JP5539161B2 - Data transmission method and multi-site data distribution method - Google Patents

Description

  The present invention relates to a communication control method for transmitting data at high speed. The present invention also relates to a multi-site data distribution method using the communication control method.

  Conventionally, TCP (Transmission Control Protocol) is generally used for file transmission. However, TCP throws a certain amount of packets and then waits for a response packet, so the round-trip delay (RTT) between bases is extremely high in communication speed. Affects. In the case of a standard 64 KB window size between Tokyo and Osaka (assuming RTT is 20 ms), the speed is theoretically only up to 25.6 Mbps, no matter how fast a line is prepared. If the window size is increased, the theoretical communication speed increases because the size of data that can be transmitted at one time increases. However, if packet loss occurs, the transfer speed slows down due to the time required for retransmission and the transfer efficiency. May fall.

  On the other hand, although there is an existing technology for performing data transfer using UDP (User Datagram Protocol), it is necessary to set an optimum parameter for the line to be used, and packet loss and fluctuation of delay. There are many problems that have not been solved in the past, such as the transfer rate being reduced when the problem occurs, and the line capacity not being fully used.

  Conventionally, in order to perform simultaneous transmission to a plurality of sites, a system in which a server is placed in the center and distributed to each site is known. Although there is a protocol called multicast, it is difficult to adapt to the general Internet, or control for packet loss is required separately (see Patent Document 1).

JP 2008-85932 A JP 2000-207298 A

  In many conventional data transmission systems, packet loss is defined as congestion, and when packet loss occurs, it is considered that congestion has occurred. In general, control is performed so that packet loss does not occur, and when packet loss occurs, a transfer rate and a packet transfer interval are controlled so that congestion is suppressed.

  For this reason, the conventional data transmission system has the subject that communication speed will fall significantly, if packet loss arises. In addition, it has been pointed out that the conventional data transmission method has a communication speed lowering due to fluctuations in packet delay, a communication speed at the beginning of communication being slow, and a communication speed being affected if RTT is large. Yes.

  In addition, in the distribution method that transmits data to multiple sites almost simultaneously, the central server method requires a high-performance central server that can withstand simultaneous distribution at multiple sites and a broadband line that matches the number of distribution destinations. is there. When multicast distribution is used, a special line is required, and retransmission and the like must be individually controlled from the server to cope with packet loss.

  The present invention has been made in view of such circumstances, and on the premise that packet loss and delay fluctuation occur during data transmission, even if packet loss occurs, the data transmission speed is not greatly reduced. It intends to provide a high-speed data transmission system. In addition, using such a data transmission method, a distribution method for distributing data to a plurality of locations almost simultaneously is provided.

  A data transmission method according to an embodiment of the present invention is a method for transmitting data from a transmission-side device to a reception-side device via a packet communication network. And a second step of receiving an acknowledgment sent from the receiving device, indicating that the receiving device has received at least some of the plurality of packets, and A third step of retransmitting a packet that has been sent before the packet whose receipt has been confirmed by the receipt confirmation and that has not received the receipt confirmation. That is, in one embodiment of the present invention, a packet transmitted before a packet for which an acknowledgment (Ack) is returned after continuous transmission of packets is regarded as a packet loss, which is different from the conventional data transmission method. Even if the receipt is not confirmed before a certain period of time elapses after transmission, the packet is continuously transmitted without being retransmitted. Since the network switch or the like performs processing after receiving a packet in the buffer, the probability that the packet enters the buffer can be increased as the interval between sending packets is shortened. The present invention enables higher-speed data transfer by sending packets at a speed faster than the capacity of the line. The amount of overflow of the line capacity is packet loss. However, in the present invention, since it is assumed that packet loss occurs, there is no problem in data transmission.

  In recent years, most of the devices constituting the IP network are switches, and have a buffer inside the device. The devices can communicate with each other at full timing in full duplex. The transmitted packets are temporarily stored in a buffer in the switch, and the packets are transmitted from the buffer to a communication partner to be transmitted. As long as the buffer is not full, even if packets for the same device are sent from a plurality of locations, they are only processed in sequence and no packet loss occurs. However, the delay time changes. When the buffer is full, packets that arrive thereafter are discarded (packet loss) until the buffer is full, but the packets that have entered the buffer are processed correctly. Therefore, “congestion” premised on the conventional communication control method refers to a situation where no one can perform normal communication, but such a situation is unlikely to occur between current devices.

  Preferably, the third step retransmits a packet sent a predetermined time or more before the sending time of the packet sent most recently among the packets whose receipts have been confirmed by the receiving confirmation. Since packets may arrive in reorder, by giving a little play to the time when packet loss is determined, it is almost impossible to receive a packet that has already been received again on the receiving side. Data transmission is possible.

  It is preferable that the first step includes a step of recording identification information that can identify the packet and a transmission time of the packet in association with each other when the packet is transmitted. Preferably, the receipt confirmation includes identification information of the packet received by the recipient. Furthermore, it is preferable that the receipt confirmation includes identification information included in the past predetermined number of receipt confirmations. By sending the receipt confirmation information for the past several times in the receipt confirmation packet, it is possible to provide a data transmission method that takes into account the packet loss of the receipt confirmation packet.

  In addition, a data distribution method according to an embodiment of the present invention performs data transmission between a plurality of transmission / reception devices by performing data transmission between a plurality of transmission / reception devices capable of data transmission / reception by the above-described data transmission method. Data transmission is performed almost simultaneously. That is, using the above-described data transmission method as a basic technique, a process in which a packet thrown from the A site to the B site is relayed to the C site by the B site is repeated. Basically, a central server is not necessary for one-to-one communication. In addition, a special broadband line is not required, and a vertically symmetric optical fiber broadband line represented by a general B FLET'S can be used. Furthermore, since data is relayed in units of packets, data distribution is performed in the minimum units. As a result, data can be transferred in units of packets without waiting for the transfer of the entire file to be completed, and simultaneous transmission to a plurality of locations is possible in substantially the same time as one-to-one communication.

  According to the data transmission system of the present invention, it is possible to provide a data transmission system capable of transmitting data at high speed without causing a significant decrease in data transmission speed even if packet loss or delay fluctuation occurs during data transmission. Can do. In addition, it is possible to provide a distribution method that distributes data to a plurality of locations substantially simultaneously using such a data transmission method.

  More specifically, according to a predetermined embodiment of the present invention, a protocol for transferring data from a base to a base at high speed using an IP communication network such as the Internet and making full use of the capacity of the line, and A control method can be provided. Even on a line where packet loss frequently occurs, stable data transfer is possible with almost no influence. In addition, it is hardly affected by the line speed and the line quality, and the user can perform high-speed data transfer by using up to the capacity of the line without performing any special setting according to the line.

  In addition, according to a predetermined embodiment of the present invention, the above-described data transmission method is applied to relay a packet from a certain base to a plurality of bases, thereby enabling simultaneous transmission of data. No special line is required, and high-speed simultaneous transfer to multiple sites is possible after using the optical fiber broadband typified by general B FLET'S to the full line capacity.

It is a figure which shows the architecture of the data transmission system 1 which concerns on one Embodiment of this invention. It is a block diagram which shows the function structure of the transmission side apparatus 10 and the receiving side apparatus 20 which concern on one Embodiment of this invention. It is a flowchart which shows the control protocol of the data transmission process in one Embodiment of this invention. It is a conceptual diagram which shows the outline of the data transmission in one Embodiment of this invention. It is a schematic diagram for demonstrating the algorithm of the data transmission system which concerns on one Embodiment of this invention. It is a schematic diagram for demonstrating the algorithm of the data transmission system which concerns on one Embodiment of this invention. It is a figure which shows the architecture of the multi-site distribution system using the data transmission system which concerns on one Embodiment of this invention. It is a block diagram which shows the function structure of the transmission side apparatus 10, the receiving side apparatus 20, and the transmission / reception apparatus 70 containing these which concern on one Embodiment of this invention. It is a flowchart which shows the outline of the multi-site delivery process in one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted. Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Furthermore, the present invention can be variously modified without departing from the gist thereof.

  FIG. 1 is a diagram showing an architecture of a data transmission system 1 according to an embodiment of the present invention. The data transmission system 1 is configured by connecting a transmission side device 10 and a reception side device 20 via a network N.

  The transmission side device 10 is a device for transmitting data to the reception side device 20 via the network N. The reception side device 20 is a device for receiving data transmitted from the transmission side device 10. Each of the transmission side device 10 and the reception side device 20 may be configured by a dedicated device, or a general-purpose computer may be configured to have the functions of the transmission side device 10 and / or the reception side device 20.

  The network N is a communication line for transmitting data between the transmission side device 10 and the reception side device 20. This may be a packet communication network (or a combination thereof) typified by a LAN or the Internet network, and does not depend on the physical layer. Therefore, the physical layer may be any of Ethernet (registered trademark), wireless communication network, public telephone communication network, general telephone line network, other communication lines, combinations thereof, and the like. The network N can also include gateways, various base stations, and exchanges for connecting the communication networks.

  FIG. 2 is a block diagram illustrating functional configurations of the transmission-side device 10 and the reception-side device 20 according to an embodiment of the present invention.

  The transmission side device 10 includes a transmission time recording module 11, a packet transmission module 12, a transmission rate adjustment module 13, an acknowledgment (Ack) reception module 14, and a retransmission determination module 15.

  The transmission time recording module 11 records, in packet units, a packet number for identifying a packet and transmission time information related to the date and time when the packet was transmitted. Note that any information that can identify a packet can be used instead of the packet number. The packet transmission module 12 divides data to be transmitted into packets and transmits the packets to the network N. The transmission rate adjustment module 13 adjusts a packet transmission rate such as a bit rate transmitted to the network N. The receipt confirmation (Ack) reception module 14 receives the receipt confirmation (Ack) from the reception side device 20, and manages whether or not the reception side device 20 has received a packet for each packet number. The retransmission determination module 15 retransmits a packet that satisfies a predetermined condition to the reception side device 20.

  The receiving-side device 20 includes a packet receiving module 21, a received packet number recording module 22, a receipt confirmation (Ack) transmission module 23, a past receipt confirmation (Ack) information storage module 24, a sort processing module 25, and a reception process. A rate calculation module 26 and a timer 27 are included.

  The packet reception module 21 receives a packet transmitted from the transmission side device 10. The received packet number recording module 22 records the packet number of the received packet. When receiving a packet, the acknowledgment (Ack) transmission module 23 transmits an acknowledgment of the received packet to the transmitting apparatus 10. At this time, it is preferable to return a receipt confirmation by collecting a certain number of received packets or by collecting all the packets received so far when a predetermined time has elapsed. The past receipt confirmation (Ack) information storage module 24 stores the receipt confirmation sent in the past in association with the packet number. The sort processing module 25 is for combining received packets and reading data. The reception rate calculation module 26 calculates a reception rate based on the received packet. The timer 27 measures the reception time and the like and measures the timing for transmitting the receipt confirmation.

  Next, an outline of the operation of the data transmission system 1 configured as described above will be described.

  FIG. 3 is a flowchart showing a control protocol for data transmission processing according to an embodiment of the present invention. In this embodiment, only the UDP protocol is used for data transmission and control. For this reason, it is not necessary to secure a bandwidth for TCP as compared to a protocol that controls TCP as in Patent Document 2 and uses UDP for data transfer, and can fully utilize the line capacity. Any connectionless datagram protocol can be applied without being limited to the UDP protocol. The packet of the transmission data has a packet number of the first 4 bytes excluding the UDP packet header. The remaining data excluding the first 4 bytes is a part of the data to be transferred (payload). Payload size is fixed except for the last packet of data to be sent. However, the packet number, payload size, etc. are not limited to these.

  The packet transmission module 12 of the transmission side device 10 divides the data to be transferred from the transmission side device 10 to the reception side device 20 for each payload size, adds a packet number, and transmits the packet to the reception side device 20 (S41). . At that time, the transmission time recording module 11 records the packet transmission time for each packet number.

  At the beginning of data transfer, since it is unclear how much capacity the line from the transmission side device 10 to the reception side device 20 has, the transmission side device 10 sends out packets one after another at the highest possible speed. Packets that exceed the capacity of the network N are discarded on the network N.

  When the packet receiving module 21 of the receiving side device 20 receives the packet, the sort processing module 25 sorts the packets received from the transmitting side device 10 in the order of the packet number. Data is output to the subsequent processing system (S42). However, this processing is not performed when the packet number of the received packet is already received.

  The received packet number recording module 22 of the receiving device 20 records the packet number of the received packet. The receipt confirmation transmission module 23 receives a predetermined number of packets when a certain number of packets (for example, 64) have arrived since the last receipt confirmation packet transmission or when a certain number of packets should arrive after conversion from the latest communication speed. When the time after adding elapses, a receipt confirmation (Ack) is sent to the transmitting side device 10 (S43). The sent receipt confirmation log is recorded in the past receipt confirmation information storage module 24. When recording the packet number of the received packet, the packet number that has been received in the past is also processed.

  The receipt confirmation (Ack) packet uses the first 4 bytes excluding the UDP packet header as the receipt confirmation packet number, followed by a bit calculated in the latest fixed time (for example, 1/3 second is measured by the timer 27). Add rate information. After that, the received packet numbers (4 bytes) are listed. If the packet numbers are continuous, a continuous flag is attached to the head and the last packet number of the continuous packet numbers, and the size of the receipt confirmation packet is compressed. Further, considering the possibility that the receipt confirmation packet becomes a packet loss, the packet number information listed in the past N receipt confirmation packets (for example, N = 1) is added. As a result, the receipt confirmation information is correctly transmitted to the transmission side device 10 as long as the receipt confirmation packets are not continuously lost (N + 1) times. The bit rate information is calculated by the reception rate calculation module 26 using the number of packets (including duplicate packets) received in a certain time. The past receipt confirmation is acquired from the past receipt confirmation information storage module 24.

  In the present embodiment, since it is assumed that a packet loss occurs during data transmission, the received data is often in a missing state. However, when data is output from the sort processing module 25 to a disk device or the like, the performance deteriorates unless the data is written sequentially. For this reason, the receiving-side apparatus 20 has an appropriate amount of buffer, and writes up to the part where the tooth missing state has been eliminated as sequential data to the disk device or outputs it to a later processing system.

  In the transmission side apparatus 10, when the receipt confirmation packet arrives, the receipt confirmation reception module 14 receives the receipt confirmation packet (S44). Then, for the received packet numbers listed in the receipt confirmation packet, the retransmission determination module 15 sets the most recent time among the times when the transmitting side device 10 originally sent each packet as the “response last packet transmission time”. (T), and when the difference (TS) from the transmission time (S) of the packet for which the receipt confirmation has not yet returned is equal to or greater than a predetermined threshold β (for example, β = 200 milliseconds), The packet whose acknowledgment has not been returned is retransmitted in such a way as to interrupt the next packet to be sent (S45). Note that, at the time of retransmission, the time when the packet was retransmitted is recorded.

