The network includes a long haul portion with {TAIL ~ multicast enabled routers} and {HEAD ~ non multicast} enabled routers 
The network includes a long haul portion with { TAIL ~ multicast enabled routers } and { HEAD ~ non multicast } enabled routers
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH