Internet Engineering Task Force                               Jan Novak
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Informational
Expires: 9 12 September, 2012                                  9                                12 March 2012

         IP Flow Information Accounting and Export Benchmarking


   This document provides a methodology and framework for quantifying
   the performance impact of monitoring of IP flows on a network device
   and export of this information to a collector. It identifies the rate
   at which the IP flows are created, expired, and successfully exported
   as a new performance metric in combination with traditional
   throughput. The metric is only applicable to the devices compliant
   with the Architecture for IP Flow Information Export [RFC5470].

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
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Conventions used in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
"OPTIONAL" in this document are to be interpreted as described
in RFC 2119 [RFC2119].

Table of Contents

   1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . 3
   2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
      2.1 Existing Terminology. . . . . . . . . . . . . . . . . . . 4
      2.2 New Terminology . . . . . . . . . . . . . . . . . . . . . 4
   3. Flow Monitoring Performance Benchmark . . . . . . . . . . . . 6
      3.1 Definition. . . . . . . . . . . . . . . . . . . . . . . . 6
      3.2 Device Applicability. . . . . . . . . . . . . . . . . . . 6
      3.3 Measurement Concept . . . . . . . . . . . . . . . . . . . 7
      3.4 The Measurement Procedure Overview. . . . . . . . . . . . 8
   4. Measurement Set-Up. . . . . . . . . . . . . . . . . . . . . . 9
      4.1 Measurement Topology. . . . . . . . . . . . . . . . . . . 9
      4.2 Base DUT Set Up. . . . . . . . . . . . . . . . . . . . . 11
      4.3 Flow Monitoring Configuration. . . . . . . . . . . . . . 11
      4.4 Collector. . . . . . . . . . . . . . . . . . . . . . . . 16
      4.5 Sampling . . . . . . . . . . . . . . . . . . . . . . . . 16
      4.6 Frame Formats. . . . . . . . . . . . . . . . . . . . . . 16
      4.7 Frame Sizes. . . . . . . . . . . . . . . . . . . . . . . 16
      4.8 Flow Export Data Packet Sizes. . . . . . . . . . . . . . 16
      4.9 Illustrative Test Set-up Examples. . . . . . . . . . . . 17
   5. Flow Monitoring Throughput Measurement Methodology . . . . . 18
      5.1 Flow Monitoring Configuration. . . . . . . . . . . . . . 19
      5.2 Traffic Configuration. . . . . . . . . . . . . . . . . . 20
      5.3 Cache Population . . . . . . . . . . . . . . . . . . . . 20
      5.4 Measurement Time Interval. . . . . . . . . . . . . . . . 20
      5.5 Flow Export Rate Measurement . . . . . . . . . . . . . . 21
      5.6 The Measurement Procedure. . . . . . . . . . . . . . . . 22
   6. RFC2544 Measurements . . . . . . . . . . . . . . . . . . . . 23
      6.1 Flow Monitoring Configuration. . . . . . . . . . . . . . 23
      6.2 Measurements With the Flow Monitoring Throughput Set-up. 24
      6.3 Measurements With Fixed Flow Export Rate . . . . . . . . 24
   7. Flow Monitoring Accuracy . . . . . . . . . . . . . . . . . . 25
   8. Evaluating Flow Monitoring Applicability . . . . . . . . . . 26
   9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 26
   10. Security Considerations . . . . . . . . . . . . . . . . . . 27
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . 27
   12. References. . . . . . . . . . . . . . . . . . . . . . . . . 27
      12.1 Normative References. . . . . . . . . . . . . . . . . . 27
      12.2 Informative References. . . . . . . . . . . . . . . . . 27
   Appendix A: Recommended Report Format . . . . . . . . . . . . . 29
   Appendix B: Miscellaneous Tests . . . . . . . . . . . . . . . . 30
      B.1 DUT Under Traffic Load . . . . . . . . . . . . . . . . . 30
      B.2 In-band Flow Export. . . . . . . . . . . . . . . . . . . 30
      B.3 Variable Packet Rate . . . . . . . . . . . . . . . . . . 30
      B.4 Bursty Traffic . . . . . . . . . . . . . . . . . . . . . 31

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      B.5 Various Flow Monitoring Configurations . . . . . . . . . 31
      B.6 Tests With Bidirectional Traffic . . . . . . . . . . . . 32
      B.7 Instantaneous Flow Export Rate . . . . . . . . . . . . . 32

1.  Introduction

    Monitoring of IP flows (Flow monitoring) is defined in the
    Architecture for IP Flow Information Export [RFC5470] and related
    IPFIX documents. It analyses the traffic using predefined fields
    from the packet header as keys and stores the traffic and
    other internal information in the DUT (Device Under Test) memory.
    This cached flow information is then formatted into records (see
    section 2.1 for term definitions) and exported from the DUT to an
    external data collector for analysis. More details on the
    measurement architecture is provided in section 3.3.

    Flow monitoring on network devices is widely deployed and has
    numerous uses in both service provider and enterprise segments as
    detailed in the Requirements for IP Flow Information Export
    [RFC3917]. This document provides a methodology for measuring Flow
    monitoring performance so that network operators have a framework
    for measurements of impact on the network and network equipment.

    This document's goal is a series of methodology specifications for
    the measurement of Flow monitoring performance, in a way that is
    comparable amongst various implementations, platforms, and
    vendor's devices.

    Flow monitoring is in most cases run on network devices also
    forwarding packets. This document therefore provides also the
    methodology for [RFC2544] measurements in the presence of Flow
    monitoring. It is applicable to IPv6 and MPLS traffic with their
    specifics defined in [RFC5180] and [RFC5695] respectively.

    The most significant performance parameter is the rate at which IP
    flows are created and expired in the network device's memory and
    exported to a collector. Therefore, this document specifies a
    methodology to measure the maximum IP flow rate that a network
    device can sustain without impacting the forwarding plane, without
    losing any IP flow information, and without compromising the IP flow
    accuracy (see section 7 for details).

    [RFC2544], [RFC5180] and [RFC5695] specify benchmarking of network
    devices forwarding IPv4, IPv6 and MPLS [RFC3031] traffic,
    respectively. The methodology specified in this document stays the
    same for any traffic type. The only restriction may be the DUT's
    lack of support for Flow monitoring of the particular traffic type.

    A variety of different network device architectures exist that are
    capable of Flow monitoring and export. As such, this document does
    not attempt to list the various white box variables (CPU load,
    memory utilization, hardware resources utilization etc) that could
    be gathered as they always help in comparison evaluations. A more

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    complete understanding of the stress points of a particular device
    can be attained using this internal information and the tester MAY
    choose to gather this information during the measurement iterations.

2.  Terminology

    The terminology used in this document is based on [RFC5470],
    [RFC2285] and [RFC1242] as summarised in section 2.1. The only new
    terms needed for this methodology are defined in section 2.2.

2.1 Existing Terminology

    Device Under Test (DUT)   [RFC2285, section 3.1.1]

    Flow                      [RFC5470, section 2]

    Flow Key                  [RFC5470, section 2]

    Flow Record               [RFC5470, section 2]

    Observation Point         [RFC5470, section 2]

    Metering Process          [RFC5470, section 2]

    Exporting Process         [RFC5470, section 2]

    Exporter                  [RFC5470, section 2]

    Collector                 [RFC5470, section 2]

    Control Information       [RFC5470, section 2]

    Data Stream               [RFC5470, section 2]

    Flow Expiration           [RFC5470, section 5.1.1]

    Flow Export               [RFC5470, section 5.1.2]

    Throughput                [RFC1242, section 3.17]

2.2 New Terminology

2.2.1 Cache

      Memory area held and dedicated by the DUT to store Flow
      information prior to the Flow Expiration.

