Communication control system, communication control device, communication device, and communication control method

Abstract

A communication control system according to the present invention comprises a plurality of communication devices and a communication control device. The communication devices each comprise: a plurality of input / output ports; a signal strength monitoring unit that monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only when a measured value of the signal strength is less than a prescribed threshold value; and a route setting unit that switches the input / output port to be used on the basis of a route setting switching instruction acquired from the communication control device. The communication control device comprises: a monitoring object setting unit that controls the signal strength monitoring unit so that only the input / output port through which the signal passes is monitored; an analysis unit that searches for another signal route connecting the plurality of communication devices when the notification is received from the signal strength monitoring unit; and a route setting control unit that transmits, to the plurality of communication devices, the route setting switching instruction to switch to the other signal route searched for by the analysis unit.

Description

Communication control system, communication control device, communication device, and communication control method

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

[0002] In some conventional optical communication systems, a control device constantly monitors the signal strength of communication data at each input / output port of a controlled device, such as a transfer device. When the measured signal strength value falls below a preset threshold, the control device recognizes that an abnormality has occurred in the signal line or the controlled device. When the control device recognizes that an abnormality has occurred, it switches the route setting of the controlled device. This allows the optical communication system to switch to another signal path and continue communication.

[0003] Takahiro Suzuki et al., “Automatic fast failure restoration on software-defined optical switch controller with NETCONF / RESTCONF for all-photonics network”, IEICE Communications Express, Vol.11, No.11, pp.709-714, 2022.

[0004] However, when there are a large number of devices to be controlled, or when the devices to be controlled have a large number of input / output ports, the number of input / output ports to be monitored becomes enormous, resulting in an increase in the amount of communication between the control device and the devices to be controlled, which can cause congestion and exceed the processing capacity of the control device, resulting in problems with the control device's continuous monitoring or anomaly detection.

[0005] In view of the above circumstances, the present invention aims to provide a technique that can prevent problems from occurring in continuous monitoring or abnormality detection by a control device even when there are a large number of input / output ports to be monitored.

[0006] One aspect of the present invention is a communication control system having a plurality of communication devices and a communication control device, wherein the communication devices have a plurality of input / output ports, a signal strength monitoring unit that monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only if the measured signal strength value is below a predetermined threshold, and a route setting unit that switches the input / output port to be used based on a route setting switching instruction obtained from the communication control device, and the communication control device has a monitoring target setting unit that controls the signal strength monitoring unit so that only the input / output port through which the signal passes is monitored, an analysis unit that, when receiving the notification from the signal strength monitoring unit, searches for another signal route connecting the plurality of communication devices, and a route setting control unit that sends the route setting switching instruction to the plurality of communication devices to switch to the another signal route searched for by the analysis unit.

[0007] Another aspect of the present invention is a communication control device in a communication control system having a plurality of communication devices and a communication control device, the communication control device comprising: a monitoring target setting unit that controls the communication devices so that only input / output ports through which signals pass are monitored; an analysis unit that, when notified by one of the communication devices, searches for another signal path connecting the plurality of communication devices; and a path setting control unit that sends a path setting switching instruction to the plurality of communication devices to switch to the another signal path searched for by the analysis unit.

[0008] Another aspect of the present invention is a communication device in a communication control system having a plurality of communication devices and a communication control device, the communication device comprising a plurality of input / output ports, a signal strength monitoring unit that monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only if the measured signal strength value is below a predetermined threshold, and a route setting unit that switches the input / output port to be used based on a route setting switching instruction obtained from the communication control device.

[0009] Another aspect of the present invention is a communication control method using a communication control system having a plurality of communication devices and a communication control device, the communication control method comprising: a monitoring target setting step in which the communication control device controls the communication devices so that only input / output ports through which signals pass are monitored; a signal strength monitoring step in which the communication devices monitor the signal strength of signals passing through the input / output ports and notify the communication control device only if the measured signal strength value is below a predetermined threshold; an analysis step in which the communication control device, when receiving the notification, searches for another signal path connecting the plurality of communication devices; a route setting control step in which the communication control device sends a route setting switching instruction to the plurality of communication devices to switch to the other signal path that has been found; and a route setting step in which the communication devices switch the input / output port to be used based on the acquired route setting switching instruction.

[0010] Another aspect of the present invention is a communication control method using a communication control system having a plurality of communication devices and a communication control device, the communication control method comprising: a monitoring target setting step in which the communication control device controls the communication devices so that only input / output ports through which signals pass are monitored; an analysis step in which the communication control device, when notified by one of the communication devices, searches for another signal path connecting the plurality of communication devices; and a path setting control step in which the communication control device sends a path setting switching instruction to the plurality of communication devices to switch to the other signal path that has been found.

[0011] Another aspect of the present invention is a communication control method using a communication control system having a plurality of communication devices and a communication control device, the communication control method including a signal strength monitoring step in which the communication devices monitor the signal strength of signals passing through input / output ports and notify the communication control device only if the measured signal strength value is below a predetermined threshold, and a route setting step in which the communication devices switch the input / output port to be used based on a route setting switching instruction obtained from the communication control device.

[0012] According to the present invention, even when there are a large number of input / output ports to be monitored, it is possible to prevent problems from occurring in the continuous monitoring or abnormality detection by the control device.

[0013] It is an overall configuration diagram of an optical communication system according to one embodiment of the present invention.It is an overall configuration diagram of an optical communication system according to one embodiment of the present invention.It is a block diagram showing the functional configuration of a control system according to one embodiment of the present invention.It is a flowchart showing an example of the operation of the control system according to one embodiment of the present invention.

[0014] The present invention is characterized in that only input / output ports of the control target device (communication device) through which communication data passes are monitored, and the control device (communication control device) transmits a monitoring signal to the control target device (communication device). Also, the present invention is characterized in that the control target device (communication device) transmits a response signal to the monitoring signal to the control device (communication control device) only when the signal strength value of the communication data at the input / output port of the control target device (communication device) is below a preset threshold.

[0015] Due to these features, even when there are a large number of control target devices (communication devices) or when the control target devices (communication devices) have a large number of input / output ports, the present invention can suppress an increase in the amount of communication between the control device and the control target devices. This prevents congestion and the control device (communication control device) from exceeding its processing capacity, allowing the control device (communication control device) to perform constant monitoring or abnormality detection without causing any malfunctions.

[0016] Hereinafter, a communication control system, a communication control device, a communication device, a communication control method, and a communication method according to embodiments of the present invention will be described in detail with reference to the drawings.

[0017] [Configuration of Optical Communication System] Fig. 1 is an overall configuration diagram of an optical communication system according to one embodiment of the present invention. As shown in Fig. 1, the optical communication system is configured to include terminal devices 100-1 and 100-2, control target devices 200-1 and 200-2, and a control device 300. In the following description, when it is not necessary to distinguish between the terminal device 100-1 and the terminal device 100-2, they may be simply referred to as "terminal device 100." In the following description, when it is not necessary to distinguish between the control target device 200-1 and the control target device 200-2, they may be simply referred to as "control target device 200."

[0018] The control target device 200 is an example of a communication device of the present invention. The control device 300 is an example of a communication control device of the present invention. Furthermore, a control system including the control target device 200 and the control device 300 is an example of a communication control system of the present invention.

[0019] The optical communication system illustrated in FIG. 1 has two terminal devices 100 and two control target devices 200, but may have more terminal devices 100 and more control target devices 200.

[0020] The terminal device 100 transmits and receives communication data to and from other terminal devices 100 via the control target device 200 .

[0021] The controlled device 200 is installed in a communication network between multiple terminal devices 100 that communicate with each other. The controlled device 200 is a device that transfers communication data sent and received between the multiple terminal devices 100. Communication data is input to the controlled device 200 from the terminal devices 100 or other controlled device 200. The controlled device 200 outputs the communication data to the terminal devices 100 or other controlled device 200.

[0022] The control target device 200 also has a plurality of input / output ports. The control target device 200 performs route setting to switch communication connections between input / output ports within the device itself, thereby switching the signal path through which communication data is transmitted.

[0023] The control device 300 controls the route setting performed by the control target device 200. The control device 300 controls the route setting performed by one or more control target devices 200, thereby controlling switching of signal paths for communication data transmitted and received between multiple terminal devices 100.

[0024] 1, a single control device 300 controls multiple control target devices 200, but the present invention is not limited to this configuration. For example, a separate control device 300 may be installed for each control target device 200.

[0025] As shown in FIG. 1, terminal device 100-1 has an input / output port 1-1. The input / output port 1-1 is connected to an input / output port 11-1 of a control target device 200-1 via line a. The control target device 200-1 has input / output ports 11-1 to 11-N and input / output ports 12-1 to 12-N. The control target device 200-1 can arbitrarily switch the communication connection between the input / output ports 11-1 to 11-N and the input / output ports 12-1 to 12-N. This switches the path setting. Note that, for example, other terminal devices (not shown) are connected to the input / output ports 11-2 to 11-N, respectively.

[0026] Similarly, the terminal device 100-2 has an input / output port 2-1. The input / output port 2-1 is connected to an input / output port 22-1 of the control target device 200-2 via a line e. The control target device 200-2 has input / output ports 21-1 to 21-N and input / output ports 22-1 to 22-N. The control target device 200-2 can arbitrarily switch the communication connection between the input / output ports 21-1 to 21-N and the input / output ports 22-1 to 22-N. This switches the path setting. Note that, for example, other terminal devices (not shown) are connected to the input / output ports 22-2 to 22-N, respectively.

[0027] Of the multiple input / output ports of the control target device 200, the control device 300 monitors only the input / output ports through which communication data transmitted and received between the multiple terminal devices 100 passes and which are connected to other control target devices 200 (rather than the terminal devices 100). The control device 300 transmits a monitoring signal for the input / output port to the control target device 200.

[0028] 1 shows, as an example, a situation in which input / output ports 11-1 and 12-1 are connected by line b inside control target device 200-1, input / output port 12-1 of control target device 200-1 and input / output port 21-1 of control target device 200-2 are connected by line c, and input / output ports 21-1 and 22-1 inside control target device 200-2 are connected by line d. In this situation, the signal path between terminal devices 100-1 and 100-2 is a path via lines a to e.

[0029] In this case, the control device 300 monitors only the input / output port 12-1 of the control target device 200-1 and the input / output port 21-1 of the control target device 200-2, which are input / output ports through which communication data passes. Therefore, the control device 300 transmits only a monitoring signal for monitoring the input / output port 12-1 to the control target device 200-1, and transmits only a monitoring signal for monitoring the input / output port 21-1 to the control target device 200-2.

[0030] When the signal strength value of the input / output port to be monitored is equal to or greater than a preset threshold, the control target device 200 does not transmit a response signal to the monitoring signal from the control device 300. On the other hand, when the signal strength of the input / output port to be monitored is below the preset threshold (is less than the threshold), the control target device 200 transmits a response signal (an abnormality occurrence notification) to the control device 300 to notify the occurrence of an abnormality.

[0031] When the control device 300 receives a response signal (anomaly occurrence notification) transmitted from the control target device 200 notifying the occurrence of an abnormality, it determines that an abnormality has occurred in the signal path connected to the input / output port or in the input / output port itself. The control device 300 searches for a signal path connected to the input / output port and another signal path that bypasses the input / output port. The control device 300 decides to switch the route to the other signal path found and immediately transmits a route setting switch instruction to the control target device 200.

[0032] The control target device 200 switches the route to another signal route based on the route setting switching instruction from the control device 300 .

[0033] 2 shows an example of the state of the optical communication system after path switching has been performed. As an example, FIG. 2 shows a situation in which, inside the control target device 200-1, input / output ports 11-1 and 12-N are connected by line f, input / output port 12-N of the control target device 200-1 and input / output port 21-N of the control target device 200-2 are connected by line g, and inside the control target device 200-2, input / output ports 21-N and 22-1 are connected by line h. In this situation, the signal path between the terminal devices 100-1 and 100-2 is a path via lines a, f to h, and e.

[0034] After the path switching is performed, the control device 300 monitors only the input / output port 12-N of the control target device 200-1 and the input / output port 21-N of the control target device 200-2, which are input / output ports through which communication data passes. Therefore, the control device 300 transmits only a monitoring signal for monitoring the input / output port 12-N to the control target device 200-1, and transmits only a monitoring signal for monitoring the input / output port 21-N to the control target device 200-2.

[0035] [Configuration of Control System] The following provides a more detailed explanation of the configuration of the control system made up of the controlled device 200 and the control device 300. Fig. 3 is a block diagram showing the functional configuration of the control system according to one embodiment of the present invention.

[0036] 3, the control target device 200 includes a threshold setting unit 201, a signal strength monitoring unit 202, and a route setting unit 203. The control device 300 includes a threshold information acquisition unit 301, a monitoring target setting unit 302, an analysis unit 303, and a route setting control unit 304.

[0037] The threshold setting unit 201 of the control target device 200 sets a specified signal strength threshold for the specified input / output port to be monitored in accordance with a threshold setting instruction sent from the monitoring target setting unit 302 of the control device 300 .

[0038] The signal strength monitoring unit 202 constantly monitors the signal strength of communication data (signals) at the input / output port. The signal strength monitoring unit 202 transmits an abnormality occurrence notification (alarm) to the analysis unit 303 of the control device 300 only when the measured signal strength value is below a threshold value (less than the threshold value).

[0039] The route setting unit 203 switches the connection of the input / output ports in accordance with a route setting switching instruction transmitted from the route setting control unit 304 of the control device 300, thereby switching the route of the control target device 200.

[0040] The threshold information acquisition unit 301 acquires threshold information that corresponds identification information (e.g., input / output port number) that identifies the input / output ports of each controlled device 200 to be monitored, which is notified from a higher-level device or specified by input operation by an operator, with the signal strength threshold at each input / output port.

[0041] The monitoring target setting unit 302 sets as monitoring targets only the input / output ports through which communication data passes and which are connected to other control target devices 200 (not to the terminal device 100) among the input / output ports of the control target device 200. The monitoring target setting unit 302 also notifies the control target device 200 of identification information (for example, input / output port numbers) that identifies the input / output ports to be monitored, and the signal strength threshold value for each input / output port.

[0042] When the analysis unit 303 receives an abnormality occurrence notification (alarm) transmitted from the signal strength monitoring unit 202 of the control target device 200, it determines whether to switch the route setting of each control target device 200. If the analysis unit 303 determines to switch the route setting, the route setting control unit 304 transmits a route setting switching instruction to the control target device 200 that requires switching of the route setting. The route setting control unit 304 controls the route setting of one or more control target devices 200, thereby switching the signal path of communication data transmitted and received between multiple terminal devices 100.

[0043] [Operation of Control System] Hereinafter, a specific example will be given to explain the operation of a control system made up of the controlled device 200 and the control device 300. Fig. 4 is a flowchart showing an example of the operation of the control system in one embodiment of the present invention.

[0044] First, in the initial connection state, as shown in Figure 1, terminal device 100-1 and terminal device 100-2 are connected via control target devices 200-1 and 200-2, and communication data (signals) are being sent and received. At this time, the input / output ports of each control target device 200 through which the communication data passes are input / output port 11-1, input / output port 12-1, input / output port 21-1, and input / output port 22-1. Furthermore, the signal lines through which the communication data passes are lines a to e.

[0045] The threshold information acquisition unit 301 of the control device 300 acquires threshold information including the input / output port numbers of each control target device 200 to be monitored and the signal strength thresholds for each input / output port, which has been notified from a higher-level device or designated by an input operation by an operator (step S001). The monitoring target setting unit 302 transmits identification information for identifying the input / output ports to be monitored and a threshold setting instruction for instructing the setting of the signal strength thresholds to the threshold setting unit 201 of each control target device 200 to be monitored (step S002).

[0046] The threshold setting unit 201 of each control target device 200 receives the threshold setting instruction (step S003), and sets a threshold based on the received threshold setting instruction (step S004).

[0047] Here, it is assumed that the identification information for identifying the input / output port to be monitored and the threshold values ​​of each signal strength for the communication data transmitted from the terminal device 100-1 to the terminal device 100-2 are as follows:

[0048] I / O port to be monitored: I / O port 12-1, signal strength threshold: -5 [dBm] (signal strength of signal output from I / O port 12-1 to I / O port 21-1) I / O port to be monitored: I / O port 21-1, signal strength threshold (-10 [dBm] (signal strength of signal input from I / O port 12-1 to I / O port 21-1)

[0049] After the threshold setting unit 201 has completed setting the threshold, the analysis unit 303 of the control device 300 starts signal monitoring of each input / output port to be monitored, and constantly monitors the signals in cooperation with each control target device 200 (step S005). Each control target device 200 constantly monitors the signal strength of communication data (signals) passing through each input / output port to be monitored, and if it detects that the signal strength is equal to or greater than the threshold, it does not notify the analysis unit 303 of the control device 300. On the other hand, if it detects that the signal strength is less than the threshold (step S006), the signal strength monitoring unit 202 of the control target device 200 immediately transmits an abnormality occurrence notification including the signal strength value to the analysis unit 303 of the control device 300 (step S007).

[0050] As an example, assume that an abnormality is detected at a certain time in the input / output port 21-1 of the control target device 200-2, which has a threshold set to -10 dBm. For example, the signal strength value of the communication data at the input / output port 21-1 becomes -35 dBm, which is significantly below the threshold, causing communication between the terminal devices 100-1 and 100-2 to be cut off, and an abnormality occurrence notification is sent to the analysis unit 303 of the control device 300. The following describes a case in which this occurs.

[0051] The analysis unit 303 of the control device 300 receives the abnormality occurrence notification transmitted from the signal strength monitoring unit 202 of the control target device 200 (step S008). The analysis unit 303 identifies the location of the abnormality based on the received abnormality occurrence notification (step S009). For example, since the analysis unit 303 has not received the abnormality occurrence notification from the input / output port 12-1, it determines that some abnormality (for example, a break in the signal line) has occurred in the signal line (line c) between the input / output port 12-1 and the input / output port 21-1.

[0052] To avoid the continuation of the communication interruption, the analysis unit 303 of the control device 300 searches for a signal path that can bypass the abnormal location (line c) and decides to switch to a new signal path via line g (step S010). The analysis unit 303 instructs the path setting control unit 304 to switch to the new signal path. The path setting control unit 304 transmits a path setting switching instruction to the path setting unit 203 of the corresponding control target device 200 to instruct the path switching (step S011).

[0053] Here, as an example, the route setting control unit 304 of the control device 300 instructs the route setting unit 203 of the control target device 200-1 to switch the connection destination of the input / output port 11-1 from the input / output port 12-1 to the input / output port 12-N (accompanying this, the signal line to be passed through is switched from line b to line f). Also, the route setting control unit 304 of the control device 300 instructs the route setting unit 203 of the control target device 200-2 to switch the connection destination of the input / output port 22-1 from the input / output port 21-1 to the input / output port 21-N (accompanying this, the signal line to be passed through is switched from line d to line h).

[0054] The route setting unit 203 of each control target device 200 receives the route setting switching instruction transmitted from the route setting control unit 304 of the control device 300 (step S012). The route setting unit 203 of each control target device 200 switches the route setting in accordance with the received route setting switching instruction (step S013). When these route settings are completed, it becomes possible to restore the communication service between the terminal devices 100-1 and 100-2 using a new signal path that bypasses the line c where the abnormality occurred.

[0055] Even after the above route setting, in order to continue monitoring the signals of each input / output port through which communication data passes, the monitoring target setting unit 302 of the control device 300 automatically resets the input / output ports to be monitored and each threshold value.

[0056] As described above, the control system according to one embodiment of the present invention includes the control device 300 and the control target device 200. The control device 300 monitors only the input / output ports of each control target device 200 through which communication data passes, and transmits a monitoring signal to each control target device 200. Furthermore, the control target device 200 transmits a response signal to the monitoring signal to the control target device 200 only when the signal strength value of the communication data at the input / output port of the control target device 200 is below a preset threshold.

[0057] With this configuration, the control system according to one embodiment of the present invention can suppress an increase in the amount of communication between the control device 300 and the control-target device 200, even if there are a large number of control-target devices 200 or if the control-target devices 200 are equipped with a large number of input / output ports. This prevents congestion and exceeding the processing capacity of the control device 300, allowing the control device 300 to constantly monitor or detect abnormalities without causing any malfunctions.

[0058] According to the above-described embodiment, the communication control system includes a plurality of communication devices and a communication control device. For example, the communication control system is the control system in the embodiment, the communication device is the controlled device 200 in the embodiment, and the communication control device is the control device 300 in the embodiment. The communication device includes a plurality of input / output ports, a signal strength monitoring unit, and a route setting unit. For example, the input / output ports are the input / output ports 11-1 to 11-N, 12-1 to 12-N, 21-1 to 21-N, and 22-1 to 22-N in the embodiment, the signal strength monitoring unit is the signal strength monitoring unit 202 in the embodiment, and the route setting unit is the route setting unit 203 in the embodiment. The signal strength monitoring unit monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only when the measured signal strength value is below a predetermined threshold. For example, the signal is communication data in the embodiment, and the notification is an abnormality occurrence notification in the embodiment. The route setting unit switches the input / output port to be used based on a route setting switching instruction acquired from the communication control device. The communication control device includes a monitoring target setting unit, an analysis unit, and a route setting control unit. For example, the monitoring target setting unit is the monitoring target setting unit 302 in the embodiment, the analysis unit is the analysis unit 303 in the embodiment, and the route setting control unit is the route setting control unit 304 in the embodiment. The monitoring target setting unit controls the signal strength monitoring unit so that only input / output ports through which signals pass are monitored. When notified by the signal strength monitoring unit, the analysis unit searches for another signal route connecting the multiple communication devices. The route setting control unit transmits a route setting switching instruction to the multiple communication devices to switch to the another signal route searched for by the analysis unit.

[0059] In the above communication control system, the communication control device may further include a threshold information acquisition unit. For example, the threshold information acquisition unit is the threshold information acquisition unit 301 in the embodiment. The threshold information acquisition unit acquires a signal strength threshold for each input / output port, and transmits threshold information including the acquired threshold to the communication device. The communication device may further include a threshold setting unit. For example, the threshold setting unit is the threshold setting unit 201 in the embodiment. The threshold setting unit sets a threshold based on the threshold information for each input / output port monitored by the monitoring target setting unit.

[0060] In the above communication control system, the signal may be a signal transmitted and received between a plurality of terminal devices relayed by a communication device. For example, the terminal device is terminal device 100 in the embodiment. The monitoring target setting unit may also control the signal strength monitoring unit to monitor only input / output ports connecting the communication devices.

[0061] In the above-described embodiments, some or all of the configurations of the control target device 200 and the control device 300 may be implemented by a computer. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as floppy disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within the computer system serving as the server or client. The program may be designed to implement some of the above-described functions, or may be capable of implementing the above-described functions in combination with programs already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0062] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the present invention that do not deviate from the gist of the present invention.

