Stan Barber's Notes NAP Quality of Service is HARD to measure. Aggregate goodput is hard to measure as is fairness. ATM Cell drops may be a problem, but it would be masked by the ADSU problems. The fixed Kentrox did definately get better, but there is still problems. With delay, the larger the delay, the window size becomes a big factor.
Good performance is only available over a very limited range of window sizes.
With a large number of flows, performance remains good at 120 millisecond delay. An ADSU solution may provide adequate performance at current traffic levels. When congestions happens, it is unclear what would happen. Fairness issues also need to be studied. The vBNS requirements cannot be met by the current ATM NAP architecture.