Packet retransmission control system, method and program

• US 20110286469A1
• Filed: 08/04/2011
• Published: 11/24/2011
• Est. Priority Date: 03/03/2010
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Yasuda, Masato
• Granted Patent: US 8,717,871 B2
• Time in Patent Office: Days
• US Class Current: 370/412
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/188 Time-out mechanisms

Abstract

A lower layer retransmission control unit performs the following processing. When transmitting a transmission packet, giving a sequence number indicating a transmission order to the transmission packet. Receiving, from a receiving device that receives the transmission packet as a reception packet, an ACK packet indicating the sequence number of the reception packet. Referring to the sequence number of the received ACK packet to determine whether or not the ACK packet is received in an order of the sequence number. Transmitting first to third transmission packets and, if receiving a first ACK packet and receiving a third ACK packet following the first ACK packet without receiving a second ACK packet, performing fast retransmission control processing. Specifically, determining whether or not to receive the second ACK packet before a fast retransmission determination period passes after a reception time of the third ACK packet. If failing to receive the second ACK packet within the fast retransmission determination period, retransmitting the second transmission packet.

Claims

1. A packet retransmission control system comprising:

a network protocol stack that performs packet retransmission control; and

a lower layer retransmission control unit configured to perform packet retransmission control in a lower layer than said network protocol stack, 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 or not 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 or not to receive said second ACK packet before a fast retransmission determination period passes after a reception time of said third ACK packet; and

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.

2. The packet retransmission control system according to claim 1, further comprising a memory device in which transmission packet information is stored, wherein:

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 the 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; and

said fast retransmission determination period depends on said RTT.

3. The packet retransmission control system according to claim 2, wherein:

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

.

4. The packet retransmission control system according to claim 3, wherein:

if said calculated RTT is more 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.

5. The packet retransmission control system according to claim 3, wherein:

said lower layer retransmission control unit compares said calculated RTT with a predetermined threshold value;

if said calculated RTT is more than said predetermined threshold value, said lower layer retransmission control unit releases said transmission packet having the same sequence number as that of said received ACK packet without updating said RTTmax nor said RTTmin;

if said calculated RTT is equal to or less than said predetermined threshold value and more 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.

6. The packet retransmission control system according to claim 3, wherein:

said lower layer retransmission control unit calculates an average value of said RTT with respect to each source of said received ACK packet;

if said calculated average value is more than said RTTmax, said lower layer retransmission control unit updates said RTTmax to said calculated average value; and

if said calculated average value is less than said RTTmin, said lower layer retransmission control unit updates said RTTmin to said calculated average value.

7. The packet retransmission control system according to claim 3,

wherein if a specified condition is met, said lower layer retransmission control unit resets said RTTmax and said RTTmin.

8. The packet retransmission control system according to claim 1, comprising:

a transmitting device; and

said receiving device, wherein;

each of said transmitting device and said receiving device comprises said network protocol stack and said lower layer retransmission control unit;

said lower layer retransmission control unit of said transmitting device transmits said transmission packet to said receiving device; and

said lower layer retransmission control unit of said receiving device sends said ACK packet back to said transmitting device.

9. A packet retransmission control method comprising:

performing packet retransmission control by a network protocol stack; and

performing packet retransmission control in a lower layer than said network protocol stack,

wherein said performing packet retransmission control in said lower layer comprises;

giving, when transmitting a transmission packet, a sequence number indicating a transmission order to said transmission packet; and

receiving, from a receiving device receiving said transmission packet as a reception packet, an ACK packet indicating said sequence number of said reception packet,

wherein 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, and

said ACK packet responding to a third transmission packet that is transmitted after said second transmission packet is a third ACK packet,

wherein said performing packet retransmission control in said lower layer further comprises;

referring to said sequence number of said received ACK packet to determine whether or not to said ACK packet is received in an order of said sequence number; and

performing fast retransmission control processing, if receiving said first ACK packet and receiving said third ACK packet following said first ACK packet without receiving said second ACK packet,

wherein said fast retransmission control processing comprises;

determining whether or not to receive said second ACK packet before a fast retransmission determination period passes after a reception time of said third ACK packet; and

retransmitting said second transmission packet, if failing to receive said second ACK packet within said fast retransmission determination period.

10. A packet retransmission control program recorded on a tangible computer-readable medium that, when executed, causes a computer to perform packet retransmission control processing,

wherein said packet retransmission control processing comprises performing packet retransmission control in a lower layer than a network protocol stack that performs packet retransmission control,

wherein said performing packet retransmission control in said lower layer comprises:

giving, when transmitting a transmission packet, a sequence number indicating a transmission order to said transmission packet; and

receiving, from a receiving device receiving said transmission packet as a reception packet, an ACK packet indicating said sequence number of said reception packet,

wherein 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, and

said ACK packet responding to a third transmission packet that is transmitted after said second transmission packet is a third ACK packet,

wherein said performing packet retransmission control in said lower layer further comprises;

referring to said sequence number of said received ACK packet to determine whether or not to said ACK packet is received in an order of said sequence number; and

performing fast retransmission control processing, if receiving said first ACK packet and receiving said third ACK packet following said first ACK packet without receiving said second ACK packet,

wherein said fast retransmission control processing comprises;

determining whether or not to receive said second ACK packet before a fast retransmission determination period Passes after a reception time of said third ACK packet; and

retransmitting said second transmission packet, if failing to receive said second ACK packet within said fast retransmission determination period.