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