The unicast response enables non multicast routers in the Internet backbone to handle the response, thereby circumventing {HEAD ~ congested multicast} enabled {TAIL ~ routers} 
The unicast response enables non multicast routers in the Internet backbone to handle the response , thereby circumventing { HEAD ~ congested multicast } enabled { TAIL ~ routers }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL