In general {TAIL ~ the number} of switching modules need not be same as {HEAD ~ the number} of switching controllers 
In general { TAIL ~ the number } of switching modules need not be same as { HEAD ~ the number } of switching controllers
OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH