An “execution server” manages requests from {HEAD ~ client machines} based on priorities assigned to {TAIL ~ the requests} 
An “ execution server ” manages requests from { HEAD ~ client machines } based on priorities assigned to { TAIL ~ the requests }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL