Internet DRAFT - draft-ietf-ippm-testplan-rfc2680
draft-ietf-ippm-testplan-rfc2680
Network Working Group L. Ciavattone
Internet-Draft AT&T Labs
Intended status: Informational R. Geib
Expires: October 5, 2014 Deutsche Telekom
A. Morton
AT&T Labs
M. Wieser
Technical University Darmstadt
April 3, 2014
Test Plan and Results for Advancing RFC 2680 on the Standards Track
draft-ietf-ippm-testplan-rfc2680-05
Abstract
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.
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 October 5, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. RFC 2680 Coverage . . . . . . . . . . . . . . . . . . . . 4
2. A Definition-centric metric advancement process . . . . . . . 4
3. Test configuration . . . . . . . . . . . . . . . . . . . . . 4
4. Error Calibration, RFC 2680 . . . . . . . . . . . . . . . . . 9
4.1. Clock Synchronization Calibration . . . . . . . . . . . . 9
4.2. Packet Loss Determination Error . . . . . . . . . . . . . 10
5. Pre-determined Limits on Equivalence . . . . . . . . . . . . 10
6. Tests to evaluate RFC 2680 Specifications . . . . . . . . . . 11
6.1. One-way Loss, ADK Sample Comparison . . . . . . . . . . . 11
6.1.1. 340B/Periodic Cross-imp. results . . . . . . . . . . 12
6.1.2. 64B/Periodic Cross-imp. results . . . . . . . . . . . 13
6.1.3. 64B/Poisson Cross-imp. results . . . . . . . . . . . 14
6.1.4. Conclusions on the ADK Results for One-way Packet
Loss . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2. One-way Loss, Delay threshold . . . . . . . . . . . . . . 15
6.2.1. NetProbe results for Loss Threshold . . . . . . . . . 16
6.2.2. Perfas Results for Loss Threshold . . . . . . . . . . 17
6.2.3. Conclusions for Loss Threshold . . . . . . . . . . . 17
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6.3. One-way Loss with Out-of-Order Arrival . . . . . . . . . 17
6.4. Poisson Sending Process Evaluation . . . . . . . . . . . 18
6.4.1. NetProbe Results . . . . . . . . . . . . . . . . . . 19
6.4.2. Perfas+ Results . . . . . . . . . . . . . . . . . . . 20
6.4.3. Conclusions for Goodness-of-Fit . . . . . . . . . . . 22
6.5. Implementation of Statistics for One-way Loss . . . . . . 22
7. Conclusions for RFC 2680bis . . . . . . . . . . . . . . . . . 23
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
11. Appendix - Network Configuration and sample commands . . . . 24
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 27
12.1. Normative References . . . . . . . . . . . . . . . . . . 27
12.2. Informative References . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29
1. Introduction
The IETF (specifically the IP Performance Metrics working group, or
IPPM) has considered how to advance their metrics along the standards
track since 2001.
The renewed work effort sought to investigate ways in which the
measurement variability could be reduced and thereby simplify the
problem of comparison for equivalence. As a result, there is
consensus (captured in [RFC6576]) that equivalent results from
independent implementations of metric specifications are sufficient
evidence that the specifications themselves are clear and
unambiguous; it is the parallel concept of protocol interoperability
for metric specifications. 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. It is a
non-goal to compare the specific implementations themselves.
The process also permits identification of options described in the
metric RFC 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
[RFC2680] and document the results.
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-
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implementation comparisons. This memo includes procedures for same-
implementation comparisons to help set the equivalence threshold.
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
[RFC6808] 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.
The conclusion reached is that [RFC2680] should be advanced on the
Standards Track with modifications. The revised text of RFC 2680bis
is ready for review [I-D.morton-ippm-2680-bis], but awaits work-in
progress to update the IPPM Framework [RFC2330]. Therefore, this
memo documents the information to support [RFC2680] advancement, and
the approval of RFC2680bis is left for future action.
1.1. RFC 2680 Coverage
This plan is intended to cover all critical requirements and sections
of [RFC2680].
