To correctly implement multipoint communications without causing overflow of buffers in a service unit and in each terminal, even if multipoint communications are conducted between terminals which differ in communication conditions, such as communication speed.
Line treatment parts 2a to 2n of a multipoint communication service unit 1 have respectively sending buffers 21a to 21n for temporarily keeping data outputted to each of terminals 8a to 8n, of which the remaining quantity is measured and the measured remaining quantity is notified to a unit control part 7. When it is determined that the sending buffers 21a to 21n of the line treatment parts 2a to 2n are about to overflow or is in overflowed state, based on the noticed buffer state, the unit control part 7 notifies this to receiving buffers 81a to 81n of the line treatment parts 2a to 2n and data from terminals are made to be discarded at the inputs of the receiving buffers 81a to 81n.
YOSHIMOTO MORIO
MIO TAKESHI
OKA SUSUMU
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