draft-ietf-bmwg-lanswitch-04.txt   draft-ietf-bmwg-lanswitch-05.txt 
Network Working Group R. Mandeville Network Working Group R. Mandeville
INTERNET-DRAFT European Network Laboratories INTERNET-DRAFT European Network Laboratories
Expiration Date: September 1997 March 1997 Expires in six months July 1997
Benchmarking Terminology for LAN Switching Devices Benchmarking Terminology for LAN Switching Devices
< draft-ietf-bmwg-lanswitch-04.txt > <draft-ietf-bmwg-lanswitch-05.txt>
Status of this Document Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas, documents of the Internet Engineering Task Force (IETF), its
and its working groups. Note that other groups may also distribute areas, and its working groups. Note that other groups may also
working documents as Internet-Drafts. distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet- Drafts as documents at any time. It is inappropriate to use Internet-
reference material or to cite them other than as ``work in progress.'' Drafts as reference material or to cite them other than as
"work in progress."
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).
Distribution of this document is unlimited. Please send comments to
bmwg@harvard.edu or to the editor.
Abstract
The purpose of this draft is to define and discuss benchmarking
terminology for local area switching devices. It is meant to extend the
terminology already defined for network interconnect devices in
RFCs 1242 and 1944 by the Benchmarking Methodology Working
Group (BMWG) of the Internet Engineering Task Force (IETF) and
prepare the way for a discussion on benchmarking methodology for
local area switches.
LAN switches are one of the principal sources of new bandwidth in
the local area. The multiplicity of products brought to market makes
it desirable to define a set of terms to be used when evaluating the
performance characteristics of local area switching devices. Well-
defined terminology will help in providing the user community with
complete, reliable and comparable data on LAN switches.
1. Introduction
The purpose of this draft is to discuss and define terminology for the
benchmarking of local area network switches. Although it might be
found useful to apply some of the terms defined here to a broader
range of network interconnect devices, this draft primarily deals with
devices which switch frames at the Medium Access Control (MAC)
layer. It defines terms in relation to forwarding performance, latency,
address handling and filtering.
2. Term definitions To view the entire list of current Internet-Drafts, please check
the "1id-abstracts.txt" listing contained in the Internet-Drafts
Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net
(Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East
Coast), or ftp.isi.edu (US West Coast).
RFC 1242 "Benchmarking Terminology for Network Interconnect This memo provides information for the Internet community. This memo
Devices" defines many of the terms that are used in this document. does not specify an Internet standard of any kind. Distribution of
The terminology document should be consulted before attempting to this memo is unlimited.
make use of this document. RFC 1944 "Benchmarking Methodology
for Network Interconnect Devices" defines a number of test
procedures which are directly applicable to switches. Since it
discusses a number of terms relevant to benchmarking switches it
should also be consulted.
A number of new terms applicable to benchmarking switches are
defined below using the format for definitions set out in Section 2 of
RFC 1242. RFCs 1242 and 1944 already contain discussions of
some of these terms. The new terms are defined in groups.
2. 1. Reminder of RFC 1242 definition format Table of Contents
Term to be defined. (e.g., Latency) 1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Existing definitions. . . . . . . . . . . . . . . . . . . . . . . . 2
3. Term definitions. . . . . . . . . . . . . . . . . . . . . . . . . . 3
Definition: 3.1 Devices .. . . . . . . . . . . . . . . . . . . . . . . . . . 3
The specific definition for the term. 3.1.1 Device under test (DUT) . . . . . . . . . . . . . . . . 3
3.1.2 System under test (SUT). . . . . . . . . . . . . . . . 3
Discussion: 3.2 Traffic orientation. . . . . . . . . . . . . . . . . . . . . 3
A brief discussion about the term, its application 3.2.1 Unidirectional traffic. . . . . . . . . . . . . . . . . 4
and any restrictions on measurement procedures. 3.2.2 Bidirectional traffic . . . . . . . . . . . . . . . . . 5
Measurement units: 3.3 Traffic distribution . . . . . . . . . . . . . . . . . . . . 5
The units used to report measurements of this 3.3.1 One-to-one mapped traffic. .. . . . . . . . . . . . . . 5
term, if applicable. 3.3.2 Partially meshed traffic. . . . . . . . . . . . . . . . 6
3.3.3 Fully meshed traffic. . . . . . . . . . . . . . . . . . 6
Issues: 3.4 Bursts . . . . . . . . . . . . . . . . . . . . . . . . . . 8
List of issues or conditions that effect this term. 3.4.1 Burst . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4.2 Burst size. . . . . . . . . . . . . . . . . . . . . . . 8
3.4.3 Inter-burst gap (IBG) . . . . . . . . . . . . . . . . . 9
See Also: 3.5 Loads. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
List of other terms that are relevant to the discussion 3.5.1 Intended load (Iload) . . . . . . . . . . . . . . . . . 9
of this term. 3.5.2 Offered load (Oload) . . . . . . . . . . . . . . . . . 10
3.5.3 Maximum offered load (MOL) . . . . . . . . . . . . . . 10
3.5.4 Overloading. . . . . . . . . . . . . . . . . . . . . . 11
3. Index of terms defined 3.6 Forwarding rates. . . . . . . . . . . . . . . . . . . . . . 12
3.6.1 Forwarding rate (FR) . . . . . . . . . . . . . . . . . 12
3.6.2 Forwarding rate at maximum offered load (FRMOL). . . . 12
3.6.3 Maximum forwarding rate (MFR). . . . . . . . . . . . . 13
3.7 Congestion control. . . . . . . . . . . . . . . . . . . . . 14
3.7.1 Backpressure . . . . . . . . . . . . . . . . . . . . . 14
3.7.2 Forward pressure . . . . . . . . . . . . . . . . . . . 14
3.7.3 Head of line blocking. . . . . . . . . . . . . . . . . 15
3.8 Address handling. . . . . . . . . . . . . . . . . . . . . . 15
3.8.1 Address caching capacity . . . . . . . . . . . . . . . 15
3.8.2 Address learning rate. . . . . . . . . . . . . . . . . 16
3.8.3 Flood count. . . . . . . . . . . . . . . . . . . . . . 16
3.1 Devices 3.9 Errored frame filtering . . . . . . . . . . . . . . . . . . 17
3.1.1 Device under test (DUT) 3.9.1 Errored frames . . . . . . . . . . . . . . . . . . . . 17
3.1.2 System under test (SUT)
3.2 Traffic patterns 3.10 Broadcasts . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.1 Unidirectional traffic 3.10.1 Broadcast forwarding rate at maximum load . . . . . . 17
3.2.2 Bidirectional traffic 3.10.2 Broadcast latency . . . . . . . . . . . . . . . . . . 18
3.2.3 Partially meshed traffic
3.2.4 Fully meshed traffic
3.3 Bursts 4. Security Considerations. . . . . . . . . . . . . . . . . . . . . . 18
3.3.1 Burst 5. References. . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.3.2 Burst size 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.3.3 Inter-burst gap (IBG) 7. Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.4 Loads 1. Introduction
3.4.1 Intended load
3.4.2 Offered load
3.4.3 Maximum offered load
3.4.4 Overloading
3.5 Forwarding rates This document is intended to provide terminology for
3.5.1 Forwarding rate at maximum load the benchmarking of local area network (LAN) switching devices. It
3.5.2 Maximum forwarding rate extends the terminology already defined for benchmarking network
interconnect devices in RFCs 1242 and 1944 to switching devices.
Although it might be found useful to apply some of the terms defined
here to a broader range of network interconnect devices, this document
primarily deals with devices which switch frames at the Medium Access
Control (MAC) layer. It defines terms in relation to the traffic put to
use when benchmarking switching devices, forwarding performance,
latency, address handling and filtering.
3.6 Congestion control 2. Existing definitions
3.6.1 Backpressure
3.6.2 Forward pressure
3.6.3 Head of line blocking
3.7 Address handling RFC 1242 "Benchmarking Terminology for Network Interconnect Devices"
3.7.1 Address caching capacity should be consulted before attempting to make use of this document. RFC
3.7.2 Address learning rate 1944 "Benchmarking Methodology for Network Interconnect Devices"
3.7.3 Flood count contains discussions of a number of terms relevant to the benchmarking
of switching devices and should also be consulted.
3.8 Errored frame filtering For the sake of clarity and continuity this RFC adopts the template for
3.8.1 Errored frames definitions set out in Section 2 of RFC 1242. Definitions are indexed
and grouped together in sections for ease of reference.
3.9 Broadcasts 3. Term definitions
3.9.1 Broadcast forwarding rate at maximum load
3.9.2 Broadcast latency
3.1 Devices 3.1 Devices
This group applies to all types of networking devcies. This group of definitions applies to all types of networking devices.
3.1.1 Device under test (DUT) 3.1.1 Device under test (DUT)
Definition: Definition:
The network forwarding device to which stimuli is offered and The network forwarding device to which stimulus is offered and response
response measured. measured.
Discussion: Discussion:
A single stand-alone or modular unit generally equipped with its own A single stand-alone or modular unit generally equipped with its own
power supply. power supply.
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 stimuli is offered as a The collective set of network devices to which stimulus is offered as a
single entity and response measured. 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.
devices. Some devices may be active in the forwarding decision- Some devices may be active in the forwarding decision-making process,
making process, such as routers or switches; other devices may be such as routers or switches; other devices may be passive such as a
passive such as CSU/DSUs. Regardless of constituent components, CSU/DSU. Regardless of constituent components, the system is treated as
the system is treated as a singular entity to which stimuli is offered a singular entity to which stimulus is offered and response measured.
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 patterns 3.2 Traffic orientation
This group applies to the distribution of frames forwarded by any
DUT/SUT. This group of definitions applies to the traffic presented to the
interfaces of a DUT/SUT and indicates whether the interfaces are
receiving only, transmitting only, or both receiving and transmitting.
3.2.1 Unidirectional traffic 3.2.1 Unidirectional traffic
Definition: Definition:
Single or multiple streams of frames forwarded in one direction only Frames presented to a DUT/SUT such that the receiving and transmitting
from a set of input ports to a set of output ports. interfaces are mutually exclusive.
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
1944 on multi-port testing which describes how unidirectional traffic multi-port testing which describes how unidirectional traffic can be
can be offered to ports of a device to measure throughput. offered to 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 many-to-one or one-to-many port overload -the creation of many-to-one or one-to-many interface overload
- the detection of head of line blocking - the detection of head of line blocking
- the measurement of throughput when congestion control -the measurement of forwarding rates and throughput when congestion
mechanisms are active control mechanisms are active.
When considering traffic patterns it is useful to distinguish traffic
orientation and traffic distribution. In the case of unidirectional
traffic, for example, traffic is orientated in a single direction
between mutually exclusive sets of source and destination interfaces
of a DUT/SUT. Such traffic, however, can be distributed between
interfaces in different ways. When traffic is sent to two or more
interfaces from an external source and forwarded by the DUT/SUT to
a single output interface traffic orientation is unidirectional and
traffic distribution between interfaces is many-to-one. Traffic can
also be sent to a single input interface and forwarded by the DUT/SUT
to two or more output interfaces to achieve a one-to-many distribution
of traffic between interfaces.
Such traffic distributions can also be combined to test for head of
line blocking or to measure forwarding rates and throughput when
congestion control is active.
When a DUT/SUT is equipped with interfaces running at different media
rates the number of input interfaces required to load or overload an
output interface or interfaces will vary.
Unidirectional traffic can be used to load the ports of a DUT/SUT in
different ways. For example unidirectional traffic can be sent to two
or more input ports from an external source and forwarded by the
DUT/SUT to a single output port (n-to-1) or such traffic can be sent
to a single input port and forwarded by the DUT/SUT to two or more
output ports (1-to-n). Such patterns can be combined to test for head
of line blocking or to measure throughput when congestion control
mechanisms are active.
When a DUT/SUT is equipped with ports running at different media
rates the number of input streams required to load or overload an
output port or ports will vary.
It should be noted that measurement of the minimum inter-frame gap It should be noted that measurement of the minimum inter-frame 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)
partially meshed traffic (3.2.3) one-to-one mapped traffic (3.3.1)
fully meshed traffic (3.2.4) partially meshed traffic (3.3.2)
fully meshed traffic (3.3.3)
3.2.2 Bidirectional traffic 3.2.2 Bidirectional traffic
Definition: Definition:
Two or more streams of frames forwarded in opposite directions Frames presented to a DUT/SUT such that the interfaces of the DUT/SUT both
between two or more ports of a DUT/SUT. receive and transmit.
Discussion: Discussion:
This definition conforms to the discussions in sections 14 and 16 of This definition conforms to the discussions in sections 14 and 16 of
RFC 1944 on bidirectional traffic and multi-port testing. RFC 1944 on bidirectional traffic and multi-port testing. Bidirectional
Bidirectional traffic MUST be offered when measuring throughput traffic MUST be offered when measuring throughput on full duplex
on full duplex ports of a switching device. 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)
partially meshed traffic (3.2.3) one-to-one mapped traffic (3.3.1)
fully meshed traffic (3.2.4) partially meshed traffic (3.3.2)
fully meshed traffic (3.3.3)
3.2.3 Partially meshed traffic 3.3 Traffic distribution
This group of definitions applies to the distribution of frames
forwarded by any DUT/SUT.
3.3.1 One-to-one mapped traffic
Definition: Definition:
Streams of frames forwarded between a set of input ports and a set of Frames offered to a single input interface and destined to a single
output ports of a DUT/SUT with a one to many, many to one or many output interface of a DUT/SUT where input and output interfaces are
to many mapping of input ports to output ports. grouped in mutually exclusive pairs.
Discussion: Discussion:
This definition follows from the discussions in sections 14 and 16 of In the simplest instance of one-to-one mapped traffic distribution
RFC 1944 on bidirectional traffic and multi-port testing and readily frames are forwarded between one source interface and one destination
extends to configurations with multiple switching devices linked
together over backbone connections. Meshed traffic can be interface of a DUT/SUT. One-to-one mapped traffic distribution extends
unidirectional or bidirectional. to multiple distinct pairs of source and destination interfaces.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
half duplex / full duplex half duplex / full duplex
See Also: See Also:
unidrectional traffic (3.2.1) unidrectional traffic (3.2.1)
bidirectional traffic (3.2.2) bidirectional traffic (3.2.2)
fully meshed traffic (3.2.4) partially meshed traffic (3.3.2.)
bursts (3.3) fully meshed traffic (3.3.3)
burst (3.4.1)
3.2.4 Fully meshed traffic 3.3.2 Partially meshed traffic
Definition: Definition:
Streams of frames switched simultaneously between all of a Frames forwarded between mutually exclusive sets of input and output
designated number of ports of a device such that each of the ports interfaces of a DUT/SUT.
under test will both send frames to and receive frames from all of the
other ports under test. Discussion:
This definition follows from the discussions in sections 14 and 16 of
RFC 1944 on bidirectional traffic and 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.
Measurement units:
n/a
Issues:
half duplex / full duplex
See Also:
unidirectional traffic (3.2.1)
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
Definition:
Frames switched simultaneously between all of a designated number of
interfaces of a device such that each of the interfacess under test
will both forward frames to and receive frames from all of the other
interfaces under test.
Discussion: Discussion:
As with bidirectional multi-port traffic, meshed traffic exercises both As with bidirectional multi-port traffic, meshed traffic exercises both
the transmission and reception sides of the ports of a switching the transmission and reception sides of the interfaces of a switching
device. Since ports are not divided into two groups every port device. Since interfaces are not divided into two groups every
forwards frames to and receives frames from every other port. The interface forwards frames to and receives frames from every other
total number of individual streams when traffic is meshed over n interface. The total number of individual input/output interface
switched ports equals n x (n - 1). This compares with n x (n / 2) such pairs when traffic is meshed over n switched interfaces equals
streams in a bidirectional multi-port test. It should be noted that n x (n - 1). This compares with n x (n / 2) such interface pairs in a
bidirectional multiport traffic can load backbone connections linking bidirectional multi-port test.
together two switching devices more than meshed traffic.
It should be noted that bidirectional meshed traffic on half duplex It should be noted that bidirectional multi-port traffic can load
ports is inherently bursty since ports must interrupt transmission backbone connections linking together two switching devices more
whenever they receive frames. This kind of bursty meshed traffic is than meshed traffic.
characteristic of real network traffic and can be advantageously used
to diagnose a DUT/SUT by exercising many of its component parts Bidirectional meshed traffic on half duplex interfaces is inherently
simultaneously. Additional inspection may be warranted to correlate bursty since interfaces must interrupt transmission whenever they
the frame forwarding capacity of a DUT/SUT when offered meshed receive frames. This kind of bursty meshed traffic is characteristic
traffic and the behavior of individual elements such as input and of real network traffic and can be advantageously used to diagnose a
output buffers, buffer allocation mechanisms, aggregate switching DUT/SUT by exercising many of its component parts simultaneously.
capacity, processing speed or medium access control. Additional inspection may be warranted to correlate the frame
When offering bursty meshed traffic to a DUT/SUT a number of forwarding capacity of a DUT/SUT when offered meshed traffic and
variables have to be considered. These include frame size, the number the behavior of individual elements such as input or output buffers,
of frames within bursts, the interval between bursts as well as the buffer allocation mechanisms, aggregate switching capacity, processing
distribution of load between incoming and outgoing traffic. Terms speed or medium access control.
related to bursts are defined in section 3.3 below.
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 3.3 below.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
half duplex / full duplex half duplex / full duplex
See Also: See Also:
unidrectional traffic (3.2.1) unidirectional traffic (3.2.1)
bidirectional traffic (3.2.2) bidirectional traffic (3.2.2)
partially meshed traffic (3.2.4) one-to-one mapped traffic (3.3.1)
bursts (3.3) partially meshed traffic (3.3.2)
burst (3.4.1)
3.3 Bursts 3.4 Bursts
This group applies to the intervals defining traffic forwarded by This group of definitions applies to the intervals between frames or
DUT/SUT. groups of frames offered to the DUT/SUT.
3.3.1 Burst 3.4.1 Burst
Definition: Definition:
A sequence of frames transmitted with the minimum inter-frame gap A sequence of frames transmitted with the minimum inter-frame gap
allowed by the medium. allowed by the medium.
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
1242 and section 21 of RFC 1944 which describes cases where it is and section 21 of RFC 1944 which describes cases where it is useful to
useful to consider isolated frames as single frame bursts. consider isolated frames as single frame bursts.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
See Also: See Also:
burst size (3.3.2) burst size (3.4.2)
inter-burst gap (IBG) (3.2.3) inter-burst gap (IBG) (3.4.3)
3.2.2 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 streams Burst size can range from one to infinity. In unidirectional traffic
there is no theoretical limit to burst length. When traffic is there is no theoretical limit to burst length. When traffic is
bidirectional or meshed bursts on half duplex media are finite since bidirectional or meshed bursts on half duplex media are finite since
ports interrupt transmission intermittently to receive frames. interfaces interrupt transmission intermittently to receive frames.
On real networks burst size will normally increase with window size. On real networks burst size will normally increase with window size.
This makes it desirable to test devices with small as well as large This makes it desirable to test devices with small as well as large
burst sizes. burst sizes.
Measurement units: Measurement units:
number of N-octet frames number of N-octet frames
Issues: Issues:
See Also: See Also:
burst (3.3.1) burst (3.4.1)
inter-burst gap (IBG) (3.2.3) inter-burst gap (IBG) (3.4.3)
3.2.3 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
1944 on bursty traffic. bursty traffic.
Bidirectional and meshed streams of traffic are inherently bursty
since ports share their time between receiving and transmitting Bidirectional and meshed traffic are inherently bursty since interfaces
frames. External sources offering bursty traffic for a given frame size share their time between receiving and transmitting frames. External
and burst size must adjust the inter-burst gap to achieve a specified sources offering bursty traffic for a given frame size and burst size
rate of transmission. must adjust the inter-burst gap to achieve a specified rate of
transmission.
Measurement units: Measurement units:
nanoseconds nanoseconds
microseconds microseconds
milliseconds milliseconds
seconds seconds
Issues: Issues:
See Also: See Also:
burst (3.3.1) burst (3.4.1)
burst size (3.2.2) burst size (3.4.2)
3.4 Loads 3.5 Loads
This group applies to the rates that traffic is offered to any This group of definitions applies to the rates at which traffic is
DUT/SUT. offered to any DUT/SUT.
3.4.1 Intended load 3.5.1 Intended load (Iload)
Definition: Definition:
The number of frames per second that an external source attempts to The number of frames per second that an external source attempts to
transmit to a DUT/SUT for forwarding to a specified output port or transmit to a DUT/SUT for forwarding to a specified output interface or
ports. interfaces.
