draft-ietf-bmwg-lanswitch-06.txt   rfc2285.txt 
Network Working Group R. Mandeville Network Working Group R. Mandeville
INTERNET-DRAFT European Network Laboratories Request for Comments: 2285 European Network Laboratories
Expiration Date: January 1998 August 1997 Category: Informational February 1998
Benchmarking Terminology for LAN Switching Devices Benchmarking Terminology for LAN Switching Devices
<draft-ietf-bmwg-lanswitch-06.txt>
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Existing definitions . . . . . . . . . . . . . . . . . . . . . . 2
2. Existing definitions . . . . . . . . . . . . . . . . . . . . . . 3
3. Term definitions . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Term definitions . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1 Devices . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1.1 Device under test (DUT) . . . . . . . . . . . . . . . . 3 3.1.1 Device under test (DUT) . . . . . . . . . . . . . . . . 3
3.1.2 System under test (SUT) . . . . . . . . . . . . . . . . 4 3.1.2 System under test (SUT) . . . . . . . . . . . . . . . . 3
3.2 Traffic orientation. . . . . . . . . . . . . . . . . . . . . 4
3.2 Traffic orientation . . . . . . . . . . . . . . . . . . . . 4 3.2.1 Unidirectional traffic. . . . . . . . . . . . . . . . . 4
3.2.2 Bidirectional traffic . . . . . . . . . . . . . . . . . 5
3.2.1 Unidirectional traffic . . . . . . . . . . . . . . . . 4 3.3 Traffic distribution . . . . . . . . . . . . . . . . . . . . 6
3.2.2 Bidirectional traffic . . . . . . . . . . . . . . . . . 6 3.3.1 Non-meshed traffic. . . . . . . . . . . . . . . . . . . 6
3.3.2 Partially meshed traffic. . . . . . . . . . . . . . . . 7
3.3 Traffic distribution . . . . . . . . . . . . . . . . . . . . 7 3.3.3 Fully meshed traffic. . . . . . . . . . . . . . . . . . 8
3.4 Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3.1 One-to-one mapped traffic . . . . . . . . . . . . . . . 7 3.4.1 Burst . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3.2 Partially meshed traffic . . . . . . . . . . . . . . . 7 3.4.2 Burst size . . . . . . . . . . . . . . . . . . . . . . 10
3.3.3 Fully meshed traffic . . . . . . . . . . . . . . . . . 8 3.4.3 Inter-burst gap (IBG). . . . . . . . . . . . . . . . . 10
3.5 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.4 Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.5.1 Intended load (Iload) . . . . . . . . . . . . . . . . 11
3.5.2 Offered load (Oload) . . . . . . . . . . . . . . . . . 12
3.4.1 Burst . . . . . . . . . . . . . . . . . . . . . . . . 10 3.5.3 Maximum offered load (MOL) . . . . . . . . . . . . . . 13
3.4.2 Burst size . . . . . . . . . . . . . . . . . . . . . . 11
3.4.3 Inter-burst gap (IBG) . . . . . . . . . . . . . . . . 11
3.5 Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.5.1 Intended load (Iload) . . . . . . . . . . . . . . . . 12
3.5.2 Offered load (Oload) . . . . . . . . . . . . . . . . . 13
3.5.3 Maximum offered load (MOL) . . . . . . . . . . . . . . 14
3.5.4 Overloading . . . . . . . . . . . . . . . . . . . . . 14 3.5.4 Overloading . . . . . . . . . . . . . . . . . . . . . 14
3.6 Forwarding rates . . . . . . . . . . . . . . . . . . . . . 15 3.6 Forwarding rates . . . . . . . . . . . . . . . . . . . . . 15
3.6.1 Forwarding rate (FR) . . . . . . . . . . . . . . . . . 15
3.6.1 Forwarding rate (FR) . . . . . . . . . . . . . . . . . 16
3.6.2 Forwarding rate at maximum offered load (FRMOL). . . . 16 3.6.2 Forwarding rate at maximum offered load (FRMOL). . . . 16
3.6.3 Maximum forwarding rate (MFR). . . . . . . . . . . . . 17 3.6.3 Maximum forwarding rate (MFR). . . . . . . . . . . . . 16
3.7 Congestion control . . . . . . . . . . . . . . . . . . . . 17
3.7 Congestion control . . . . . . . . . . . . . . . . . . . . 18 3.7.1 Backpressure . . . . . . . . . . . . . . . . . . . . . 17
3.7.2 Forward pressure . . . . . . . . . . . . . . . . . . . 18
3.7.1 Backpressure . . . . . . . . . . . . . . . . . . . . . 18 3.7.3 Head of line blocking . . . . . . . . . . . . . . . . 19
3.7.2 Forward pressure . . . . . . . . . . . . . . . . . . . 19
3.7.3 Head of line blocking . . . . . . . . . . . . . . . . 20
3.8 Address handling . . . . . . . . . . . . . . . . . . . . . 20 3.8 Address handling . . . . . . . . . . . . . . . . . . . . . 20
3.8.1 Address caching capacity . . . . . . . . . . . . . . . 20
3.8.1 Address caching capacity . . . . . . . . . . . . . . . 21 3.8.2 Address learning rate . . . . . . . . . . . . . . . . 20
3.8.2 Address learning rate . . . . . . . . . . . . . . . . 21 3.8.3 Flood count . . . . . . . . . . . . . . . . . . . . . 21
3.8.3 Flood count . . . . . . . . . . . . . . . . . . . . . 22 3.9 Errored frame filtering . . . . . . . . . . . . . . . . . . 21
3.9 Errored frame filtering . . . . . . . . . . . . . . . . . . 22
3.9.1 Errored frames . . . . . . . . . . . . . . . . . . . . 22 3.9.1 Errored frames . . . . . . . . . . . . . . . . . . . . 22
3.10 Broadcasts . . . . . . . . . . . . . . . . . . . . . . . . 22
3.10 Broadcasts . . . . . . . . . . . . . . . . . . . . . . . . 23 3.10.1 Broadcast forwarding rate at maximum load . . . . . . 22
3.10.2 Broadcast latency . . . . . . . . . . . . . . . . . . 23
3.10.1 Broadcast forwarding rate at maximum load . . . . . . 23
3.10.2 Broadcast latency . . . . . . . . . . . . . . . . . . 24
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 24 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 24
5. References. . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6. Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . 24
7. Author's Address. . . . . . . . . . . . . . . . . . . . . . . . 24
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 25 8. Full Copyright Statement. . . . . . . . . . . . . . . . . . . . 25
7. Author's Address . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction 1. Introduction
This Request for Comments (RFC) is intended to provide terminology This document is intended to provide terminology for the benchmarking
for the benchmarking of local area network (LAN) switching devices. of local area network (LAN) switching devices. It extends the
It extends the terminology already defined for benchmarking network terminology already defined for benchmarking network interconnect
interconnect devices in RFCs 1242 and 1944 to switching devices. devices in RFCs 1242 and 1944 to switching devices.
Although it might be found useful to apply some of the terms defined Although it might be found useful to apply some of the terms defined
here to a broader range of network interconnect devices, this RFC here to a broader range of network interconnect devices, this RFC
primarily deals with devices which switch frames at the Medium primarily deals with devices which switch frames at the Medium Access
Access Control (MAC) layer. It defines terms in relation to the Control (MAC) layer. It defines terms in relation to the traffic put
traffic put to use when benchmarking switching devices, forwarding to use when benchmarking switching devices, forwarding performance,
performance, latency, address handling and filtering. congestion control, latency, address handling and filtering.
