...err, I didn't realise this. Is this specification practice documented anywhere on the web?
Contention are frequently misunderstood. 5:1 actually means something more along the lines of 250 2M connections being multiplex over an ATM network onto one 100M ethernet port at the ISP end.
So I assume one also needs to take into account the maximum real-world throughput of a 100Mb ethernet port is nothing like 100Mbits / second. Most likely this is going to peak at 20Mbits / second, max. What this implies is when applying this 'hypothetical' definition of contention ratios, in practice this is more likely to become 25:1. Also, if the ISP decides to simply slot a 1Gbit ethernet link into the data stream, can they legitimately claim their users now benefit from an uprated link with a contention ratio of "0.5 to 1" ?!!!!!!! :-( David Bowles Education Support / TeacherLab