[0063] 1-1, 2-1, 11-1 to 11-N, 12-1 to 12-N, 21-1 to 21-N, 22-1 to 22-N...input / output ports, 100, 100-1, 100-2...terminal devices, 200, 200-1, 200-2...devices to be controlled, 201...threshold setting unit, 202...signal strength monitoring unit, 203...route setting unit, 300...control device, 301...threshold information acquisition unit, 302...monitoring target setting unit, 303...analysis unit, 304...route setting control unit, a to h...lines

Claims

1. A communication control system having a plurality of communication devices and a communication control device, wherein the communication devices comprise a plurality of input / output ports, a signal strength monitoring unit that monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only when the measured signal strength value is below a predetermined threshold, and a route setting unit that switches the input / output port to be used based on a route setting switching instruction obtained from the communication control device, and the communication control device comprises: a monitoring target setting unit that controls the signal strength monitoring unit to monitor only the input / output ports through which the signal passes, an analysis unit that, when receiving the notification from the signal strength monitoring unit, searches for another signal route connecting the plurality of communication devices, and a route setting control unit that transmits the route setting switching instruction to the plurality of communication devices to switch to the another signal route searched for by the analysis unit.

2. The communication control system of claim 1, wherein the communication control device further comprises a threshold information acquisition unit that acquires the signal strength threshold for each of the input / output ports and transmits threshold information including the acquired threshold to the communication device, and the communication device further comprises a threshold setting unit that sets the threshold based on the threshold information for each of the input / output ports monitored by the monitoring target setting unit.

3. The communication control system according to claim 1, wherein the signal is a signal transmitted and received between a plurality of terminal devices relayed by the communication device, and the monitoring target setting unit controls the signal strength monitoring unit so that only the input / output ports connecting the communication devices to each other are monitored.

4. A communication control device in a communication control system having a plurality of communication devices and a communication control device, the communication control device comprising: a monitoring target setting unit that controls the communication devices so that only input / output ports through which signals pass are monitored; an analysis unit that, when notified by one of the communication devices, searches for another signal path connecting the plurality of communication devices; and a path setting control unit that sends a path setting switching instruction to the plurality of communication devices to switch to the other signal path searched for by the analysis unit.

5. A communication device in a communication control system having a plurality of communication devices and a communication control device, the communication device comprising: a plurality of input / output ports; a signal strength monitoring unit that monitors the signal strength of signals passing through the input / output ports and notifies the communication control device only when the measured signal strength value is below a predetermined threshold; and a route setting unit that switches the input / output port to be used based on a route setting switching instruction obtained from the communication control device.

6. A communication control method using a communication control system having a plurality of communication devices and a communication control device, comprising: a monitoring target setting step in which the communication control device controls the communication devices so that only input / output ports through which signals pass are set as monitoring targets; a signal strength monitoring step in which the communication devices monitor the signal strength of signals passing through the input / output ports and notify the communication control device only if the measured signal strength value is below a predetermined threshold; an analysis step in which the communication control device searches for another signal path connecting the plurality of communication devices when it receives the notification; a route setting control step in which the communication control device sends a route setting switch instruction to the plurality of communication devices to switch to the other signal path that has been found; and a route setting step in which the communication devices switch the input / output ports to be used based on the acquired route setting switch instruction.

7. A communication control method using a communication control system having a plurality of communication devices and a communication control device, comprising: a monitoring target setting step in which the communication control device controls the communication devices so that only input / output ports through which signals pass are monitored; an analysis step in which the communication control device searches for another signal path connecting the plurality of communication devices when notified by one of the communication devices; and a path setting control step in which the communication control device transmits a path setting switching instruction to the plurality of communication devices to switch to the other signal path that has been found.

8. A communication control method using a communication control system having a plurality of communication devices and a communication control device, comprising: a signal strength monitoring step in which the communication devices monitor the signal strength of signals passing through input / output ports and notify the communication control device only when the measured signal strength value is below a predetermined threshold; and a route setting step in which the communication devices switch the input / output port to be used based on a route setting switching instruction obtained from the communication control device.

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