Server Sizing

Here are some general guidelines for sizing a K12LTSP server:

256M Ram + 50M Ram for each concurrent terminal session (more is better). Memory-intensive applications, such as image editing, will require much more per conncurrent client. At least a Gig of ram is recommended.
If you have more than six or so terminals, strongly consider SCSI drives over IDE drives. If you have more than a dozen terminals, you will NEED SCSI drives
CPU speeds depend on applications being used. Light word processing and web browsing requires very little CPU speed (a 1Ghz PIII could easily drive dozens of terminals). Heavy-duty graphics manipulation (editing large images in the GIMP) and other such resource-intensive applications will need heavy-duty CPU power (dual P4 Xeons).
100Mb ethernet on the server will work fine for up to 30 or so terminals, more than that on a single server would benefit from a 1000Mb nic in the server, to lower latency.
100Mb is fine for each of the clients.
10Mb works, though with a longer repaint time. Very useable.
Remember, a switch is 10x better than a hub.
A hub still works - in the third world.

See the K12LTSP Case Studies web page for descriptions of systems in production.