Solaris:

set the ndd tcp_close_wait_interval to 1000 (default is I think 24000)

(NCVU will flag this for you)

Also using ndd, lock your NIC at 100 FDX if that is what it is:

In /etc/system, add this:

*  set: 100Mbps full-duplex
set hme:hme_adv_autoneg_cap=0
set hme:hme_adv_100T4_cap=0
set hme:hme_adv_100fdx_cap=1
set hme:hme_adv_100hdx_cap=0
set hme:hme_adv_10fdx_cap=0
set hme:hme_adv_10hdx_cap=0

That's for the hme type device - you may have to do it differently for 
different NICs.

I guess others can tell you how to do this on other o/s.  Here is some 
info for W2K.  Beware of tunign for backup at the expense of the 
application...

Try http://rdweb.cns.vt.edu/public/notes/win2k-tcpip.htm, and the 
microsoft document it refers to (has moved to...)

http://www.microsoft.com/technet/itsolutions/network/deploy/depovg/tcpip2k.mspx

Tells you more than you could possibly want to know.

To tune W2K itself:

http://www.microsoft.com/windows2000/professional/evaluation/performance/reports/perftune.asp

Appendix 4 of that document has tips for various specific GbE adapters.

William D L Brown