Multicast communication method and apparatus

[0121] The second embodiment of the present invention will be explained below.

[0122] Each of terminals A, B, and C that build a network of a multicast group, as shown in FIG. 7, has an arrangement shown in, e.g., FIG. 8.

[0123] Each terminal is roughly constructed by an application 400 which implements information processing such as computerized conference and the like, and a data transfer section 200. The data transfer section 200 comprises a transmitter section 230 for transmitting a packet onto the network in response to a transmission request from the application 400 or an order control section 210, the order control section 210 for making control for maintaining order consistency of multicast data in a given group, and a receiver section 220 for receiving a packet from the network, and delivering that packet to the application 400 or order control section 210.

[0124] Terminals A, B, and C according to this embodiment are implemented using personal computers each of which comprise

[0165] The third embodiment of the present invention will be described below with reference to FIGS. 16 to 20. In this embodiment, assume that one of terminals A, B, and C that construct the network shown in FIG. 7 is a server terminal, and other terminals are client terminals.

[0166] Each client terminal is roughly constituted by an application 400 that implements information processing such as computerized conference and the like, and a data transfer section 300, as shown in FIG. 16. The data transfer section 300 comprises a transmitter section 330 for transmitting a packet onto the network in response to a transmission request from the application 400 or an order control section 310, the order control section 310 for making control for maintaining order consistency of multicast data in a given group, and a receiver section 320 for receiving a packet from the network, and delivering that packet to the application 400 or order control section 310.

[0167] As shown in FIG. 17, a data tr

[0184] The fourth embodiment of the present invention will be described below with reference to FIGS. 21 and 22. An order number issue request packet output from server and client terminals of the fourth embodiment has the format shown in, e.g., FIG. 21.

[0185] A first or second order number control section forms data transfer section frame 8 shown in FIG. 21. More specifically, each section writes a destination identifier of data requested from an application 400 in destination field 2, a self terminal identifier in source field 3, and “NULL” in order number field 4.

[0186] Data transfer section frame 8 formed by the first or second order number control section is further appended with an identifier indicating multicast as destinations to be informed to a lower layer, and the self terminal identifier as the packet source, as shown in FIG. 21, when it is output onto the network via the lower layer.

[0187] Upon receiving the order number issue request shown in FIG. 21, an order number i