A nice reference on how to tune the network performance under many operating systems can be found at:
http://www.psc.edu/networking/perf_tune.html.
The performance parameters have mainly to do with the fact that the sending and receiving buffers on the network interface have the wrong size...
Compiling a new Network Driver
For the RealTek Chips, go to SCYLD webpage and download the new drivers and instructions for building a new driver!
I downloaded and compiled the Madwifi drivers and use them to run my wireless card in the laptop. The driver works, but now I am having troubles setting up the 128bit passphrase using iwconfig as it does not accept passphrases.