2. Existing definitions 2. Existing definitions
RFC 1242 "Benchmarking Terminology for Network Interconnect Devices" RFC 1242 "Benchmarking Terminology for Network Interconnect Devices"
should be consulted before attempting to make use of this document. should be consulted before attempting to make use of this document.
RFC 1944 "Benchmarking Methodology for Network Interconnect Devices" RFC 1944 "Benchmarking Methodology for Network Interconnect Devices"
contains discussions of a number of terms relevant to the contains discussions of a number of terms relevant to the
benchmarking of switching devices and should also be consulted. benchmarking of switching devices and should also be consulted.
For the sake of clarity and continuity this RFC adopts the template For the sake of clarity and continuity this RFC adopts the template
for definitions set out in Section 2 of RFC 1242. Definitions are for definitions set out in Section 2 of RFC 1242. Definitions are
indexed and grouped together in sections for ease of reference. indexed and grouped together in sections for ease of reference.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
"OPTIONAL" in this document are to be interpreted as described in document are to be interpreted as described in RFC 2119.
RFC 2119.
3. Term definitions 3. Term definitions
3.1 Devices 3.1 Devices
This group of definitions applies to all types of networking This group of definitions applies to all types of networking devices.
devices.
3.1.1 Device under test (DUT) 3.1.1 Device under test (DUT)
Definition: Definition:
The network forwarding device to which stimulus is offered and The network forwarding device to which stimulus is offered and
response measured. response measured.
Discussion: Discussion:
A single stand-alone or modular unit which receives frames on A single stand-alone or modular unit which receives frames on one
or more of its interfaces and then forwards them to one or more or more of its interfaces and then forwards them to one or more
interfaces according to the addressing information contained in interfaces according to the addressing information contained in
the frame. the frame.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
See Also: See Also:
system under test (SUT) (3.1.2) system under test (SUT) (3.1.2)
3.1.2 System Under Test (SUT) 3.1.2 System Under Test (SUT)
Definition: Definition:
The collective set of network devices to which stimulus is The collective set of network devices to which stimulus is offered
offered as a single entity and response measured. as a single entity and response measured.
Discussion: Discussion:
A system under test may be comprised of a variety of networking A system under test may be comprised of a variety of networking
devices. Some devices may be active in the forwarding decision- devices. Some devices may be active in the forwarding decision-
making process, such as routers or switches; other devices may making process, such as routers or switches; other devices may be
be passive such as a CSU/DSU. Regardless of constituent passive such as a CSU/DSU. Regardless of constituent components,
components, the system is treated as a singular entity to which the system is treated as a singular entity to which stimulus is
stimulus is offered and response measured. offered and response measured.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
See Also: See Also:
device under test (DUT) (3.1.1) device under test (DUT) (3.1.1)
3.2 Traffic orientation 3.2 Traffic orientation
This group of definitions applies to the traffic presented to the This group of definitions applies to the traffic presented to the
interfaces of a DUT/SUT and indicates whether the interfaces are interfaces of a DUT/SUT and indicates whether the interfaces are
receiving only, transmitting only, or both receiving and receiving only, transmitting only, or both receiving and
transmitting. transmitting.
3.2.1 Unidirectional traffic 3.2.1 Unidirectional traffic
Definition: Definition:
When all frames presented to the input interfaces of a DUT/SUT When all frames presented to the input interfaces of a DUT/SUT are
are addressed to output interfaces which do not themselves addressed to output interfaces which do not themselves receive any
receive any frames. frames.
Discussion: Discussion:
This definition conforms to the discussion in section 16 of RFC This definition conforms to the discussion in section 16 of RFC
1944 on multi-port testing which describes how unidirectional 1944 which describes how unidirectional traffic can be offered to
traffic can be offered to a DUT/SUT to measure throughput. a DUT/SUT to measure throughput. Unidirectional traffic is also
Unidirectional traffic is also appropriate for: appropriate for:
-the measurement of the minimum inter-frame gap -the measurement of the minimum inter-frame gap -the creation of
-the creation of many-to-one or one-to-many interface overload many-to-one or one-to-many interface overload -the detection of
-the detection of head of line blocking head of line blocking -the measurement of forwarding rates and
-the measurement of forwarding rates and throughput when throughput when congestion control mechanisms are active.
congestion control mechanisms are active.
When a tester offers unidirectional traffic to a DUT/SUT When a tester offers unidirectional traffic to a DUT/SUT reception
reception and transmission are handled by different interfaces and transmission are handled by different interfaces or sets of
or sets of interfaces of the DUT/SUT. All frames received from interfaces of the DUT/SUT. All frames received from the tester by
the tester by the DUT/SUT are transmitted back to the tester the DUT/SUT are transmitted back to the tester from interfaces
from interfaces which do not themselves receive any frames. which do not themselves receive any frames.
It is useful to distinguish traffic orientation and traffic It is useful to distinguish traffic orientation and traffic
distribution when considering traffic patterns used in device distribution when considering traffic patterns used in device
testing. Unidirectional traffic, for example, is traffic testing. Unidirectional traffic, for example, is traffic
orientated in a single direction between mutually exclusive orientated in a single direction between mutually exclusive sets
sets of source and destination interfaces of a DUT/SUT. Such of source and destination interfaces of a DUT/SUT. Such traffic,
traffic, however, can be distributed between interfaces in however, can be distributed between interfaces in different ways.
different ways. When traffic is sent to two or more When traffic is sent to two or more interfaces from an external
interfaces from an external source and then forwarded by the source and then forwarded by the DUT/SUT to a single output
DUT/SUT to a single output interface the traffic orientation is interface the traffic orientation is unidirectional and the
unidirectional and the traffic distribution between interfaces traffic distribution between interfaces is many-to-one. Traffic
is many-to-one. Traffic can also be sent to a single input can also be sent to a single input interface and forwarded by the
interface and forwarded by the DUT/SUT to two or more output DUT/SUT to two or more output interfaces to achieve a one-to-many
interfaces to achieve a one-to-many distribution of traffic. distribution of traffic.
Such traffic distributions can also be combined to test for Such traffic distributions can also be combined to test for head
head of line blocking or to measure forwarding rates and of line blocking or to measure forwarding rates and throughput
throughput when congestion control is active. when congestion control mechanisms are active.
When a DUT/SUT is equipped with interfaces running at different When a DUT/SUT is equipped with interfaces running at different
media rates the number of input interfaces required to load or media rates the number of input interfaces required to load or
overload an output interface or interfaces will vary. overload an output interface or interfaces will vary.
It should be noted that measurement of the minimum inter-frame It should be noted that measurement of the minimum inter-frame gap
gap serves to detect violations of the IEEE 802.3 standard. serves to detect violations of the IEEE 802.3 standard.
Issues: Issues:
half duplex / full duplex half duplex / full duplex
Measurement units: Measurement units:
n/a n/a
See Also: See Also:
bidirectional traffic (3.2.2) bidirectional traffic (3.2.2)
one-to-one mapped traffic (3.3.1) non-meshed traffic (3.3.1)
partially meshed traffic (3.3.2) partially meshed traffic (3.3.2)
fully meshed traffic (3.3.3) fully meshed traffic (3.3.3)
congestion control (3.7) congestion control (3.7)
head of line blocking (3.7.3) head of line blocking (3.7.3)
3.2.2 Bidirectional traffic 3.2.2 Bidirectional traffic
Definition: Definition:
Frames presented to a DUT/SUT such that each of the interfaces Frames presented to a DUT/SUT such that every receiving interface
of the DUT/SUT both receive and transmit. also transmits.
Discussion: Discussion:
This definition conforms to the discussions in sections 14 and This definition conforms to the discussion in section 14 of RFC
16 of RFC 1944 on bidirectional traffic and multi-port testing. 1944.
When a tester offers bidirectional traffic to a DUT/SUT all the When a tester offers bidirectional traffic to a DUT/SUT all the
interfaces which receive frames from the tester also transmit interfaces which receive frames from the tester also transmit
frames back to the tester. frames back to the tester.
Bidirectional traffic MUST be offered when measuring throughput Bidirectional traffic MUST be offered when measuring the
on full duplex interfaces of a switching device. throughput or forwarding rate of full duplex interfaces of a
switching device.
Issues: Issues:
truncated binary exponential back-off algorithm truncated binary exponential back-off algorithm
Measurement units: Measurement units:
n/a n/a
See Also: See Also:
unidirectional traffic (3.2.1) unidirectional traffic (3.2.1)
one-to-one mapped traffic (3.3.1) non-meshed traffic (3.3.1)
partially meshed traffic (3.3.2) partially meshed traffic (3.3.2)
fully meshed traffic (3.3.3) fully meshed traffic (3.3.3)
3.3 Traffic distribution 3.3 Traffic distribution
This group of definitions applies to the distribution of frames This group of definitions applies to the distribution of frames
forwarded by any DUT/SUT. forwarded by a DUT/SUT.
3.3.1 One-to-one mapped traffic 3.3.1 Non-meshed traffic
Definition: Definition:
Frames offered to a single input interface and addressed to a
single output interface of a DUT/SUT where input and output
interfaces are grouped in mutually exclusive pairs.
Discussion: Frames offered to a single input interface and addressed to a
single output interface of a DUT/SUT where input and output
interfaces are grouped in mutually exclusive pairs.
In the simplest instance of one-to-one mapped traffic Discussion:
distribution frames are forwarded between one source interface
and one destination interface of a DUT/SUT. One-to-one mapped
traffic distribution extends to multiple distinct pairs of
source and destination interfaces.
Measurement units: In the simplest instance of non-meshed traffic all frames are
offered to a single input interface and addressed to a single
output interface. The one-to-one mapping of input to output
interfaces required by non-meshed traffic can be extended to
multiple mutually exclusive pairs of input and output interfaces.
n/a Measurement units:
Issues: n/a
half duplex / full duplex Issues:
See Also: half duplex / full duplex
unidrectional traffic (3.2.1) See Also:
bidirectional traffic (3.2.2)
partially meshed traffic (3.3.2.)
fully meshed traffic (3.3.3)
burst (3.4.1)
3.3.2 Partially meshed traffic unidirectional traffic (3.2.1)
bidirectional traffic (3.2.2)
partially meshed traffic (3.3.2.)
fully meshed traffic (3.3.3)
burst (3.4.1)
Definition: 3.3.2 Partially meshed traffic
Frames offered to one or more input interfaces of a DUT/SUT and Definition:
addressed to one or more output interfaces where input and
output interfaces are mutually exclusive and mapped one-to-
many, many-to-one or many-to-many.
Discussion: Frames offered to one or more input interfaces of a DUT/SUT and
This definition follows from the discussions in sections 14 and addressed to one or more output interfaces where input and output
16 of RFC 1944 on bidirectional traffic and multi-port testing. interfaces are mutually exclusive and mapped one-to-many, many-
Partially meshed traffic allows for one-to-many, many-to-one or to-one or many-to-many.
many-to-many mappings of input to output interfaces and readily
extends to configurations with multiple switching devices
linked together over backbone connections.
When partially meshed traffic is distributed in a one-to-many Discussion:
or many-to-one mapping of receiving to transmitting interfaces
of a DUT/SUT traffic orientation will be unidirectional. When
traffic is partially meshed and distributed in a many-to-many
mapping of receiving to transmitting ports which are mutually
exclusive traffic orientation will be bidirectional.
Measurement units: This definition follows from the discussion in section 16 of RFC
n/a 1944 on multi-port testing. Partially meshed traffic allows for
one-to-many, many-to-one or many-to-many mappings of input to
output interfaces and readily extends to configurations with
multiple switching devices linked together over backbone
connections.
Issues: It should be noted that partially meshed traffic can load backbone
connections linking together two switching devices or systems more
than fully meshed traffic. When offered partially meshed traffic
devices or systems can be set up to forward all of the frames they
receive to the opposite side of the backbone connection whereas
fully meshed traffic requires at least some of the offered frames
to be forwarded locally, that is to the interfaces of the DUT/SUT
receiving them. Such frames will not traverse the backbone
connection.
half duplex / full duplex Measurement units:
See Also: n/a
unidirectional traffic (3.2.1) Issues:
bidirectional traffic (3.2.2)
one-to-one mapped traffic (3.3.1)
fully meshed traffic (3.3.3)
burst (3.4.1)
3.3.3 Fully meshed traffic half duplex / full duplex
Definition: See Also:
Frames switched simultaneously between all of a designated unidirectional traffic (3.2.1)
number of interfaces of a DUT/SUT such that each of the bidirectional traffic (3.2.2)
interfaces under test will both forward frames to and receive non-meshed traffic (3.3.1)
frames from all of the other interfaces under test. fully meshed traffic (3.3.3)
burst (3.4.1)
Discussion: 3.3.3 Fully meshed traffic
As with bidirectional multi-port traffic, meshed traffic Definition:
exercises both the transmission and reception sides of the
interfaces of a switching device. Since interfaces are not
divided into two groups every interface forwards frames to and
receives frames from every other interface. The total number
of individual input/output interface pairs when traffic is
meshed over n switched interfaces equals n x (n - 1). This
compares with n x (n / 2) such interface pairs in a
bidirectional multi-port test.
It should be noted that bidirectional multi-port traffic can Frames offered to a designated number of interfaces of a DUT/SUT
load backbone connections linking together two switching such that each one of the interfaces under test receives frames
devices more than fully meshed traffic. In a bidirectional addressed to all of the other interfaces under test.
multiport test each one of two devices or systems connected
over a backbone connection can be configured to forward the
totality of the frames they receive to the devices or systems
placed on the opposite side of the backbone connection. All
frames generated during such a test will traverse the backbone
connection. Fully meshed traffic requires at least some of the
frames received on the interfaces of each one of the devices or
systems under test to be forwarded locally, that is to the
interfaces of the receiving devices themselves. Such frames
will not traverse the backbone connection.
Bidirectional meshed traffic on half duplex interfaces is Discussion:
inherently bursty since interfaces must interrupt transmission
whenever they receive frames. This kind of bursty meshed
traffic is characteristic of real network traffic and can be
advantageously used to diagnose a DUT/SUT by exercising many of
its component parts simultaneously. Additional inspection may
be warranted to correlate the frame forwarding capacity of a
DUT/SUT when offered meshed traffic and the behavior of
individual elements such as input or output buffers,
buffer allocation mechanisms, aggregate switching capacity,
processing speed or medium access control.
The analysis of forwarding rate measurements presents a As with bidirectional partially meshed traffic, fully meshed
challenge when offering bidirectional or fully meshed traffic traffic requires each one the interfaces of a DUT/SUT to both
since the rate at which the tester can be observed to transmit receive and transmit frames. But since the interfaces are not
frames to the DUT/SUT may be smaller than the rate at which it divided into groups as with partially meshed traffic every
intends to transmit due to collisions on half duplex media or interface forwards frames to and receives frames from every other
the action of congestion control mechanisms. This makes it interface. The total number of individual input/output interface
important to take account of both the intended and offered pairs when traffic is fully meshed over n switched interfaces
loads defined in sections 3.5.1.and 3.5.2 below when reporting equals n x (n - 1). This compares with n x (n / 2) such interface
the results of such forwarding rate measurements. pairs when traffic is partially meshed.
When offering bursty meshed traffic to a DUT/SUT a number of Fully meshed traffic on half duplex interfaces is inherently
variables have to be considered. These include frame size, the bursty since interfaces must interrupt transmission whenever they
number of frames within bursts, the interval between bursts as receive frames. This kind of bursty meshed traffic is
well as the distribution of load between incoming and outgoing characteristic of real network traffic and can be advantageously
traffic. Terms related to bursts are defined in section 3.3 used to diagnose a DUT/SUT by exercising many of its component
below. parts simultaneously. Additional inspection may be warranted to
correlate the frame forwarding capacity of a DUT/SUT when offered
meshed traffic and the behavior of individual elements such as
input or output buffers, buffer allocation mechanisms, aggregate
switching capacity, processing speed or medium access control.
Measurement units: The analysis of forwarding rate measurements presents a challenge
when offering bidirectional or fully meshed traffic since the rate
at which the tester can be observed to transmit frames to the
DUT/SUT may be smaller than the rate at which it intends to
transmit due to collisions on half duplex media or the action of
congestion control mechanisms. This makes it important to take
account of both the intended and offered loads defined in sections
3.5.1.and 3.5.2 below when reporting the results of such
forwarding rate measurements.
n/a When offering bursty meshed traffic to a DUT/SUT a number of
variables have to be considered. These include frame size, the
number of frames within bursts, the interval between bursts as
well as the distribution of load between incoming and outgoing
traffic. Terms related to bursts are defined in section 3.4
below.
Issues: Measurement units:
half duplex / full duplex n/a
See Also: Issues:
unidirectional traffic (3.2.1) half duplex / full duplex
bidirectional traffic (3.2.2)
one-to-one mapped traffic (3.3.1)
partially meshed traffic (3.3.2)
burst (3.4.1)
intended load (3.5.1)
offered load (3.5.2)
3.4 Bursts See Also:
unidirectional traffic (3.2.1)
bidirectional traffic (3.2.2)
non-meshed traffic (3.3.1)
partially meshed traffic (3.3.2)
burst (3.4.1)
intended load (3.5.1)
offered load (3.5.2)
3.4 Bursts
This group of definitions applies to the intervals between frames or This group of definitions applies to the intervals between frames or
groups of frames offered to the DUT/SUT. groups of frames offered to the DUT/SUT.
3.4.1 Burst 3.4.1 Burst
Definition: Definition:
A sequence of frames transmitted with the minimum inter-frame A sequence of frames transmitted with the minimum legal inter-
gap allowed by the medium. frame gap.
Discussion: Discussion:
This definition follows from discussions in section 3.16 of RFC This definition follows from discussions in section 3.16 of RFC
1242 and section 21 of RFC 1944 which describes cases where it 1242 and section 21 of RFC 1944 which describes cases where it is
is useful to consider isolated frames as single frame bursts. useful to consider isolated frames as single frame bursts.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
See Also: See Also:
burst size (3.4.2) burst size (3.4.2)
inter-burst gap (IBG) (3.4.3) inter-burst gap (IBG) (3.4.3)
3.4.2 Burst size 3.4.2 Burst size
Definition: Definition:
The number of frames in a burst. The number of frames in a burst.
Discussion: Discussion:
Burst size can range from one to infinity. In unidirectional Burst size can range from one to infinity. In unidirectional
traffic as well as in bidirectional or meshed traffic on full traffic as well as in bidirectional or meshed traffic on full
duplex interfaces there is no theoretical limit to burst duplex interfaces there is no theoretical limit to burst length.
length. When traffic is bidirectional or meshed bursts on half When traffic is bidirectional or meshed bursts on half duplex
duplex media are finite since interfaces interrupt transmission media are finite since interfaces interrupt transmission
intermittently to receive frames. intermittently to receive frames.
On real networks burst size will normally increase with window On real networks burst size will normally increase with window
size. This makes it desirable to test devices with small as size. This makes it desirable to test devices with small as well
well as large burst sizes. as large burst sizes.
Measurement units: Measurement units:
number of N-octet frames number of N-octet frames
Issues: Issues:
See Also: See Also:
burst (3.4.1) burst (3.4.1)
inter-burst gap (IBG) (3.4.3) inter-burst gap (IBG) (3.4.3)
3.4.3 Inter-burst gap (IBG) 3.4.3 Inter-burst gap (IBG)
Definition: Definition:
The interval between two bursts. The interval between two bursts.
Discussion: Discussion:
This definition conforms to the discussion in section 20 of RFC This definition conforms to the discussion in section 20 of RFC
1944 on bursty traffic. 1944 on bursty traffic.
Bidirectional and meshed traffic are inherently bursty since Bidirectional and meshed traffic are inherently bursty since
interfaces share their time between receiving and transmitting interfaces share their time between receiving and transmitting
frames. External sources offering bursty traffic for a given frames. External sources offering bursty traffic for a given
frame size and burst size must adjust the inter-burst gap to frame size and burst size must adjust the inter-burst gap to
achieve a specified average rate of frame transmission. achieve a specified average rate of frame transmission.
Measurement units: Measurement units:
nanoseconds nanoseconds
microseconds microseconds
milliseconds milliseconds
seconds seconds
Issues: Issues:
See Also: See Also:
burst (3.4.1) burst (3.4.1)
burst size (3.4.2) burst size (3.4.2)
3.5 Loads 3.5 Loads
This group of definitions applies to the rates at which traffic is This group of definitions applies to the rates at which traffic is
offered to any DUT/SUT. offered to any DUT/SUT.
3.5.1 Intended load (Iload) 3.5.1 Intended load (Iload)
Definition:
The number of frames per second that an external source Definition:
attempts to transmit to a DUT/SUT for forwarding to a specified
output interface or interfaces.
Discussion: The number of frames per second that an external source attempts
to transmit to a DUT/SUT for forwarding to a specified output
interface or interfaces.
Collisions on CSMA/CD links or the action of congestion control Discussion:
mechanisms can effect the rate at which an external source of
traffic transmits frames to a DUT/SUT. This makes it useful to
distinguish the load that an external source attempts to apply
to a DUT/SUT and the load it is observed or measured to apply
In the case of Ethernet an external source of traffic MUST Collisions on CSMA/CD links or the action of congestion control
Implement the truncated binary exponential back-off algorithm mechanisms can effect the rate at which an external source of
to ensure that it is accessing the medium legally traffic transmits frames to a DUT/SUT. This makes it useful to
distinguish the load that an external source attempts to apply to
a DUT/SUT and the load it is observed or measured to apply.
