Using Win2K the file transfer took 68 seconds, and using RedHat 7.2 the file transfer took 125 seconds. At first glance this doesn't look good, but there are many other factors that must be taken into consideration to get a clear picture.
What was the load on the network during each of the file transfers? There are certain times during the day when network traffic is more dense than others. For example, if you use DHCP there will be a lot of congestion first thing in the morning from around 8-9AM because people are booting up and addresses are being alocated. Also lunch time and up to an hour before people start going home is always busy for the obvious reasons.
Make sure you do your testing under similar conditions, or in a lab environment with just the workstation and the servers connected to a switch. Check the results and see if they are different.
If all conditions were the same, I would ask were the same services running on each server. If there are more services running on the RedHat platform than that could be a reason. It could be configuration or driver issues.
Give me a low down on the conditions and I will try to get you through this....