Network Working Group R. Mandeville
Internet-Draft European Network Laboratories
Expiration Date: November 1999 J. Perser
Netcom Systems
May 1999
Benchmarking Methodology for LAN Switching Devices
<draft-ietf-bmwg-mswitch-01.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Test setup . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Frame formats and sizes . . . . . . . . . . . . . . . . . . . . 3
5. Benchmarking Tests . . . . . . . . . . . . . . . . . . . . . . 4
5.1 Fully meshed throughput, frame loss and forwarding rates . . 4
5.2 Partially meshed overloading . . . . . . . . . . . . . . . . 7
5.3 Head of line blocking . . . . . . . . . . . . . . . . . . . . 10
5.4 Partially meshed multiple devices . . . . . . . . . . . . . . 13
5.5 Multiple streams of unidirectional traffic . . . . . . . . . 15
5.6 Filter illegal frames . . . . . . . . . . . . . . . . . . . . 18
5.7 Broadcast frame handling and latency . . . . . . . . . . . . 20
5.8 Maximum forwarding rate and minimum interframe gap . . . . . 21
5.9 Address caching capacity . . . . . . . . . . . . . . . . . . 23
5.10 Address learning rate . . . . . . . . . . . . . . . . . . . . 26
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 28
7. Authors' Address . . . . . . . . . . . . . . . . . . . . . . . 28
Appendix A: Formulas . . . . . . . . . . . . . . . . . . . . . . 29
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1. Introduction
This document is intended to provide methodology for the benchmarking
of local area network (LAN) switching devices. It extends the
methodology already defined for benchmarking network interconnecting
devices in RFC 2544 to switching devices.
This RFC primarily deals with devices which switch frames at the
Medium Access Control (MAC) layer. It provides a methodology for
benchmarking switching devices, forwarding performance, congestion
control, latency, address handling and filtering. In addition to
defining the tests, this document also describes specific formats for
reporting the results of the tests.
A previous document, "Benchmarking Terminology for LAN Switching
Devices" (RFC 2285), defined many of the terms that are used in this
document. The terminology document SHOULD be consulted before
attempting to make use of this document.
2. Requirements
The following RFCs SHOULD be consulted before attempting to make use
of this document:
* RFC 1242 "Benchmarking Terminology for Network Interconnect
Devices"
* RFC 2285 "Benchmarking Terminology for LAN Switching Devices"
* RFC 2544 "Benchmarking Methodology for Network Interconnect
Devices"
For the sake of clarity and continuity, this RFC adopts the template
for benchmarking tests set out in Section 26 of RFC 2544.
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.
3. Test setup
This document extends the general test setup described in section 6
of RFC 2544 to the benchmarking of LAN switching devices. RFC 2544
primarily describes non-meshed traffic where input and output
interfaces are grouped in mutually exclusive sending and receiving
pairs. In fully meshed traffic, each interface of a DUT/SUT is set
up to both receive and transmit frames to all the other interfaces
under test.
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Prior to each test run, the DUT/SUT MUST learn the MAC addresses used
in the test and the address learning SHOULD be verified. Addresses
not learned will be forwarded as flooded frames and reduce the amount
of correctly forwarded frames. The rate at which address learning
frames are offered may have to be adjusted to be as low as 50 frames
per second or even less, to guarantee successful learning. The
DUT/SUT address aging time SHOULD be configured to be greater than
the period of the learning phase of the test plus the test duration
plus any configuration time required by the testing device.
Addresses SHOULD NOT age out until the test duration is completed.
More than one learning trial may be needed for the association of the
address to the port to occur.
If a DUT/SUT uses a hashing algorithm with address learning, the
DUT/SUT may not learn the necessary addresses to perform the tests.
The format of the MAC addresses MUST be adjustable so that the
address mapping may be re-arranged to make a DUT/SUT learn addresses
without confusion.
It is recommended that SNMP and Spanning Tree be disabled when bench-
marking switching devices unless investigating overhead behavior. If
such protocols cannot be turned off, it is recommended that the
levels of offered load be reduced (less than 100%) to allow for
the additional management frames.
4. Frame formats and sizes
The frame format is defined in RFC 2544 section 8 and MUST contain a
unique signature field located in the UDP DATA area of the Test Frame
(see Appendix C of RFC 2544). The purpose of the signature field is
filter out frames that are not part of the offered load.
The signature field MUST be unique enough to identify the frames not
originating from the DUT/SUT. The signature field SHOULD be located
after byte 56 (ISO/IEC 8802-3 collision window) or at the end of the
frame. The length, contents and method of detection is not defined
in this memo.
The signature field MAY have a unique identifier per port. This
would filter out misforwarded frames. It is possible for a DUT/SUT
to strip off the MAC layer, send it through its switching matrix,
and transmit it out with the correct destination MAC address but the
wrong payload.
For frame sizes, refer to RFC 2544, section 9.
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There are three possible frame formats for layer 2 Ethernet switches:
standard MAC Ethernet frames, standard MAC Ethernet frames
with vendor-specific tags added to them, and IEEE 802.3ac
frames tagged to accommodate 802.3p&q. The two types of tagged
frames may exceed the standard maximum length frame of 1518 bytes,
and may not be accepted by the interface controllers of some
DUT/SUTs. It is recommended to check the compatibility of the DUT/SUT
with tagged frames before testing.
Devices switching tagged frames of over 1518 bytes will have a lower
maximum forwarding rate than standard untagged frames.
5. Benchmarking Tests
The following tests offer objectives, procedures, and reporting
formats for benchmarking LAN switching devices.
5.1 Fully meshed throughput, frame loss and forwarding rates
5.1.1 Objective
To determine the throughput, frame loss and forwarding rates of
DUT/SUTs offered fully meshed traffic as defined in RFC 2285.
5.1.2 Setup Parameters
When offering bursty full meshed traffic, the following parameters
MUST be defined. Each parameter is configured with the following
considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Interframe Gap (IFG) - The IFG between frames inside a burst
MUST be at the minimum specified by the standard (9.6 us for
10Mbps Ethernet, 960 ns for 100Mbps Ethernet, and 96 ns for
1 Gbps Ethernet).
Interburst Gap (IBG) - This is the interval between bursts of
traffic. Refer to Appendix A Formulas, for the formula used to
compute IBG.
Duplex mode - Half duplex or full duplex.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
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In half duplex mode, exactly half of the intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 7440 frames received per second and 7440 frames
transmitted per second (for 10Mbps Ethernet).
In full duplex mode, the entire intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 14880 frames received per second and 14880 frames
transmitted per second (for 10Mbps Ethernet).
Burst Size - The burst size defines the number of frames sent
back-to-back at the minimum legal IFG (96 bit times) before
pausing transmission to receive frames. Burst sizes
SHOULD vary between 1 and 930 frames. A burst size of 1 will
simulate non-bursty traffic.
Addresses per port - Represents the number of addresses which
are being tested for each port. Number of addresses SHOULD be a
binary exponential (i.e. 1, 2, 4, 8, 16, 32, 64, 128, 256, ...).
Recommended values are 1, 16 and 256.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
5.1.3 Procedure
All ports MUST transmit the exact number of frames. All ports SHOULD
start transmitting their frames within 1% of the test duration. For
a test duration of 10 seconds, all ports SHOULD have started
transmitting frames with 100 milliseconds of each other.
Each port in the test MUST send frames to all other ports in a
round robin type fashion. The following table shows how each port in
a test MUST transmit frames to all other ports in the test. In this
example, there are six ports with 1 address per port:
Source Port Destination Ports (in order of transmission)
Port #1 2 3 4 5 6 2...
Port #2 3 4 5 6 1 3...
Port #3 4 5 6 1 2 4...
Port #4 5 6 1 2 3 5...
Port #5 6 1 2 3 4 6...
Port #6 1 2 3 4 5 1...
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As shown in the table, there is an equal distribution of destination
addresses for each transmit opportunity. This keeps the test balanced
so that one destination port is not overloaded by the test algorithm
and all ports are equally and fully loaded throughout the test. Not
following this algorithm exactly will produce inconsistent results.
For tests using multiple addresses per port, the actual port
destinations are the same as described above and the actual
source/destination address pairs SHOULD be chosen randomly to
exercise the DUT/SUT's ability to perform address lookups.
For every address, the testing device MUST send learning frames to
allow the DUT/SUT to update its address tables properly.
5.1.4 Measurements
Each port should receive the same number of frames that it
transmitted. Each receiving port MUST categorize, then count the
frames into one of two groups:
1.) Received Frames: received frames MUST have the correct
destination MAC address and SHOULD match a signature field.
2.) Flood count: defined in RFC 2285 3.8.3.
Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
Frame loss rate of the DUT/SUT SHOULD be reported as defined in
RFC 2544 section 26.3 with the following notes: Frame loss rate
SHOULD be measured at the end of the test duration. The term "rate",
for this measurement only, does not imply the units in the fashion of
"per seconds."
Throughput measurement is defined in RFC 2544.
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
Forwarding rate at maximum offered load (FRMOL) MUST be reported
as the number of frames per second that a device can successfully
transmit to the correct destination interface in response to the
maximum offered load as defined in RFC 2285, section 3.6. The
maximum offered load MUST also be cited.
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Maximum forwarding rate (MFR) MUST be reported as the highest
forwarding rate of a DUT/SUT taken from an iterative set of
forwarding rate measurements. The load applied to the device MUST
also be cited.
5.1.5 Reporting format
The results for these tests SHOULD be reported in the form of a
graph. The x coordinate SHOULD be the frame size, the y coordinate
SHOULD be the test results. There SHOULD be at least two lines on
the graph, one plotting the theoretical and one plotting the test
results.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.2 Partially meshed overloading
5.2.1 Objective
To determine the throughput when transmitting from/to multiple ports
and to/from one port. As with the fully meshed throughput test, this
test is a measure of the capability of the DUT to switch frames
without frame loss. Results of this test can be used to determine
the ability of the DUT to utilize an Ethernet port when switching
traffic from multiple Ethernet ports.
5.2.2 Setup Parameters
When offering bursty meshed traffic, the following parameters MUST
be defined. Each parameter is configured with the following
considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Traffic Direction - Traffic can be generated in one direction, the
reverse direction, or both directions.
Interframe Gap (IFG) - The IFG between frames inside a burst
MUST be at the minimum specified by the standard (9.6 us for
10Mbps Ethernet, 960 ns for 100Mbps Ethernet, and 96 ns for
1 Gbps Ethernet).
Interburst Gap (IBG) - This is the interval between bursts of
traffic. Refer to Appendix A, Calculating Interburst Gap, for
the formula used to compute IBG.
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Duplex mode - Half duplex or full duplex.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
In half duplex mode, exactly half of the intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 7440 frames received per second and 7440 frames
transmitted per second (for 10Mbps Ethernet).
In full duplex mode, the entire intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 14880 frames received per second and 14880 frames
transmitted per second (for 10Mbps Ethernet).
Burst Size - The burst size defines the number of frames sent
back-to-back at the minimum legal IFG (96 bit times) before
pausing transmission to receive frames. Burst sizes
SHOULD vary between 1 and 930 frames. A burst size of 1 will
simulate non-bursty traffic.
Addresses per port - Represents the number of addresses which
are being tested for each port. Number of addresses SHOULD be a
binary exponential (i.e. 1, 2, 4, 8, 16, 32, 64, 128, 256, ...).
Recommended values are 1, 16 and 256.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
5.2.3 Procedure
In this test, each transmitting port MUST transmit the exact number
of frames. Depending upon traffic direction, some or all of the
ports will be transmitting.
Frames transmitted from the Many Ports MUST be destined to the One
port. Frames transmitted from the One Port MUST be destined to the
Many ports in a round robin type fashion. See section 5.1.3 for a
description of the round robin fashion.
For tests using multiple addresses per port, the actual port
destinations are the same as described above and the actual
source/destination address pairs SHOULD be chosen randomly to
exercise the DUT/SUT's ability to perform address lookups.
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+----------+
| |
| Many | <--------
| | \
+----------+ \
\
+----------+ \ +-------------+
| | ------------> | |
| Many | <-----------------------> | One |
| | ------------> | |
+----------+ / +-------------+
/
+----------+ /
| | /
| Many | <-------
| |
+----------+
For every address, the testing device MUST send learning frames to
allow the DUT/SUT to update its address tables properly.
5.2.4 Measurements
Each receiving port MUST categorize, then count the frames into one
of two groups:
1.) Received Frames: received frames MUST have the correct
destination MAC address and SHOULD match a signature field.
2.) Flood count: defined in RFC 2285 3.8.3.
Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
Forwarding rate at maximum offered load (FRMOL) MUST be reported
as the number of frames per second that a device can successfully
transmit to the correct destination interface in response to the
maximum offered load as defined in RFC 2285, section 3.6. The
maximum offered load MUST also be cited.
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Maximum forwarding rate (MFR) MUST be reported as the highest
forwarding rate of a DUT/SUT taken from an iterative set of
forwarding rate measurements. The load applied to the device MUST
also be cited.
5.2.5 Reporting Format
The results for these tests SHOULD be reported in the form of a
graph. The x coordinate SHOULD be the frame size, the y coordinate
SHOULD be the test results. There SHOULD be at least two lines on
the graph, one plotting the theoretical and one plotting the test
results.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.3 Head-of-line blocking
5.3.1 Objective
To determine how a DUT handles congestion. Namely, does the device
implement congestion control and does congestion on one port
affect an uncongested port?
5.3.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Duplex mode - Half duplex or full duplex.
Interframe Gap (IFG) - The IFG between frames MUST be at the
minimum specified by the standard (9.6 us for 10Mbps Ethernet,
960 ns for 100Mbps Ethernet, and 96 ns for 1 Gbps Ethernet).
Addresses per port - Represents the number of addresses which
are being tested for each port. Number of addresses SHOULD be a
binary exponential (i.e. 1, 2, 4, 8, 16, 32, 64, 128, 256, ...).
Recommended values are 1, 16 and 256.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
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5.3.3 Procedure
This test MUST consist of a multiple of four ports. Four ports are
REQUIRED and MAY be expanded to fully utilize the DUT/SUT in
increments of four. Each group of four will contain a test block
with two of the ports as source transmitters and two of the ports as
receivers. The diagram below depicts the flow of traffic between the
switch ports:
+----------+ 50 % MOL +-------------+
| | ------------------------> | |
| | 50 % MOL | uncongested |
| | --------- | |
+----------+ \ +-------------+
\
\
\
+----------+ \ +-------------+
| | ---------> | |
| | 100 % MOL | congested |
| | ------------------------> | |
+----------+ +-------------+
Both source transmitters MUST transmit the exact number of frames.
The first source MUST transmit frames at the MOL with the destination
address of the two receive ports in an alternating order. The first
frame to the uncongested receive port, second frame to the congested
receive port, then repeat. The second source transmitter MUST
transmit frames at the MOL only to the congested receive port.
Both receive ports SHOULD distinguish between frames originating from
the source ports and frames originating from the DUT/SUT. Only
frames from the source ports SHOULD be counted.
The uncongested receive port should be receiving at a rate of half
the MOL. The number of frames received on the uncongested port
SHOULD be 50% of the frames transmitted by the first source
transmitter. The congested receive port should be receiving at the
MOL. The number of frames received on the congested port should be
between 100% and 150% of the frames transmitted by one source
transmitter.
Frames destined to uncongested ports in a switch device should not
be dropped due to other ports being congested, even if the source
is sending to both the congested and uncongested ports.
5.3.4 Measurements
Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
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Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
Frame loss rate of the DUT/SUT's congested and uncongested ports MUST
be reported as defined in RFC 2544 section 26.3 with the following
notes: Frame loss rate SHOULD be measured at the end of the test
duration. The term "rate", for this measurement only, does not imply
the units in the fashion of "per seconds."
Forwarding rate (FR) of the DUT/SUT's congested and uncongested ports
MUST be reported as the number of frames per second that the device
is observed to successfully transmit to the correct destination
interface in response to a specified offered load. The offered load
MUST also be cited.
5.3.5 Reporting format
This test MUST report the frame lost rate at the uncongested port,
the maximum forwarding rate (at 50% offered load) at the uncongested
port, and the frame lost rate at the congested port. This test MAY
report the frame counts transmitted and frame counts received by the
ports.
If the DUT implements a flow control mechanism, an indication of this
is presented by observing no frame loss on the congested port. It
should be noted that this test expects the overall load to the
congested port to be greater than 100%. Therefore if the load is
greater than 100% and no frame loss is detected, then the DUT must be
implementing a flow control mechanism. The type of flow control
mechanism used is beyond the scope of this memo.
If there is frame loss at the uncongested port, "Head of Line"
blocking exists. The DUT cannot forward the amount of traffic to the
congested port and as a result it is also losing frames destined to
the uncongested port.
It should be noted that some DUTs may not be able to handle the 100%
load presented at the input port. In this case, there may be frame
loss reported at the uncongested port which is due to the load at the
input port rather than the congested port's load.
If the uncongested frame loss is reported as zero, but the maximum
forwarding rate is less than 7440 (for 10Mbps Ethernet), then this
may be an indication of congestion control being enforced by the DUT.
In this case, the congestion control is affecting the throughput of
the uncongested port.
If no congestion control is detected, the expected percentage frame
loss for the congested port is 33% at 150% overload. It is receiving
100% load from 1 port, and 50% from another, and can only get 100%
possible throughput, therefore having a frame loss rate of 33%
(150%-50%/150%).
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5.4 Partially Meshed Multiple Devices
5.4.1 Objective
To determine the throughput, frame loss and forwarding rates of two
switching devices equipped with multiple Ethernet ports and one high
speed backbone uplink (Gigabit Ethernet, ATM, SONET).
5.4.2 Setup Parameters
When offering bursty partially meshed traffic, the following
parameters MUST be defined. Each variable is configured with the
following considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Interframe Gap (IFG) - The IFG between frames inside a burst
MUST be at the minimum specified by the standard (9.6 us for
10Mbps Ethernet, 960 ns for 100Mbps Ethernet, and 96 ns for
1 Gbps Ethernet).
Interburst Gap (IBG) - This is the interval between bursts of
traffic. Refer to Appendix A, Calculating Interburst Gap, for
the formula used to compute IBG.
Duplex mode - Half duplex or full duplex.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
In half duplex mode, exactly half of the intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 7440 frames received per second and 7440 frames
transmitted per second (for 10Mbps Ethernet).
In full duplex mode, the entire intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 14880 frames received per second and 14880 frames
transmitted per second (for 10Mbps Ethernet).
Burst Size - The burst size defines the number of frames sent
back-to-back at the minimum legal IFG (96 bit times) before
pausing transmission to receive frames. Burst sizes
SHOULD vary between 1 and 930 frames.
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Addresses per port - Represents the number of addresses which
are being tested for each port. Number of addresses SHOULD be a
binary exponential (i.e. 1, 2, 4, 8, 16, 32, 64, 128, 256, ...).
Recommended values are 1, 16 and 256.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
Local Traffic - A Boolean value of ON or OFF. The frame
sequence
algorithm MAY be altered to remove local traffic. With local
traffic ON, the algorithm is exactly the same as a fully meshed
throughput. With local traffic OFF, the port sends frames to all
other ports on the other side of the backbone uplink in a round
robin type fashion.
5.4.3 Procedure
All ports MUST transmit the exact number of frames. All ports SHOULD
start transmitting their frames within 1% of the test duration. For
a test duration of 10 seconds, all ports SHOULD have started
transmitting frames with 100 milliseconds of each other.
Each port in the test MUST send frames to all other ports in a
round robin type fashion as defined in section 5.1. Local traffic
MAY be removed from the round robin list in order to send the entire
load across the backbone uplink.
For tests using multiple addresses per port, the actual port
destinations are the same as described above and the actual
source/destination address pairs SHOULD be chosen randomly to
exercise the DUT/SUT's ability to perform address lookups.
For every address, the testing device MUST send learning frames to
allow the DUT/SUT to update its address tables properly.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.4.4 Measurements
Each port should receive the same amount of frames that is
transmitted. Each receiving port MUST categorize, then count the
frames into one of two groups:
1.) Received frames MUST have the correct destination MAC address
and SHOULD match a signature field.
2.) Flood count (defined in RFC 2285 3.8.3).
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Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
Frame loss rate of the DUT/SUT SHOULD be reported as defined in
RFC 2544 section 26.3 with the following notes: Frame loss rate
SHOULD be measured at the end of the test duration. The term "rate",
for this measurement only, does not imply the units in the fashion of
"per seconds."
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
Forwarding rate at maximum offered load (FRMOL) MUST be reported
as the number of frames per second that a device can successfully
transmit to the correct destination interface in response to the
maximum offered load as defined in RFC 2285, section 3.6. The
maximum offered load MUST also be cited.
Maximum forwarding rate (MFR) MUST be reported as the highest
forwarding rate of a DUT/SUT taken from an iterative set of
forwarding rate measurements. The load applied to the device MUST
also be cited.
5.4.5 Reporting format
The results for these tests SHOULD be reported in the form of a
graph. The x coordinate SHOULD be the frame size, the y coordinate
SHOULD be the test results. There SHOULD be at least two lines on
the graph, one plotting the theoretical and one plotting the test
results.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.5 Multiple streams of unidirectional traffic
5.5.1 Objective
To determine the throughput of the DUT/SUT when presented multiple
streams of unidirectional traffic with half of the ports on the
DUT/SUT are receiving frames destined to the other half of the
ports.
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5.1.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Duplex mode - Half duplex or full duplex.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
In half duplex mode, exactly half of the intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 7440 frames received per second and 7440 frames
transmitted per second (for 10Mbps Ethernet).
In full duplex mode, the entire intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 14880 frames received per second and 14880 frames
transmitted per second (for 10Mbps Ethernet).
Addresses per port - Represents the number of addresses which
are being tested for each port. Number of addresses SHOULD be a
binary exponential (i.e. 1, 2, 4, 8, 16, 32, 64, 128, 256, ...).
Recommended values are 1, 16 and 256.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
5.5.3 Procedure
Ports do not send and receive frames simultaneously. As a
consequence, there should be no collisions unless the DUT is
misforwarding frames, generating flooded or Spanning-Tree frames or
is enabling some flow control mechanism. Ports used for this test
are either transmitting or receiving, but not both. Those ports which
are transmitting send frames destined to addresses corresponding to
each of the ports receiving. This creates a unidirectional mesh of
traffic.
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All ports MUST transmit the exact number of frames. All ports SHOULD
start transmitting their frames within 1% of the test duration. For
a test duration of 10 seconds, all ports SHOULD have started
transmitting frames with 100 milliseconds of each other.
Each transmitting port in the test MUST send frames to all receiving
ports in a round robin type fashion. The following table shows how
each port in a test MUST transmit frames to all other ports in the
test. In this 8 port example, port 1 through 4 are transmitting and
ports 5 through 8 are receiving; each with 1 address per port:
Source Port, then Destination Ports (in order of transmission)
Port #1 5 6 7 8 5 6...
Port #2 6 7 8 5 6 7...
Port #3 7 8 5 6 7 8...
Port #4 8 5 6 7 8 5...
As shown in the table, there is an equal distribution of destination
addresses for each transmit opportunity. This keeps the test balanced
so that one destination port is not overloaded by the test algorithm
and all receiving ports are equally and fully loaded throughout the
test. Not following this algorithm exactly will product inconsistent
results.
For tests using multiple addresses per port, the actual port
destinations are the same as described above and the actual
source/destination address pairs SHOULD be chosen randomly to
exercise the DUT/SUT's ability to perform address lookups.
For every address, the testing device MUST send learning frames to
allow the DUT/SUT to load its address tables properly. The address
table's aging time SHOULD be set sufficiently longer than the
learning time and test duration time combined. If the address table
ages out during the test, the results will show a lower performing
DUT/SUT.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.5.4 Measurements
Each port should receive the same number of frames that it
transmitted. Each receiving port MUST categorize, then count the
frames into one of two groups:
1.) Received Frames: received frames MUST have the correct
destination MAC address and SHOULD match a signature field.
2.) Flood count: defined in RFC 2285 3.8.3.
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Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
Frame loss rate of the DUT/SUT SHOULD be reported as defined in
RFC 2544 section 26.3 with the following notes: Frame loss rate
SHOULD be measured at the end of the test duration. The term "rate",
for this measurement only, does not imply the units in the fashion of
"per seconds."
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
Forwarding rate at maximum offered load (FRMOL) MUST be reported
as the number of frames per second that a device can successfully
transmit to the correct destination interface in response to the
maximum offered load as defined in RFC 2285, section 3.6. The
maximum offered load MUST also be cited.
Maximum forwarding rate (MFR) MUST be reported as the highest
forwarding rate of a DUT/SUT taken from an iterative set of
forwarding rate measurements. The load applied to the device MUST
also be cited.
5.1.5 Reporting format
The results for these tests SHOULD be reported in the form of a
graph. The x coordinate SHOULD be the frame size, the y coordinate
SHOULD be the test results. There SHOULD be at least two lines on
the graph, one plotting the theoretical and one plotting the test
results.
To measure the DUT/SUT's ability to switch traffic while performing
many different address lookups, the number of addresses per port
MAY be increased in a series of tests.
5.6 Filter illegal frames
5.6.1 Objective
The objective of the filter illegal frame test is to determine
the behavior of the DUT under errors or abnormal frame conditions.
The results of the test indicate if the DUT/SUT filters the errors,
or simply propagates the errored frames along to the destination.
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5.1.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
5.6.3 Procedure
Each of the illegal frames for Ethernet MUST be checked:
Oversize - The DUT/SUT MAY filter frames larger than 1518 bytes
from being propagated through the DUT/SUT (ISO 8802-3 4.2.4.2.1).
Oversized frames transmitted to the DUT/SUT should not appear as
receive frames or as error frames on any port. DUT/SUT supporting
tagged Frames MAY forward frames up to and including 1522 bytes
long (IEEE 802.3ac 4.2.4.2.1).
Undersize - The DUT/SUT MUST filter frames less than 64 bytes from
being propagated through the DUT/SUT (per ISO 8802-3 4.2.4.2.2).
Undersized frames (or collision fragments) transmitted to the DUT/SUT
MUST not appear as receive frames or as error frames on another port.
CRC Errors - The DUT/SUT MUST filter frames that fail the Frame Check
Sequence Validation (ISO 8802-3 4.2.4.1.2) from being propagated
through the DUT/SUT. Frames with an invalid CRC transmitted to the
DUT/SUT should not appear as receive frames or as error frames on
another port.
Dribble Bit Errors - The DUT/SUT MUST correct and forward frames
containing dribbling bits. Frames transmitted to the DUT/SUT that do
not end in an octet boundary but contain a valid frame check sequence
MUST be accepted by the DUT/SUT (ISO 8802-3 4.2.4.2.1) and forwarded
to the correct receive port with the frame ending in an octet
boundary (ISO 8802-3 3.4).
Alignment Errors - The DUT/SUT MUST filter frames than fail the Frame
Check Sequence Validation AND do not end in an octet boundary. This
is a combination of a CRC error and a Dribble Bit error. When both
errors are occurring in the same frame, the DUT/SUT MUST determine
the CRC error takes precedence and filters the frame (ISO 8802-3
4.2.4.1.2) from being propagated.
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5.7 Broadcast frame handling and latency test
5.7.1 Objective
The objective of the Broadcast Frame Handling and Latency Test is to
determine the throughput and latency of the DUT when handling
broadcast traffic. The ability to forward broadcast frames will
depend on special features built into the device for that purpose.
It is therefore necessary to determine the ability of switches to
handle broadcast frames, since there may be many different ways of
implementing such a feature.
5.7.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Duplex mode - Half duplex or full duplex.
Load / Port - Load per port is expressed in a percentage of the
medium's maximum intended load possible. The actual transmitted
frame per second is dependent upon half duplex or full duplex
operation. The test SHOULD be run multiple times with a different
load per port in each case.
In half duplex mode, exactly half of the intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 7440 frames received per second and 7440 frames
transmitted per second (for 10Mbps Ethernet).
In full duplex mode, the entire intended load SHOULD be
transmitted to each of the ports under test. For example, with a
100% load of 64-byte frames, the intended load for each port under
test is 14880 frames received per second and 14880 frames
transmitted per second (for 10Mbps Ethernet).
Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
5.7.3 Procedure
For this test, there are two parts to be run.
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Broadcast Frame Throughput - This portion of the test uses a single
source test port to transmit frames with a broadcast address using
the frame specified in RFC 2544. Selected receive ports then
measure the forwarding rate and Frame loss rate.
Broadcast Frame Latency - This test uses the same setup as the
Broadcast Frame throughput, but instead of a large stream of frames
being sent, only one frame is sent and the latency to each of the
receive ports are measured in seconds.
5.7.4 Measurements
Frame loss rate of the DUT/SUT SHOULD be reported as defined in
RFC 2544 section 26.3 with the following notes: Frame loss rate
SHOULD be measured at the end of the test duration. The term "rate",
for this measurement only, does not imply the units in the fashion of
"per seconds."
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
5.8 Maximum forwarding rate and minimum interframe gap
5.8.1 Objective
The objective of the Maximum forwarding rate test is to find the
peak value of the Forwarding Rate when the Offered Load is varied
between the throughput (RFC 1242) and the Maximum Offered Load
(RFC 2285).
The Minimum Interframe gap Test overloads a DUT/SUT port and measure
the output for forward pressure. If the DUT/SUT transmits frames
with an interframe gap less than 96 bits (ISO 8802-3 4.2.3.2.2), then
forward pressure is detected.
5.8.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Frame Size - Recommended frame sizes are 64, 128, 256, 512, 1024,
1280 and 1518 bytes, per RFC 2544 section 9. The four CRC bytes
are included in the frame size specified.
Duplex mode - Half duplex or full duplex.
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Test Duration - Test duration SHOULD be between 1 and 300 seconds.
RFC 2285 recommends a duration of at least 10 seconds for each
test.
Step Size - The minimum incremental resolution that the Offered
Load (OL) will be incremented in frames per second. The smaller
the step size, the more accurate the measurement and the more
iterations required. As the Offered Load approaches the Maximum
Offered Load, the minimum step size will increase because of gap
resolution on the testing device.
5.8.3 Procedure
If the throughput and the Maximum Offered Load are the same, then
Maximum Forwarding rate is equal to the Maximum Offered Load.
This test SHOULD at a minimum be performed in a two-port
configuration as described below. Learning frames MUST be sent to
allow the DUT/SUT to update its address tables properly.
The first port (port 1) device transmits frames at the Offered Load
to the DUT/SUT. A second port (port 2) receives frames from the
DUT/SUT and measures the Forwarding Rate.
The Offered Load is incremented for each Step Size to find the
Maximum Forwarding Rate. The algorithm for the test is as follows:
CONSTANT
MOL = ... frames/sec; {Maximum Offered Load}
VARIABLE
MFR := 0 frames/sec; {Maximum Forwarding Rate}
OLOAD := starting throughput in frames/sec; {offered load}
STEP := ... frames/sec; {Step Size}
BEGIN
OLOAD := OLOAD - STEP;
DO
BEGIN
OLOAD := OLOAD + STEP
IF (OLOAD > MOL) THEN
BEGIN
OLOAD := MOL
END
AddressLearning; {Port 2 broadcast frame with its source
address}
Transmit(OLOAD); {Port 1 sends frames to Port 2 at Offered load}
IF (Port 2 Forwarding Rate > MFR) THEN
BEGIN
MFR := Port 2 Forwarding Rate; {A higher value than before}
END
END
WHILE (OLOAD >= MOL); {MFR equals Maximum Forwarding Rate}
DONE
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The Minimum Interframe gap test SHOULD, at a minimum, be performed in
a two-port configuration as described below. Learning frames MUST be
sent to allow the DUT/SUT to update its address tables properly.
The first port (port 1) device transmits frames with an interframe
gap of 88 bits to the DUT/SUT. This will apply forward pressure to
the DUT/SUT and overload it at a rate of one byte per frame. The
frames MUST be constructed with a source address of port 1 and a
destination address of port 2.
A second port (port 2) receives frames from the DUT/SUT and measures
the Forwarding Rate. The measured Forwarding Rate SHOULD not exceed
the medium's maximum theoretical utilization.
5.8.4 Measurements
Port 2 MUST categorize, then count the frames into one of two groups:
1.) Received Frames: received frames MUST have the correct
destination MAC address and SHOULD match a signature field.
