Patent ID: 8717871
Filing Date: 2014-05-06
Classification: H04L

Abstract:
1. A packet retransmission control system comprising: a network protocol stack that performs packet retransmission control; a lower layer retransmission control unit configured to perform packet retransmission control in a lower layer than said network protocol stack; and a memory device in which transmission packet information is stored, wherein: said lower layer retransmission control unit, when transmitting a transmission packet, gives a sequence number indicating a transmission order to said transmission packet; said lower layer retransmission control unit receives, from a receiving device receiving said transmission packet as a reception packet, an ACK packet indicating said sequence number of said reception packet; said lower layer retransmission control unit refers to said sequence number of said received ACK packet to determine whether said lower layer retransmission control unit receives said ACK packet in an order of said sequence number; said ACK packet responding to a first transmission packet is a first ACK packet; said ACK packet responding to a second transmission packet that is transmitted following said first transmission packet is a second ACK packet; said ACK packet responding to a third transmission packet that is transmitted after said second transmission packet is a third ACK packet; if said lower layer retransmission control unit receives said first ACK packet and receives said third ACK packet following said first ACK packet without receiving said second ACK packet, said lower layer retransmission control unit performs fast retransmission control processing; in said fast retransmission control processing, said lower layer retransmission control unit determines whether to receive said second ACK packet before a fast retransmission determination period passes after a reception time of said third ACK packet; if said lower layer retransmission control unit fails to receive said second ACK packet within said fast retransmission determination period, said lower layer retransmission control unit retransmits said second transmission packet; said transmission packet information indicates said sequence number and a transmission time with respect to each of said transmission packet; said lower layer retransmission control unit, when receiving said ACK packet, refers to said transmission packet information to obtain said transmission time of said transmission packet having a same sequence number as that of said received ACK packet; said lower layer retransmission control unit calculates an RTT (Round Trip Time) regarding said received ACK packet, based on said obtained transmission time and a reception time of said received ACK packet; said fast retransmission determination period depends on said RTT; a range of said RTT is defined as from RTTmin to RTTmax; said lower layer retransmission control unit refers to said transmission packet information to calculate a difference Δ in said transmission time between said second transmission packet and said third transmission packet; and said lower layer retransmission control unit sets said fast retransmission determination period to RTTmax−RTTmin−Δ; if said calculated RTT is greater than said RTTmax, said lower layer retransmission control unit updates said RTTmax to said calculated RTT; and if said calculated RTT is less than said RTTmin, said lower layer retransmission control unit updates said RTTmin to said calculated RTT.