When choosing pause and resume thresholds, consider a delay in transmitting a PFC frame and processing it by the other side. For example, device A experienced congestion at time T, transmitted a PFC pause frame to device B, and B processed the frame and halted transmission at time T+D. During the delta time D, device B still kept sending traffic. If device A has configured the pause threshold to 100%, it has no free buffers available, and, therefore, packets may drop, which is unacceptable for lossless traffic classes. Lowering the pause threshold, let's say, down to 80% issues a PFC pause frame while still having free memory to accumulate traffic during the delta time D. The same applies to resume threshold. Setting it to 0% keeps the device idle during the delta time, lowering the overall throughput.