Is there a Linux driver for testing transport protocols?

I am trying to test some communication protocols, both commercial and homegrown. I would like to find an Ethernet driver that allows me to degrade the channel 开发者_如何学Goin a controllable fashion. For instance

1. specify a packet drop rate.
2. modulate the bandwidth.
3. modulate the RTT, independent of the apparent bandwidth

This may all be done performing "tricks" to the real driver's input queue. So I would simply load the driver pointing it at target existing channel and perform my tests on the new port. Anyone know if such a driver exists?

Netem does what you want at ip level.

http://www.linuxfoundation.org/collaborate/workgroups/networking/netem