IMIX Genome: Specification of variable packet sizes for additional testing
draft-ietf-bmwg-imix-genome-04

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Network Working Group                                          A. Morton
Internet-Draft                                                 AT&T Labs
Intended status: Informational                         December 12, 2012
Expires: June 15, 2013

   IMIX Genome: Specification of variable packet sizes for additional
                                testing
                     draft-ietf-bmwg-imix-genome-04

Abstract

   Benchmarking Methodologies have always relied on test conditions with
   constant packet sizes, with the goal of understanding what network
   device capability has been tested.  Tests with constant packet size
   reveal device capabilities but differ significantly from the
   conditions encountered in operational deployment, and so additional
   tests are sometimes conducted with a mixture of packet sizes, or
   "IMIX".  The mixture of sizes a networking device will encounter is
   highly variable and depends on many factors.  An IMIX suited for one
   networking device and deployment will not be appropriate for another.
   However, the mix of sizes may be known and the tester may be asked to
   augment the fixed size tests.  To address this need, and the
   perpetual goal of specifying repeatable test conditions, this draft
   defines a way to specify the exact repeating sequence of packet sizes
   from the usual set of fixed sizes, and other forms of mixed size
   specification.

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

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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on June 15, 2013.

Copyright Notice

   Copyright (c) 2012 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Scope and Goals  . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Specification of the IMIX Genome . . . . . . . . . . . . . . .  5
   4.  Specification of a Custom IMIX . . . . . . . . . . . . . . . .  7
   5.  Reporting Long or Pseudo-Random Packet Sequences . . . . . . .  7
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     9.1.  Normative References . . . . . . . . . . . . . . . . . . .  9
     9.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

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1.  Introduction

   This memo defines a method to unambiguously specify the sequence of
   packet sizes used in a load test.

   Benchmarking Methodologies [RFC2544] have always relied on test
   conditions with constant packet 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.

   Streams of constant packet size differ significantly from the
   conditions encountered in operational deployment, and so additional
   tests are sometimes conducted with a mixture of packet sizes.  The
   set of sizes used is often called an Internet Mix, or "IMIX"
   [Spirent], [IXIA], [Agilent].

   The mixture of sizes a networking device will encounter is highly
   variable and depends on many factors.  An IMIX suited for one
   networking device and deployment will not be appropriate for another.
   However, the mix of sizes may be known and the tester may be asked to
   augment the fixed size tests.  The references above cite the original
   studies and their methodologies.  Similar methods can be used to
   determine new size mixes present on a link or network.  We note that
   the architecture for IP Flow Information Export [RFC5470] provides
   one method to gather packet size information on private networks.

   To address this need, and the perpetual goal of specifying repeatable
   test conditions, this draft proposes a way to specify the exact
   repeating sequence of packet sizes from the usual set of fixed sizes:
   the IMIX Genome.  Other, less exact forms of size specification are
   also recommended for extremely complicated or customized size mixes.

   This memo takes the position that it cannot be proven for all
   circumstances that the sequence of packet sizes does not affect the
   test result, thus a standardized specification of sequence is
   valuable.

2.  Scope and Goals

   This memo defines a method to unambiguously specify the sequence of
   packet sizes that have been used in a load test, assuming that a
   relevant mix of sizes is known to the tester and the length of the
   repeating sequence is not very long (<100 packets).

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   The IMIX Genome will allow an exact sequence of packet sizes to be
   communicated as a single-line name, resolving the current ambiguity
   with results that simply refer to "IMIX".  This aspect is critical
   because no ability has been demonstrated to extrapolate results from
   one IMIX to another IMIX, even when the mix varies only slightly from
   another IMIX, and certainly no ability to extrapolate results to
   other circumstances.

   While documentation of the exact sequence is ideal, the memo also
   covers the case where the sequence of sizes is very long or may be
   generated by a pseudo-random process.

   It is a colossal non-goal to standardize one or more versions of the
   IMIX.  This topic has been discussed on many occasions on the bmwg-
   list[IMIXonList].  The goal is to enable customization with minimal
   constraints while fostering repeatable testing once the fixed size
   testing is complete.

3.  Specification of the IMIX Genome

   The IMIX Genome is specified in the following format:

   IMIX - 123456...x

   where each number is replaced by the letter corresponding to the size
   of the packet at that position in the sequence.  The following table
   gives the letter encoding for the [RFC2544] standard sizes (64, 128,
   256, 512, 1024, 1280, and 1518 bytes) and "jumbo" sizes (2112, 9000,
   16000).  Note that the 4 octet Ethernet frame check sequence may fail
   to detect bit errors in the larger jumbo frames, see [jumbo].

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                   +-------------+--------------------+
                   | Size, bytes | Genome Code Letter |
                   +-------------+--------------------+
                   | 64          | a                  |
                   | 128         | b                  |
                   | 256         | c                  |
                   | 512         | d                  |
                   | 1024        | e                  |
                   | 1280        | f                  |
                   | 1518        | g                  |
                   | 2112        | h                  |
                   | 9000        | i                  |
                   | 16000       | j                  |
                   | MTU         | z                  |
                   +-------------+--------------------+

   For example: a five packet sequence with sizes 64,64,64,1280,1518
   would be designated:

   IMIX - aaafg

   While this approach allows some flexibility, there are also
   constraints.

   o  Non-RFC2544 packet sizes would need to be approximated by those
      available in the table.

   o  The Genome for very long sequences can become undecipherable by
      humans.

   o  z=MTU is seen as valuable, so MTU MUST be specified if used.

   o  "jumbo" sizes are included.

   Some questions testers must ask and answer when using the IMIX Genome
   are:

   1.  Multiple Source-Destination Address Pairs: is the IMIX sequence
       applicable to each pair, across multiple pairs in sets, or across
       all pairs?

   2.  Multiple Tester Ports: is the IMIX sequence applicable to each
       port, across multiple ports in sets, or across all ports?

   The chosen configuration would be expressed the following general
   form:

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   +-----------------------+-------------------------+-----------------+
   | Source                | Destination             | Corresponding   |
   | Address/Port/Blade    | Address/Port/Blade      | IMIX            |
   +-----------------------+-------------------------+-----------------+
   | x.x.x.x Blade2        | y.y.y.y Blade3          | IMIX - aaafg    |
   +-----------------------+-------------------------+-----------------+

   where testers can specify the IMIX used between any two entities in
   the test architecture (and Blade is a component in a multi-component
   device chassis).

4.  Specification of a Custom IMIX

   The Custom IMIX is specified in the following format:

   CUSTOM IMIX - 123456...x

   where each number is replaced by the letter corresponding to the size
   of the packet at that position in the sequence.  The tester MUST
   complete the following table, giving the letter encoding for each
   size used, where each set of three lower-case letters would be
   replaced by the integer size in octets.

                   +-------------+--------------------+
                   | Size, bytes | Custom Code Letter |
                   +-------------+--------------------+
                   | aaa         | A                  |
                   | bbb         | B                  |
                   | ccc         | C                  |
                   | ddd         | D                  |
                   | eee         | E                  |
                   | fff         | F                  |
                   | ggg         | G                  |
                   | etc.        | up to Z            |
                   +-------------+--------------------+

   For example: a five packet sequence with sizes
   aaa=64,aaa=64,aaa=64,ggg=1020,ggg=1020 would be designated:

   CUSTOM IMIX - AAAGG

5.  Reporting Long or Pseudo-Random Packet Sequences

   When the IMIX-Genome cannot be used (when the sheer length of the
   sequence would make the genome unmanageable), two options are
   possible.  When a sequence can be decomposed into a series of short

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   repeating sequences, then a run-length encoding approach MAY be used
   as shown below:

          +------------------------------+----------------------+
          | Count of Repeating Sequences | Packet Size Sequence |
          +------------------------------+----------------------+
          | 20                           | abcd                 |
          | 5                            | ggga                 |
          | 10                           | dcba                 |
          +------------------------------+----------------------+

   When the sequence is designed to vary within some proportional
   constraints, a table simply giving the proportions of each size MAY
   be used instead.

      +-----------+---------------------+---------------------------+
      | IP Length | Percentage of Total | Length(s) at other layers |
      +-----------+---------------------+---------------------------+
      | 64        | 23                  | 82                        |
      | 128       | 67                  | 146                       |
      | 1000      | 10                  | 1018                      |
      +-----------+---------------------+---------------------------+

   Note that the table of proportions also allows non-standard packet
   sizes, but trades the short genome specification and ability to
   specify the exact sequence for other flexibilities.

   If a pseudo-random length generation capability is used, then the
   generation algorithm SHOULD be reported with the results along with
   the seed value used.  We also recognize the opportunity to randomize
   inter-packet spacing from a test sender as well as the size, and both
   spacing and length pseudo-random generation algorithms and seeds
   SHOULD be reported when used.

6.  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.

   Further, benchmarking is performed on a "black-box" basis, relying

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   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.

7.  IANA Considerations

   This memo makes no requests of IANA, and hopes that IANA will leave
   it alone as well.

8.  Acknowledgements

   Thanks to Sarah Banks, Aamer Akhter, Steve Maxwell, and Scott Bradner
   for their reviews and comments.  Ilya Varlashkin suggested the run-
   length coding approach in Section 5.

9.  References

9.1.  Normative References

   [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.

9.2.  Informative References

   [Agilent]  http://www.ixiacom.com/pdfs/test_plans/
              agilent_journal_of_internet_test_methodologies.pdf, "The
              Journal of Internet Test Methodologies", 2007.

   [IMIXonList]
              http://www.ietf.org/mail-archive/web/bmwg/current/
              msg00691.html, "Discussion on IMIX", 2003.

   [IXIA]     http://www.ixiacom.com/library/test_plans/
              display?skey=testing_pppox, "Library: Test Plans", 2010.

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture for IP Flow Information Export", RFC 5470,
              March 2009.

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   [Spirent]  http://gospirent.com/whitepaper/
              IMIX%20Test%20Methodolgy%20Journal.pdf, "Test Methodology
              Journal: IMIX (Internet Mix) Journal",   2006.

   [jumbo]    http://www.ietf.org/mail-archive/web/bmwg/current/
              msg00691.html, "Discussion of Jumbo Packets and FCS
              Failure, see http://sd.wareonearth.com/~phil/jumbo.html
              and http://staff.psc.edu/mathis/MTU/arguments.html#crc".

Author's Address

   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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