In addition, links can be added to {HEAD ~ the network topology model} to reduce {TAIL ~ the cost} of network operation 
to reduce
In addition , links can be added to { HEAD ~ the network topology model } to reduce { TAIL ~ the cost } of network operation
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH