Network Working Group S. Bradner
Internet-Draft Harvard University
Intended status: Informational K. Dubray
Expires: February 7, 2012 Juniper Networks
J. McQuaid
Turnip Video
A. Morton
AT&T Labs
August 6, 2011
RFC 2544 Applicability Statement: Use on Real-World Networks Considered
Harmful
draft-ietf-bmwg-2544-as-00
Abstract
Benchmarking Methodology Working Group (BMWG) has been developing key
performance metrics and laboratory test methods since 1990, and
continues this work at present. Recent application of the methods
beyond their intended scope is cause for concern. This memo
clarifies the scope of RFC 2544 and other benchmarking work for the
IETF community.
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
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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 February 7, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Scope and Goals . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The Concept of an Isolated Test Environment . . . . . . . . . . 4
4. Why RFC 2544 Methods are intended for ITE . . . . . . . . . . . 4
4.1. Experimental Control, Repeatability, and Accuracy . . . . . 4
4.2. Containment of Implementation Failure Impact . . . . . . . 5
5. Advisory on RFC 2544 Methods in Real-world Networks . . . . . . 5
6. What to do without RFC 2544? . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
This memo clarifies the scope of RFC 2544 [RFC2544], and other
benchmarking work for the IETF community.
Benchmarking Methodologies (beginning with [RFC2544]) have always
relied on test conditions that can only be reliably produced in the
laboratory. Thus it was surprising to find that this foundation
methodology was being cited in several unintended applications, such
as:
1. Validation of telecommunication service configuration, such as
the Committed Information Rate (CIR).
2. Validation of performance metrics in a telecommunication Service
Level Agreement (SLA), such as frame loss and latency.
3. As an integral part of telecommunication service activation
testing, where traffic that shares network resources with the
test might be adversely affected.
Above, we distinguish "telecommunication service" (where a network
service provider contracts with a customer to transfer information
between specified interfaces at different geographic locations in the
real world) from the generic term "service". Also, we use the term
"real-world networks" to refer to production networks carrying live
user traffic.
Although RFC 2544 is held up as the standard reference for such
testing, we believe that the actual methods used vary from RFC 2544
in significant ways. Since the only citation is to RFC 2544, the
modifications are opaque to the standards community and to users in
general (an undesirable situation).
To directly address this situation, the past and present Chairs of
the IETF Benchmarking Methodology Working Group (BMWG) have prepared
this Applicability Statement for RFC 2544.
1.1. 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].
2. Scope and Goals
This memo clarifies the scope of [RFC2544], with the goal to provide
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guidance to the community on its applicability, which is limited to
laboratory testing.
3. The Concept of an Isolated Test Environment
An Isolated Test Environment (ITE) used with [RFC2544] methods (as
illustrated in Figures 1 through 3 of [RFC2544])has the ability to:
o contain the test streams to paths within the desired set-up
o prevent non-test traffic from traversing the test set-up
These features allow unfettered experimentation, while at the same
time protecting equipment management LANs and other production
networks from the unwanted effects of the test traffic.
4. Why RFC 2544 Methods are intended for ITE
The following sections discuss some of the reasons why RFC 2544
[RFC2544] methods were intended only for isolated laboratory use, and
the difficulties of applying these methods outside the lab
environment.
4.1. Experimental Control, Repeatability, and Accuracy
All of the tests described in RFC 2544 assume that the tester and
device under test are the only devices on the networks that are
transmitting data. The presence of other unwanted traffic on the
network would mean that the specified test conditions have not been
achieved.
Assuming that the unwanted traffic appears in variable amounts over
time, the repeatability of any test result will likely depend to some
degree on the unwanted traffic.
The presence of unwanted or unknown traffic makes accurate,
repeatable, and consistent measurements of the performance of the
device under test very unlikely, since the actual test conditions
will not be reported.
For example, the RFC 2544 Throughput Test attempts to characterize a
maximum reliable load, thus there will be testing above the maximum
that causes packet/frame loss. Any other sources of traffic on the
network will cause packet loss to occur at a tester data rate lower
than the rate that would be achieved without the extra traffic.
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4.2. Containment of Implementation Failure Impact
RFC 2544 methods, specifically to determine Throughput as defined in
[RFC1242] and other benchmarks, are designed to overload the
resources of the device under test, and may cause failure modes in
the device under test. Since failures can become the root cause of
more wide-spread failure, it is clearly desirable to contain all DUT
traffic within the ITE.
In addition, such testing can have a negative affect on any traffic
which shares resources with the test stream(s) since, in most cases,
the traffic load will be close to the capacity of the network links.
