IP Switches

[crompton@NADC.NADC.NAVY.MIL (D. Crompton)]

Chris,
   Your question's could be answered many ways depending on how much
money you want to throw at it. On the high end maybe a Grace card or
standalone and on the low side a cheap 286 with NRS to TNC's.

   16Mhz 286 motherboards with 4 or 8 meg on board ram can be had for
around $125 (minus the ram). If you look around you could probrobly
even find a 20Mhz. 386SX boards 16Mhz are running $325-$400 and a local
vendor is selling an SX with 32k cache for $425. With 8 ports I think
you want to get as much horsepower as you can. It is real nice to run
the system in ramdisk, eliminating the need for a harddisk. 8 ports
is about tops given the number of interrupts available. Of course a
polling type driver using 1 interrupt could also be used. I am getting
occasional overruns on my multiport switch. Some are due to my use of a
serial port to run dos remotely. Not being interrupt driven this causes
many overruns when it is being used. I am NOT using 16550's. Use of them
I am sure would eliminate this problem. Overruns need not be of great
concern unless they are numerous. An overrun would simply cause a retry
in the NRS circuit. Something that already happens in the typical multi-node
netrom connection and probably much more often. I am very happy with the
way my multi-nrs connection is running. It is not a Grace card running
56Kbit ports, but then I am not Fort Knox either. If you are independenly
rich, don't have a wife or have group support then you could look at the
high end approach. My goal was to make something work with available
materials in the best way I could. The 9600 baud (radio) multi-NRS NOS
switch was the best way for me. I have never tried 19200 NRS, but with
the radio running at 9600 or less it is not clear that there would be
any advantage to it.

Doug