Internet DRAFT - draft-morton-bmwg-b2b-frame
draft-morton-bmwg-b2b-frame
Network Working Group A. Morton
Internet-Draft AT&T Labs
Updates: 2544 (if approved) March 2, 2019
Intended status: Informational
Expires: September 3, 2019
Updates for the Back-to-back Frame Benchmark in RFC 2544
draft-morton-bmwg-b2b-frame-05
Abstract
Fundamental Benchmarking Methodologies for Network Interconnect
Devices of interest to the IETF are defined in RFC 2544. This memo
updates the procedures of the test to measure the Back-to-back frames
Benchmark of RFC 2544, based on further experience.
This memo updates Section 26.4 of RFC 2544.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14[RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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 https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 3, 2019.
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Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Scope and Goals . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Prerequisites . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Back-to-back Frames . . . . . . . . . . . . . . . . . . . . . 6
5.1. Preparing the list of Frame sizes . . . . . . . . . . . . 6
5.2. Test for a Single Frame Size . . . . . . . . . . . . . . 6
5.3. Test Repetition . . . . . . . . . . . . . . . . . . . . . 7
5.4. Benchmark Calculations . . . . . . . . . . . . . . . . . 7
6. Reporting . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
10.1. Normative References . . . . . . . . . . . . . . . . . . 10
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
The IETF's fundamental Benchmarking Methodologies are defined
in[RFC2544], supported by the terms and definitions in [RFC1242], and
[RFC2544] actually obsoletes an earlier specification, [RFC1944].
Over time, the benchmarking community has updated [RFC2544] several
times, including the Device Reset Benchmark [RFC6201], and the
important Applicability Statement [RFC6815] concerning use outside
the Isolated Test Environment (ITE) required for accurate
benchmarking. Other specifications implicitly update [RFC2544], such
as the IPv6 Benchmarking Methodologies in [RFC5180].
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Recent testing experience with the Back-to-back Frame test and
Benchmark in Section 26.4 of [RFC2544] indicates that an update is
warranted [OPNFV-2017] [VSPERF-b2b]. This memo describes the
rationale and provides the updated method.
[RFC2544] provides its own Requirements Language consistent with
[RFC2119], since [RFC1944] predates [RFC2119]. Thus, the
requirements presented in this memo are expressed in [RFC2119] terms,
and intended for those performing/reporting laboratory tests to
improve clarity and repeatability, and for those designing devices
that facilitate these tests.
2. Scope and Goals
The scope of this memo is to define an updated method to
unambiguously perform tests, measure the benchmark(s), and report the
results for Back-to-back Frames (presently described Section 26.4 of
[RFC2544]).
The goal is to provide more efficient test procedures where possible,
and to expand reporting with additional interpretation of the
results. The tests described in this memo address the cases where
the maximum frame rate of a single ingress port cannot be transferred
to an egress port loss-free (for some frame sizes of interest).
[RFC2544] Benchmarks rely on test conditions with constant frame
sizes, with the goal of understanding what network device capability
has been tested. Tests with the smallest size stress the header
processing capacity, and tests with the largest size stress the
overall bit processing capacity. Tests with sizes in-between may
determine the transition between these two capacities. However,
conditions simultaneously sending multiple frame sizes, such as those
described in [RFC6985], MUST NOT be used in Back-to-back Frame
testing.
Section 3 of [RFC8239] describes buffer size testing for physical
networking devices in a Data Center. The [RFC8239] methods measure
buffer latency directly with traffic on multiple ingress ports that
overload an egress port on the Device Under Test (DUT), and are not
subject to the revised calculations presented in this memo.
3. Motivation
Section 3.1 of [RFC1242] describes the rationale for the Back-to-back
Frames Benchmark. To summarize, there are several reasons that
devices on a network produce bursts of frames at the minimum allowed
spacing, and it is therefore worthwhile to understand the Device
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Under Test (DUT) limit on the length of such bursts in practice.
Also, [RFC1242] states:
"Tests of this parameter are intended to determine the extent
of data buffering in the device."
After this test was defined, there have been occasional discussions
of the stability and repeatability of the results, both over time and
across labs. Fortunately, the Open Platform for Network Function
Virtualization (OPNFV) VSPERF project's Continuous Integration (CI)
testing routinely repeats Back-to-back Frame tests to verify that
test functionality has been maintained through development of the
test control programs. These tests were used as a basis to evaluate
stability and repeatability, even across lab set-ups when the test
platform was migrated to new DUT hardware at the end of 2016.
When the VSPERF CI results were examined [VSPERF-b2b], several
aspects of the results were considered notable:
1. Back-to-back Frame Benchmark was very consistent for some fixed
frame sizes, and somewhat variable for others.
2. The Back-to-back Frame length reported for large frame sizes was
unexpectedly long, and no explanation or measurement limit
condition was indicated.
3. Calculation of the extent of buffer time in the DUT helped to
explain the results observed with all frame sizes (for example,
some frame sizes cannot exceed the frame header processing rate
of the DUT and therefore no buffering occurs, therefore the
results depended on the test equipment and not the DUT).
4. It was found that the actual buffer time in the DUT could be
estimated using results from the Throughput tests conducted
according to Section 26.1 of [RFC2544], because it appears that
the DUT's frame processing rate may tend to increase the
estimate.
Further, if the Throughput tests of Section 26.1 of [RFC2544] are
conducted as a prerequisite test, the number of frame sizes required
for Back-to-back Frame Benchmarking can be reduced to one or more of
the small frame sizes, or the results for large frame sizes can be
noted as invalid in the results if tested anyway (these are the frame
sizes for which the back-to-back frame rate cannot exceed the exceed
the frame header processing rate of the DUT and no buffering occurs).
[VSPERF-b2b] provides the details of the calculation to estimate the
actual buffer storage available in the DUT, using results from the
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Throughput tests for each frame size, and the maximum theoretical
frame rate for the DUT links (which constrain the minimum frame
spacing). We present some of these details here.
The simplified model used in these calculations for the DUT includes
a packet header processing function with limited rate of operation,
as shown below:
|------------ DUT --------|
Generator -> Ingress -> Buffer -> HeaderProc -> Egress -> Receiver
So, in the back2back frame testing:
1. The Ingress burst arrives at Max Theoretical Frame Rate, and
initially the frames are buffered
2. The packet header processing function (HeaderProc) operates at
approximately the "Measured Throughput", removing frames from the
buffer
3. Frames that have been processed are clearly not in the buffer, so
the Corrected DUT buffer time equation (Section 5.4) estimates
and removes the frames that the DUT forwarded on Egress during
the burst.
Knowledge of approximate buffer storage size (in time or bytes) may
be useful to estimate whether frame losses will occur if DUT
forwarding is temporarily suspended in a production deployment, due
to an unexpected interruption of frame processing (an interruption of
duration greater than the estimated buffer would certainly cause lost
frames).
The presentation of OPNFV VSPERF evaluation and development of
enhanced search alogorithms [VSPERF-BSLV] was discussed at IETF-102.
The enhancements are intended to compensate for transient inerrrupts
that may cause loss at near-Throughput levels of offered load.
Subsequent analysis of the results indicates that buffers within the
DUT can compensate for some interrupts, and this finding increases
the importance of the Back-to-back frame characterization described
here.
4. Prerequisites
The Test Setup MUST be consistent with Figure 1 of [RFC2544], or
Figure 2 when the tester's sender and recover are different devices.
Other mandatory testing aspects described in [RFC2544] MUST be
included, unless explicitly modified in the next section.
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The ingress and egress link speeds and link layer protocols MUST be
specified and used to compute the maximum theoretical frame rate when
respecting the minimum inter-frame gap.
The test results for the Throughput Benchmark conducted according to
Section 26.1 of [RFC2544] for all [RFC2544]-RECOMMENDED frame sizes
MUST be available to reduce the tested frame size list, or to note
invalid results for individual frame sizes (because the burst length
may be essentially infinite for large frame sizes).
Note that:
o the Throughput and the Back-to-back Frame measurement
configuration traffic characteristics (unidirectional or bi-
directional) MUST match.
o the Throughput measurement MUST be under zero-loss conditions,
according to Section 26.1 of [RFC2544].
The Back-to-back Benchmark described in Section 3.1 of [RFC1242] MUST
be measured directly by the tester. Additional measurement
requirements are described below in Section 5.
5. Back-to-back Frames
Objective: To characterize the ability of a DUT to process back-to-
back frames as defined in [RFC1242].
The Procedure follows.
5.1. Preparing the list of Frame sizes
From the list of RECOMMENDED Frame sizes (Section 9 of [RFC2544]),
select the subset of Frame sizes whose measured Throughput was less
than the maximum theoretical Frame Rate. These are the only Frame
sizes where it is possible to produce a burst of frames that cause
the DUT buffers to fill and eventually overflow, producing one or
more discarded frames.
5.2. Test for a Single Frame Size
Each trial in the test requires the tester to send a burst of frames
(after idle time) with the minimum inter-frame gap, and to count the
corresponding frames forwarded by the DUT.
The duration of the trial MUST be at least 2 seconds, to allow DUT
buffers to deplete.
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If all frames have been received, the tester increases the length of
the burst according to the search algorithm and performs another
trial.
If the received frame count is less than the number of frames in the
burst, then the limit of DUT processing and buffering may have been
exceeded, and the burst length is determined by the search algorithm
for the next trial.
Classic search algorithms have been adapted for use in benchmarking,
where the search requires discovery of a pair of outcomes, one with
no loss and another with loss, at load conditions within the
acceptable tolerance. Also for conditions encountered when
benchmarking the Infrastructure for Network Function Virtualization
require algorithm enhancement. Fortunately, the adaptation of Binary
Search, and an enhanced Binary Search with Loss Verification have
been specified in [TST009]. These alogorithms (see clause 12.3) can
easily be used for Back-to-back Frame benchmarking by replacing the
Offered Load level with burst length in frames. [TST009] Annex B
describes the theory behind the enhanced Binary Search algorithm.
Either the [TST009] Binary Search or Binary Search with Loss
Verification algorithms MUST be used, and input parameters to the
algorithm(s) MUST be reported.
The Back-to-back Frame value is the longest burst of frames that the
DUT can successfully process and buffer without frame loss, as
determined from the series of trials. The tester may impose a
(configurable) minimum step size for burst length, and the step size
MUST be reported with the results (as this influences the accuracy
and variation of test results).
5.3. Test Repetition
The test MUST be repeated N times for each frame size in the subset
list, and each Back-to-back Frame value made available for further
processing (below).
5.4. Benchmark Calculations
For each Frame size, calculate the following summary statistics for
Back-to-back Frame values over the N tests:
o Average (Benchmark)
o Minimum
o Maximum
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o Standard Deviation
Further, calculate the Implied DUT Buffer Time and the Corrected DUT
Buffer Time in seconds, as follows:
Implied DUT Buffer Time =
Average num of Back-to-back Frames / Max Theoretical Frame Rate
The formula above is simply expressing the Burst of Frames in units
of time.
The next step is to apply a correction factor that accounts for the
DUT's frame forwarding operation during the test (assuming a simple
model of the DUT composed of a buffer and a forwarding function).
Corrected DUT Buffer Time =
Measured Throughput
= Implied DUT Buffer Time * --------------------------
Max Theoretical Frame Rate
where:
1. The "Measured Throughput" is the RFC2544 Throughput Benchmark for
the frame size tested, and MUST be expressed in Frames per second
in this equation.
2. The "Max Theoretical Frame Rate" is a calculated value for the
interface speed and link layer technology used, and MUST be
expressed in Frames per second in this equation.
The term on the far right in the formula for Corrected DUT Buffer
Time accounts for all the frames in the Burst that were transmitted
by the DUT *while the Burst of frames were sent in*. So, these frames
are not in the Buffer and the Buffer size is more accurately
estimated by excluding them.
6. Reporting
The back-to-back results SHOULD be reported in the format of a table
with a row for each of the tested frame sizes. There SHOULD be
columns for the frame size and for the resultant average frame count
for each type of data stream tested.
The number of tests Averaged for the Benchmark, N, MUST be reported.
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The Minimum, Maximum, and Standard Deviation across all complete
tests SHOULD also be reported.
The Corrected DUT Buffer Time SHOULD also be reported.
If the tester operates using a maximum burst length in frames, then
this maximum length SHOULD be reported.
+--------------+----------------+----------------+------------------+
| Frame Size, | Ave B2B | Min,Max,StdDev | Corrected Buff |
| octets | Length, frames | | Time, Sec |
+--------------+----------------+----------------+------------------+
| 64 | 26000 | 25500,27000,20 | 0.00004 |
+--------------+----------------+----------------+------------------+
Back-to-Back Frame Results
Static and configuration parameters:
Number of test repetitions, N
Minimum Step Size (during searches), in frames.
