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