Principle (Buffer Position): If all non-bottleneck machines are identical and all buffers are of equal size, then the increase in throughput from adding an additional buffer space will be largest either directly before or after the bottleneck station.

The principle states that all things being equal, buffers near the bottleneck are most helpful in improving throughput.  This follows from the fact that throughput is proportional to the fraction of time the bottleneck is busy.  As noted earlier, increasing buffer sizes increases throughput by reducing blocking and starving of stations. An increase in buffer space directly before the bottleneck station will reduce starving of the bottleneck station in cases of stoppage of a upstream station. Similarly an increase in the buffer space directly behind the bottleneck station will reduce blocking in the case of failures or other disruptions in a downstream station. Because buffers immediately adjacent to the bottleneck provide the greatest protection against blocking/starving, they have the largest effect on the throughput.
 
 
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