PPPoEd Speed Problems - Tuning Help

[ovidiue at unixware.ro]

Hello

I've tried to optimize the speed using PPPoEd.

I have a FreeBSD Box (5.4) and 4 windoze boxes (win xp, 2000 and 98)
Without PPPoEd, the download speed is at 100mbps from FreeBSD box to windows boxes
and 80 mbps from a windoze box to another.

if i conect all windoze to pppoed freebsd server the download speed from freebsd
to windoze is 80 mbps but the speed from one windoze box to another is too slow
almost 10 mbps. why is that?

i've tried a lot of optimizing solutions but none worked. 
i've changed MTU, MRU (lower than 1492) from pppoed and tried other pppoed
parameters 

anyone have experience with that?
(for windoze box i use pppoe suport from win xp and raspppoe for windoze 2000
and 98)

i do not have any pipe, i use a simple firewall with ipfw

ovidiu