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Keywords: Performance, Flow monitoring, IPFIX, Netflow
Internet Engineering Task Force (IETF) J. Novak
Request for Comments: 6645 Cisco Systems, Inc.
Category: Informational July 2012
ISSN: 2070-1721
IP Flow Information Accounting and
Export Benchmarking Methodology
Abstract
This document provides a methodology and framework for quantifying
the performance impact of the monitoring of IP flows on a network
device and the 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 RFC 5470, "Architecture for IP Flow Information
Export". The methodology quantifies the impact of the IP flow
monitoring process on the network equipment.
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; see Section 2 of RFC 5741.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6645.
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Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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.
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Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................5
2.1. Existing Terminology .......................................5
2.2. New Terminology ............................................6
3. Flow Monitoring Performance Benchmark ...........................8
3.1. Definition .................................................8
3.2. Device Applicability .......................................8
3.3. Measurement Concept ........................................8
3.4. The Measurement Procedure Overview .........................9
4. Measurement Setup ..............................................11
4.1. Measurement Topology ......................................11
4.2. Baseline DUT Setup ........................................13
4.3. Flow Monitoring Configuration .............................13
4.4. Collector .................................................19
4.5. Sampling ..................................................19
4.6. Frame Formats .............................................19
4.7. Frame Sizes ...............................................20
4.8. Flow Export Data Packet Sizes .............................20
4.9. Illustrative Test Setup Examples ..........................20
5. Flow Monitoring Throughput Measurement Methodology .............22
5.1. Flow Monitoring Configuration .............................23
5.2. Traffic Configuration .....................................24
5.3. Cache Population ..........................................25
5.4. Measurement Time Interval .................................25
5.5. Flow Export Rate Measurement ..............................26
5.6. The Measurement Procedure .................................27
6. RFC 2544 Measurements ..........................................28
6.1. Flow Monitoring Configuration..............................28
6.2. Measurements with the Flow Monitoring Throughput Setup ....29
6.3. Measurements with Fixed Flow Export Rate...................29
7. Flow Monitoring Accuracy .......................................30
8. Evaluating Flow Monitoring Applicability .......................31
9. Acknowledgements ...............................................32
10. Security Considerations .......................................32
11. References ....................................................33
11.1. Normative References .....................................33
11.2. Informative References ...................................33
Appendix A. Recommended Report Format .............................35
Appendix B. Miscellaneous Tests ...................................36
B.1. DUT Under Traffic Load ...................................36
B.2. In-Band Flow Export ......................................36
B.3. Variable Packet Rate .....................................37
B.4. Bursty Traffic ...........................................37
B.5. Various Flow Monitoring Configurations ...................38
B.6. Tests with Bidirectional Traffic .........................38
B.7. Instantaneous Flow Export Rate ...........................39
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1. Introduction
Monitoring IP flows (Flow monitoring) is defined in the "Architecture
for IP Flow Information Export" [RFC5470] and related IPFIX documents
specified in Section 1.2 of [RFC5470]. It analyzes 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 are 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 (IPFIX)"
[RFC3917]. This document provides a methodology for measuring Flow
monitoring performance so that network operators have a framework to
measure the impact on the network and network equipment.
This document's goal is to provide a series of methodology
specifications for the measurement of Flow monitoring performance in
a way that is comparable amongst various implementations, platforms,
and vendor devices.
Flow monitoring is, in most cases, run on network devices that also
forward packets. Therefore, this document also provides 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.
This document specifies a methodology to measure the maximum IP Flow
Export Rate that a network device can sustain without impacting the
Forwarding Plane, without losing any IP flow information and without
compromising 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 a particular traffic type.
A variety of different DUT architectures exist that are capable of
Flow monitoring and export. As such, this document does not attempt
to list the various white-box variables (e.g., CPU load, memory
utilization, hardware resources utilization, etc.) that could be
gathered as they always help in comparison evaluations. A more
complete understanding of the stress points of a particular device
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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 that defined in
[RFC5470], [RFC2285], and [RFC1242], as summarized in Section 2.1.
The only new terms needed for this methodology are defined in Section
2.2.
Additionally, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
"SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
RFC 2119 [RFC2119].
2.1. Existing Terminology
Device Under Test (DUT) [RFC2285, Section 3.1.1]
Flow [RFC5101, Section 2]
Flow Key [RFC5101, Section 2]
Flow Record [RFC5101, Section 2]
Template Record [RFC5101, 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]
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2.2. New Terminology
2.2.1. Cache
Definition:
Memory area held and dedicated by the DUT to store Flow
information prior to the Flow Expiration.
2.2.2. Cache Size
Definition:
The size of the Cache in terms of how many entries the Cache can
hold.
Discussion:
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
Definition:
For long-running Flows, the time interval after which the Metering
Process expires a Cache entry to ensure Flow data is regularly
updated.
Discussion:
This term is typically presented as a configurable option in the
particular Flow monitoring implementation. See Section 5.1.1 of
[RFC5470] for a more detailed discussion.
Flows are considered long running when they last longer than
several multiples of the Active Timeout. If the Active Timeout is
zero, then Flows are considered long running if they contain many
more packets (tens of packets) than usually observed in a single
transaction.
Measurement units:
Seconds
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2.2.4. Idle Timeout
Definition:
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.
Discussion:
Idle Timeout is typically represented as a configurable option in
the particular Flow monitoring implementation. See Section 5.1.1
of [RFC5470] for more detailed discussion. Note that some
documents in the industry refer to "Idle Timeout" as "inactive
timeout".
Measurement units:
Seconds
2.2.5. Flow Export Rate
Definition:
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 MUST be indicated in the measurement report.
The measured Flow Export Rate MUST include both the Data Stream
and the Control Information, as defined in Section 2 of [RFC5470].
Discussion:
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 a 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 physical-layer issues between the DUT and the
Collector are excluded).
Measurement units:
Number of Flow Records per second
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3. Flow Monitoring Performance Benchmark
3.1. Definition
Flow Monitoring Throughput
Definition:
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
Discussion:
The losses of Cache entries, or forwarded packets per 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 deploy the architecture described in [RFC5470]. These
devices can be network packet forwarding devices or appliances that
analyze traffic but do not forward traffic (e.g., 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.
3.3. Measurement Concept
Figure 1 presents the functional block diagram of the DUT. The
traffic in the figure represents test traffic sent to the DUT and
forwarded by the DUT, if possible. When testing devices that 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 Throughput of such devices
will always be zero, and the only applicable performance metric is
the Flow Monitoring Throughput. Netflow is specified by [RFC3954].
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+------------------------- +
| 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 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 (e.g., the Active
and Idle Timeouts, the Cache Size), number of Cache entries, 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 characterized
by the metrics defined by [RFC1242].
The Monitoring Plane handles Flows that reflect the analyzed traffic.
The metric for Monitoring Plane performance is the 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.
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The basic measurement procedure of the 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
that 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
discussion.
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 measured independently. On the other hand, when measuring
the performance of one, the status and performance of the other MUST
be known and benchmarked when both are present.
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 the DUT
creates a new Cache entry and forces the DUT to fill the Cache
instead of just updating the 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 are 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 packet header corruption (resulting in
the cyclic redundancy check failure on the transmission level and
consequent packet drop) or packet payload corruption, which leads to
lost application-level data.
3.4.2. Forwarding Plane Performance Measurement
The Forwarding Plane (see Figure 1) performance metrics are fully
specified by [RFC1242] and MUST be measured accordingly. A detailed
traffic analysis (see below) with relation to Flow monitoring MUST be
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performed prior of any [RFC2544] measurements. Most importantly, 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 performance metrics described in RFC 1242 can be measured in one
of the three modes:
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
Throughput.
The above mentioned measurement mode in point a. represents an
ordinary Throughput measurement specified in RFC 2544. The details
of how to set up the measurements in points b. and c. are given in
Section 6.
4. Measurement Setup
This section concentrates on the setup 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 (e.g., 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.
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The measurement setup is identical to that used by [RFC2544], with
the addition of a Collector to analyze the Flow Export (see Figure
2).
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 that 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
as to 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 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.
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Note that more complex topologies might be required. For example, if
the effects of enabling Flow monitoring on several interfaces is of
concern, or the maximum speed of media transmission 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 report.
4.2. Baseline DUT Setup
The baseline DUT setup and the way the setup 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
report.
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 part of the
measurement report.
4.3. Flow Monitoring Configuration
This section covers all of 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 a
meaningful results comparison due to the standardized export
protocol.
