Just try to bring up another point. Anyone has thought about Gigabit ethernet

Prominet's Cajun switch has a 45GB backplane. Supports up to 24 full-duplex
Gigabit ethernet ports or 120 full-duplex fastethernet ports, or a mix
of both. The price is also very reasonable.

There was a BOF at the last NANOG about the Digital version,
Gigaswitch/Ethernet. However, it wasn't clear what the switch did
when congested. There was some mention of IEEE congestion control,
but that seems to use some sort of back pressure on the sender. I
don't think that is what you want in an exchange point. A single
congested egress port shouldn't block an ingress port at an exchange
point. Especially if you are going to mix different types and speeds
of ports.

There was also some concern about the amount of buffering in the switch.
And finally, when fully maxed out with ports the switch is oversubscribed,
but that could be managed by only using two port cards rather than four
port cards. And for a MAE-East size exchange, you will still quickly be
faced with the problem tying two or more switches together, which makes
the congestion control issue even more critical if it happens on a port
between switches.