Data communication system, data communication method, and recording medium with data communication program recorded thereon

A data communication system comprising a data transmitter, a data receiver, and a network for connecting the data transmitter to the data receiver, wherein said data transmitter transmits data packets to the data receiver, said data receiver transmits an ACK packet for informing the data transmitter of the confirmation of the delivery of the received data packet, and said data transmitter detects the loss of the transmitted data packet based on the content of the ACK packet and retransmits the data packet, which has been detected to be lost, whereby error control of data packets is carried out,

• said data transmitter comprising:
• a counter for counting the number of round trips of data packets transmitted;
• first and second tables for storing predetermined data;
• means for storing, for each transmitted data packet, the relationship between the data packet and the time at the point of the transmission of the data packet in the first table;
• means for storing, in the second table, for each counter value in the counter, the relationship between the counter value and the time at the point of the transmission of the first data packet after the counter has indicated said counter value;
• and
• means which, when the value of the time stored in the first table is smaller than the value of the time corresponding to a counter value which is two smaller than the current counter value stored in the second table, judges that the data packet corresponding to the time stored in the first table has been lost, followed by the retransmission of the data packet which has been judged to be lost.

A data communication method comprising the steps of:

• providing a data communication system comprising a data transmitter, a data receiver, and a network for connecting the data transmitter to the data receiver;
• transmitting data packets by the data transmitter to the data receiver;
• transmitting an ACK packet for informing, by the data receiver, the data transmitter of the confirmation of the delivery of the received data packet;
• detecting the loss of the transmitted data packet, by the data transmitter, based on the content of the ACK packet;
• and retransmitting the data packet, which has been detected to be lost, by the data transmitter, thereby performing error control of data packets, wherein
• the data transmitter is provided with a counter for counting the number of round trips of data packets transmitted, and
• for each transmitted data packet, the relationship between the data packet and the counter value at the point of the transmission of the data packet is stored, and, when the stored counter value is two or more smaller than the current counter value at that time, the data packet corresponding to the stored counter value is regarded as having been lost, followed by the retransmission of the lost data packet.

A data communication method comprising the steps of:

• providing a data communication system comprising a data transmitter, a data receiver, and a network for connecting the data transmitter to the data receiver;
• transmitting data packets by the data transmitter to the data receiver;
• transmitting, by the data receiver, an ACK packet for informing the data transmitter of the confirmation of the delivery of the received data packet;
• detecting the loss of the transmitted data packet, by the data transmitter, based on the content of the ACK packet;
• and retransmitting the data packet, which has been detected to be lost, by the data transmitter, thereby performing error control of data packets, wherein
• the data transmitter is provided with a counter for counting the number of round trips of data packets transmitted, and first and second tables for storing predetermined data, for each transmitted data packet, the relationship between the data packet and the time at the point of the transmission of the data packet is stored in the first table,
• for each counter value in the counter, the relationship between the counter value and the time at the point of the transmission of the first data packet after the counter has indicated said counter value is stored in the second table, and
• when the value of the time stored in the first table is smaller than the value of the time corresponding to a counter value which is two smaller than the current counter value stored in the second table, the data packet corresponding to the time stored in the first table is regarded as having been lost, followed by the retransmission of the data packet which has been judged to be lost.

A data communication method comprising the steps of:

• providing a data communication system comprising a data transmitter, a data receiver, and a network for connecting the data transmitter to the data receiver;
• transmitting data packets by the data transmitter to the data receiver;
• transmitting, by the data receiver, an ACK packet for informing the data transmitter of the confirmation of the delivery of the received data packet;
• detecting the loss of the transmitted data packet, by the data transmitter, based on the content of the ACK packet;
• retransmitting the data packet, which has been detected to be lost, by the data transmitter, thereby performing error control of data packets;
• and performing transmission flow control by a transmission window, during error control in its period between the detection of the loss of a data packet and the confirmation of the delivery of the data packet by the data transmitter, wherein
• the data transmitter functions to release, from the transmission window, a closed window to an extent corresponding to the total size of data, for which delivery confirmation has been newly made by ACK packets received from the data receiver during the error control, and consequently renders the released window transmittable.