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The DUT configuration, any existing Cache, and Cache entries MUST be
erased before the application of any new configuration for the
currently executed measurement.
4.3.1. Observation Points
The Observation Points specify the interfaces and direction in which
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
This test topology corresponds to unidirectional traffic only with
traffic analysis performed on the input and/or output interface.
Testing with bidirectional traffic is discussed in Appendix B.
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
configurations.
In the case of both ingress and egress Flow monitoring being enabled
on one DUT, the resulting analysis should consider that each Flow
will be represented in the DUT Cache by two Flow Records (one for
each direction). Therefore, the Flow Export will also 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 that do not overlap. Each packet (or set of packets if
measuring more than one packet per Flow - see Section 6.3.1) sent to
the DUT on different ports still creates one unique Flow Record.
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.
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The Cache Size available to the DUT MUST be known and taken into
account when designing the measurement as specified in Section 5.
Typically, the Cache Size will be present in the "show" commands of
the Flow monitoring process, in either the actual configuration or
the product documentation from the DUT vendor. The Cache Size MUST
have a fixed value for the entire duration of the measurement. This
method is not applicable to benchmarking any Flow monitoring
applications that dynamically change their Cache Size.
The configuration of the Metering Process MUST be included as part of
the measurement report. For example, when a Flow monitoring
implementation uses timeouts to expire entries from the Cache, the
Cache's Idle 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 2.2.5.
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
compared.
The Cache Size and the Idle and Active Timeouts MUST be included in
the measurement report.
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, which is composed of the
Idle and Active Timeouts and Cache Size.
The Exporting Process SHOULD be configured with IPFIX [RFC5101] as
the protocol used to format the Flow Export data. If the Flow
monitoring implementation does not support IPFIX, proprietary
protocols MAY be used. Only measurements with the same export
protocol SHOULD be compared since the protocols may differ in their
export efficiency. The export efficiency might also be influenced by
the Template Record used and the ordering of the individual export
fields within the template.
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The Template Records used by the tested implementations SHOULD be
analyzed and documented as part of the measurement report. Ideally,
only tests with same Template Records should be compared.
Various Flow monitoring implementations might use different default
values regarding the export of Control Information [RFC5470];
therefore, the 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 options and Template Records [RFC5470].
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 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 the 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 observed at
an Observation Point. A Flow Record contains measured properties of
the Flow (e.g., the total number of bytes for all the 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 only requirement for the
measurements defined in this document is the need for a large
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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 below.
The IP address indicates either IPv4 or IPv6, depending on the
traffic type being tested. The Flow Record configuration is Flow
monitoring implementation-specific; therefore, the examples below
cannot provide an exact specification of individual entries in each
Flow Record. The best set of key fields to use is left to the test
designer using the capabilities of the specific Flow monitoring
implementation.
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
or:
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
only compared for exactly the 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. Therefore, the measurement report should 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. For this document's purposes,
"MPLS Label" is the entire 4 byte MPLS header. Typically, the label
of the interest will be at the top of the label stack, but this
depends on the details of the MPLS test setup.
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.
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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 exclusively as a 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 offline.
However, if the Collector is also used to decode the Flow Export
data, it SHOULD support IPFIX [RFC5101] for meaningful results
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. When using
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
measurement.
4.5. Sampling
Packet sampling and flow sampling is out of the scope of this
document. This document applies to situations without packet, flow,
or export sampling.
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. This applies both to data forwarding
interfaces and to the export interface (see Figure 2).
At the time of this writing, the most common transmission media and
corresponding frame formats (e.g., Ethernet, Packet over SONET) for
IPv4, IPv6, and MPLS traffic are specified within [RFC2544],
[RFC5180], and [RFC5695].
The presented frame formats MUST be recorded in the measurement
report.
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4.7. Frame Sizes
Frame sizes of the traffic to be analyzed by the DUT are specified in
Section 9 of [RFC2544] for Ethernet type interfaces (64, 128, 256,
1024, 1280, 1518 bytes) and in Section 5 of [RFC5180] 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 that 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
that the particular implementation uses to transmit Flow Export data
to the Collector. The used packet size MUST be part of the
measurement report and only measurements with same packet sizes
SHOULD be compared.
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
report.
