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Versions: (draft-morton-ippm-testplan-rfc2679) 00 01 02 03 RFC 6808

Network Working Group                                      L. Ciavattone
Internet-Draft                                                 AT&T Labs
Intended status: Informational                                   R. Geib
Expires: April 23, 2012                                 Deutsche Telekom
                                                               A. Morton
                                                               AT&T Labs
                                                               M. Wieser
                                          University of Applied Sciences
                                                               Darmstadt
                                                        October 21, 2011


  Test Plan and Results for Advancing RFC 2679 on the Standards Track
                  draft-ietf-ippm-testplan-rfc2679-00

Abstract

   This memo proposes to advance a performance metric RFC along the
   standards track, specifically RFC 2679 on One-way Delay Metrics.
   Observing that the metric definitions themselves should be the
   primary focus rather than the implementations of metrics, this memo
   describes the test procedures to evaluate specific metric requirement
   clauses to determine if the requirement has been interpreted and
   implemented as intended.  Two completely independent implementations
   have been tested against the key specifications of RFC 2679.

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 April 23, 2012.



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Copyright Notice

   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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  RFC 2679 Coverage  . . . . . . . . . . . . . . . . . . . .  5
   2.  A Definition-centric metric advancement process  . . . . . . .  5
   3.  Test configuration . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Error Calibration, RFC 2679  . . . . . . . . . . . . . . . . . 10
     4.1.  NetProbe Error and Type-P  . . . . . . . . . . . . . . . . 11
     4.2.  Perfas Error and Type-P  . . . . . . . . . . . . . . . . . 13
   5.  Pre-determined Limits on Equivalence . . . . . . . . . . . . . 14
   6.  Tests to evaluate RFC 2679 Specifications  . . . . . . . . . . 14
     6.1.  One-way Delay, ADK Sample Comparison - Same & Cross
           Implementation . . . . . . . . . . . . . . . . . . . . . . 15
       6.1.1.  NetProbe Same-implementation results . . . . . . . . . 16
       6.1.2.  Perfas Same-implementation results . . . . . . . . . . 17
       6.1.3.  One-way Delay, Cross-Implementation ADK Comparison . . 18
       6.1.4.  Conclusions on the ADK Results for One-way Delay . . . 18
     6.2.  One-way Delay, Loss threshold, RFC 2679  . . . . . . . . . 19
       6.2.1.  NetProbe results for Loss Threshold  . . . . . . . . . 20
       6.2.2.  Perfas Results for Loss Threshold  . . . . . . . . . . 20
       6.2.3.  Conclusions for Loss Threshold . . . . . . . . . . . . 20
     6.3.  One-way Delay, First-bit to Last bit, RFC 2679 . . . . . . 20
       6.3.1.  NetProbe and Perfas Results for Serialization  . . . . 21
       6.3.2.  Conclusions for Serialization  . . . . . . . . . . . . 22
     6.4.  One-way Delay, Difference Sample Metric (Lab)  . . . . . . 22
       6.4.1.  NetProbe results for Differential Delay  . . . . . . . 23
       6.4.2.  Perfas results for Differential Delay  . . . . . . . . 24
       6.4.3.  Conclusions for Differential Delay . . . . . . . . . . 24
     6.5.  Implementation of Statistics for One-way Delay . . . . . . 24
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 25
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 25
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 25
     10.2. Informative References . . . . . . . . . . . . . . . . . . 26
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 26















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1.  Introduction

   The IETF (IP Performance Metrics working group, IPPM) has considered
   how to advance their metrics along the standards track since 2001,
   with the initial publication of Bradner/Paxson/Mankin's memo [ref to
   work in progress, draft-bradner-metricstest-].  The original proposal
   was to compare the results of implementations of the metrics, because
   the usual procedures for advancing protocols did not appear to apply.
   It was found to be difficult to achieve consensus on exactly how to
   compare implementations, since there were many legitimate sources of
   variation that would emerge in the results despite the best attempts
   to keep the network paths equal, and because considerable variation
   was allowed in the parameters (and therefore implementation) of each
   metric.  Flexibility in metric definitions, essential for
   customization and broad appeal, made the comparison task quite
   difficult.

   A renewed work effort sought to investigate ways in which the
   measurement variability could be reduced and thereby simplify the
   problem of comparison for equivalence.

   There is *preliminary* consensus [I-D.ietf-ippm-metrictest] that the
   metric definitions should be the primary focus of evaluation rather
   than the implementations of metrics, and equivalent results are
   deemed to be evidence that the metric specifications are clear and
   unambiguous.  This is the metric specification equivalent of protocol
   interoperability.  The advancement process either produces confidence
   that the metric definitions and supporting material are clearly
   worded and unambiguous, OR, identifies ways in which the metric
   definitions should be revised to achieve clarity.

   The process should also permit identification of options that were
   not implemented, so that they can be removed from the advancing
   specification (this is an aspect more typical of protocol advancement
   along the standards track).

   This memo's purpose is to implement the current approach for
   [RFC2679].  It was prepared to help progress discussions on the topic
   of metric advancement, both through e-mail and at the upcoming IPPM
   meeting at IETF.

   In particular, consensus is sought on the extent of tolerable errors
   when assessing equivalence in the results.  In discussions, the IPPM
   working group agreed that test plan and procedures should include the
   threshold for determining equivalence, and this information should be
   available in advance of cross-implementation comparisons.  This memo
   includes procedures for same-implementation comparisons to help set
   the equivalence threshold.



