JP2000278286A - Network system - Google Patents

Abstract

(57) [Summary] [Problem] The reliability of a network system is low. SOLUTION: Two networks independent of each other,
A plurality of node devices, and each of the plurality of node devices is configured to be connected to each of the two networks, and each node device is configured to connect a predetermined node device to the two networks. A monitoring device for monitoring a state, a route management device for managing a communication route between the node devices, and a communication between the node devices.
And a route resolution device for selecting one of the two networks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network system requiring high reliability, such as a plant monitoring and control system.

[0002]

2. Description of the Related Art FIG. 10 is a diagram for explaining the configuration of a conventional network system described in Japanese Patent Application Laid-Open No. 10-257036. The configuration and operation of the invention of FIG. 10 will be described. It is connected to both of the duplexed transmission lines 1a and 1b, performs processing for transmitting the same data to both of the transmission lines 1a and 1b when transmitting data, and transmits the transmission lines 1a and 1b when receiving data. A duplex control unit 6a for selecting one of the data having the same contents received from both of them, and in a duplex transmission device 2c for transmitting and receiving data using both of the transmission paths 1a and 1b, a predetermined specific external device When data is transmitted to one of the transmission paths 1a and 1b without passing through the duplex control means 6a, and when data is received from a specific external device, the transmission paths 1a and 1b are transmitted without passing through the duplex control means 6a. And a data passage path for receiving data from one of the two.

In the invention shown in FIG. 10, a packet is transmitted to both networks, and a packet arriving earlier on the receiving side is determined to be positive, or a packet determined to be normal by the normality determination information is determined to be positive.

[0004]

However, it is known that in a CSMA / CD system network, for example, