JP2008219323A - Packet communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to correctly and efficiently transmit again when the transmitting side does not receive a notification showing that a receiving side has normally received a packet transmitted from the transmitting side. <P>SOLUTION: In the packet communication method by which the transmitting side sequentially transmits a packet with a packet number attached to the receiving side, a notification is made to the transmitting side when the receiving side normally receives the packet, and the transmitting side restarts transmission at a packet number which has not been normally received by the receiving side when a notification of normally receiving the packet is not received from the receiving side, when a notification of normally receiving the packet is not received until the preceding packet of the packet with the last packet number while the data amount of the packet with the last packet number attached is one byte, a data amount from a packet with a packet number about which the notification of normally receiving the packet is not received till the preceding packet of the packet with the last packet number is divided into small parts and sequentially transmitted, and the packet with the last packet number is transmitted without reducing a data amount. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a packet communication method for retransmitting a packet from a transmission side when a notification indicating that the packet transmitted from the transmission side has been normally received at the reception side is not received at the transmission side.

  In the conventional packet communication method, packets with packet numbers are sequentially transmitted from the transmission side to the reception side, and when the reception side has received the packet normally, the fact that the packet has been received normally is transmitted to the transmission side by an ACK signal. Notify. When the transmitting side does not receive the ACK signal, it is determined that the receiving side has not received the packet correctly, that is, non-reaching (NAK) has occurred, and the unreachable packet is retransmitted. Note that the phenomenon in which the transmitting side does not receive the ACK signal occurs when the receiving side cannot receive the packet normally and does not transmit the ACK signal, and when the receiving side normally receives the packet and transmits the ACK signal. This occurs in two cases where the transmission side cannot receive the ACK signal.

  Further, the failure to normally receive a packet transmitted from the transmission side on the reception side is caused by interference radio waves, noise from other devices, or the like. The unreached state is likely to occur when the amount of data to be transmitted is large. In this case, the unreached state may not be reached again at the time of retransmission. In order to prevent non-reach due to interference such as interference from radio waves or noise from other devices, it is preferable to reduce the data amount of all packets in advance, for example, 1 byte. The inconvenience that the transmission time becomes long occurs.

  Therefore, in order to transmit data efficiently and prevent unreachability at the time of retransmission, the data amount is divided into smaller parts for packets after the packet number that has not reached, and transmission is started from the packet number that has not reached. It is effective to resume. In the packet communication method having the packet configuration shown in FIG. 6, the data amount of one packet is, for example, 256 bytes, the first packet number is 0, the last packet number is E, and the packet number [0, [1-9, A to D] to E] are transmitted in packets, and when unreachable occurs, the data amount of the packet after the packet number where unreachable occurs is divided into, for example, 32 bytes, The transmission of the packet is resumed from the packet of the packet number where the non-delivery (NAK) has occurred.

  In addition, as described above, in the method of resuming transmission by dividing the data amount into packets after the packet number that has not been delivered, when the last packet number E has not been reached (NAK), If there is, it will be divided and retransmitted as [E] [0] [1]. However, [E] indicates the end of a series of data, while [0] means the start of new data, and in the state where the series of data transmission has not yet ended, it means the start of new data. Cannot be retransmitted including [0]. Therefore, as shown in FIG. 7, the present applicant has adopted a packet communication method in which the divided transmission is started from the packet number 1 only when the last packet number E is not reached (NAK).

  However, when the packet communication method is actually performed, if the last packet number E is not reached (NAK) and transmission is resumed from packet number 1 in which the data is divided into small parts, the transmission is resumed as shown in FIG. As described above, it has been found that there is a case where the receiving side cannot receive the packet [32 bytes] of the packet number 1 and the transmitting side continuously transmits the packet of the packet number 1 endlessly. That is, if the receiving side cannot receive the last packet number E and does not transmit an ACK signal (a notification that has been normally received) to the transmitting side for receiving the packet number E, the transmitting side has not reached the packet number E. It is determined that it has occurred, the packet with the packet number E is divided, and transmission is started from packet 1. However, since the receiving side continues to wait for the arrival of the packet number E that could not be received, the data of the packet number 1 transmitted from the transmitting side is discarded even if it arrives, and an ACK signal is transmitted for the packet number 1 Will not be sent to the other side. On the other hand, since the transmitting side does not receive an ACK signal for packet transmission of packet number 1, it continues to transmit the packet of packet number 1 repeatedly.

