[Aslan[TLD]]

That 7 KB per second should be kiloBYTES per second. That 128 kbps on your ISDN is kiloBITS per second. There is a factor of 8 at work there. ISDN/Cable/DSL connections are only able to support a few players (<6) reliably.

I just took a look at my server and right this moment it has 16 players on it and is consuming 50 kiloBYTES per second incoming and about another 50 kiloBYTES per second outgoing for a total bandwidth consumption of 100 KiloBYTES = 800 KiloBITS per second.

Typically it is going to be your outgoing bandwith that is the limitation. For instance, at home I have cable and it has 1.5 Megabits per second incoming but only 256 kilobits per second outgoing. This means that if I use my entire outgoing bandwidth, I could theoretically host 10 players. However in practice you don't get that much outgoing bandwidth steadily and quality of play starts to break down around 6 players. That is with an outgoing pipe that is twice as big as what your ISDN has. So figure 3-4 tops for your connection.