JP3914072B2 - Network failure monitoring method, communication system, and line switching apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a network failure monitoring method, a communication system, and a line switching device, and more particularly to a network failure monitoring method, a communication system, and a line switching device for identifying and reporting a failure part of a failure that has occurred in a network.
[0002]
[Prior art]
In a communication system that monitors facilities such as plants and buildings, various equipment installed in the facility is connected to a monitoring device via a network, and data communication with each equipment is performed to operate and operate these equipment. Is monitoring the situation.
Here, when a failure occurs in the network, data cannot be collected from each facility device, which may greatly affect the operation / operation of the facility device and the behavior of the facility. For this reason, in such a communication system, the network is duplexed and the line switching device is arranged at the end point of the duplexed network, and when one system fails, the individual line switching device switches to the other system. It is supposed to be.
[0003]
Conventionally, in a communication system using Ethernet (registered trademark) as a network, a failure is detected by using a spanning tree protocol (STP) or SNMP (Simple Network Management Protocol). Some monitor automatically.
STP is a management bridge protocol that uses a spanning tree algorithm to avoid network loops, exchanges management messages with other bridges to detect loops, shuts down unnecessary bridge interfaces, and loops There is a function to remove. SNMP is a TCP / IP-based management protocol dedicated to the Internet, and has functions for monitoring, controlling and setting network configurations and network devices, collecting statistics, managing performance, and security.
[0004]
[Problems to be solved by the invention]
However, in such a conventional communication system, when the STP is used, although the network path where the failure has occurred can be specified, there is no function to immediately notify the monitoring device of the failure occurrence, and the administrator catches the failure occurrence. There was a problem that there was a delay until the system was restored and it was impossible to respond quickly. Also, when using SNMP, it is necessary to make each line switching device highly functional and to operate an operation system and a dedicated protocol, which causes the size and complexity of the line switching device, and manages faults at low cost. There was a problem that could not.
The present invention is intended to solve such a problem, and a network failure monitoring method and a communication system capable of identifying and quickly notifying a failure site of a failure that has occurred in a network without increasing the functionality of a line switching device And it aims at providing a line switching device.
[0005]
[Means for Solving the Problems]
In order to achieve such an object, a network failure monitoring method according to the present invention includes a plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and the node devices and the duplex network. Monitors data communication failures with a communication system consisting of a plurality of line switching devices that are connected between and connected to the relevant node equipment to switch to a communication system that does not have a failure of the two communication systems. In the network fault monitoring method, each line switching device includes one master line switching device that operates as a master device based on the master / slave method and one or more other devices that operate as slave devices based on the master / slave method. Slave line switching device, and the master line switching device Sends a check request message to each slave line switching device independently for each system, and whether or not a check response message is returned from the slave line switching device via the communication system used to send the check request message. Based on the above, the failure occurrence in each communication system is monitored, and when the slave line switching device receives a check request message from the master line switching device, the slave line switching device uses the communication system that received the message to A check response message including the IP address of the connected node device is returned to the master line switching device, and the master line switching device uses the IP address included in the check response message from the slave line switching device as the slave line switching device. And check from any slave line switching device If the answer message could not be received, a failure occurrence notification message including the IP address corresponding to the slave line switching device and the IP address of the node device connected to the master line switching device as information indicating the failure part, The data is transmitted to a predetermined monitoring device capable of data communication with the master line switching device.
[0006]
At this time, Master line switching device The IP address included in the received check response message may be managed in association with the transmission source line switching device unique address of the check response message.
[0007]
The communication system according to the present invention includes a plurality of node devices that perform data communication via a duplex network including two independent communication systems, and the node devices provided between the node devices and the duplex network. In a communication system comprising a plurality of line switching devices that switch and connect a connected node side line to a communication system that does not have a failure among the two communication systems, each line switching device operates as a master device based on a master / slave system. One master line switching device and one or more other slave line switching devices that operate as slave devices based on the master / slave method. The master line switching device is independent for each communication system of the duplex network. Send a check request message to the slave line switching unit, and in response to this, disconnect the slave line. The failure monitoring means for monitoring the occurrence of failure in each communication system based on the presence or absence of reception of a check response message returned from the device via the communication system used for transmission of the check request message, the slave line switching device, When a check request message is received from the master line switching device, a check response message including the IP address of the node device connected to the slave line switching device is sent to the master line switching using the communication system that received the message. A monitoring response means for returning to the device, and the failure monitoring means manages the IP address included in the check response message from the slave line switching device for each slave line switching device and checks from any slave line switching device. If the response message could not be received, information indicating the faulty part A failure notification message including an IP address corresponding to the slave line switching device and an IP address of a node device connected to the master line switching device is transmitted to a predetermined monitoring device capable of data communication with the master line switching device. It is what you do.
[0008]
At this time, the failure monitoring means may manage the IP address included in the received check response message in association with the transmission source line switching device unique address of the check response message.
[0009]
Further, the line switching apparatus according to the present invention is provided with a plurality of node devices that perform data communication via a duplex network including two independent communication systems, and the node devices provided between these node devices and the duplex network. Is a communication system comprising a plurality of line switching devices for switching and connecting a node-side line connected to a communication system without a failure of two communication systems, and one of the line switching devices is based on a master / slave system. In a line switching device that operates as a master device and manages one or more other slave line switching devices that operate as a slave device based on a master / slave system, the slave line switching device is independently provided for each communication system of the duplex network. A check request message is sent to the slave line switching device in response to the check request message. Fault monitoring means for monitoring the occurrence of a fault in each communication system based on whether or not a check response message returned via the communication system used to transmit the message is received, and the slave line switching included in the received check response message An address table for managing the IP address of the node device connected to the device for each slave line switching device, and the failure monitoring means checks from any of the slave line switching devices according to the transmitted check request message. If the response message could not be received, the IP device corresponding to the slave line switching device is obtained by referring to the address table, and the node device connected to the IP address and the master line switching device as information indicating the failure part The failure occurrence message including the IP address of the line switching device It is obtained so as to transmit to the Data Communications possible predetermined monitoring device.
[0010]
In addition, another line switching apparatus according to the present invention is provided between a plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and between these node devices and the duplex network. A communication system comprising a plurality of line switching devices that switch and connect a node side line connected to a node device to a communication system that does not have a failure of two communication systems. In a line switching device that operates as one or more slave devices and is managed by another master line switching device that operates as a master device based on the master-slave method, a master is independently provided for each communication system of the duplex network. Receives the check request message sent from the line switching device and receives the check request message. A failure response means for returning a check response message to the master line switching device via the communication system, and an address acquisition means for acquiring the IP address of the node equipment from a packet exchanged by the node equipment via the node side line, The failure handling means checks the IP address acquired by the address acquisition means as information indicating a failure part notified from the master line switching device to a predetermined monitoring device capable of data communication with the master line switching device when a failure occurs. The response message is sent back.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention.
In this communication system, a monitoring device 2M, a line switching device 1M, node devices 2A to 2K, line switching devices 1A to 1K, an A-system network 3A, and a B-system network 3B are provided.
[0012]
The monitoring device 2M comprises a computer such as a server device as a whole, and operates / operates each of the node devices 2A to 2K by performing data communication with each of the node devices 2A to 2K via the A system network 3A and the B system network 3B. Monitor network failures as well as status.
The node devices 1A to 1K are controllers that control equipment and collect data from sensors.
The A-system network 3A and the B-system network 3B are duplex networks used for data communication between the monitoring device 2M and the node devices 2A to 2K. Normally, data communication is performed using either one of the systems. However, fault monitoring is performed independently for both systems, and the status of each system is monitored in real time.
[0013]
The line switching device 1M is provided between the monitoring device 2M and the A-system network 3A and the B-system network 3B, and switches and connects any of these communication systems to the monitoring device 2M.
