TCP/IP only use.(TfGen uses UDP. Therefore at least one destination IP node is required)
TfGen can generate multicast traffic (Vers. 0.4 or later).
TfGen can generate traffic with some traffic patterns (Vers. 0.6 or later).
TfGen generates traffic to the destination at the rate of octet per 10mS (in "Continuous and Constant" mode).
For Windows platform, I recommend you to use Windows NT/2000. Of course you can use Windows 9x. But by default setting, the utilization you specified in TfGen will not match real utilization. If you need to use TfGen on Windows 9x, please try option described in below "How to use it" as workaround.
Lab use only. (You should not use TfGen in the network for business!)