Measurement units: In the case of Ethernet an external source of traffic MUST
implement the truncated binary exponential back-off algorithm to
ensure that it is accessing the medium legally
bits per second Measurement units:
N-octets per second
(N-octets per second / media_maximum-octets per second) x 100
Issues: bits per second
N-octets per second
(N-octets per second / media_maximum-octets per second) x 100
See Also: Issues:
burst (3.4.1) See Also:
inter-burst gap (3.4.3)
offered load (3.5.2)
3.5.2 Offered load (Oload) burst (3.4.1)
inter-burst gap (3.4.3)
offered load (3.5.2)
Definition: 3.5.2 Offered load (Oload)
The number of frames per second that an external source can be Definition:
observed or measured to transmit to a DUT/SUT for forwarding to
a specified output interface or interfaces.
Discussion: The number of frames per second that an external source can be
observed or measured to transmit to a DUT/SUT for forwarding to a
specified output interface or interfaces.
The load which an external device can be observed to apply to a Discussion:
DUT/SUT may be less than the intended load due to collisions on
half duplex media or the action of congestion control
mechanisms. This makes it important to distinguish intended
and offered load when analyzing the results of forwarding rate
measurements using bidirectional or fully meshed traffic
Frames which are not successfully transmitted by an external The load which an external device can be observed to apply to a
source of traffic to a DUT/SUT MUST NOT be counted as DUT/SUT may be less than the intended load due to collisions on
transmitted frames when measuring the forwarding rate of a half duplex media or the action of congestion control mechanisms.
DUT/SUT. This makes it important to distinguish intended and offered load
when analyzing the results of forwarding rate measurements using
bidirectional or fully meshed traffic.
The frame count on an interface of a DUT/SUT may exceed the Frames which are not successfully transmitted by an external
rate at which an external device offers frames due to the source of traffic to a DUT/SUT MUST NOT be counted as transmitted
presence of spanning tree BPDUs (Bridge Protocol Data Units) on frames when measuring forwarding rates.
802.1D-compliant switches or SNMP frames. Such frames should
be treated as modifiers as described in section 11 of RFC 1944
Measurement units: The frame count on an interface of a DUT/SUT may exceed the rate
at which an external device offers frames due to the presence of
spanning tree BPDUs (Bridge Protocol Data Units) on 802.1D-
compliant switches or SNMP frames. Such frames should be treated
as modifiers as described in section 11 of RFC 1944.
bits per second Offered load MUST be indicated when reporting the results of
N-octets per second forwarding rate measurements.
(N-octets per second / media_maximum-octets per second) x 100
Issues: Measurement units:
token ring bits per second
N-octets per second
(N-octets per second / media_maximum-octets per second) x 100
See Also: Issues:
bidirectional traffic (3.2.2) token ring
fully meshed traffic (3.3.3)
intended load (3.5.1)
forwarding rate (3.6.1)
3.5.3 Maximum offered load (MOL) See Also:
Definition: bidirectional traffic (3.2.2)
fully meshed traffic (3.3.3)
intended load (3.5.1)
forwarding rate (3.6.1)
The highest number of frames per second that an external source 3.5.3 Maximum offered load (MOL)
can transmit to a DUT/SUT for forwarding to a specified output
interface or interfaces.
Discussion: Definition:
The maximum load that an external device can apply to a DUT/SUT The highest number of frames per second that an external source
may not equal the maximum load allowed by the medium. This can transmit to a DUT/SUT for forwarding to a specified output
will be the case when an external source lacks the resources interface or interfaces.
to transmit frames at the minimum legal inter-frame gap or when
it has sufficient resources to transmit frames below the
minimum legal inter-frame gap. Moreover, maximum load may vary
with respect to parameters other than a medium's maximum
theoretical utilization. For example, on those media employing
tokens, maximum load may vary as a function of Token Rotation
Time, Token Holding Time, or the ability to chain multiple
frames to a single token. The maximum load that an external
device applies to a DUT/SUT MUST be specified when measuring
forwarding rates.
Measurement units: Discussion:
bits per second The maximum load that an external device can apply to a DUT/SUT
N-octets per second may not equal the maximum load allowed by the medium. This
(N-octets per second / media_maximum-octets per second) x 100 will be the case when an external source lacks the resources
to transmit frames at the minimum legal inter-frame gap or when
it has sufficient resources to transmit frames below the
minimum legal inter-frame gap. Moreover, maximum load may vary
with respect to parameters other than a medium's maximum
theoretical utilization. For example, on those media employing
tokens, maximum load may vary as a function of Token Rotation
Time, Token Holding Time, or the ability to chain multiple
frames to a single token. The maximum load that an external
device applies to a DUT/SUT MUST be specified when measuring
forwarding rates.
Issues: Measurement units:
See Also: bits per second
N-octets per second
(N-octets per second / media_maximum-octets per second) x 100
offered load (3.5.2) Issues:
3.5.4 Overloading See Also:
Definition: offered load (3.5.2)
Attempting to load a DUT/SUT in excess of the maximum rate of 3.5.4 Overloading
transmission allowed by the medium.
Discussion: Definition:
Overloading can serve to exercise buffers and buffer allocation Attempting to load a DUT/SUT in excess of the maximum rate of
algorithms as well as congestion control mechanisms. transmission allowed by the medium.
The number of input interfaces required to overload one or more Discussion:
output interfaces of a DUT/SUT will vary according to the media
rates of the interfaces involved.
An external source can also overload an interface by Overloading can serve to exercise buffers and buffer allocation
transmitting frames below the minimum inter-frame gap. A algorithms as well as congestion control mechanisms. The number
DUT/SUT MUST forward such frames at intervals equal to or above of input interfaces required to overload one or more output
the minimum gap specified in standards. interfaces of a DUT/SUT will vary according to the media rates of
the interfaces involved.
A DUT/SUT using congestion control techniques such as An external source can also overload an interface by transmitting
backpressure or forward pressure may exhibit no frame loss when frames below the minimum inter-frame gap. A DUT/SUT MUST forward
a tester attempts to overload one or more of its interfaces. such frames at intervals equal to or above the minimum gap
This should not be exploited to suggest that the DUT/SUT specified in standards.
supports rates of transmission in excess of the maximum rate
allowed by the medium since both techniques reduce the rate at
which the tester offers frames to prevent overloading.
Backpressure achieves this purpose by jamming the transmission
interfaces of the tester and forward pressure by hindering the
tester from gaining fair acces to the medium. Analysis of both
cases should take the distinction between intended load (3.5.1)
and offered load (3.5.2) into account.
Overloading can be achieved with unidirectional, bidirectional A DUT/SUT using congestion control techniques such as backpressure
and meshed traffic. or forward pressure may exhibit no frame loss when a tester
attempts to overload one or more of its interfaces. This should
not be exploited to suggest that the DUT/SUT supports rates of
transmission in excess of the maximum rate allowed by the medium
since both techniques reduce the rate at which the tester offers
frames to prevent overloading. Backpressure achieves this purpose
by jamming the transmission interfaces of the tester and forward
pressure by hindering the tester from gaining fair access to the
medium. Analysis of both cases should take the distinction
between intended load (3.5.1) and offered load (3.5.2) into
account.
Measurement units: Measurement units:
N-octets per second bits per second
(N-octets per second / media_maximum-octets per second) x 100N- N-octets per second
octet (N-octets per second / media_maximum-octets per second) x 100
frames per second
Issues: Issues:
See Also: See Also:
unidirectional traffic (3.2.1) unidirectional traffic (3.2.1)
intended load (3.5.1) intended load (3.5.1)
offered load (3.5.2) offered load (3.5.2)
forwarding rate (3.6.1) forwarding rate (3.6.1)
backpressure (3.7.1) backpressure (3.7.1)
forward pressure (3.7.2) forward pressure (3.7.2)
3.6 Forwarding rates 3.6 Forwarding rates
This group of definitions applies to the rates at which traffic is This group of definitions applies to the rates at which traffic is
forwarded by any DUT/SUT in response to a stimulus. forwarded by any DUT/SUT in response to a stimulus.
3.6.1 Forwarding rate (FR) 3.6.1 Forwarding rate (FR)
Definition: Definition:
The number of frames per second that a device can be observed The number of frames per second that a device can be observed to
to successfully transmit to the correct destination interface successfully transmit to the correct destination interface in
in response to a specified offered load. response to a specified offered load.
Discussion: Discussion:
Unlike throughput defined in section 3.17 of RFC 1242, Unlike throughput defined in section 3.17 of RFC 1242, forwarding
forwarding rate makes no explicit reference to frame loss. rate makes no explicit reference to frame loss. Forwarding rate
Forwarding rate refers to the number of frames per second refers to the number of frames per second observed on the output
observed on the output side of the interface under test an side of the interface under test and MUST be reported in relation
MUST be reported in relation to the offered load. Forwarding to the offered load. Forwarding rate can be measured with
rate can be measured with different traffic orientations and different traffic orientations and distributions.
distributions.
It should be noted that the forwarding rate of a DUT/SUT may be It should be noted that the forwarding rate of a DUT/SUT may be
sensitive to the action of congestion control mechanisms. sensitive to the action of congestion control mechanisms.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
offered load (3.5.2) offered load (3.5.2)
forwarding rate at maximum offered load (3.6.2) forwarding rate at maximum offered load (3.6.2)
maximum forwarding rate (3.6.3) maximum forwarding rate (3.6.3)
3.6.2 Forwarding rate at maximum offered load (FRMOL) 3.6.2 Forwarding rate at maximum offered load (FRMOL)
Definition: Definition:
The number of frames per second that a device can be observed The number of frames per second that a device can be observed to
To successfully transmit to the correct destination interface successfully transmit to the correct destination interface in
in response to the maximum offered load. response to the maximum offered load.
Discussion: Discussion:
Forwarding rate at maximum offered load may be less than the Forwarding rate at maximum offered load may be less than the
maximum rate at which a device can be observed to successfully maximum rate at which a device can be observed to successfully
forward traffic. forward traffic. This will be the case when the ability of a
device to forward frames degenerates when offered traffic at
maximum load.
This will be the case when the ability of a device to forward Maximum offered load MUST be cited when reporting forwarding rate
frames degenerates when offered traffic at maximum load. at maximum offered load.
Maximum offered load MUST be cited when reporting forwarding
rate at maximum offered load.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
maximum offered load (3.5.3) maximum offered load (3.5.3)
forwarding rate (3.6.1) forwarding rate (3.6.1)
maximum forwarding rate (3.6.3) maximum forwarding rate (3.6.3)
3.6.3 Maximum forwarding rate (MFR) 3.6.3 Maximum forwarding rate (MFR)
Definition: Definition:
The highest forwarding rate of a DUT/SUT taken from an The highest forwarding rate of a DUT/SUT taken from an iterative
iterative set of forwarding rate measurements. set of forwarding rate measurements.
Discussion: Discussion:
The forwarding rate of a device may degenerate before maximum The forwarding rate of a device may degenerate before maximum load
load is reached. The load applied to a device must be cited is reached. The load applied to a device must be cited when
when reporting maximum forwarding rate. reporting maximum forwarding rate.
The following example illustrates how the terms relative to The following example illustrates how the terms relative to
loading and forwarding rates are meant to be used. In loading and forwarding rates are meant to be used. In particular
particular it shows how the distinction between forwarding rate it shows how the distinction between forwarding rate at maximum
at maximum offered load (FRMOL) and maximum forwarding rate offered load (FRMOL) and maximum forwarding rate (MFR) can be used
(MFR)can be used to characterize a DUT/SUT. to characterize a DUT/SUT.
(A) (B) Column A - Oload (A) (B)
Test Device DUT/SUT Column B - FR Test Device DUT/SUT
Offered Rate Forwarding Rate Offered Load Forwarding Rate
------------ --------------- ------------ ---------------
1. 14,880 fps 7,400 fps Row 1, Col A - MOL (1) 14,880 fps - MOL 7,400 fps - FRMOL
2. 13,880 fps 8,472 fps Row 1, Col B - FRMOL (2) 13,880 fps 8,472 fps
3. 12,880 fps 12,880 fps Row 3, Col B - MFR (3) 12,880 fps 12,880 fps - MFR
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
offered load (3.5.2) offered load (3.5.2)
forwarding rates (3.6.1) forwarding rates (3.6.1)
forwarding rate at maximum load (3.6.2) forwarding rate at maximum load (3.6.2)
3.7 Congestion control 3.7 Congestion control
This group of definitions applies to the behavior of a DUT/SUT when This group of definitions applies to the behavior of a DUT/SUT when
congestion or contention is present. congestion or contention is present.
3.7.1 Backpressure 3.7.1 Backpressure
Definition: Definition:
Any technique used by a DUT/SUT to attempt to avoid frame loss Any technique used by a DUT/SUT to attempt to avoid frame loss by
by impeding external sources of traffic from transmitting impeding external sources of traffic from transmitting frames to
frames to congested interfaces. congested interfaces.
Discussion: Discussion:
Some switches send jam signals, for example preamble bits, back Some switches send jam signals, for example preamble bits, back to
to traffic sources when their transmit and/or receive buffers traffic sources when their transmit and/or receive buffers start
start to overfill. Switches implementing full duplex Ethernet to overfill. Switches implementing full duplex Ethernet links may
links may use IEEE 802.3x Flow Control for the same purpose. use IEEE 802.3x Flow Control for the same purpose. Such devices
Such devices may incur no frame loss when external sources may incur no frame loss when external sources attempt to offer
attempt to offer traffic to congested or overloaded interfaces. traffic to congested or overloaded interfaces.
It should be noted that jamming and other flow control methods It should be noted that jamming and other flow control methods may
may slow all traffic transmitted to congested input interfaces slow all traffic transmitted to congested input interfaces
including traffic intended for uncongested output interfaces. including traffic intended for uncongested output interfaces.
A DUT/SUT applying backpressure may exhibit no frame loss when A DUT/SUT applying backpressure may exhibit no frame loss when a
a tester attempts to overload one or more of its interfaces. tester attempts to overload one or more of its interfaces. This
This should not be interpreted to suggest that the interfaces should not be interpreted to suggest that the interfaces of the
of the DUT/SUT support forwarding rates above the maximum rate DUT/SUT support forwarding rates above the maximum rate allowed by
allowed by the medium. In these cases overloading is only the medium. In these cases overloading is only apparent since
apparent since through the application of backpressure the through the application of backpressure the DUT/SUT avoids
DUT/SUT avoids overloading by reducing the rate at which the overloading by reducing the rate at which the tester can offer
tester can offer frames. frames.
