draft-ietf-bmwg-lanswitch-02.txt   draft-ietf-bmwg-lanswitch-03.txt 
Network Working Group R. Mandeville Network Working Group R. Mandeville
INTERNET-DRAFT European Network Laboratories INTERNET-DRAFT European Network Laboratories
Expiration Date: Jun 1997 Jan 1997 Expiration Date: Jul 1997 Feb 1997
Benchmarking Terminology for LAN Switching Devices Benchmarking Terminology for LAN Switching Devices
< draft-ietf-bmwg-lanswitch-02.txt >
< draft-ietf-bmwg-lanswitch-03.txt >
Status of this Document Status of this Document
This document is an Internet-Draft. Internet-Drafts are working documents of This document is an Internet-Draft. Internet-Drafts are working documents of
the Internet Engineering Task Force (IETF), its areas, and its working the Internet Engineering Task Force (IETF), its areas, and its working
groups. Note that other groups may also distribute working documents as groups. Note that other groups may also distribute working documents as
Internet-Drafts. Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and Internet-Drafts are draft documents valid for a maximum of six months and
may be updated, replaced, or obsoleted by other documents at any time. It is may be updated, replaced, or obsoleted by other documents at any time. It is
skipping to change at line 183 skipping to change at line 184
backbone connections linking together two switching devices more than meshed backbone connections linking together two switching devices more than meshed
traffic. traffic.
Meshed traffic on half duplex ports is inherently bursty since ports must Meshed traffic on half duplex ports is inherently bursty since ports must
interrupt transmission whenever they receive frames. Bursty meshed traffic interrupt transmission whenever they receive frames. Bursty meshed traffic
which is characteristic of real network traffic simultaneously exercises which is characteristic of real network traffic simultaneously exercises
many of the component parts of a switching device such as input and output many of the component parts of a switching device such as input and output
buffers, buffer allocation mechanisms, aggregate switching capacity, buffers, buffer allocation mechanisms, aggregate switching capacity,
processing speed and behavior of the medium access controller. processing speed and behavior of the medium access controller.
When offering bursty meshed traffic to a device under test a number of When offering bursty meshed traffic to a device under test a number of
variables have to be considered. These include frame size, the number of variables have to be considered. These include frame size, the number of
frames within bursts as well as the interval between bursts. The terms frames within bursts, the interval between bursts as well as the
burst, burst size and inter-burst gap are defined in sections 2.5, 2.6 and distribution of load between incoming and outgoing traffic. The terms burst,
2.7 below. burst size and inter-burst gap are defined in sections 2.5, 2.6 and 2.7
below. Load and balanced load are defined in sections 2.8 and 2.10 below.
Measurement units: Measurement units:
n/a n/a
Issues: Issues:
half duplex / full duplex half duplex / full duplex
See Also: See Also:
unidirectional traffic (2.2) unidirectional traffic (2.2)
bidirectional traffic (2.3) bidirectional traffic (2.3)
burst (2.5) burst (2.5)
burst size (2.6) burst size (2.6)
inter-burst gap (2.7) inter-burst gap (2.7)
load (2.8)
balanced load (2.10)
2.5 Burst 2.5 Burst
Definition: Definition:
A sequence of frames transmitted with the minimum inter-frame gap allowed by A sequence of frames transmitted with the minimum inter-frame gap allowed by
the medium. the medium.
Discussion: Discussion:
This definition follows from discussions in section 3.16 of RFC 1242 and This definition follows from discussions in section 3.16 of RFC 1242 and
section 21 of RFC 1944 which describes cases where it is useful to consider section 21 of RFC 1944 which describes cases where it is useful to consider
skipping to change at line 267 skipping to change at line 271
seconds seconds
Issues: Issues:
See Also: See Also:
burst size (2.6) burst size (2.6)
2.8 Port load 2.8 Port load
Definition: Definition:
The number of frames per second that a switched port transmits and receives. The total number of frames per second that a switched port can be observed
to transmit and receive in response to an offered load.
Discussion: Discussion:
Port load can be expressed in a number of ways: bits per second, frames per Port load can be expressed in a number of ways: bits per second, frames per
second with the frame size specified or as a percentage of the maximum frame second with the frame size specified or as a percentage of the maximum frame
rate allowed by the medium for a given frame size. In the case of rate allowed by the medium for a given frame size. In the case of
bidirectional or meshed traffic port load is the sum of the frames bidirectional or meshed traffic port load is the sum of the frames
transmitted and received on a port per second. The load on an Ethernet port transmitted and received on a port per second. The load on an Ethernet port
which is transmitting and receiving a total of 7440 64-byte frames per which is transmitting and receiving a total of 7440 64-byte frames per
second equals 50% given that the maximum rate of transmission on an Ethernet second equals 50% given that the maximum rate of transmission on an Ethernet
is 14880 64-byte frames per second. is 14880 64-byte frames per second.
There is room for varying the balance between incoming and outgoing traffic
when loading ports with bidirectional and meshed traffic. When offering
meshed traffic to a device the equal distribution of load over all ports
will help avoid unwanted or inadvertent port overloading in throughput tests.
Measurement units: Measurement units:
bits per second bits per second
frames per second with the frame size specified frames per second with the frame size specified
as a percentage of the maximum frame rate allowed by the medium for a given as a percentage of the maximum frame rate allowed by the medium for a given
frame size. frame size.
Issues: Issues:
See Also: See Also:
bidirectional traffic (2.3) bidirectional traffic (2.3)
meshed traffic (2.4) meshed traffic (2.4)
overload (2.9) offered load (2.9)
overload (2.12)
2.9 Overload
Definition:
Loading a port or ports in excess of the maximum rate of transmission
allowed by the medium.
Discussion:
Overloading can serve to exercise input and output buffers, buffer
allocation algorithms and congestion control mechanisms.
Port overloading with unidirectional traffic requires a minimum of two input
and one output ports when the medium rate of all ports is the same. The
number of input ports will vary according to the media rates of the output
port or ports under test.
Port overloading with bidirectional and meshed traffic requires the sum of
the traffic transmitted and received on each port to exceed the maximum rate
of transmission allowed by the medium. To distribute port overload equally,
the external source of traffic must transmit at the same rate situated
between more than 50% and a 100% of the maximum medium rate to each of the
ports under test.
Measurement units:
N-octet frames per second
Issues:
See Also:
bidirectional traffic (2.3)
meshed traffic (2.4)
port load (2.8)
2.10 Intended rate
Definition: 2.9 Offered load
The number of frames per second that an external source attempts to send to The total number of frames per second that an external source attempts to
a port of a device under test. transmit or address to a port of a device under test.
Discussion: Discussion:
An external source may not transmit frames to a device under test at the Collisions on CSMA/CD links or the action of congestion control mechanisms
intended rate due to collisions on CSMA/CD links or the action of congestion can reduce the rate of transmission of external sources sending or
control mechanisms. This makes it useful to distinguish between intended addressing traffic to a port under test. This makes it useful to distinguish
rate and the rate at which the source can be observed to send frames to a port load, the load that can be observed on a port, from the load that an
device under test. external source offers, that is, attempts to send or address to the port.
An external source should have sufficient internal resources to transmit In the case of Ethernet an external source of traffic must implement the
frames at the intended rate and in the case of Ethernet must implement the
truncated binary exponential back-off algorithm when executing bidirectional truncated binary exponential back-off algorithm when executing bidirectional
and meshed performance tests to ensure that it is accessing the medium legally. and meshed performance tests to ensure that it is accessing the medium legally.
Frames which are not successfully transmitted by the external source of Frames which are not successfully transmitted by an external source of
traffic to the device under test MUST NOT be counted as transmitted frames traffic to the device under test MUST NOT be counted as transmitted frames
in performance benchmarks. in performance benchmarks.
