Patent ID: 7532624

Claim:
A multicast packet control apparatus for relaying packets between a plurality of user terminals and a packet transfer apparatus in a network system where multicast communication is performed by a point-to-point connection between the user terminals and the packet transfer apparatus, the multicast packet control apparatus comprising: a multicast transmission buffer for storing packets used in multicast communication; a transfer limitation table for storing transfer rate limitation information corresponding to the utilization rate of the multicast transmission buffer, and for limiting transfer from the multicast transmission buffer to the packet transfer apparatus; a discard table for storing a group address and a transmission-source address, and for recording a discarded packet; and a processor for controlling packet transfer by referencing and updating the transfer limitation table and the discard table, wherein the processor transfers a received packet to the multicast transmission buffer when the received packet is determined to be a response packet corresponding to join confirmation from the packet transfer apparatus; the processor monitors the utilization rate of the multicast transmission buffer, compares the monitored utilization rate with the utilization rate of the multicast transmission buffer specified in the transfer limitation table when the response packet is transferred to the multicast transmission buffer, obtains corresponding transfer rate limitation information, and limits the transfer rate or the number of packets transferred from the multicast transmission buffer to the packet transfer apparatus in accordance with the transfer rate limitation information if a limitation is needed; the processor searches through the discard table if the response packet is received while the limitation is imposed; the processor discards the received packet if the discard table contains no data item corresponding to the group address and the transmission-source address of the received packet, and records the group address and the transmission-source address in the discard table; and the processor stores the received packet in the multicast transmission buffer with priority if the discard table contains data items corresponding to the group address and the transmission-source address of the received packet, and deletes the data items corresponding to the group address and the transmission-source address from the discard table.