Network Working Group Debra Stopp
Hardev Soor
INTERNET-DRAFT IXIA
Expires in: March 2003
Methodology for IP Multicast Benchmarking
<draft-ietf-bmwg-mcastm-10.txt>
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
The purpose of this draft is to describe methodology specific to
the benchmarking of multicast IP forwarding devices. It builds upon
the tenets set forth in RFC 2544, RFC 2432 and other IETF
Benchmarking Methodology Working Group (BMWG) efforts. This
document seeks to extend these efforts to the multicast paradigm.
The BMWG produces two major classes of documents: Benchmarking
Terminology documents and Benchmarking Methodology documents. The
Terminology documents present the benchmarks and other related
terms. The Methodology documents define the procedures required to
collect the benchmarks cited in the corresponding Terminology
documents.
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Table of Contents
1. INTRODUCTION...................................................3
2. KEY WORDS TO REFLECT REQUIREMENTS..............................3
3. TEST SET UP....................................................3
3.1. Test Considerations..........................................5
3.1.1. IGMP Support..............................................5
3.1.2. Group Addresses...........................................5
3.1.3. Frame Sizes...............................................6
3.1.4. TTL.......................................................6
3.1.5. Trial Duration............................................6
3.2. Layer 2 Support..............................................6
4. FORWARDING AND THROUGHPUT......................................6
4.1. Mixed Class Throughput.......................................6
4.2. Scaled Group Forwarding Matrix...............................8
4.3. Aggregated Multicast Throughput..............................8
4.4. Encapsulation/Decapsulation (Tunneling) Throughput...........9
4.4.1. Encapsulation Throughput..................................9
4.4.2. Decapsulation Throughput.................................10
4.4.3. Re-encapsulation Throughput..............................11
5. FORWARDING LATENCY............................................12
5.1. Multicast Latency...........................................12
5.2. Min/Max Multicast Latency...................................15
6. OVERHEAD......................................................16
6.1. Group Join Delay............................................16
6.2. Group Leave Delay...........................................16
7. CAPACITY......................................................17
7.1. Multicast Group Capacity....................................17
8. INTERACTION...................................................18
8.1. Forwarding Burdened Multicast Latency.......................18
8.2. Forwarding Burdened Group Join Delay........................19
9. SECURITY CONSIDERATIONS.......................................20
10. ACKNOWLEDGEMENTS.............................................20
11. REFERENCES...................................................21
12. AUTHOR'S ADDRESSES...........................................22
13. FULL COPYRIGHT STATEMENT.....................................22
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1. Introduction
This document defines a specific set of tests that vendors can use
to measure and report the performance characteristics and
forwarding capabilities of network devices that support IP
multicast protocols. The results of these tests will provide the
user comparable data from different vendors with which to evaluate
these devices.
A previous document, " Terminology for IP Multicast Benchmarking"
(RFC 2432), defined many of the terms that are used in this
document. The terminology document should be consulted before
attempting to make use of this document.
This methodology will focus on one source to many destinations,
although many of the tests described may be extended to use
multiple source to multiple destination IP multicast communication.
2. Key Words to Reflect Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
in this document are to be interpreted as described in RFC 2119.
RFC 2119 defines the use of these key words to help make the intent
of standards track documents as clear as possible. While this
document uses these keywords, this document is not a standards
track document.
3. Test set up
The set of methodologies presented in this draft are for single
ingress, multiple egress scenarios as exemplified by Figures 1 and
2. Methodologies for multiple ingress, multiple egress scenarios
are beyond the scope of this document.
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Figure 1 shows a typical setup for an IP multicast test, with one
source to multiple destinations.
+----------------+
+------------+ | Egress |
+--------+ | (-)-------->| destination(E1)|
| | | | | |
| source |------->(|)Ingress | +----------------+
| | | | +----------------+
+--------+ | D U T (-)-------->| Egress |
| | | destination(E2)|
| | | |
| | +----------------+
| | . . .
| | +----------------+
| | | Egress |
| (-)-------->| destination(En)|
| | | |
+------------+ +----------------+
Figure 1
---------
If the multicast metrics are to be taken across multiple devices
forming a System Under Test (SUT), then test packets are offered to
a single ingress interface on a device of the SUT, subsequently
routed across the SUT topology, and finally forwarded to the test
apparatus' packet-receiving components by the test egress
interface(s) of devices in the SUT. Figure 2 offers an example SUT
test topology. If a SUT is tested, the details of the test
topology MUST be disclosed with the corresponding test results.
+--------+ +----------------+ +--------+
| | +------------+ |DUT B Egress E0(-)-->| |
| | |DUT A |--->| | | |
| Test | | | | Egress E1(-)-->| Test |
| App. |--->(-)Ingress, I | +----------------+ | App. |
| Traffic| | | +----------------+ | Traffic|
| Src. | | |--->|DUT C Egress E2(-)-->| Dest. |
| | +------------+ | | | |
| | | Egress En(-)-->| |
+--------+ +----------------+ +--------+
Figure 2
---------
Generally, the destination ports first join the desired number of
multicast groups by sending IGMP Join Group messages to the
DUT/SUT. To verify that all destination ports successfully joined
the appropriate groups, the source port MUST transmit IP multicast
frames destined for these groups. The destination ports MAY send
IGMP Leave Group messages after the transmission of IP Multicast
frames to clear the IGMP table of the DUT/SUT.
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In addition, test equipment MUST validate the correct and proper
forwarding actions of the devices they test in order to ensure the
receipt of only the frames that are involved in the test.
3.1. Test Considerations
The procedures outlined below are written without regard for
specific physical layer or link layer protocols. The methodology
further assumes a uniform medium topology. Issues regarding mixed
transmission media, such as speed mismatch, headers differences,
etc., are not specifically addressed. Flow control, QoS and other
traffic-affecting mechanisms MUST be disabled. Modifications to
the specified collection procedures might need to be made to
accommodate the transmission media actually tested. These
accommodations MUST be presented with the test results.
An actual flow of test traffic may be required to prime related
mechanisms, (e.g., process RPF events, build device caches, etc.)
to optimally forward subsequent traffic. Therefore, before an
initial, measured forwarding test trial, the test apparatus MUST
generate test traffic utilizing the same addressing characteristics
to the DUT/SUT that will subsequently be used to measure the
DUT/SUT response. The test monitor should ensure the correct
forwarding of traffic by the DUT/SUT. The priming action need only
be repeated to keep the associated information current.
3.1.1. IGMP Support
Each of the destination ports should support and be able to test
all IGMP versions 1, 2 and 3. The minimum requirement, however, is
IGMP version 2.
Each destination port should be able to respond to IGMP queries
during the test.
Each destination port should also send LEAVE (running IGMP version
2) after each test.
3.1.2. Group Addresses
It is intended that the collection of benchmarks prescribed in
this document be executed in an isolated lab environment. That
is to say, the test traffic offered the tested devices MUST NOT
traverse a live internet, intranet, or other user-oriented network.
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Assuming the above, there is no restriction to the use of multicast
addresses to compose the test traffic other than those assignments
imposed by IANA. The IANA assignments MUST be regarded for
operational consistency. For multicast address assignments see:
http://www.iana.org/assignments/multicast-addresses
It should be noted that address selection need not be restricted to
Administratively Scoped IP Multicast addresses.
3.1.3. Frame Sizes
Each test SHOULD be run with different Multicast Frame Sizes. The
recommended frame sizes are 64, 128, 256, 512, 1024, 1280, and 1518
byte frames.
3.1.4. TTL
The source frames should have a TTL value large enough to
accommodate the DUT/SUT.
3.1.5. Trial Duration
The duration of the test portion of each trial SHOULD be at least
30 seconds. This parameter MUST be included as part of the results
reporting for each methodology.
3.2. Layer 2 Support
Each of the destination ports should support GARP/GMRP protocols to
join groups on Layer 2 DUTs/SUTs.
4. Forwarding and Throughput
This section contains the description of the tests that are related
to the characterization of the packet forwarding of a DUT/SUT in a
multicast environment. Some metrics extend the concept of throughput
presented in RFC 1242. The notion of Forwarding Rate is cited in RFC
2285.