The line switching devices 1A to 1K are provided between the node devices 2A to 2K and the A-system network 3A and the B-system network 3B, and switch-connect any one of these communication systems to the respective node devices 2A to 2K.
[0014]
Between these line switching devices 1M, 1A to 1K, a health check message is exchanged based on a master / slave system to monitor the occurrence of a failure in each line switching device or network.
In the following, a case will be described as an example where the line switching device 1M is the only master device (master line switching device) and all the other line switching devices 1A to 1K are slave devices (slave line switching devices). If the master device stops functioning due to the occurrence of a failure, any other slave device operates as a new master device.
[0015]
FIG. 2 shows the configuration of the line switching apparatus. In this line switching apparatus 1 (1A to 1K, 1M), a line switching unit 11 for switching and connecting the node side line 3M to either one of the A system network 3A and the B system network 3B, the A system network 3A, and the B system network By performing data communication with other line switching devices via 3B, a control unit 12 that controls the switching operation of the line switching unit 11 and a storage unit 15 that stores various types of information used for processing of the control unit 12 are provided. It has been. In particular, in the storage unit 15 of the master device, a unique address assigned in advance to identify each of the line switching devices 1A to 1K and 1M and the IP addresses of the node devices 2A to 2K connected to the device are stored. An address table 16 managed in association with each other is provided.
[0016]
The control unit 12 includes an operation management unit 21, a failure monitoring unit 22, a switching instruction unit 23, a monitoring response unit 24, and an address acquisition unit 25.
In the operation management means 21, whether to operate the device as one master device based on the master / slave method or whether to operate the device as one or more other slave devices controlled by the master device is turned on. Judge immediately. When it is determined that the device is to be operated as a master device, a master declaration message indicating that the device is a master device is periodically transmitted to one communication system. In the case of a slave device, when it becomes impossible to receive a master declaration message from another, it is determined that a master device failure has occurred, and it is determined whether or not to operate the device as a new master device.
[0017]
The failure monitoring means 22 monitors the occurrence of a communication failure in both the redundant A-system network 3A and B-system network 3B when the device is operating as a master device. Here, a check request message is transmitted in parallel to other slave devices via each communication system, and the occurrence of a failure is detected according to whether or not a check response message returned from the slave device is received. Then, the IP address included in the received check response message is associated with the line switching device, managed by the address table 16 of the storage unit 15, and the IP address of the node device corresponding to the line switching device that detected the occurrence of the failure is obtained. The failure occurrence notification message including this is notified to the monitoring device 2M.
[0018]
In the switching instruction unit 23, when the occurrence of a communication failure is detected by the failure monitoring unit 22 while the device is operating as a master device, all the line switching devices operating as slave devices are A line switching message to the other communication system is transmitted, and the line switching unit 11 of the own apparatus switches to the other communication system. When operating as a slave device, the line switching unit 11 of the own apparatus switches from one to the other communication system in response to a line switching message from the master device.
[0019]
In response to the check request message from the line switching device operating as the master device, the monitoring response unit 24 checks the IP address of the node device connected to the node side line 3M via the communication system that has received the message. Return a response message.
The address acquisition means 25 captures the latest packet exchanged on the node side line 3M and acquires the IP address of the node device connected to the node side line 3M.
[0020]
This control part 12 is comprised from ASIC (Application Specification Integrated Circuit).
About the content of the memory | storage part 15, you may make it update via a communication system as needed.
In addition, about each function means of the control part 12, it is not limited to the said structure, You may comprise a part or all of each function means by an electronic circuit, for example.
[0021]
Next, the operation of the communication system according to the present embodiment will be described with reference to FIGS. FIG. 3 is a flowchart showing a network failure monitoring processing procedure in the line switching device of the master device. FIG. 4 is a configuration example of the check response message. FIG. 5 shows a configuration example of the address table. FIG. 6 is a flowchart showing the switching instruction process.
The failure monitoring means 22 of the line switching device 1M as the master device periodically exchanges the health check messages with the line switching devices 1A to 1K as the slave devices, thereby allowing the A network 3A and the B network 3B to communicate with each other. Failure occurrence and failure recovery are detected. In the following, the fault monitoring process in the A-system network 3A will be described, but the same fault monitoring process is also performed in the B-system network 3B in parallel with this.
[0022]
First, in the line switching apparatus 1M that is a master apparatus, as shown in FIG. 3, the IP address of the node apparatus connected to the node side line 3M is acquired by the address acquisition unit 25, and the uniqueness of the line switching apparatus 1M is acquired. The address is stored in the address table 16 of the storage unit 15 in association with the address (step 100).
As shown in FIG. 5, the address table 16 stores a unique address that can identify the line switching device and a connection node IP address in association with each other. Here, normally, the lower 1 byte of the IP address used to identify the node device connected in the local area network is stored as the connection node IP address.
[0023]
Subsequently, the failure monitoring means 22 of the line switching device 1M transmits a check request message to each of the line switching devices 1A to 1K operating as slave devices via the A-system network 3A (step 101), and sets a transmission interval timer. It starts (step 102) and waits for a check response message from each of the line switching devices 1A to 1K as slave devices (step 103).
On the other hand, in the line switching apparatuses 1A to 1K which are slave devices, when a check request message is received from the A-system network 3A, each check response message is received by the monitoring correspondence means 24 via the A-system network 3A. Will be returned.
[0024]
In the failure monitoring means 22 of the line switching device 1M, if the check response message is received from each of the line switching devices 1A to 1K as slave devices (step 107) until the transmission interval timer expires (step 107: YES). The connection node IP address of the line switching device included in the check response message is acquired (step 105).
As shown in FIG. 4, the check response message includes a unique address 200 and a transmission source IP address 201 assigned to each transmission source line switching apparatus, and a destination IP address 202 of the transmission line switching apparatus 1M. In addition, the IP address of the node device connected to the node side line 3M of the line switching device acquired by the address acquisition unit 25, that is, the connection node IP address 205 is included.
[0025]
The failure monitoring unit 22 associates the connection node IP address acquired from the check response message with the unique address of the line switching device and stores it in the address table 16 of the storage unit 15 (step 106), and returns to step 103.
If the transmission interval timer has expired (step 107: YES), it is determined whether check response messages have been received from all slave devices. If check response messages have been received from all slave devices (step 107). 108: YES), it is determined that no failure has occurred in the A-system network 3A (step 109), and the process returns to step 101.
[0026]
On the other hand, if all check response messages have not been received by the time-up (step 108: NO), it is determined that there is a failure in the A-system network 3A (step 110). Then, the connection node IP address corresponding to the unique address of the line switching device that could not receive the check response message is read from the address table 16 of the storage unit 15 (step 111), and the failure occurrence notification including the acquired connection node IP address The message is transmitted to the monitoring apparatus 1M (step 112), and the process returns to step 101.
[0027]
In parallel with this, in the switching instruction unit 23 of the line switching apparatus 1M which is the master device, when the failure monitoring unit 22 determines that a failure has occurred, the A-system network 3A is used for data communication between the nodes and switches. Is required, and the line switching process shown in FIG. 6A is started.
In the line switching process, a line switching message is transmitted to each of the line switching apparatuses 1A to 1K (step 130), the line switching unit 11 of the line switching apparatus 1M is controlled, and the node side line 3M is transferred from the A-system network 3A to B. The connection is switched to the system network 3B (step 131), and the line switching process is terminated.
[0028]
On the other hand, in the switching instruction means 23 of each of the line switching devices 1A to 1K which are slave devices, when a line switching message is received from the master device in the line switching processing shown in FIG. 6B (step 135: YES) The switching unit 11 is controlled to switch and connect the node side line 3M from the A-system network 3A to the B-system network 3B (step 136), and the line switching process is terminated.