  In addition, the phenomenon that the transmission side does not receive the notification that the last packet number E was normally received from the reception side is the case where the reception side correctly received the last packet number E and transmitted the ACK signal to the transmission side. Nevertheless, it also occurs when the transmitting side cannot receive the ACK signal for some reason. In this case, the reception side has already completed data reception up to the last packet number E, and then waits for reception of packet number 1, and in that state, the transmission side has not reached due to ACK signal not being received. Since the packet number E determined to be divided into smaller portions and transmission is resumed from the packet number 1, the reception side can correctly receive the packet number 1 transmitted from the transmission side and transmit an ACK signal to the transmission side. Such a phenomenon that the transmission side continuously transmits the packet number 1 does not occur.

JP-A-10-150435 JP 2002-344456 A

  The present invention has been made in view of the above points, and when a notification indicating that the packet transmitted from the transmission side has been normally received by the reception side cannot be received by the transmission side, the retransmission is correctly and efficiently performed. An object is to provide a packet communication method that can be performed.

  The present invention sequentially transmits packets with packet numbers from the transmission side to the reception side, and when the reception side has received the packet normally, notifies the transmission side that the packet has been received normally, and the normal A packet communication method in which the transmission side resumes packet transmission from a packet number that did not receive the normally received notification when the transmission side did not receive the notification received in If the data amount of the packet to which the last packet number is assigned is 1 byte among the received packets, and the transmission side does not receive the notification that has been normally received before the last packet number, Decrease the amount of data for packets from the packet number that did not receive the normally received notification to the packet before the last packet number. And split sequentially transmitted from the transmitting side, the packet of the last packet numbers and transmits without reducing the data amount.

  According to the present invention, since the data amount of the packet with the last packet number is set to 1 byte as a minimum unit in advance, it is difficult for the last packet number to be unreached due to a communication failure. In addition, even if the last packet number has not been reached, the data amount of the last packet that has not been reached is set to the minimum unit from the beginning, and there is little possibility of repeated failures due to communication failures. Only the packet with the last packet number may be retransmitted as it is. Furthermore, in the present invention, when the receiving side cannot receive the packet with the last packet number and is waiting for the packet with the last packet number, the packet with the last packet number is retransmitted from the sending side. Therefore, the packet with the last packet number retransmitted can be received at the receiving side, and the reception error when the data with the last packet number is divided and retransmitted from packet number 1 as described above, that is, the retransmission packet Is not received at the receiving side, and there is no possibility of causing a problem that the transmitting side retransmits the packet endlessly. In addition, the data amount of all packets is not reduced to 1 byte in advance, but data is divided and transmitted for packets from the unreachable packet number to the last packet number before the last packet number. Data can be transmitted.

  Embodiments of the present invention will be described below. 1 is a flowchart on the transmission side in a packet communication method according to an embodiment of the present invention, FIG. 2 is a diagram illustrating an example of a packet configuration, FIG. 3 is a diagram illustrating a data amount of each packet in the embodiment, and FIG. FIG. 5 is a diagram showing the data amount of each packet when failure occurs midway in the embodiment, and FIG. 5 is a diagram showing the data amount of each packet when failure occurs at the last packet number in the embodiment. It is.

  In the packet communication method of the present invention, predetermined data is transmitted from the transmission side to the reception side as a packet. The transmission side and the reception side can be connected by a wired or wireless communication path. The transmission side and the reception side are provided with known random access means that can read and write transmission data and reception data stored in a hard disk device or a memory. Examples of the device on the transmission side include a portable terminal and a personal computer, and examples of the reception side include a personal computer and a printer, each having a CPU.

  As shown in FIG. 1, on the transmission side, connection to the reception side is established by a wired or wireless communication path (S101). Next, the data read from the hard disk device, the memory, etc. is divided into a predetermined amount of data to give a series of packet numbers, and transmitted to the receiving side in the order of packet numbers (S102).

  As shown in FIG. 2, each packet 10 stores divided data, error check information in the header, and packet number in the footer. The error check information and the packet number may be stored in the header or footer, or both may be stored in the header or footer. In this embodiment, the packet number 0 is assigned to the first transmitted packet, while the packet number E is assigned to the last transmitted packet, and the packet numbers 1 to 9 and A to D are added to the packets in between. It has become. Packet number 0 indicates that the packet is transmitted first, and packet number E indicates that the packet is transmitted last. The packet with the last packet number E is 1 byte. Note that the number of packets between the first packet number 0 and the last packet number E varies depending on the amount of data to be transmitted. In the example shown in FIG. 3, the packet numbers 0 to 4 are each 256 bytes, the last packet number 5 is 255 bytes, and the last packet number E is 1 byte. Yes.

  For each packet transmission according to the packet number order, it is determined whether or not an unreached (NAK) has occurred (whether an ACK signal has been received from the receiving side) (S103), and an unreached (NAK) has not occurred (an ACK signal is not received). If it has been received), it is determined whether the packet of the last packet number has been transmitted (S104). If the packet with the last packet number has not been transmitted, 1 is added to the packet number (S105), and the packet with the added packet number is transmitted (S102). The processing of S102 to S105 is repeated until the packet with the last packet number is transmitted. When it is determined that the packet with the last packet number has been transmitted, the data transmission from the transmission side ends. When the receiving side correctly receives a packet for each packet number, the receiving side transmits an ACK signal to the transmitting side.

  On the other hand, if it is determined in S103 that unreached (NAK) has occurred (no ACK signal has been received from the receiving side), it is determined whether the next unreachable (NAK) packet is the last packet number. If the packet number is not the last packet number (S106), the data amount of each packet from the packet number that has not reached (NAK) to the one before the last packet number is set to the first packet number. (S107). For example, as shown in FIG. 4, when a non-reached (NAK) occurs in a packet with a packet number 4 (data amount 256 bytes), the packet immediately before the last packet number 4 where the unreached (NAK) has occurred. The data amount is divided into small packets up to the number. In the example shown in the figure, the packet number from which the non-delivery (NAK) occurred to the packet immediately before the last packet number is divided into 32 bytes, and the packet immediately before the last packet number is 31 bytes. It is divided into

  For packets divided into small amounts of data, transmission is resumed in order from the packet number where the non-reached (NAK) occurred (S108), and whether the non-reached (NAK) occurred from the receiving side for each transmission (ACK signal) (S109). If no delivery (NAK) has occurred (acknowledgment has been received from the receiving side), it is determined whether the packet with the last previous packet number has been transmitted (S110), and has not been transmitted. Then, 1 is added to the packet number (S111), and the packet with the added packet number is transmitted (S108). Steps S108 to S111 are repeated until the packet with the last previous packet number has been transmitted. In addition, if unreached (NAK) has occurred in S109 (no ACK signal has been received from the receiving side), transmission (S108) starts again from the packet of the packet number where unreached (NAK) has occurred. Is done.

  If it is determined in S110 that the packet immediately before the last packet number has been transmitted, or if it is determined in S106 that the packet that has not been reached (NAK) is the last packet number, Packet (1 byte) having a packet number of (1) is transmitted (S112), it is then determined whether an unreached (NAK) has occurred (whether an ACK signal has been received from the receiving side) (S113), and an unreached (NAK) is If it has occurred, the packet (1 byte) of the last packet number that has not been reached is retransmitted (S112). FIG. 5 shows the data amount of each packet when non-reach (NAK) occurs at the last packet number. On the other hand, if it is determined in S113 that the non-reaching (NAK) has not occurred, the data communication from the transmission side is terminated.

  As described above, according to the present invention, since the data amount of the last packet number packet is set to a minimum unit of 1 byte in advance, the last packet number packet is less likely to be unreached due to a communication failure. In addition, when undelivered occurs, only the packet with the last data number may be retransmitted as it is. In addition, the data amount of all packets is not reduced to 1 byte in advance, but data is divided and transmitted for packets from the unreachable packet number to the last packet number one before. Data can be transmitted.

  In the above-described embodiment, when unsuccessful occurrence occurs, retransmission is repeatedly performed until the packet that has not been reached is normally transmitted. If the maximum number of repetitions or the maximum number of repetitions is exceeded, an error notification may be issued as a timeout.

  In the above embodiment, an example in which 256 bytes are divided into 32 bytes when not achieved is shown. However, the present invention is not limited to the above example, and the initial data amount and the divided data amount are changed to other values. It may be a value.

It is a flowchart on the transmission side in the packet communication method according to an embodiment of the present invention. It is a figure which shows an example of a structure of a packet. It is a figure which shows the data amount of each packet in the Example. It is a figure which shows the data amount of each packet when non-achieving occurs in the middle in the same Example. It is a figure which shows the data amount of each packet when failure to reach | attain with the last packet number in the Example. It is a figure which shows the data amount of each packet in the case of making data amount small about the packet after the packet number by which unreachable occurred. It is a figure which shows the data amount of each packet at the time of retransmission at the time of non-delivery with the last packet number. It is a figure which shows the state of the communication error by repetition of resending in case unreachable by the last packet number.

Explanation of symbols

  10 packets

Claims (1)

The packet with the packet number is sequentially transmitted from the transmission side to the reception side, and when the reception side normally receives the packet, the reception side is notified to the transmission side, and the normal reception notification A packet communication method in which the transmission side resumes packet transmission from a packet number that did not receive the normally received notification,
The data amount of the packet assigned the last packet number among the packets assigned the packet number is 1 byte,
If the transmission side does not receive the normally received notification until the last packet number, the packet number that did not receive the normally received notification is immediately before the last packet number. A packet communication method characterized in that the data amount is divided into small parts and transmitted sequentially from the transmitting side, and the packet with the last packet number is transmitted without reducing the data amount.

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