Retransmission-request transmitting method and receiving side apparatus

A retransmission-request transmitting method in which a receiving side apparatus triggers transmission of a retransmission request for a packet from a transmitting side apparatus, the receiving side apparatus managing a receiving side window defining an upper limit value and a lower limit value of a sequence number of a receivable packet, the retransmission-request transmitting method comprising the steps of:

• activating, at the receiving side apparatus, a reordering timer, when receiving a first packet before receiving an unreceived packet with a sequence number within the receiving side window and smaller than a sequence number of the first packet;
• and
• triggering, at the receiving side apparatus, transmission of a retransmission request for the unreceived packet, when having not received the unreceived packet by the time of expiration of the reordering timer activated in response to the receipt of the first packet;
• wherein
• the receiving side apparatus stops the reordering timer activated in response to the receipt of the first packet, when a value of the sequence number of the first packet falls out of a range of the receiving side window as a result of changing the upper limit value and the lower limit value in accordance with a sequence number of a second packet received from the transmitting side apparatus.