7. Security Considerations
Benchmarking activities as described in this memo are limited to
technology characterization using controlled stimuli in a laboratory
environment, with dedicated address space and the other constraints
[RFC2544].
The benchmarking network topology will be an independent test setup
and MUST NOT be connected to devices that may forward the test
traffic into a production network, or misroute traffic to the test
management network. See [RFC6815].
Further, benchmarking is performed on a "black-box" basis, relying
solely on measurements observable external to the DUT/SUT.
Special capabilities SHOULD NOT exist in the DUT/SUT specifically for
benchmarking purposes. Any implications for network security arising
from the DUT/SUT SHOULD be identical in the lab and in production
networks.
8. IANA Considerations
This memo makes no requests of IANA.
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9. Acknowledgements
Thanks to Trevor Cooper, Sridhar Rao, and Martin Klozik of the VSPERF
project for many contributions to the testing [VSPERF-b2b]. Yoshiaki
Itou has also investigated the topic, and made useful suggestions.
10. References
10.1. Normative References
[RFC1242] Bradner, S., "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, DOI 10.17487/RFC1242,
July 1991, <https://www.rfc-editor.org/info/rfc1242>.
[RFC1944] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 1944,
DOI 10.17487/RFC1944, May 1996,
<https://www.rfc-editor.org/info/rfc1944>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544,
DOI 10.17487/RFC2544, March 1999,
<https://www.rfc-editor.org/info/rfc2544>.
[RFC5180] Popoviciu, C., Hamza, A., Van de Velde, G., and D.
Dugatkin, "IPv6 Benchmarking Methodology for Network
Interconnect Devices", RFC 5180, DOI 10.17487/RFC5180, May
2008, <https://www.rfc-editor.org/info/rfc5180>.
[RFC6201] Asati, R., Pignataro, C., Calabria, F., and C. Olvera,
"Device Reset Characterization", RFC 6201,
DOI 10.17487/RFC6201, March 2011,
<https://www.rfc-editor.org/info/rfc6201>.
[RFC6815] Bradner, S., Dubray, K., McQuaid, J., and A. Morton,
"Applicability Statement for RFC 2544: Use on Production
Networks Considered Harmful", RFC 6815,
DOI 10.17487/RFC6815, November 2012,
<https://www.rfc-editor.org/info/rfc6815>.
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[RFC6985] Morton, A., "IMIX Genome: Specification of Variable Packet
Sizes for Additional Testing", RFC 6985,
DOI 10.17487/RFC6985, July 2013,
<https://www.rfc-editor.org/info/rfc6985>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
10.2. Informative References
[OPNFV-2017]
Cooper, T., Morton, A., and S. Rao, "Dataplane
Performance, Capacity, and Benchmarking in OPNFV", June
2017,
<https://wiki.opnfv.org/download/attachments/10293193/
VSPERF-Dataplane-Perf-Cap-Bench.pptx?api=v2>.
[RFC8239] Avramov, L. and J. Rapp, "Data Center Benchmarking
Methodology", RFC 8239, DOI 10.17487/RFC8239, August 2017,
<https://www.rfc-editor.org/info/rfc8239>.
[TST009] ETSI Network Function Virtualization ISG, "ETSI GS NFV-TST
009 V3.1.1 (2018-10), "Network Functions Virtualisation
(NFV) Release 3; Testing; Specification of Networking
Benchmarks and Measurement Methods for NFVI"", October
2018, <https://www.etsi.org/deliver/etsi_gs/NFV-
TST/001_099/009/03.01.01_60/gs_NFV-TST009v030101p.pdf>.
[VSPERF-b2b]
Morton, A., "Back2Back Testing Time Series (from CI)",
June 2017, <https://wiki.opnfv.org/display/vsperf/
Traffic+Generator+Testing#TrafficGeneratorTesting-
AppendixB:Back2BackTestingTimeSeries(fromCI)>.
[VSPERF-BSLV]
Morton, A. and S. Rao, "Evolution of Repeatability in
Benchmarking: Fraser Plugfest (Summary for IETF BMWG)",
July 2018,
<https://datatracker.ietf.org/meeting/102/materials/
slides-102-bmwg-evolution-of-repeatability-in-
benchmarking-fraser-plugfest-summary-for-ietf-bmwg-00>.
Author's Address
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Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
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