The frame count on a port of a device under test 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. If such frames cannot be inhibited, they MUST be left out of frame
counts in performance benchmarks.
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:
offered rate (2.11) port load (2.8)
2.11 Offered rate 2.10 Balanced load
Definition: Definition:
The number of frames per second that an external source can be observed to Port load when the total number of frames per second that an external source
send to a port of a device under test. attempts to transmit to a port of a device under test equals the total
number of frames per second that the external source attempts to address to
the same port.
Discussion: Discussion:
Offered rate may differ from intended rate due to collisions on half duplex There is room for varying the balance between incoming and outgoing traffic
media or congestion control mechanisms. when loading ports with bidirectional and meshed traffic. A balanced load on
The frame count on a port of a device under test may exceed the rate at all ports will help avoid unwanted or inadvertent port overloading in
which an external device offers frames due to the presence of spanning tree throughput tests.
BPDUs (Bridge Protocol Data Units) on 802.1D-compliant switches or SNMP
frames. If such frames cannot be inhibited, they MUST be left out of frame
counts in performance benchmarks.
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
See also: See also:
intended rate (2.10) port load (2.8)
offered load (2.9)
2.12 Maximum load 2.11 Maximum load
Definition: Definition:
The load which results on a port when traffic is transmitted or addressed to Port load when the offered load equals the maximum rate allowed by the medium.
it at the maximum rate allowed by the medium.
Discussion: Discussion:
Maximum port load may be less than the maximum rate allowed by the medium Maximum load in balanced bidirectional and meshed traffic tests requires the
when the offered rate of the external sources sending traffic to the device number of frames per second an external source attempts to transmit to a
or system under test is less than the intended rate. port and the number of frames per second the source attempts to address to
the same port to be equally divided and total to the maximum rate of
transmission allowed by the medium.
Measurement units: Measurement units:
bits per second bits per second
frames per second with the frame size specified frames per second with the frame size specified
as a percentage of the maximum frame rate allowed by the medium for a given as a percentage of the maximum frame rate allowed by the medium for a given
frame size. frame size.
Issues: Issues:
See Also: See Also:
bidirectional traffic (2.3) bidirectional traffic (2.3)
meshed traffic (2.4) meshed traffic (2.4)
port load (2.8) port load (2.8)
intended rate (2.10) offered load (2.9)
offered rate (2.11)
forwarding rate (2.13)
forwarding rate at maximum load (2.14)
2.13 Forwarding rate 2.12 Overload
Definition: Definition:
The number of frames per second that a device is observed to deliver to the Loading a port or ports in excess of the maximum rate of transmission
correct output port in response to a known intended rate. allowed by the medium.
Discussion: Discussion:
Forwarding rate does not take frame loss into account and must only be Overloading can serve to exercise input and output buffers, buffer
sampled on the output side of the ports under test. It can be measured on allocation algorithms and congestion control mechanisms.
devices offered unidirectional, bidirectional or meshed traffic. Port overloading with unidirectional traffic requires a minimum of two input
The forwarding rates of switching devices which exhibit no frame loss may be and one output ports when the medium rate of all ports is the same. The
reduced through the action of congestion control mechanisms. number of input ports will vary according to the media rates of the output
port or ports under test.
Port overloading with bidirectional and meshed traffic requires the offered
load on each port to exceed the maximum rate of transmission allowed by the
medium.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
bidirectional traffic (2.3)
meshed traffic (2.4)
port load (2.8) port load (2.8)
intended rate (2.10)
offered rate (2.11)
forwarding rate at maximum load (2.14)
2.14 Forwarding rate at maximum load 2.13 Forwarding rate
Definition: Definition:
The number of frames per second that a device is observed to successfully The number of frames per second that a device can be observed to deliver to
deliver to the correct output port at maximum load. the correct output port in response to an offered load.
Discussion: Discussion:
Forwarding rate at maximum load may be less than the maximum rate at which a Forwarding rate does not take frame loss into account and must only be
device might be observed to successfully forward traffic. sampled on the output side of the ports under test. It can be measured on
devices offered unidirectional, bidirectional or meshed traffic with
balanced loads to help avoid unwanted or inadvertent port overloading in
throughput tests.
The forwarding rates of switching devices which exhibit no frame loss may
decrease when congestion control mechanisms are active.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
Issues: Issues:
See Also: See Also:
maximum load (2.12) port load (2.8)
forwarding rate (2.13) offered load (2.9)
forwarding rate at maximum load (2.14)
2.15 Flooding 2.14 Forwarding rate at maximum load
Definition: Definition:
Frames received on ports which do not correspond to the destination MAC Forwarding rate when the offered load equals the maximum rate allowed by the
address information. medium.
Discussion: Discussion:
When recording throughput statistics it is important to check that frames Forwarding rate at maximum load may be less than the maximum rate at which a
have been forwarded to their proper destinations. Flooded frames MUST NOT be device can be observed to successfully forward traffic.
counted as received frames. Both known and unknown unicast frames can be
flooded.
Measurement units: Measurement units:
N-octet valid frames per second N-octet frames per second
Issues: Issues:
Spanning tree BPDUs.
See Also: See Also:
maximum load (2.11)
forwarding rate (2.13)
2.16 Backpressure 2.15 Backpressure
Definition: Definition:
Techniques whereby switching devices avoid frame loss by impeding external Techniques whereby switching devices attempt to avoid frame loss by impeding
sources of traffic from transmitting frames to congested ports. external sources of traffic from transmitting frames to congested ports.
Discussion: Discussion:
Some switches send jam signals, for example preamble bits, back to traffic Some switches send jam signals, for example preamble bits, back to traffic
sources when their transmit and/or receive buffers start to overfill. sources when their transmit and/or receive buffers start to overfill.
Switches implementing full duplex Ethernet links may use IEEE 802.3x Flow Switches implementing full duplex Ethernet links may use IEEE 802.3x Flow
Control for the same purpose. Such devices may incur no frame loss when Control for the same purpose. Such devices may incur no frame loss when
external sources attempt to offer traffic to congested or overloaded ports. external sources attempt to offer traffic to congested or overloaded ports.
Jamming and flow control normally slow all traffic transmitted to congested Jamming and flow control normally slow all traffic transmitted to congested
input ports including traffic intended for uncongested output ports. input ports including traffic intended for uncongested output ports.
Measurement units: Measurement units:
frame loss on congested port or ports frame loss on congested port or ports
N--octet frames per second between the port applying backpressure and an N--octet frames per second between the port applying backpressure and an
uncongested uncongested
destination port destination port
Issues: Issues:
jamming not explicitly described in standards jamming not explicitly described in standards
See Also: See Also:
forward pressure (2.17) forward pressure (2.16)
2.17 Forward pressure 2.16 Forward pressure
Definition: Definition:
An illegal technique whereby a device retransmits buffered frames without An illegal technique whereby a device retransmits buffered frames without
waiting for the interval calculated by the normal operation of the back-off waiting for the interval calculated by the normal operation of the back-off
algorithm. algorithm.
Discussion: Discussion:
Some switches illegally inhibit or abort the truncated binary exponential Some switches illegally inhibit or abort the truncated binary exponential
backoff algorithm and force access to the medium to avoid frame loss. backoff algorithm and force access to the medium to avoid frame loss.
The backoff algorithm should be fair whether the device under test is in a The backoff algorithm should be fair whether the device under test is in a
congested or an uncongested state. congested or an uncongested state.
Measurement units: Measurement units:
intervals in microseconds between transmission retries during 16 successive intervals in microseconds between transmission retries during 16 successive
collisions. collisions.