4.9. Illustrative Test Setup Examples
The examples below represent a hypothetical test setup 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 - Idle Timeout Flow Expiration
The traffic generator sends 1000 packets per second in 10000 defined
streams, each stream identified by a 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.
After a packet for stream 10000 is sent, the next packet destination
IP address corresponds to stream 1's address again.
The configured Cache Size is 20000 Flow Records. The configured
Active Timeout is 100 seconds, and the Idle Timeout is 5 seconds.
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Flow monitoring on the DUT uses the destination IP address as the
Flow Key.
A packet with the destination IP address equal to A is sent every 10
seconds, so the Cache entry is refreshed in the Cache every 10
seconds. However, the Idle Timeout is 5 seconds, so the Cache
entries will expire from the Cache due to the Idle Timeout, and when
a new packet is sent with the same IP address A, it will create a new
entry in the Cache. This behavior depends upon the design and
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 are sent.
The expected number of Cache entries in the Cache during the whole
measurement is around 5000. It corresponds to the Idle Timeout being
5 seconds; during those five seconds, 5000 entries are created. This
expectation might change in real measurement setups with large Cache
Sizes and a 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 behavior is entirely
implementation-specific.
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 a 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. After
a packet for stream 100 is sent, the next packet destination IP
address corresponds to stream 1's address again.
The configured Cache Size is 1000 Flow Records. The configured
Active Timeout is 100 seconds. The Idle 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).
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A packet with the 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 Idle Timeout is 10 seconds. In this case, the
Cache entries will not expire until the Active Timeout expires, 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 a
Flow Record per second since the Cache expired the same number of
Flows twice (100) during the 290-seconds period.
5. Flow Monitoring Throughput Measurement Methodology
Objective:
To measure the Flow monitoring performance in a manner that is
comparable between different Flow monitoring implementations.
Metric definition:
Flow Monitoring Throughput - see Section 3.
Discussion:
Different Flow monitoring implementations might choose to handle
Flow Export from a partially empty Cache differently than in the
case of the Cache being 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 define one measurement procedure covering all the
possible behaviors.
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 tester.
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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 sets of Flow Keys 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 by a packet from the sender before the particular
Flow Expiration and Flow Export. This condition is simple to
fulfill with linearly incremented Flow Keys (for example, IP
addresses or transport-layer ports) where the range of values must
be larger than the Cache Size. When randomized traffic generation
is in use, the generator must ensure that the same Flow Keys are
not repeated within a range of randomly generated values.
The Cache Size MUST be known in order to define the measurement
circumstances properly. Typically, the Cache Size will be found
using the "show" commands of the Flow monitoring implementation in
the actual configuration or in the product documentation from the
vendor.
Idle Timeout
Idle 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 Idle 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, Idle Timeout, and 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
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testing might be viable if the implementation follows the guidance
provided in the [IPFIX-CONFIG] document and is considered on a case-
by-case basis.
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.
A particular Flow monitoring implementation might choose to deploy
a hashing mechanism to match incoming data packets to a certain
Flow. In such a case, the combination of how the traffic is
constructed and the hashing might influence the DUT Flow
monitoring performance. For example, if IP addresses are used as
Flow Keys, this means there could be a performance difference for
linearly incremented addresses (in ascending or descending order)
as opposed to IP addresses randomized in a certain range. If
randomized IP address sequences are used, then the traffic
generator needs to be able to reproduce the randomization (e.g.,
the same set of IP addresses sent in the same order in different
test runs) in order to compare various DUTs and Flow monitoring
implementations.
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 that do
not fulfill this condition MUST NOT and cannot be used for the
Flow Monitoring Throughput measurement. An example of this
behavior is if the test traffic rate is one half of the media
rate. The traffic generator achieves this rate by sending packets
each half of each second at the full media rate and sending
nothing for the second half of each second. In such conditions,
it would be impossible to distinguish if the DUT failed to handle
the Flows due to the shortage of input buffers 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 Idle
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.
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5.3. Cache Population
The product of the Idle 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 behavior during
high DUT loads when processing the Flows).
The Flow monitoring implementation might behave differently depending
on the relation of the Cache population to the available Cache Size
during the measurement. This behavior is fully implementation-
specific and will also be influenced if the DUT architecture is
software based or hardware based.