  The transmission rate adjustment module 13 of the transmission side apparatus 10 controls the time interval for transmitting the packets thereafter, based on the most recent bit rate information described in the receipt confirmation packet (S46). Specifically, the packet is transmitted at a rate of θ times (for example, θ = 1.2) with respect to the highest numerical value (maximum value) in the bit rate information from the start of transfer. In the present invention, since it is assumed that a packet loss will occur, even if a packet is transmitted exceeding the capacity of the line and a packet loss occurs, no problem in data transmission will occur. Even if the line is excessively congested at the beginning of communication and the rate is not too high, the speed is recovered if the line is freed. On the contrary, even if the line is vacant at the beginning of communication and gradually becomes congested, the actual transfer rate for the congested area will drop, but only a small amount of packet loss will occur. It does not affect. Even if the line is congested during communication, the capacity up to the maximum value of the bit rate information is supposed to exist, so the transfer rate is not slowed down.

  If there is still a packet of data to be transmitted (S47: No), the transmitting apparatus 10 transmits the packet by repeating the processes of S41 to S46. When the data has been transmitted up to the last packet to be transmitted (S47: Yes), a packet indicating the end of the transmission data is transmitted, and the receipt confirmation has not yet returned (the transmitting side device 10 recognizes that). ) The packet is forcibly retransmitted (S48). In this forced retransmission mode, a packet for which no acknowledgment has been returned is treated as being in the same state as untransmitted, and the processing of S41 to S47 is performed. Never stop or pause the transfer. Note that the packet indicating the end of the transmission data is also subject to retransmission when the packet is lost.

  The reception side device 20 sets the reception completion status when all the packets are received, but if the packet is still sent from the transmission side device 10, the process of returning the receipt confirmation packet continues.

  The transmission side apparatus 10 repeats the process of S48 until it receives the receipt confirmation packet (S49: No). Then, the transmission processing is completed when it is detected by the receipt confirmation packet that the receiving side apparatus 20 has received all the packets (S49: Yes).

  FIG. 4 is a conceptual diagram showing an outline of data transmission in one embodiment of the present invention. As shown in the figure, in this embodiment, data packets are continuously transmitted from the transmission side device 10 to the reception side device 20 exceeding the line speed. Packets that cannot be processed by the buffer 30 such as the router on the network N are discarded (arrow 32). However, since packets are constantly coming from the transmission side device 10 to the buffer 30 such as the router, the faster this speed, The probability that a packet transmitted from the transmission side apparatus 10 enters the buffer 30 such as a router increases (arrow 34). When receiving the packet, the receiving side device 20 returns an acknowledgment (Ack) packet. At this time, the reception side device 10 collects a plurality of data packet acknowledgments into one acknowledgment packet and returns it to the transmitting side device 10. To do.

  5 and 6 are schematic views for explaining an algorithm of a data transmission method according to an embodiment of the present invention.

  FIG. 5 assumes that the data transfer rate from the transmission side device 10 is 8.192 Mbps, the payload size is 1024 bytes, that is, data packets are continuously transmitted every 1 millisecond, and RTT = 0 millisecond. ing. For example, a data packet with a packet number 1 is transmitted at a transmission time of 1 millisecond, a data packet with a packet number 2 is transmitted at a transmission time of 2 milliseconds, and thereafter a data packet with a packet number of 259 is transmitted every millisecond. ing. The transmitted data packet is recorded with the packet number and the transmission time associated with each other. A value obtained by adding a threshold value β (in this embodiment, β = 200 milliseconds) to the transmission time is the retransmission determination time. For convenience of explanation, FIG. 5 shows the transmission time and the retransmission determination time together.

  On the other hand, the receiving device 20 receives the data packet transmitted from the transmitting device 10. In the figure, the data packet with the packet number 1 is received at the reception time of 1 millisecond, the data packet with the packet number 3 is received at the reception time of 3 milliseconds, and thereafter the packet number 259 is generated without causing a delay in data transmission. Packets are received every 1 millisecond until the next data packet. However, the data packet with the packet number 2 is not received by the receiving-side device 20 due to packet loss.

  At this time, each time the receiving side apparatus 20 receives 64 data packets, the receiving side apparatus 20 collects the reception confirmation of the 64 data packets into one reception confirmation packet and returns it to the transmitting side apparatus 10. In the receipt confirmation packet 51, the receipt confirmations of the data packets having the packet numbers 1 and 3 to 65 are combined into one. The data packet with the packet number 65 is received at a reception time of 65 milliseconds, and after reception of this packet, it is assumed that the processing took 1 millisecond in this case, and the receipt confirmation packet 51 is transmitted at the time of 66 milliseconds. 10 is returned.

  Upon receiving the receipt confirmation packet 51, the transmission side device 10 identifies the data packet received by the reception side device 20 based on the packet number included in the packet, and has been received or not received in association with the packet number. Set a flag to indicate. In the example of FIG. 5, reception “done” flags are set for packet numbers 1 and 3 to 65. As a result, data packets received by the receiving side apparatus 20 and data packets not received are managed.

  Subsequently, the transmission time of the last packet (the packet transmitted most recently) among the received packets included in the reception confirmation packet is compared with the retransmission determination time of the packet that has not been received yet. The response-completed last packet transmission time obtained from the receipt confirmation packet 51 is 65 milliseconds, and the retransmission determination time of the packet number 2 that has not been received is 202 milliseconds. Since the response final packet transmission time (65 milliseconds) does not exceed the retransmission determination time (202 milliseconds) of the packet number 2, it is determined that the packet 2 is not yet required to be retransmitted.

  During this time, the transmission of the data packet from the transmission side apparatus 10 to the reception side apparatus 20 continues continuously, and the data packet with the packet number 129 is received at the time 129 milliseconds. A total of 64 packets from number 66 to packet number 129 are collected. Therefore, the reception confirmation packet 52 is transmitted from the reception-side device 20 to the transmission-side device 10 when the time is 130 milliseconds. This receipt confirmation packet 52 includes not only the receipt confirmation of 64 data packets of the newly generated packet numbers 66 to 129 but also the receipt confirmation of the previously transmitted packet numbers 1 and 3 to 65. Upon receiving the receipt confirmation packet 52, the transmission side device 10 sets a reception “completed” flag of packet numbers 66 to 129 based on the packet number included in this packet. After that, 129 milliseconds of the response final packet transmission time is compared with the retransmission determination time 202 milliseconds of the packet number 2 not yet received, and the response final packet transmission time (129 milliseconds) of the packet number 2 is compared. Since the retransmission determination time (202 milliseconds) has not been exceeded, it is determined that packet 2 is not yet required to be retransmitted.

  Thereafter, the processing is continued in the same manner, and the transmission of the data packet is continuously performed. The reception confirmation packet 53 including the reception confirmation of the packet numbers 130 to 193 is transmitted from the reception side apparatus 20 to the transmission side apparatus 10. In the transmission side apparatus 10 that has received the receipt confirmation packet 53, it is determined that the packet numbers 130 to 193 have been received. Further, since the last packet transmission time that has been responded (193 milliseconds) does not exceed the retransmission determination time (202 milliseconds) of packet number 2, it is determined that packet 2 is not yet required to be retransmitted.

  Thereafter, a reception confirmation packet 54 including reception confirmations of the packet numbers 194 to 257 is transmitted from the reception side apparatus 20. After the transmission side device 10 receives the receipt confirmation packet 54 and sets the reception “completed” flag of the packet numbers 194 to 257, the response final packet transmission time, the retransmission determination time of the packet number 2 that has not been received, Are compared. At this time, it is determined that retransmission is necessary because the response last packet transmission time (257 milliseconds) exceeds the retransmission determination time (202 milliseconds) of the packet number 2. That is, even a data packet transmitted 200 milliseconds after the transmission of the packet with the packet number 2 has already been received. Therefore, it is determined that the packet 2 has been lost and is retransmitted. Even if the retransmission process is performed immediately after reception of the receipt confirmation packet 54, the packet data to be transmitted has already accumulated in the buffer of the transmission side device 10, so that the data packet of the packet number 2 is actually retransmitted. In this example, the time is 300 milliseconds.

  During the retransmission process and after the retransmission process, the transmission side apparatus 10 continues to transmit data packets, and the reception side apparatus 20 transmits a reception confirmation packet 55 including reception confirmation of packet numbers 258 to 321. The transmission-side apparatus 10 receives the receipt confirmation packet 55, and manages the received “done” packet and performs retransmission determination processing.

  FIG. 6 shows an embodiment in the case where a data transmission delay occurs in the middle of the setting example similar to FIG. In the example of the figure, the same processing as in FIG. 5 is performed until the time of 129 milliseconds. In other words, data packets continue to be transmitted from the transmission side device 10 every 1 millisecond. The receiving side device 20 returns receipt confirmation packets 61 and 62. The data packet with the packet number 2 is lost.

  In such a situation, in the example of FIG. 6, a data transmission delay occurs after receiving the packet with the packet number 129, and the data packet with the packet number 130 is received 500 milliseconds later, that is, at a time of 630 milliseconds. Second, and then one data packet is received every millisecond.

  At this time, the reception confirmation packet 63 is transmitted from the receiving-side apparatus 20 at time 694 milliseconds. When receiving the receipt confirmation packet 63, the transmission side apparatus 10 determines that the packet numbers 130 to 193 have been received based on the packet number included in the receipt confirmation packet 63. Further, since the last packet transmission time that has been responded (193 milliseconds) does not exceed the retransmission determination time (202 milliseconds) of packet number 2, it is determined that packet 2 is not yet required to be retransmitted.