Issues: Issues:
truncated binary exponential backoff algorithm truncated binary exponential backoff algorithm
See also: See also:
backpressure (2.16) backpressure (2.15)
2.18 Head of line blocking 2.17 Head of line blocking
Definition: Definition:
Frame loss observed on an uncongested output port whenever frames are Frame loss observed on an uncongested output port whenever frames are
received from an input port which is also attempting to forward frames to a received from an input port which is also attempting to forward frames to a
congested output port. congested output port.
Discussion: Discussion:
It is important to verify that a switch does not slow transmission or drop It is important to verify that a switch does not slow transmission or drop
frames on ports which are not congested whenever overloading on one of its frames on ports which are not congested whenever overloading on one of its
other ports occurs. other ports occurs.
skipping to change at line 546 skipping to change at line 525
Measurement units: Measurement units:
frame loss recorded on an uncongested port when receiving frames from a port frame loss recorded on an uncongested port when receiving frames from a port
which is also forwarding frames to a congested port. which is also forwarding frames to a congested port.
Issues: Issues:
input buffers input buffers
See Also: See Also:
unidirectional traffic (2.2) unidirectional traffic (2.2)
2.19 Address handling 2.18 Address handling
Definition: Definition:
The number of MAC addresses per n ports, per module or per device which a The number of MAC addresses per n ports, per module or per device which a
switch can cache and successfully forward frames to without flooding or switch can cache and successfully forward frames to without flooding or
dropping frames. dropping frames.
Discussion: Discussion:
Users building networks will want to know how many nodes they can connect to Users building networks will want to know how many nodes they can connect to
a switch. This makes it necessary to verify the number of MAC addresses that a switch. This makes it necessary to verify the number of MAC addresses that
can be assigned per n ports, per module and per chassis before a switch can be assigned per n ports, per module and per chassis before a switch
begins flooding frames. begins flooding frames.
Measurement units: Measurement units:
number of MAC addresses number of MAC addresses
Issues: Issues:
See Also: See Also:
Address learning rate (2.20) Address learning rate (2.19)
2.20 Address learning rate 2.19 Address learning rate
Definition: Definition:
The maximum rate at which a switch can learn new MAC addresses before The maximum rate at which a switch can learn new MAC addresses 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 address Users may want to know how long it takes a switch to build its address
tables. This information is useful to have when considering how long it tables. This information is useful to have when considering how long it
takes a network to come up when many users log on in the morning or after a takes a network to come up when many users log on in the morning or after a
network crash. network crash.
Measurement units: Measurement units:
frames per second with each successive frame sent to the switch containing a frames per second with each successive frame sent to the switch containing a
different source address. different source address.
Issues: Issues:
See Also: address handling (2.19) See Also: address handling (2.18)
2.20 Flooding
Definition:
Frames received on ports which do not correspond to the destination MAC
address information.
Discussion:
When recording throughput statistics it is important to check that frames
have been forwarded to their proper destinations. Flooded frames MUST NOT be
counted as received frames. Both known and unknown unicast frames can be
flooded.
Measurement units:
N-octet valid frames per second
Issues:
Spanning tree BPDUs.
See Also:
2.21 Illegal frames 2.21 Illegal frames
Definition: Definition:
Frames which are over-sized, under-sized, misaligned or with an errored Frames which are over-sized, under-sized, misaligned or with an errored
Frame Check Sequence. Frame Check Sequence.
Discussion: Discussion:
Switches, unlike IEEE 802.1d compliant brdiges, do not necessarily filter Switches, unlike IEEE 802.1d compliant brdiges, do not necessarily filter
all types of illegal frames. Some switches, for example, which do not store all types of illegal frames. Some switches, for example, which do not store
skipping to change at line 612 skipping to change at line 611
Measurement units: Measurement units:
N-octet frames filtered or not filtered N-octet frames filtered or not filtered
Issues: Issues:
See Also: See Also:
2.22 Maximum broadcast forwarding rate 2.22 Maximum broadcast forwarding rate
Definition: Definition:
The number of broadcast frames per second that a switch can deliver to all The number of broadcast frames per second that a switch can be observed to
ports at maximum load. deliver to all ports at maximum load.
