A network includes a source of {HEAD ~ multicast packets} in {TAIL ~ a multicast session} and a plurality of multicast recipients in that session 
in
A network includes a source of { HEAD ~ multicast packets } in { TAIL ~ a multicast session } and a plurality of multicast recipients in that session
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH