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