LAN/WAN fault simulation

[Michael ODonnell]

We may want to characterize some client/server systems and
applications (destined to be geographically distant from each
other) in the face of various LAN/WAN faults/conditions like
dropped/duplicate packets and varyious end-to-end throughput
rates, so I'm wondering if anybody here has a pointer to
something that might help us simulate/tweak such conditions
for in-house testing.  We're thinking a Linux box rigged as
a switch might be the heart of such a test bed but would love
not to have to reinvent any wheels...