Not necessarily. The data rate required by Roboserver is quite low since the communication with the controller is at 9600 bps, and traffic is not continuous. So the data rate is well within the 56K of the modem.
As far as response time, you will be mostly limited by the time it takes for a bit to go from the PC, through the internet, to the Roboserver PC. The "ping" time will not be very different wether via modem or DSL.
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