Note that there are only five instances of the requirement term
"MUST" in [RFC2680] outside of the boilerplate and [RFC2119]
reference.
Material may be added as it is "discovered" (apparently, not all
requirements use requirements language).
2. A Definition-centric metric advancement process
The process described in Section 3.5 of [RFC6576] 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. This
memo follows that process.
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 [WIPM]).
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]. Perfas+ uses UDP unicast
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packets of variable size (but also supports TCP and multicast). Test
streams with periodic, Poisson, or uniform sample distributions may
be used.
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 [RFC6576].
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+------------+ +------------+
| Imp 1 | ,---. | Imp 2 |
+------------+ / \ +-------+ +------------+
| 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 (where "Imp #" is the sender and receiver of implementation
1 or 2, either Perfas+ and NetProbe in this test). The lower diagram
shows example flows traveling between two measurement
implementations. For simplicity only two flows are shown, and netem
is omitted (it would appear before or after the Internet, depending
on the flow).
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
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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
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 [Fedora] with
IP forwarding enabled and the "netem" Network emulator as part of the
Fedora Kernel 2.6.35.11 [netem] loaded and operating. The standard
kernel is "tickless" replacing the previous periodic timer (250HZ,
with 4ms uncertainty) interrupts with on-demand interrupts.
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. See the Appendix for more details.
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" [mii-tool], when 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 was sent from
source to destination in each implementation. Periodic streams (as
per [RFC3432]) with 1 second spacing were used, except as noted.
As required in Section 2.8.1 of [RFC2680], packet Type-P must be
reported. The packet Type-P for this test was IP-UDP with Best
Effort DSCP. These headers were encapsulated according to the L2TPv3
specifications [RFC3931], and thus may not influence the treatment
received as the packets traversed the Internet.
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-Packet-Loss-<StreamType>-Stream
With (Section 3.2. [RFC2680]) metric parameters:
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+ 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 2.8.2 of
[RFC2680]) and (Section 3.8. [RFC2680])
Metric Units: A sequence of pairs; the elements of each pair are:
+ T, a time, and
+ L, either a zero or a one
The values of T in the sequence are monotonically increasing. Note
that T would be a valid parameter of *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 [RFC2680]).
Also, Section 2.8.4 of [RFC2680] 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 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 * * *
NetProbe Traceroute
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 2680
An implementation is required to report calibration results on clock
synchronization in Section 2.8.3 of [RFC2680] (also required in
Section 3.7 of [RFC2680] for sample metrics).
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 [RFC2680].
4.1. Clock Synchronization Calibration
For NetProbe and Perfas+ clock synchronization test results, refer to
Section 4 of [RFC6808].
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4.2. Packet Loss Determination Error
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.
In previous test efforts [I-D.morton-ippm-advance-metrics], 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.
The maximum load used here between any 2 NetProbe implementations was
11.5 Mbit/s divided equally among 3 unicast test streams. We
concluded that steady resource usage does not contribute error
(additional loss) to the measurements.
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 misinterpretation 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) [ADK] comparisons, the required
confidence factor for the cross-implementation comparisons SHALL be
the smallest of:
o 0.95 confidence factor at 1 packet resolution, or
o the smallest confidence factor (in combination with resolution) of
the two same-implementation comparisons for the same test
conditions (if the number of streams is sufficient to allow such
comparisons).
For Anderson-Darling Goodness-of-Fit (ADGoF) [Radgof] comparisons,
the required level of significance for the same-implementation
Goodness-of-Fit (GoF) SHALL be 0.05 or 5%, as specified in
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Section 11.4 of [RFC2330]. This is equivalent to a 95% confidence
factor.
6. Tests to evaluate RFC 2680 Specifications
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.
The procedures are similar contained in Appendix A.1 of [RFC6576] for
One-way Delay.
6.1. One-way Loss, ADK Sample Comparison
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 [RFC2680], "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.
This test is intended to evaluate measurements in sections 2, 3, and
4 of [RFC2680].
By testing the extent to which the counts of one-way packet loss
counts on different test streams of two [RFC2680] implementations
appear to be from the same loss process, we reduce comparison steps
because comparing the resulting summary statistics (as defined in
Section 4 of [RFC2680]) would require a redundant set of equivalence
evaluations. We can easily check whether the single statistic in
Section 4 of [RFC2680] was implemented, and report on that fact.
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 packet loss singletons with 2 or more
implementations, using identical options and network emulator
settings (if used).
3. Measure a sample of one-way packet loss singletons with *four or
more* instances of the *same* implementations, using identical
options, noting that connectivity differences SHOULD be the same
as for cross implementation testing.
4. If less than ten test streams are available, skip to step 7.
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5. Apply the ADK comparison procedures (see Appendix C of [RFC6576])
and determine the resolution and confidence factor for
distribution equivalence of each same-implementation comparison
and each cross-implementation comparison.
6. 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.
7. Compare the cross-implementation ADK performance with the
equivalence threshold determined in step 5 to determine if
equivalence can be declared.
The metric parameters varied for each loss test, and they are listed
first in each sub-section below.
The cross-implementation comparison uses a simple ADK analysis
[Rtool] [Radk], where all NetProbe loss counts are compared with all
Perfas+ loss results.
In the result analysis of this section:
o All comparisons used 1 packet resolution.
o No Correction Factors were applied.
o The 0.95 confidence factor (1.960 for cross-implementation
comparison) was used.
6.1.1. 340B/Periodic Cross-imp. results
Tests described in this section used:
o IP header + payload = 340 octets
o Periodic sampling at 1 packet per second
o Test duration = 1200 seconds (during April 7, 2011, EDT)
The netem emulator was set for 100ms constant delay, with 10% loss
ratio. 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.
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=======================================
A07bps_loss <- c(114, 175, 138, 142, 181, 105) (NetProbe)
A07per_loss <- c(115, 128, 136, 127, 139, 138) (Perfas+)
> A07bps_loss <- c(114, 175, 138, 142, 181, 105)
> A07per_loss <- c(115, 128, 136, 127, 139, 138)
>
> A07cross_loss_ADK <- adk.test(A07bps_loss, A07per_loss)
> A07cross_loss_ADK
Anderson-Darling k-sample test.
Number of samples: 2
Sample sizes: 6 6
Total number of values: 12
Number of unique values: 11
Mean of Anderson Darling Criterion: 1
Standard deviation of Anderson Darling Criterion: 0.6569
T = (Anderson Darling Criterion - mean)/sigma
Null Hypothesis: All samples come from a common population.
t.obs P-value extrapolation
not adj. for ties 0.52043 0.20604 0
adj. for ties 0.62679 0.18607 0
=======================================
The cross-implementation comparisons pass the ADK criterion.
6.1.2. 64B/Periodic Cross-imp. results
Tests described in this section used:
o IP header + payload = 64 octets
o Periodic sampling at 1 packet per second
o Test duration = 300 seconds (during March 24, 2011, EDT)
The netem emulator was set for 0ms constant delay, with 10% loss
ratio.
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=======================================
> M24per_loss <- c(42,34,35,35) (Perfas+)
> M24apd_23BC_loss <- c(27,39,29,24) (NetProbe)
> M24apd_loss23BC_ADK <- adk.test(M24apd_23BC_loss,M24per_loss)
> M24apd_loss23BC_ADK
Anderson-Darling k-sample test.
Number of samples: 2
Sample sizes: 4 4
Total number of values: 8
Number of unique values: 7
Mean of Anderson Darling Criterion: 1
Standard deviation of Anderson Darling Criterion: 0.60978
T = (Anderson Darling Criterion - mean)/sigma
Null Hypothesis: All samples come from a common population.
t.obs P-value extrapolation
not adj. for ties 0.76921 0.16200 0
adj. for ties 0.90935 0.14113 0
Warning: At least one sample size is less than 5.
p-values may not be very accurate.
=======================================
The cross-implementation comparisons pass the ADK criterion.
6.1.3. 64B/Poisson Cross-imp. results
Tests described in this section used:
o IP header + payload = 64 octets
o Poisson sampling at lambda = 1 packet per second
o Test duration = 20 minutes (during April 27, 2011, EDT)
The netem configuration was 0ms delay and 10% loss, but there were
two passes through an emulator for each stream, and loss emulation
was present for 18 minutes of the 20 minute test.
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=======================================
A27aps_loss <- c(91,110,113,102,111,109,112,113) (NetProbe)
A27per_loss <- c(95,123,126,114) (Perfas+)
A27cross_loss_ADK <- adk.test(A27aps_loss, A27per_loss)
> A27cross_loss_ADK
Anderson-Darling k-sample test.
Number of samples: 2
Sample sizes: 8 4
Total number of values: 12
Number of unique values: 11
Mean of Anderson Darling Criterion: 1
Standard deviation of Anderson Darling Criterion: 0.65642
T = (Anderson Darling Criterion - mean)/sigma
Null Hypothesis: All samples come from a common population.
t.obs P-value extrapolation
not adj. for ties 2.15099 0.04145 0
adj. for ties 1.93129 0.05125 0
Warning: At least one sample size is less than 5.
p-values may not be very accurate.
>
=======================================
The cross-implementation comparisons barely pass the ADK criterion at
95% = 1.960 when adjusting for ties.
6.1.4. Conclusions on the ADK Results for One-way Packet Loss
We conclude that the two implementations are capable of producing
equivalent one-way packet loss measurements based on their
interpretation of [RFC2680].
6.2. One-way Loss, Delay threshold
This test determines if implementations use the same configured
maximum waiting time delay from one measurement to another under
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different delay conditions, and correctly declare packets arriving in
excess of the waiting time threshold as lost.
See Section 2.8.2 of [RFC2680].
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 1sec 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:
o IP header + payload = 64 octets
o Poisson sampling at lambda = 1 packet per second
o Test duration = 900 seconds total (March 21, 2011 EDT)
The netem emulator settings added constant delays as specified in the
procedure above.
6.2.1. NetProbe results for Loss Threshold
In NetProbe, the Loss Threshold was 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 were 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
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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 [RFC2680]. This is a simple way to
enforce the constant loss threshold envisioned in [RFC2680] (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.
6.3. One-way Loss with Out-of-Order Arrival
Section 3.6 of [RFC2680] indicates that implementations need to
ensure that reordered packets are handled correctly using an
uncapitalized "must". In essence, this is an implied requirement
because the correct packet must be identified as lost if it fails to
arrive before its delay threshold under all circumstances, and
reordering is always a possibility on IP network paths. See
[RFC4737] for the definition of reordering used in IETF standard-
compliant measurements.
Using the procedure of section 6.1, the netem emulator was set to
introduce 10% loss, significant delay (2000 ms) and delay variation
(1000 ms), which was sufficient to produce packet reordering because
each packet's emulated delay is independent from others.
The tests described in this section used:
o IP header + payload = 64 octets
o Periodic sampling = 1 packet per second
o Test duration = 600 seconds (during May 2, 2011, EDT)
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=======================================
> Y02aps_loss <- c(53,45,67,55) (NetProbe)
> Y02per_loss <- c(59,62,67,69) (Perfas+)
> Y02cross_loss_ADK <- adk.test(Y02aps_loss, Y02per_loss)
> Y02cross_loss_ADK
Anderson-Darling k-sample test.
Number of samples: 2
Sample sizes: 4 4
Total number of values: 8
Number of unique values: 7
Mean of Anderson Darling Criterion: 1
Standard deviation of Anderson Darling Criterion: 0.60978
T = (Anderson Darling Criterion - mean)/sigma
Null Hypothesis: All samples come from a common population.
t.obs P-value extrapolation
not adj. for ties 1.11282 0.11531 0
adj. for ties 1.19571 0.10616 0
Warning: At least one sample size is less than 5.
p-values may not be very accurate.
>
=======================================
The test results indicate that extensive reordering was present.
Both implementations capture the extensive delay variation between
adjacent packets. In NetProbe, packet arrival order is preserved in
the raw measurement files, so an examination of arrival packet
sequence numbers also indicates reordering.
Despite extensive continuous packet reordering present in the
transmission path, the distributions of loss counts from the two
implementations pass the ADK criterion at 95% = 1.960.
6.4. Poisson Sending Process Evaluation
Section 3.7 of [RFC2680] indicates that implementations need to
ensure that their sending process is reasonably close to a classic
Poisson distribution when used. Much more detail on sample
distribution generation and Goodness-of-Fit testing is specified in
Section 11.4 of [RFC2330] and the Appendix of [RFC2330].
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In this section, each implementation's Poisson distribution is
compared with an idealistic version of the distribution available in
the base functionality of the R-tool for Statistical Analysis[Rtool],
and performed using the Anderson-Darling Goodness-of-Fit test package
(ADGofTest) [Radgof]. The Goodness-of-Fit criterion derived from
[RFC2330] requires a test statistic value AD <= 2.492 for 5%
significance. The Appendix of [RFC2330] also notes that there may be
difficulty satisfying the ADGofTest when the sample includes many
packets (when 8192 were used, the test always failed, but smaller
sets of the stream passed).
Both implementations were configured to produce Poisson distributions
with lambda = 1 packet per second, and assign received packet
timestamps in the measurement application (above UDP layer, see the
calibration results in Section 4 of [RFC6808] for assessment of
error).
6.4.1. NetProbe Results
Section 11.4 of [RFC2330] suggests three possible measurement points
to evaluate the Poisson distribution. The NetProbe analysis uses
"user-level timestamps made just before or after the system call for
transmitting the packet".
The statistical summary for two NetProbe streams is below:
=======================================
> summary(a27ms$s1[2:1152])
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.0100 0.2900 0.6600 0.9846 1.3800 8.6390
> summary(a27ms$s2[2:1152])
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.010 0.280 0.670 0.979 1.365 8.829
=======================================
We see that both the Means are near the specified lambda = 1.
The results of ADGoF tests for these two streams is shown below:
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=======================================
> ad.test( a27ms$s1[2:101], pexp, 1)
Anderson-Darling GoF Test
data: a27ms$s1[2:101] and pexp
AD = 0.8908, p-value = 0.4197
alternative hypothesis: NA
> ad.test( a27ms$s1[2:1001], pexp, 1)
Anderson-Darling GoF Test
data: a27ms$s1[2:1001] and pexp
AD = 0.9284, p-value = 0.3971
alternative hypothesis: NA
> ad.test( a27ms$s2[2:101], pexp, 1)
Anderson-Darling GoF Test
data: a27ms$s2[2:101] and pexp
AD = 0.3597, p-value = 0.8873
alternative hypothesis: NA
> ad.test( a27ms$s2[2:1001], pexp, 1)
Anderson-Darling GoF Test
data: a27ms$s2[2:1001] and pexp
AD = 0.6913, p-value = 0.5661
alternative hypothesis: NA
=======================================
We see that both 100 and 1000 packet sets from two different streams
(s1 and s2) all passed the AD <= 2.492 criterion.
6.4.2. Perfas+ Results
Section 11.4 of [RFC2330] suggests three possible measurement points
to evaluate the Poisson distribution. The Perfas+ analysis uses
"wire times for the packets as recorded using a packet filter".
However, due to limited access at the Perfas+ side of the test setup,
the captures were made after the Perfas+ streams traversed the
production network, adding a small amount of unwanted delay variation
to the wire times (and possibly error due to packet loss).
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The statistical summary for two Perfas+ streams is below:
=======================================
> summary(a27pe$p1)
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.004 0.347 0.788 1.054 1.548 4.231
> summary(a27pe$p2)
Min. 1st Qu. Median Mean 3rd Qu. Max.
0.0010 0.2710 0.7080 0.9696 1.3740 7.1160
=======================================
We see that both the means are near the specified lambda = 1.
The results of ADGoF tests for these two streams is shown below:
=======================================
> ad.test(a27pe$p1, pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p1 and pexp
AD = 1.1364, p-value = 0.2930
alternative hypothesis: NA
> ad.test(a27pe$p2, pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p2 and pexp
AD = 0.5041, p-value = 0.7424
alternative hypothesis: NA
> ad.test(a27pe$p1[1:100], pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p1[1:100] and pexp
AD = 0.7202, p-value = 0.5419
alternative hypothesis: NA
> ad.test(a27pe$p1[101:193], pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p1[101:193] and pexp
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AD = 1.4046, p-value = 0.201
alternative hypothesis: NA
> ad.test(a27pe$p2[1:100], pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p2[1:100] and pexp
AD = 0.4758, p-value = 0.7712
alternative hypothesis: NA
> ad.test(a27pe$p2[101:193], pexp, 1 )
Anderson-Darling GoF Test
data: a27pe$p2[101:193] and pexp
AD = 0.3381, p-value = 0.9068
alternative hypothesis: NA
>
=======================================
We see that both 193, 100, and 93 packet sets from two different
streams (p1 and p2) all passed the AD <= 2.492 criterion.
6.4.3. Conclusions for Goodness-of-Fit
Both NetProbe and Perfas+ implementations produce adequate Poisson
distributions according to the Anderson-Darling Goodness-of-Fit at
the 5% significance (1-alpha = 0.05, or 95% confidence level).
6.5. Implementation of Statistics for One-way Loss
We check which statistics were implemented, and report on those
facts, noting that Section 4 of [RFC2680] does not specify the
calculations exactly, and gives only some illustrative examples.
NetProbe Perfas
4.1. Type-P-One-way-Packet-Loss-Average yes yes
(this is more commonly referred to as loss ratio)
Implementation of Section 4 Statistics
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We note that implementations refer to this metric as a loss ratio,
and this is an area for likely revision of the text to make it more
consistent with wide-spread usage.
7. Conclusions for RFC 2680bis
This memo concludes that [RFC2680] should be advanced on the
standards track, and recommends the following edits to improve the
text (which are not deemed significant enough to affect maturity).
o Revise Type-P-One-way-Packet-Loss-Ave to Type-P-One-way-Delay-
Packet-Loss-Ratio .
o Regarding implementation of the loss delay threshold (section
6.2), the assumption of post-processing is compliant, and the text
of RFC 2680bis should be revised slightly to include this point.
o The IETF has reached consensus on guidance for reporting metrics
in [RFC6703], and this memo should be referenced in RFC2680bis to
incorporate recent experience where appropriate.
We note that there are at least two Errata on [RFC2680] and these
should be processed as part of the editing process.
We recognize the existence of BCP 170 [RFC6390] providing guidelines
for development of drafts describing new performance metrics.
However, the advancement of [RFC2680] represents fine-tuning of long-
standing specifications based on experience that helped to formulate
BCP 170, and material that satisfies some of the requirements of
[RFC6390] can be found in other RFCs, such as the IPPM Framework
[RFC2330]. Thus, no specific changes to address BCP 170 guidelines
are recommended for RFC 2680bis.
8. Security Considerations
The security considerations that apply to any active measurement of
live networks are relevant here as well. See [RFC4656] and
[RFC5357].
9. IANA Considerations
This memo makes no requests of IANA, and the authors hope that IANA
personnel will be able to use their valuable time in other worthwhile
pursuits.
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10. 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 on
statistical interpretation with Ganga Maguluri.
Constructive comments and helpful reviews where also provided by Bill
Cerveny, Joachim Fabini, and Ann Cerveny.
11. Appendix - Network Configuration and sample commands
This Appendix provides some background information on the host
configuration and sample tc commands for the "netem" network
emulator, as described in Section 3 and Figure 1 in the body of this
memo. These details are also applicable to the test plan in
[RFC6808].
