Abstract: A communication system (1) is provided with URs (20a to 20h) and a source terminal (10). The URs (20a to 20h) include: entry holders (21a to 21h) for holding forwarding addresses; message processors (25) for registering the addresses of other URs, the addresses being associated with a source terminal address and a multicast group address, in the entry holders (21a to 21h) as the forwarding addresses; message providers (26) for providing the source terminal address with join request messages which request the addition of the addresses of the URs to sending addresses. The source terminal (10) includes: an entry holder (11) for holding a sending address; and a message processor 14 for registering the addresses of the URs (20a to 20h) in the entry holder 11 as sending addresses based on the join request messages.

Abstract: A receiving device which received segments out of sequence identifies a lost segment among the segments to be received successively and transmits an acknowledgement including the number of lost segments as an advertised window size. By substituting either one of a transmitting device or a receiving device included in a communication system with a transmitting device or a receiving device of the present invention, a segment retransmission method according to the present invention is achieved. The present invention thus allows a conventional communication system to perform the lost segment retransmission of the present invention.

Abstract: A communication system (1) is provided with URs (20a to 20h) and a source terminal (10). The URs (20a to 20h) include: entry holders (21a to 21h) for holding forwarding addresses; message processors (25) for registering the addresses of other URs, the addresses being associated with a source terminal address and a multicast group address, in the entry holders (21a to 21h) as the forwarding addresses; message providers (26) for providing the source terminal address with join request messages which request the addition of the addresses of the URs to sending addresses. The source terminal (10) includes: an entry holder (11) for holding a sending address; and a message processor 14 for registering the addresses of the URs (20a to 20h) in the entry holder 11 as sending addresses based on the join request messages.

Abstract: A receiving device which received segments out of sequence identifies a lost segment among the segments to be received successively and transmits an acknowledgement including the number of lost segments as an advertised window size. By substituting either one of a transmitting device or a receiving device included in a communication system with a transmitting device or a receiving device of the present invention, a segment retransmission method according to the present invention is achieved. The present invention thus allows a conventional communication system to perform the lost segment retransmission of the present invention.