m0n0wall with its ipfw/Dummynet traffic shaper can also be a nice "IP 
Channel Emulator" that is very useful for testing over emulated WAN 
channels. For example satellite channels have substantial delay, limited 
bandwidth and also drop packets sometimes.

Would it be possible to add a parameter "DropProbability", and 
eventually a second "QueueSize", in the Web interface "Firewall: Traffic 
shaper: Edit pipe" that match the command

    ipfw pipe NNN config  bw B  delay D  queue Q  plr P

where queue size in packets or Bytes, plr is the fraction of packets 
randomly dropped (according to FreeBSD man page of Dummynet)?

With these minimal additions, m0n0wall implicitely becomes an IP channel 
emulator with a very nice and easy-to-use Web interface.
Actually, this takes it back to the roots of Dummynet, which started off 
in research as a channel emulator, to become a traffic shaper only later :-)

Regards,
Rolf