4.1. Mixed Class Throughput
Objective
To determine the throughput of a DUT/SUT when both unicast class
frames and multicast class frames are offered simultaneously to a
fixed number of ports as defined in RFC 2432.
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Procedure
Multicast and unicast traffic are mixed together in the same
aggregated traffic stream in order to simulate the non-homogenous
networking environment. The DUT/SUT MUST learn the appropriate
unicast IP addresses, either by sending ARP frames from each
unicast address, sending a RIP packet or by assigning static
entries into the DUT/SUT address table.
The relationship between the intended load [Ma91] of multicast
class frames vs. unicast class frames MUST be specified:
a) As an independent rate for unicast class and multicast
class of traffic OR
b) As an aggregate rate comprised of a ratio of multicast
class to unicast class of traffic.
The offered load per each DUT/SUT port MUST not exceed the maximum
bandwidth capacity of any configured receive DUT/SUT ports.
All DUT/SUT ports configured to receive multicast traffic MUST join
all configured multicast groups prior to transmitting test frames.
Joining a group is accomplished by sending an IGMP Join Group
messages. All DUT/SUT ports configured to receive unicast traffic
MUST send learning frames prior to transmitting test frames (see
section 3 for more information).
Unicast traffic distribution can either be non-meshed or meshed
[Ma98] as specified in RFC2544 or RFC2289. A minimum of one
unicast transmit port MUST be configured to transmit unicast
traffic to a DUT/SUT port that is configured to receive unicast and
multicast traffic.
Multicast traffic distribution MUST be configured to transmit
traffic in a one-to-many mesh [Ma98] configuration. A minimum of
one multicast transmit port MUST be configured to transmit
multicast traffic to a DUT/SUT port that is configured to receive
multicast traffic.
Throughput measurement is defined in RFC1242 [Br91]. A search
algorithm MUST be utilized to determine the maximum offered frame
rate with a zero frame loss rate.
Result
Parameters to be measured MUST include the aggregate offered load,
number of multicast frames offered, number of unicast frames
offered, number of multicast frames received, number of unicast
frames received and transmit duration of offered frames.
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4.2. Scaled Group Forwarding Matrix
Objective
To determine Forwarding Rate as a function of tested multicast
groups for a fixed number of tested DUT/SUT ports.
Procedure
Multicast traffic is sent at a fixed percent of maximum offered
load with a fixed number of receive ports of the tester at a fixed
frame length.
On each iteration, the receive ports SHOULD incrementally join 10
multicast groups until a user defined maximum number of groups is
reached.
Results
Parameters to be measured MUST include the offered load and
forwarding rate as a function of the total number of multicast
groups, for each test iteration.
The nature of the traffic stream contributing to the result MUST be
reported, specifically number of source and destination ports
within the multicast group. In addition, all other reporting
parameters of the scaled group forwarding matrix methodology MUST
be reflected in the results report, such as the transmitted packet
size(s) and offered load of the packet stream for each source port.
Result reports MUST include the following parameters for each
iteration: the number of frames offered, number of frames received
per each group, number of multicast groups and forwarding rate, in
frames per second, and transmit duration of offered frames.
Constructing a table that contains the forwarding rate vs. number
of groups is desirable.
4.3. Aggregated Multicast Throughput
Objective
To determine the maximum rate at which none of the offered frames
to be forwarded through N destination interfaces of the same
multicast group is dropped.
Procedure
Multicast traffic is sent at a fixed percent of maximum offered
load with a fixed number of groups at a fixed frame length for a
fixed duration of time.
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The initial number of receive ports of the tester will join the
group(s) and the sender will transmit to the same groups after a
certain delay (a few seconds).
If any frame loss is detected, one receive port MUST leave the
group(s) and the sender will transmit again. Continue in this
iterative fashion until either there are no ports left joined to
the multicast group(s) OR 0% frame loss is achieved.
Results
Parameters to be measured MUST include the maximum offered load at
which no frame loss occurred (as defined by RFC 2544)
The nature of the traffic stream contributing to the result MUST be
reported. All required reporting parameters of aggregated
throughput MUST be reflected in the results report, such as the
initial number of receive ports, the final number of receive ports,
total number of multicast group addresses, the transmitted packet
size(s), offered load of the packet stream and transmit duration of
offered frames.
Constructing a table from the measurements might be useful in
illustrating the effect of modifying the number of active egress
ports on the tested system.
4.4. Encapsulation/Decapsulation (Tunneling) Throughput
This sub-section provides the description of tests that help in
obtaining throughput measurements when a DUT/SUT or a set of DUTs
are acting as tunnel endpoints.
4.4.1. Encapsulation Throughput
Objective
To determine the maximum rate at which frames offered a DUT/SUT are
encapsulated and correctly forwarded by the DUT/SUT without loss.
Procedure
Traffic is offered to the ingress interface of a DUT/SUT <Figure 1>
that has been configured to encapsulate the frames and received on
a test port prior to decapsulation at the egress interface.
The DUT/SUT SHOULD be configured such that the constitution of
traffic will consist of either:
a) A single tunnel encapsulating one or more multicast address
groups OR
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b) Multiple tunnels, each encapsulating one or more multicast
address groups.
Each tunnel created by the ingress DUT/SUT SHOULD contain the same
number of multicast address groups per tunnel interface.
The offered load on the ingress port MUST not oversubscribe the
outbound link of the DUT/SUT with respect to the benchmarked
throughput at the encapsulated frame size.
Results
Based on the resulting encapsulated frame size, parameters to be
measured MUST include the maximum offered load at which no frame
loss occurred, the number of encapsulated multicast frames offered
per tunnel interface, and the number of encapsulated multicast
frames received per tunnel interface.
The nature of the traffic stream contributing to the result MUST be
reported. All required reporting parameters of multicast
encapsulation throughput MUST be reflected in the results report,
such as the encapsulation format, transmitted packet size(s),
encapsulated frame size, and transmit duration of offered frames.
4.4.2. Decapsulation Throughput
Objective
To determine the maximum rate at which frames offered a DUT/SUT are
decapsulated and correctly forwarded by the DUT/SUT without loss.
Procedure
Encapsulated traffic is offered to the egress interface of a
DUT/SUT <Figure 1> that has been configured to decapsulate the
frames.
The constitution of traffic SHOULD consist of either:
a) A single tunnel encapsulating one or more multicast address
groups OR
b) Multiple tunnels, each encapsulating one or more multicast
address groups.
Due to the nature of decapsulation, the offered load on the
encapsulated egress port will be less than the offered load on the
decapsulated egress interface.
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Results
Based on the resulting decapsulated frame size, parameters to be
measured MUST include the maximum offered load at which no frame
loss occurred, the number of encapsulated multicast frames offered
per tunnel interface, and the number of multicast frames received
after decapsulation.
The nature of the traffic stream contributing to the result MUST be
reported. All required reporting parameters of multicast
decapsulation throughput MUST be reflected in the results report,
such as the transmitted packet size(s), decapsulated frame size,
and transmit duration of offered frames.
4.4.3. Re-encapsulation Throughput
Objective
To determine the maximum rate at which frames of one encapsulated
format offered a DUT/SUT are converted to another encapsulated
format and correctly forwarded by the DUT/SUT without loss.
Procedure
Encapsulated traffic of one type is offered to the egress interface
of a DUT/SUT <Figure 1> that has been configured to re-encapsulate
the frames using a different encapsulation format.
The DUT/SUT SHOULD be configured such that the constitution of
traffic will consist of either:
c) A single tunnel encapsulating one or more multicast address
groups OR
d) Multiple tunnels, each encapsulating one or more multicast
address groups.
Each tunnel created by the ingress DUT/SUT SHOULD contain the same
number of multicast address groups per tunnel interface.
The offered load on the ingress port MUST not oversubscribe the
outbound link with respect to the offered load at the higher end of
the DUT/SUTÆs capacity based on the encapsulated frame size.
Results
Based on the resulting encapsulated frame size, parameters to be
measured MUST include the maximum offered load at which no frame
loss occurred, the number of encapsulated multicast frames offered
per tunnel interface, and the number of encapsulated multicast
frames received per tunnel interface.
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The nature of the traffic stream contributing to the result MUST be
reported. All required reporting parameters of multicast
encapsulation throughput MUST be reflected in the results report,
such as the encapsulation format on the egress interface,
transmitted packet size(s), encapsulated frame size, and transmit
duration of offered frames.
5. Forwarding Latency
This section presents methodologies relating to the
characterization of the forwarding latency of a DUT/SUT in a
multicast environment. It extends the concept of latency
characterization presented in RFC 2544.
In order to lessen the effect of packet buffering in the DUT/SUT,
the latency tests MUST be run at the measured multicast throughput
level of the DUT; multicast latency at other offered loads is
optional.
Lastly, RFC 1242 and RFC 2544 draw distinction between two classes
of devices: "store and forward" and "bit-forwarding." Each class
impacts how latency is collected and subsequently presented. See
the related RFCs for more information. In practice, much of the
test equipment will collect the latency measurement for one class
or the other, and, if needed, mathematically derive the reported
value by the addition or subtraction of values accounting for
medium propagation delay of the packet, bit times to the timestamp
trigger within the packet, etc. Test equipment vendors SHOULD
provide documentation regarding the composition and calculation
latency values being reported. The user of this data SHOULD
understand the nature of the latency values being reported,
especially when comparing results collected from multiple test
vendors. (E.g., If test vendor A presents a "store and forward"
latency result and test vendor B presents a "bit-forwarding"
latency result, the user may erroneously conclude the DUT has two
differing sets of latency values.)
5.1. Multicast Latency
Objective
To produce a set of multicast latency measurements from a single,
multicast ingress port of a DUT/SUT through multiple, egress
multicast ports of that same DUT/SUT as provided for by the metric
"Multicast Latency" in RFC 2432.
The procedures highlighted below attempt to draw from the
collection methodology for latency in RFC 2544 to the degree
possible. The methodology addresses two topological scenarios: one
for a single device (DUT) characterization; a second scenario is
presented or multiple device (SUT) characterization.
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Procedure
If the test trial is to characterize latency across a single Device
Under Test (DUT), an example test topology might take the form of
Figure 1 in section 3. That is, a single DUT with one ingress
interface receiving the multicast test traffic from packet-
transmitting component of the test apparatus and n egress
interfaces on the same DUT forwarding the multicast test traffic
back to the packet-receiving component of the test apparatus. Note
that n reflects the number of TESTED egress interfaces on the DUT
actually expected to forward the test traffic (as opposed to
configured but untested, non-forwarding interfaces, for example).
If the multicast latencies are to be taken across multiple devices
forming a System Under Test (SUT), an example test topology might
take the form of Figure 2 in section 3.
The trial duration SHOULD be 120 seconds. Departures to the
suggested traffic class guidelines MUST be disclosed with the
respective trial results. The nature of the latency measurement,
"store and forward" or "bit forwarding," MUST be associated with
the related test trial(s) and disclosed in the results report.
End-to-end reach ability of the test traffic path MUST be verified
prior to the engagement of a test trial. This implies that
subsequent measurements are intended to characterize the latency
across the tested device's or devices' normal traffic forwarding
path (e.g., faster hardware-based engines) of the device(s) as
opposed a non-standard traffic processing path (e.g. slower,
software-based exception handlers). If the test trial is to be
executed with the intent of characterizing a non-optimal,
forwarding condition, then a description of the exception
processing conditions being characterized MUST be included with the
trial's results.
A test traffic stream is presented to the DUT. At the mid-point of
the trial's duration, the test apparatus MUST inject a uniquely
identifiable ("tagged") packet into the test traffic packets being
presented. This tagged packet will be the basis for the latency
measurements. By "uniquely identifiable," it is meant that the test
apparatus MUST be able to discern the "tagged" packet from the
other packets comprising the test traffic set. A packet generation
timestamp, Timestamp A, reflecting the completion of the
transmission of the tagged packet by the test apparatus, MUST be
determined.
The test apparatus then monitors packets from the DUT's tested
egress port(s) for the expected tagged packet(s) until the
cessation of traffic generation at the end of the configured trial
duration.A value of the Offered Load presented the DUT/SUT MUST be
noted.
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The test apparatus MUST record the time of the successful detection
of a tagged packet from a tested egress interface with a timestamp,
Timestamp B. A set of Timestamp B values MUST be collected for all
tested egress interfaces of the DUT/SUT.