Discussion: Discussion:
There is no standard forwarding mechanism used by switches to forward There is no standard forwarding mechanism used by switches to forward
broadcast frames. It is useful to determine the broadcast forwarding rate broadcast frames. It is useful to determine the broadcast forwarding rate
for frames switched between ports on the same card, ports on different cards 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 in the same chassis and ports on different chassis linked together over
backbone connections. backbone connections.
Measurement units: Measurement units:
N-octet frames per second N-octet frames per second
skipping to change at line 659 skipping to change at line 658
seconds seconds
Issues: Issues:
See Also: See Also:
broadcast forwarding rate (2.20) broadcast forwarding rate (2.20)
3. Index of definitions 3. Index of definitions
2.1 Reminder of RFC 1242 definition format 2.1 Reminder of RFC 1242 definition format
Traffic patterns
2.2 Unidirectional traffic 2.2 Unidirectional traffic
2.3 Bidirectional traffic 2.3 Bidirectional traffic
2.4 Meshed traffic 2.4 Meshed traffic
Bursts
2.5 Burst 2.5 Burst
2.6 Burst size 2.6 Burst size
2.7 Inter-burst gap (IBG) 2.7 Inter-burst gap (IBG)
Port loads
2.8 Port load 2.8 Port load
2.9 Overload 2.9 Offered load
2.10 Intended rate 2.10 Balanced load
2.11 Offered rate 2.11 Maximum load
2.12 Maximum load 2.12 Overload
Forwarding rates
2.13 Forwarding rate 2.13 Forwarding rate
2.14 Forwarding rate at maximum load 2.14 Forwarding rate at maximum load
2.15 Flooding
2.16 Backpressure Congestion control
2.17 Forward pressure 2.15 Backpressure
2.18 Head of line blocking 2.16 Forward pressure
2.19 Address handling 2.17 Head of line blocking
2.20 Address learning rate
Address handling
2.18 Address handling
2.19 Address learning rate
2.20 Flooding
Filtering
2.21 Illegal frames 2.21 Illegal frames
Broadcasts
2.22 Maximum broadcast forwarding rate 2.22 Maximum broadcast forwarding rate
2.23 Broadcast latency 2.23 Broadcast latency
4. Acknowledgments 4. Acknowledgments
In order of appearance Jean-Christophe Bestaux of European Network In order of appearance Jean-Christophe Bestaux of European Network
Laboratories, Ajay Shah of Wandel & Goltermann, Henry Hamon of Netcom Laboratories, Ajay Shah of Wandel & Goltermann, Henry Hamon of Netcom
Systems, Stan Kopek of Digital Equipment Corporation, Kevin Dubray of Bay Systems, Stan Kopek of Digital Equipment Corporation, Kevin Dubray of Bay
Networks, and Doug Ruby of Prominet were all instrumental in getting this Networks, and Doug Ruby of Prominet were all instrumental in getting this
draft done. draft done.
A special thanks goes to the IETF BenchMark WorkGroup for the many A special thanks goes to the IETF BenchMark WorkGroup for the many
suggestions it collectively made to help shape this draft. suggestions it collectively made to help shape this draft.
The editor The editor
Bob Mandeville Bob Mandeville
5. Editor's Address 5. Editor's Address
Robert Mandeville Robert Mandeville, ENL
ENL (European Network Laboratories) European Network Laboratories
35, rue Beaubourg 6 Parc Ariane, le Mercure
75003 Paris Blvd des Chenes
78284 Guyancourt
France France
mobile phone: +33 6 07 47 67 10
phone: +33 1 39 44 12 05
fax: + 33 1 39 44 12 06
email: bob.mandeville@eunet.fr email: bob.mandeville@eunet.fr
Phone/voice mail: +33 1 39 44 12 05
Fax: +33 1 39 44 12 06
Mobile phone: +33 6 07 47 67 10
 End of changes. 

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