Speed Freaks -- Bob Nirenberg <RNIRENBE@us.oracle.com> points out a missing element in FAQtoids 001 about ISDN and serial port limitations.
I noticed you talked about the 115 Kbps limit for Mac serial port connections to ISDN, but you could have mentioned that some ISDN devices connect to your Mac via Ethernet, which relative to ISDN has unlimited capacity.
Another reader noted that you can buy and install cheap, high-speed serial cards in Macs that have card slots and achieve the same results without buying a GeoPort compatible device.