Among {HEAD ~ the factors} considered in the optimization are the characteristics of the originating source and {TAIL ~ the network path} 
Among { HEAD ~ the factors } considered in the optimization are the characteristics of the originating source and { TAIL ~ the network path }
OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL