                          March 12, 2012

RFC 2544 Applicability Statement: Use on Production Networks Considered
                                Harmful
                       draft-ietf-bmwg-2544-as-02

Abstract

   Benchmarking Methodology Working Group (BMWG) has been developing key
   performance metrics and laboratory test methods since 1990, and
   continues this work at present.  Recent application of the methods
   beyond their intended scope is cause for concern.  This memo
   clarifies the scope of RFC 2544 and other benchmarking work for the
   IETF community.

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 September 13, 2012.

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

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   (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 . . . . . . . . . . . . . . . . . . . 3
   2.  Scope and Goals . . . . . . . . . . . . . . . . . . . . . . . . 4
   3.  The Concept of an Isolated Test Environment . . . . . . . . . . 4
   4.  Why RFC 2544 Methods are intended for ITE . . . . . . . . . . . 4
     4.1.  Experimental Control, Repeatability, and Accuracy . . . . . 4
     4.2.  Containment of Implementation Failure Impact  . . . . . . . 5
   5.  Advisory on RFC 2544 Methods in Real-world Networks . . . . . . 5
   6.  What to do without RFC 2544?  . . . . . . . . . . . . . . . . . 6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 7
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

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1.  Introduction

   This memo clarifies the scope of RFC 2544 [RFC2544], and other
   benchmarking work for the IETF community.

   Benchmarking Methodologies (beginning with [RFC2544]) have always
   relied on test conditions that can only be produced and replicated
   reliably in the laboratory.  Thus it was surprising to find that this
   foundation methodology was being cited in several unintended
   applications, 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.  As an integral part of 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".  Also, 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 RFC 2544 is held up as the standard reference for such
   testing, we believe that the actual methods used vary from RFC 2544
   in significant ways.  Since the only citation is to RFC 2544, the
   modifications are opaque to the standards community and to users in
   general (an undesirable situation).

   To directly address this situation, the past and present Chairs of
   the IETF Benchmarking Methodology Working Group (BMWG) have prepared
   this Applicability Statement for RFC 2544.

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].

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2.  Scope and Goals

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

3.  The Concept of an Isolated Test Environment

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

   o  contain the test streams to paths within the desired set-up

   o  prevent non-test traffic from traversing the test set-up

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

4.  Why RFC 2544 Methods are intended for ITE

   The following sections discuss some of the reasons why RFC 2544
   [RFC2544] methods were intended only for isolated laboratory use, and
   the difficulties of applying these methods outside the lab
   environment.

4.1.  Experimental Control, Repeatability, and Accuracy

   All of the tests described in RFC 2544 assume that the tester and
   device under test are the only devices on the networks that are
   transmitting data.  The presence of other unwanted traffic on the
   network would mean that the specified test conditions have not been
   achieved.

   Assuming that the unwanted traffic appears in variable amounts over
   time, the repeatability of any test result will likely depend to some
   degree on the unwanted traffic.

   The presence of unwanted or unknown traffic makes accurate,
   repeatable, and consistent measurements of the performance of the
   device under test very unlikely, since the actual test conditions
   will not be reported.

   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

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   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.  Containment of Implementation Failure Impact

   RFC 2544 methods, specifically to determine Throughput as defined in
   [RFC1242] and other benchmarks, may overload the resources of the
   device under test, and may cause failure modes in the device under
   test.  Since failures can become the root cause of more wide-spread
   failure, it is clearly desirable to contain all test traffic within
   the ITE.

   In addition, such testing can have a negative affect on any traffic
   which 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.&", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Protocol Updates

   Discarding the NCE after three packets spaced one second apart is
   only needed when an alternative neighbor is available, such as an
   additional default router or discarding an NCE created by a Redirect.

   If an implementation transmits more than MAX_UNICAST_SOLICIT/
   MAX_MULTICAST_SOLICIT packets, then it SHOULD use the exponential
   backoff of the retransmit timer.  This is to avoid any significant
   load due to a steady background level of retransmissions from
   implementations that retransmit a large number of Neighbor
   Solicitations (NS) before discarding the NCE.

   Even if there is no alternative neighbor, the protocol needs to be
   able to handle the case when the link-layer address of the neighbor/
   target has changed by switching to multicast Neighbor Solicitations
   at some point in time.

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   In order to capture all the cases above, this document introduces a
   new UNREACHABLE state in the conceptual model described in [RFC4861].
   An NCE in the UNREACHABLE state retains the link-layer address, and
   IPv6 packets continue to be sent to that link-layer address.  But in
   the UNREACHABLE state, the NUD Neighbor Solicitations are multicast
   (to the solicited-node multicast address), using a timeout that
   follows an exponential backoff.

   In the places where [RFC4861] says to discard/delete the NCE after N
   probes (Sections 7.3 and 7.3.3, and Appendix C), this document
   instead specifies a transition to the UNREACHABLE state.

   If the Neighbor Cache Entry was created by a Redirect message, a node
   MAY delete the NCE instead of changing its state to UNREACHABLE.  In
   any case, the node SHOULD NOT use an NCE created by a Redirect to
   send packets if that NCE is in the UNREACHABLE state.  Packets should
   be sent following the next-hop selection algorithm in [RFC4861],
   Section 5.2, which disregards NCEs that are not reachable.

   Section 6.3.6 of [RFC4861] indicates that default routers that are
   "known to be reachable" are preferred.  For the purposes of that
   section, if the NCE for the router is in the UNREACHABLE state, it is
   not known to be reachable.  Thus, the particular text in
   Section 6.3.6 that says "in any state other than INCOMPLETE" needs to
   be extended to say "in any state other than INCOMPLETE or
   UNREACHABLE".

   Apart from the use of multicast NS instead of unicast NS, and the
   exponential backoff of the timer, the UNREACHABLE state works the
   same as the current PROBE state.

   A node MAY garbage collect a Neighbor Cache Entry at any time as
   specified in [RFC4861].  This freedom to garbage collect does not
   change with the introduction of the UNREACHABLE state in the
   conceptual model.  An implementation MAY prefer garbage collecting
   UNREACHABLE NCEs over other NCEs.

   There is a non-obvious extension to the state-machine description in
   Appendix C of [RFC4861] in the case for "NA, Solicited=1, Override=0.
   Different link-layer address than cached".  There we need to add
   "UNREACHABLE" to the current list of "STALE, PROBE, Or DELAY".  That
   is, the NCE would be unchanged.  Note that there is no corresponding
   change necessary to the text in [RFC4861], Section 7.2.5, since it is
   phrased using "Otherwise" instead of explicitly listing the three
   states.

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   The other state transitions described in Appendix C handle the
   introduction of the UNREACHABLE state without any change, since they
   are described using "not INCOMPLETE".

   There is also the more obvious change already described above.
   [RFC4861] has this:

   State           Event                   Action             New state

   PROBE           Retransmit timeout,     Discard entry         -
                   N or more
                   retransmissions.

   That needs to be replaced by:

   State           Event                   Action             New state

   PROBE           Retransmit timeout,     Increase timeout  UNREACHABLE
                   N retransmissions.      Send multicast NS

   UNREACHABLE     Retransmit timeout      Increase timeout  UNREACHABLE
                                           Send multicast NS

   The exponential backoff SHOULD be clamped at some reasonable maximum
   retransmit timeout, such as 60 seconds (see MAX_RETRANS_TIMER below).
   If there is no IPv6 packet sent using the UNREACHABLE NCE, then it is
   RECOMMENDED to stop the retransmits of the multicast NS until either
   the NCE is garbage collected or there are IPv6 packets sent using the
   NCE.  The multicast NS and associated exponential backoff can be
   applied on the condition of continued use of the NCE to send IPv6
   packets to the recorded link-layer address.

   A node can unicast the first few Neighbor Solicitation messages even
   while in the UNREACHABLE state, but it MUST switch to multicast
   Neighbor Solicitations within 60 seconds of the initial
   retransmission to be able to handle a link-layer address change for
   the target.  The example below shows such behavior.

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4.  Example Algorithm

   This section is NOT normative but specifies a simple implementation
   that conforms with this document.  The implementation is described
   using operator-configurable values that allow it to be configured to
   be compatible with the retransmission behavior in [RFC4861].  The
   operator can configure the values for MAX_UNICAST_SOLICIT,
   MAX_MULTICAST_SOLICIT, RETRANS_TIMER, and the new BACKOFF_MULTIPLE,
   MAX_RETRANS_TIMER, and MARK_UNREACHABLE.  This allows the
   implementation to be as simple as:

   next_retrans = ($BACKOFF_MULTIPLE ^ $solicit_retrans_num) *
   $RetransTimer * $JitterFactor where solicit_retrans_num is zero for
   the first transmission, and JitterFactor is a random value between
   MIN_RANDOM_FACTOR and MAX_RANDOM_FACTOR [RFC4861] to avoid any
   synchronization of transmissions from different hosts.

   After MARK_UNREACHABLE transmissions, the implementation would mark
   the NCE UNREACHABLE and as a result explore alternate next hops.
   After MAX_UNICAST_SOLICIT, the implementation would switch to
   multicast NUD probes.

   The behavior of this example algorithm is to have 5 attempts, with
   time spacing of 0 (initial request), 1 second later, 3 seconds after
   the first retransmission, then 9, then 27, and switch to UNREACHABLE
   after the first three transmissions.  Thus, relative to the time of
   the first transmissions, the retransmissions would occur at 1 second,
   4 seconds, 13 seconds, and finally 40 seconds.  At 4 seconds from the
   first transmission, the NCE would be marked UNREACHABLE.  That
   behavior corresponds to:

      MAX_UNICAST_SOLICIT=5

      RETRANS_TIMER=1 (default)

      MAX_RETRANS_TIMER=60

      BACKOFF_MULTIPLE=3

      MARK_UNREACHABLE=3

   After 3 retransmissions, the implementation would mark the NCE
   UNREACHABLE.  That results in trying an alternative neighbor, such as
   another default router, or ignoring an NCE created by a Redirect as
   specified in [RFC4861].  With the above values, that would occur
   after 4 seconds following the first transmission compared to the

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   2 seconds using the fixed scheme in [RFC4861].  That additional
   delay is small compared to the default ReachableTime of
   30,000 milliseconds.

   After 5 transmissions, i.e., 40 seconds after the initial
   transmission, the example behavior is to switch to multicast NUD
   probes.  In the language of the state machine in [RFC4861], that
   corresponds to the action "Discard entry".  Thus, any attempts to
   send future packets would result in sending multicast NS packets.  An
   implementation MAY retain the backoff value as it switches to
   multicast NUD probes.  The potential downside of deferring switching
   to multicast is that it would take longer for NUD to handle a change
   in a link-layer address, i.e., the case when a host or a router
   changes its link-layer address while keeping the same IPv6 address.
   However, [RFC4861] says that a node MAY send unsolicited NS to handle
   that case, which is rather infrequent in operational networks.  In
   any case, the implementation needs to follow the "SHOULD" in
   Section 3 to switch to multicast solutions within 60 seconds after
   the initial transmission.

   If BACKOFF_MULTIPLE=1, MARK_UNREACHABLE=3, and MAX_UNICAST_SOLICIT=3,
   you would get the same behavior as in [RFC4861].

   If the request was not answered at first -- due, for example, to a
   transitory condition -- an implementation following this algorithm
   would retry immediately and then back off for progressively longer
   periods.  This would allow for a reasonably fast resolution time when
   the transitory condition clears.

   Note that RetransTimer and ReachableTime are by default set from the
   protocol constants RETRANS_TIMER and REACHABLE_TIME but are
   overridden by values advertised in Router Advertisements as specified
   in [RFC4861].  That remains the case even with the protocol updates
   specified in this document.  The key values that the operator would
   configure are BACKOFF_MULTIPLE, MAX_RETRANS_TIMER,
   MAX_UNICAST_SOLICIT, and MAX_MULTICAST_SOLICIT.

   It is useful to have a maximum value for
   ($BACKOFF_MULTIPLE^$solicit_attempt_num)*$RetransTimer so that the
   retransmissions are not too far apart.  The above value of 60 seconds
   for this MAX_RETRANS_TIMER is consistent with DHCPv6.

5.  Acknowledgements

   The comments from Thomas Narten, Philip Homburg, Joel Jaeggli, Hemant
   Singh, Tina Tsou, Suresh Krishnan, and Murray Kucherawy have helped
   improve this document.

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6.  Security Considerations

   Relaxing the retransmission behavior for NUD is believed to have no
   impact on security.  In particular, it doesn't impact the application
   of Secure Neighbor Discovery [RFC3971].

7.  References

7.1.  Normative References

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

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

7.2.  Informative References

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC6583]  Gashinsky, I., Jaeggli, J., and W. Kumari, quot;

   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, testers using the
   assigned testing address ranges MUST NOT be connected to the
   Internet.

   We note that a range of IPv6 addresses has been assigned to BMWG for
   laboratory test purposes, in [RFC5180].  Also, the strong statements
   in the Security Considerations Section of this memo make the scope
   even more clear; this is now a standard fixture of all BMWG memos.

5.  Advisory on RFC 2544 Methods in Real-world 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
   unanticipated difficulties when applying these methods outside the
   lab environment.

   Operating test equipment on production networks according to the
   methods described in [RFC2544], where overload is a possible outcome,
   would no doubt be harmful to user traffic performance.  These tests

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   MUST NOT be used on production networks and as discussed above, the
   tests will never 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 contra-
   indicated by the BMWG.

6.  What to do without RFC 2544?

   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.

   Other standards may help to fill gaps in telecommunication service
   testing.  For example, the IETF has many standards intended to assist
   with network operation, administration and maintenance (OAM), and
   ITU-T Study Group 12 has a recommendation on service activation test
   methodology.

   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 is also intended 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

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   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.  IANA Considerations

   This memo makes no requests of IANA, and hopes that IANA will leave
   it alone as well.

9.  Acknowledgements

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

10.  References

10.1.  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.

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

10.2.  Informative References

Authors' Addresses

   Scott Bradner
   Harvard University
   29 Oxford St.
   Cambridge, MA  02138
   USA

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

   Kevin Dubray
   Juniper Networks

   Phone:
   Fax:
   Email: kdubray@juniper.net
   URI:

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

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

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   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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