DATA FILE DISTRIBUTION METHOD BY MULTICAST

PROBLEM TO BE SOLVED: To provide a file distribution method of multicast where a data file is efficiently distributed through reliable multicast even in a communication system in which a radio transmission circuit such as a satellite circuit shared by multiple accesses is used in uplink. SOLUTION: There are provided a step where a data file comprising a plurality of blocks is distributed to destinations, and a step where, after the data file is distributed, if an erroneous data distribution packet is found in the data file comprising a plurality of blocks which is received at the destination, that data distribution packet is requested again. The request is formed to indicate an offset position of the erroneous data distribution packet and a data length of the erroneous data.