Discussion: Discussion:
Collisions on CSMA/CD links or the action of congestion control Collisions on CSMA/CD links or the action of congestion control
mechanisms can effect the rate at which an external source of traffic mechanisms can effect the rate at which an external source of traffic
transmits frames to a DUT/SUT. This makes it useful to distinguish transmits frames to a DUT/SUT. This makes it useful to distinguish the
the load that an external source attempts to apply to a DUT/SUT and load that an external source attempts to apply to a DUT/SUT and the
the load it is observed or measured to apply. load it is observed or measured to apply.
In the case of Ethernet an external source of traffic must implement In the case of Ethernet an external source of traffic must implement
the truncated binary exponential back-off algorithm to ensure that it the truncated binary exponential back-off algorithm to ensure that it
is accessing the medium legally. is accessing the medium legally.
Measurement units: Measurement units:
bits per second bits per second
N-octets per second N-octets per second
(N-octets per second / media_maximum-octets per second) x 100 (N-octets per second / media_maximum-octets per second) x 100
Issues: Issues:
See Also: See Also:
offered load (3.4.2) offered load (3.5.2)
3.4.2 Offered load 3.5.2 Offered load (Oload)
Definition: Definition:
The number of frames per second that an external source can be The number of frames per second that an external source can be observed
observed or measured to transmit to a DUT/SUT for forwarding to a or measured to transmit to a DUT/SUT for forwarding to a specified
specified output port or ports. output interface or interfaces.
Discussion: Discussion:
The load which an external device can be observed to apply to a The load which an external device can be observed to apply to a DUT/SUT
DUT/SUT may be less than the load the external device attempts to may be less than the load the external device attempts to apply due to
apply due to collisions or the action of congestion control collisions or the action of congestion control mechanisms. Frames which
mechanisms. are not successfully transmitted by an external source of traffic to a
Frames which are not successfully transmitted by an external source DUT/SUT MUST NOT be counted as transmitted frames when measuring the
of traffic to a DUT/SUT MUST NOT be counted as transmitted forwarding rate of a DUT/SUT.
frames when measuring the forwarding rate of a DUT/SUT.
The frame count on a port of a DUT/SUT may exceed the rate at 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 which an external device offers frames due to the presence of spanning
spanning tree BPDUs (Bridge Protocol Data Units) on 802.1D- tree BPDUs (Bridge Protocol Data Units) on 802.1D-compliant switches or
compliant switches or SNMP frames. Such frames should be treated SNMP frames. Such frames should be treated as modifiers as described in
as modifiers as described in section 11 of RFC 1944. section 11 of RFC 1944.
Measurement units: Measurement units:
bits per second bits per second
N-octets per second N-octets per second
(N-octets per second / media_maximum-octets per second) x 100 (N-octets per second / media_maximum-octets per second) x 100
Issues: Issues:
token ring token ring
See also: See also:
intended load (3.4.1)
3.4.3 Maximum offered load intended load (3.5.1)
3.5.3 Maximum offered load (MOL)
Definition: Definition:
The highest number of frames per second that an external source can The highest number of frames per second that an external source can
transmit to a DUT/SUT for forwarding to a specified output port or transmit to a DUT/SUT for forwarding to a specified output interface
ports. or interfaces.
Discussion: Discussion:
The maximum load that an external device can apply to a DUT/SUT The maximum load that an external device can apply to a DUT/SUT may not
may not equal the maximum load allowed by the medium. This will equal the maximum load allowed by the medium. This will be the case
be the case when an external source lacks the resources to transmit when an external source lacks the resources to transmit frames at the
frames at the minimum legal inter-frame gap or when it has sufficient minimum legal inter-frame gap or when it has sufficient resources to
resources to transmit frames below the minimum legal inter-frame transmit frames below the minimum legal inter-frame gap. Moreover,
gap. Moreover, maximum load may vary with respect to parameters maximum load may vary with respect to parameters other than a medium's
other than a medium's maximum theoretical utilization. For example, maximum theoretical utilization. For example, on those media employing
on those media employing tokens, maximum load may vary as a tokens, maximum load may vary as a function of Token Rotation Time,
function of Token Rotation Time, Token Holding Time, or the ability Token Holding Time, or the ability to chain multiple frames to a single
to chain multiple frames to a single token. token. The maximum load that an external device applies to a DUT/SUT
The maximum load that an external device applies to a DUT/SUT
MUST be specified when measuring forwarding rates. MUST be specified when measuring forwarding rates.
Measurement units: Measurement units:
bits per second bits per second
N-octets per second N-octets per second
(N-octets per second / media_maximum-octets per second) x 100 (N-octets per second / media_maximum-octets per second) x 100
Issues: Issues:
See Also: See Also:
offered load (3.4.2) offered load (3.5.2)
3.4.4 Overloading 3.5.4 Overloading
Definition: Definition:
Attempting to load a DUT/SUT in excess of the maximum rate of Attempting to load a DUT/SUT in excess of the maximum rate of
transmission allowed by the medium. transmission allowed by the medium.
Discussion: Discussion:
Overloading can serve to exercise buffers and buffer allocation Overloading can serve to exercise buffers and buffer allocation
algorithms as well as congestion control mechanisms. algorithms as well as congestion control mechanisms.
