draft-ietf-bmwg-mcast-00.txt   draft-ietf-bmwg-mcast-01.txt 
Network Working Group K. Dubray Network Working Group K. Dubray
INTERNET-DRAFT Bay Networks INTERNET-DRAFT Bay Networks
Expiration Date: May 1997 November 1996 Expiration Date: September 1997 March 1997
Terminology for IP Multicast Benchmarking Terminology for IP Multicast Benchmarking
<draft-ietf-bmwg-mcast-00.txt> <draft-ietf-bmwg-mcast-01.txt>
Status of this Memo 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 areas,
and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts. working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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To learn the current status of any Internet-Draft, please check the To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts ``1id-abstracts.txt'' listing contained in the Internet- Drafts
Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast). ftp.isi.edu (US West Coast).
Abstract Abstract
The purpose of this draft is to add terminology specific to the The purpose of this draft is to add terminology specific to the
benchmarking of multicast IP forwarding devices. It builds upon the benchmarking of multicast IP forwarding devices. It builds upon the
tenets set forth in RFC 1242, RFC 1944, and other IETF tenets set forth in RFC 1242, RFC 1944, and other IETF Benchmarking
Benchmark Methodology Working Group (BMWG) effort and extends Methodology Working Group (BMWG) effort and extends them to the
them to the multicast paradigm. multicast paradigm.
[While primarily directed towards intermediate IP multicast
forwarding devices on LANs, elements of this text may or may not be
applicable to other media as well.]
1. Introduction 1. Introduction
Network forwarding devices are being required to take a single Network forwarding devices are being required to take a single
frame and support delivery to a number of destinations having frame and support delivery to a number of destinations having
membership to a particular group. As such, multicast support may membership to a particular group. As such, multicast support may
place a different burden on the resources of these network place a different burden on the resources of these network
forwarding devices than with unicast or broadcast traffic types. forwarding devices than with unicast or broadcast traffic types.
By clearly identifying benchmarks and related terminology in this By clearly identifying benchmarks and related terminology in this
document, it is hoped that detailed methodologies can be generated document, it is hoped that detailed methodologies can be generated
in subsequent documents. Taken in tandem, these two efforts in subsequent documents. Taken in tandem, these two efforts
endeavor to assist the clinical, empirical, and consistent endeavor to assist the clinical, empirical, and consistent
characterization of certain aspects of multicast technologies and characterization of certain aspects of multicast technologies and
their individual implementations. their individual implementations.
[While primarily directed towards intermediate IP multicast
forwarding devices on LANs, elements of this text may or may not be
applicable to other media as well.]
2. Definition Format 2. Definition Format
This section cites the template suggested by RFC 1242 in the This section cites the template suggested by RFC 1242 in the
specification of a term to be defined. specification of a term to be defined.
Term to be defined. Term to be defined.
Definition: Definition:
The specific definition for the term. The specific definition for the term.
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This document draws on existing terminology defined in other This document draws on existing terminology defined in other
BMWG work. Examples include, but are not limited to: BMWG work. Examples include, but are not limited to:
Throughput (RFC 1242, section 3.17) Throughput (RFC 1242, section 3.17)
Latency (RFC 1242, section 3.8) Latency (RFC 1242, section 3.8)
Constant Load (RFC 1242, section 3.4) Constant Load (RFC 1242, section 3.4)
Frame Loss Rate (RFC 1242, section 3.6) Frame Loss Rate (RFC 1242, section 3.6)
Overhead behavior (RFC 1242, section 3.11) Overhead behavior (RFC 1242, section 3.11)
3. Term Definitions 3. Table of Defined Terms
This section will present the terminology to be defined in 3.1 General Nomenclature
this document. 3.1.1 Device Under Test (DUT).
3.1.2 System Under Test (SUT).
3.1.3 Target Rate.
3.1.4 Offered Rate.
3.1.5 Forwarding Rate.
3.1.6 Maximum Forwarding Rate (MFR).
3.1.7 Flow.
3.1.8 Group Flow.
3.1.9 Service Flow.
3.1 Device Under Test (DUT). 3.2 Throughput
3.2.1 Mixed Flow Throughput (MFT).
3.2.2 Scaled Group Throughput (SGT).
3.2.3 Aggregated Multicast Throughput (AMT)
3.2.4 Translational Throughput (TT)
3.3 Fairness
3.4 Forwarding Latency
3.4.1 Multicast Latency
3.4.2 Min/Max Multicast Latency
3.5 Overhead
3.5.1 Group Join Delay.
3.5.2 Group Leave Delay.
3.6 Capacity
3.6.1 Multicast Group Capacity.
3.1 General Nomenclature
This section will present general terminology to be used in
this and other documents.
