Subject: [bmwg] Multicast Methodology: Mixed Class Throughput & Appendix A

From: "Perser, Jerry" <[email-masked]>
Date: Mon, 17 Dec 2001 16:07:11 -0800

Debbie,

I have a solution to the Appendix A issue.  If we remove Appendix A, there
are no algorithms or equations lost.  The current Appendix is just restating
the bmwg charter.  The only reference to Appendix A is the Mixed Class
Throughput test.  Please consider the follow text as a replacement for Mixed
Class Throughput:

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4.1. Mixed Class Throughput 

Objective 

To determine a DUT/SUT's throughput when both unicast frames and multicast
frames are offered to the DUT/SUT.  The DUT/SUT's ability to process both
unicast and multicast frames is observed by the same aggregated traffic
reaching the destination(s) with zero frame loss.  

Procedure 

The DUT/SUT's ports are divided into two different groups: Multicast
Transmitters (MT group) and Unicast Transmitters (UT Group).

The MT group will transmit multicast frames at an offered Load [Ma98].  The
MT group SHOULD not join any multicast groups or transmit unicast frames.
Each multicast frame received by the DUT/SUT will be sent to multiple UT
group ports.

The UT group will join all the multicast groups as well as transmit unicast
frames at an offered load.  The total number of multicast groups that a UT
group port joins SHOULD be limited to avoid congestion on that particular
port.  The "Mixed Class" is done in the DUT/SUT by replicating and
forwarding both types of traffic with no frame loss [Br91].

Specifying the mixture of multicast and unicast traffic as a percentage and
the frame rate also as a percentage could lead to confusion.  To avoid this,
the mixture of multicast and unicast traffic MUST be set up in one of two
ways:

A.) Input frame rate for each class of traffic [Br91] or as a percentage of
media_maximum-octets [Ma98].  There MUST be two rates; one for each traffic
class.
B.) As an aggregate rate (given either in frames per second or as a
percentage), with the ratio of multicast to unicast traffic declared.

Prior to transmitting any test frames, the MT group ports MUST be configured
to transmit to one or more multicast addresses.  The MT group ports MAY
transmit some learning frames for the DUT/SUT to populate its forwarding
tables.  The multicast addresses SHOULD be distributed as evenly as possible
among the MT group.  Test involving an uneven distribution MUST state which
ports are configured for more addresses.

The UT group MUST join one or more multicast groups before transmitting any
test frames.  Joining a group is accomplished by sending an IGMP Join Group
messages (see section 3 for more information.  For each multicast address
used by the MT group, at least two UT ports MUST join that multicast group.

Unicast traffic distribution can be either non-meshed or fully meshed
[Ma98].  The source and destination addresses MUST belong to a port in the
UT group.  The traffic distribution SHOULD follow either RFC2544 or RFC2889.

Frame sizes tested SHOULD include the maximum and minimum legitimate sizes
for the protocol under test on the media under test and enough sizes in
between to be able to get a full characterization of the DUT/SUT
performance.  See section 9 [Br96] for further information.

Throughput measurement is defined in RFC1242 [Br91].  A search algorithm is
employed to find the maximum offered frame rate with a zero Frame loss rate.
The algorithm MUST adjust the intended load [Ma98] to find the throughput.

Measurement

Parameters to be measured MUST include the offered load, number of multicast
frames offered, number of unicast frames offered, number of multicast frames
received and number of unicast frames received.

Reporting Format

The test setup SHOULD be reported with the a single Mixed Class Throughput
number.  Test setup includes the number of ports in the MT group, the number
of ports in the UT group, the transmitted packet size(s), ratio of unicast
traffic to multicast traffic, total number of multicast groups used, and the
traffic distribution.

The individual iterations used to find the Throughput MAY be reported for
debugging purposes. Each iteration may lead to some understanding why a
DUT/SUT did or did not perform as expected.

For multiple frame sizes, the results of the throughput test SHOULD be
reported in the form of a graph. If it is, the x coordinate SHOULD be the
frame size, the y coordinate SHOULD be the frame rate.  There SHOULD be at
least two lines on the graph.  There SHOULD be one line showing the
theoretical maximum frame rate for the media at the various frame sizes.
The second line SHOULD be the plot of the test results.

___________________________________________________________ 
Jerry Perser                         SmartBits Division 
Director of Test Methodology         26750 Agoura Road 
Phone: 818.676.2320                  Calabasas, CA, 91302
Lab:   818.676.2337                  Corp:  818.676.2300 
Pager: [email-masked]

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