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Internet Engineering Task Force (IETF)                         A. MortonRequest for Comments: 6985                                     AT&T LabsCategory: Informational                                        July 2013ISSN: 2070-1721IMIX Genome: Specification of Variable Packet Sizesfor Additional TestingAbstract   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 a constant packet size   reveal device capabilities but differ significantly from the   conditions encountered in operational deployment, so additional tests   are sometimes conducted with a mixture of packet sizes, or "IMIX"   ("Internet Mix").  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 document defines a way to specify the exact   repeating sequence of packet sizes from the usual set of fixed sizes   and from other forms of mixed-size specification.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Not all documents   approved by the IESG are a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6985.Morton                        Informational                     [Page 1]

RFC 6985                       IMIX Genome                     July 2013Copyright Notice   Copyright (c) 2013 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   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.Table of Contents1. Introduction ....................................................22. Requirements Language ...........................................33. Scope and Goals .................................................34. Specification of the IMIX Genome ................................45. Specification of a Custom IMIX ..................................66. Reporting Long or Pseudorandom Packet Sequences .................76.1. Run-Length Encoding ........................................76.2. Table of Proportions .......................................76.3. Deterministic Algorithm ....................................76.4. Pseudorandom Length Algorithm ..............................86.5. Pseudorandom Sequence Algorithm ............................87. Security Considerations .........................................88. Acknowledgements ................................................89. References ......................................................99.1. Normative References .......................................99.2. Informative References .....................................91.  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.Morton                        Informational                     [Page 2]

RFC 6985                       IMIX Genome                     July 2013   Streams of constant packet size differ significantly from the   conditions encountered in operational deployment, 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 memo 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.   We apply the term "genome" to infer that the entire test packet-size   sequence can be replicated if this information is known -- a parallel   to the information needed for biological replication.   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.  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 inRFC 2119 [RFC2119].3.  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).   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 fromMorton                        Informational                     [Page 3]

RFC 6985                       IMIX Genome                     July 2013   one IMIX to another IMIX -- and certainly no ability to extrapolate   results to other circumstances -- even when the mix varies only   slightly from another IMIX.   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 pseudorandom 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   mailing list [IMIXonList].  The goal is to enable customization with   minimal constraints while fostering repeatable testing once the   fixed-size testing is complete.  Thus, the requirements presented in   this specification, expressed in [RFC2119] terms, are intended for   those performing/reporting laboratory tests to improve clarity and   repeatability.4.  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,   and 16000 bytes).  Note that the 4-octet Ethernet frame check   sequence may fail to detect bit errors in the larger jumbo frames   [Jumbo1] [Jumbo2].                    +--------------+--------------------+                    | 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                  |                    +--------------+--------------------+Morton                        Informational                     [Page 4]

RFC 6985                       IMIX Genome                     July 2013   For example, a five-packet sequence with sizes 64,64,64,1280,1518   would be designated:   IMIX - aaafg   If z (MTU) is used, the tester MUST specify the length of the MTU in   the report.   While this approach allows some flexibility, there are also   constraints.   o  Packet sizes not defined byRFC 2544 would need to be approximated      by those available in the table.   o  The genome for very long sequences can become undecipherable by      humans.   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 in the following general   form:   +-------------------+------------------------+---------------------+   | Source Address +  | Destination Address +  | Corresponding IMIX  |   | Port AND/OR Blade | Port AND/OR Blade      |                     |   +-------------------+------------------------+---------------------+   | 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).Morton                        Informational                     [Page 5]

RFC 6985                       IMIX Genome                     July 20135.  Specification of a Custom IMIX   This section describes how to specify an IMIX with locally selected   packet sizes.   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 - AAAGGMorton                        Informational                     [Page 6]

RFC 6985                       IMIX Genome                     July 20136.  Reporting Long or Pseudorandom Packet Sequences   When the IMIX Genome cannot be used (when the sheer length of the   sequence would make the genome unmanageable), five options are   possible, as noted in the following subsections.6.1.  Run-Length Encoding   When a sequence can be decomposed into a series of short repeating   sequences, then a run-length encoding approach MAY be specified as   shown in the table below (using the single lower-case letter Genome   Codes fromSection 4):           +------------------------------+----------------------+           | Count of Repeating Sequences | Packet-Size Sequence |           +------------------------------+----------------------+           | 20                           | abcd                 |           | 5                            | ggga                 |           | 10                           | dcba                 |           +------------------------------+----------------------+   The run-length encoding approach is also applicable to the custom   IMIX as described inSection 5 (where the single upper-case letter   Genome Codes would be used instead).6.2.  Table of Proportions   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.6.3.  Deterministic Algorithm   If a deterministic packet-size generation method is used (such as a   monotonic increase by 1 octet from start value to MTU), then the   generation algorithm SHOULD be reported.Morton                        Informational                     [Page 7]

RFC 6985                       IMIX Genome                     July 20136.4.  Pseudorandom Length Algorithm   If a pseudorandom 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 pseudorandom generation algorithms and seeds   SHOULD be reported when used.6.5.  Pseudorandom Sequence Algorithm   Finally, we note another possibility: a pseudorandom sequence   generates an index to the table of packet lengths, and the generation   algorithm SHOULD be reported with the results, along with the seed   value if used.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 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   (DUT) or System Under Test (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.  Acknowledgements   Thanks to Sarah Banks, Aamer Akhter, Steve Maxwell, and Scott Bradner   for their reviews and comments.  Ilya Varlashkin suggested the   run-length encoding approach inSection 6.1.Morton                        Informational                     [Page 8]

RFC 6985                       IMIX Genome                     July 20139.  References9.1.  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]  Agilent, "The Journal of Internet Test Methodologies",              September 2007, <http://www.ixiacom.com/pdfs/test_plans/agilent_journal_of_internet_test_methodologies.pdf>.   [IMIXonList]              IETF Benchmarking Methodology Working Group, "Discussion              on IMIX", October 2003, <http://www.ietf.org/mail-archive/web/bmwg/current/msg00691.html>.   [IXIA]     IXIA, "Testing PPPoX and L2TP Broadband Access Devices",              2004, <http://www.ixiacom.com/library/test_plans/display?skey=testing_pppox>.   [Jumbo1]   Dykstra, P., "Gigabit Ethernet Jumbo Frames, and why you              should care", WareOnEarth Communications, Inc., December              1999, <http://sd.wareonearth.com/~phil/jumbo.html>.   [Jumbo2]   Mathis, M., "The Ethernet CRC limits packets to about              12 kBytes. (NOT)", Pittsburgh Supercomputing Center,              April 2003,              <http://staff.psc.edu/mathis/MTU/arguments.html#crc>.   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,              "Architecture for IP Flow Information Export",RFC 5470,              March 2009.   [Spirent]  Spirent, "Test Methodology Journal: IMIX (Internet Mix)              Journal", January 2006, <http://gospirent.com/whitepaper/IMIX%20Test%20Methodolgy%20Journal.pdf>.Morton                        Informational                     [Page 9]

RFC 6985                       IMIX Genome                     July 2013Author'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/Morton                        Informational                    [Page 10]