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   Another aspect of the metric RFC advancement process is the
   requirement to document the work and results.  The procedures of
   [RFC2026] are expanded in[RFC5657], including sample implementation
   and interoperability reports.  This memo follows the template in
   [I-D.morton-ippm-advance-metrics] for the report that accompanies the
   protocol action request submitted to the Area Director, including
   description of the test set-up, procedures, results for each
   implementation and conclusions.

1.1.  RFC 2679 Coverage

   This plan, in it's first draft version, does not cover all critical
   requirements and sections of [RFC2679].  Material will be added as it
   is "discovered" (not all requirements use requirements language).


2.  A Definition-centric metric advancement process

   The process described in Section 3.5 of [I-D.ietf-ippm-metrictest]
   takes as a first principle that the metric definitions, embodied in
   the text of the RFCs, are the objects that require evaluation and
   possible revision in order to advance to the next step on the
   standards track.

   IF two implementations do not measure an equivalent singleton or
   sample, or produce the an equivalent statistic,

   AND sources of measurement error do not adequately explain the lack
   of agreement,

   THEN the details of each implementation should be audited along with
   the exact definition text, to determine if there is a lack of clarity
   that has caused the implementations to vary in a way that affects the
   correspondence of the results.

   IF there was a lack of clarity or multiple legitimate interpretations
   of the definition text,

   THEN the text should be modified and the resulting memo proposed for
   consensus and advancement along the standards track.

   Finally, all the findings MUST be documented in a report that can
   support advancement on the standards track, similar to those
   described in [RFC5657].  The list of measurement devices used in
   testing satisfies the implementation requirement, while the test
   results provide information on the quality of each specification in
   the metric RFC (the surrogate for feature interoperability).




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   The figure below illustrates this process:

      ,---.
     /     \
    ( Start )
     \     /    Implementations
      `-+-'        +-------+
        |         /|   1   `.
    +---+----+   / +-------+ `.-----------+      ,-------.
    |  RFC   |  /             |Check for  |    ,' was RFC `.  YES
    |        | /              |Equivalence.....  clause x   -------+
    |        |/    +-------+  |under      |    `. clear?  ,'       |
    | Metric \.....|   2   ....relevant   |      `---+---'    +----+---+
    | Metric |\    +-------+  |identical  |       No |        |Report  |
    | Metric | \              |network    |      +---+---.    |results+|
    |  ...   |  \             |conditions |      |Modify |    |Advance |
    |        |   \ +-------+  |           |      |Spec   +----+  RFC   |
    +--------+    \|   n   |.'+-----------+      +-------+    |request?|
                   +-------+                                  +--------+


3.  Test configuration

   One metric implementation used was NetProbe version 5.8.5, (an
   earlier version is used in the WIPM system and deployed world-wide).
   NetProbe uses UDP packets of variable size, and can produce test
   streams with Periodic [RFC3432] or Poisson [RFC2330] sample
   distributions.

   The other metric implementation used was Perfas+ version 3.1,
   developed by Deutsche Telekom.  Perfas+ uses UDP unicast packets of
   variable size (but supports also TCP and multicast).  Test streams
   with periodic, Poisson or uniform sample distributions may be used.

   Figure 2 shows a view of the test path as each Implementation's test
   flows pass through the Internet and the L2TPv3 tunnel IDs (1 and 2),
   based on Figure 1 of [I-D.ietf-ippm-metrictest].














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           +----+  +----+                                +----+  +----+
           |Imp1|  |Imp1|           ,---.                |Imp2|  |Imp2|
           +----+  +----+          /     \    +-------+  +----+  +----+
             | V100 | V200        /       \   | Tunnel|   | V300  |  V400
             |      |            (         )  | Head  |   |       |
            +--------+  +------+ |         |__| Router|  +----------+
            |Ethernet|  |Tunnel| |Internet |  +---B---+  |Ethernet  |
            |Switch  |--|Head  |-|         |      |      |Switch    |
            +-+--+---+  |Router| |         |  +---+---+--+--+--+----+
              |__|      +--A---+ (         )  |Network|     |__|
                                  \       /   |Emulat.|
            U-turn                 \     /    |"netem"|     U-turn
            V300 to V400            `-+-'     +-------+     V100 to V200



           Implementations                  ,---.       +--------+
                               +~~~~~~~~~~~/     \~~~~~~| Remote |
            +------->-----F2->-|          /       \     |->---.  |
            | +---------+      | Tunnel  (         )    |     |  |
            | | transmit|-F1->-|   ID 1  (         )    |->.  |  |
            | | Imp 1   |      +~~~~~~~~~|         |~~~~|  |  |  |
            | | receive |-<--+           (         )    | F1  F2 |
            | +---------+    |           |Internet |    |  |  |  |
            *-------<-----+  F1          |         |    |  |  |  |
              +---------+ |  | +~~~~~~~~~|         |~~~~|  |  |  |
              | transmit|-*  *-|         |         |    |<-*  |  |
              | Imp 2   |      | Tunnel  (         )    |     |  |
              | receive |-<-F2-|   ID 2   \       /     |<----*  |
              +---------+      +~~~~~~~~~~~\     /~~~~~~| Switch |
                                            `-+-'       +--------+

     Illustrations of a test setup with a bi-directional tunnel.  The
      upper diagram emphasizes the VLAN connectivity and geographical
    location.  The lower diagram shows example flows traveling between
    two measurement implementations (for simplicity, only two flows are
                                  shown).

                                 Figure 1

   The testing employs the Layer 2 Tunnel Protocol, version 3 (L2TPv3)
   [RFC3931] tunnel between test sites on the Internet.  The tunnel IP
   and L2TPv3 headers are intended to conceal the test equipment
   addresses and ports from hash functions that would tend to spread
   different test streams across parallel network resources, with likely
   variation in performance as a result.

   At each end of the tunnel, one pair of VLANs encapsulated in the



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   tunnel are looped-back so that test traffic is returned to each test
   site.  Thus, test streams traverse the L2TP tunnel twice, but appear
   to be one-way tests from the test equipment point of view.

   The network emulator is a host running Fedora 14 Linux
   [http://fedoraproject.org/] with IP forwarding enabled and the
   "netem" Network emulator as part of the Fedora Kernel 2.6.35.11 [http
   ://www.linuxfoundation.org/collaborate/workgroups/networking/netem]
   loaded and operating.  Connectivity across the netem/Fedora host was
   accomplished by bridging Ethernet VLAN interfaces together with
   "brctl" commands (e.g., eth1.100 <-> eth2.100).  The netem emulator
   was activated on one interface (eth1) and only operates on test
   streams traveling in one direction.  In some tests, independent netem
   instances operated separately on each VLAN.

   The links between the netem emulator host and router and switch were
   found to be 100baseTx-HD (100Mbps half duplex) as reported by "mii-
   tool"when the testing was complete.  Use of Half Duplex was not
   intended, but probably added a small amount of delay variation that
   could have been avoided in full duplex mode.

   Each individual test was run with common packet rates (1 pps, 10pps)
   Poisson/Periodic distributions, and IP packet sizes of 64, 340, and
   500 Bytes.

   For these tests, a stream of at least 300 packets were sent from
   Source to Destination in each implementation.  Periodic streams (as
   per [RFC3432]) with 1 second spacing were used, except as noted.

   With the L2TPv3 tunnel in use, the metric name for the testing
   configured here (with respect to the IP header exposed to Internet
   processing) is:

   Type-IP-protocol-115-One-way-Delay-<StreamType>-Stream

   With (Section 4.2.  [RFC2679]) Metric Parameters:

   + Src, the IP address of a host (12.3.167.16 or 193.159.144.8)

   + Dst, the IP address of a host (193.159.144.8 or 12.3.167.16)

   + T0, a time

   + Tf, a time

   + lambda, a rate in reciprocal seconds

   + Thresh, a maximum waiting time in seconds (see Section 3.82 of



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   [RFC2679]) And (Section 4.3.  [RFC2679])

   Metric Units: A sequence of pairs; the elements of each pair are:

   + T, a time, and

   + dT, either a real number or an undefined number of seconds.

   The values of T in the sequence are monotonic increasing.  Note that
   T would be a valid parameter to Type-P-One-way-Delay, and that dT
   would be a valid value of Type-P-One-way-Delay.

   Also, Section 3.8.4 of [RFC2679] recommends that the path SHOULD be
   reported.  In this test set-up, most of the path details will be
   concealed from the implementations by the L2TPv3 tunnels, thus a more
   informative path trace route can be conducted by the routers at each
   location.

   When NetProbe is used in production, a traceroute is conducted in
   parallel with, and at the outset of measurements.

   Perfas+ does not support traceroute.





























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 IPLGW#traceroute 193.159.144.8

 Type escape sequence to abort.
 Tracing the route to 193.159.144.8

   1 12.126.218.245 [AS 7018] 0 msec 0 msec 4 msec
   2 cr84.n54ny.ip.att.net (12.123.2.158) [AS 7018] 4 msec 4 msec
     cr83.n54ny.ip.att.net (12.123.2.26) [AS 7018] 4 msec
   3 cr1.n54ny.ip.att.net (12.122.105.49) [AS 7018] 4 msec
     cr2.n54ny.ip.att.net (12.122.115.93) [AS 7018] 0 msec
     cr1.n54ny.ip.att.net (12.122.105.49) [AS 7018] 0 msec
   4 n54ny02jt.ip.att.net (12.122.80.225) [AS 7018] 4 msec 0 msec
     n54ny02jt.ip.att.net (12.122.80.237) [AS 7018] 4 msec
   5 192.205.34.182 [AS 7018] 0 msec
     192.205.34.150 [AS 7018] 0 msec
     192.205.34.182 [AS 7018] 4 msec
   6 da-rg12-i.DA.DE.NET.DTAG.DE (62.154.1.30) [AS 3320] 88 msec 88 msec
 88 msec
   7 217.89.29.62 [AS 3320] 88 msec 88 msec 88 msec
   8 217.89.29.55 [AS 3320] 88 msec 88 msec 88 msec
   9  *  *  *

   It was only possible to conduct the traceroute for the measured path
   on one of the tunnel-head routers (the normal trace facilities of the
   measurement systems are confounded by the L2TPv3 tunnel
   encapsulation).