2.2.2 Cache Size

      The size of the Cache in terms of how many entries the Cache can

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      This term is typically represented as a configurable option in
      the particular Flow monitoring implementation. Its highest value
      will depend on the memory available in the network device.

   Measurement units:
      Number of Cache entries

2.2.3 Active Timeout

      For long-running Flows, the time interval after which the Metering
      Process expires a Cache entry to ensure Flow data is regularly

      This term is typically presented as a configurable option in the
      particular Flow monitoring implementation. See section 5.1.1 of
      [RFC5470] for more detailed discussion.

      Flows are considered long-running when they last longer than
      several multiples of the Active Timeout. When If the Active Timeout is zero
      zero, then Flows are considered long-running if they contain a larger number of many
      more packets (tens of packets) than usual for usually observed in a single transaction based Flows, in the
      order of tens of packets and higher.

   Measurement units:

2.2.4 Inactive Timeout

      The time interval used by the Metering Process to expire an entry
      from the Cache, when no more packets belonging to that specific
      Cache entry have been observed during the interval.

      This term is typically represented as a configurable option in the
      particular Flow monitoring implementation. See section 5.1.1 of
      [RFC5470] for more detailed discussion.

   Measurement units:

2.2.5 Flow Export Rate

      The number of Cache entries that expire from the Cache (as defined
      by the Flow Expiration term) and are exported to the Collector
      within a measurement time interval. There SHOULD NOT be any export
      filtering, so that all the expired cache entries are exported. If
      there is export filtering and it can't be disabled, this needs to
      be noted.

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      The measured Flow Export Rate MUST include both the Data Stream
      and the Control Information, as defined in section 2 of [RFC5470].

      The Flow Export Rate is measured using Flow Export data observed
      at the Collector by counting the exported Flow Records during the
      measurement time interval (see section 5.4). The value obtained is
      an average of the instantaneous export rates observed during the
      measurement time interval. The smallest possible measurement
      interval (if attempting to measure nearly instantaneous export
      rate rather than average export rate on the DUT) is limited by the
      export capabilities of the particular Flow monitoring
      implementation (when possible physical layer issues between the
      DUT and the Collector are excluded).

   Measurement units:
      Number of Flow Records per second

3.  Flow Monitoring Performance Benchmark

3.1 Definition

   Flow Monitoring Throughput

      The maximum Flow Export Rate the DUT can sustain without losing a
      single Cache entry. Additionally, for packet forwarding devices,
      the maximum Flow Export Rate the DUT can sustain without dropping
      packets in the Forwarding Plane (see figure 1).

   Measurement units:
      Number of Flow Records per second

      The losses of Cache entries or forwarded packets in this
      definition are assumed to happen due to the lack of DUT resources
      to process any additional traffic information or lack of resources
      to process Flow Export data. The physical layer issues, like
      insufficient bandwidth from the DUT to the Collector or lack of
      Collector resources MUST be excluded as detailed in section 4.

3.2 Device Applicability

   The Flow monitoring performance metric is applicable to network
   devices that implement [RFC5470] architecture. These devices can be
   network packet forwarding devices or appliances which analyze the
   traffic but do not forward traffic (probes, sniffers, replicators).

   This document does not intend to measure Collector performance, it
   only requires sufficient Collector resources (as specified in section
   4.4) in order to measure the DUT characteristics.

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3.3 Measurement Concept

   Figure 1 below presents the functional block diagram of the DUT. The
   traffic in the figure represents the test traffic sent to the
   DUT and forwarded by the DUT, if possible. When testing devices which
   do not act as network packet forwarding devices (such as probes,
   sniffers and replicators) the forwarding plane is simply an
   Observation Point as defined in section 2 of [RFC5470]. The [RFC2544]
   Throughput of such devices will always be zero and the only
   applicable performance metric is the Flow Monitoring Throughput.

                 +------------------------- +
                 | IPFIX | NetFlow | Others |
                 +------------------------- +
                 |            ^             |
                 |       Flow Export        |
                 |            ^             |
                 |     +-------------+      |
                 |     | Monitoring  |      |
                 |     |   Plane     |      |
                 |     +-------------+      |
                 |            ^             |
                 |     traffic information  |
                 |            ^             |
                 |     +-------------+      |
                 |     |             |      |
      traffic ---|---->| Forwarding  |------|---->
                 |     |    Plane    |      |
                 |     +-------------+      |
                 |                          |
                 |           DUT            |
                 +------------------------- +

   Figure 1. The functional block diagram of the DUT

   Flow monitoring is represented in the figure 1 by the Monitoring
   Plane. It is enabled as specified in section 4.3. It uses the
   traffic information provided by the Forwarding Plane and configured
   Flow Keys to create Cache entries representing the traffic
   forwarded (or observed) by the DUT in the DUT Cache. The Cache
   entries are expired from the Cache depending on the Cache
   configuration (ie, the Active and Inactive Timeouts, number of Cache
   entries and the Cache Size) and the traffic pattern. The Cache
   entries are used by the Exporting Process to format the Flow Records
   which are then exported from the DUT to the Collector (see figure 2
   in section 4).

   The Forwarding Plane and Monitoring Plane represent two separate
   functional blocks, each with its own performance capability. The
   Forwarding Plane handles user data packets and is fully characterised
   by the metrics defined by [RFC2544].

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   The Monitoring Plane handles Flows which reflect the analysed
   traffic. The metric for Monitoring Plane performance is Flow Export
   Rate, and the benchmark is the Flow Monitoring Throughput.

3.4 The Measurement Procedure Overview

   The measurement procedure is fully specified in sections 4, 5 and 6.
   This section provides an overview of principles for the measurements.

   The basic measurement procedure of performance characteristics of a
   DUT with Flow monitoring enabled is a conventional Throughput
   measurement using a search algorithm to determine the maximum packet
   rate at which none of the offered packets and corresponding Flow
   Records are dropped by the DUT as described in [RFC1242] and section
   26.1 of [RFC2544].

   The DUT with Flow monitoring enabled contains two functional blocks
   which need to be measured using characteristics applicable to one or
   both blocks  (see figure 1). See sections 3.4.1 and 3.4.2 for further

   On one hand the Monitoring Plane and Forwarding Plane (see
   figure 1) need to be looked at as two independent blocks, and the
   performance of each of them measured independently. But on the other
   hand when measuring the performance of one of them, the status and
   performance of the other MUST be known and benchmarked when both are

3.4.1 Monitoring Plane Performance Measurement

   The Flow Monitoring Throughput MUST be (and can only be) measured
   with one packet per Flow as specified in section 5. This traffic
   type represents the most demanding traffic from the Flow monitoring
   point of view and will exercise the Monitoring Plane (see figure 1)
   of the DUT most. In this scenario every packet seen by DUT creates a
   new Cache entry and forces the DUT to fill the Cache instead of just
   updating packet and byte counters of an already existing Cache entry.

   The exit criteria for the Flow Monitoring Throughput measurement are
   one of the following (e.g. if any of the conditions is reached):

   a. The Flow Export Rate at which the DUT starts to lose Flow
      information or the Flow information gets corrupted
   b. The Flow Export Rate at which the Forwarding Plane starts to drop
      or corrupt packets (if the Forwarding Plane is present)

   A corrupted packet here means the packet header corruption (resulting
   in the cyclic redundancy check failure on the transmission level and
   consequent packet drop) or the packet payload corruption leading to
   the lost application level data.

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3.4.2 Forwarding Plane Performance Measurement

   The Forwarding Plane (see figure 1) performance metrics are fully
   specified by [RFC2544] and MUST be measured accordingly. A detailed
   traffic analysis (see below) with relation to Flow monitoring MUST be
   performed prior of any [RFC2544] measurements. Mainly the Flow Export
   Rate caused by the test traffic during an [RFC2544] measurement MUST
   be known and reported.

   The required test traffic analysis mainly involves the following:

   a. Which packet header parameters are incremented or changed during
      traffic generation
   b. Which Flow Keys the Flow monitoring configuration uses to generate
      Flow Records

   The RFC2544 performance metrics can be measured in one of the three

   a. As a baseline of forwarding performance without Flow monitoring
   b. At a certain level of Flow monitoring activity specified by a Flow
      Export Rate lower than the Flow Monitoring Throughput
   c. At the maximum level of Flow monitoring performance, e.g. using
      traffic conditions representing a measurement of Flow Monitoring

   The above mentioned measurement mode in point a. represents an
   ordinary Throughput measurement specified in RFC2544. The details of
   how to setup the measurements in points b. and c. are given in
   section 6.

4. Measurement Set-Up

   This section concentrates on the set-up of all components necessary
   to perform Flow monitoring performance measurement. The recommended
   reporting format can be found in Appendix A.

4.1 Measurement Topology

   The measurement topology described in this section is applicable only
   to the measurements with packet forwarding network devices. The
   possible architectures and implementation of the traffic monitoring
   appliances (see section 3.2) are too various to be covered in this
   document. Instead of the Forwarding Plane, these appliances generally
   have some kind of feed (an optical splitter, an interface sniffing
   traffic on a shared media or an internal channel on the DUT providing
   a copy of the traffic) providing the information about the traffic
   necessary for Flow monitoring analysis. The measurement topology then
   needs to be adjusted to the appliance architecture, and MUST be part
   of the measurement report.

   The measurement set-up is identical to that used by [RFC2544], with
   the addition of a Collector to analyze the Flow Export(see figure 2).

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   In the measurement topology with unidirectional traffic, the traffic
   is transmitted from the sender to the receiver through the DUT. The
   received traffic is analyzed to check it is identical to the
   generated traffic.

   The ideal way to implement the measurement is by using a single
   device to provide the sender and receiver capabilities with one
   sending port and one receiving port. This allows for an easy check
   whether all the traffic sent by the sender was re-transmitted by the
   DUT and received at the receiver.

                             |           |
                             | Collector |
                             |           |
                             |Flow Record|
                             | analysis  |
                             |           |
                                   | Flow Export
                                   | Export Interface
         +--------+         +-------------+          +----------+
         |        |         |             |          | traffic  |
         | traffic|      (*)|             |          | receiver |
         | sender |-------->|     DUT     |--------->|          |
         |        |         |             |          | traffic  |
         |        |         |             |          | analysis |
         +--------+         +-------------+          +----------+

   Figure 2 Measurement topology with unidirectional traffic

   The DUT's export interface (connecting the Collector) MUST NOT be
   used for forwarding the test traffic but only for the Flow Export
   data containing the Flow Records. In all measurements, the export
   interface MUST have enough bandwidth to transmit Flow Export data
   without congestion. In other words, the export interface MUST NOT be
   a bottleneck during the measurement.

   The traffic receiver MUST have sufficient resources to measure all
   test traffic transferred successfully by the DUT. This may be
   checked through measurements with and without the DUT.

   Note that more complex topologies might be required. For example, if
   the effects of enabling Flow monitoring on several interfaces are of
   concern or the media maximum speed is less than the DUT throughput,
   the topology can be expanded with several input and output ports.
   However, the topology MUST be clearly written in the measurement

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4.2 Baseline DUT Set Up

   The baseline DUT set-up and the way the set-up is reported in the
   measurement results is fully specified in section 7 of [RFC2544].

   The baseline DUT configuration might include other features like
   packet filters or quality of service on the input and/or output
   interfaces if there is the need to study Flow monitoring in the
   presence of those features. The Flow monitoring measurement
   procedures do not change in this case. Consideration needs to be made
   when evaluating measurement results to take into account the
   possible change of packet rates offered to the DUT and Flow
   monitoring after application of the features to the configuration.
   Any such feature configuration MUST be part of the measurement

   The DUT export interface (see figure 2) SHOULD be configured with
   sufficient output buffers to avoid dropping the Flow Export data due
   to a simple lack of resources in the interface hardware. The applied
   configuration MUST be part of the measurement report.

   The test designer has the freedom to run tests in multiple
   configurations. It is therefore possible to run both non-production
   and real deployment configurations in the laboratory, according to
   the needs of the tester. All configurations MUST be fully documented.

4.3 Flow Monitoring Configuration

   This section covers all the aspects of the Flow monitoring
   configuration necessary on the DUT in order to perform the Flow
   monitoring performance measurement. The necessary configuration has
   a number of components (see [RFC5470]), namely Observation Points,
   Metering Process and Exporting Process as detailed below.

   The DUT MUST support the Flow monitoring architecture as specified by
   [RFC5470]. The DUT SHOULD support IPFIX [RFC5101] to allow meaningful
   results comparison due to the standardized export protocol.

   The DUT configuration and any existing Cache MUST be erased before
   application of any new configuration for the currently executed

4.3.1 Observation Points

   The Observation Points specify the interfaces and direction where the
   Flow monitoring traffic analysis is to be performed.

   The (*) in Figure 2 designates the Observation Points in the default
   configuration. Other DUT Observation Points might be configured
   depending on the specific measurement needs as follows:

   a. ingress port/ports only
   b. egress port/ports only
   c. both ingress and egress
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   Generally, the placement of Observation Points depends upon the
   position of the DUT in the deployed network and the purpose of Flow
   monitoring. See [RFC3917] for detailed discussion. The measurement
   procedures are otherwise the same for all these possible

   In the case when both ingress and egress Flow monitoring is enabled
   on one DUT the results analysis needs to take into account that each
   Flow will be represented in the DUT Cache by two Flow Records (one
   for each direction). Therefore also the Flow Export will contain
   those two Flow Records.

   If more than one Observation Point for one direction is defined on
   the DUT the traffic passing through each of the Observation Points
   MUST be configured in such a way that it creates Flows and Flow
   Records which do not overlap. Each packet (or set of packets if
   measuring with more than one packet per Flow - see section 6.3.1)
   sent to the DUT on different ports still creates one unique Flow

   The specific Observation Points and associated monitoring direction
   MUST be included as part of the measurement report.

4.3.2 Metering Process

   The Metering Process MUST be enabled in order to create the Cache in
   the DUT and configure the Cache related parameters.

   The Cache Size available to the DUT MUST be known and taken into
   account when designing the measurement as specified in section 5.

   The configuration of the Metering Process MUST be recorded. For
   example, when a Flow monitoring implementation uses timeouts to
   expire entries from the Cache, the Cache's Inactive and Active
   Timeouts MUST be known and taken into account when designing the
   measurement as specified in section 5. If the Flow monitoring
   implementation allows only timeouts equal to zero (e.g. immediate
   timeout or non-existent Cache) then the measurement conditions in
   section 5 are fulfilled inherently without any additional
   configuration. The DUT simply exports information about every packet
   immediately, subject to the Flow Export Rate definition in section

   If the Flow monitoring implementation allows configuration of
   multiple Metering Processes on a single DUT, the exact configuration
   of each process MUST be included in the measurement report. Only
   measurements with the same number of Metering Processes can be

   The Cache Size, the Inactive and Active Timeouts MUST be included in
   the measurement report.

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4.3.3 Exporting Process

   The Exporting Process MUST be configured in order to export the Flow
   Record data to the Collector.

   The Exporting Process MUST be configured in such a way that all Flow
   Records from all configured Observation Points are exported towards
   the Collector, after the expiration policy composed of the Inactive
   and Active Timeouts and Cache Size.

   The Exporting Process SHOULD be configured with IPFIX [RFC5101] as
   the protocol to use to format the Flow Export data. If the Flow
   monitoring implementation does not support IPFIX, proprietary
   protocols MAY be used. Only measurements with same export protocol
   SHOULD be compared since the protocols may differ in their export
   efficiency. The export efficiency might also be influenced by used
   template layout and ordering of the individual export fields within
   the template. The templates used by the tested implementations SHOULD
   be analysed and reported as part of the measurement report. Ideally
   only tests with same templates layout should be compared.

   Various Flow monitoring implementations might use different default
   values regarding the export of Control Information [RFC5470] and
   therefore Flow Export corresponding to Control Information SHOULD
   be analyzed and reported as a separate item on the measurement
   report. The export of Control Information SHOULD always be
   configured consistently across all testing and configured to the
   minimal possible value. Ideally just one set of Control Information
   should be exported during each measurement. Note that Control
   Information includes IPFIX Options and Templates [RFC5101].

   Section 10 of [RFC5101] and section 8.1 of [RFC5470] discuss the
   possibility of deploying various transport layer protocols to deliver
   Flow Export data from the DUT to the Collector. The selected protocol
   MUST be included in the measurement report. Only benchmarks with the
   same transport layer protocol should be compared. If the Flow
   monitoring implementation allows the use of multiple the transport
   layer protocols, each of the protocols SHOULD be measured in a
   separate measurement run and the results reported independently in
   the measurement report.

   If a reliable transport protocol is used for the transmission of
   the Flow Export data from the DUT, the configuration of the
   Transport session MUST allow for non-blocking data transmission.
   An example of parameters to look at would be TCP window size and
   maximum segment size (MSS). The most substantial transport layer
   parameters should be included in the measurement report.

4.3.4 Flow Records

   A Flow Record contains information about a specific Flow that was
   observed at an Observation Point. A Flow Record contains measured
   properties of the Flow (e.g., the total number of bytes for all the

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   Flow packets) and usually characteristic properties of the Flow
   (e.g., source IP address).

   The Flow Record definition is implementation specific. A Flow
   monitoring implementation might allow for only a fixed Flow Record
   definition, based on the most common IP parameters in the IPv4 or
   IPv6 headers - for example source and destination IP addresses, IP
   protocol numbers or transport level port numbers. Another
   implementation might allow the user to define their own arbitrary
   Flow Record to monitor the traffic. The requirement for the
   measurements defined in this document is only the need for a large
   number of Cache entries in the Cache. The Flow Keys needed to
   achieve that will typically be source and destination IP addresses
   and transport level port numbers.

   The recommended full IPv4, IPv6 or MPLS Flow Record is shown

      Flow Keys:
               Source IP address
               Destination IP address
               MPLS label (for MPLS traffic type only)
               Transport layer source port
               Transport layer destination port
               IP protocol number (IPv6 next header)
               IP type of service (IPv6 traffic class)

      Other fields:
               Packet counter
               Byte counter

   Table 1: Recommended Configuration

   If the Flow monitoring allows for user defined Flow Records, the
   minimal Flow Record configurations allowing large numbers of Cache
   entries are for example:

      Flow Keys:
               Source IP address
               Destination IP address

      Other fields:
               Packet counter


      Flow Keys:
               Transport layer source port
               Transport layer destination port

      Other fields:
               Packet counter

      Table 2: User-defined Configuration
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   The Flow Record configuration MUST be clearly noted in the
   measurement report. The Flow Monitoring Throughput measurements on
   different DUTs or different Flow monitoring implementations MUST be
   compared only for exactly same Flow Record configuration.

4.3.5 Flow Monitoring With Multiple Configurations

   The Flow monitoring architecture as specified in [RFC5470] allows for
   more complicated configurations with multiple Metering and Exporting
   Processes on a single DUT. Depending on the particular Flow
   monitoring implementation it might affect the measured DUT
   performance. The measurement report should therefore contain
   information about how many Metering and Exporting processes were
   configured on the DUT for the selected Observation Points.

   The examples of such possible configurations are:

   a. Several Observation Points with a single Metering Process and a
      single Exporting Process
   b. Several Observation Points, each with one Metering Process but
      all using just one instance of Exporting Process
   c. Several Observation Points with per Observation Point Metering
      Process and Exporting Process

4.3.6 MPLS Measurement Specifics

   The Flow Record configuration for measurements with MPLS encapsulated
   traffic SHOULD contain the MPLS label.

   The tester SHOULD ensure that the data received by the Collector
   contains the expected MPLS labels.

   The MPLS forwarding performance document [RFC5695] specifies a number
   of possible MPLS label operations to test. The Observation Points
   MUST be placed on all the DUT test interfaces where the particular
   MPLS label operation takes place. The performance measurements SHOULD
   be performed with only one MPLS label operation at the time.

   The DUT MUST be configured in such a way that all the traffic is
   subject to the measured MPLS label operation.

4.4 Collector

   The Collector is needed in order to capture the Flow Export data
   which allows the Flow Monitoring Throughput to be measured.

   The Collector can be used as exclusively capture device providing
   just hexadecimal format of the Flow Export data. In such a case it
   does not need to have any additional Flow Export decoding
   capabilities and all the decoding is done off line.

   However if the Collector is also used to decode the Flow Export data
   then it SHOULD support IPFIX [RFC5101] for meaningful results

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   analysis. If proprietary Flow Export is deployed, the Collector MUST
   support it otherwise the Flow Export data analysis is not possible.

   The Collector MUST be capable of capturing the export packets sent
   from the DUT at the full rate without losing any of them. In the
   case of the use of reliable transport protocols (see also section
   4.3.3) to transmit Flow Export data, the Collector MUST have
   sufficient resources to guarantee non-blocking data transmission on
   the transport layer session.

   During the analysis, the Flow Export data needs to be decoded and the
   received Flow Records counted.

   The capture buffer MUST be cleared at the beginning of each

4.5 Sampling

   Packet sampling and flow sampling is out of scope of this document.
   This document applies to situations without packet, flow, or export

4.6 Frame Formats

   Flow monitoring itself is not dependent in any way on the media used
   on the input and output ports. Any media can be used as supported by
   the DUT and the test equipment.

   At the time of writing the most common transmission media and
   corresponding frame formats (Ethernet, Packet over SONET) for IPv4,
   IPv6 and MPLS traffic are specified within [RFC2544], [RFC5180] and

   The presented frame formats MUST be recorded in the measurement

4.7 Frame Sizes

   Frame sizes of the traffic to be analyzed by the DUT are specified in
   [RFC2544] section 9 for Ethernet type interfaces (64, 128, 256, 1024,
   1280, 1518 bytes) and in [RFC5180] section 5 for Packet over SONET
   interfaces (47, 64, 128, 256, 1024, 1280, 1518, 2048, 4096 bytes).

   When measuring with large frame sizes, care needs to be taken to
   avoid any packet fragmentation on the DUT interfaces which could
   negatively affect measured performance values.

   The presented frame sizes MUST be recorded in the measurement report.

4.8 Flow Export Data Packet Sizes

   The Flow monitoring performance will be affected by the packet size
   the particular implementation uses to transmit Flow Export data to

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   the Collector. The used packet size SHOULD be part of the measurement
   report and only measurements with same packet sizes SHOULD be

   The DUT export interface (see figure 2) maximum transmission unit
   (MTU) SHOULD be configured to the largest available value for the
   media. The Flow Export MTU MUST be recorded in the measurement

4.9 Illustrative Test Set-up Examples

   The below examples represent a hypothetical test set-up to clarify
   the use of Flow monitoring parameters and configuration, together
   with traffic parameters to test Flow monitoring. The actual
   benchmarking specifications are in sections 5 and 6.

4.9.1 Example 1 - Inactive Timeout Flow Expiration

   The traffic generator sends 1000 packets per second in 10000 defined
   streams, each stream identified by an unique destination IP address.
   Therefore each stream has a packet rate of 0.1 packets per second.

   The packets are sent in a round robin fashion (stream 1 to 10000)
   while incrementing the destination IP address for each sent packet.

   The configured Cache Size is 20000 Flow Records. The configured
   Active Timeout is 100 seconds, the Inactive Timeout is 5 seconds.

   Flow monitoring on the DUT uses the destination IP address as the
   Flow Key.

   A packet with destination IP address equal to A is sent every 10
   seconds, so the Cache entry would be refreshed in the Cache every 10
   seconds. However, the Inactive Timeout is 5 seconds, so the Cache
   entries will expire from the Cache due to the Inactive Timeout and
   when a new packet is sent with the same IP address A it will create a
   new entry in the Cache. This behaviour depends upon the design an
   efficiency of the cache ager, and incidences of multi-packet flows
   observed during this test should be noted.

   The measured Flow Export Rate in this case will be 1000 Flow
   Records per second since every single sent packet will always
   create a new Cache entry and 1000 packets per second is sent.

   The expected number of Cache entries in the Cache during the whole
   measurement is around 5000. It corresponds to the Inactive Timeout
   being 5 seconds and during those five seconds 5000 entries are
   created. This expectation might change in real measurement set-ups
   with large Cache Sizes and high packet rate where the DUT's actual
   export rate might be limited and lower than the Flow Expiration
   activity caused by the traffic offered to the DUT. This behaviour is
   entirely implementation specific.

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4.9.2 Example 2 - Active Timeout Flow Expiration

   The traffic generator sends 1000 packets per second in 100 defined
   streams, each stream identified by an unique destination IP address.
   Each stream has a packet rate of 10 packets per second. The packets
   are sent in a round robin fashion (stream 1 to 100) while
   incrementing the destination IP address for each sent packet.

   The configured Cache Size is 1000 Flow Records. The configured
   Active Timeout is 100 seconds. The Inactive Timeout is 10 seconds.

   Flow monitoring on the DUT uses the destination IP address as the
   Flow Key.

   After the first 100 packets are sent, 100 Cache entries will have
   been created in the Flow monitoring Cache. The subsequent packets
   will be counted against the already created Cache entries since the
   destination IP address (Flow Key) has already been seen by the DUT
   (provided the Cache entries did not expire yet as described below).

   A packet with destination IP address equal to A is sent every 0.1
   second, so the Cache entry is refreshed in the Cache every 0.1
   second, while the Inactive Timeout is 10 seconds. In this case the
   Cache entries will not expire until the Active Timeout, e.g. they
   will expire every 100 seconds and then the Cache entries will be
   created again.

   If the test measurement time is 50 seconds from the start of the
   traffic generator then the measured Flow Export Rate is 0 since
   during this period nothing expired from the Cache.

   If the test measurement time is 100 seconds from the start of the
   traffic generator then the measured Flow Export Rate is 1 Flow Record
   per second.

   If the test measurement time is 290 seconds from the start of the
   traffic generator then the measured Flow Export Rate is 2/3 of Flow
   Record per second since during the 290 seconds period the Cache
   expired same number of Flows twice (100).

5. Flow Monitoring Throughput Measurement Methodology


      To measure the Flow monitoring performance in a manner comparable
      between different Flow monitoring implementations.

   Metric definition:

      Flow Monitoring Throughput - see section 3.

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      Different Flow monitoring implementations might chose to handle
      Flow Export from a partially empty Cache differently than in the
      case when the Cache is fully occupied. Similarly software and
      hardware based DUTs can handle the same situation as stated above
      differently. The purpose of the benchmark measurement in this
      section is to abstract from all the possible behaviours and define
      one measurement procedure covering all the possibilities. The only
      criteria is to measure as defined here until Flow Record or packet
      losses are seen. The decision whether to dive deeper into the
      conditions under which the packet losses happen is left to the

5.1 Flow Monitoring Configuration

   Cache Size
      Cache Size configuration is dictated by the expected position of
      the DUT in the network and by the chosen Flow Keys of the Flow
      Record. The number of unique Flow Keys sets that the traffic
      generator (sender) provides should be multiple times larger than
      the Cache Size. This ensures that the existing Cache entries are
      never updated before Flow Expiration and Flow Export. The Cache
      Size MUST be known in order to define the measurement
      circumstances properly.

   Inactive Timeout
      Inactive Timeout is set (if configurable) to the minimum possible
      value on the DUT. This ensures that the Cache entries are expired
      as soon as possible and exported out of the DUT Cache. It MUST be
      known in order to define the measurement circumstances completely
      and equally across implementations.

   Active Timeout
      Active Timeout is set (if configurable) to a value equal to or
      higher than the Inactive Timeout. It MUST be known in order to
      define the measurement circumstances completely and equally
      across implementations.

   Flow Keys Definition:
      The test needs large numbers of unique Cache entries to be created
      by incrementing values of one or several Flow Keys. The number of
      unique combinations of Flow Keys values SHOULD be several times
      larger than the DUT Cache Size. This makes sure that any incoming
      packet will never refresh any already existing Cache entry.

   The availability of Cache Size, Inactive Timeout, Active Timeout as
   configuration parameters is implementation specific. If the Flow
   monitoring implementation does not support these parameters, the test
   possibilities as specified by this document are restricted. Some
   testing might be viable if the implementation follows the
   [IPFIX-CONFIG] document and needs to be considered on the case by
   by case basis.

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5.2 Traffic Configuration

   Traffic Generation
      The traffic generator needs to increment the Flow Keys values with
      each sent packet. This way each packet represents one Cache entry
      in the DUT Cache.

      If the test traffic rate is below the maximum media rate for
      the particular packet size the traffic generator MUST send the
      packets in equidistant time intervals. Traffic generators which do
      not fulfil this condition MUST NOT and cannot be used for the Flow
      Monitoring Throughput measurement. An example of this behaviour is
      if the test traffic rate is one half of the media rate and the
      traffic generator achieves this by sending each half of the second
      at the full media rate and then sending nothing for the second
      half of the second. In such conditions it would be impossible to
      distinguish if the DUT failed to handle the Flows due to the input
      buffers shortage during the burst or due to the limits in the Flow
      Monitoring performance.

   Measurement Duration
      The measurement duration (e.g. how long the test traffic is sent
      to the DUT) MUST be at least two times longer than the Inactive
      Timeout otherwise no Flow Export would be seen. The measurement
      duration SHOULD guarantee that the number of Cache entries created
      during the measurement exceeds the available Cache Size.

5.3 Cache Population

   The product of Inactive Timeout and the packet rate offered to the
   DUT (cache population) during one measurement determines the total
   number of Cache entries in the DUT Cache during the measurement
   (while taking into account some margin for dynamic behaviour during
   high DUT loads when processing the Flows).

   The Flow monitoring implementation might behave differently depending
   on the relation of cache population to the available Cache Size
   during the measurement. This behaviour is fully implementation
   specific and will also be influenced if the DUT is software based or
   hardware based architecture.

   The cache population (if it is lower or higher than the available
   Cache Size) during a particular benchmark measurement SHOULD be
   noted and mainly only measurements with same cache population SHOULD
   be compared.

5.4 Measurement Time Interval

   The measurement time interval is the time value which is used to
   calculate the measured Flow Export Rate from the captured Flow Export
   data. It is obtained as specified below.

   RFC2544 specifies with the precision of the packet beginning and end

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   the time intervals to be used to measure the DUT time
   characteristics. In the case of a Flow Monitoring Throughput
   measurement the start and stop time needs to be clearly defined but
   the granularity of this definition can be limited to just marking the
   start and stop time with the start and stop of the traffic generator.
   This assumes that the traffic generator and DUT are collocated and
   the variance in transmission delay from the generator to the DUT is
   negligible as compared to the total time of traffic generation.

   The measurement start time: the time when the traffic generator is

   The measurement stop time: the time when the traffic generator is

   The measurement time interval is then calculated as the difference
   (stop time) - (start time) - (Inactive Timeout).

   This supposes that the Cache Size is large enough so that the time to
   fill it up with Cache entries is longer than Inactive Timeout.
   Otherwise the time to fill up the Cache needs to be used for
   calculation of the measurement time interval in the place of the
   Inactive Timeout.

   Instead of measuring the absolute values of stop and start time it is
   possible to setup the traffic generator to send traffic for a certain
   pre-defined time interval which is then used in the above definition
   instead of the difference (stop time) - (start time).

   The Collector MUST stop collecting the Flow Export data at the
   measurement stop time.

   The Inactive Timeout (or the time needed to fill up the Cache) causes
   delay of the Flow Export data behind the test traffic which is
   analysed by the DUT. E.g. if the traffic starts at time point X Flow
   Export will start only at the time point X + Inactive Timeout (or X +
   time to fill up the Cache). Since Flow Export capture needs to stop
   with the traffic (because that's when the DUT stops processing the
   Flows at the given rate) the time interval during which the DUT kept
   exporting data is shorter by the Inactive Timeout than the Time
   interval when the test traffic was sent from the traffic generator to
   the DUT.

5.5 Flow Export Rate Measurement

   The Flow Export Rate needs to be measured in two consequent steps.
   The purpose of the first step (point a. below) is to gain the actual
   value for the rate, the second step (point b. below) needs to be done
   in order to verify Flow Record drops during the measurement:

   a. In the first step the captured Flow Export data MUST be analyzed
      only for the capturing interval (measurement time interval) as
      specified in section 5.4. During this period the DUT is forced to

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      process Cache entries at the rate the packets are sent. When
      traffic generation finishes, the behaviour when emptying the Cache
      is completely implementation specific and the Flow Export data
      from this period cannot be therefore used for the benchmarking.
   b. In the second step all the Flow Export data from the DUT MUST be
      captured in order to be capable to determine the Flow Record
      losses. It needs to be taken into account that especially when
      large Cache Sizes (in order of magnitude of hundreds of thousands
      of entries and higher) are in use the Flow Export can take many
      multiples of Inactive Timeout to empty the Cache after the
      measurement. This behaviour is completely implementation specific.

   If the Collector has the capability to redirect the Flow Export data
   after the measurement time interval into different capture buffer
   (or time stamp the received Flow Export data after that) this can be
   done in one step. Otherwise each Flow Monitoring Throughput
   measurement at certain packet rate needs to be executed twice - once
   to capture the Flow Export data just for the measurement time
   interval (to determine the actual Flow Export Rate) and second time
   to capture all Flow Export data in order to determine Flow Record
   losses at that packet rate.

   At the end of the measurement time interval the DUT might still be
   processing Cache entries which belong to the Flows expired from the
   Cache before the end of the interval. These Flow records might
   appear in an export packet sent only after the end of the
   measurement interval. This imprecision can be mitigated by large
   amounts of Flow Records used during the measurement (so that the
   few Flow Records in one export packet can be ignored) or by use of
   timestamps exported with the Flow Records.

5.6 The Measurement Procedure

  The measurement procedure is same as the Throughput measurement in
  section 26.1 of [RFC2544] for the traffic sending side. The DUT
  output analysis is done on the traffic generator receiving side for
  the test traffic the same way as for RFC2544 measurements.

  An additional analysis is performed using data captured by the
  Collector. The purpose of this analysis is to establish the value of
  the Flow Export Rate during the current measurement step and to verify
  that no Flow Records were dropped during the measurement. The
  procedure to measure Flow Export Rate is described in section 5.5.

  The Flow Export performance can be significantly affected by the way
  the Flow monitoring implementation formats the Flow Records into the
  Flow Export packets. The ordering and frequency of Control Information
  export and mainly the number of Flow Records in one Flow Export packet
  is of interest. The worst case scenario here is just one Flow Record
  in every Flow Export packet.

  Flow Export data should be sanity checked during the benchmark
  measurement for:

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  a. the number of Flow Records per packet, by simply calculating the
     ratio of exported Flow Records to the number of Flow Export
     packets captured during the measurement (which should be available
     as a counter on the Collector capture buffer)
  b. the number of Flow Records corresponding to the export of Control
     Information per Flow Export packet (calculated as the ratio of the
     total number of such Flow Records in the Flow Export data and the
     number of Flow Export packets).

6. RFC2544 Measurements

   RFC2544 measurements can be performed under two Flow Monitoring set-
   ups (see also section 3.4.2). This section details both of them and
   specifies ways to construct the test traffic so that RFC2544
   measurements can be performed in a controlled environment from the
   Flow monitoring point of view. A controlled Flow monitoring
   environment means that the tester always knows what Flow monitoring
   activity (Flow Export Rate) the traffic offered to the DUT causes.

   This section is applicable mainly for the RFC2544 throughput (RFC2544
   section 26.1) and latency (RFC2544 section 26.2 ) measurements. It
   could be used also to measure frame loss rate (RFC2544 section 26.3)
   and back-to-back frames (RFC2544 section 26.4). It is not relevant
   for the rest of RFC2544 network interconnect devices characteristics.


      Provide RFC2544 network device characteristics in the presence of
      Flow monitoring on the DUT. RFC2544 studies numerous
      characteristics of network devices. The DUT forwarding and time
      characteristics without Flow monitoring present on the DUT can
      vary significantly when Flow monitoring is deployed on the network

   Metric definition:

     Metric as specified in [RFC2544].

   The measured RFC2544 Throughput MUST NOT include the packet rate
   corresponding to the Flow Export data, because it is control type
   traffic. It is generated by the DUT as a result of enabling Flow
   monitoring and does not contribute to the test traffic which the DUT
   can handle. Flow Export requires DUT resources to be generated and
   transmitted and therefore the RFC2544 Throughput in most cases will
   be much lower when Flow monitoring is enabled on the DUT than without

6.1 Flow Monitoring Configuration

   Flow monitoring configuration (as detailed in section 4.3) needs
   to be applied the same way as discussed in section 5 with the
   exception of the Active Timeout configuration.

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   The Active Timeout SHOULD be configured to exceed several times the
   measurement time interval (see section 5.4). This makes sure that if
   measurements with two traffic components are performed (see section
   6.3.2) there is no Flow monitoring activity related to the second
   traffic component.

   The Flow monitoring configuration does not change in any other way
   for the measurement performed in this section. What changes and makes
   the difference is the traffic configurations as specified in the
   sections below.

6.2 Measurements with the Flow Monitoring Throughput Set-up

   The major requirement to perform a measurement with Flow Monitoring
   Throughput set-up is that the traffic and Flow monitoring is
   configured in such a way that each sent packet creates one entry in
   the DUT Cache. This restricts the possible set-ups only to the
   measurement with two traffic components as specified in section

6.3 Measurements With Fixed Flow Export Rate

   This section covers the measurements where the RFC2544 metrics need
   to be measured with Flow monitoring enabled but at certain Flow
   Export Rate lower than Flow Monitoring Throughput.

   The tester here has both options as specified in section 6.3.1 and

6.3.1 Measurements With Single Traffic Component

   Section 12 of [RFC2544] discusses the use of protocol source and
   destination addresses for defined measurements. To perform all the
   RFC2544 type measurements with Flow monitoring enabled the defined

   Flow Keys SHOULD contain IP source and destination address. The
   RFC2544 type measurements with Flow monitoring enabled then can be
   executed under these additional conditions:

   a. the test traffic is not limited to single unique pair of source
      and destination addresses
   b. the traffic generator defines test traffic as follows:
      allow for a parameter to send N (where N is an integer number
      starting at 1 and incremented in small steps) packets with source
      IP address A and destination IP address B before changing both IP
      addresses to the next value

   This test traffic definition allows execution of the Flow monitoring
   measurements with fixed Flow Export Rate while measuring the DUT
   RFC2544 characteristics. This set-up is the better option since it
   best simulates the live network traffic scenario with Flows
   containing more than just one packet.

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   The initial packet rate at N equal to 1 defines the Flow Export Rate
   for the whole measurement procedure. Subsequent increases of N will
   not change the Flow Export Rate as the time and Cache
   characteristics of the test traffic stay the same. This set-up is
   suitable for measurements with Flow Export Rates below the Flow
   Monitoring Throughput.

6.3.2 Measurements With Two Traffic Components

   The test traffic set-up in section 6.3.1 might be difficult to
   achieve with commercial traffic generators or the granularity of the
   traffic rates as defined by the initial packet rate at N equal to 1
   might not be suitable for the required measurement. An alternative
   mechanism is to define two traffic components in the test traffic.
   One to populate Flow monitoring Cache and the second one to execute
   the RFC2544 measurements.

   a. Flow monitoring test traffic component - the exact traffic
      definition as specified in section 5.2.
   b. RFC2544 Test Traffic Component - test traffic as specified by
      RFC2544 MUST create just one entry in the DUT Cache. In the
      particular set-up discussed here this would mean a traffic stream
      with just one pair of unique source and destination IP addresses
      (but could be avoided if Flow Keys were for example UDP/TCP source
      and destination ports and Flow Keys did not contain the

   The Flow monitoring traffic component will exercise the DUT in terms
   of Flow activity while the second traffic component will measure the
   RFC2544 characteristics.

   The measured RFC2544 Throughput is the sum of the packet rates of
   both traffic components. The definition of other RFC2544 metrics
   remains unchanged.

7. Flow Monitoring Accuracy

   The pure Flow Monitoring Throughput measurement in section 5 provides
   the capability to verify the Flow monitoring accuracy in terms of the
   exported Flow Record data. Since every Cache entry created in the
   Cache is populated by just one packet, the full set of captured data
   on the Collector can be parsed (e.g. providing the values of all Flow
   Keys and other Flow Record fields, not only the overall Flow Record
   count in the exported data) and each set of parameters from each Flow
   Record can be checked against the parameters as configured on the
   traffic generator and set in packets sent to the DUT. The exported
   Flow Record is considered accurate if:

   a. all the Flow Record fields are present in each exported Flow
   b. all the Flow Record fields values match the value ranges as set by
      the traffic generator (for example an IP address falls within the
      range of the IP addresses increments on the traffic generator)

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   c. all the possible Flow Record field values as defined at the
      traffic generator have been found in the captured export data on
      the Collector. This check needs to be offset against detected
      packet losses at the DUT during the measurement

8. Evaluating Flow Monitoring Applicability

   The measurement results as discussed in this document and obtained
   for certain DUTs allow for a preliminary analysis of a Flow
   monitoring deployment based on the traffic analysis data from the
   providers network.
   An example of such traffic analysis in the Internet is provided by
   [CAIDA] and the way it can be used is discussed below. The data
   needed to make an estimate if a certain network device can manage the
   particular amount of live traffic with Flow monitoring enabled is:

   Average packet size:            350 bytes
   Number of packets per IP Flow:  20

   Expected data rate on the network device: 1 Gbit/s

   The required value needed to be known is the average number of Flows
   created per second in the network device:

                       Expected packet rate
   Flows per second =  --------------------
                       Packet per flow

   When using the example values given above, the network device would
   be required to process 18 000 Flows per second. By executing the
   benchmarking as specified in this document a platform capable of this
   processing can be determined for the deployment in that particular
   part of the user network.

   It needs to be kept in mind that the above is a very rough and
   averaged Flow activity estimate which cannot account for traffic
   anomalies, for example a large number of DNS request packets which
   are typically small packets coming from many different sources and
   represent mostly just one packet per Flow.

9. Acknowledgements

   This work could have been performed thanks to the patience and
   support of Cisco Systems NetFlow development team, namely Paul
   Aitken, Paul Atkins and Andrew Johnson. Thanks belong to Benoit
   Claise for numerous detailed reviews and presentations of the
   document and Aamer Akhter for initiating this work. A special
   acknowledgment needs to go to the whole of the working group and
   especially to the chair Al Morton for the support and work on
   this draft and Paul Aitken for a very detailed technical review.

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10. Security Considerations

   Documents of this type do not directly affect the security of
   the Internet or corporate networks as long as benchmarking
   is not performed on devices or systems connected to operating

   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 constraints
   specified in sections above.

   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 DUT.

   Special capabilities SHOULD NOT exist in the DUT specifically for
   benchmarking purposes.  Any implications for network security arising
   from the DUT SHOULD be identical in the lab and in production

11.  IANA Considerations

    This memo makes no requests of IANA.

12. References

12.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, April 1997

   [RFC2544]  Bradner, S., "Benchmarking Methodology for Network
              Interconnect Devices", Informational, RFC 2544, April 1999

12.2. Informative References

   [RFC1242]  Bradner, S., "Benchmarking Terminology for Network
              Interconnection Devices", RFC 1242, July 1991

   [RFC2285]  Mandeville R., "Benchmarking Terminology for LAN Switching
              Devices", Informational, RFC 2285, November 1998

   [RFC3031]  E. Rosen, A. Viswanathan, R. Callon, "Multiprotocol Label
              Switching Architecture", Standards Track, RFC 3031,
              January 2001

   [RFC3917]  Quittek J., "Requirements for IP Flow Information Export
              (IPFIX)", Informational, RFC 3917, October 2004.

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   [RFC5101]  Claise B., "Specification of the IP Flow Information
              Export (IPFIX) Protocol for the Exchange of IP Traffic
              Flow Information", Standards Track, RFC 5101, January 2008

   [RFC5180]  C. Popoviciu, A. Hamza, D. Dugatkin, G. Van de Velde,
              "IPv6 Benchmarking Methodology for Network Interconnect
              Devices", Informational, RFC 5180, May 2008

   [RFC5470]  Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
              "Architecture Model for IP Flow Information Export",
              RFC 5470, October 2011

   [RFC5695]  Akhter A. "MPLS Forwarding Benchmarking Methodology",
              RFC 5695, November 2009

     [CAIDA]  Claffy, K., "The nature of the beast: recent traffic
              measurements from an Internet backbone",

[IPFIX-CONFIG] Configuration Data Model for IPFIX and PSAMP, G. Muenz
              et al, Work in Progress,

Author's Addresses

   Jan Novak (editor)
   Cisco Systems
   United Kingdom

Novak                                            Expires September, 2012
Appendix A: Recommended Report Format
Parameter                           Units
----------------------------------- ------------------------------------
Test Case                           test case name (section 5 and 6)
Test Topology                       Figure 2, other
Traffic Type                        IPv4, IPv6, MPLS, other

Test Results
  Flow Monitoring Throughput        Flow Records per second or Not
  Flow Export Rate                  Flow Records per second or Not
  Control Information Export Rate   Flow Records per second
  RFC2544 Throughput                packets per second
  (Other RFC2544 Metrics)           (as appropriate)

General Parameters
  Traffic Direction                 unidirectional, bidirectional
  DUT Interface Type                Ethernet, POS, ATM, other
  DUT Interface Bandwidth           MegaBits per second

Traffic Specifications
  Number of Traffic Components      (see section 6.3.1 and 6.3.2)
  For each traffic component:
  Packet Size                       bytes
  Traffic Packet Rate               packets per second
  Traffic Bit Rate                  MegaBits per second
  Number of Packets Sent            number of entries
  Incremented Packet Header Fields  list of fields
  Number of Unique Header Values    number of entries
  Number of Packets per Flow        number of entries

Flow monitoring Specifications
  Direction                         ingress, egress, both
  Observation Points                DUT interface names
  Cache Size                        number of entries
  Active Timeout                    seconds
  Inactive Timeout                  seconds
  Flow Keys                         list of fields
  Flow Record Fields                total number of fields
  Number of Flows Created           number of entries
  Flow Export Transport Protocol    UDP, TCP, SCTP, other
  Flow Export Protocol              IPFIX, NetFlow, other
  Flow Export data packet size      bytes
  Flow Export MTU                   bytes

MPLS Specifications                 (for traffic type MPLS only)
  Tested Label Operation            imposition, swap, disposition

Novak                                            xpires September, 2012
Appendix B: Miscellaneous Tests

   This section lists the tests which could be useful to asses a proper
   Flow monitoring operation under various operational or stress
   conditions. These tests are not deemed suitable for any benchmarking
   for various reasons.

B.1 DUT Under Traffic Load

   The Flow Monitoring Throughput SHOULD be measured under different
   levels of static traffic load through the DUT. This can be achieved
   only by using two traffic components as discussed in section 6.3.2.
   One traffic component exercises the Flow Monitoring Plane. The second
   traffic component loads only the Forwarding Plane without affecting
   Flow monitoring (e.g. it creates just a certain amount of permanent
   Cache entries).

   The variance in Flow Monitoring Throughput as function of the traffic
   load should be noted for comparison purposes between two DUTs of
   similar architecture and capability.

B.2 In-band Flow Export

   The test topology in section 4.1 mandates the use of separate Flow
   Export interface to avoid the Flow Export data generated by the DUT
   to mix with the test traffic from the traffic generator. This is
   necessary in order to create clear and reproducible test conditions
   for the benchmark measurement.

   The real network deployment of Flow monitoring might not allow for
   such a luxury - for example on a very geographically large network.
   In such a case, Flow Export will use an ordinary traffic forwarding
   interface e.g. in-band Flow Export.

   The Flow monitoring operation should be verified with in-band Flow
   Export configuration while following these test steps:

   a. Perform benchmark test as specified in section 5
   b. One of the results will be how much bandwidth Flow Export used
      on the dedicated Flow Export interface
   c. Change Flow Export configuration to use the test interface
   d. Repeat the benchmark test while the receiver filters out the
      Flow Export data from analysis

   The expected result is that the RFC2544 Throughput achieved in step
   a. is same as the Throughput achieved in step d. provided that the
   bandwidth of the output DUT interface is not the bottleneck (in
   other words it must have enough capacity to forward both test and
   Flow Export traffic).

B.3 Variable Packet Size

   The Flow monitoring measurements specified in this document would be

Novak                                            Expires September, 2012
   interesting to repeat with variable packet sizes within one
   particular test (e.g. test traffic containing mix of packet sizes).
   The packet forwarding tests specified mainly in [RFC2544] do not
   recommend and perform such tests. Flow monitoring is not dependent
   on packet sizes so such a test could be performed during the Flow
   Monitoring Throughput measurement and verify its value does not
   depend on the offered traffic packet sizes. The tests must be
   carefully designed in order to avoid measurement errors due to the
   physical bandwidth limitations and changes of the base forwarding
   performance with packet size.

B.4 Bursty Traffic

   RFC2544 section 21 discusses and defines the use of bursty traffic.
   It can be used for Flow monitoring testing as well to gauge some
   short term overload DUT capabilities in terms of Flow monitoring. The
   test benchmark here would not be the Flow Export Rate the DUT can
   sustain but the absolute number of Flow Records the DUT can process
   without dropping any single Flow Record. The traffic set-up to be
   used for this test is as follows:

   a. each sent packet creates a new Cache entry
   b. the packet rate is set to the maximum transmission speed of the
      DUT interface used for the test

B.5 Various Flow Monitoring Configurations

   This section translates the terminology used in the IPFIX documents
   [RFC5470], [RFC5101] and others into the terminology used in this
   document. Section B.5.2 proposes another measurement which is not
   possible to verify in a black box test manner.

B.5.1 RFC2544 Throughput without Metering Process

   If Metering Process is not defined on the DUT it means no Flow
   monitoring Cache exists and no Flow analysis occurs. The performance
   measurement of the DUT in such a case is just pure [RFC2544]

B.5.2 RFC2544 Throughput with Metering Process

   If only Metering Process is enabled it means that Flow analysis on
   the DUT is enabled and operational but no Flow Export happens. The
   performance measurement of a DUT in such a configuration represents
   an useful test of the DUT capabilities (this corresponds to the case
   when the network operator uses Flow monitoring for example for manual
   denial of service attacks detection and does not wish to use Flow

   The performance testing on this DUT can be performed as discussed in
   this document but it is not possible to verify the operation and
   results without interrogating the DUT.

Novak                                            Expires September, 2012
B.5.3 RFC2544 Throughput with Metering and Exporting Process

   This test represents the performance testing as discussed in
   section 6.

 B.6 Tests With Bidirectional Traffic

   The test topology in figure 2 can be expanded to verify Flow
   monitoring functionality with bidirectional traffic in two possible

   a. use two sets of interfaces, one for Flow monitoring for ingress
      traffic and one for Flow monitoring egress traffic
   b. use exactly same set-up as in figure 2 but use the interfaces in
      full duplex mode e.g. sending and receiving simultaneously on each
      of them

   The set-up in point a. above is in fact equivalent to the set-up with
   several Observation Points as already discussed in section 4.1
   and 4.3.1.

   For the set-up in point b. same rules should be applied (as per
   section 4.1 and 4.3.1) - traffic passing through each Observation
   Point SHOULD always create a new Cache entry in the Cache e.g. the
   same traffic SHOULD NOT be just looped back on the receiving
   interfaces to create the bidirectional traffic flow.

B.7 Instantaneous Flow Export Rate

   An additional useful information when analysing the Flow Export data
   is the time distribution of the instantaneous Flow Export Rate. It
   can be derived during the measurements in two ways:

   a. The Collector might provide the capability to decode Flow Export
      during capturing and at the same time counting the Flow Records
      and provide the instantaneous (or simply an average over shorter
      time interval than specified in section 5.4) Flow Export Rate
   b. The Flow Export protocol (like IPFIX [RFC5101]) can provide time
      stamps in the Flow Export packets which would allow time based
      analysis and calculate the Flow Export Rate as an average over
      much shorter time interval than specified in section 5.4

   The accuracy and shortest time average will always be limited by the
   precision of the time stamps (1 second for IPFIX) or by the
   capabilities of the DUT and the Collector.

Novak                                            Expires September, 2012