2.) Flood count: defined in RFC 2285 3.8.3.
Any frame received which does not have the correct destination
address MUST not be counted as a received frame and SHOULD be counted
as part of a flood count.
Any frame originating from the DUT/SUT MUST not be counted as a
received frame. Frames originating from the DUT/SUT MAY be counted
as flooded frames or not counted at all.
5.8.5 Reporting format
Maximum forwarding rate (MFR) MUST be reported as the highest
forwarding rate of a DUT/SUT taken from an iterative set of
forwarding rate measurements. The load applied to the device MUST
also be cited.
Forwarding rate (FR) of the DUT/SUT SHOULD be reported as the number
of frames per second that the device is observed to successfully
transmit to the correct destination interface in response to a
specified offered load. The offered load MUST also be cited.
5.9 Address Caching Capacity
5.9.1 Objective
To determine the address caching capacity of a LAN switching device
as defined in RFC 2285, section 3.8.1.
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5.9.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
Age Time - The maximum time that a DUT/SUT will keep a learned
address in its forwarding table.
Addresses Learning Rate - The rate at which new addresses are
offered to the DUT/SUT to be learned. The rate at which address
learning frames are offered may have to be adjusted to be as low as
50 frames per second or even less, to guarantee successful
learning.
Initial Addresses - The initial number of addresses to start the
test with. The number MUST be between 1 and the maximum number
supported by the implementation.
5.9.3 Procedure
The aging time of the DUT/SUT MUST be known. The aging time MUST be
longer than the time necessary to produce frames at the specified
rate. If a low frame rate is used for the test, then it may be
possible that sending a large amount of frames may actually take
longer than the aging time.
This test SHOULD at a minimum be performed in a three-port
configuration as described below.
This test MUST consist of a multiple of three ports. Three ports
are REQUIRED and MAY be expanded to fully utilized the DUT/SUT in
increments of three. Each group of three will contain a test
block as follows:
The first port (port 1) send frames with varying source addresses and
a fixed destination address corresponding to the MAC address of the
receiving port (port 2) of the DUT/SUT. By receiving frames with
varying source addresses, the DUT/SUT will learn these new addresses
from the sending port of the test device. The source addresses MAY
be in sequential order.
A second port (port 2) acts as the receiving port for the address
learning frames. This port also sends test frames back to the
addresses learned on the first port. The algorithm for this is
explained below.
A third port (port 3) on the DUT/SUT act as a monitoring port to
listen for flooded frames.
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It is highly recommended that SNMP, Spanning Tree, and any other
frames originating from the DUT/SUT be disabled when running this
test. If such protocols cannot be turned off, the flood count MUST
be modified only to count frame originating from port 1 and MUST
NOT count frames originating from the DUT/SUT.
The algorithm for the test is as follows:
CONSTANT
AGE = ...; {value greater that DUT aging time}
MAX = ...; {maximum address support by implementation}
VARIABLE
LOW := 0; {Highest passed valve}
HIGH := MAX; {Lowest failed value}
N := ...; {user specified initial starting point}
BEGIN
DO
BEGIN
PAUSE(AGE); {Age out any learned addresses}
AddressLearning(Port 2); {broadcast a frame with its source
Address and broadcast destination}
AddressLearning(Port 1); {N frames with varying source
addresses
to Port 2}
Transmit(Port 2); {N frames with varying destination addresses
corresponding to Port 1}
IF (Port 3 receive frame != 0) OR
(Port 1 receive frames < Port 2 transmit) THEN
BEGIN {Address Table of DUT/SUT was full}
HIGH := N;
END
ELSE
BEGIN {Address Table of DUT/SUT was NOT full}
LOW := N;
END
N := LOW + (HIGH - LOW)/2;
END WHILE (HIGH - LOW < 2);
END {Value of N equals number of addresses supported by DUT/SUT}
Using a binary search approach, the test targets the exact number of
addresses supported per port with consistent test iterations. Due
to the aging time of DUT/SUT address tables, each iteration may take
some time during the waiting period for the addresses to clear. If
possible, configure the DUT/SUT for a low value for the aging time.
Once the high and low values of N meet, then the threshold of address
handling has been found.
5.9.4 Measurements
Whether the offered addresses per port was successful forwarded
without flooding.
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5.9.5 Reporting format
After the test is run, results for each iteration SHOULD be displayed
in a table to include:
The number of addresses used for each test iteration (varied).
The intended load used for each test iteration (fixed).
Number of test frames that were transmitted by test port number 2.
This SHOULD match the number of addresses used for the test
iteration. Test frames are the frames sent with varying
destination addresses to confirm that the DUT/SUT has learned
all of the addresses for each test iteration.
The flood count on port 2 during the test portion of each test.
If the number is non-zero, this is an indication of the DUT/SUT
flooding a frame in which the destination address is not in the
address table.
The number of frames correctly forwarded to test port 1 during
the test portion of the test. Received frames MUST have the
correct destination MAC address and SHOULD match a signature
field. For a passing test iteration, this number should be equal
to the number of frames transmitted by port 2.
The flood count on port 1 during the test portion of each test.
If the number is non-zero, this is an indication of the DUT/SUT
flooding a frame in which the destination address is not in the
address table.
The flood count on port 3. If the value is not zero, then this
indicates that for that test iteration, the DUT/SUT could not
determine the proper destination port for that many frames. In
other words, the DUT/SUT flooded the frame to all ports since its
address table was full.
5.10 Address Learning Rate
5.10.1 Objective
To determine the rate of address learning of a LAN switching device
as defined in RFC 2285, section 3.8.2.
