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