The Pittsburgh Supercomputing Center (PSC) has a nice writeup on their research into adjusting TCP parameters in order to maintain a high throughput on a system.
The article is constantly being updated, and in addition to general principles, provides specific instructions on adjusting the network stack parameters on FreeBSD, Linux, MacOS X, Solaris, Windows XP, and even more! However, despite the broad breadth of converage (including Netware 5 and HP-UX 9 and up) there is no coverage of OpenVMS. This can perhaps be forgiven considering the newness of TCP/IP on OpenVMS.
I’ll be implementing this in FreeBSD on my laptop shortly and I’ll let you know how this goes. HP-UX details and Linux details will follow as I experience them.