  Thereafter, the reception confirmation packet 64 including the reception confirmation of the packet numbers 194 to 257 is transmitted from the reception-side apparatus 20 at time 758 milliseconds. After the transmission side apparatus 10 receives the receipt confirmation packet 64 and sets the reception “completed” flag of the packet numbers 194 to 257, the response final packet transmission time, the retransmission determination time of the packet number 2 that has not been received, Are compared. At this time, it is determined that retransmission is necessary because the response last packet transmission time (257 milliseconds) exceeds the retransmission determination time (202 milliseconds) of the packet number 2. For example, the data packet with the packet number 2 is retransmitted at a time of 800 milliseconds.

  As is apparent from a comparison between FIG. 5 and FIG. 6, in this embodiment, even if the network is congested and a large delay occurs, the comparison target does not change, so there is no problem. In contrast, in the normal data transmission method, when a data transfer delay occurs in the network, the transmission of the data packet is interrupted, and the data transmission rate is reduced to avoid congestion, and the packet retransmission process is performed. Therefore, the data transmission time is delayed.

  Thus, in the present invention, on the assumption that packet loss and delay fluctuations occur, packets are sent at a speed faster than the capacity of the line. This can increase the probability that one's own packet enters the buffer when the switch buffer becomes available.

  If a packet loss actually occurs, it must be detected quickly and retransmitted. However, “If a receipt confirmation (Ack) does not come even after a certain period of time has passed since the packet was sent, it is considered a packet loss. In the case of a conventional control method in TCP or the like, there may be a case where the delay time threshold is exceeded when there is a fluctuation in the delay but no packet loss actually occurs. In fact, when the buffer of the switch is full, the amount of delay may exceed several hundred milliseconds, and in severe cases it may exceed 1 second. In addition, in the prior art, most of the devices are controlled so as not to generate a delay, considering that “occurrence of delay” = “increase in the degree of congestion” = “increase in the probability of occurrence of packet loss”.

  On the other hand, in the present invention, communication is controlled on the assumption that packet loss and delay occur, and as a method that does not cause a problem no matter how much fluctuation or delay occurs, “acknowledgment confirmation after continuous transmission of packets” A control method is adopted in which a packet that has been transmitted before (Ack) is returned but has not been acknowledged is regarded as a packet loss. This is a control method that is different from the conventional control method in that it does not schedule a time when the packet receipt confirmation is returned. However, in actuality, there is a case where the packet arrives in a reorder, and therefore it is preferable to give some play to the time when the packet loss is determined. As a result, a packet that has already been received on the receiving side is almost never received again, and very efficient transfer is possible.

  In addition, this high-speed transfer protocol uses up the capacity of the line, so there is no problem if it is a line that you can occupy. However, if the line is shared with others, problems may occur. . Therefore, it is preferable to be able to specify transfer efficiency. For example, when 70% is designated, transfer is performed using up to 70% of the capacity of the line.

  To do this, periodically and instantaneously (for example, 1 second in 10 seconds), the packet capacity is thrown at a high speed in order to measure the capacity of the line, and the rate obtained by multiplying the obtained rate information by the transfer efficiency is set to the normal rate. Control as the maximum rate. This momentarily compresses the line, but other communication is not interrupted because the line is free at other times.

  Furthermore, it is preferable to perform data transfer and control with only one UDP port for the server. As a result, even if the client or server is a NAT environment, data can be transferred without any problem.

  Next, a multi-site distribution process using a data transmission method according to an embodiment of the present invention will be described.

  FIG. 7 is a diagram showing an architecture of a multi-site distribution system 80 using a data transmission method according to an embodiment of the present invention. The multi-site distribution system is configured by connecting a transmission-side device 10, a reception-side device 20, and a plurality of transmission / reception devices 70 via a network N.

  Since the transmission side apparatus 10, the reception side apparatus 20, and the network N have the same configuration as the above-described example, the details are omitted. The transmission / reception device 70 is configured to include the function of the transmission side device 10 and the function of the reception side device 20. A high-speed data transmission method according to the present invention is used between the transmission side device 10 (including the transmission side device 10 included in the transmission / reception device 70) and the reception side device 20 (including the reception side device 20 included in the transmission / reception device 70). Multi-site distribution processing is realized by controlling communication and connecting them in series in a daisy chain.

  FIG. 8 is a block diagram showing a functional configuration of the transmission side device 10, the reception side device 20, and the transmission / reception device 70 including these according to an embodiment of the present invention.

  As shown in the figure, the transmission / reception device 70 includes a reception-side device 20 and a transmission-side device 10 in one device. Then, the data packet received by the packet reception module 21 of the reception side device 20 is transferred to the packet transmission module 12 of the transmission side device 10 in the same device as it is. In addition, the functional configurations of the transmission side device 10 and the reception side device 20 are the same as those in the above-described embodiment.

  FIG. 9 is a flowchart showing an outline of the multi-site distribution process in one embodiment of the present invention. In this embodiment, it is assumed that distribution is performed from the A site to the C site via the B site. This figure is only an example, and there is actually no limit on the number of bases.

  First, the A site starts data transfer to the B site using the above-described high-speed data transfer protocol (S91).

  The site B performs the same processing as that of the reception side device 20 in the above-described high-speed data transmission, and also functions as the transmission side device 10, and transfers the data packet received from the site A to the site C (S92). However, when the B site has received a packet that has already been received, the transfer to the C site is not performed. In the same way as the transmitting side device 10 and the receiving side device 20 in the high-speed data transmission described above, between the B site and the C site, when packet loss occurs in the route, retransmission processing is performed from the B site. Even when the number of bases is large, the number of bases corresponding to the above-mentioned base B only increases, and the overall efficiency hardly changes.

  Thus, on the premise of the transmission / reception device 70 that has the functions of the above-described reception-side device 20 and the transmission-side device 10 and can perform reception and transmission by the above-described data transmission method almost simultaneously, it is connected between these bases. By transferring data to the network, high-speed, almost simultaneous data transmission to multiple sites is possible. In addition, in the case of a full-duplex line network such as an optical fiber, both the upper and lower bands can be used. In conventional technologies and products, transfer is handled in units of files, so if one file transfer is not completed, the next transfer cannot be performed, or TCP is used, so the transfer rate is reduced due to packet loss and delay fluctuations. Most of them deteriorated, but this multi-site distribution method assumes that the above high-speed data transmission control protocol and each base are connected to the same level of line, and the server The data received at is transferred as it is to the next server. If the line is vertically symmetrical, reception and transmission can be performed at the same time, so the efficiency is hardly reduced. Thereby, compared with the case of transferring to a plurality of bases with only one facing, it is possible to transfer to a plurality of bases at high speed in almost the same time.

  As described above in detail, the present invention relates to a protocol and a control method for transferring data from a base to a base at high speed by using an IP communication network such as the Internet to make full use of the capacity of the line. According to the present invention, stable data transmission can be achieved with little influence even on a line where packet loss occurs frequently.

  Specifically, it is a control method that enables high-speed data transmission while ensuring reliability using a protocol such as UDP that does not require an Ack response, and the embodiment of the present invention further increases its efficiency. It is a control method that enables high-speed data transmission by using up to the full capacity of the line, without being affected by the line speed and line quality, and without any special setting by the user.

  In addition, by applying this data transmission system, packets can be relayed from one base to multiple bases in a daisy chain, enabling simultaneous transmission of data. According to the present embodiment, a special line is not necessary, and high-speed simultaneous transfer to a plurality of bases is possible after using up to the capacity of the line by using optical fiber broadband represented by general B FLET'S. Yes.

  The present invention is not limited to the above-described embodiment, and can be implemented in various other forms without departing from the gist of the present invention. For this reason, the said embodiment is only a mere illustration in all points, and is not interpreted limitedly. For example, the above-described processing steps can be executed in any order or in parallel as long as there is no contradiction in the processing contents.

DESCRIPTION OF SYMBOLS 1 ... Data transmission system, 10 ... Transmission side apparatus, 11 ... Transmission time recording module, 12 ... Packet transmission module, 13 ... Transmission rate adjustment module, 14 ... Receipt confirmation reception module, 15 ... Retransmission determination module, 20 ... Reception side apparatus , 21 ... Packet reception module, 22 ... Reception packet number recording module, 23 ... Receipt confirmation transmission module, 24 ... Past receipt confirmation information storage module, 25 ... Sort processing module, 26 ... Reception rate calculation module, 27 ... Timer, 70 ... Transceiver, 80 ... Multi-site distribution system

Claims (26)

A method of transmitting data from a transmission side device to a reception side device via a packet communication network, wherein the transmission side device comprises:
A first step of continuously sending a plurality of packets to the receiving side device at a speed faster than a line capacity of the packet communication network ;
A second step of receiving an acknowledgment sent from the receiving device indicating that the receiving device has received at least some of the plurality of packets;
A third step of retransmitting a packet that has been sent before a packet that has been confirmed to be received by the receiving device by the receipt confirmation and that has not received a receipt confirmation;
A data transmission method comprising: In the data transmission method, the transmitting device further includes:
  A transmission rate adjustment step for adjusting the transmission rate so that the rate at which the packets are continuously transmitted is faster than the bit rate information calculated based on the packets received by the receiving side device.
A data transmission method according to claim 1. The third step is a packet sent a predetermined time or more before the sending time of the packet sent most recently among the packets confirmed to be received by the receiving device by the receipt confirmation; and The data transmission method according to claim 1 or 2 , wherein a packet for which an acknowledgment has not been received is retransmitted. The first step, when sending a packet, one of the claims 1 to 3, characterized in that it comprises the step of recording the packet in association with transmission time of the identification information capable of identifying and the packet data transmission method according to any. 5. The data transmission method according to claim 4 , wherein the receipt confirmation includes identification information of a packet received by the receiving apparatus. 6. The data transmission method according to claim 5 , wherein the receipt confirmation includes identification information included in a past receipt confirmation. A transmission-side device that transmits data to a reception-side device via a packet communication network,
A packet sending module for continuously sending a plurality of packets to a receiving side device at a speed faster than the line capacity of the packet communication network ;
A receipt confirmation receiving module that receives a receipt confirmation sent from the receiving apparatus and indicating that the receiving apparatus has received at least some of the plurality of packets;
A retransmission determination module that retransmits a packet that has been sent before the packet that has been confirmed to be received by the receiving device by the receipt confirmation and that has not received the receipt confirmation;
A transmission-side device comprising:   The transmitting device further includes:
  A transmission rate adjustment module that adjusts the transmission rate so that the rate at which the packets are continuously transmitted is faster than the bit rate information calculated based on the packets received by the receiving side device.
The transmission side apparatus according to claim 7. The retransmission determination module is a packet transmitted a predetermined time or more before the transmission time of the most recently transmitted packet among the packets confirmed to be received by the reception side device by the reception confirmation, and 9. The transmission side apparatus according to claim 7 , wherein a packet for which confirmation has not been received is retransmitted. In a data transmission system comprising a transmission side device and a reception side device and transmitting data via a packet communication network,
The transmitting device is:
A packet sending module for continuously sending a plurality of packets to a receiving side device at a speed faster than the line capacity of the packet communication network ;
A receipt confirmation receiving module that receives a receipt confirmation sent from the receiving apparatus and indicating that the receiving apparatus has received at least some of the plurality of packets;
A retransmission determination module that retransmits a packet that has been sent before the packet that has been confirmed to be received by the receiving device by the receipt confirmation and that has not received the receipt confirmation;
With
The receiving side device
A receipt confirmation sending module for sending a receipt confirmation of a packet received from the sending device;
A data transmission system characterized by that. In the data transmission system, the transmitting device further includes:
  A transmission rate adjustment module that adjusts the transmission rate so that the rate at which the packets are continuously transmitted is faster than the bit rate information calculated based on the packets received by the receiving side device.
The data transmission system according to claim 10. The retransmission determination module is a packet transmitted a predetermined time or more before the transmission time of the most recently transmitted packet among the packets confirmed to be received by the reception side device by the reception confirmation, and 12. The data transmission system according to claim 10 , wherein a packet for which confirmation has not been received is retransmitted.   The program for making a computer perform the data transmission method in any one of Claims 1 thru | or 6.   A computer-readable recording medium on which the program according to claim 13 is recorded.   Data transmission between the plurality of transmission / reception devices is performed almost simultaneously by performing data transmission between the plurality of transmission / reception devices capable of data transmission / reception by the data transmission method according to any one of claims 1 to 6. The data transfer method characterized by performing. A method of transferring data received from one device to another device via a packet communication network,
A first step of receiving a plurality of packets sent from the one device at a speed faster than a line capacity of the packet communication network ;
A second step of sending the received plurality of packets to the other device;
A third step of receiving an acknowledgment sent from the other device indicating that the other device has received at least some of the plurality of packets;
A fourth step of retransmitting a packet that has been sent before the packet that has been confirmed to be received by the other device by the receipt confirmation and that has not received the receipt confirmation;
A data transfer method comprising: In the data transfer method, the one apparatus further includes:
  A transmission rate adjustment step for adjusting the transmission rate so that the rate at which the packets are continuously transmitted is faster than the bit rate information calculated based on the packets received by the receiving side device.
The data transfer method according to claim 16. The data transfer method according to claim 16 or 17 , further comprising a fifth step of transmitting a receipt confirmation of a packet received from the one device. The fourth step is a packet sent a predetermined time or more before the sending time of the packet sent most recently among the packets confirmed to be received by the other device by the receipt confirmation; and The data transfer method according to any one of claims 16 to 18, wherein a packet for which an acknowledgment has not been received is retransmitted. A transmission / reception device that transfers data received from one device to another device via a packet communication network,
A packet receiving module for receiving a packet transmitted from the one device at a speed faster than a line capacity of the packet communication network ;
A packet transmission module for transmitting the received packet to the other device;
An acknowledgment receiving module that receives an acknowledgment sent from the other device and indicating that the other device has received at least a part of the transmitted packet;
A retransmission determination module that retransmits a packet that has been sent before a packet that has been confirmed to be received by the other device by the receipt confirmation and that has not received the receipt confirmation;
A transmission / reception device comprising: In the transmitting / receiving device, the one device is
  A transmission rate adjustment module that adjusts the transmission rate so that the rate at which the packets are continuously transmitted is faster than the bit rate information calculated based on the packets received by the receiving side device.
The transmitting / receiving apparatus according to claim 20. The transmission / reception apparatus according to claim 20 or 21 , further comprising an acknowledgment transmission module that transmits an acknowledgment of a packet received from the one apparatus. The retransmission determination module is a packet that has been sent a predetermined time or more before the sending time of the most recently sent packet among the packets that have been confirmed to be received by the other device by the receipt confirmation, and 23. The transmitting / receiving apparatus according to claim 20 , wherein a packet for which confirmation has not been received is retransmitted.   A plurality of the transmission / reception devices according to any one of claims 20 to 23 are provided, and data transmission is performed between the plurality of transmission / reception devices at approximately the same time by performing data transmission between the plurality of transmission / reception devices. A data transfer system characterized by performing.   A program for causing a computer to execute the data transfer method according to claim 16.   The computer-readable recording medium which recorded the program of Claim 25.

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