Appendix C.2.2 of [RFC2544] (as adjusted by errata) gives the private
IPv4 address range for testing:
"...The network addresses 198.18.0.0 through 198.19.255.255 have been
assigned to the BMWG by the IANA for this purpose. This assignment
was made to minimize the chance of conflict in case a testing device
were to be accidentally connected to part of the Internet. The
specific use of the addresses is detailed below."
In other words, devices operating on the Internet may be configured
to discard any traffic they observe in this address range, as it is
intended for laboratory ITE use only. Thus, testers using the
assigned testing address ranges MUST NOT be connected to the
Internet.
We note that a range of IPv6 addresses has been assigned to BMWG for
laboratory test purposes, in [RFC5180]. Also, the strong statements
in the Security Considerations Section of this memo make the scope
even more clear; this is now a standard fixture of all BMWG memos.
5. Advisory on RFC 2544 Methods in Real-world Networks
The tests in [RFC2544] were designed to measure the performance of
network devices, not of networks, and certainly not production
networks carrying user traffic on shared resources. There will be
unanticipated difficulties when applying these methods outside the
lab environment.
Operating test equipment on real-world networks according to the
methods described in [RFC2544], where overload is a required outcome,
would no doubt be harmful to user traffic performance. These tests
MUST NOT be used on active networks. And as discussed above, the
tests will never produce a reliable or accurate benchmarking result.
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[RFC2544] methods have never been validated on a network path, even
when that path is not part of a production network and carrying no
other traffic. It is unknown whether the tests can be used to
measure valid and reliable performance of a multi-device, multi-
network path. It is possible that some of the tests may prove to be
valid in some path scenarios, but that work has not been done or has
not been shared with the IETF community. Thus, such testing is
contra-indicated by the BMWG.
6. What to do without RFC 2544?
The IETF has addressed the problem of real-world network performance
measurement by chartering a different working group: IP Performance
Metrics (IPPM). This working group has developed a set of standard
metrics to assess the quality, performance, and reliability of
Internet packet transfer services. These metrics can be measured by
network operators, end users, or independent testing groups. We note
that some IPPM metrics differ from RFC 2544 metrics with similar
names, and there is likely to be confusion if the details are
ignored.
IPPM has not standardized methods for raw capacity measurement of
Internet paths. Such testing needs to adequately consider the strong
possibility for degradation to any other traffic that may be present
due to congestion. There are no specific methods proposed for
activation of a packet transfer service in IPPM.
Other standards may help to fill gaps in telecommunication service
testing. For example, the IETF has many standards intended to assist
with network operation, administration and maintenance (OAM), the
ITU-T Study Group 12 has a recommendation on service activation test
methodology.
The world will not spin off axis while waiting for appropriate and
standardized methods to emerge from the consensus process.
7. Security Considerations
This Applicability Statement is also intended to help preserve the
security of the Internet by clarifying that the scope of [RFC2544]
and other BMWG memos are all limited to testing in laboratory ITE,
thus avoiding accidental Denial of Service attacks or congestion due
to high traffic volume test streams.
All Benchmarking activities are limited to technology
characterization using controlled stimuli in a laboratory
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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.
Further, benchmarking is performed on a "black-box" basis, relying
solely on measurements observable external to the device under test/
system under test (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, and hopes that IANA will leave
it alone as well.
9. Acknowledgements
Thanks to Matt Zekauskas, Bill Cerveny, Barry Constantine, and Curtis
Villamizar for reading and suggesting improvements for this memo.
10. References
10.1. Normative References
[RFC1242] Bradner, S., "Benchmarking terminology for network
interconnection devices", RFC 1242, July 1991.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2544] Bradner, S. and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC5180] Popoviciu, C., Hamza, A., Van de Velde, G., and D.
Dugatkin, "IPv6 Benchmarking Methodology for Network
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Interconnect Devices", RFC 5180, May 2008.
10.2. Informative References
Authors' Addresses
Scott Bradner
Harvard University
29 Oxford St.
Cambridge, MA 02138
USA
Phone: +1 617 495 3864
Fax:
Email: sob@harvard.edu
URI: http://www.sobco.com
Kevin Dubray
Juniper Networks
Phone:
Fax:
Email: kdubray@juniper.net
URI:
Jim McQuaid
Turnip Video
6 Cobbleridge Court
Durham, North Carolina 27713
USA
Phone: +1 919-619-3220
Fax:
Email: jim@turnipvideo.com
URI: www.turnipvideo.com
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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
URI: http://home.comcast.net/~acmacm/
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