Patent ID: 6532233
Filing Date: 2003-03-11
Classification: H04L

Abstract:
A multicast communication apparatus comprising a center station or subscriber station in a two-way CATV network, said center station or subscriber station including:a plurality of ports for inputting/ou tputting packets; means for performing layer-2 bridging between said ports in a 7-layer OSI model; a transfer control table for holding layer-2 and layer-3 group addresses for each of said ports in the 7-layer OSI model; means for converting th e layer-3 group address into the layer-2 group address; means for transferring a multicast packet to a corresponding port upon reception of the multicast packet from an arbitrary one of said ports only when a layer-2 group address of a destination of the multicast packet is registered in said table corresponding to each of said ports other than said port through which the multicast packet has been received; means for analyzing the layer-3 message received from each of said ports, and extracting the message if the message is a management message indicating a subscription request for a layer-3 multicast group or subscription state query; means for, when the extracted management message is a multicast subscription request, checking whether the layer-3 group address corresponding to the subscription request has been registered in said table corresponding to said port through which the subscription request message has been received, not transferring the subscription request message to said other ports if the layer-3 group address has been registered, transferring the subscription request message to all said ports other than said port through which the message has been received if the layer-3 group address has not been registered, registering the layer-3 group address corresponding to the subscription request in said table corresponding to said port through which the subscription request message has been received, and also registering a layer-2 group address corresponding to the registered layer-3 group address if the layer-2 group address has not been registered in said table; means, when the extracted management message is a multicast subscription state query, transferring the subscription state query message to all said ports other than said port through which the message is received, acquiring layer-3 group addresses registered in said transfer control tables corresponding to all said ports other than said port through which the message is received, generating layer-3 multicast subscription request messages destined to the respective acquired layer-3 group addresses, and outputting the subscription state query message to said port through which the message is received; and means for, when a multicast subscription request message destined to a layer-3 group addresses registered in said table through said port for a predetermined period of time, deleting the corresponding layer-3 group address from said table, and, when no layer-3 group address corresponding to a layer-2 group address registered in said table is left as a result of deletion, deleting the corresponding layer-2 group address from said table.