Communication systems and communication methods

Abstract

To make the internal state of an I / F module on an active side identical to the internal state of an I / F module on a backup side even if a communication abnormality occurs between the I / F module on the active side and a subordinate module.SOLUTION: A communication system 10 has an active-side I / F module 20 and a backup-side I / F module 30. The active-side I / F module 20 includes a transmitting unit 22a, and the backup-side I / F module 30 includes a monitoring unit 32a and a response processing unit 32b. The transmitting unit 22a transmits a predetermined notification to make the internal state of the active-side I / F module 20 identical to the internal state of the backup-side I / F module 30. The monitoring unit 32a monitors communication between the active-side I / F module 20 and a subordinate module 40 and receives communication contents. The response processing unit 32b receives and processes a response from the subordinate module 40 to the active-side I / F module 20.SELECTED DRAWING: Figure 2

Description

Technical Field

[0006] , ,

[0001] The present invention relates to a communication system and a communication method.

Background Art

[0002] Conventionally, in computers, communication systems, etc., in order to prevent the system from stopping due to equipment failure, a standby redundant system has always been kept in standby. When a failure occurs in the system, the standby system operates instead, so that the entire system can be operated without stopping. This is known as the standby redundancy method.

[0003] In the standby redundancy method, it is necessary to equalize the data between the active-side module and the backup-side module. There is a technique in which the backup-side I / F (Interface) module monitors all communications between the active-side I / F module and the lower-level modules to make the internal states the same between the two I / F modules (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the above technology, when an abnormality occurs in communication between the active-side I / F module and the lower-level module and the response from the lower-level module cannot be received, the active-side I / F module receives a response to the retransmission of the request, but if the backup-side I / F module has received the response from the first lower-level module, there is a problem that a difference occurs in the internal state.

[0006] Furthermore, if the active I / F module is unable to receive a response to a request retransmission, while the backup I / F module has received a response, the backup I / F module cannot know the state of the active I / F module, resulting in a discrepancy in their internal states. [Means for solving the problem]

[0007] To solve the above-mentioned problems and achieve the objective, the present invention provides a communication system having an operating module and a standby module, wherein the operating module has a transmitting unit that transmits a predetermined notification to make the internal state of the operating module the same as the internal state of the standby module, and the standby module has a monitoring unit that monitors communication between the operating module and a lower module, and a response processing unit that processes responses from the lower module. [Effects of the Invention]

[0008] According to the present invention, even if a communication error occurs between the active I / F module and the subordinate module, the internal state of the active I / F module and the internal state of the backup I / F module can be made identical. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an explanatory diagram showing an overview of the communication system according to the embodiment. [Figure 2] Figure 2 shows an example of the configuration of a communication system according to the embodiment. [Figure 3] Figure 3 shows a specific example of communication processing according to the embodiment. [Figure 4] Figure 4 shows a specific example of communication processing according to the embodiment. [Figure 5] Figure 5 shows a specific example of communication processing according to the embodiment. [Figure 6]Figure 6 shows a specific example of communication processing according to the embodiment. [Figure 7] Figure 7 shows a specific example of communication processing according to the embodiment. [Figure 8] Figure 8 is a flowchart showing the processing procedure according to the embodiment. [Figure 9] Figure 9 is a flowchart showing the processing procedure according to the embodiment. [Figure 10] Figure 10 shows an example of a hardware configuration. [Modes for carrying out the invention]

[0010] The embodiments of the communication system and communication method according to the present application will be described in detail below with reference to the drawings. However, these embodiments do not limit the communication system and communication method according to the present application.

[0011] [1. Example of system configuration] Figure 1 shows the configuration of the communication system according to this embodiment. The system shown in Figure 1 includes a communication system 10, an active I / F module 20, a backup I / F module 30, and a lower-level module 40.

[0012] The communication system 10 includes an active I / F module 20 and a backup I / F module 30. The backup I / F module 30 monitors communication between the active I / F module 20 and the lower-level module 40. The active I / F module 20 and the backup I / F module 30 also process responses from the lower-level module 40. The active I / F module 20 and the backup I / F module 30 communicate with each other in accordance with the process of making their internal states identical.

[0013] The backup-side I / F module 30 monitors the communication between the active-side I / F module 20 and the lower-level module 40. For example, the backup-side I / F module 30 monitors all the communication between the active-side I / F module 20 and the lower-level module 40, and receives requests from the active-side I / F module 20 to the lower-level module 40 and responses from the lower-level module 40 to the active-side I / F module 20.

[0014] Then, the active-side I / F module 20 and the backup-side I / F module 30 each process the received response from the lower-level module 40. For example, the active-side I / F module 20 processes the response sent from the lower-level module 40 for the request to the lower-level module 40, and the backup-side I / F module 30 receives the response sent from the lower-level module 40 to the active-side I / F module 20 through the above-mentioned communication monitoring and processes the received response.

[0015] Also, the active-side I / F module 20 and the backup-side I / F module 30 communicate with each other according to the process of making their internal states the same. For example, when a difference occurs in the reception status of responses between the active-side I / F module 20 and the backup-side I / F module 30 due to a communication abnormality between the active-side I / F module 20 and the lower-level module 40, the active-side I / F module 20 and the backup-side I / F module 30 communicate with each other to make their internal states the same.

[0016] The active-side I / F module 20 and the backup-side I / F module 30 are I / F modules that perform arbitrary processing by communicating with the lower-level module 40, and the lower-level module 40 is a module that can send a response to a request from the active-side I / F module.

[0017] 〔2. Configuration of Communication System 10〕 Next, referring to FIG. 2, the configuration of the communication system 10 shown in FIG. 1 will be described. FIG. 2 is a diagram showing a configuration example of a communication system according to an embodiment. As shown in FIG. 2, the communication system 10 according to the embodiment includes an active-side I / F module 20 and a backup-side I / F module 30.

[0018] The active-side I / F module 20 includes a communication unit 21, a control unit 22, and a storage unit 23, and the backup-side I / F module 30 includes a communication unit 31, a control unit 32, and a storage unit 33. Also, the active-side I / F module 20, the backup-side I / F module 30, and the lower-level module 40 are communicably connected to each other by wire or wirelessly.

[0019] The communication units 21 and 31 are realized by, for example, a NIC (Network Interface Card) or the like. The communication units 21 and 31 are connected to the active-side I / F module 20 or the backup-side I / F module 30 and the lower-level module 40 by wire or wirelessly, and transmit and receive information between the active-side I / F module 20 or the backup-side I / F module 30 and the lower-level module 40.

[0020] The storage units 23 and 33 are realized by, for example, a storage device such as a RAM (Random Access Memory) or a hard disk. The storage units 23 and 33 store data and programs necessary for various processes by the control unit 22 or the control unit 32. And the storage unit 23 of the active-side I / F module 20 has a timeout information storage unit 23a as being closely related to the present invention.

[0021] The timeout information storage unit 23a stores information regarding a response wait timeout notification of the active-side I / F module 20 when a communication failure occurs between the active-side I / F module 20 and the lower-level module 40 described later. For example, the timeout information storage unit 13a stores an arbitrary time N for which the active-side I / F module 20 waits for a response from the lower-level module 40.

[0022] Furthermore, the storage unit 33 of the backup-side I / F module 30, as closely related to the present invention, includes a monitoring information storage unit 33a and a standby information storage unit 33b. The monitoring information storage unit 33a stores information about communication between the active-side I / F module 20 and the lower-level module 40, which is monitored by the monitoring unit 32a described later.

[0023] For example, the monitoring information storage unit 33a stores requests from the active-side I / F module 20 to the lower-level module 40, retransmissions of those requests, and responses from the lower-level module 40 to the active-side I / F module 20, which are received through monitoring by the monitoring unit 32a, which will be described later.

[0024] The standby information storage unit 33b stores the waiting time when the backup-side I / F module 30 processes the response from the lower-level module 40. For example, the standby information storage unit 33b stores the waiting time M from the moment the backup-side I / F module 30 receives the response from the lower-level module 40 until it starts processing it.

[0025] Furthermore, the response waiting time N of the active I / F module 20 and the standby time M of the backup I / F module 30 are assumed to be stored in advance, and the standby time M is set to a value greater than the response waiting time N.

[0026] Control units 22 and 32 are implemented by a CPU (Central Processing Unit) or MPU (Micro Processing Unit), etc., which executes various programs stored in the memory devices within each I / F module using RAM as the working area. Control units 22 and 32 are also implemented by integrated circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field Programmable Gate Arrays).

[0027] The control unit 22 of the active-side I / F module 20 has a transmission unit 22a. The transmission unit 22a transmits a predetermined notification to make the internal state of the module in operation (active side) the same as the internal state of the module in standby (backup side).

[0028] For example, if a communication failure occurs between the active I / F module 20 and the lower-level module 40, the transmitting unit 22a sends a timeout notification to make the internal state of the active I / F module 20 and the internal state of the backup I / F module 30 the same.

[0029] Furthermore, if a module in operation does not receive a response from a lower-level module to a request retransmitted from the operating module, the transmitting unit 22a may send a timeout notification to a module in standby mode.

[0030] For example, if the active I / F module 20 fails to receive a response from the lower-level module 40 to retransmit a request even after a response waiting time N has elapsed, the transmitting unit 22a sends a timeout notification to the backup I / F module 30 to prevent any discrepancies in the internal state caused by the backup I / F module 30 starting response processing.

[0031] The control unit 32 of the backup-side I / F module 30 includes a monitoring unit 32a, a response processing unit 32b, and a switching unit 32c. The monitoring unit 32a monitors communication between the operating module and the lower-level module. The monitoring unit 32a then stores the communication information between the active-side I / F module 20 and the lower-level module 40, received through monitoring, in the monitoring information storage unit 33a.

[0032] For example, the monitoring unit 32a monitors communication between the active I / F module 20 and the lower module 40, receives requests and retransmissions of requests from the active I / F module 20 to the lower module 40, and responses from the lower module 40 to the active I / F module 20, and stores them in the monitoring information storage unit 33a.

[0033] The response processing unit 32b processes responses from lower-level modules. For example, the response processing unit 32b performs the same processing as the active-side I / F module 20 for responses from lower-level modules 40 to the active-side I / F module 20 that are stored in the monitoring information storage unit 33a.

[0034] Furthermore, the response processing unit 32b may, after receiving a response from a lower module, wait for a predetermined time and then process the response from the lower module if the request has not been resent from the operating module to the lower module, or if it has not received a timeout notification from the operating module.

[0035] For example, the response processing unit 32b, after receiving a response from the lower-level module 40 to the active-side I / F module 20, waits for a period of waiting time M stored in the standby information storage unit 33b. If the monitoring information storage unit 33a does not store a retransmission of the request from the active-side I / F module 20 to the lower-level module 40, or if the backup-side I / F module 30 has not received a timeout notification from the active-side I / F module 20, it processes the response from the lower-level module 40.

[0036] Furthermore, if the standby module has received the initial response from the subordinate module and the response from the subordinate module to the request retransmission, but has not received a timeout notification from the operating module, the response processing unit 32b may process the response from the subordinate module to the request retransmission.

[0037] For example, the response processing unit 32b stores the initial response from the lower module 40 to the active-side I / F module 20 and the response to the retransmission of the request in the monitoring information storage unit 33a, and after waiting for a waiting period M from the time the backup-side I / F module 30 receives the response to the retransmission of the request, if the backup-side I / F module 30 has not received a timeout notification from the active-side I / F module 20, it processes the response to the retransmission of the request.

[0038] Since the monitoring information storage unit 33a stores the response to the request retransmission, the active-side I / F module 20 can be determined that it did not receive the initial response from the lower-level module 40, and since it has not received a timeout notification from the active-side I / F module 20, it can be determined that the active-side I / F module 20 has received the response to the request retransmission. Therefore, the backup-side I / F module 30 can prevent discrepancies in its internal state by processing the response to the request retransmission that the active-side I / F module 20 is processing.

[0039] The switching unit 12c switches the standby module to the operating state when the standby module receives a response from a lower-level module and also receives a timeout notification from the operating module.

[0040] For example, if the backup I / F module 30 receives a response from the lower module 40 and also receives a timeout notification from the active I / F module 20, the switching unit 12c determines that there is an abnormality in the communication function of the active I / F module 20, performs an operation state switch and a transmission enable switch, and switches the backup I / F module 30 to the active side.

[0041] [3. Specific Examples of Information Processing] Here, with reference to Figures 3 to 7, specific examples of the processes by the communication system 10 to make the internal state of the active I / F module 20 and the backup I / F module 30 the same will be described. Figures 3 to 7 are diagrams showing specific examples of communication processing according to the embodiment.

[0042] First, let's explain the timeout notification sending process of the active-side I / F module 20. If the active-side I / F module 20 is unable to receive a response from the subordinate module 40 to the retransmission of the request, it sends a timeout notification to the backup-side I / F module 30.

[0043] In the example shown in Figure 3, the active I / F module 20 sends "Request 1" to the subordinate module 40 and waits for a response waiting period N. However, since there is no response from the subordinate module 40, it sends "Request 1 Resend 1". After the request is resent, the active I / F module 20 waits for the same period N, but since it does not receive a response to the resent request either, it sends a timeout notification to the backup I / F module 30. This allows the backup I / F module 30 to know that the active I / F module 20 has not received a response from the subordinate module 40.

[0044] Next, the response processing of the backup-side I / F module 30 will be described. The backup-side I / F module 30 waits for a time M from the moment it receives a response from the lower-level module 40 to the active-side I / F module 20. After that, the backup-side I / F module 30 confirms that it has not received a retransmission of the request from the active-side I / F module 20 to the lower-level module 40, and then processes the received response.

[0045] In the example shown in Figure 4, the backup I / F module 30 waited for the elapsed time M after receiving "Response 1" from the lower-level module 40 to the active-level I / F module 20, but since it did not receive a retransmission of the request from the active-level I / F module 20 to the lower-level module 40, it processes "Response 1". This prevents discrepancies in the internal state because the backup-level I / F module 30 processes only after confirming the reception status of the active-level I / F module 20.

[0046] Furthermore, the backup I / F module 30 waits for the elapsed time M from the moment it receives a response from the lower-level module 40 to the active I / F module 20 in response to the retransmission of the request. After that, the backup I / F module 30 confirms that it has not received a timeout notification from the active I / F module 20 before processing the received response.

[0047] In the example shown in Figure 5, the backup I / F module 30 monitors and receives "Response 1" to "Request 1 Retransmission 1" from the lower-level module 40 to the active I / F module 20, and waits for the elapsed time M. However, since it has not received a timeout notification from the active I / F module 20, it processes "Response 1". This prevents discrepancies in the internal state because the backup I / F module 30 processes only after confirming the reception status of the active I / F module 20.

[0048] Furthermore, if the backup-side I / F module 30 receives both the initial response from the lower-level module 40 to the active-side I / F module 20 and the response to the request retransmission, it processes the response to the request retransmission.

[0049] In the example shown in Figure 6, the backup I / F module 30 monitors and receives "Response 1" from the lower-level module 40 to the active I / F module 20. Subsequently, the active I / F module 20, unable to receive "Response 1" from the lower-level module 40, sends "Request 1 Retransmission 1" to the lower-level module 40. The lower-level module 40 then sends "Response 1 Retransmission 1" to the active I / F module 20 in response to "Request 1 Retransmission 1," and both the active I / F module 20 and the backup I / F module 30 receive "Response 1 Retransmission 1."

[0050] Subsequently, the backup I / F module 30 waited for the elapsed time M, but since it did not receive a timeout notification from the active I / F module 20, it processes "Response 1, Resend 1". As a result, both the active I / F module 20 and the backup I / F module 30 process "Response 1, Resend 1", so there is no difference in their internal states.

[0051] Next, the operation state switching process by the backup-side I / F module 30 will be explained. When the backup-side I / F module 30 receives a response from the lower-level module 40 to the active-side I / F module 20 and a timeout notification, it performs an operation state switch and a transmission enable switch, and switches to the active side.

[0052] In the example shown in Figure 7, the backup I / F module 30 receives "Response 1" and "Response 1 Retransmission 1" from the lower-level module 40 to the active I / F module 20. On the other hand, the active I / F module 20 was unable to receive responses to "Request 1" and "Request 1 Retransmission 1," and therefore sends a timeout notification.

[0053] Upon receiving a timeout notification, the backup I / F module 30 determines that an abnormality has occurred in the communication function of the active I / F module 20 and performs an operation state switch and a transmission enable switch. As a result, the backup I / F module 30 can quickly switch to the active side if an abnormality occurs in the communication function of the active I / F module 20.

[0054] [4. An example of information processing in an information processing device] Next, the communication processing of the communication system 10 will be explained using Figures 8 and 9. Figures 8 and 9 are flowcharts showing the flow of communication processing in the active-side I / F module 20 and the backup-side I / F module 30 according to the embodiment. First, referring to Figure 8, the flow of communication processing in the active-side I / F module 20 will be explained.

[0055] The active I / F module 20 determines, for example, whether or not it can communicate with the lower module 40 (step S101). If the active I / F module 20 can communicate with the lower module 40 (step S101; Yes), it sends a request to the lower module 40 (step S102). On the other hand, if the active I / F module 20 cannot communicate with the lower module 40 (step S101; No), it waits until communication becomes possible.

[0056] Then, the active I / F module 20 receives a response from the lower module 40 (step S103). If the active I / F module 20 has received a response from the lower module 40 (step S103; Yes), it processes the response (step S106). On the other hand, if the active I / F module 20 has not received a response from the lower module 40 (step S103; No), it resends the request to the lower module 40 (step S104).

[0057] Subsequently, the active I / F module 20 receives a response from the lower module 40 (step S105). If the active I / F module 20 receives a response from the lower module 40 (step S105; Yes), it processes the response (step S106). On the other hand, if the active I / F module 20 has not received a response from the lower module 40 (step S105; No), the transmitting unit 22a sends a timeout notification to the backup I / F module 30 (step S107).

[0058] Next, referring to Figure 9, the communication processing in the backup-side I / F module 30 will be described. The monitoring unit 32a receives a response from the lower-level module 40, for example (step S101). If the monitoring unit 32a receives a response from the lower-level module 40 (step S101; Yes), the backup-side I / F module 30 waits for the elapsed time M (step S102). On the other hand, if the monitoring unit 32a has not received a response from the lower-level module 40 (step S101; No), the backup-side I / F module 30 waits until it receives a response.

[0059] Then, the monitoring unit 32a receives a retransmission of the request from the active I / F module 20 to the lower module 40 (step S103). If the monitoring unit 32a receives a retransmission of the request (step S103; Yes), the backup I / F module 30 receives a timeout notification (step S104). On the other hand, if the monitoring unit 32a does not receive a retransmission of the request (step S103; No), the response processing unit 32b processes the response (step S105).

[0060] If the backup-side I / F module 30 receives a timeout notification (step S104; Yes), the switching unit 32c switches to the active side (step S107). On the other hand, if the backup-side I / F module 30 does not receive a timeout notification (step S104; No), the response processing unit 32b processes the response to the retransmission of the request (step S106).

