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