Pipe's parameters

Bandwidth (1 bit/s resolution).

ipfw pipe 4 config bw 803Kbit/s

Packets are extracted from the queue at a rate of BW/size
All times are rounded to 1/HZ
only accounts for IP size

Mostly useful for output traffic shaping (remember, some links have variable rate)

Works to some degree for input traffic pacing


Can also set the rate using the device's TX interrupt:

ipfw pipe 4 config bw tun0

(not yet committed, and device-dependent)