After performing some tuning based on the walkthrough found here: http://www.psc.edu/networking/projects/tcptune/OStune/winxp/winxp_stepbystep.html, I was able to get the Win -> Mac communications up to 260 Mbit/sec. Just for comparison, unoptimized Mac<->Linux rates were 260Mbit/sec using OS X 10.4 and FC 6. I suspect that the limitations of my switch will cap my throughput at that rate.

Naturally, after having done all of the edits instructed in the tutorial, I discovered that dslreports.com offers a utility called DrTCP that drastically simplifies making windows TCP tuning changes.  At a minimum, you will need to restart the network interface that you’ve tuned, if you don’t simply reboot the machine altogether.

For aid in testing during the tuning I used the following utilities:

• Windows – http://www.pcausa.com/Utilities/pcattcp.htm
  •  A copy of the windows binaries are at http://www.genvmunix.com/ttcpzip.exe
• Mac & Linux – http://www.genvmunix.com/ttcp.c
  • The source compiled without any changes with a few warnings doing just a cc -o ttcp ttcp.c on both unix variants.
  • If I can find a netperf client as well I will rerun my testing using that utility.

When time permits, my final round of testing will involve directly connecting the machines together and see what kind of rates I can get by eliminating the switch altogether. For now I have settled with the 260 MBits/sec.

>>>Karl