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RE: PMTU-D: remember, your load balancer is broken
From: "Roeland Meyer (E-mail)" <rmeyer () mhsc com>
Date: Wed, 14 Jun 2000 09:06:52 -0700

Valdis.Kletnieks () vt edu: Wednesday, June 14, 2000 8:07 AM

On Tue, 13 Jun 2000 22:36:08 MDT, Marc Slemko said:

It is also a concern that, in my experience, many of the
links with
MTUs <1500 are also the links with greater packet loss, etc.
you really don't want fragmentation on them.

The worst part here is that I suspect that most of these
links (just on
sheer numbers of shipped product) are the aformentioned Win98

I just set my dial PPP ports to MTU=512+40=552, is this wrong?
Where does the MTU=576 number come from?

I seem to remember that the *original* motivation for
slow-start and
all that was Van Jacobson's observation that the most common
cause of
a TCP retransmit was that an *entire* packet had been silently
due to queueing congestion, and could thus be treated identical
an ICMP Source Quench.

Has this changed?  Has "fragmentation" become a Great Evil,
rather than
an annoyance that some links have to deal with?

I'm having some trouble getting full throughput from a GigE pipe.
Even in the 100baseTX/FDX down-stream, I'm not getting full link
utilization (everything on switches, Cat6509 and 3512XLs). I'm
considering increasing MTU sizes to MTU=4096+40, or even larger.
Most of the data transmissions fall into the 5KB-50KB range. The
site can be considered a large portal. What would be the effect
on my upstream? Would it create problems? The only systems that
see the Internet are the web-servers (dual NICs).

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