The host interface and configuration is shown below:
[system@dell4-4 ~]$ su
Password:
[root@dell4-4 system]# service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
[root@dell4-4 system]# service iptables stop
iptables: Flushing firewall rules: [ OK ]
iptables: Setting chains to policy ACCEPT: nat filter [ OK ]
iptables: Unloading modules: [ OK ]
[root@dell4-4 system]# brctl show
bridge name bridge id STP enabled interfaces
virbr0 8000.000000000000 yes
[root@dell4-4 system]# ifconfig eth1.300 0.0.0.0 promisc up
[root@dell4-4 system]# ifconfig eth1.400 0.0.0.0 promisc up
[root@dell4-4 system]# ifconfig eth2.400 0.0.0.0 promisc up
[root@dell4-4 system]# ifconfig eth2.300 0.0.0.0 promisc up
[root@dell4-4 system]# brctl addbr br300
[root@dell4-4 system]# brctl addif br300 eth1.300
[root@dell4-4 system]# brctl addif br300 eth2.300
[root@dell4-4 system]# ifconfig br300 up
[root@dell4-4 system]# brctl addbr br400
[root@dell4-4 system]# brctl addif br400 eth1.400
[root@dell4-4 system]# brctl addif br400 eth2.400
[root@dell4-4 system]# ifconfig br400 up
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[root@dell4-4 system]# brctl show
bridge name bridge id STP enabled interfaces
br300 8000.0002b3109b8a no eth1.300
eth2.300
br400 8000.0002b3109b8a no eth1.400
eth2.400
virbr0 8000.000000000000 yes
[root@dell4-4 system]# brctl showmacs br300
port no mac addr is local? ageing timer
2 00:02:b3:10:9b:8a yes 0.00
1 00:02:b3:10:9b:99 yes 0.00
1 00:02:b3:c4:c9:7a no 0.52
2 00:02:b3:cf:02:c6 no 0.52
2 00:0b:5f:54:de:81 no 0.01
[root@dell4-4 system]# brctl showmacs br400
port no mac addr is local? ageing timer
2 00:02:b3:10:9b:8a yes 0.00
1 00:02:b3:10:9b:99 yes 0.00
2 00:02:b3:c4:c9:7a no 0.60
1 00:02:b3:cf:02:c6 no 0.42
2 00:0b:5f:54:de:81 no 0.33
[root@dell4-4 system]# tc qdisc add dev eth1.300 root netem delay 100ms
[root@dell4-4 system]# ifconfig eth1.200 0.0.0.0 promisc up
[root@dell4-4 system]# vconfig add eth1 100
Added VLAN with VID == 100 to IF -:eth1:-
[root@dell4-4 system]# ifconfig eth1.100 0.0.0.0 promisc up
[root@dell4-4 system]# vconfig add eth2 100
Added VLAN with VID == 100 to IF -:eth2:-
[root@dell4-4 system]# ifconfig eth2.100 0.0.0.0 promisc up
[root@dell4-4 system]# ifconfig eth2.200 0.0.0.0 promisc up
[root@dell4-4 system]# brctl addbr br100
[root@dell4-4 system]# brctl addif br100 eth1.100
[root@dell4-4 system]# brctl addif br100 eth2.100
[root@dell4-4 system]# ifconfig br100 up
[root@dell4-4 system]# brctl addbr br200
[root@dell4-4 system]# brctl addif br200 eth1.200
[root@dell4-4 system]# brctl addif br200 eth2.200
[root@dell4-4 system]# ifconfig br200 up
[root@dell4-4 system]# brctl show
bridge name bridge id STP enabled interfaces
br100 8000.0002b3109b8a no eth1.100
eth2.100
br200 8000.0002b3109b8a no eth1.200
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eth2.200
br300 8000.0002b3109b8a no eth1.300
eth2.300
br400 8000.0002b3109b8a no eth1.400
eth2.400
virbr0 8000.000000000000 yes
[root@dell4-4 system]# brctl showmacs br100
port no mac addr is local? ageing timer
2 00:02:b3:10:9b:8a yes 0.00
1 00:02:b3:10:9b:99 yes 0.00
1 00:0a:e4:83:89:07 no 0.19
2 00:0b:5f:54:de:81 no 0.91
2 00:e0:ed:0f:72:86 no 1.28
[root@dell4-4 system]# brctl showmacs br200
port no mac addr is local? ageing timer
2 00:02:b3:10:9b:8a yes 0.00
1 00:02:b3:10:9b:99 yes 0.00
2 00:0a:e4:83:89:07 no 1.14
2 00:0b:5f:54:de:81 no 1.87
1 00:e0:ed:0f:72:86 no 0.24
[root@dell4-4 system]# tc qdisc add dev eth1.100 root netem delay 100ms
[root@dell4-4 system]#
======================================================================
Some sample tc command lines controlling netem and its impairments
are given below.
tc qdisc add dev eth1.100 root netem loss 0%
tc qdisc add dev eth1.200 root netem loss 0%
tc qdisc add dev eth1.300 root netem loss 0%
tc qdisc add dev eth1.400 root netem loss 0%
Add delay and delay variation:
tc qdisc change dev eth1.100 root netem delay 100ms 50ms
tc qdisc change dev eth1.200 root netem delay 100ms 50ms
tc qdisc change dev eth1.300 root netem delay 100ms 50ms
tc qdisc change dev eth1.400 root netem delay 100ms 50ms
Add delay, delay variation, and loss:
tc qdisc change dev eth1 root netem delay 2000ms 1000ms loss 10%
=====================================================================
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12. References
12.1. Normative References
[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.
[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.
[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
S., and J. Perser, "Packet Reordering Metrics", RFC 4737,
November 2006.
[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.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
October 2011.
[RFC6576] Geib, R., Morton, A., Fardid, R., and A. Steinmitz, "IP
Performance Metrics (IPPM) Standard Advancement Testing",
BCP 176, RFC 6576, March 2012.
[RFC6703] Morton, A., Ramachandran, G., and G. Maguluri, "Reporting
IP Network Performance Metrics: Different Points of View",
RFC 6703, August 2012.
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[RFC6808] Ciavattone, L., Geib, R., Morton, A., and M. Wieser, "Test
Plan and Results Supporting Advancement of RFC 2679 on the
Standards Track", RFC 6808, December 2012.
12.2. Informative References
[ADK] Scholz, F. and M. Stephens, "K-sample Anderson-Darling
Tests of Fit, for Continuous and Discrete cases",
University of Washington, Technical Report No. 81, May
1986.
[Fedora] "http://fedoraproject.org/", .
[I-D.morton-ippm-2680-bis]
Almes, G., Zekauskas, M., and A. Morton, "A One-Way Loss
Metric for IPPM", draft-morton-ippm-2680-bis-02 (work in
progress), February 2014.
[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.
[Perfas] Heidemann, C., "Qualitaet in IP-Netzen Messverfahren",
published by ITG Fachgruppe, 2nd meeting 5.2.3 (NGN)
http://www.itg523.de/oeffentlich/01nov/
Heidemann_QOS_Messverfahren.pdf , November 2001.
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[Radgof] Bellosta, C., "ADGofTest: Anderson-Darling Goodness-of-Fit
Test. R package version 0.3.", http://cran.r-project.org/
web/packages/ADGofTest/index.html, December 2011.
[Radk] Scholz, F., "adk: Anderson-Darling K-Sample Test and
Combinations of Such Tests. R package version 1.0.", ,
2008.
[Rtool] R Development Core Team, , "R: A language and environment
for statistical computing. R Foundation for Statistical
Computing, Vienna, Austria. ISBN 3-900051-07-0, URL
http://www.R-project.org/", , 2011.
[WIPM] "AT&T Global IP Network",
http://ipnetwork.bgtmo.ip.att.net/pws/index.html, 2012.
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[mii-tool]
"http://man7.org/linux/man-pages/man8/mii-tool.8.html", .
[netem] "http://www.linuxfoundation.org/collaborate/workgroups/
networking/netem", .
Authors' Addresses
Len Ciavattone
AT&T Labs
200 Laurel Avenue South
Middletown, NJ 07748
USA
Phone: +1 732 420 1239
Email: lencia@att.com
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
Technical University Darmstadt
Darmstadt
Germany
Email: matthias_michael.wieser@stud.tu-darmstadt.de
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