Patent ID: 7620045

Claim:
A communication system for forwarding a multicast packet transmitted from a source terminal to a destination terminal in accordance with predetermined forwarding paths, wherein the forwarding paths include a plurality of multicast-capable routers and a plurality of multicast-incapable routers, the plurality of multicast-capable routers include a non-branch router and a branch router, the non-branch router is connected to a single other multicast-capable router on the destination terminal side, and the branch router is connected to a plurality of other multicast-capable routers including the non-branch router on the destination terminal side, the non-branch router comprises: a message provider configured to generate a request message requesting deletion of an address of the non-branch router and requesting registration of an address of a register target multicast-capable router connected to the destination terminal side of the non-branch router; and a forwarder configured to forward the request message to the branch router connected to the destination terminal side of the non-branch router; the branch router comprises: a forwarding destination holder configured to hold a table in which each address of the plurality of other multicast-capable routers is registered; a forwarding destination register configured to update the table by deletion of the address of the non-branch router from the table and registration of an address of the register target multicast-capable router to the table, in accordance with receiving of the request message; and a forwarding controller configured to generate a second encapsulated multicast packet in accordance with receiving a first encapsulated multicast packet generated by setting an address of the branch router to the multicast packet, and wherein the forwarding controller is configured to generate the second encapsulated multicast packet by re-setting an address registered in the updated table to the multicast packet derived from the first encapsulated multicast packet.