Is there any "end all" benchmark tool that gives an accurate account of the performance of each layer in the network stack?  I would like to be able to analyze any bottlenecks in the network stack.  Seems like such an obvious thing to do.  Just to give a little background, I am a device driver/embedded firmware/software guy.  I don't get into the layers above the hardware much, I am trying to find out where I can expect networking bottle necks so I can analyze the value add of specific hardware solutions.