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 the same Cache population
SHOULD be compared.
5.4. Measurement Time Interval
The measurement time interval is the time value that is used to
calculate the measured Flow Export Rate from the captured Flow Export
data. It is obtained as specified below.
RFC 2544 specifies, with the precision of the packet beginning and
ending, 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 started
The measurement stop time: the time when the traffic generator is
stopped
The measurement time interval is then calculated as the difference
(stop time) - (start time) - (Idle Timeout).
This supposes that the Cache Size is large enough that the time
needed to fill it with Cache entries is longer than the Idle Timeout.
Otherwise, the time needed to fill the Cache needs to be used to
calculate the measurement time interval in place of the Idle Timeout.
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Instead of measuring the absolute values of the stop and start times,
it is possible to set up the traffic generator to send traffic for a
certain predefined 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 Idle Timeout (or the time needed to fill the Cache) causes delay
of the Flow Export data behind the test traffic that is analyzed by
the DUT. For example, if the traffic starts at time point X, Flow
Export will start only at the time point X + Idle Timeout (or X +
time to fill 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 Idle 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 that no Flow Record are dropped 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 process Cache entries at the rate the packets are sent. When
traffic generation finishes, the behavior when emptying the Cache
is completely implementation-specific; therefore, the Flow Export
data from this period cannot be used for benchmarking.
b. In the second step, all the Flow Export data from the DUT MUST be
captured in order 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
Idle Timeout to empty the Cache after the measurement. This
behavior is completely implementation-specific.
If the Collector has the capability to redirect the Flow Export data
after the measurement time interval into a 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 a certain packet rate needs to be executed twice --
once to capture the Flow Export data just for the measurement time
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interval (to determine the actual Flow Export Rate) and a 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 that 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 use of large amounts
of Flow Records 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 the 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 RFC 2544 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 for measuring the 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 in which Control
Information is exported and the number of Flow Records in one Flow
Export packet are of interest. In the worst case scenario, there is
just one Flow Record in every Flow Export packet.
Flow Export data should be sanity checked during the benchmark
measurement for:
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).
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6. RFC 2544 Measurements
RFC 2544 measurements can be performed under two Flow monitoring
setups (see also Section 3.4.2). This section details both and
specifies ways to construct the test traffic so that RFC 2544
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 Throughput (RFC 2544,
Section 26.1) and latency (RFC 2544, Section 26.2 ) measurements. It
could also be used to measure frame loss rate (RFC 2544, Section
26.3) and back-to-back frames (RFC 2544, Section 26.4). Flow Export
requires DUT resources to be generated and transmitted; therefore,
the Throughput in most cases will be much lower when Flow monitoring
is enabled on the DUT than when it is not.
Objective:
Provide RFC 2544 network device characteristics in the presence of
Flow monitoring on the DUT. RFC 2544 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
device.
Metric definition:
Metric as specified in [RFC2544].
The measured Throughput MUST NOT include the packet rate
corresponding to the Flow Export data, because it is not user traffic
forwarded by the DUT. It is generated by the DUT as a result of
enabling Flow monitoring and does not contribute to the test traffic
that the DUT can handle. Flow Export requires DUT resources to be
generated and transmitted; therefore, the Throughput in most cases
will be much lower when Flow monitoring is enabled on the DUT than
when it is not.
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.
The Active Timeout SHOULD be configured to exceed several times the
measurement time interval (see Section 5.4). This ensures that if
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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 Setup
To perform a measurement with Flow Monitoring Throughput setup, the
major requirement is that the traffic and Flow monitoring be
configured in such a way that each sent packet creates one entry in
the DUT Cache. This restricts the possible setups only to the
measurement with two traffic components as specified in Section
6.3.2.
6.3. Measurements with a Fixed Flow Export Rate
This section covers the measurements where the RFC 2544 metrics need
to be measured with Flow monitoring enabled, but at a certain Flow
Export Rate that is lower than the Flow Monitoring Throughput.
The tester here has both options as specified in Sections 6.3.1 and
6.3.2.
6.3.1. Measurements with a Single Traffic Component
Section 12 of [RFC2544] discusses the use of protocol source and
destination addresses for defined measurements. To perform all the
RFC 2544 type measurements with Flow monitoring enabled, the defined
Flow Keys SHOULD contain an IP source and destination address. The
RFC 2544 type measurements with Flow monitoring enabled then can be
executed under these additional conditions:
a. the test traffic is not limited to a single, unique pair of source
and destination addresses.
b. the traffic generator defines test traffic as follows: it allows
for a parameter to send N (where N is an integer number starting
at 1 and is 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 a fixed Flow Export Rate while measuring the DUT
RFC 2544 characteristics. This setup is the better option since it
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best simulates the live network traffic scenario with Flows
containing more than just one packet.
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 setup is suitable for
measurements with Flow Export Rates below the Flow Monitoring
Throughput.
6.3.2 Measurements with Two Traffic Components
The test traffic setup described in Section 6.3.1 might be difficult
to achieve with commercial traffic generators or if the granularity
of the traffic rates as defined by the initial packet rate at N equal
to 1 are unsuitable 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 to execute the
RFC 2544 measurements.
a. Flow monitoring test traffic component -- the exact traffic
definition as specified in Section 5.2.
b. RFC 2544 Test Traffic Component -- test traffic as specified by
RFC 2544 MUST create just one entry in the DUT Cache. In the
particular setup 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
addresses).
The Flow monitoring traffic component will exercise the DUT in terms
of Flow activity, while the second traffic component will measure the
RFC 2544 characteristics.
The measured Throughput is the sum of the packet rates of both
traffic components. The definition of other RFC 1242 metrics remains
unchanged.
7. Flow Monitoring Accuracy
The pure Flow Monitoring Throughput measurement described 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
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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
Record.
b. all the Flow Record fields' values match the value ranges set by
the traffic generator (for example, an IP address falls within the
range of the IP address increments on the traffic generator).
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.
For a DUT with packet forwarding, the Flow monitoring accuracy also
involves data checks on the received traffic, as already discussed in
Section 4.
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]; the way it can be used is discussed
below. The data needed to 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 average number of Flows created per second in the network device
is needed and is determined as follows:
Expected packet rate
Flows per second = --------------------
Packet per flow
When using the above example values, the network device is required
to process 18000 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.
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Keep 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 that are typically
small packets coming from many different sources and represent mostly
just one packet per Flow.
9. Acknowledgements
This work was performed thanks to the patience and support of Cisco
Systems NetFlow development team, namely Paul Aitken, Paul Atkins,
and Andrew Johnson. Thanks to Benoit Claise for numerous detailed
reviews and presentations of the document, and to Aamer Akhter for
initiating this work. A special acknowledgment to the entire BMWG
working group, especially to the chair, Al Morton, for the support
and work on this document and Paul Aitken for a very detailed
technical review.
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 networks.
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
networks.
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11. References
11.1. 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.
11.2. Informative References
[RFC1242] Bradner, S., "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, July 1991.
[RFC2285] Mandeville, R., "Benchmarking Terminology for LAN
Switching Devices", RFC 2285, February 1998.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC3917] Quittek, J., Zseby, T., Claise, B., and S. Zander,
"Requirements for IP Flow Information Export (IPFIX)",
RFC 3917, October 2004.
[RFC3954] Claise, B., Ed., "Cisco Systems NetFlow Services Export
Version 9", RFC 3954, October 2004.
[RFC5101] Claise, B., Ed., "Specification of the IP Flow
Information Export (IPFIX) Protocol for the Exchange of
IP Traffic Flow Information", RFC 5101, January 2008.
[RFC5180] Popoviciu, C., Hamza, A., Van de Velde, G., and D.
Dugatkin, "IPv6 Benchmarking Methodology for Network
Interconnect Devices", RFC 5180, May 2008.
[RFC5470] Sadasivan, G., Brownlee, N., Claise, B., and J. Quittek,
"Architecture for IP Flow Information Export", RFC 5470,
March 2009.
[RFC5695] Akhter, A., Asati, R., and C. Pignataro, "MPLS Forwarding
Benchmarking Methodology for IP Flows", RFC 5695,
November 2009.
[CAIDA] Claffy, K., "The nature of the beast: recent traffic
measurements from an Internet backbone",
http://www.caida.org/publications/papers/1998/
Inet98/Inet98.html
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RFC 6645 Flow Monitoring Benchmarking July 2012
[IPFIX-CONFIG]
Muenz, G., Muenchen, TU, Claise, B., and P. Aitken,
"Configuration Data Model for IPFIX and PSAMP", Work in
Progress, July 2011.
