One document matched: draft-morton-ippm-testplan-rfc2680-01.xml
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<rfc category="info" docName="draft-morton-ippm-testplan-rfc2680-00"
ipr="pre5378Trust200902">
<front>
<title abbrev="Stds Track Tests RFC2680">Test Plan and Results for
Advancing RFC 2680 on the Standards Track</title>
<author fullname="Len Ciavattone" initials="L." surname="Ciavattone">
<organization>AT&T Labs</organization>
<address>
<postal>
<street>200 Laurel Avenue South</street>
<city>Middletown</city>
<region>NJ</region>
<code>07748</code>
<country>USA</country>
</postal>
<phone>+1 732 420 1239</phone>
<facsimile></facsimile>
<email>lencia@att.com</email>
<uri></uri>
</address>
</author>
<author fullname="Ruediger Geib" initials="R." surname="Geib">
<organization>Deutsche Telekom</organization>
<address>
<postal>
<street>Heinrich Hertz Str. 3-7</street>
<!-- Reorder these if your country does things differently -->
<code>64295</code>
<city>Darmstadt</city>
<region></region>
<country>Germany</country>
</postal>
<phone>+49 6151 58 12747</phone>
<email>Ruediger.Geib@telekom.de</email>
<!-- uri and facsimile elements may also be added -->
</address>
</author>
<author fullname="Al Morton" initials="A." surname="Morton">
<organization>AT&T Labs</organization>
<address>
<postal>
<street>200 Laurel Avenue South</street>
<city>Middletown</city>
<region>NJ</region>
<code>07748</code>
<country>USA</country>
</postal>
<phone>+1 732 420 1571</phone>
<facsimile>+1 732 368 1192</facsimile>
<email>acmorton@att.com</email>
<uri>http://home.comcast.net/~acmacm/</uri>
</address>
</author>
<author fullname="Matthias Wieser" initials="M." surname="Wieser">
<organization>University of Applied Sciences Darmstadt</organization>
<address>
<postal>
<street>Birkenweg 8 Department EIT</street>
<!-- Reorder these if your country does things differently -->
<code>64295</code>
<city>Darmstadt</city>
<region></region>
<country>Germany</country>
</postal>
<phone></phone>
<email>matthias.wieser@stud.h-da.de</email>
<!-- uri and facsimile elements may also be added -->
</address>
</author>
<date day="21" month="October" year="2011" />
<abstract>
<t>This memo proposes to advance a performance metric RFC along the
standards track, specifically RFC 2680 on One-way Loss 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 2680.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>The IETF (IP Performance Metrics working group, IPPM) has considered
how to advance their metrics along the standards track since 2001.</t>
<t>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.</t>
<t>There is consensus <xref target="I-D.ietf-ippm-metrictest"></xref>
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.</t>
<t>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).</t>
<t>This memo's purpose is to implement the current approach for <xref
target="RFC2680"></xref>. </t>
<t>In particular, this memo documents consensus 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.</t>
<t>Another aspect of the metric RFC advancement process is the
requirement to document the work and results. The procedures of <xref
target="RFC2026"></xref> are expanded in<xref target="RFC5657"></xref>,
including sample implementation and interoperability reports. This memo
follows the template in <xref
target="I-D.morton-ippm-advance-metrics"></xref> 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.</t>
<section title="RFC 2680 Coverage">
<t>This plan, in its first draft version, does not cover all critical
requirements and sections of <xref target="RFC2680"></xref>. Material
will be added as it is "discovered" (not all requirements use
requirements language).</t>
</section>
</section>
<section title="A Definition-centric metric advancement process">
<t>The process described in Section 3.5 of <xref
target="I-D.ietf-ippm-metrictest"></xref> 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.</t>
<t>IF two implementations do not measure an equivalent singleton or
sample, or produce the an equivalent statistic,</t>
<t>AND sources of measurement error do not adequately explain the lack
of agreement,</t>
<t>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.</t>
<t>IF there was a lack of clarity or multiple legitimate interpretations
of the definition text,</t>
<t>THEN the text should be modified and the resulting memo proposed for
consensus and advancement along the standards track.</t>
<t>Finally, all the findings MUST be documented in a report that can
support advancement on the standards track, similar to those described
in <xref target="RFC5657"></xref>. 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).</t>
</section>
<section title="Test configuration">
<t>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 <xref target="RFC3432"></xref> or Poisson <xref
target="RFC2330"></xref> sample distributions.</t>
<t>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.</t>
<t>Figure 1 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 <xref
target="I-D.ietf-ippm-metrictest"></xref>.</t>
<t><figure align="center" anchor="L2TPv3_tunnel">
<preamble />
<artwork align="center"><![CDATA[ +----+ +----+ +----+ +----+
|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 |
`-+-' +--------+
]]></artwork>
<postamble>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).</postamble>
</figure></t>
<t>The testing employs the Layer 2 Tunnel Protocol, version 3 (L2TPv3)
<xref target="RFC3931"></xref> 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.</t>
<t>At each end of the tunnel, one pair of VLANs encapsulated in the
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.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
<t>For these tests, a stream of at least 300 packets were sent from
Source to Destination in each implementation. Periodic streams (as per
<xref target="RFC3432"></xref>) with 1 second spacing were used, except
as noted.</t>
<t>As required in Section 2.8.1 of <xref target="RFC2680"></xref>,
packet Type-P must be reported. The packet Type-P for this test was
IP-UDP with Best Effort DCSP. These headers were encapsulated according
to the L2TPv3 specifications <xref target="RFC3931"></xref>, and thus
may not influence the treatment received as the packets traversed the
Internet.</t>
<t>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:</t>
<t>Type-IP-protocol-115-One-way-Packet-Loss-<StreamType>-Stream</t>
<t>With (Section 3.2. <xref target="RFC2680"></xref>) Metric
Parameters:</t>
<t>+ Src, the IP address of a host (12.3.167.16 or 193.159.144.8)</t>
<t>+ Dst, the IP address of a host (193.159.144.8 or 12.3.167.16)</t>
<t>+ T0, a time</t>
<t>+ Tf, a time</t>
<t>+ lambda, a rate in reciprocal seconds</t>
<t>+ Thresh, a maximum waiting time in seconds (see Section 2.8.2 of
<xref target="RFC2680"></xref>) and (Section 3.8. <xref
target="RFC2680"></xref>)</t>
<t>Metric Units: A sequence of pairs; the elements of each pair are:</t>
<t>+ T, a time, and</t>
<t>+ L, either a zero or a one</t>
<t>The values of T in the sequence are monotonic increasing. Note that T
would be a valid parameter to the *singleton*
Type-P-One-way-Packet-Loss, and that L would be a valid value of
Type-P-One-way-Packet Loss (see Section 2 of <xref
target="RFC2680"></xref>).</t>
<t>Also, Section 2.8.4 of <xref target="RFC2680"></xref> 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.</t>
<t>When NetProbe is used in production, a traceroute is conducted in
parallel with, and at the outset of measurements.</t>
<t>Perfas+ does not support traceroute.</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[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 * * *
]]></artwork>
<postamble></postamble>
</figure></t>
<t>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).</t>
</section>
<section title="Error Calibration, RFC 2679">
<t>An implementation is required to report calibration results on clock
synchronization in Section 2.8.3 of <xref target="RFC2680"></xref> (also
required in Section 3.7 of <xref target="RFC2680"></xref> for sample
metrics).</t>
<t>Also, it is recommended to report the probability that a packet
successfully arriving at the destination network interface is
incorrectly designated as lost due to resource exhaustion in Section
2.8.3 of <xref target="RFC2680"></xref>.</t>
<section title="Clock Synchronization Calibration">
<t>First, we look at clock synchronization. Sections 3.6, 3.7, and 3.8
of <xref target="RFC2679"></xref> give the detailed formulation of the
errors and uncertainties for calibration. In summary, Section 3.7.1 of
<xref target="RFC2679"></xref> describes the total time-varying
uncertainty as:</t>
<t>Esynch(t)+ Rsource + Rdest</t>
<t>where:</t>
<t>Esynch(t) denotes an upper bound on the magnitude of clock
synchronization uncertainty.</t>
<t>Rsource and Rdest denote the resolution of the source clock and the
destination clock, respectively.</t>
<t>Further, Section 3.7.2 of <xref target="RFC2679"></xref> describes
the total wire-time uncertainty as</t>
<t>Hsource + Hdest</t>
<t>referring to the upper bounds on host-time to wire-time for source
and destination, respectively.</t>
<t>Section 3.7.3 of <xref target="RFC2679"></xref> 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.</t>
<t>The test context, or Type-P of the test packets, must also be
reported, as required in Section 3.8 of <xref target="RFC2679"></xref>
and all metrics defined there. Type-P is defined in Section 13 of
<xref target="RFC2330"></xref> (as are many terms used below).</t>
<section title="NetProbe Clock Error">
<t>In general, NetProbe clock error is dependent on the specific
version and installation details.</t>
<t>NetProbe operates using host time above the UDP layer, which is
different from the wire-time preferred in <xref
target="RFC2330"></xref>, but can be identified as a source of error
according to Section 3.7.2 of <xref target="RFC2679"></xref>.</t>
<t>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<xref target="RFC2330"></xref> (in fact, smooth
adjustment, long-term drift analysis and compensation, and
infrequent adjustment all lead to stability during measurement
intervals, the main concern).</t>
<t>The resolution of the reported results is 1us (us = microsecond)
in the version of NetProbe tested here, which contributes to at
least +/-1us error.</t>
<t>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.</t>
<t>We performed a NetProbe calibration of the type described in
Section 3.7.3 of <xref target="RFC2679"></xref>, 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:</t>
<t><figure>
<preamble>(Results from the "R" software environment for
statistical computing and graphics - http://www.r-project.org/
)</preamble>
<artwork><![CDATA[> 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
> ]]></artwork>
<postamble>NetProbe Calibration with Cross-Connect Cable,
one-way delay values in microseconds (us)</postamble>
</figure></t>
<t>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.</t>
<t>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
<xref target="I-D.ietf-ippm-metrictest"></xref>), 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)<figure>
<preamble></preamble>
<artwork><![CDATA[> 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
> ]]></artwork>
<postamble></postamble>
</figure></t>
</section>
<section title="Perfas Clock Error">
<t>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.</t>
<t>The resolution of the results reported by Perfas+ is 1us (us =
microsecond) in the version tested here, which contributes to at
least +/-1us error.</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[Port 5001 5002 5003
Min. -227 -226 294
Median -169 -167 323
Mean -159 -157 335
Max. 6 -52 376
s 102 102 93]]></artwork>
<postamble>Perfas Calibration with Cross-Connect Cable, one-way
delay values in microseconds (us)</postamble>
</figure></t>
<t>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.</t>
</section>
</section>
<section title="Packet Loss Determination Error">
<t>Since both measurement implementations have resource limitations,
it is theoretically possible that these limits could be exceeded and a
packet that arrived at the destination successfully might be discarded
in error. </t>
<t>In previous test efforts <xref
target="I-D.morton-ippm-advance-metrics"></xref>, NetProbe produced 6
multicast streams with an aggregate bit rate over 53 Mbit/s, in order
to characterize the 1-way capacity of a NISTNet-based emulator.
Neither the emulator nor the pair of NetProbe implementations used in
this testing dropped any packets in these streams. </t>
<t>The maximum load used here between any 2 NetProbe implementations
was be 11.5 Mbit/s divided equally among 3 unicast test streams. We
conclude that steady resource usage does not contribute error
(additional loss) to the measurements.</t>
</section>
<t></t>
</section>
<section title="Pre-determined Limits on Equivalence">
<t>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.</t>
<t>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.</t>
<t>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.</t>
<t>For Anderson-Darling K-sample (ADK) comparisons, the required
confidence factor for the cross-implementation comparisons SHALL be the
smallest of:</t>
<t><list style="symbols">
<t>0.95 confidence factor at 1ms resolution, or</t>
<t>the smallest confidence factor (in combination with resolution)
of the two same-implementation comparisons for the same test
conditions.</t>
</list>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.</t>
<t>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.</t>
<t>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.</t>
</section>
<section title="Tests to evaluate RFC 2680 Specifications">
<t>This section describes some results from production network
(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.</t>
<t>The procedures are similar contained in Appendix A.1 of <xref
target="I-D.ietf-ippm-metrictest"></xref> for One-way Delay. </t>
<t>Note that there are only five instances of the requirement term
"MUST" in <xref target="RFC2680"></xref> outside of the boilerplate and
<xref target="RFC2119"></xref> reference.</t>
<section title="One-way Packet Loss, ADK Sample Comparison - Same & Cross Implementation">
<t>This test determines if implementations produce results that appear
to come from a common packet loss distribution, as an overall
evaluation of Section 3 of <xref target="RFC2680"></xref>, "A
Definition for Samples of One-way Packet Loss". Same-implementation
comparison results help to set the threshold of equivalence that will
be applied to cross-implementation comparisons.</t>
<t>This test is intended to evaluate measurements in sections 2 and 3
of <xref target="RFC2680"></xref>.</t>
<t>By testing the extent to which the distributions of one-way packet
loss ratios from two implementations of <xref target="RFC2679"></xref>
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 <xref target="RFC2679"></xref>) would require another
set of individual evaluations of equivalence. Instead, we can simply
check which statistics were implemented, and report on those
facts.</t>
<t><list style="numbers">
<t>Configure an L2TPv3 path between test sites, and each pair of
measurement devices to operate tests in their designated pair of
VLANs.</t>
<t>Measure a sample of one-way packet loss singletons with 2 or
more implementations, using identical options and network emulator
settings (if used).</t>
<t>Measure a sample of one-way packet loss 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.</t>
<t>Apply the ADK comparison procedures (see Appendix C of <xref
target="I-D.ietf-ippm-metrictest"></xref>) and determine the
resolution and confidence factor for distribution equivalence of
each same-implementation comparison and each cross-implementation
comparison.</t>
<t>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.</t>
<t>Apply constant correction factors to all singletons of the
sample distributions, as described and limited in Section 5
above.</t>
<t>Compare the cross-implementation ADK performance with the
equivalence threshold determined in step 5 to determine if
equivalence can be declared.</t>
</list></t>
<t>The common parameters used for tests in this section are:</t>
<t><list style="symbols">
<t>IP header + payload = 64 octets</t>
<t>Periodic sampling at 1 packet per second</t>
<t>Test duration = 300 seconds (March 29)</t>
</list>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.</t>
<t>In the result analysis of this section:</t>
<t><list style="symbols">
<t>All comparisons used 1 microsecond resolution.</t>
<t>No Correction Factors were applied.</t>
<t>The 0.95 confidence factor (1.960 for paired stream comparison)
was used.</t>
</list></t>
<section title="NetProbe Same-implementation results">
<t>A single same-implementation comparison </t>
</section>
<section title="Perfas Same-implementation results">
<t>All pair comparisons pass the ADK criterion.</t>
<t></t>
</section>
<section title="One-way Packet Loss, Cross-Implementation ADK Comparison">
<t>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.</t>
</section>
<section title="Conclusions on the ADK Results for One-way Packet Loss">
<t>Similar testing was repeated many times ...</t>
<t>We conclude that the two implementations are capable of producing
equivalent one-way packet loss distributions based on their
interpretation of <xref target="RFC2680"></xref> .</t>
</section>
</section>
<section title="One-way Packet Loss, Loss threshold, RFC 2680">
<t>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.</t>
<t>See Section 2.8.2 of <xref target="RFC2680"></xref>.</t>
<t><list style="numbers">
<t>configure an L2TPv3 path between test sites, and each pair of
measurement devices to operate tests in their designated pair of
VLANs.</t>
<t>configure the network emulator to add 1.0 sec one-way constant
delay in one direction of transmission.</t>
<t>measure (average) one-way delay with 2 or more implementations,
using identical waiting time thresholds (Thresh) for loss set at 3
seconds.</t>
<t>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)</t>
<t>repeat/continue measurements</t>
<t>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.</t>
</list></t>
<t>The common parameters used for tests in this section are:</t>
<t><list style="symbols">
<t>IP header + payload = 64 octets</t>
<t>Poisson sampling at lambda = 1 packet per second</t>
<t>Test duration = 900 seconds total (March 21)</t>
</list>The netem emulator was set to add constant delays as
specified in the procedure above.</t>
<section title="NetProbe results for Loss Threshold">
<t>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 <xref target="RFC2680"></xref>).
This resulted in 342 packets designated as lost in one of the test
streams (with average delay = 3.091 sec).</t>
</section>
<section title="Perfas Results for Loss Threshold">
<t>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).</t>
</section>
<section title="Conclusions for Loss Threshold">
<t>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 <xref
target="RFC2680"></xref>. This is a simple way to enforce the
constant loss threshold envisioned in <xref target="RFC2680"></xref>
(see specific section reference 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.</t>
</section>
</section>
<section title="Implementation of Statistics for One-way Delay">
<t>We check which statistics were implemented, and report on those
facts, noting that Section 4 of <xref target="RFC2680"></xref> does
not specify the calculations exactly, and gives only some illustrative
examples.<figure>
<preamble></preamble>
<artwork><![CDATA[ NetProbe Perfas
4.1. Type-P-One-way-Delay-Packet-Loss-Ave yes yes
(this is more commonly referred to as loss ratio)
]]></artwork>
<postamble>Implementation of Section 4 Statistics</postamble>
</figure></t>
<t></t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>The security considerations that apply to any active measurement of
live networks are relevant here as well. See <xref
target="RFC4656"></xref> and <xref target="RFC5357"></xref>.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This memo makes no requests of IANA, and the authos hope that IANA
will be able to use their time in other worthwhile pursuits.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors thank Lars Eggert for his continued encouragement to
advance the IPPM metrics during his tenure as AD Advisor.</t>
<t>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!</t>
<t>The "NetProbe Team" also acknowledges many useful discussions with
Ganga Maguluri.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include='reference.RFC.2026'?>
<?rfc include='reference.RFC.2330'?>
<?rfc include='reference.RFC.2679'?>
<?rfc include='reference.RFC.2680'?>
<?rfc include='reference.RFC.3432'?>
<?rfc include='reference.RFC.4656'?>
<?rfc include='reference.RFC.4814'?>
<?rfc include='reference.RFC.5226'?>
<?rfc include='reference.RFC.5357'?>
<?rfc include='reference.RFC.5657'?>
<?rfc include='reference.I-D.ietf-ippm-metrictest'?>
</references>
<references title="Informative References">
<?rfc include='reference.I-D.morton-ippm-advance-metrics'?>
<?rfc include='reference.RFC.3931'?>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 05:55:09 |