Transfer device and transfer method using ARQ with Packet ID and several ARQ phases

摘要

A transfer device (100) increments a value of a phase ID at predetermined time intervals, and registers a packet ID of a transmitted data packet and a phase ID on a determination table in an associated manner. When having received a response packet from a receiving-side transfer device (200), the transfer device (200) determines an unarrived packet on the basis of received packet IDs contained in the received response packet and packet IDs of transmitted data packets. Then, the transfer device (100) determines whether a data packet corresponding to the unarrived packet is lost or on-the-fly from a relationship between a phase ID of the unarrived packet and the maximum phase contained in the received response packet, and retransmits the corresponding data packet only if it is lost.