The number of input port or ports required to overload one or more
output ports of a DUT/SUT will vary according to the media rates of The number of input interfaces required to overload one or more output
the ports involved. An external source can also overload a port by interfaces of a DUT/SUT will vary according to the media rates of the
transmitting frames below the minimum inter-frame gap. This can interfaces involved. An external source can also overload an interface
by transmitting frames below the minimum inter-frame gap. This can
serve to determine whether a device respects the minimum inter-frame serve to determine whether a device respects the minimum inter-frame
gap. Overloading can be achieved with unidirectional, bidirectional gap.
and meshed traffic.
Overloading can be achieved with unidirectional, bidirectional and
meshed traffic.
Measurement units: Measurement units:
N-octets per second N-octets per second
(N-octets per second / media_maximum-octets per second) x 100 (N-octets per second / media_maximum-octets per second) x 100
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
offered load (3.4.2) offered load (3.5.2)
3.5 Forwarding rates 3.6 Forwarding rates
This group applies to the rates at which traffic is forwarded by any This group of definitions applies to the rates at which traffic is
DUT/SUT in response a stimulus. forwarded by any DUT/SUT in response to a stimulus.
3.5.1 Forwarding rate 3.6.1 Forwarding rate (FR)
Definition: Definition:
The number of frames per second that a device can be observed to The number of frames per second that a device can be observed to
successfully transmit to the correct destination port in response to a successfully transmit to the correct destination interface in response
specified offered load. to a specified offered load.
Discussion: Discussion:
Unlike throughput defined in section 3.17 of RFC 1242, forwarding Unlike throughput defined in section 3.17 of RFC 1242, forwarding rate
rate makes no explicit reference to frame loss. Forwarding rate, makes no explicit reference to frame loss. Forwarding rate refers to
which must only be sampled on the output side of the ports under the number of frames per second observed on the output side of the
test, can be measured for unidirectional, bidirectional or meshed interface under test and MUST be reported in relation to the offered
traffic and should be sampled in fixed time intervals of one second. If load. Forwarding rate can be measured with different traffic
longer or shorter intervals are used they should be cited when orientations and distributions.
reporting a device's forwarding rate.
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
sensitive to the action of congestion control mechanisms. may be 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 (3.4.2) offered load (3.5.2)
forwarding rate at maximum offered load (3.5.2) forwarding rate at maximum offered load (3.6.2)
maximum forwarding rate (3.5.3) maximum forwarding rate (3.6.3)
3.5.2 Forwarding rate at maximum offered load 3.6.2 Forwarding rate at maximum offered load (FRMOL)
Definition: Definition:
The number of frames per second that a device can be observed to The number of frames per second that a device can be observed to
successfully transmit to the correct destination port in response to the successfully transmit to the correct destination interface in response
maximum offered load. 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
maximum rate at which a device can be observed to successfully 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 This will be the case when the ability of a device to forward frames
forward frames degenerates when offered traffic at maximum load.
Maximum offered load must be cited when reporting forwarding rate degenerates when offered traffic at maximum load. Maximum offered load
at 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 (3.4.3) maximum offered load (3.5.3)
forwarding rate (3.5.1) forwarding rate (3.6.1)
maximum forwarding rate (3.5.3) maximum forwarding rate (3.6.3)
3.5.3 Maximum forwarding rate 3.6.3 Maximum forwarding rate (MFR)
Definition: Definition:
The highest forwarding rate of a DUT/SUT taken from an iterative set The highest forwarding rate of a DUT/SUT taken from an iterative set
of forwarding rate measurements. of forwarding rate measurements.
Discussion: Discussion:
The forwarding rate of a device may degenerate before maximum load The forwarding rate of a device may degenerate before maximum load is
is reached. The load applied to a device must be cited when reporting reached. The load applied to a device must be cited when reporting
maximum forwarding rate. maximum forwarding rate.
The following example illustrates how the terms relative to loading and
forwarding rates are meant to be used. In particular it shows how the
distinction between forwarding rate at maximum offered load (FRMOL)
and maximum forwarding rate (MFR)can be used to characterize a DUT/SUT.
(A) (B)
Test Device DUT/SUT
Offered Rate Forwarding Rate
------------ ---------------
1. 14,880 fps 7,400 fps
2. 13,880 fps 8,472 fps
3. 12,880 fps 12,880 fps
Column A - Oload
Column B - FR
Row 1, Col A - MOL
Row 1, Col B - FRMOL
Row 3, Col B - MFR
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
offered load (3.4.2) offered load (3.5.2)
forwarding rates (3.5.1) forwarding rates (3.6.1)
forwarding rate at maximum load (3.5.2) forwarding rate at maximum load (3.6.2)
3.6 Congestion 3.7 Congestion control
This group applies to the behavior of a DUT/SUT when congestion
or contention is present.
3.6.1 Backpressure This group of definitions applies to the behavior of a DUT/SUT when
congestion or contention is present.
3.7.1 Backpressure
Definition: Definition:
Any technique used by a DUT/SUT to attempt to avoid frame loss by Any technique used by a DUT/SUT to attempt to avoid frame loss by
impeding external sources of traffic from transmitting frames to impeding external sources of traffic from transmitting frames to
congested ports. congested interfaces.
Discussion: Discussion:
Some switches send jam signals, for example preamble bits, back to Some switches send jam signals, for example preamble bits, back to
traffic sources when their transmit amd/or receive buffers start to traffic sources when their transmit and/or receive buffers start to
overfill. Switches implementing full duplex Ethernet links may use overfill. Switches implementing full duplex Ethernet links may use IEEE
IEEE 802.3x Flow Control for the same purpose. Such devices may 802.3x Flow Control for the same purpose. Such devices may incur no
incur no frame loss when external sources attempt to offer traffic to frame loss when external sources attempt to offer traffic to congested
congested or overloaded ports. or overloaded interfaces.
It shoulkd be noted that jamming and other flow control methods
may slow all traffic transmitted to congested input ports including It should be noted that jamming and other flow control methods may slow
traffic intended for uncongested output ports. all traffic transmitted to congested input interfaces including traffic
intended for uncongested output interfaces.
Measurement units: Measurement units:
frame loss on congested port or ports frame loss on congested interface or interfaces
N--octet frames per second between the port applying backpressure N--octet frames per second between the interface applying backpressure
and an uncongested and an uncongested destination interface
destination port
Issues: Issues:
jamming not explicitly described in standards jamming not explicitly described in standards
See Also: See Also:
forward pressure (3.6.2) forward pressure (3.7.2)
3.6.2 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
standardized protocol in an attempt to increase the forwarding protocol in an attempt to increase the forwarding performance of a
performance of a DUT/SUT. DUT/SUT.
Discussion: Discussion:
A DUT/SUT may be found to inhibit or abort backoff algorithms in A DUT/SUT may be found to inhibit or abort back-off algorithms in order
order to force access to the medium when contention occurs. It to force access to the medium when contention occurs. It should be
should be noted that the backoff algorithm should be fair whether the noted that the back-off algorithm should be fair whether the DUT/SUT is
DUT/SUT is in a congested or an uncongested state. Transmission in a congested or an uncongested state. Transmission below the minimum
below the minimum inter-frame gap or the disregard of flow control inter-frame gap or the disregard of flow control primitives fall into
primitives fall into this category. this category.
Measurement units: Measurement units:
intervals between frames in microseconds intervals between frames in microseconds
intervals in microseconds between transmission retries during 16 intervals in microseconds between transmission retries during 16
successive collisions. successive collisions.
Issues: Issues:
truncated binary exponential backoff algorithm truncated binary exponential back-off algorithm
See also: See also:
backpressure (3.6.1) backpressure (3.7.1)
3.6.3 Head of line blocking 3.7.3 Head of line blocking
Definition: Definition:
Frame loss observed on an uncongested output port whenever frames Frame loss observed on an uncongested output interface whenever frames
are received from an input port which is also attempting to forward are received from an input interface which is also attempting to
frames to a congested output port. forward frames to a congested output interface.
Discussion: Discussion:
It is important to verify that a switch does not slow transmission or It is important to verify that a switch does not slow transmission or
drop frames on ports which are not congested whenever overloading drop frames on interfaces which are not congested whenever overloading
on one of its other ports occurs. on one of its other interfaces occurs.
Measurement units: Measurement units:
frame loss recorded on an uncongested port when receiving frames frame loss recorded on an uncongested interface when receiving frames
from a port which is also forwarding frames to a congested port. from an interface which is also 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)
3.7 Address handling 3.8 Address handling
This group applies to the process of address resolution which enables
a DUT/SUT to forward frames to the correct destination.
3.7.1 Address caching capacity This group of definitions applies to the process of address resolution
which enables a DUT/SUT to forward frames to the correct destination.
3.8.1 Address caching capacity
Definition: Definition:
The number of MAC addresses per n ports, per module or per device The number of MAC addresses per n interfaces, per module or per device
that a DUT/SUT can cache and successfully forward frames to that a DUT/SUT can cache and successfully forward frames to without
without flooding or dropping frames. flooding or dropping frames.
Discussion: Discussion:
Users building networks will want to know how many nodes they can Users building networks will want to know how many nodes they can
connect to a DUT/SUT. This makes it necessary to verify the number connect to a DUT/SUT. This makes it necessary to verify the number of
of MAC addresses that can be assigned per n ports, per module and MAC addresses that can be assigned per n interfaces, per module and per
per chassis before a DUT/SUT begins flooding frames. chassis before a DUT/SUT begins flooding frames.
Measurement units: Measurement units:
number of MAC addresses per n ports, per module and/or per chassis number of MAC addresses per n interfaces, per module and/or per chassis
Issues: Issues:
See Also: See Also:
Address learning rate (3.7.2) Address learning rate (3.8.2)
3.7.2 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
before starting to flood or drop frames. starting to flood or drop 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
address tables. This information is useful to have when considering tables. This information is useful to have when considering how long it
how long it takes a network to come up when many users log on in takes a network to come up when many users log on in the morning or
the morning or after a network crash. after a network crash.
Measurement units: Measurement units:
frames per second with each successive frame sent to the switch frames per second with each successive frame sent to the switch
containing a different source address. containing a different source address.
Issues: Issues:
See Also: address caching capacity (3.7.1) See Also: address caching capacity (3.8.1)
3.7.3 Flood count 3.8.3 Flood count
Definition: Definition:
Frames forwarded to ports 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 a destination MAC address information when traffic is offered to a
DUT/SUT for forwarding. DUT/SUT for forwarding.
Discussion: Discussion:
When recording throughput statistics it is important to check that When recording throughput statistics it is important to check that
frames have been forwarded to their proper destinations. Flooded frames have been forwarded to their proper destinations. Flooded frames
frames MUST NOT be counted as received frames. Both known and MUST NOT be counted as received frames. Both known and unknown unicast
unknown unicast frames can be flooded. 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 (3.7.1) address caching capacity (3.8.1)
3.8 Errored frame filtering 3.9 Errored frame filtering
This group applies to frames with errors which a DUT/SUT may
filter.
3.8.1 Errored frames This group of definitions applies to frames with errors which a DUT/SUT
may filter.
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
errored Frame Check Sequence. Frame Check Sequence.
Discussion: Discussion:
Switches, unlike IEEE 802.1d compliant bridges, do not necessarily Switches, unlike IEEE 802.1d compliant bridges, do not necessarily
filter all types of illegal frames. Some switches, for example, which filter all types of illegal frames. Some switches, for example, which
do not store frames before forwarding them to their destination ports do not store frames before forwarding them to their destination
may not filter over-sized frames (jabbers) or verify the validity of the interfaces may not filter over-sized frames (jabbers) or verify the
Frame Check Sequence field. Other illegal frames are under-sized validity of the Frame Check Sequence field. Other illegal frames are
frames (runts) and misaligned frames. under-sized frames (runts) and misaligned frames.
Measurement units: Measurement units:n/a
n/a
Issues: Issues:
See Also: See Also:
3.9 Broadcasts 3.10 Broadcasts
This group applies to MAC layer and network layer broadcast This group of definitions applies to MAC layer and network layer
frames. broadcast frames.
3.9.1 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 ports located within a broadcast domain in
response to a specified offered load.
Discussion: observed to deliver to all interfaces located within a broadcast domain
There is no standard forwarding mechanism used by switches to in response to a specified offered load.
forward broadcast frames. It is useful to determine the broadcast
forwarding rate for frames switched between ports on the same card,
ports on different cards in the same chassis and ports on different
chassis linked together over backbone connections. The terms
maximum broadcast forwarding rate and broadcast forwarding rate at
maximum load follow directly from the terms already defined for
forwarding rate measurements in section 3.5 above.
Measurement units: Discussion:
There is no standard forwarding mechanism used by switches to forward
broadcast frames. It is useful to determine the broadcast forwarding
rate for frames switched between interfaces on the same card, interfaces
on different cards in the same chassis and interfaces on different
chassis linked together over backbone connections. The terms maximum
broadcast forwarding rate and broadcast forwarding rate at maximum load
follow directly from the terms already defined for forwarding rate
measurements in section 3.6 above.Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
forwarding rate at maximum load (3.5.2) forwarding rate at maximum load (3.6.2)
maximum forwarding rate (3.5.3) maximum forwarding rate (3.6.3)
broadcast latency (3.9.2) broadcast latency (3.10.2)
3.9.2 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
each port located within a broadcast domain. interface located within a broadcast domain.
Discussion: Discussion:
Since there is no standard way for switches to process broadcast Since there is no standard way for switches to process broadcast
frames, broadcast latency may not be the same on all receiving ports frames, broadcast latency may not be the same on all receiving
of a switching device. The latency measurements SHOULD be bit interfaces of a switching device. The latency measurements SHOULD be
oriented as described in 3.8 of RFC 1242. It is useful to determine bit oriented as described in 3.8 of RFC 1242. It is useful to determine
broadcast latency for frames forwarded between ports on the same broadcast latency for frames forwarded between interfaces on the same
card, ports on different cards in the same chassis and ports on card, interfaces on different cards in the same chassis and interfaces
different chassis linked together over backbone connections. on different chassis linked together over backbone connections.
Measurement units: Measurement units:
nanoseconds nanoseconds
microseconds microseconds
milliseconds milliseconds
seconds seconds
Issues: Issues:
See Also: See Also:
broadcast forwarding rate (3.9.1) broadcast forwarding rate (3.10.1)
4. References: 4. Security Considerations
1. RFC 1242 "Benchmarking Terminology for Network Interconnect
Devices"
2. RFC 1944 "Benchmarking Methodology for Network Interconnect
Devices"
5. Acknowledgments This document raises no security issues.
A special thanks goes to the IETF BenchMark WorkGroup for the 5. References:
many suggestions it collectively made to help complete this draft.
Kevin Dubray (Bay Networks), Jean-Christophe Bestaux (ENL),
Ajay Shah ( WG), Henry Hamon (Netcom Systems), Stan Kopek
(3Com) and Doug Ruby (Prominet) all provided valuable input at
various stages of this project.
The editor 1. RFC 1242 "Benchmarking Terminology for Network Interconnect Devices"
Bob Mandeville 2. RFC 1944 "Benchmarking Methodology for Network Interconnect Devices"
5. Editor's Address 6. Acknowledgments
A special thanks goes to the IETF BenchMarking Methodology 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
Robert Mandeville Robert Mandeville
ENL (European Network Laboratories) European Network Laboratories (ENL)
35, rue Beaubourg 6, Parc Ariane "Le Mercure"
75003 Paris Boulevard des Chenes
78284 Guyancourt
France France
mobile phone: +33 6 07 47 67 10
phone: +33 1 39 44 12 05 phone: + 33 1 39 44 12 05 or mobile phone + 33 6 07 47 67 10
fax: + 33 1 39 44 12 06 fax: + 33 1 39 44 12 06
email: bob.mandeville@eunet.fr email: bob.mandeville@eunet.fr
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/