I am seeking software to measure the traffic carried by a
local area network. Can you direct me to an artificial
network traffic generator?

The features that I need are:

The ability to provide a uniform packet stream at up
to a 54 Mb/s link rate.

The ability to produce a continuous stream of packets
preferably until instructed to stop or alternatively
over a period of several minutes.

Operation under Windows XP. (I am using a special
interface for which no Linux driver is available.)

I also want a traffic generator that measures the traffic
that is successfully sent (though a separate measurement
package could work.) A single software package can avoid
the error associated with asynchronisms between the
traffic generator and the measurement interval. The data
returned by the measurement must be updated continuously
for my application, rather than only after all
measurements have completed (as does Qcheck.)