Patent ID: 7417990

Claim:
A Layer 2 switch disposed between a user terminal and a packet transfer apparatus, for passing a packet, the Layer 2 switch comprising: a user management table for storing an address of a multicast group which the user terminal is going to join, a channel interface number connected to the user terminal, and a MAC address of the user terminal; a multicast connection management table for storing a channel interface number of a multicast connection to be made to the packet transfer apparatus and a MAC address of the packet transfer apparatus, corresponding to an address of a multicast group which the user terminal is going to join; a channel interface connected to a network; and a processor which has access to each of the tables and transfers a multicast packet between the user terminal and the packet transfer apparatus through the channel interface; the processor comprising: a means for receiving a packet of a multicast reception request message for joining a multicast group having a multicast group address, from a user terminal desiring to receive a multicast packet through the channel interface; a means for terminating the received packet without transferring the packet to the packet transfer apparatus of high-level if it is judged from the header or the data portion that the packet from a user terminal contains a multicast reception request message; a means for determining whether a multicast connection has already been made, in accordance with a multicast group address obtained from the received multicast reception request message, with reference to the multicast connection management table; a means for adding a multicast group address and a channel interface number and a MAC address of a user terminal from which the multicast reception request message is sent, if the multicast reception connection has already been made; a means for receiving a multicast packet from the packet transfer apparatus and determining whether the multicast packet is received through the multicast connection, with reference to the multicast connection management table, in accordance with a multicast group address and a transmission source MAC address included in the received packet; a means for referencing the user management table in accordance with a group address included in the received packet, if the received packet is determined as being a multicast packet; and a means for copying the multicast packet for each contained user terminal while obtaining the information of a channel interface to each user terminal from the user management table, and distributing the multicast packet to each user terminal, if the user management table contains the information of a user terminal joining a group having the same group address as included in the received packet.