JP6268027B2 - COMMUNICATION SYSTEM, TRANSMISSION DEVICE, AND COMMUNICATION METHOD - Google Patents

Description

  The present invention relates to a technique for transferring data.

  TCP was a protocol optimized for network communication quality and speed at the time of its birth.

RFC 793

  However, the checksum of the TCP header is a 16-bit value using one's complement, and there is a problem that the reliability is lower than that of the hash function. When a hash value is assigned to a packet, a hash function must be calculated for each packet, resulting in a high CPU load.

  In addition, TCP has a problem that the overhead is too large for a high-quality and high-speed network for digital transmission using the current optical fiber. In TCP, since the transmission side always waits for ACK transmitted from the reception side, the transmission side cannot transmit a packet unless it receives ACK or times out. In particular, it is directly affected by delay in the network in physically far-distance communication.

  The present invention has been made in view of the above, and an object of the present invention is to transfer data with high reliability.

  Another object of the present invention is to transfer data at high speed.

A communication system according to a first aspect of the present invention is a communication system including a transmission device and a reception device, wherein the transmission device holds a first packet to be transmitted, and receives the first packet. Transmitting means for transmitting to the device; receiving means for receiving the second packet returned by the receiving device; comparing means for comparing the second packet with the first packet held by the buffer; Control means for instructing the transmission means to retransmit the first packet when the comparison result of the comparison means does not match, and the control means sends the second packet within a predetermined time. When a timeout occurs without receiving, the transmission means is instructed to retransmit the first packet, and when the first packet is retransmitted due to a timeout, the first packet is also timed If out waiting to backoff, when further times out, characterized in that to check the status of the receiving device by another communication method of a connection type.

  In the communication system, the transmission device transmits the next first packet without waiting for the return of the second packet.

  In the communication system, the number of the first packets to be transmitted without waiting for the return of the second packet is determined by setting.

  In the communication system, the control unit deletes the first packet from the buffer when a comparison result of the comparison unit matches.

  In the communication system, the first packet and the second packet are transferred using datagram communication.

A transmitting apparatus according to a second aspect of the present invention receives a buffer for holding a first packet to be transmitted, a transmitting means for transmitting the first packet to a receiving apparatus, and a second packet returned by the receiving apparatus. Receiving means, comparing means for comparing the second packet with the first packet held by the buffer, and retransmission of the first packet if the comparison result of the comparing means does not match Control means for instructing the transmission means to transmit the first packet to the transmission means when a timeout occurs without receiving the second packet within a predetermined time. When the first packet is retransmitted due to a timeout, if the first packet also times out, it is backed off and waits. By other communication methods ® emission type, characterized in that to check the status of the receiving device.

A communication method according to a third aspect of the present invention is a communication method between a transmitting device and a receiving device, the step of transmitting a first packet to the receiving device by the transmitting device, and the second returned by the receiving device. A step of receiving the packet, a step of comparing the second packet and the first packet, and a step of retransmitting the first packet if the result of the comparing step does not match, A step of resending the first packet when timed out without receiving the second packet within a predetermined time, and a time out of the first packet when resending the first packet due to time out If this happens, back off and wait, and if it times out, check the status of the receiver using another connection-type communication method. A method, characterized by having a.

  According to the present invention, data can be transferred with high reliability. Further, according to the present invention, data can be transferred at high speed.

It is a schematic diagram for demonstrating a mode that the communication system in this Embodiment transmits / receives a packet. It is a functional block diagram which shows the structure of the communication system in this Embodiment. It is a flowchart which shows the flow of the process which the transmitter 1 transmits a packet. It is a flowchart which shows the flow of the process in which a receiver receives a packet. It is a schematic diagram for demonstrating a mode that a packet is transmitted / received using TCP. It is the schematic diagram which showed the mode of the packet which flows through the path | route from the transmission side to the reception side.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram for explaining how the communication system according to the present embodiment transmits and receives packets.

  In the communication system according to the present embodiment, a transmission-side device and a reception-side device are connected via a high-quality and high-speed network, and packets are transmitted and received between the devices.

  In the communication system according to the present embodiment, when the transmitting device transmits a packet, the receiving device returns the received packet and transmits it. Without establishing a connection between the transmission side device and the reception side device, the transmission side device sequentially transmits the number of packets determined by the setting from the start of communication. The number of packets determined by the setting is, for example, the number of packets that does not cause congestion, and the available bandwidth is set as an upper limit or adjusted with the communication partner in advance.

  When the device on the transmission side receives the return packet sent back, it matches the transmitted packet with the received return packet, and confirms that the packet has been transmitted correctly. If the packets do not match as a result of matching, the packets are retransmitted. The packet is also retransmitted even if the return packet is not received within the timeout time.

  Currently, 10 Gigabit Ethernet is widespread. In the case of full-duplex communication such as 10 Gigabit Ethernet, even if a return packet is sent from the receiving side to the sending side at the same time as sending a packet from the sending side to the receiving side, the network is not adversely affected.

  Note that the line-side usage rate is improved because the transmitting apparatus transmits packets one after another without waiting for return packets from the receiving apparatus.

  Next, the configuration of the communication system in the present embodiment will be described.

  FIG. 2 is a functional block diagram showing the configuration of the communication system in the present embodiment.

  As shown in FIG. 2, the communication system in the present embodiment includes a transmission device 1 and a reception device 2.

  The transmission device 1 includes an input unit 11, a transmission buffer 12, a transmission unit 13, a reception unit 14, a comparison unit 15, and a control unit 16.

  The input unit 11 inputs data to be transmitted from an application or the like, divides the data into packets, and stores them in the transmission buffer 12.

  The transmission buffer 12 is a storage area for temporarily holding packets. In FIG. 2, the packet is indicated by a circle.

  The transmission unit 13 takes out the packet from the transmission buffer 12, adds a transmission source, a transmission destination, and a header including control information used for retransmission and flow control, and transmits the packet to the reception device 2. As information described in the header, for example, there is a sequence number indicating the order of packets. When the order in which the packets arrive is changed, the receiving apparatus 2 changes the order of the packets using the sequence number.

  The reception unit 14 receives the return packet transmitted from the reception device 2 and transmits it to the comparison unit 15.

  The comparison unit 15 compares the return packet and the transmitted packet stored in the transmission buffer 12. As a result of the comparison, if they match, the compared packet is deleted from the transmission buffer 12, and if they do not match, the control unit 16 is instructed to retransmit the compared packet. The transmitted packet corresponding to the return packet can be specified using, for example, a sequence number described in the packet header.

  The control unit 16 performs communication control such as packet retransmission and flow control.

  The reception device 2 includes a reception unit 21, a transmission unit 22, a reception buffer 23, and an output unit 24.

  The reception unit 21 receives a packet from the transmission device 1, stores the received packet in the reception buffer 23, and transmits the received packet to the transmission unit 22.

  The transmission unit 22 transmits the packet received from the reception unit 21 to the transmission device 1 as a return packet.

  The reception buffer 23 is a storage area that temporarily stores received packets.

  The output unit 24 takes out the packet from the reception buffer 23, reconstructs the data transmitted by the transmission device 1, and passes the data to an application or the like.

  The units included in the transmission device 1 and the reception device 2 may be configured by a computer including an arithmetic processing device, a storage device, and the like, and the processing of each unit may be executed by a program. This program is stored in a storage device included in the transmission device 1 and the reception device 2, and can be recorded on a recording medium such as a magnetic disk, an optical disk, or a semiconductor memory, or provided through a network.

  In FIG. 2, the transmission device 1 and the reception device 2 are illustrated as devices having only a transmission function and a reception function, respectively, but both the transmission device 1 and the reception device 2 may have a transmission / reception function.

  The communication system in the present embodiment can be implemented on existing datagram communication such as IP and UDP.

  Next, the operation of the communication system in the present embodiment will be described.

  First, a process in which the transmission device 1 transmits a packet will be described. FIG. 3 is a flowchart showing a flow of processing in which the transmission apparatus 1 transmits a packet.

  The transmitter 13 takes out the packet from the transmission buffer 12 and transmits it to the receiver 2 (step S11).

  Subsequently, it is determined whether the receiving unit 14 has received a return packet from the receiving device 2 (step S12).

  When the reception unit 14 receives the return packet (YES in step S12), the reception unit 14 transmits the received return packet to the comparison unit 15, and the comparison unit 15 compares the returned packet with the transmitted packet held in the transmission buffer 12. (Step S13).

  As a result of the comparison by the comparison unit 15, when the return packet matches the transmitted packet (YES in step S14), the transmitted packet is deleted from the transmission buffer 12 (step S15).

  On the other hand, if the return packet has not been received (NO in step S12), it is determined whether or not a preset very short timer has timed out (step S16). The communication system according to the present embodiment transmits and receives packets using a high-speed network, and the receiving device 2 immediately returns the received packet as it is, so there is no need to set a long timer. Therefore, in this embodiment, a very short timer is set in consideration of the communication quality of the network between the transmission device 1 and the reception device 2.

  If not timed out (NO in step S16), the process returns to step S12 to wait for the return packet.

  When the timeout has occurred (YES in step S16), the packet is acquired again from the transmission buffer 12 and retransmitted (step S17). When the timeout occurs, only about one retry is performed, and when the retry times out, back off and wait. The back-off process can be performed in the same way as CSMA / CD. Further, when the timeout occurs, the state of the receiving device 2 is confirmed using another communication method (for example, TCP).

  Also, as a result of the comparison by the comparison unit 15, when the return packet and the transmitted packet do not match (NO in step S 14), packet retransmission processing is performed (step S 17). Packet retransmission is performed for each packet.

  Subsequently, a process in which the reception device 2 receives a packet will be described. FIG. 4 is a flowchart showing a flow of processing in which the receiving device 2 receives a packet.

  When the receiving unit 21 receives the packet, it stores the received packet in the receiving buffer 23 and passes the received packet to the transmitting unit 22 (step S21).

  The transmission unit 22 transmits the packet received from the reception unit 21 to the transmission device 1 that is the transmission source of the packet (step S22).

<Comparative example>
Next, the communication method of the communication system in this embodiment and TCP are compared.

  FIG. 5 is a schematic diagram for explaining how packets are transmitted and received using TCP of the comparative example.

  In TCP, first, a connection is established between a transmission side and a reception side by a three-way handshake. After the 3-way handshake, the transmitting side transmits a packet. When the receiving side receives the packet, it returns an ACK to the transmitting side. The transmission side transmits the next packet after receiving the ACK. Therefore, as shown in FIG. 5, the transmission side generates a transmission waiting time for transmitting the next packet after transmitting the packet until receiving the ACK.

  FIG. 6 is a schematic diagram showing a state of a packet flowing in the path from the transmission side to the reception side. FIG. 6A is a diagram illustrating a state of a packet that flows in a route when TCP is used, and FIG. 6B is a packet that flows in a route when the communication system according to the present embodiment is used. FIG.

  In the example using TCP shown in FIG. 6A, since the transmitting side does not transmit packet 2 after transmitting packet 1 until it receives ACK transmitted by the receiving side, packet 2 is transmitted after packet 1 is transmitted. There is a transmission waiting time before transmitting.

  In the example using the communication system in the present embodiment shown in FIG. 6B, the transmitting side transmits the subsequent packet 2 without waiting for the return packet of the packet 1 after transmitting the packet 1. There is no transmission waiting time between the transmission of 1 and the transmission of packet 2.

  Comparing FIGS. 6A and 6B, until the transmission side confirms that packet 3 has been received after transmitting packet 1 (in the case of FIG. 6A, until ACK is received, FIG. In the case of b), the total time until the return packet of packet 3 is received is shorter in the communication system in the present embodiment.

  In TCP, a method called window control is adopted, and efficiency is improved by transmitting a plurality of packets corresponding to the window size without confirming ACK. The receiving side transmits one ACK for a plurality of packets. After receiving the ACK, the transmission side transmits a packet corresponding to one window size. Even in the window control, after transmitting a packet for one window size, a transmission waiting time occurs until ACK is confirmed.

  In TCP, a method called a sliding window is adopted, and when there is a vacant window on the receiving side, a packet is transmitted without waiting for an ACK. Since the vacant window on the receiving side is notified by ACK, a transmission waiting time occurs until ACK is confirmed even in the sliding window.

  Subsequently, the reliability is compared with the existing communication protocol.

  Although UDP exists as a protocol for transferring data at high speed, UDP does not guarantee reliability, order, and data integrity. On the other hand, in the present embodiment, since the transmission device 1 compares the transmitted packet with the return packet returned from the reception device 2, reliability and data integrity are guaranteed. Orderability can be dealt with by describing information indicating the order of packets to be transmitted in a header or the like.

  In addition, while the TCP checksum is a 16-bit value using a one's complement, in the communication system according to the present embodiment, the packet transmitted by the transmission device 1 and the packet received by the reception device 2 are directly compared. Therefore, the communication system according to the present embodiment can obtain much higher reliability (completeness) than TCP. Further, in the communication system according to the present embodiment, only a comparison is made as to whether or not the packets match, so that the processing load is not high.

  Further, in TCP, there is a case where a packet that is normally received on the receiving side is wasted due to an ACK sequence number or a timeout. On the other hand, in the communication system according to the present embodiment, only packets that do not match the comparison results and packets that have timed out are retransmitted, so that it is possible to suppress wasteful retransmission of packets.

<Application example>
Next, an application example of the communication system in the present embodiment will be described.

  As a first application example, an example applied to secret sharing will be described. A secret sharing technique is known in which three shares Sa, Sb, and Sc are created from the original data S, and the respective shares Sa, Sb, and Sc are stored separately to increase security. Furthermore, when any one of the shares Sa, Sb, and Sc is lost, there is a technique for regenerating the lost share Sa without restoring the original data S using the remaining shares Sb and Sc. To do.

  For example, three shares Sa, Sb, and Sc are stored in different regional data centers DCa, DCb, and DCc. At this time, when one regional data center DCa collapses due to an earthquake or the like, it is necessary to regenerate the share Sa lost in the new regional data center DCx. In this case, it is necessary to transfer the shares Sb and Sc from the regional data centers DCb and DCc to the new regional data center DCx, resulting in a situation where burst communication occurs. By using the communication system according to the present embodiment for communication for transferring the shares Sb and Sc to the new regional data center DCx, the lost share Sa can be regenerated as quickly as possible. Although it is possible to transfer shares Sb and Sc using TCP, it is not necessary to increase the speed of the physical line or increase the number of lines by using this communication system having a high line usage rate.

  As a second application example, an example applied to file transfer between geographically distant bases (for example, between Japan and the US) will be described. In recent years, development bases are often located in various parts of the world. Also, the amount of data handled is enormous. By using the communication system according to this embodiment when transferring a huge amount of data between geographically distant bases, it is possible to transfer data more reliably and at high speed. In addition, even if the bases are not connected by a dedicated line, the cost can be reduced by using the communication system in this embodiment. For example, a well-managed network with a guaranteed available bandwidth is more effective, but is not limited to this.

  As described above, according to the present embodiment, the packet transmitted by the transmission device 1 is returned to the transmission device 1 by the reception device 2 as a return packet, and the packet transmitted by the transmission device 1 is compared with the return packet. Thus, it can be ensured that the transmitted packet has surely arrived at the receiving device 2. Further, the transmission device 1 can improve the line usage rate by continuing to transmit packets without waiting for a response from the reception device 2.

  According to the present embodiment, unlike TCP, a slow start is not performed at the beginning of connection establishment, and the transmission apparatus 1 transmits the number of packets determined by setting from the start of communication, thereby improving the line usage rate. be able to.

  According to the present embodiment, when the comparison result with the return packet does not match or when a time-out occurs, the packet is retransmitted only for the corresponding packet, thereby causing waste of retransmission of the packet received by the receiving device 2. Absent.

  According to the present embodiment, by using existing datagram communication such as IP or UDP, it becomes possible to use commodity hardware, and a great improvement in cost performance can be expected.

DESCRIPTION OF SYMBOLS 1 ... Transmission apparatus 11 ... Input part 12 ... Transmission buffer 13 ... Transmission part 14 ... Reception part 15 ... Comparison part 16 ... Control part 2 ... Reception apparatus 21 ... Reception part 22 ... Transmission part 23 ... Reception buffer 24 ... Output part

Claims (7)

A communication system including a transmission device and a reception device,
The transmitter is
A buffer holding the first packet to be transmitted;
Transmitting means for transmitting the first packet to the receiving device;
Receiving means for receiving a second packet returned by the receiving device;
A comparing means for comparing the second packet with the first packet held by the buffer;
Control means for instructing the transmission means to retransmit the first packet if the comparison result of the comparison means does not match ,
When the control means times out without receiving the second packet within a predetermined time, the control means instructs the transmission means to retransmit the first packet, and when the first packet is retransmitted due to timeout A communication system characterized in that if the first packet also times out, it is backed off and waits, and when the time-out occurs, the state of the receiving apparatus is confirmed by another connection-type communication method .   The communication system according to claim 1, wherein the transmission device transmits the next first packet without waiting for the return of the second packet.   The communication system according to claim 2, wherein the number of the first packets to be transmitted without waiting for the return of the second packet is determined by setting.   4. The communication system according to claim 1, wherein the control unit deletes the first packet from the buffer when a comparison result of the comparison unit matches. 5. Communication system according to any one of claims 1 to 4, characterized in that the said the first packet Second packet is transferred using the datagram communication. A buffer holding the first packet to be transmitted;
Transmitting means for transmitting the first packet to a receiving device;
Receiving means for receiving a second packet returned by the receiving device;
A comparing means for comparing the second packet with the first packet held by the buffer;
Control means for instructing the transmission means to retransmit the first packet if the comparison result of the comparison means does not match ,
When the control means times out without receiving the second packet within a predetermined time, the control means instructs the transmission means to retransmit the first packet, and when the first packet is retransmitted due to timeout When the time-out also occurs for the first packet , the transmission device waits for back-off, and further checks the status of the receiving device by another connection-type communication method when time-out occurs . A communication method between a transmitting device and a receiving device,
By the transmitting device,
Transmitting a first packet to the receiving device;
Receiving a second packet returned by the receiving device;
Comparing the second packet with the first packet;
Retransmitting the first packet if the results of the comparing step do not match; and
Retransmitting the first packet when timed out without receiving the second packet within a predetermined time; and
When the first packet is retransmitted due to a timeout, if the first packet also times out, it is backed off and waits. When the timeout occurs, the status of the receiving device is confirmed by another connection type communication method. And steps to
A communication method characterized by comprising:

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