Measurement units: Measurement units:
frame loss on congested interface or interfaces frame loss on congested interface or interfaces N-octet frames per
N--octet frames per second between the interface applying second between the interface applying backpressure and an
backpressure and an uncongested destination interface uncongested destination interface
Issues: Issues:
jamming not explicitly described in standards jamming not explicitly described in standards
See Also: See Also:
intended load (3.5.1) intended load (3.5.1)
offered load (3.5.2) offered load (3.5.2)
overloading (3.5.4) overloading (3.5.4)
forwarding rate (3.6.1) forwarding rate (3.6.1)
forward pressure (3.7.2) forward pressure (3.7.2)
3.7.2 Forward pressure 3.7.2 Forward pressure
Definition: Definition:
Methods which depart from or otherwise violate a defined Methods which depart from or otherwise violate a defined
standardized protocol in an attempt to increase the forwarding standardized protocol in an attempt to increase the forwarding
performance of a DUT/SUT. performance of a DUT/SUT.
Discussion: Discussion:
A DUT/SUT may be found to inhibit or abort back-off algorithms A DUT/SUT may be found to inhibit or abort back-off algorithms in
in order to force access to the medium when contention occurs. order to force access to the medium when contention occurs. It
It should be noted that the back-off algorithm should be fair should be noted that the back-off algorithm should be fair whether
whether the DUT/SUT is in a congested or an uncongested state. the DUT/SUT is in a congested or an uncongested state.
Transmission below the minimum inter-frame gap or the disregard Transmission below the minimum inter-frame gap or the disregard of
of flow control primitives fall into this category. flow control primitives fall into this category.
A DUT/SUT applying forward pressure may eliminate all or most A DUT/SUT applying forward pressure may eliminate all or most
frame loss when a tester attempts to overload one or more of frame loss when a tester attempts to overload one or more of its
its interfaces. This should not be interpreted to suggest that interfaces. This should not be interpreted to suggest that the
the interfaces of the DUT/SUT can sustain forwarding rates interfaces of the DUT/SUT can sustain forwarding rates above the
above the maximum rate allowed by the medium. Overloading in maximum rate allowed by the medium. Overloading in such cases is
such cases is only apparent since the application of forward only apparent since the application of forward pressure by the
pressure by the DUT/SUT enables interfaces to relieve saturated DUT/SUT enables interfaces to relieve saturated output queues by
output queues by forcing access to the medium and concomitantly forcing access to the medium and concomitantly inhibiting the
inhibiting the tester from transmitting frames. tester from transmitting frames.
Measurement units: Measurement units:
intervals between frames in microseconds intervals between frames in microseconds
intervals in microseconds between transmission retries during intervals in microseconds between transmission retries during
16 successive collisions. 16 successive collisions.
Issues: Issues:
truncated binary exponential back-off algorithm truncated binary exponential back-off algorithm
See Also: See Also:
intended load (3.5.1) intended load (3.5.1)
offered load (3.5.2) offered load (3.5.2)
overloading (3.5.4) overloading (3.5.4)
forwarding rate (3.6.1) forwarding rate (3.6.1)
backpressure (3.7.1) backpressure (3.7.1)
3.7.3 Head of line blocking 3.7.3 Head of line blocking
Definition: Definition:
Frame loss or added delay observed on an uncongested output Frame loss or added delay observed on an uncongested output
interface whenever frames are received from an input interface interface whenever frames are received from an input interface
which is also attempting to forward frames to a congested which is also attempting to forward frames to a congested output
output interface. interface.
Discussion: Discussion:
It is important to verify that a switch does not slow It is important to verify that a switch does not slow transmission
transmission or drop frames on interfaces which are not or drop frames on interfaces which are not congested whenever
congested whenever overloading on one of its other interfaces overloading on one of its other interfaces occurs.
occurs.
Measurement units: Measurement units:
frame loss recorded on an uncongested interface when receiving forwarding rate and frame loss recorded on an uncongested
frames from an interface which is also forwarding frames to a interface when receiving frames from an interface which is also
congested interface. forwarding frames to a congested interface.
Issues: Issues:
input buffers input buffers
See Also: See Also:
unidirectional traffic (3.2.1) unidirectional traffic (3.2.1)
3.8 Address handling 3.8 Address handling
This group of definitions applies to the process of address This group of definitions applies to the address resolution process
resolution which enables a DUT/SUT to forward frames to the correct enabling a DUT/SUT to forward frames to their correct destinations.
destination.
3.8.1 Address caching capacity 3.8.1 Address caching capacity
Definition: Definition:
The number of MAC addresses per n interfaces, per module or per The number of MAC addresses per n interfaces, per module or per
device that a DUT/SUT can cache and successfully forward frames device that a DUT/SUT can cache and successfully forward frames to
to without flooding or dropping frames. without flooding or dropping frames.
Discussion: Discussion:
Users building networks will want to know how many nodes they Users building networks will want to know how many nodes they can
can connect to a DUT/SUT. This makes it necessary to verify connect to a switch. This makes it necessary to verify the number
the number of MAC addresses that can be assigned per n of MAC addresses that can be assigned per n interfaces, per module
interfaces, per module and per chassis before a DUT/SUT begins and per chassis before a DUT/SUT begins flooding frames.
flooding frames.
Measurement units: Measurement units:
number of MAC addresses per n interfaces, per module and/or per number of MAC addresses per n interfaces, modules, or chassis
chassis
Issues: Issues:
See Also: See Also:
Address learning rate (3.8.2) address learning rate (3.8.2)
3.8.2 Address learning rate 3.8.2 Address learning rate
Definition: Definition:
The maximum rate at which a switch can learn new MAC addresses The maximum rate at which a switch can learn new MAC addresses
Before starting to flood or drop frames. without flooding or dropping frames.
Discussion: Discussion:
Users may want to know how long it takes a switch to build its Users may want to know how long it takes a switch to build its
address tables. This information is useful to have when address tables. This information is useful to have when
considering how long it takes a network to come up when many considering how long it takes a network to come up when many users
users log on in the morning or after a network crash. log on in the morning or after a network crash.
Measurement units: Measurement units:
frames per second with each successive frame sent to the switch frames with different source addresses per second
containing a different source address.
Issues: Issues:
See Also: See Also:
address caching capacity (3.8.1) address caching capacity (3.8.1)
3.8.3 Flood count 3.8.3 Flood count
Definition: Definition:
Frames forwarded to interfaces which do not correspond to the Frames forwarded to interfaces which do not correspond to the
destination MAC address information when traffic is offered to destination MAC address information when traffic is offered to a
a DUT/SUT for forwarding. DUT/SUT for forwarding.
Discussion: Discussion:
When recording throughput statistics it is important to check When recording throughput statistics it is important to check that
that frames have been forwarded to their proper destinations. frames have been forwarded to their proper destinations. Flooded
Flooded frames MUST NOT be counted as received frames. Both frames MUST NOT be counted as received frames. Both known and
known and unknown unicast frames can be flooded. unknown unicast frames can be flooded.
