Subject: Methodology for IP Mulicast Benchmarking - Encapsulation

From: "Perser, Jerry" <[email-masked]>
Date: Thu, 14 Dec 2000 15:26:03 -0800

A lot of the test sections have definitions.  Since RFC 2432 already has the
definitions, can you reword these sections to be test objective?  Sections
include 4.2, 4.3, 4.4.1, 4.4.2, 4.4.3, 5.1, 5.2, 6.1, 6.2, and 7.1.  Section
4.1 is the only one with an objective.  Section 8 has neither a test
objective nor a definition.

Encapsulation Throughput tests (section 4.4.1, 4.4.2, 4.4.3) talk about
testing and measuring the forwarding rate of the DUT/SUT.  Forwarding Rate
and Throughput are two different measurements.  The procedure and the
results should match the title of the test.  It is not clear what metric to
measure.  Also, the frame loss for a throughput is zero.  We may not want to
record a number that is always zero.

Section 4.4 describes a process where "Client B joins a multicast group (for
example, 224.0.1.1) and it sends an IGMP Join message to DUT/SUT B to join
that group."  Can you change "and it sends" to "by sending"?  The process of
joining is a single action.  The next sentence, "Client A now wants to
transmit some traffic to Client B." sounds like a unicast frame.  Client A
does not want to send to Client B, instead "Client A now wants to transmit
some traffic to the multicast group in which Client B is a member."

Section 4.4.1 procedure mentions a "(Figure B)".  Do you mean Figure 2 or
Figure 3?

In section 4.4.1 procedure,  "test port B is acting as the end of the
tunnel, and it does not have to support any tunneling protocol."  How does
test port B let DUT/SUT A know to forward the multicast group's frames out
port c' ?  Multicast devices only forward frames to ports that have joined
that multicast group.  Do you need to add DUT/SUT B into figure 3 to
transmit the encapsulated IGMP joins?

In section 4.4.1 procedure, the sentence "received encapsulated frames are
used to calculate the throughput" should be changed to "received
encapsulated frames are used to measure the throughput".  Also, can you
elaborate on "other necessary measurements"?   The methodology should state
what is necessary and what is optional. 
 
I am not familiar with encapsulation formats, but can we still meet the
requirement "all transmitted frames MUST contain a recognizable pattern that
can be filtered on in order to ensure the receipt of only the frames that
are involved in the test" (section 3) when "the frames do not have to be
decapsulated" (section 4.4.1)?

In section 4.4.2 procedure, the methodology is flawed.  The test is only
valid IF AND ONLY IF the decapsulation rate is less than the encapsulation
rate.  Configure DUT/SUT A to offer frames to DUT/SUT B at DUT/SUT A's
maximum encapsulation rate.  Unless you have frame loss, you don't know if
the decapsulation rate could be higher.

In section 4.4.3, the re-encapsulation procedure is not clear on how to
configure the three test ports.  How does Test port B know to count only
frames from Test port C and to filter out frames from Test port A?  Do both
Test ports B and C send IGMP join frames?  What is forcing DUT/SUT B to do
re-encapsulation as opposed to section 4.4.2 decapsulation?

The destination port is not specified in the results of the re-encapsulation
test.  Since DUT/SUT B sends frames to both Test port B and Test port C,
which one should be used to verify the zero-loss in the throughput
measurement.  The result section is a word for word copy of decapsulation
throughput.  Some provision should be made to either state which Test port
to record or to record both.
___________________________________________________________ 
Jerry Perser           Phone: 818.676.2320 
SmartLab Manager       Lab:   818.676.2337 
Netcom Systems Inc.    Fax:   818.880.9165 
26750 Agoura Road      Corp:  818.676.2300 
Calabasas, CA, 91302   Pager: [email-masked]