5.10.2 Setup Parameters
The following parameters MUST be defined. Each variable is
configured with the following considerations.
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Age Time - The maximum time that a DUT/SUT will keep a learned
address in its forwarding table.
Initial Addresses Learning Rate - The starting rate at which new
addresses are offered to the DUT/SUT to be learned.
Number of Addresses - The number of addresses that the DUT/SUT must
learn. The number MUST be between 1 and the maximum number
supported by the implementation. It is recommended no to exceed
the address caching capacity found in section 5.9
5.10.3 Procedure
The aging time of the DUT/SUT MUST be known. The aging time MUST be
longer than the time necessary to produce frames at the specified
rate. If a low frame rate is used for the test, then it may be
possible that sending a large amount of frames may actually take
longer than the aging time.
This test SHOULD at a minimum be performed in a three-port
configuration as described below.
This test MUST consist of a multiple of three ports. Three ports
are REQUIRED and MAY be expanded to fully utilized the DUT/SUT in
increments of three. Each group of three will contain a test
block as described in section 5.9.
An algorithm similar to the one used to determine address caching
capacity can be used to determine the address learning rate. This
test iterates the rate at which address learning frames are offered
by the test device connected to the DUT/SUT. It is recommended to
set the number of addresses offered to the DUT/SUT in this test to
the maximum caching capacity.
The address learning rate might be determined for different numbers
of addresses but in each test run, the number MUST remain constant
and SHOULD be equal to or less than the maximum address caching
capacity.
5.10.4 Measurements
Whether the offered addresses per port was successful forwarded
without flooding at the offered learning rate.
5.10.5 Reporting format
After the test is run, results for each iteration SHOULD be displayed
in a table:
The number of addresses used for each test iteration (fixed).
The intended load used for each test iteration (varied).
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Number of test frames that were transmitted by test port number 2.
This SHOULD match the number of addresses used for the test
iteration. Test frames are the frames sent with varying
destination addresses to confirm that the DUT/SUT has learned
all of the addresses for each test iteration.
The flood count on port 2 during the test portion of each test.
If the number is non-zero, this is an indication of the DUT/SUT
flooding a frame in which the destination address is not in the
address table.
The number of frames correctly forwarded to test port 1 during
the test portion of the test. Received frames MUST have the
correct destination MAC address and SHOULD match a signature
field. For a passing test iteration, this number should be equal
to the number of frames transmitted by port 2.
The flood count on port 1 during the test portion of each test.
If the number is non-zero, this is an indication of the DUT/SUT
flooding a frame in which the destination address is not in the
address table.
The flood count on port 3. If the value is not zero, then this
indicates that for that test iteration, the DUT/SUT could not
determine the proper destination port for that many frames. In
other words, the DUT/SUT flooded the frame to all ports since its
address table was full.
6. Security Considerations
This document does not yet address Security Considerations.
7. Authors' Address
Robert Mandeville
European Network Laboratories (ENL)
2, rue Helene Boucher
87286 Guyancourt Cedex
France
Phone: + 33 1 39 44 12 05
EMail: bob@enl.net
Jerry Perser
Netcom Systems
20550 Nordhoff St.
Chatsworth, CA 91311
USA
Phone: + 1 818 700 5100
Email: jerry_perser@netcomsystems.com
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Appendix A: Formulas
A.1 Calculating the InterBurst Gap
IBG is defined in RFC 2285 as the interval between two bursts. To
achieve a desired load, the follow Input Parameter need to be
defined:
LENGTH - Frame size in bytes including the CRC.
LOAD - The intended load in percent. Range is 0 to 100.
BURST - The number of frames in the burst (integer value).
SPEED - media's speed in bits/sec
Ethernet is 10,000,000 bits/sec
Fast Ethernet is 100,000,000 bits/sec
Gigabit Ethernet is 1,000,000,000 bits/sec
DUPLEX - A constant to adjust the transmit rate for full or half
duplex mode. In full duplex the value is 100, in half
duplex the value is 200.
IFG - A constant 96 bits for the minimum interframe gap.
The IBG (in seconds) can be calculated:
(DUPLEX/LOAD - 1) * BURST * (IFG + 64 + 8*LENGTH)] + IFG
IBG = ----------------------------------------------------------
SPEED
A.2 Calculating the Number of Bursts for the Test Duration
The number of burst for the test duration is rounded up to the
nearest
integer number. The follow Input Parameter need to be defined:
LENGTH - Frame size in bytes including the CRC.
BURST - The number of frames in the burst (integer value).
SPEED - media's speed in bits/sec
Ethernet is 10,000,000 bits/sec
Fast Ethernet is 100,000,000 bits/sec
Gigabit Ethernet is 1,000,000,000 bits/sec
IFG - A constant 96 bits for the minimum interframe gap.
IBG - Found in the above formula
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DURATION - Test duration in seconds.
An intermediate number of the Burst duration needs to be calculated
first:
IFG*(BURST-1) + BURST*(64 + 8*LENGTH)
TXTIME = -----------------------------------------
SPEED
Number of Burst for the Test Duration (rounded up):
DURATION
#OFBURSTS = --------------
(TXTIME + IBG)
Example:
LENGTH = 64 bytes per frame
LOAD = 100 % offered load
BURST = 24 frames per burst
SPEED = 10 Mbits/sec (Ethernet)
DUPLEX = 200 (half duplex)
DURATION = 10 seconds test
IBG = 1612.8 uS
TXTIME = 1603.2 uS
#OFBURSTS = 3110
Mandeville, Perser [Page 30]