[Tmrg] Round table: Buffer sizes

[Sally Floyd]

> In my limited experience, buffer sizes are typically powers of 2.  I
> propose that all "core" tests use buffers with a limit (in packets)
> equal to a power of 2.  Do others agree?

It makes sense to me to limit buffer sizes to powers of two.

I also think that the purpose of a "core" set of tests is to
explore how congestion control mechanisms perform under a
range of conditions (including boundary conditions of various
kinds).  That is, in my view, the point of a core set of tests is
not "whoever gets the highest score on these tests wins", but
in contrast, a set of tests that hopefully will shed some light
on the strong and weak points (or the tradeoffs in design)
for the congestion control mechanism under test.  With
some added guide of "we believe that these tests represent
fairly realistic scenarios", and "these other tests represent fairly
unrealistic scenarios, but are included to test boundary
conditions of various kinds, or to test conjectured conditions
of the future."

With that view in mine, I assume that a core set of tests will
include tests with buffers in packets and with buffers in bytes,
and with both Drop-Tail and AQM.

And I assume that a core set of tests will include (but not
necessarily be limited to) a realistic mix of packet sizes for
data packets on the congested link.  My memory is that for
some links that have been measured, a realistic mix means
90% of data packets with 1500 bytes, with a mix for the
remaining data packets of 500 bytes, 4000 bytes, 200 bytes,
and the like.

I also assume that a core set of tests is a set that an average
researcher can run on their computer over the weekend
(or in only a few days).  So of course, many of the tests will
have to be short samples of the possible space.

- Sally
http://www.icir.org/floyd/