[PSAMP-MIB] Dietz, T., Claise, B., and J. Quittek, "Definitions of
Managed Objects for Packet Sampling", Work in Progress,
October 2011.
[IPFIX-MIB] Dietz, T., Kobayashi, A., Claise, B., and G. Muenz,
"Definitions of Managed Objects for IP Flow Information
Export", Work in Progress, March 2012.
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Appendix A. (Informative) Recommended Report Format
Parameter Units
----------------------------------- ------------------------------------
Test Case test case name (Sections 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
Applicable
Flow Export Rate Flow Records per second or Not
Applicable
Control Information Export Rate Flow Records per second
Throughput packets per second
(Other RFC 1242 Metrics) (as appropriate)
General Parameters
DUT Interface Type Ethernet, POS, ATM, other
DUT Interface Bandwidth MegaBits per second
Traffic Specifications
Number of Traffic Components (see Sections 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
Traffic Generation linearly incremented or
randomized
Flow monitoring Specifications
Direction ingress, egress, both
Observation Points DUT interface names
Cache Size number of entries
Active Timeout seconds
Idle 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
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Parameter Units (continued)
----------------------------------- ------------------------------------
MPLS Specifications (for traffic type MPLS only)
Tested Label Operation imposition, swap, disposition
The format of the report as documented in this appendix is informative,
but the entries in the contents of it are required as specified in the
corresponding sections of this document.
Many of the configuration parameters required by the measurement report
can be retrieved from the [IPFIX-MIB] and [PSAMP-MIB] MIB modules, and
from the [IPFIX-CONFIG] YANG module or other general MIBs. Therefore,
querying those modules from the DUT would be beneficial: first of all,
to help in populating the required entries of the measurement report,
and also to document all the other configuration parameters from the
DUT.
Appendix B. (Informative) Miscellaneous Tests
This section lists tests that 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 (i.e., it creates just a certain amount of
permanent Cache entries).
The variance in Flow Monitoring Throughput as a 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 a 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.
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In such a case, the 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 the benchmark test as specified in Section 5. One of the
results will be how much bandwidth Flow Export used on the
dedicated Flow Export interface.
b. Change Flow Export configuration to use the test interface.
c. Repeat the benchmark test while the receiver filters out the Flow
Export data from analysis.
The expected result is that the Throughput achieved in step a. is
same as the Throughput achieved in step c. 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
interesting to repeat with variable packet sizes within one
particular test (e.g., test traffic containing mixed packet sizes).
The packet forwarding tests specified mainly in [RFC2544] do not
recommend performing such tests. Flow monitoring is not dependent on
packet sizes, so such a test could be performed during the Flow
Monitoring Throughput measurement, and verification of 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
RFC 2544, Section 21 discusses and defines the use of bursty traffic.
It can be used for Flow monitoring testing 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 setup 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.
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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 that is
impossible to verify in a black box test manner.
B.5.1. Throughput without the Metering Process
If the 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]
measurement.
B.5.2. Throughput with the Metering Process
If only the Metering Process is enabled, 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 a useful test
of the DUT's capabilities (this corresponds to the case when the
network operator uses Flow monitoring, for example, for manual
detection of denial-of-service attacks, and does not wish to use Flow
Export).
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.
B.5.3. Throughput with the Metering and Exporting Processes
This test represents the performance testing as discussed in Section
6.
B.6. Tests With Bidirectional Traffic
Bidirectional traffic is not part of the normative benchmarking tests
based on discussion with and recommendation of the Benchmarking
working group. The experienced participants stated that this kind of
traffic did not provide reproducible results.
The test topology in Figure 2 can be expanded to verify Flow
monitoring functionality with bidirectional traffic using the
interfaces in full duplex mode, e.g., sending and receiving
simultaneously on each of them.
The same rules should be applied for Flow creation in the DUT Cache
(as per Sections 4.1 and 4.3.1) -- traffic passing through each
Observation Point should always create a new Cache entry in the
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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
Additional useful information when analyzing 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 count 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 that 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.
Author's Address
Jan Novak (editor)
Cisco Systems
Edinburgh
United Kingdom
EMail: janovak@cisco.com
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