| Network Working Group | L. Ciavattone |
| Internet-Draft | AT&T Labs |
| Intended status: Informational | R. Geib |
| Expires: October 05, 2014 | Deutsche Telekom |
| A. Morton | |
| AT&T Labs | |
| M. Wieser | |
| Technical University Darmstadt | |
| April 03, 2014 |
Test Plan and Results for Advancing RFC 2680 on the Standards Track
draft-ietf-ippm-testplan-rfc2680-05
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.
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].
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 05, 2014.
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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-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.
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).
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.
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 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].
+------------+ +------------+
| 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 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:
+ 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.
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).
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].
For NetProbe and Perfas+ clock synchronization test results, refer to Section 4 of [RFC6808].
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.
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:
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 Section 11.4 of [RFC2330]. This is equivalent to a 95% confidence factor.
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.
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.
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:
Tests described in this section used:
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.
=======================================
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.
Tests described in this section used:
The netem emulator was set for 0ms constant delay, with 10% loss ratio.
=======================================
> 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.
Tests described in this section used:
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.
=======================================
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.
We conclude that the two implementations are capable of producing equivalent one-way packet loss measurements based on their interpretation of [RFC2680].
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 2.8.2 of [RFC2680].
The common parameters used for tests in this section are:
The netem emulator settings added constant delays as specified in the procedure above.
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 packets designated as lost in one of the test streams (with average delay = 3.091 sec).
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).
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.
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:
=======================================
> 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.
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].
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).
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:
=======================================
> 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.
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).
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
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.
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).
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
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.
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).
[RFC2680] and these should be processed as part of the editing process.
We note that there are at least two Errata on
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.
The security considerations that apply to any active measurement of live networks are relevant here as well. See [RFC4656] and [RFC5357].
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.
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.
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].
[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
[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
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]#
======================================================================
The host interface and configuration is shown 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% =====================================================================
Some sample tc command lines controlling netem and its impairments are given below.