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RE: Jumbo Frames (was Re: MAE-EAST Moving? from Tysons corner torestonVA. )
From: "Roeland Meyer (E-mail)" <rmeyer () mhsc com>
Date: Mon, 19 Jun 2000 15:53:15 -0700


Marc Slemko: Monday, June 19, 2000 10:06 AM

On Mon, 19 Jun 2000, Roeland M.J. Meyer wrote:

I should have re-caveated, for your benefit. I am not testing
with a bazillion-byte file. I am testing with query/response
against a RDBMS host. IOW, a typically real-world(tm)
practical
application. The responses range from 3-50KB, with anomalies
out
to 100KB. The slow-start algorithm has been identified as the

Erm... no, then your problem is opening and closing TCP
connections all the time.  Don't do that.

I don't have much choice there. Each query/response is a new
connection. Even SQLnet is limited with batch query optimization.

It hurts you in a lot of other ways.

Yes, it does. I'm still scraping off the charred back-side meat.

It really isn't appropriate to go around saying "you need
larger MTUs to
fill a 100 meg link, period" when you really mean "in one
particular
situation where I am opening and closing TCP connections and
only sending
a very small amount of data over each, you need larger MTUs".

Hm, I don't remember the "period" and I thought that I'd outlined
my case a few messages back.

I wouldn't be so quick to say slow start is useless, either.
Perhaps with
small window sizes, but as soon as they get big enough...

Here is where you may not have thought it through enough. On a
dedicated FDX link, what need is there for slow-start? Only the
transmitter and receiver are on the wire and the other-end has a
separate transmit circuit to talk back with (the other side of
the FDX link). If the switch can't keep up then I need a switch
that can. In this case, I happen to know that the switch is fine.
I'm feeding CAT5 straight from the switch to the NIC on the
server. The other side is similarly connected. Slow-start is a
legacy requirement for non-switched networks and is still exists
for legacy reasons. In switched FDX environments, it would be
real nice if I could just turn it off, as a configuration issue.
In fact, there's a lot of stuff that could probably be stripped
from a stack, for switched FDX environs and modern SMP hosts.
Even switched 100baseTX could benefit.




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