[0061] [5. Effects of the Embodiment] As described above, the communication system 10 according to this embodiment has an active I / F module 20 and a backup I / F module 30. The active I / F module 20 has a transmission unit 22a, and the backup I / F module 30 has a monitoring unit 32a and a response processing unit 32b.

[0062] The transmitting unit 22a transmits a predetermined notification to make the internal state of the active I / F module 20 and the backup I / F module 30 the same. The monitoring unit 32a monitors the communication between the active I / F module 20 and the lower-level module 40 and receives the communication content. The response processing unit 32b processes the response received from the lower-level module 40 to the active I / F module 20.

[0063] As a result, the communication system 10 has the effect of being able to make the internal state of the active I / F module and the backup I / F module the same even if a communication abnormality occurs between the active I / F module 20 and the lower module 40.

[0064] Furthermore, if the active I / F module 20 does not receive a response to the retransmission of a request from the lower-level module 40, the transmitting unit 22a of the active I / F module 20 sends a timeout notification to the backup I / F module 30.

[0065] As a result, even if a communication failure occurs between the active I / F module 20 and the lower-level module 40, the backup I / F module 30 can know the communication status of the active I / F module 20, thus enabling the communication system 10 to perform processing to maintain the same internal state.

[0066] Furthermore, the response processing unit 32b of the backup-side I / F module 30 waits for a waiting period M from the time it receives a response from the lower-side module 40, and if it has not received a retransmission of the request from the active-side I / F module 20 to the lower-side module 40, or has not received a timeout notification from the active-side I / F module 20, it processes the response from the lower-side module 40.

[0067] As a result, the communication system 10 has the effect of maintaining the same internal state because the backup I / F module 30 checks the communication status of the active I / F module 20 before processing the response, so that the active I / F module 20 and the backup I / F module 30 process the same response content.

[0068] Furthermore, if the backup-side I / F module 30 has received the initial response from the lower-level module 40 and the response from the lower-level module 40 to the retransmission of the request, and has not received a timeout notification from the active-side I / F module 20, the response processing unit 32b of the backup-side I / F module 30 processes the response from the lower-level module 40 to the retransmission of the request.

[0069] As a result, the communication system 10 has the effect of maintaining identical internal states because the backup I / F module 30 checks the communication status of the active I / F module 20 and then processes the response to the retransmission of the request received by the active I / F module 20, so that the active I / F module 20 and the backup I / F module 30 process the same response content.

[0070] Furthermore, the switching unit 32c of the backup-side I / F module 30 switches the backup-side I / F module 30 to the active side by switching the operating state and enabling transmission when the backup-side I / F module 30 receives a response from the lower-level module 40 and a timeout notification from the active-side I / F module 20.

[0071] As a result, the communication system 10 has the effect that if an abnormality occurs in the communication function of the active I / F module 20, the backup I / F module 30 can detect the communication abnormality and quickly switch the operating state between the active and backup sides.

[0072] [6. Hardware Configuration] The communication system 10 according to the above-described embodiment consists of an active I / F module 20 and a backup I / F module 30, and the active I / F module 20 and the backup I / F module 30 are realized by a computer 1000 having a configuration as shown in Figure 10, for example. Figure 10 is a hardware configuration diagram showing an example of a computer that realizes the functions of the active I / F module 20 and the backup I / F module 30 of the communication system 10.

[0073] Computer 1000 has a configuration in which a CPU 1100, RAM 1200, ROM 1300, auxiliary storage device 1400, communication interface 1500, and input / output interface 1600 are connected by a bus 1800. The CPU 1100 operates based on programs stored in the ROM 1300 or auxiliary storage device 1400 and controls each part. The ROM 1300 stores boot programs executed by the CPU 1100 when computer 1000 starts up, as well as programs that depend on the computer 1000's hardware.

[0074] The auxiliary storage device 1400 stores programs executed by the CPU 1100, and data used by such programs. The communication interface 1500 receives data from other devices via a predetermined communication network and sends it to the CPU 1100, and transmits data generated by the CPU 1100 to other devices via the predetermined communication network.

[0075] The CPU 1100 controls output devices such as displays and printers, and input / output devices 1700 such as keyboards and mice, via the input / output interface 1600. The CPU 1100 acquires data from the input / output devices 1700 via the input / output interface 1600. The CPU 1100 also outputs the generated data to the input / output devices 1700 via the input / output interface 1600.

[0076] For example, when the computer 1000 functions as the active-side I / F module 20 or the backup-side I / F module 30 of the communication system 10 according to this embodiment, the CPU 1100 of the computer 1000 realizes the functions of the control unit 22 or the control unit 32 by executing a program loaded on the RAM 1200.

[0077] [7. Others] Of the processes described in the embodiments above, all or part of the processes described as being performed automatically can be performed manually, or all or part of the processes described as being performed manually can be performed automatically by known methods. In addition, the processing procedures, specific names, and information including various data and parameters shown in the above document and drawings can be changed at will unless otherwise specified. For example, the various information shown in each figure is not limited to the information shown.

[0078] Furthermore, the components of each illustrated device are functionally conceptual and do not necessarily need to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those illustrated, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads, usage conditions, etc.

[0079] The aforementioned components include those that can be easily conceived by a person skilled in the art, those that are substantially identical, and those that fall within the so-called equivalent range. Furthermore, the embodiments described above can be appropriately combined as long as the processing content is not contradictory.

[0080] Furthermore, the terms "section," "module," and "unit" mentioned above can be replaced with "means" or "circuit," etc. For example, a control unit can be replaced with a control means or a control circuit.

[0081] Although some embodiments of the present invention have been described in detail above with reference to the drawings, these are illustrative examples, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, starting with the embodiments described in the disclosure section of the invention. [Explanation of Symbols]

[0082] 10 Communication Systems 20 Active side I / F module 21 Communications Department 22 Control Unit 22a Transmitter 23 Memory section 23a Timeout Information Storage Unit 30 Backup side I / F module 31 Communications Department 32 Control Unit 33 Storage section 32a Monitoring Department 32b Response Processing Unit 32c switching section 33a Monitoring information storage unit 33b Standby information storage unit 40 Lower Modules

Claims

1. A communication system having a module in operation and a module in standby mode, The module in the aforementioned operating state is The transmission unit has a predetermined notification for making the internal state of the operating module the same as the internal state of the standby module, which sends a timeout notification to the standby module if the operating module does not receive a response from the subordinate module to the retransmission of a request from the operating module to the subordinate module. The aforementioned module in standby state A monitoring unit that monitors communication between the module in operation and the lower-level module, It includes a response processing unit that processes the response from the lower module. A communication system characterized by the following features.

2. The response processing unit, after receiving a response from the subordinate module, waits for a predetermined time and, if the request has not been resent from the operating module to the subordinate module, or if it has not received the timeout notification from the operating module, it processes the response from the subordinate module. The communication system according to feature 1.

3. The response processing unit processes the response from the subordinate module to the request retransmission if the standby module has received the initial response from the subordinate module and the response from the subordinate module to the request retransmission, but has not received the timeout notification from the operating module. The communication system according to feature 1.

4. The aforementioned module in standby state The switching unit has, upon receiving a response from the lower-level module and a timeout notification from the operating module, switches the standby module to the operating state. The communication system according to feature 1.

5. A communication method performed by a communication system having a module in operation and a module in standby mode, The module in the aforementioned operating state is As a predetermined notification for making the internal state of the operating module the same as the internal state of the standby module, the operating module sends a timeout notification to the standby module if it does not receive a response from the subordinate module to the retransmission of a request from the operating module to the subordinate module. The aforementioned module in standby state A monitoring step that monitors communication between the module in operation and the subordinate module, The process includes a response processing step for processing the response from the lower-level module, A communication method characterized by the following features.

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