Networking problems in unusual configuration

[Rick Genter x18]

I have a bizarre situation.  We have a Sun-3/180 server hooked up to an
Isolan multiport repeater.  We have four network legs connected to the
repeater (including the leg containing the server).  We have ~20 diskless
and dataless Suns hooked up to the network; some are on the same leg as
the server, while some are on the other legs.

The Suns on the server leg work fine.  The Suns on the other legs work
marginally, requiring us to cut the buffer sizes for NFS reads and writes
to 1024.  Anything larger and we get NFS Server not responding/still
trying.

For a long time we suspected the repeater, but then we got an Ethernet
test box (handy dandy little piece of equipment) and blasted packets
across the repeater in great volumes during times of great load, and never
lost a single packet.  What's even more bizarre is that the Suns on the
other legs go through tftpboot and arp and everything just fine, until
they start to "heavily" use NFS.  Thus I suspect there is some parameter
(other than rsize/wsize) in NFS that needs tweaking.

The rsize/wsize tweak is not an acceptable option; the non-server-leg Suns
run *SIGNIFICANTLY* slower than the server-leg Suns, to the point of
almost being unusable.  I tried fiddling with timeo, but with 8K buffers
even a timeo of 50 (5.0 seconds) doesn't work.

We have a variation of the problem which is that some machines on the
non-server leg will work with rsize/wsize=1024 when configured as dataless
nodes, but if you try to make them diskless nodes it doesn't matter what
size you give, they hang during /etc/rc.  They always hang executing "ps
-U"; if you comment that line out, they hang at the next command in rc
that does "significant" I/O.  (ps -U builds the file /etc/psdatabase --
it's not clear what ps does with this file, but it doesn't seem to work
without it.)  "Hanging" means "NFS Server not responding/still trying"

We've been around and around with Sun on this; I have yet to talk to
someone who struck me as halfway competent.  I've been dealing with Suns
since '82 and am no novice at this stuff, but I can't seem to convince Sun
of that (I get bullsh*t suggestions like "are your cables making good
contact").

Has anyone out there in 'Spots-Land seen anything like this?  Frankly,
we're stumped, and we're tired of dealing with the incompetent bozos at
Sun.  Thanks for hearing my gripe.

					- reg
--
Rick Genter					...!{buita,bbn}!lti!reg
Language Technology, Inc.			reg%lti.uucp at bu-it.bu.edu
27 Congress St., Salem, MA 01970		(508) 741-1507

[[ This was added later:  --wnl ]]

A followup to my last message: all machines are Sun-3s, and all are running
4.0.1 with tty patch and itrunc patch.
					-reg