said sub step in {HEAD ~ step} further comprises determining survivability characteristics of {TAIL ~ the current network topology} 
said sub step in { HEAD ~ step } further comprises determining survivability characteristics of { TAIL ~ the current network topology }
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL