Data transmission system and system switching program

Abstract

To solve a problem of a conventional data transmission system having complicated configuration of system switching processing.SOLUTION: A data transmission system in the present invention includes: a first transmission device 10 for periodically transmitting data to a receiving device 30 which receives the data; and a second transmission device 20 which periodically transmits data to the receiving device 30 exclusively with respect to the first transmission device 10. In system switching processing to switch the transmission device for the data, the first transmission device 10 transmits, when stopping periodic data transmission, data to be transmitted immediately before the transmission stop via the second transmission device 20, and transfers transmission data to be transmitted and transmission control information regarding transmission intervals to the second transmission device 20. The second transmission device 20 transmits the data to be transmitted provided from the first transmission device 10, and starts subsequent periodic data transmission on the basis of the transmission data and the transmission control information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a data transmission system and a system switching program, and more particularly to a data transmission system having a main device and a redundant device that provides redundancy to the main device, and a system switching program.

Background Art

[0002] There is a data transmission system that constructs a redundant configuration using an operation system transmission device that exclusively performs data transmission and a standby system transmission device. For example, an RTP (Real-time Transport Protocol) server is an example of such a data transmission system. In the data transmission system, a system switch from the operation system transmission device to the standby system transmission device occurs. At this time, in the data transmission system, it is necessary to execute the system switch without interrupting regular data transmission. Therefore, a technique related to system switching in a data transmission system having such a redundant configuration is disclosed in Patent Document 1.

[0003] The seamless device switching system described in Patent Document 1 includes means for supplying absolute time information from a clock device to each communication device for time synchronization, means for transmitting a packet with a packet output time given from a communication device upstream of an intermediate communication device, calculating the packet output timing in the intermediate communication device from the arrival time of a packet transmitted through a long route transmission path in the intermediate communication device and the packet output time given to the packet, and notifying the upstream communication device of the packet output timing from the intermediate communication device, and means for notifying information on the packet output timing to the intermediate communication device and the communication device to be updated from the upstream communication device, and performing the switch while holding the information on the packet output timing in the intermediate communication device and the communication device to be updated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the seamless device switching system described in Patent Document 1, it is necessary to synchronize the time among a plurality of transmission devices based on absolute time information, it is necessary to connect the devices through two routes, namely, a long route and a short route, and it is necessary to calculate the packet output timing in each device. Thus, the configuration and processing necessary for synchronization among the devices are complicated, and there is a problem of poor maintainability.

Means for Solving the Problems

[0006] One aspect of the data transmission system according to the present invention includes a first transmission device that periodically transmits the data to a receiving device that receives the data, and a second transmission device that exclusively performs the periodic transmission of the data to the receiving device with respect to the first transmission device. In the system switching process of switching the data transmission device, when the first transmission device stops the periodic transmission of the data, the first transmission device transmits the data to be transmitted immediately before the stop via the second transmission device, and passes transmission control information, which is information regarding the transmission data to be transmitted and the transmission interval, to the second transmission device. The second transmission device transmits the data to be transmitted provided by the first transmission device, and starts the subsequent periodic transmission of the data based on the transmission data and the transmission control information.

[0007] One aspect of the system switching program according to the present invention is a system switching program executed in arithmetic units provided in a first transmission device that periodically transmits the data to a reception device that receives the data and a second transmission device that exclusively performs the periodic transmission of the data to the reception device, in a data transmission system having the first transmission device and the second transmission device. In the system switching process of switching the transmission device that transmits the data to the reception device, when the first transmission device stops the periodic transmission of the data, it transmits the data to be transmitted immediately before the stop via the second transmission device, and causes the second transmission device to transmit transmission control information, which is information regarding the transmission data to be transmitted and the transmission interval, and the second transmission device transmits the data of the transmission target provided from the first transmission device, and based on the transmission data and the transmission control information, starts the subsequent periodic transmission of the data.

Effect of the Invention

[0008] According to the data transmission system and the system switching program of the present invention, it is possible to execute system switching while preventing failures such as buffer underruns and reception timeouts on the reception device side with a simple configuration.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a block diagram of a data transmission system according to Embodiment 1. As shown in FIG. 1, the data transmission system 1 according to Embodiment 1 includes a first transmission device (for example, an operation system transmission device 10), a second transmission device (for example, a standby system transmission device 20), and a reception device 30. In the data transmission system 1, the operation system transmission device 10 and the reception device 30, and the operation system transmission device 10 and the standby system transmission device 20 are communicably connected via a network N1, respectively. Further, in the data transmission system 1, the operation system transmission device 10 and the standby system transmission device 20 are communicably connected via a network N2. In the example shown in FIG. 1, the network N1 connecting the transmission device and the reception device and the network N2 connecting between the transmission devices are shown as independent networks, but the operation system transmission device 10, the standby system transmission device 20, and the reception device 30 may be connected to each other only by the network N1. Note that by providing the networks N1 and N2 individually, it is possible to operate a data transmission system having a redundant configuration more stably.

[0011] The operation system transmission device 10 and the standby system transmission device 20 have the same configuration for the redundant configuration function, but may have different parts for the parts that do not form a redundant configuration. And the data transmission system 1 according to the first embodiment periodically transmits preset data. At this time, in the data transmission system 1 according to the first embodiment, the data transmission is executed by exclusively enabling the periodic data transmission function of the operation system transmission device 10 and the standby system transmission device 20. Also, the data transmission system 1 according to the first embodiment has one of the characteristics in the operation when switching the device to be enabled between the operation system transmission device 10 and the standby system transmission device 20. In the following description, a packet signal is taken as an example of the data periodically transmitted by the operation system transmission device 10 and the standby system transmission device 20, but the data to be transmitted is not limited to the packet signal.

[0012] More specifically, in the data transmission system 1 according to the first embodiment, there are a first transmission device (for example, the operation system transmission device 10) that periodically transmits data to the reception device 30 that receives the data, and a second transmission device (for example, the standby system transmission device 20) that exclusively performs the periodic data transmission to the reception device 30 with respect to the operation system transmission device 10. And in the system switching process of switching the data transmission device in the data transmission system 1 according to the first embodiment, when the operation system transmission device 10 stops the periodic data transmission, the data to be transmitted immediately before the stop is transmitted via the standby system transmission device 20, and the transmission control information, which is information regarding the transmission target transmission data and the transmission interval, is passed to the standby system transmission device 20. Also, the data transmission system 1 has the standby system transmission device 20 transmit the data of the transmission target provided from the operation system transmission device 10, and start the subsequent periodic data transmission based on the transmission data and the transmission control information provided from the operation system transmission device 10.

[0013] The operation system transmission device 10 includes a first receiving unit (e.g., receiving unit 11), a first transmitting unit (e.g., transmitting unit 12), and a first redundancy control unit (e.g., redundancy control unit 13). The receiving unit 11 receives data transmitted from other devices via the network N1 and the network N2. The transmitting unit 12 transmits data to be transmitted to other devices via the network N1 and the network N2. The redundancy control unit 13 performs control for the operation system transmission device 10 and the standby system transmission device 20 to transmit data exclusively. The redundancy control unit 13 is connected to the receiving unit 11 and the transmitting unit 12 by internal wiring, and controls the receiving unit 11 and the transmitting unit 12 to execute system switching processing between the operation system transmission device 10 and the standby system transmission device 20.

[0014] The receiving unit 11 includes a first receiving processing unit (e.g., receiving processing unit 14). The receiving processing unit 14 receives data transmitted via the network N1 or the network N2, interprets the packet content of the received data, and transmits it to a subsequent processing unit (e.g., transmitting unit 12).

[0015] The transmitting unit 12 includes a first transmitting processing unit (e.g., transmitting processing unit 15), a first transmission data storage area (e.g., transmission data storage area 16), and a first transmission timing control unit (e.g., transmission timing control unit 17). The transmitting processing unit 15 sends the data packetized from the transmission data generated by the transmission timing control unit 17 to the network N1 or N2. The transmission data storage area 16 is, for example, a non-volatile memory or a volatile memory provided in a computer, and stores data to be transmitted (e.g., transmission target data). Also, transmission control information for designating the transmission timing of data is held in the transmission timing control unit 17. Then, the transmission timing control unit 17 generates data to be transmitted by the transmission processing unit 15 at intervals specified by the transmission control information. Also, in the system switching process, the transmission timing control unit 17 transmits the transmission control information to the transmission processing unit 15 as information to be transmitted.

[0016] The standby transmission device 20 includes a second receiving unit (for example, receiving unit 21), a second transmitting unit (for example, transmitting unit 22), and a second redundancy control unit (for example, redundancy control unit 23). The receiving unit 21 receives data transmitted from other devices via the network N1 and the network N2. The transmitting unit 22 transmits data to be transmitted to other devices via the network N1 and the network N2. The redundancy control unit 23 performs control for the operation system transmission device 10 and the standby transmission device 20 to transmit data exclusively. The redundancy control unit 23 is connected to the receiving unit 21 and the transmitting unit 22 by internal wiring, and controls the receiving unit 21 and the transmitting unit 22 to execute system switching processing between the operation system transmission device 10 and the standby transmission device 20.

[0017] The receiving unit 21 includes a second receiving processing unit (for example, receiving processing unit 24). The receiving processing unit 24 receives data transmitted via the network N1 or the network N2, interprets the packet content of the received data, and transmits it to a subsequent processing unit (for example, the transmitting unit 22).

[0018] The transmitting unit 22 includes a second transmitting processing unit (for example, transmitting processing unit 25), a second transmission data storage area (for example, transmission data storage area 26), and a second transmission timing control unit (for example, transmission timing control unit 27). The transmitting processing unit 25 sends the data packetized from the transmission data generated by the transmission timing control unit 27 to the network N1 or N2. The transmission data storage area 26 is, for example, a non-volatile memory or a volatile memory provided in a computer, and stores data to be transmitted (for example, transmission target data). Also, transmission control information for designating the transmission timing of data is held in the transmission timing control unit 27. Then, the transmission timing control unit 27 generates data to be transmitted by the transmission processing unit 25 at intervals specified by the transmission control information. Also, in the system switching process, the transmission timing control unit 27 transmits the transmission control information to the transmission processing unit 25 as information to be transmitted.

[0019] The configurations of the above-described operation system transmission device 10 and the standby system transmission device 20 may be realized by hardware to implement the functions described above, or may be realized by a program executed by an arithmetic unit provided on the operation system transmission device 10 and the standby system transmission device 20, or may also be realized by combining hardware and software. In the following description, an example in which the system switching process is realized by a system switching program will be described. Further, in the following description, the system switching process of the operation of the data transmission system 1 according to the first embodiment will be described, but the data transmission system 1 also performs other operations.

[0020] First, with reference to FIGS. 2 to 4, the data flow in the system switching process of the data transmission system 1 will be described. Note that in FIG. 4, only the functional blocks operating in packet transmission are shown, and the paths enabled in packet transmission are shown by thick lines.

[0021] FIG. 2 shows a block diagram for explaining the flow of packet transmission processing before system switching of the data transmission system 1 according to the first embodiment. As shown in FIG. 2, in the state before the system switching process in which the data transmission system 1 according to the first embodiment activates the operation system transmission device 10, the transmission unit 12 of the operation system transmission device 10 mainly operates, and the standby system transmission device 20 is in a state where the data transmission process has stopped. In the state shown in FIG. 2, the transmission timing control unit 17 of the transmission unit 12 reads the transmission target data from the transmission data storage area 16 and periodically transmits packets to the receiving device 30 via the transmission processing unit 15.

[0022] Next, a block diagram for explaining the flow of packet transmission processing during system switching of the data transmission system 1 according to Embodiment 1 is shown in FIG. 3. As shown in FIG. 3, in the data transmission system 1 during system switching processing, the transmission timing control unit 17 of the operation system transmission device 10 transmits the transmission data stored in the transmission data storage area 16 and the transmission control information in the transmission timing control unit 17 to the transmission processing unit 15. The transmission processing unit 15 packetizes the transmission data and the transmission control information and transmits them to the standby system transmission device 20 via the network N2. Then, the reception processing unit 24 of the standby system transmission device 20 that has received the data transmitted from the operation system transmission device 10 analyzes the received packet, transmits the transmission data to the reception device 30 via the transmission processing unit 25, and stores it in the transmission data storage area 26. Further, the reception processing unit 24 analyzes the received packet and transmits the transmission control information to the transmission timing control unit 27. Here, the transmission timing control unit 27 learns the transmission interval for performing periodic data transmission based on the received transmission control information.

[0023] Next, a block diagram for explaining the flow of packet transmission processing after system switching of the data transmission system 1 according to Embodiment 1 is shown in FIG. 4. As shown in FIG. 4, in the state after the system switching process in which the data transmission system 1 according to Embodiment 1 has activated the standby system transmission device 20, the standby system transmission device 20 mainly operates, and the operation system transmission device 10 is in a state of stopping the data transmission processing. In the state shown in FIG. 4, the transmission timing control unit 27 of the transmission unit 22 reads the transmission target data from the transmission data storage area 26 and periodically transmits packets to the reception device 30 via the transmission processing unit 25.

[0024] As described above, in the data transmission system 1 according to the first embodiment, a switching process is performed to switch the system that periodically performs data transmission between the operation system transmission device 10 and the standby system transmission device 20. Hereinafter, the detailed process flow of the system switching process in the data transmission system 1 will be described. Therefore, FIG. 5 shows a sequence diagram for explaining the system switching procedure of the data transmission system according to the first embodiment. Note that the sequence diagram shown in FIG. 5 shows the process when performing a system switching process for switching the device that periodically performs data transmission from the operation system transmission device 10 to the standby system transmission device 20.

[0025] As shown in FIG. 5, in the data transmission system 1 according to the first embodiment, the system switching process is started during a time period when data transmission is not performed while the operation system transmission device 10 is performing periodic data communication (step S1). Then, when starting the system switching process, the redundancy control unit 13 of the operation system transmission device 10 transmits a switching preparation instruction to the redundancy control unit 23 of the standby system transmission device 20 (step S2). Note that the switching preparation instruction is sent by the redundancy control unit 13 to the transmission processing unit 15, and the transmission processing unit 15 transmits it to the reception processing unit 24 of the standby system transmission device 20 via the network N2. Further, the reception processing unit 24 transmits the received switching preparation instruction to the redundancy control unit 23. This switching preparation instruction is defined as a signal that can always be received whether the reception processing unit 24 is in a state of executing packet reception processing or in a stopped state.

[0026] Then, the redundancy control unit 23 that has received the switching preparation instruction transmits a reception processing start instruction to the reception processing unit 24 (step S3). Then, in response to the reception processing unit 24 having received the reception processing start instruction via reception processing, the reception processing unit 24 notifies the redundancy control unit 23 that it has started operating (step S4). Then, the redundancy control unit 23 that has recognized the start of operation of the reception processing unit 24 notifies the redundancy control unit 13 of the completion notification of system switching preparation (step S5). Note that the completion notification of switching preparation is sent by the redundancy control unit 23 sending a transmission instruction to the transmission processing unit 25, and the transmission processing unit 25 transmits it to the reception processing unit 14 of the operation system transmission device 10 via the network N2. Further, the reception processing unit 14 transmits the received completion notification of switching preparation to the redundancy control unit 13.

[0027] Thereafter, the redundancy control unit 13 instructs the transmission unit 12 to change the packet transmission destination (step S6). As a result, in the transmission unit 12, the transmission processing unit 15 changes the packet transmission destination to the standby system transmission device 20 (step S7). Thereafter, when the regular packet transmission time arrives, the transmission timing control unit 17 transmits the transmission data and the transmission control information to the transmission processing unit 15. Then, the transmission processing unit 15 packetizes the received transmission data and transmission control information and transmits them to the reception processing unit 24 of the standby system transmission device 20 (step S8).

[0028] Thereafter, the reception processing unit 24 provides the received packet to the transmission unit 22 (step S9). Then, in the transmission unit 22, the transmission processing unit 25 outputs the packet signal of the transmission data to the receiving device 30, stores the transmission data in the transmission data storage area 26, and stores the transmission control information in the transmission timing control unit 27 (step S10).

[0029] Also, the transmission unit 12 that performed packet transmission in step S8 notifies the redundancy control unit 13 that the packet transmission has been completed (step S11). Then, the redundancy control unit 13 that recognizes that the packet transmission in step S8 has been completed issues a system switching instruction to the redundancy control unit 23 of the standby transmission device 20 (step S12). The redundancy control unit 23 that receives the switching instruction issues a rendezvous instruction for transmission data and transmission control information to the transmission unit 22 (step S13). Thereafter, the transmission unit 22 spontaneously starts periodic data transmission based on the transmission data stored in the transmission data storage area 26 and the transmission control information stored in the transmission timing control unit 27 (step S14).

[0030] Then, in response to the spontaneous start of periodic data transmission, the transmission unit 22 notifies the redundancy control unit 23 that the rendezvous of transmission data and transmission control information has been completed (step S16). Then, the redundancy control unit 23 that receives the notification that the rendezvous of transmission data and transmission control information has been completed notifies the redundancy control unit 13 that the system switching has been completed (step S17). The redundancy control unit 13 that receives the notification that the system switching has been completed instructs the transmission unit 12 to stop periodic transmission (step S18). Also, the transmission unit 12 stops operating upon receiving the instruction to stop periodic transmission (step S19). Note that, in response to the spontaneous start of periodic data transmission, the reception unit 21 discards the packet received in step S9 (step S15).

[0031] From the above description, in the data transmission system 1 according to Embodiment 1, when the timing of periodic data transmission arrives after the system switching process is started, the transmission data is transmitted from the active system transmission device 10 to the standby system transmission device 20, and the transmission data to be periodically transmitted from the standby system transmission device 20 is transmitted from the standby system transmission device 20 to the reception device 30. Thereby, in the data transmission system 1 according to Embodiment 1, it is possible to prevent a communication failure in which periodic transmission data due to the system switching process is not transmitted.

[0032] In the data transmission system 1 according to Embodiment 1, together with switching the data transmission source to the standby transmission device 20, transmission control information that defines the transmission target data and the transmission interval is transmitted from the operation system transmission device 10 to the standby transmission device 20. Thereby, in the data transmission system 1 according to Embodiment 1, the standby transmission device 20 after receiving the information can periodically transmit the transmission data under the same conditions as the operation system transmission device 10.

[0033] In this way, the data transmission system 1 according to Embodiment 1 can realize a system switching process in which regular data transmission does not occur only by simple information exchange without using a special configuration between the operation system transmission device 10 and the standby transmission device 20.

[0034] Note that the present invention is not limited to the above embodiments, and can be appropriately changed without departing from the gist.

Explanation of Reference Numerals

[0035] 1 Data transmission system 10 Operation system transmission device 11, 21 Receiver 12, 22 Transmitter 13, 23 Redundancy control unit 14, 24 Reception processing unit 15, 25 Transmission processing unit 16, 26 Transmission data storage area 17, 27 Transmission timing control unit 20 Standby transmission device 30 Receiver N1, N2 Network

Claims

1. A first transmission device that periodically transmits the data to a receiving device that receives the data, and a second transmission device that exclusively performs the periodic transmission of the data to the receiving device, and having in the system switching process for switching the data transmission device, when the first transmission device stops the periodic transmission of the data, the first transmission device transmits the data to be transmitted immediately before the stop via the second transmission device, and passes transmission control information, which is information on the transmission data and the transmission interval to be transmitted, to the second transmission device, the second transmission device transmits the data of the transmission target provided from the first transmission device, and starts the subsequent periodic transmission of the data based on the transmission data and the transmission control information, a data transmission system.

2. The first transmission device has a first transmission unit that transmits the data, a first reception unit that receives the data, and a first redundancy control unit that performs control for the first transmission device and the second transmission device to exclusively transmit the data, and the second transmission device has a second transmission unit that transmits the data, a second reception unit that receives the data, and a second redundancy control unit that performs control for the first transmission device and the second transmission device to exclusively transmit the data, the data transmission system according to claim 1.

3. The second redundancy control unit in response to receiving a system switching preparation instruction from the first redundancy control unit, instructs the second reception unit to start reception processing, and in response to receiving a notification that the reception processing has been started from the second reception unit, returns a system switching preparation completion notification to the first redundancy control unit, the first redundancy control unit in response to receiving the system switching preparation completion notification, causes the first transmission unit to transmit the data to the second reception unit, the second reception unit causes the data transmitted by the first transmission unit to be transmitted via the second transmission unit, the data transmission system according to claim 2.

4. The first transmission unit has a first transmission processing unit that sends the data to a network, a first transmission data storage unit that stores the data of the transmission target, and a first transmission timing control unit that reads the data from the first transmission data storage unit and generates the data to be transmitted by the first transmission processing unit at intervals specified by the transmission control information, The second transmission unit includes: a second transmission processing unit that sends the data to a network; a second transmission data storage unit that stores the data to be transmitted; a second transmission timing control unit that reads the data from the second transmission data storage unit and generates the data to be transmitted by the second transmission processing unit at intervals specified by the transmission control information. The data transmission system according to claim 2 or 3.

5. In the system switching process, the first redundancy control unit instructs the first transmission timing control unit to generate the data so as to transmit the data stored in the first transmission data storage unit and the transmission control information set in the first transmission timing control unit from the first transmission unit to the second transmission unit; the second reception unit stores the data to be transmitted included in the data received from the first transmission unit in the second transmission data storage unit, and distributes information so as to set the transmission control information included in the data received from the first transmission unit in the second transmission timing control unit. The data transmission system according to claim 4.

6. After the transmission control information is set, the second transmission timing control unit learns the transmission interval of the data, and starts regular transmission of the data after the learning is completed. The data transmission system according to claim 4 or 5.

7. In response to receiving a learning completion notification from the second transmission timing control unit, the second redundancy control unit transmits a switching process completion notification to the first transmission device. In response to receiving the switching process completion notification, the first transmission device stops regular transmission of the data. The data transmission system according to claim 6.

8. A system switching program executed in arithmetic units respectively provided in a first transmission device that regularly transmits data to a receiving device that receives the data and a second transmission device that exclusively performs regular transmission of the data to the receiving device instead of the first transmission device. In the system switching process for switching the transmission device that transmits the data to the receiving device, In the system switching process for switching the transmission device that transmits the data to the receiving device, When the first transmission device stops the periodic transmission of the data, it transmits the data to be transmitted immediately before the stop via the second transmission device, and causes the second transmission device to transmit transmission control information, which is information regarding the transmission data to be transmitted and the transmission interval. A system switching program that causes the second transmission device to transmit the data to be transmitted provided by the first transmission device and to start the subsequent periodic transmission of the data based on the transmission data and the transmission control information.

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