Measurement units: Measurement units:
N-octet valid frames N-octet valid frames
Issues: Issues:
spanning tree BPDUs. spanning tree BPDUs.
See Also: See Also:
address caching capacity (3.8.1) address caching capacity (3.8.1)
3.9 Errored frame filtering 3.9 Errored frame filtering
This group of definitions applies to frames with errors which a This group of definitions applies to frames with errors which a
DUT/SUT may filter. DUT/SUT may filter.
3.9.1 Errored frames 3.9.1 Errored frames
Definition: Definition:
Frames which are over-sized, under-sized, misaligned or with an Frames which are over-sized, under-sized, misaligned or with an
errored Frame Check Sequence. errored Frame Check Sequence.
Discussion: Discussion:
Switches, unlike IEEE 802.1d compliant bridges, do not Switches, unlike IEEE 802.1d compliant bridges, do not necessarily
necessarily filter all types of illegal frames. Some switches, filter all types of illegal frames. Some switches, for example,
for example, which do not store frames before forwarding them which do not store frames before forwarding them to their
to their destination interfaces may not filter over-sized destination interfaces may not filter over-sized frames (jabbers)
frames (jabbers) or verify the validity of the Frame Check or verify the validity of the Frame Check Sequence field. Other
Sequence field. Other illegal frames are under-sized frames illegal frames are under-sized frames (runts) and misaligned
(runts) and misaligned frames. frames.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
See Also: See Also:
3.10 Broadcasts 3.10 Broadcasts
This group of definitions applies to MAC layer and network layer This group of definitions applies to MAC layer and network layer
broadcast frames. broadcast frames.
3.10.1 Broadcast forwarding rate 3.10.1 Broadcast forwarding rate
Definition: Definition:
The number of broadcast frames per second that a DUT/SUT can be The number of broadcast frames per second that a DUT/SUT can be
observed to deliver to all interfaces located within a observed to deliver to all interfaces located within a broadcast
broadcast domain in response to a specified offered load of domain in response to a specified offered load of frames directed
frames directed to the broadcast MAC address. to the broadcast MAC address.
Discussion: Discussion:
There is no standard forwarding mechanism used by switches to There is no standard forwarding mechanism used by switches to
forward broadcast frames. It is useful to determine the forward broadcast frames. It is useful to determine the broadcast
broadcast forwarding rate for frames switched between forwarding rate for frames switched between interfaces on the same
interfaces on the same card, interfaces on different cards in card, interfaces on different cards in the same chassis and
the same chassis and interfaces on different chassis linked interfaces on different chassis linked together over backbone
together over backbone connections. The terms maximum connections. The terms maximum broadcast forwarding rate and
broadcast forwarding rate and broadcast forwarding rate at broadcast forwarding rate at maximum load follow directly from the
maximum load follow directly from the terms already defined for terms already defined for forwarding rate measurements in section
forwarding rate measurements in section 3.6 above. 3.6 above.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
forwarding rate at maximum load (3.6.2) forwarding rate at maximum load (3.6.2)
maximum forwarding rate (3.6.3) maximum forwarding rate (3.6.3)
broadcast latency (3.10.2) broadcast latency (3.10.2)
3.10.2 Broadcast latency 3.10.2 Broadcast latency
Definition: Definition:
The time required by a DUT/SUT to forward a broadcast frame to The time required by a DUT/SUT to forward a broadcast frame to
each interface located within a broadcast domain. each interface located within a broadcast domain.
Discussion: Discussion:
Since there is no standard way for switches to process Since there is no standard way for switches to process
broadcast frames, broadcast latency may not be the same on all broadcast frames, broadcast latency may not be the same on all
receiving interfaces of a switching device. The latency receiving interfaces of a switching device. The latency
measurements SHOULD be bit oriented as described in 3.8 of measurements SHOULD be bit oriented as described in section 3.8
RFC 1242. It is useful to determine broadcast latency for of RFC 1242. It is useful to determine broadcast latency for
frames forwarded between interfaces on the same card, frames forwarded between interfaces on the same card, on
interfaces on different cards in the same chassis and different cards in the same chassis and on different chassis
interfaces on different chassis linked together over backbone linked over backbone connections.
connections.
Measurement units: Measurement units:
nanoseconds nanoseconds
microseconds microseconds
milliseconds milliseconds
seconds seconds
Issues: Issues:
See Also: See Also:
broadcast forwarding rate (3.10.1) broadcast forwarding rate (3.10.1)
4. Security Considerations 4. Security Considerations
Documents of this type do not directly effect the security of the Documents of this type do not directly effect the security of the
Internet or of corporate networks as long as benchmarking is not Internet or of corporate networks as long as benchmarking is not
performed on devices or systems connected to operating networks. performed on devices or systems connected to operating networks.
The document points out that switching devices may violate the The document points out that switching devices may violate the IEEE
IEEE 802.3 standard by transmitting frames below the minimum 802.3 standard by transmitting frames below the minimum interframe
interframe gap or unfairly accessing the medium by inhibiting the gap or unfairly accessing the medium by inhibiting the backoff
backoff algorithm. Although such violations do not directly algorithm. Although such violations do not directly engender
engender breaches in security, they may perturb the normal breaches in security, they may perturb the normal functioning of
functioning of other interworking devices by obstructing their other interworking devices by obstructing their access to the medium.
access to the medium. Their use on the Internet or on corporate Their use on the Internet or on corporate networks should be
networks should be discouraged. discouraged.
5. References: 5. References
1. RFC 1242 "Benchmarking Terminology for Network Interconnect [1] Bradner, S., "Benchmarking Terminology for Network
Devices" Interconnection Devices", RFC 1242, July 1991.
2. RFC 1944 "Benchmarking Methodology for Network Interconnect
Devices"
6. Acknowledgments [2] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 1944, May 1996.
A special thanks goes to the IETF BenchMarking Methodology 6. Acknowledgments
WorkGroup for the many suggestions it collectively made to help
complete this RFC. Kevin Dubray (Bay Networks), Jean-Christophe
Bestaux (ENL), Ajay Shah (WG), Henry Hamon (Netcom Systems), Stan
Kopek (3Com) and Doug Ruby (Prominet) provided valuable input at
various stages of this project.
7. Author's Address The Benchmarking Methodology Working Group of the IETF and
particularly Kevin Dubray (Bay Networks) are to be thanked for the
many suggestions they collectively made to help complete this
document. Ajay Shah (WG), Jean-Christophe Bestaux (ENL), Henry Hamon
(Netcom Systems), Stan Kopek (Digital) and Doug Ruby (Prominet) all
provided valuable input at various stages of this project.
Robert Mandeville Special thanks go to Scott Bradner for his seminal work in the field
European Network Laboratories (ENL) of benchmarking and his many encouraging remarks.
33, Boulevard Henri IV
75004 Paris
France
phone: + 33 1 39 44 12 05 7. Author's Address
mobile phone + 33 6 07 47 67 10
fax: + 33 1 39 44 12 06
email: bob.mandeville@eunet.fr Robert Mandeville
European Network Laboratories (ENL)
2, rue Helene Boucher
78286 Guyancourt Cedex
France
Phone: + 33 1 39 44 12 05
Mobile Phone + 33 6 07 47 67 10
Fax: + 33 1 39 44 12 06
EMail: bob.mandeville@eunet.fr
8. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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