Session relay device and session relay method

• US 8,085,669 B2
• Filed: 11/02/2006
• Issued: 12/27/2011
• Est. Priority Date: 11/07/2005
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Hama, Takayuki
• Primary Examiner(s): Ngo, Ricky
• Assistant Examiner(s): Masur, Paul
• Application Number:
  US12/092,037
• Publication Number:
  US 20090268742A1
• Time in Patent Office: 1,881 Days
• Field of Search: 370/232, 370/235, 370/236, 709/227, 709/228
• US Class Current: 370/236
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• CPC Class Codes: H04L 47/36 by determining packet size, e.g. maximum transfer unit [MTU]
• CPC Class Codes: H04L 47/40 using split connections
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/166 IP fragmentation; TCP segmentation

Abstract

A session relay device which can reliably send a data packet from a source to a destination without the need for reconfiguring and dividing a segment is supplied. Session relay device 110, adapted to be disposed between terminals for transmitting and receiving data as packets to which sequence numbers representative of the order of segments to be transmitted are assigned, includes session relay section 110-3 that relays data transmitted as packets between a first session opened between session relay device 110 and a terminal on a transmission side and a second session opened between session relay device 110 and a terminal on a reception side. Session relay section 110-3 receives the retransmitted segment from a terminal on the transmission side, updates a maximum segment size of the second session with the segment size of the retransmitted segment, and transmits the retransmitted segment to a terminal on the reception side.

Claims

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.

2. The session relay device according to claim 1, wherein said transmission acknowledgement packet comprises an ACK packet in accordance with TCP.

3. 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;

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; and

a minimum sequence number calculator for calculating a sequence number when a delivery segment size of a packet relayed toward the terminal on the reception side has reached the maximum segment size of said second session;

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 the sequence number calculated by said minimum sequence number calculator, 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 the maximum segment size acknowledged for transmission has reached the calculated sequence number, then said transmission acknowledgement packet transfer/termination determining section terminates said transmission acknowledgement packet.

4. The session relay device according to claim 3, wherein said transmission acknowledgement packet comprises an ACK packet in accordance with TCP.