a communications switch or router employs a replication server to perform batch processing of multicast connections . the replication server performs three distinct forms of processing using staging queues : packet arrival processing , packet replication processing , and per - interface transmission processing . packet arrival processing queues arriving packets in session queues , adds new multicast sessions to a replication set , and assigns a counter equivalent to the fan - out of the multicast session . packet replication processing assigns a descriptor to packets of each session in the replication set , and copies the descriptor to each per - interface queue . per - interface transmission processing examines each descriptor in the per - interface queue , copies the corresponding packets for transmission by the interface , adjusts the counter as each packet is copied , and clears the packet in the switch based on the adjusted counter .