[0029]
As described above, when the line switching devices 1A to 1K operating as slave devices receive the check request message from the line switching device 1M operating as the master device, the line switching is performed using the communication system that has received the message. A check response message including the IP addresses of the node devices connected to the devices 1A to 1K is returned to the line switching device 1M, and the line switching device 1M converts the IP addresses included in these check response messages into the line switching device 1A. If the check response message cannot be received from any of the line switching devices 1A to 1K, the IP address corresponding to the line switching device 1A to 1K and the master line switching are indicated as information indicating the faulty part. A message including the IP address of the node device connected to the device is monitored. Since as transmitted to 2M, without highly functional nodes equipment can be quickly notified to identify the failed component of the fault in the network.
[0030]
Here, when specifying the faulty part, a method of specifying the faulty part using the unique address of the line switching apparatus can be considered. However, there is a case where the unique address of the line switching device is automatically set, and the correspondence with each part of the communication system is not fixedly guaranteed, and there is a problem that the faulty part cannot be specified. On the other hand, in this embodiment, focusing on the fact that the IP address of the node device is fixedly assigned, the node device connected to the duplex network via the line switching device as information for specifying the faulty part Since the IP address acquired from is used, the faulty part can be uniquely specified on the communication system.
[0031]
Note that there may be a case where a plurality of node devices are connected to the node side line of the line switching device. In such a case, a plurality of different IP addresses are acquired by the line switching device. However, these IP addresses are acquired only by the line switching device, and the fault monitoring according to the present embodiment monitors the range up to the two communication systems and the line switching device constituting the redundant network, that is, the range in the redundant domain. Therefore, any of these IP addresses can be used as information representative of the part of the line switching device.
[0032]
Next, an example of network failure monitoring processing by the communication system according to the present embodiment will be described with reference to FIG. FIG. 7 is a sequence diagram showing an example of network failure monitoring processing in the communication system according to the present embodiment.
Hereinafter, the fault monitoring process in the A-system network 3A will be described, but the fault monitoring process is also performed for the B-system network 3B in parallel with this.
[0033]
The line switching device 1M, which is the master device, transmits a check request message at predetermined transmission intervals to the line switching devices 1A-1K, which are slave devices, via the A-system network 3A (step 150). The check response messages from the devices 1A to 1K are received (step 151), the occurrence of a failure is monitored based on whether or not the check response message is received, and the connection node IP address included in the check response message is stored in the address table 16.
[0034]
Here, in response to the check request message transmitted from the line switching apparatus 1M (step 152), for example, when a check response message from the line switching apparatus 1B cannot be received before a predetermined transmission interval elapses from the transmission. (Step 153), it is determined that a failure has occurred (Step 154). If the A-system network 3A is used for data communication between nodes and needs to be switched, and the B-system network 3B can be switched without any failure, the line switching apparatus 1M to the line switching apparatuses 1A to 1K. A line switching message is transmitted (step 155). In response to this, each of the line switching apparatuses 1A to 1K and the line switching apparatus 1M switches and connects each node side line 3M from the A-system network 3A to the B-system network 3B (step 156).
[0035]
Further, the line switching apparatus 1M reads out the connection node IP address corresponding to the line switching apparatus 1B for which the check response message could not be received from the address table 16 (step 157), and sends a failure occurrence notification message including the connection node IP address. The data is transmitted to the monitoring device 2M (step 158).
In response to the failure occurrence notification message, the monitoring device 2M displays the connection node IP address included in the message on the screen and notifies the administrator. After that, when check response messages are received from all slave devices and failure recovery is confirmed, a failure recovery notification message is similarly notified from the line switching device 1M to the monitoring device 2M.
[0036]
FIG. 8 shows a failure notification screen display example.
Here, “Failure A is detected” is displayed in the “message” column as the content of the failure notification, and the slave line switching device and the master line switching device are displayed as specific failure portions in the “failure portion” column. “IP address: AAA.BBB.CCC.xxx to AAA.BBB.CCC.yyy” that can easily identify the node device corresponding to each is displayed. In the “line switching device operation status list” column, the operation status of each line switching device is displayed in detail. Here, “×” is displayed in the “A system” column of the line switching device unique address “01”, and the network A between the line switching device and the master line switching device having the unique address “00” is displayed. It can be seen that there is a failure part and the IP addresses of the corresponding node devices are “AAA.BBB.CCC.yyy” and “AAA.BBB.CCC.xxx”. In addition, “O” is displayed in the “B system” of the unique address “01” and the “Acquire unique address” column, the B system network between the line switching device is normal, and the line switching device is also It turns out that it is normal.
[0037]
In the above description, the case where the line switching device 1M operating as the master device is directly connected to the monitoring device 2M has been described as an example. However, the present invention is not limited to this, and the line switching device 1M and the monitoring device 2M As long as data communication is possible, the line switching device 1M and the monitoring device 2M may not be directly connected. For example, when the line switching device 1A is a master device and the line switching device 1M, which is one of the slave devices, and the monitoring device 2M are directly connected, the failure occurrence notification message is sent from the line switching device 1A to the A-system network. The failure notification screen shown in FIG. 8 is displayed on the monitoring device 2M via the 3A or B-system network 3B and the line switching device 1M, and the same effect as described above can be obtained.
[0038]
【The invention's effect】
As described above, when the slave line switching apparatus receives a check request message from the master line switching apparatus, the present invention is connected to the slave line switching apparatus using the communication system that has received the message. A check response message including the IP address of the node device is returned to the master line switching device, and the master line switching device manages the IP address included in the check response message from the slave line switching device for each slave line switching device. However, if the check response message cannot be received from any of the slave line switching devices, the IP address corresponding to the slave line switching device and the node device connected to the master line switching device as information indicating the failure part A message including the IP address is sent to the master line switching device. And since so as to transmit to the data communicable predetermined monitoring device without high performance line switching apparatus can be quickly notified to identify the failed component of the fault in the network.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a communication system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a line switching device.
FIG. 3 is a flowchart showing a network failure monitoring processing procedure in the line switching device of the master device.
FIG. 4 is a configuration example of a check response message.
FIG. 5 is a configuration example of an address table.
FIG. 6 is a flowchart showing a switching instruction process.
FIG. 7 is a sequence diagram illustrating an example of a network failure monitoring process in the communication system according to the embodiment.
FIG. 8 is a display example of a failure occurrence screen.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,1A-1K, 1M ... Line switching apparatus, 2, 2A-2K ... Node apparatus, 2M ... Monitoring apparatus, 3A ... A system network, 3B ... B system network, 3M ... Node side line, 11 ... Line switching part, DESCRIPTION OF SYMBOLS 12 ... Control part, 15 ... Memory | storage part, 16 ... Address table, 21 ... Operation | movement management means, 22 ... Fault monitoring means, 23 ... Switching instruction | indication means, 24 ... Monitoring response means, 25 ... Address acquisition means.

Claims (6)

A plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and node-side lines that are respectively provided between the node devices and the duplex network and connected to the node devices are connected to the 2 In a network failure monitoring method for monitoring a data communication failure in a communication system comprising a plurality of line switching devices that are switched and connected to a communication system having no failure among two communication systems,
Each of the line switching devices comprises one master line switching device that operates as a master device based on the master / slave method and one or more other slave line switching devices that operate as slave devices based on the master / slave method. ,
The master line switching device transmits a check request message to the slave line switching device independently for each communication system of the duplex network, and in response to this, the slave line switching device is used to transmit the check request message. Monitoring the occurrence of a failure in each communication system based on the presence or absence of a check response message sent back via the communication system,
When the slave line switching device receives the check request message from the master line switching device, the IP address of the node device connected to the slave line switching device using the communication system that received the message A check response message including: is returned to the master line switching device,
The master line switching device manages the IP address included in the check response message from the slave line switching device for each slave line switching device, and cannot receive the check response message from any slave line switching device. If a failure occurrence notification message including an IP address corresponding to the slave line switching device and an IP address of a node device connected to the master line switching device is provided as information indicating a failure part, the master line switching device A network failure monitoring method comprising: transmitting to a predetermined monitoring device capable of data communication with the network. The network failure monitoring method according to claim 1,
A network failure monitoring method, wherein the master line switching device manages an IP address included in the received check response message in association with a transmission source line switching device unique address of the check response message. A plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and node-side lines that are respectively provided between the node devices and the duplex network and connected to the node devices are connected to the 2 In a communication system composed of a plurality of line switching devices that are connected to a communication system that does not have a failure among the two communication systems,
Each of the line switching devices comprises one master line switching device that operates as a master device based on the master / slave method and one or more other slave line switching devices that operate as slave devices based on the master / slave method. ,
The master line switching device transmits a check request message to the slave line switching device independently for each communication system of the duplex network, and in response to this, the slave line switching device is used to transmit the check request message. A failure monitoring means for monitoring the occurrence of a failure in each communication system based on whether or not a check response message is returned via the communication system,
When the slave line switching device receives the check request message from the master line switching device, it uses the communication system that has received the message to use the IP address of the node device connected to the slave line switching device. A monitoring response means for returning a check response message including the master line switching device,
The failure monitoring means manages the IP address included in the check response message from the slave line switching device for each slave line switching device, and has not received the check response message from any slave line switching device In this case, a failure occurrence notification message including an IP address corresponding to the slave line switching device and an IP address of a node device connected to the master line switching device as information indicating a failure part is sent to the master line switching device. A communication system characterized by transmitting to a predetermined monitoring device capable of data communication. The communication system according to claim 3,
The communication system characterized in that the failure monitoring means manages an IP address included in the received check response message in association with a transmission source line switching device unique address of the check response message. A plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and node-side lines that are respectively provided between the node devices and the duplex network and connected to the node devices are connected to the 2 A communication system comprising a plurality of line switching devices that are connected to a communication system that does not have a failure in one communication system, and operates as one master device based on the master / slave system among the line switching devices, In the line switching device that manages one or more other slave line switching devices that operate as slave devices based on the slave method,
Sends a check request message to the slave line switching device independently for each communication system of the duplex network, and returns a response from the slave line switching device via the communication system used to transmit the check request message accordingly. Fault monitoring means for monitoring the occurrence of a fault in each communication system based on whether or not a check response message is received;
An address table for managing the IP address of the node device connected to the slave line switching device included in the received check response message for each slave line switching device;
If the failure monitoring unit fails to receive a check response message from any of the slave line switching devices in response to the transmitted check request message, the failure monitoring unit refers to the address table and corresponds to the slave line switching device. Predetermined monitoring for acquiring an IP address and enabling data communication between the failure occurrence message including the IP address as information indicating the failure part and the IP address of the node device connected to the master line switching device. A line switching device characterized by transmitting to a device. A plurality of node devices that perform data communication via a duplex network composed of two independent communication systems, and node-side lines that are respectively provided between the node devices and the duplex network and connected to the node devices are connected to the 2 A communication system comprising a plurality of line switching devices that are connected to a communication system that does not have a failure among the two communication systems, and each of the line switching devices operates as one or more slave devices based on a master / slave system, In the line switching device managed by one other master line switching device operating as a master device based on the master / slave method,
A check request message transmitted from the master line switching device is received independently for each communication system of the duplex network, and a check response message is sent to the master line switching device via the communication system that has received the check request message. The failure handling means to return,
Address acquisition means for acquiring an IP address of the node device from a packet exchanged by the node device via the node side line;
The failure handling means is an IP address acquired by the address acquisition means as information indicating a failure part notified from the master line switching device to a predetermined monitoring device capable of data communication with the master line switching device when a failure occurs. Is returned in the check response message.

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