3.1.1 Device Under Test (DUT).
Definition: Definition:
The network forwarding device being tested. The network forwarding device being tested.
Discussion: Discussion:
Measurement units: Measurement units:
Not applicable. Not applicable.
3.2 System Under Test (SUT). Issue:
This definition is being moved to the BMWG LAN switch
terminology draft. This item will be deleted from this
multicast terminology draft upon migration.
3.1.2 System Under Test (SUT).
Definition: Definition:
The collective set of network devices being tested as a singular The collective set of network devices being tested as a singular
entity. entity.
Discussion: A system under test may be comprised of a variety Discussion: A system under test may be comprised of a variety
of networking devices. Some devices may be active in the of networking devices. Some devices may be active in the
forwarding decision making process, such as routers or switches; forwarding decision making process, such as routers or switches;
other devices may be passive such as CSU/DSUs. Regardless other devices may be passive such as CSU/DSUs. Regardless
of constituent components, the system is treated as a "black box" of constituent components, the system is treated as a "black box"
to which stimuli is offered and response measured. to which stimuli is offered and response measured.
Measurement units: Measurement units:
Not applicable. Not applicable.
3.3 Target Rate. Issue:
This definition is being moved to the BMWG LAN switch
terminology draft. This item will be deleted from this
multicast terminology draft upon migration.
3.1.3 Target Rate.
Definition: Definition:
The requested rate at which the test device attempts to offer the The requested rate at which the test device attempts to offer the
DUT or SUT test traffic. DUT or SUT test traffic.
Discussion: Discussion:
There are networks events (e.g., collisions) that may preclude the There are networks events (e.g., collisions) that may preclude the
test device from delivering the requested rate to the SUT. In this test device from delivering the requested rate to the SUT. In this
case, differentiation is made between target rate and offered rate. case, differentiation is made between target rate and offered rate.
[May need to be reconciled with terminology of BMWG works-in-
progress.]
Measurement units: Measurement units:
Frames per second. Frames per second.
3.4 Offered Rate. Issue:
This definition is being moved to the BMWG LAN switch
terminology draft as "intended rate". This item will be deleted
multicast terminology draft upon migration.
3.1.4 Offered Rate.
Definition: Definition:
The actual resultant rate at which the test device is successful The actual resultant rate at which the test device is successful
in offering test traffic to the SUT. in offering test traffic to the SUT.
Discussion: Discussion:
Contrast with Target Rate. Note relationship to Forwarding Rate. Contrast with Target Rate. Note relationship to Forwarding Rate.
[May need to be reconciled with terminology of BMWG works-in-
progress.]
Measurement units: Measurement units:
Frames per second. Frames per second.
3.5 Forwarding Rate. Issue:
This definition is being moved to the BMWG LAN switch
terminology draft. This item will be deleted from this
multicast terminology draft upon migration.
3.1.5 Forwarding Rate.
Definition: Definition:
The rate at which the SUT has been observed to successfully The rate at which the SUT has been observed to successfully
forward test traffic to the traffic's correct destination(s) in forward test traffic to the traffic's correct destination(s) in
response to a particular offered rate. response to a particular offered rate.
Discussion: Discussion:
Note the specification of "correct destination(s)" in the Note the specification of "correct destination(s)" in the
definition. The reporting of a forwarding rate MUST definition. The reporting of a forwarding rate MUST
correspond to an associated Offered Rate. Frame loss is not correspond to an associated Offered Rate. Frame loss is not
a constraint when reporting Forwarding Rate. a constraint when reporting Forwarding Rate.
[May need to be reconciled with terminology of BMWG works-in-
progress.]
Measurement units: Measurement units:
Frames per second. Frames per second.
3.6 Maximum Forwarding Rate (MFR). Issue:
This definition is being moved to the BMWG LAN switch
terminology draft. This item will be deleted from this
multicast terminology draft upon migration.
3.1.6 Maximum Forwarding Rate (MFR).
Definition: Definition:
The rate at which the SUT has been observed to successfully The rate at which the SUT has been observed to successfully
forward test traffic to the traffic's correct destination(s) in forward test traffic to the traffic's correct destination(s) in
response to the test device's maximum offered rate. response to the test device's maximum offered rate.
Discussion: Discussion:
Because a DUT's maximum forwarding rate does not always equal Because a DUT's maximum forwarding rate does not always equal
the largest forwarding rate of the DUT, this metric can sometimes the largest forwarding rate of the DUT, this metric can sometimes
indicate oversubscription or congestion internal to the DUT/SUT. indicate oversubscription or congestion internal to the DUT/SUT.
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When reporting the MFR, the corresponding test device's maximum When reporting the MFR, the corresponding test device's maximum
offered load MUST be cited. This is due to the fact that not offered load MUST be cited. This is due to the fact that not
all test devices deliver the maximum usable bandwidth. In the all test devices deliver the maximum usable bandwidth. In the
case when the test device is able to exceed the maximum, legal case when the test device is able to exceed the maximum, legal
bandwidth, the test results SHOULD reflect that the test was bandwidth, the test results SHOULD reflect that the test was
conducted in a overload condition. conducted in a overload condition.
Measurement units: Measurement units:
Frames per second. Frames per second.
3.7 Flow. Issue:
This definition is being moved to the BMWG LAN switch
terminology draft as "Forwarding Rate at Maximum Offered Load."
This item will be deleted from this multicast terminology draft
upon migration.
3.1.7 Flow.
Definition: Definition:
An equivalence class of packets comprising one or more data An equivalence class of packets comprising one or more data
streams. streams.
Discussion: Discussion:
In the scope of this document, Flow will be considered a logical In the scope of this document, Flow will be considered a logical
identifier used to discriminate between a set or sets of packets identifier used to discriminate between a set or sets of packets
offered the DUT. offered the DUT.
For example, one flow may identify a set of unicast packets For example, one flow may identify a set of unicast packets
offered to the DUT. Another flow may differentiate the offered to the DUT. Another flow may differentiate the
multicast packets destined to multicast group X. Yet another multicast packets destined to multicast group X. Yet another
flow may distinguish the set of multicast packets destined to flow may distinguish the set of multicast packets destined to
multicast group Y. multicast group Y.
Measurement units: Measurement units:
Not applicable. Not applicable.
3.8 Group Flow. Issue: This definition does not seem to be inconsistent with
section 1.2 of the RSVP draft, but may not map directly to
work being done in the RTFM space.
3.1.8 Group Flow.
Definition: Definition:
A specific type of flow where the packets comprising the flow A specific type of flow where the packets comprising the flow
are destined to a particular multicast group. are destined to a particular multicast group.
Discussion: Discussion:
Measurement units: Measurement units:
Not applicable. Not applicable.
3.9 Service Flow. 3.1.9 Service Flow.
Definition: Definition:
A specific type of flow where the packets comprising the flow A specific type of flow where the packets comprising the flow
require particular treatment or treatments by the network require particular treatment or treatments by the network
forwarding devices along the path to the packets' destination(s). forwarding devices along the path to the packets' destination(s).
Discussion: Discussion:
Measurement units: Measurement units:
Not applicable. Not applicable.
3.10 Mixed Throughput (MT). 3.2 Throughput.
This section presents terminology relating to the characterization of
the packet forwarding ability of a DUT/SUT in a multicast environment.
It extends the concept of throughput presented in RFC 1242.
3.2.1 Mixed Flow Throughput (MFT).
Definition: Definition:
The maximum rate at which none of the offered frames, comprised The maximum rate at which none of the offered frames, comprised
from a unicast flow and a multicast flow, to be forwarded are from a unicast flow and a multicast flow, to be forwarded are
dropped by the device. dropped by the device.
Discussion: Discussion:
Often times, throughput is collected on a homogenous traffic Often times, throughput is collected on a homogenous traffic
type - though the packets' destinations may vary, the packets type - though the packets' destinations may vary, the packets
follow the same packet forwarding path through the DUT. follow the same packet forwarding path through the DUT.
Based on the RFC 1242 definition for throughput, the Mixed Based on the RFC 1242 definition for throughput, the Mixed
Thoughput benchmark attempts to characterize the DUT's Flow Throughput benchmark attempts to characterize the DUT's
ability to process both unicast and multicast frames in the ability to process both unicast and multicast frames in the
same aggregated traffic stream. same aggregated traffic stream.
Measurement units: Measurement units:
Frames per second Frames per second
3.11 Scaled Group Throughput (SGT). Issues:
Related methodology may have to address the ratio of unicast packets
to multicast packets.
3.2.2 Scaled Group Throughput (SGT).
Definition: Definition:
The maximum number of multicast groups that a DUT/SUT can The maximum number of multicast groups that a DUT/SUT can
support and still yield the same throughput as supporting a support and still yield the same throughput as supporting a
single multicast group. single multicast group.
Discussion: Discussion:
A desirable attribute of many Internet mechanisms is the ability A desirable attribute of many Internet mechanisms is the ability
to "scale." This benchmark seeks to demonstrate the ability to "scale." This benchmark seeks to demonstrate the ability
of a SUT to scale the number of multicast groups upwards while of a SUT to scale the number of multicast groups upwards while
holding it to the RFC 1242 definition of throughput for a single holding it to the RFC 1242 definition of throughput for a single
multicast group. multicast group.
Measurement units: Measurement units:
Number of multicast groups. Number of multicast groups.
3.12 Extraction Throughput (ET) Issues:
The corresponding methodology (or even the definition itself) may
have to reflect the impact that the pairing (source, group) has on
many multicast routing protocols.
3.2.3 Aggregated Multicast Throughput (AMT)
Definition:
The maximum rate at which none of the offered frames to be
forwarded through N destination interfaces of the same multicast
group are dropped.
Discussion:
Another "scaling" type of exercise, designed to identify the
DUT/SUT's ability to handle traffic as a function of the
multicast destination ports it is required to support.
Measurement units:
The ordered pair (N,t) where,
N = the number of destination ports of the multicast group.
t = the throughput, in frames per second, relative to the
source stream.
3.2.4 Translational Throughput (TT)
Definition: Definition:
The maximum rate at which none of the frames offered in an The maximum rate at which none of the frames offered in an
transitional format to the SUT are dropped in the process of transitional format to the SUT are dropped in the process of
converting those frames to their appropriate, final format and converting those frames to their appropriate, final format and
subsequent correct delivery. subsequent correct delivery.
Discussion: Discussion:
A popular technique in presenting frames to devices that may A popular technique in presenting frames to devices that may
not support a protocol feature is to encapsulate, or tunnel, not support a protocol feature is to encapsulate, or tunnel,
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is supported by that device. This benchmark attempts to is supported by that device. This benchmark attempts to
characterize the overhead behavior associated with that characterize the overhead behavior associated with that
transitional process. transitional process.
Consideration may need to be given with respect to the impact Consideration may need to be given with respect to the impact
of different frame formats on usable bandwidth. of different frame formats on usable bandwidth.
Measurement units: Measurement units:
Frames per second. Frames per second.
3.13 Fairness. 3.3 Fairness.
Definition: Definition:
The ability of a SUT to fulfill the requirements of a flow The ability of a SUT to fulfill the requirements of a flow
without compromising the requirements, if any, of other flows. without compromising the requirements, if any, of other flows.
Discussion: Discussion:
Measurement units: Measurement units:
Not applicable. Not applicable.
3.14 Multicast Latency. 3.4 Forwarding Latency.
This section presents terminology relating to the characterization of
the forwarding latency of a DUT/SUT in a multicast environment.
It extends the concept of latency presented in RFC 1242.
3.4.1 Multicast Latency.
Definition: Definition:
The set of individual latencies from a single input port on The set of individual latencies from a single input port on
the DUT or SUT to all tested ports belonging to the destination the DUT or SUT to all tested ports belonging to the destination
multicast group. multicast group.
Discussion: Discussion:
This benchmark is based on the RFC 1242 definition of latency. This benchmark is based on the RFC 1242 definition of latency.
While it is useful to collect latency between a pair of source While it is useful to collect latency between a pair of source
and destination multicast ports, it may be insightful to collect and destination multicast ports, it may be insightful to collect
the same type of measurements across a range of ports supporting the same type of measurements across a range of ports supporting
that group flow. that group flow.
A variety of statistical exercises can be applied to the set of A variety of statistical exercises can be applied to the set of
latencies measurements. latencies measurements.
Measurement units: Measurement units:
Time units with enough precision to reflect measurement. Time units with enough precision to reflect measurement.
3.15 Min/Max Latency. 3.4.2 Min/Max Multicast Latency.
Definition: Definition:
The difference between the maximum latency measurement and the The difference between the maximum latency measurement and the
minimum latency measurement from the set of latencies produced by minimum latency measurement from the set of latencies produced by
the Multicast Latency benchmark. the Multicast Latency benchmark.
Discussion: Discussion:
This statistic may yield some insight into how a particular This statistic may yield some insight into how a particular
implementation handles its multicast traffic. This may be useful implementation handles its multicast traffic. This may be useful
to users of multicast synchronization types of applications. to users of multicast synchronization types of applications.
Measurement units: Measurement units:
Time units with enough precision to reflect measurement. Time units with enough precision to reflect measurement.
3.16 Prune Delay. 3.5 Overhead
Definition:
The time duration it takes a DUT/SUT to cease forwarding multicast
packets after a corresponding "prune" or similar event has been
successfully generated.
Discussion:
While it is important to understand how quickly a system can
process multicast frames; it may be beneficial to understand
how quickly that same system can stop the process as well.
Measurement units: This section presents terminology relating to the characterization of
Microseconds. the overhead delays associated with explicit operations found in
multicast environments.
3.16 Group Membership Delay. 3.5.1 Group Join Delay.
Definition: Definition:
The time duration it takes a DUT/SUT to start forwarding multicast The time duration it takes a DUT/SUT to start forwarding multicast
packets from the time a successful IGMP group membership report has packets from the time a successful IGMP group membership report has
been generated. been issued to the DUT/SUT.
Discussion: Discussion:
Many different factors can contribute to different results, such as Many different factors can contribute to different results, such as
the number or type of multicast-related protocols configured the number or type of multicast-related protocols configured
on the system under test. on the system under test.
A consideration for the related methodology: possible need to A consideration for the related methodology: possible need to
differentiate a specifically-forwarded multicast frame from those differentiate a specifically-forwarded multicast frame from those
sprayed by protocols implementing a flooding tactic to solicit prune sprayed by protocols implementing a flooding tactic to solicit prune
feedback. feedback.
Measurement units: Measurement units:
Microseconds. Microseconds.
3.17 Multicast Group Capacity. 3.5.2 Group Leave Delay.
Definition: Definition:
The maximum number of multicast groups a SUT/DUT can support The time duration it takes a DUT/SUT to cease forwarding multicast
while maintaining the ability to forward multicast frames packets after a corresponding IGMP "Leave Group" message has been
to all multicast groups registered to that SUT/DUT. successfully offered to the DUT/SUT.
Discussion: Discussion:
While it is important to understand how quickly a system can
process multicast frames; it may be beneficial to understand
how quickly that same system can stop the process as well.
Measurement units: Measurement units:
Multicast groups. Microseconds.
3.18 Aggregated Multicast Throughput (AMT) Issues: Methodology may need to consider protocol-specific timeout
values.
3.6 Capacity
This section offers terms relating to the identification of multicast
group limits of a DUT/SUT.
3.6.1 Multicast Group Capacity.
Definition: Definition:
The maximum rate at which none of the offered frames to be The maximum number of multicast groups a SUT/DUT can support
forwarded through N destination interfaces of the same multicast while maintaining the ability to forward multicast frames
group are dropped. to all multicast groups registered to that SUT/DUT.
Discussion: Discussion:
Another "scaling" type of exercise, designed to identify the
DUT/SUT's ability to handle traffic as a function of the
multicast destination ports it is required to support.
Measurement units: Measurement units:
The ordered pair (N,t) where, Multicast groups.
N = the number of destination ports of the multicast group. Issues:
t = the throughput, in frames per second, relative to the The related methodology may have to consider the impact of multicast
source stream. sources per group on the ability of a SUT/DUT to "scale up" the
number of supportable multicast groups.
4. Security Considerations 4. Security Considerations
Security issues are not addressed in this memo. Security issues are not addressed in this memo.
5. References 5. References
[1] Bradner, S. Benchmarking Terminology for Network [1] Bradner, S. Benchmarking Terminology for Network
Interconnection Devices. RFC 1242. July, 1991. Interconnection Devices. RFC 1242. July, 1991.
[2] Bradner, S., McQuaid, J. Benchmarking Methodology for Network [2] Bradner, S., McQuaid, J. Benchmarking Methodology for Network
Interconnect Devices. RFC 1944. May, 1996. Interconnect Devices. RFC 1944. May, 1996.
[3] Craig, R. Terminology for Cell/Call Benchmarking. <draft-ietf- [3] Craig, R. Terminology for Cell/Call Benchmarking. <draft-ietf-
bmwg-call-00.txt> November, 1996. Work in progress. bmwg-call-00.txt> November, 1996. Work in progress.
[4] Mandeville, R. Benchmarking Terminology for LAN Switching [4] Mandeville, R. Benchmarking Terminology for LAN Switching
Devices. <draft-ietf-bmwg-lanswitch-01.txt> November, 1996. Devices. <draft-ietf-bmwg-lanswitch-03.txt> February, 1997.
Work in progress. Work in progress.
5. Author's Address 5. Author's Address
Kevin Dubray Kevin Dubray
Bay Networks, Inc. Bay Networks, Inc.
2 Federal Street 2 Federal Street
Billerica, MA 01984 Billerica, MA 01984
(508) 436-3862 (508) 436-3862
kdubray@baynetworks.com kdubray@baynetworks.com
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