Patent ID: 8085669
Filing Date: 2011-12-27
Classification: H04L

Abstract:
1. A session relay device adapted to be disposed between terminals for transmitting and receiving data as packets to which sequence numbers representative of an order of segments to be transmitted are assigned, for relaying data transmitted as packets between a first session opened between the session relay device and a terminal on a transmission side and a second session opened between the session relay device and a terminal on a reception side, said session relay device comprising: a session status holder for holding information of the first and second sessions; a segment retransmission determining section for, when a packet is received through the first session, determining whether the segment of the received packet is a retransmitted segment having a sequence number identical to, and a segment size different from, the segment of a packet already received through said first segment, by referring to session information held by said session status holder; a segment retransmitter for, if it is determined by said segment retransmission determining section that the segment of the received packet is the retransmitted segment, transmitting said retransmitted segment through said second session; a transmission acknowledgement receiver for receiving, through said second session, a transmission acknowledgement packet which is a response to a start packet of said first session which is relayed toward the terminal on the reception side; a transmission acknowledgement packet transfer/termination determining section for determining whether it is to transfer or terminate the transmission acknowledgement packet received by said transmission acknowledgement receiver; and a transmission acknowledgement transmitter for generating a new transmission acknowledgement packet for said start packet and transmitting the new transmission acknowledgement packet to the terminal on the transmission side if said transmission acknowledgement packet transfer/termination determining section determines that it is to terminate the transmission acknowledgement packet; wherein said session status holder holds, as said session status information, a transmission sequence number of said start packet and a transmission acknowledgement sequence number of a transmission acknowledgement packet received from the terminal on the transmission side; and if a maximum segment size acknowledged for transmission which is represented by the difference between said transmission sequence number and said transmission acknowledgement sequence number is smaller than a preset value given as a multiple of the maximum segment size of said second session, then said transmission acknowledgement packet transfer/termination determining section transfers said transmission acknowledgement packet through said first session toward the terminal on the transmission side, and if said difference between said sequence numbers has reached said preset value, then said transmission acknowledgement packet transfer/termination determining section terminates said transmission acknowledgement packet.