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