A trial MUST be considered INVALID should any of the following
conditions occur in the collection of the trial data:
. Forwarded test packets directed to improper destinations.
. Unexpected differences between Intended Load and Offered Load
or unexpected differences between Offered Load and the
resulting Forwarding Rate(s) on the DUT/SUT egress ports.
. Forwarded test packets improperly formed or packet header
fields improperly manipulated.
. Failure to forward required tagged packet(s) on all expected
egress interfaces.
. Reception of a tagged packet by the test apparatus outside the
configured test duration interval or 5 seconds, whichever is
greater.
Data from invalid trials SHOULD be considered inconclusive. Data
from invalid trials MUST not form the basis of comparison.
The set of latency measurements, M, composed from each latency
measurement taken from every ingress/tested egress interface
pairing MUST be determined from a valid test trial:
M = { (Timestamp B(E0) - Timestamp A),
(Timestamp B(E1) - Timestamp A), ...
(Timestamp B(En) - Timestamp A) }
where (E0 ... En) represents the range of all tested egress
interfaces and Timestamp B represents a tagged packet detection
event for a given DUT/SUT tested egress interface.
Results
Two types of information MUST be reported: 1) the set of latency
measurements and 2) the significant environmental, methodological,
or device particulars giving insight into the test or its results.
Specifically, when reporting the results of a VALID test trial, the
set of ALL latencies related to the tested ingress interface and
each tested egress DUT/SUT interface of MUST be presented. The
time units of the presented latency MUST be uniform and with
sufficient precision for the medium or media being tested. Results
MAY be offered in tabular format and SHOULD preserve the
relationship of latency to ingress/egress interface to assist in
trending across multiple trials.
The Offered Load of the test traffic presented the DUT/SUT, size of
the "tagged" packet, transmit duration of offered frames and nature
(i.e., store-and-forward or bit-forwarding) of the trial's
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measurement MUST be associated with any reported test trial's
result.
5.2. Min/Max Multicast Latency
Objective
To determine the difference between the maximum latency measurement
and the minimum latency measurement from a collected set of
latencies produced by the Multicast Latency benchmark.
Procedure
Collect a set of multicast latency measurements, as prescribed in
section 5.1. This will produce a set of multicast latencies, M,
where M is composed of individual forwarding latencies between DUT
packet ingress and DUT packet egress port pairs. E.g.:
M = {L(I,E1),L(I,E2), à, L(I,En)}
where L is the latency between a tested ingress port, I, of the
DUT, and Ex a specific, tested multicast egress port of the DUT.
E1 through En are unique egress ports on the DUT.
From the collected multicast latency measurements in set M,
identify MAX(M), where MAX is a function that yields the largest
latency value from set M.
Identify MIN(M), when MIN is a function that yields the smallest
latency value from set M.
The Max/Min value is determined from the following formula:
Result = MAX(M) û MIN(M)
Results
The result MUST be represented as a single numerical value in time
units consistent with the corresponding latency measurements. In
addition, the number of tested egress ports on the DUT MUST be
reported.
The nature of the traffic stream contributing to the result MUST be
reported. All required reporting parameters of multicast latency
MUST be reflected in the min/max results report, such as the
transmitted packet size(s), offered load of the packet stream in
which the tagged packet was presented to the DUT and transmit
duration of offered frames.
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6. Overhead
This section presents methodology relating to the characterization
of the overhead delays associated with explicit operations found in
multicast environments.
6.1. Group Join Delay
Objective
To determine the time duration it takes a DUT/SUT to start
forwarding multicast packets from the time a successful IGMP group
membership report has been issued to the DUT/SUT.
Procedure
Traffic is sent on the source port at the same time as the IGMP
JOIN Group message is transmitted from the destination ports. The
join delay is the difference in time from when the IGMP Join is
sent (timestamp A) and the first frame is forwarded to a receiving
member port (timestamp B).
Group Join delay = timestamp B - timestamp A
One of the keys is to transmit at the fastest rate the DUT/SUT can
handle multicast frames. This is to get the best resolution and
the least margin of error in the Join Delay.
However, you do not want to transmit the frames so fast that frames
are dropped by the DUT/SUT. Traffic should be sent at the
throughput rate determined by the forwarding tests of section 4.
Results
The parameter to be measured is the join delay time for each
multicast group address per destination port. In addition, the
number of frames transmitted and received and percent loss may be
reported.
6.2. Group Leave Delay
Objective
To determine the time duration it takes a DUT/SUT to cease
forwarding multicast packets after a corresponding IGMP "Leave
Group" message has been successfully offered to the DUT/SUT.
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Procedure
Traffic is sent on the source port at the same time as the IGMP
Leave Group messages are transmitted from the destination ports.
The leave delay is the difference in time from when the IGMP leave
is sent (timestamp A) and the last frame is forwarded to a
receiving member port (timestamp B).
Group Leave delay = timestamp B - timestamp A
One of the keys is to transmit at the fastest rate the DUT/SUT can
handle multicast frames. This is to get the best resolution and
least margin of error in the Leave Delay. However, you do not want
to transmit the frames too fast that frames are dropped by the
DUT/SUT. Traffic should be sent at the throughput rate determined
by the forwarding tests of section 4.
Results
The parameter to be measured is the leave delay time for each
multicast group address per destination port. In addition, the
number of frames transmitted and received and percent loss may be
reported.
7. Capacity
This section offers terms relating to the identification of
multicast group limits of a DUT/SUT.
7.1. Multicast Group Capacity
Objective
To determine the maximum number of multicast groups a DUT/SUT can
support while maintaining the ability to forward multicast frames
to all multicast groups registered to that DUT/SUT.
Procedure
One or more destination ports of DUT/SUT will join an initial
number of groups.
Then after a delay (enough time for all ports to join) the source
port will transmit to each group at a transmission rate that the
DUT/SUT can handle without dropping IP Multicast frames.
If all frames sent are forwarded by the DUT/SUT and received the
test iteration is said to pass at the current capacity.
If the iteration passes at the capacity the test will add an user
defined incremental value of groups to each receive port.
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The iteration is to run again at the new group level and capacity
tested as stated above.
Once the test fails at a capacity the capacity is stated to be the
last Iteration that pass at a giving capacity.
Results
The parameter to be measured is the total number of group addresses
that were successfully forwarded with no loss.
In addition, the nature of the traffic stream contributing to the
result MUST be reported. All required reporting parameters MUST be
reflected in the results report, such as the transmitted packet
size(s) and offered load of the packet stream.
8. Interaction
Network forwarding devices are generally required to provide more
functionality than just the forwarding of traffic. Moreover,
network-forwarding devices may be asked to provide those functions
in a variety of environments. This section offers terms to assist
in the characterization of DUT/SUT behavior in consideration of
potentially interacting factors.
8.1. Forwarding Burdened Multicast Latency
Objective
To produce a set of multicast latency measurements from a single,
multicast ingress port of a DUT/SUT through multiple, egress
multicast ports of that same DUT/SUT as provided for by the metric
"Multicast Latency" in RFC 2432, while burdening the DUT/SUT by
injecting addresses into the DUT/SUT address table.
Procedure
The Multicast Latency metrics can be influenced by forcing the
DUT/SUT to perform extra processing of packets while multicast
class traffic is being forwarded for latency measurements. As
described in Section 5.1, a set of ports on the tester will be
designated to be the source and destination in this test. In
addition to this setup, another set of ports will be selected to
transmit some multicast class traffic that is destined to multicast
group addresses that have not been joined by these additional set
of ports.
For example, ports 1,2, 3, and 4 form the burdened response setup
(setup A) which is used to obtain the latency metrics and ports 5,
6, 7, and 8 form the non-burdened response setup (setup B) which
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will afflict the burdened response setup. Setup B traffic will
then join multicast group addresses not joined by the ports in this
setup. By sending such multicast class traffic, the DUT/SUT will
perform a lookup on the packets that will affect the processing of
setup A traffic.
Results
Result reports MUST include the following parameters for each
iteration: transmitted packet size, the number of frames offered,
number of frames received per each group, number of multicast
groups and forwarding rate in frames per second, number of
addresses injected into address table for that iteration, and
transmit duration of offered frames. The result report must also
specify the number of source and destination ports within the
multicast group, as well as the ports designated to inject
addresses throughout the test.
The following metrics MUST be reported:
1) The set of latency measurements
2) The nature of latency measured (i.e., store-and-forward or
bit-forwarding)
3) The significant environmental, methodological, or device
particulars giving insight into the test or its results.
Constructing a table that contains the latency vs. number of
injected addresses is desirable.
8.2. Forwarding Burdened Group Join Delay
Objective
To determine the time duration it takes a DUT/SUT to start
forwarding multicast packets from the time a successful IGMP group
membership report has been issued to the DUT/SUT while burdening
the DUT/SUT by injecting addresses into the DUT/SUT address table
on a unrelated set of ports.
Procedure
The port configuration in this test is similar to the one described
in Sections 6.1 and 8.1, however, the additional set of transmit
ports, which comprise setup B, do not send multicast class
traffic. Setup A traffic must be influenced in such a way that will
affect the DUT's/SUT's ability to process Group Join messages.
Therefore, in this test, the ports in setup B will send a set of
IGMP Group Join messages while the ports in setup A are also
simultaneously joining its own set of group addresses. Since the
two sets of group addresses are independent of each other, the
group join delay for setup A may be different than in the case when
there were no other group addresses being joined.
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Results
Similar to Section 6.1, the parameter to be measured is the leave
delay time for each multicast group address per destination port.
Result reports MUST specify the number of multicast groups joined
in the join delay port group, the number of groups joined by the
unrelated ports, the number of source and destination ports within
the join delay port group, and the number of unrelated ports
designated to inject addresses throughout the test.
Constructing a table that contains the join delay time vs. number
of injected addresses is desirable.
9. Security Considerations
As this document is solely for the purpose of providing metric
methodology and describes neither a protocol nor a protocol's
implementation, there are no security considerations associated
with this document.
10. Acknowledgements
The authors would like to acknowledge the following individuals for
their help and participation of the compilation and editing of this
document û Ralph Daniels, Netcom Systems, who made significant
contributions to earlier versions of this draft, Michele Bustos,
IXIA, and Kevin Dubray, Juniper Networks.
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11. References
[Br91] Bradner, S., "Benchmarking Terminology for Network
Interconnection Devices", RFC 1242, July 1991.
[Br96] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
[Br97] Bradner, S. "Use of Keywords in RFCs to Reflect Requirement
Levels, RFC 2119, March 1997
[Du98] Dubray, K., "Terminology for IP Multicast Benchmarking", RFC
2432, October 1998.
[Hu95] Huitema, C. "Routing in the Internet." Prentice-Hall, 1995.
[Ka98] Kosiur, D., "IP Multicasting: the Complete Guide to
Interactive Corporate Networks", John Wiley & Sons, Inc, 1998.
[Ma98] Mandeville, R., "Benchmarking Terminology for LAN Switching
Devices", RFC 2285, February 1998.
[Mt98] Maufer, T. "Deploying IP Multicast in the Enterprise."
Prentice-Hall, 1998.
[Se98] Semeria, C. and Maufer, T. "Introduction to IP Multicast
Routing." http://www.3com.com/nsc/501303.html 3Com Corp.,
1998.
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12. Author's Addresses
Debra Stopp
IXIA
26601 W. Agoura Rd.
Calabasas, CA 91302
USA
Phone: 818 871 1800
EMail: debby@ixiacom.com
Hardev Soor
IXIA
26601 W. Agoura Rd.
Calabasas, CA 91302
USA
Phone: 818 871 1800
EMail: hardev@ixiacom.com
13. Full Copyright Statement
"Copyright (C) The Internet Society (date). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain
it or assist in its implementation may be prepared, copied,
published and distributed, in whole or in part, without restriction
of any kind, provided that the above copyright notice and this
paragraph are included on all such copies and derivative works.
However, this document itself may not be modified in any way, such
as by removing the copyright notice or references to the Internet
Society or other Internet organizations, except as needed for the
purpose of developing Internet standards in which case the
procedures for copyrights defined in the Internet Standards process
must be followed, or as required to translate it into.
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