4.  Error Calibration, RFC 2679

   An implementation is required to report on its error calibration in
   Section 3.8 of [RFC2679] (also required in Section 4.8 for sample
   metrics).  Sections 3.6, 3.7, and 3.8 of [RFC2679] give the detailed
   formulation of the errors and uncertainties for calibration.  In
   summary, Section 3.7.1 of [RFC2679] describes the total time-varying
   uncertainty as:

   Esynch(t)+ Rsource + Rdest

   where:

   Esynch(t) denotes an upper bound on the magnitude of clock
   synchronization uncertainty.

   Rsource and Rdest denote the resolution of the source clock and the
   destination clock, respectively.

   Further, Section 3.7.2 of [RFC2679] describes the total wire-time



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   uncertainty as

   Hsource + Hdest

   referring to the upper bounds on host-time to wire-time for source
   and destination, respectively.

   Section 3.7.3 of [RFC2679] describes a test with small packets over
   an isolated minimal network where the results can be used to estimate
   systematic and random components of the sum of the above errors or
   uncertainties.  In a test with hundreds of singletons, the median is
   the systematic error and when the median is subtracted from all
   singletons, the remaining variability is the random error.

   The test context, or Type-P of the test packets, must also be
   reported, as required in Section 3.8 of [RFC2679] and all metrics
   defined there.  Type-P is defined in Section 13 of [RFC2330] (as are
   many terms used below).

4.1.  NetProbe Error and Type-P

   Type-P for this test was IP-UDP with Best Effort DCSP.  These headers
   were encapsulated according to the L2TPv3 specifications [RFC3931],
   and thus may not influence the treatment received as the packets
   traversed the Internet.

   In general, NetProbe error is dependent on the specific version and
   installation details.

   NetProbe operates using host time above the UDP layer, which is
   different from the wire-time preferred in [RFC2330], but can be
   identified as a source of error according to Section 3.7.2 of
   [RFC2679].

   Accuracy of NetProbe measurements is usually limited by NTP
   synchronization performance (which is typically taken as ~+/-1ms
   error or greater), although the installation used in this testing
   often exhibits errors much less than typical for NTP.  The primary
   stratum 1 NTP server is closely located on a sparsely utilized
   network management LAN, thus it avoids many concerns raised in
   Section 10 of[RFC2330] (in fact, smooth adjustment, long-term drift
   analysis and compensation, and infrequent adjustment all lead to
   stability during measurement intervals, the main concern).

   The resolution of the reported results is 1us (us = microsecond) in
   the version of NetProbe tested here, which contributes to at least
   +/-1us error.




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   NetProbe implements a time-keeping sanity check on sending and
   receiving time-stamping processes.  When the significant process
   interruption takes place, individual test packets are flagged as
   possibly containing unusual time errors, and are excluded from the
   sample used for all "time" metrics.

   We performed a NetProbe calibration of the type described in Section
   3.7.3 of [RFC2679], using 64 Byte packets over a cross-connect cable.
   The results estimate systematic and random components of the sum of
   the Hsource + Hdest errors or uncertainties.  In a test with 300
   singletons conducted over 30 seconds (periodic sample with 100ms
   spacing), the median is the systematic error and the remaining
   variability is the random error.  One set of results is tabulated
   below:

   (Results from the "R" software environment for statistical computing
   and graphics - http://www.r-project.org/ )
   > summary(XD4CAL)
         CAL1            CAL2             CAL3
    Min.   : 89.0   Min.   : 68.00   Min.   : 54.00
    1st Qu.: 99.0   1st Qu.: 77.00   1st Qu.: 63.00
    Median :110.0   Median : 79.00   Median : 65.00
    Mean   :116.8   Mean   : 83.74   Mean   : 69.65
    3rd Qu.:127.0   3rd Qu.: 88.00   3rd Qu.: 74.00
    Max.   :205.0   Max.   :177.00   Max.   :163.00
   >
   NetProbe Calibration with Cross-Connect Cable, one-way delay values
   in microseconds (us)

   The median or systematic error can be as high as 110 us, and the
   range of the random error is also on the order of 116 us for all
   streams.

   Also, anticipating the Anderson-Darling K-sample (ADK) comparisons to
   follow, we corrected the CAL2 values for the difference between means
   between CAL2 and CAL3 (as specified in [I-D.ietf-ippm-metrictest]),
   and found strong support for the (Null Hypothesis that) the samples
   are from the same distribution (resolution of 1 us and alpha equal
   0.05 and 0.01)












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   > XD4CVCAL2 <- XD4CAL$CAL2 - (mean(XD4CAL$CAL2)-mean(XD4CAL$CAL3))
   > boxplot(XD4CVCAL2,XD4CAL$CAL3)
   > XD4CV2_ADK <- adk.test(XD4CVCAL2, XD4CAL$CAL3)
   > XD4CV2_ADK
   Anderson-Darling k-sample test.

   Number of samples:  2
   Sample sizes: 300 300
   Total number of values: 600
   Number of unique values: 97

   Mean of Anderson Darling Criterion: 1
   Standard deviation of Anderson Darling Criterion: 0.75896

   T = (Anderson Darling Criterion - mean)/sigma

   Null Hypothesis: All samples come from a common population.

                        t.obs P-value extrapolation
   not adj. for ties  0.71734 0.17042             0
   adj. for ties     -0.39553 0.44589             1
   >

4.2.  Perfas Error and Type-P

   Perfas+ is configured to use GPS synchronisation and uses NTP
   synchronization as a fall-back or default.  GPS synchronisation
   worked throughout this test with the exception of the calibration
   stated here (one implementation was NTP synchronised only).  The time
   stamp accuracy typically is 0.1 ms.

   The resolution of the results reported by Perfas+ is 1us (us =
   microsecond) in the version tested here, which contributes to at
   least +/-1us error.

   Port    5001 5002 5003
   Min.    -227 -226  294
   Median  -169 -167  323
   Mean    -159 -157  335
   Max.       6  -52  376
   s        102  102   93
   Perfas Calibration with Cross-Connect Cable, one-way delay values in
   microseconds (us)

   The median or systematic error can be as high as 323 us, and the
   range of the random error is also less than 232 us for all streams.





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5.  Pre-determined Limits on Equivalence

   In this section, we provide the numerical limits on comparisons
   between implementations, in order to declare that the results are
   equivalent and therefore, the tested specification is clear.

   A key point is that the allowable errors, corrections, and confidence
   levels only need to be sufficient to detect mis-interpretation of the
   tested specification resulting in diverging implementations.

   Also, the allowable error must be sufficient to compensate for
   measured path differences.  It was simply not possible to measure
   fully identical paths in the VLAN-loopback test configuration used,
   and this practical compromise must be taken into account.

   For Anderson-Darling K-sample (ADK) comparisons, the required
   confidence factor for the cross-implementation comparisons SHALL be
   the smallest of:

   o  0.95 confidence factor at 1ms resolution, or

   o  the smallest confidence factor (in combination with resolution) of
      the two same-implementation comparisons for the same test
      conditions.

   A constant time accuracy error of as much as +/-0.5ms MAY be removed
   from one implementation's distributions (all singletons) before the
   ADK comparison is conducted.

   A constant propagation delay error (due to use of different sub-nets
   between the switch and measurement devices at each location) of as
   much as +2ms MAY be removed from one implementation's distributions
   (all singletons) before the ADK comparison is conducted.

   For comparisons involving the mean of a sample or other central
   statistics, the limits on both the time accuracy error and the
   propagation delay error constants given above also apply.


6.  Tests to evaluate RFC 2679 Specifications

   This section describes some results from real-world (cross-Internet)
   tests with measurement devices implementing IPPM metrics and a
   network emulator to create relevant conditions, to determine whether
   the metric definitions were interpreted consistently by implementors.

   The procedures are slightly modified from the original procedures
   contained in Appendix A.1 of [I-D.ietf-ippm-metrictest].  The



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   modifications include the use of the mean statistic for comparisons.

   Note that there are only five instances of the requirement term
   "MUST" in [RFC2679] outside of the boilerplate and [RFC2119]
   reference.

6.1.  One-way Delay, ADK Sample Comparison - Same & Cross Implementation

   This test determines if implementations produce results that appear
   to come from a common delay distribution, as an overall evaluation of
   Section 4 of [RFC2679], "A Definition for Samples of One-way Delay".
   Same-implementation comparison results help to set the threshold of
   equivalence that will be applied to cross-implementation comparisons.

   This test is intended to evaluate measurements in sections 3 and 4 of
   [RFC2679].

   By testing the extent to which the distributions of one-way delay
   singletons from two implementations of [RFC2679] appear to be from
   the same distribution, we economize on comparisons, because comparing
   a set of individual summary statistics (as defined in Section 5 of
   [RFC2679]) would require another set of individual evaluations of
   equivalence.  Instead, we can simply check which statistics were
   implemented, and report on those facts.

   1.  Configure an L2TPv3 path between test sites, and each pair of
       measurement devices to operate tests in their designated pair of
       VLANs.

   2.  Measure a sample of one-way delay singletons with 2 or more
       implementations, using identical options and network emulator
       settings (if used).

   3.  Measure a sample of one-way delay singletons with *four*
       instances of the *same* implementations, using identical options,
       noting that connectivity differences SHOULD be the same as for
       the cross implementation testing.

   4.  Apply the ADK comparison procedures (see Appendix C of
       [I-D.ietf-ippm-metrictest]) and determine the resolution and
       confidence factor for distribution equivalence of each same-
       implementation comparison and each cross-implementation
       comparison.

   5.  Take the coarsest resolution and confidence factor for
       distribution equivalence from the same-implementation pairs, or
       the limit defined in Section 5 above, as a limit on the
       equivalence threshold for these experimental conditions.



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   6.  Apply constant correction factors to all singletons of the sample
       distributions, as described and limited in Section 5 above.

   7.  Compare the cross-implementation ADK performance with the
       equivalence threshold determined in step 5 to determine if
       equivalence can be declared.

   The common parameters used for tests in this section are:

   o  IP header + payload = 64 octets

   o  Periodic sampling at 1 packet per second

   o  Test duration = 300 seconds (March 29)

   The netem emulator was set for 100ms average delay, with uniform
   delay variation of +/-50ms.  In this experiment, the netem emulator
   was configured to operate independently on each VLAN and thus the
   emulator itself is a potential source of error when comparing streams
   that traverse the test path in different directions.

   In the result analysis of this section:

   o  All comparisons used 1 microsecond resolution.

   o  No Correction Factors were applied.

   o  The 0.95 confidence factor (1.960 for paired stream comparison)
      was used.

6.1.1.  NetProbe Same-implementation results

   A single same-implementation comparison fails the ADK criterion (s1
   <-> sB).  We note that these streams traversed the test path in
   opposite directions, making the live network factors a possibility to
   explain the difference.

   All other pair comparisons pass the ADK criterion.













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          +------------------------------------------------------+
          |            |             |             |             |
          | ti.obs (P) |     s1      |     s2      |     sA      |
          |            |             |             |             |
          .............|.............|.............|.............|
          |            |             |             |             |
          |    s2      | 0.25 (0.28) |             |             |
          |            |             |             |             |
          ...........................|.............|.............|
          |            |             |             |             |
          |    sA      | 0.60 (0.19) |-0.80 (0.57) |             |
          |            |             |             |             |
          ...........................|.............|.............|
          |            |             |             |             |
          |    sB      | 2.64 (0.03) | 0.07 (0.31) |-0.52 (0.48) |
          |            |             |             |             |
          +------------+-------------+-------------+-------------+

               NetProbe ADK Results for same-implementation

6.1.2.  Perfas Same-implementation results

   All pair comparisons pass the ADK criterion.

          +------------------------------------------------------+
          |            |             |             |             |
          | ti.obs (P) |     p1      |     p2      |     p3      |
          |            |             |             |             |
          .............|.............|.............|.............|
          |            |             |             |             |
          |    p2      | 0.06 (0.32) |             |             |
          |            |             |             |             |
          .........................................|.............|
          |            |             |             |             |
          |    p3      | 1.09 (0.12) | 0.37 (0.24) |             |
          |            |             |             |             |
          ...........................|.............|.............|
          |            |             |             |             |
          |    p4      |-0.81 (0.57) |-0.13 (0.37) | 1.36 (0.09) |
          |            |             |             |             |
          +------------+-------------+-------------+-------------+

                Perfas ADK Results for same-implementation








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6.1.3.  One-way Delay, Cross-Implementation ADK Comparison

   The cross-implementation results are compared using a combined ADK
   analysis [ref], where all NetProbe results are compared with all
   Perfas results after testing that the combined same-implementation
   results pass the ADK criterion.

   When 4 (same) samples are compared, the ADK criterion for 0.95
   confidence is 1.915, and when all 8 (cross) samples are compared it
   is 1.85.

   Combination of Anderson-Darling K-Sample Tests.

   Sample sizes within each data set:
   Data set 1 :  299 297 298 300 (NetProbe)
   Data set 2 :  300 300 298 300 (Perfas)
   Total sample size per data set: 1194 1198
   Number of unique values per data set: 1188 1192
   ...
   Null Hypothesis:
   All samples within a data set come from a common distribution.
   The common distribution may change between data sets.

   NetProbe           ti.obs P-value extrapolation
   not adj. for ties 0.64999 0.21355             0
   adj. for ties     0.64833 0.21392             0
   Perfas
   not adj. for ties 0.55968 0.23442             0
   adj. for ties     0.55840 0.23473             0

   Combined Anderson-Darling Criterion:
                      tc.obs P-value extrapolation
   not adj. for ties 0.85537 0.17967             0
   adj. for ties     0.85329 0.18010             0

   The combined same-implementation samples and the combined cross-
   implementation comparison all pass the ADK criteria at P>=0.18 and
   support the Null Hypothesis (both data sets come from a common
   distribution).

   We also see that the paired ADK comparisons are rather critical.
   Although the NetProbe s1-sB comparison failed, the combined data set
   from 4 streams passed the ADK criterion easily.

6.1.4.  Conclusions on the ADK Results for One-way Delay

   Similar testing was repeated many times in the months of March and
   April 2011.  There were many experiments where a single test stream



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   from NetProbe or Perfas proved to be different from the others in
   paired comparisons (even same comparisons).  When the out lier stream
   was removed from the comparison, the remaining streams passed
   combined ADK criterion.  Also, the application of correction factors
   resulted in higher comparison success.

   We conclude that the two implementations are capable of producing
   equivalent one-way delay distributions based on their interpretation
   of [RFC2679] .

6.2.  One-way Delay, Loss threshold, RFC 2679

   This test determines if implementations use the same configured
   maximum waiting time delay from one measurement to another under
   different delay conditions, and correctly declare packets arriving in
   excess of the waiting time threshold as lost.

   See Section 3.5 of [RFC2679], 3rd bullet point and also Section 3.8.2
   of [RFC2679].

   1.  configure an L2TPv3 path between test sites, and each pair of
       measurement devices to operate tests in their designated pair of
       VLANs.

   2.  configure the network emulator to add 1.0 sec one-way constant
       delay in one direction of transmission.

   3.  measure (average) one-way delay with 2 or more implementations,
       using identical waiting time thresholds (Thresh) for loss set at
       3 seconds.

   4.  configure the network emulator to add 3 sec one-way constant
       delay in one direction of transmission equivalent to 2 seconds of
       additional one-way delay (or change the path delay while test is
       in progress, when there are sufficient packets at the first delay
       setting)

   5.  repeat/continue measurements

   6.  observe that the increase measured in step 5 caused all packets
       with 2 sec additional delay to be declared lost, and that all
       packets that arrive successfully in step 3 are assigned a valid
       one-way delay.

   The common parameters used for tests in this section are:






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   o  IP header + payload = 64 octets

   o  Poisson sampling at lambda = 1 packet per second

   o  Test duration = 900 seconds total (March 21)

   The netem emulator was set to add constant delays as specified in the
   procedure above.

6.2.1.  NetProbe results for Loss Threshold

   In NetProbe, the Loss Threshold is implemented uniformly over all
   packets as a post-processing routine.  With the Loss Threshold set at
   3 seconds, all packets with one-way delay >3 seconds are marked
   "Lost" and included in the Lost Packet list with their transmission
   time (as required in Section 3.3 of [RFC2680]).  This resulted in 342
   packets designated as lost in one of the test streams (with average
   delay = 3.091 sec).

6.2.2.  Perfas Results for Loss Threshold

   Perfas uses a fixed Loss Threshold which was not adjustable during
   this study.  The Loss Threshold is approximately one minute, and
   emulation of a delay of this size was not attempted.  However, it is
   possible to implement any delay threshold desired with a post-
   processing routine and subsequent analysis.  Using this method, 195
   packets would be declared lost (with average delay = 3.091 sec).

6.2.3.  Conclusions for Loss Threshold

   Both implementations assume that any constant delay value desired can
   be used as the Loss Threshold, since all delays are stored as a pair
   <Time, Delay> as required in [RFC2679] .  This is a simple way to
   enforce the constant loss threshold envisioned in [RFC2679] (see
   specific section references above).  We take the position that the
   assumption of post-processing is compliant, and that the text of the
   RFC should be revised slightly to include this point.

6.3.  One-way Delay, First-bit to Last bit, RFC 2679

   This test determines if implementations register the same relative
   change in delay from one packet size to another, indicating that the
   first-to-last time-stamping convention has been followed.  This test
   tends to cancel the sources of error which may be present in an
   implementation.

   See Section 3.7.2 of [RFC2679], and Section 10.2 of [RFC2330].




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   1.  configure an L2TPv3 path between test sites, and each pair of
       measurement devices to operate tests in their designated pair of
       VLANs, and ideally including a low-speed link (it was not
       possible to change the link configuration during testing, so the
       lowest speed link present was the basis for serialization time
       comparisons).

   2.  measure (average) one-way delay with 2 or more implementations,
       using identical options and equal size small packets (64 octet IP
       header and payload)

   3.  maintain the same path with additional emulated 100 ms one-way
       delay

   4.  measure (average) one-way delay with 2 or more implementations,
       using identical options and equal size large packets (500 octet
       IP header and payload)

   5.  observe that the increase measured between steps 2 and 4 is
       equivalent to the increase in ms expected due to the larger
       serialization time for each implementation.  Most of the
       measurement errors in each system should cancel, if they are
       stationary.

   The common parameters used for tests in this section are:

   o  IP header + payload = 64 octets

   o  Periodic sampling at l packet per second

   o  Test duration = 300 seconds total (April 12)

   The netem emulator was set to add constant 100ms delay.

6.3.1.  NetProbe and Perfas Results for Serialization

   When the IP header + payload size was increased from 64 octets to 500
   octets, there was a delay increase observed.













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   Mean Delays in us
   NetProbe
   Payload    s1      s2      sA      sB
   500    190893  191179  190892  190971
    64    189642  189785  189747  189467
   Diff     1251    1394    1145    1505

   Perfas
   Payload    p1      p2      p3      p4
   500    190908  190911  191126  190709
    64    189706  189752  189763  190220
   Diff     1202   1159    1363      489

   Serialization tests, all values in microseconds

   The typical delay increase when the larger packets were used was 1.1
   to 1.5 ms (with one outlier).  The typical measurements indicate that
   a link with approximately 3 Mbit/s capacity is present on the path.

   Through investigation of the facilities involved, it was determined
   that the lowest speed link was approximately 45 Mbit/s, and therefore
   the estimated difference should be about 0.077 ms.  The observed
   differences are much higher.

   The unexpected large delay difference was also the outcome when
   testing serialization times in a lab environment, using the NIST Net
   Emulator and NetProbe [ref to earlier lab tests].

6.3.2.  Conclusions for Serialization

   Since it was not possible to confirm the estimated serialization time
   increases in field tests, we resort to examination of the
   implementations to determine compliance.

   NetProbe performs all time stamping above the IP-layer, accepting
   that some compromises must be made to achieve extreme portability and
   measurement scale.  Therefore, the first-to-last bit convention is
   supported because the serialization time is included in the one-way
   delay measurement, enabling comparison with other implementations.

   Perfas >>>>>>>>>>>>>>> TBD

6.4.  One-way Delay, Difference Sample Metric (Lab)

   This test determines if implementations register the same relative
   increase in delay from one measurement to another under different
   delay conditions.  This test tends to cancel the sources of error
   which may be present in an implementation.



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   This test is intended to evaluate measurements in sections 3 and 4 of
   [RFC2679].

   1.  configure an L2TPv3 path between test sites, and each pair of
       measurement devices to operate tests in their designated pair of
       VLANs.

   2.  measure (average) one-way delay with 2 or more implementations,
       using identical options

   3.  configure the path with X+Y ms one-way delay

   4.  repeat measurements

   5.  observe that the (average) increase measured in steps 2 and 4 is
       ~Y ms for each implementation.  Most of the measurement errors in
       each system should cancel, if they are stationary.

   In this test, X=1000ms and Y=1000ms.

   The common parameters used for tests in this section are:

   o  IP header + payload = 64 octets

   o  Poisson sampling at lambda = 1 packet per second

   o  Test duration = 900 seconds total (March 21)

   The netem emulator was set to add constant delays as specified in the
   procedure above.

6.4.1.  NetProbe results for Differential Delay

         Average pre-increase delay, microseconds        1089868.0
         Average post 1s additional, microseconds        2089686.0
         Difference (should be ~= Y = 1s)                 999818.0

               Average delays before/after 1 second increase

   The NetProbe implementation observed a 1 second increase with a 182
   microsecond error (assuming that the netem emulated delay difference
   is exact).

   We note that this differential delay test has been run under lab
   conditions and published in prior work [ref to "advance metrics"
   draft].  The error was 6 microseconds.





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6.4.2.  Perfas results for Differential Delay

         Average pre-increase delay, microseconds        1089794.0
         Average post 1s additional, microseconds        2089801.0
         Difference (should be ~= Y = 1s)                1000007.0

               Average delays before/after 1 second increase

   The Perfas implementation observed a 1 second increase with a 7
   microsecond error.

6.4.3.  Conclusions for Differential Delay

   Again, the live network conditions appear to have influenced the
   results, but both implementations measured the same delay increase
   within their calibration accuracy.

6.5.  Implementation of Statistics for One-way Delay

   The ADK tests the extent to which the sample distributions of one-way
   delay singletons from two implementations of [RFC2679] appear to be
   from the same overall distribution.  By testing this way, we
   economize on the number of comparisons, because comparing a set of
   individual summary statistics (as defined in Section 5 of [RFC2679])
   would require another set of individual evaluations of equivalence.
   Instead, we can simply check which statistics were implemented, and
   report on those facts, noting that Section 5 of [RFC2679] does not
   specify the calculations exactly, and gives only some illustrative
   examples.

                                                 NetProbe    Perfas

   5.1. Type-P-One-way-Delay-Percentile            yes       no

   5.2. Type-P-One-way-Delay-Median                yes       no

   5.3. Type-P-One-way-Delay-Minimum               yes       yes

   5.4. Type-P-One-way-Delay-Inverse-Percentile    no        no



   Implementation of Section 5 Statistics

   5.1.  Type-P-One-way-Delay-Percentile 5.2.  Type-P-One-way-Delay-
   Median 5.3.  Type-P-One-way-Delay-Minimum 5.4.  Type-P-One-way-Delay-
   Inverse-Percentile




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7.  Security Considerations

   The security considerations that apply to any active measurement of
   live networks are relevant here as well.  See [RFC4656] and
   [RFC5357].


8.  IANA Considerations

   This memo makes no requests of IANA, and hopes that IANA will be as
   accepting of our new computer overlords as the authors intend to be.


9.  Acknowledgements

   The authors thank Lars Eggert for his continued encouragement to
   advance the IPPM metrics during his tenure as AD Advisor.

   Nicole Kowalski supplied the needed CPE router for the NetProbe side
   of the test set-up, and graciously managed her testing in spite of
   issues caused by dual-use of the router.  Thanks Nicole!

   The "NetProbe Team" also acknowledges many useful discussions with
   Ganga Maguluri.


10.  References

10.1.  Normative References

   [I-D.ietf-ippm-metrictest]
              Geib, R., Morton, A., Fardid, R., and A. Steinmitz, "IPPM
              standard advancement testing",
              draft-ietf-ippm-metrictest-03 (work in progress),
              June 2011.

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

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

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, September 1999.



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   [RFC2680]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Packet Loss Metric for IPPM", RFC 2680, September 1999.

   [RFC3432]  Raisanen, V., Grotefeld, G., and A. Morton, "Network
              performance measurement with periodic streams", RFC 3432,
              November 2002.

   [RFC4656]  Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
              Zekauskas, "A One-way Active Measurement Protocol
              (OWAMP)", RFC 4656, September 2006.

   [RFC4814]  Newman, D. and T. Player, "Hash and Stuffing: Overlooked
              Factors in Network Device Benchmarking", RFC 4814,
              March 2007.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC5357]  Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
              Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
              RFC 5357, October 2008.

   [RFC5657]  Dusseault, L. and R. Sparks, "Guidance on Interoperation
              and Implementation Reports for Advancement to Draft
              Standard", BCP 9, RFC 5657, September 2009.

10.2.  Informative References

   [I-D.morton-ippm-advance-metrics]
              Morton, A., "Lab Test Results for Advancing Metrics on the
              Standards Track", draft-morton-ippm-advance-metrics-02
              (work in progress), October 2010.

   [RFC3931]  Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
              Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.















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Authors' Addresses

   Len Ciavattone
   AT&T Labs
   200 Laurel Avenue South
   Middletown, NJ  07748
   USA

   Phone: +1 732 420 1239
   Fax:
   Email: lencia@att.com
   URI:


   Ruediger Geib
   Deutsche Telekom
   Heinrich Hertz Str. 3-7
   Darmstadt,   64295
   Germany

   Phone: +49 6151 58 12747
   Email: Ruediger.Geib@telekom.de


   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/


   Matthias Wieser
   University of Applied Sciences Darmstadt
   Birkenweg 8 Department EIT
   Darmstadt,   64295
   Germany

   Phone:
   Email: matthias.wieser@stud.h-da.de







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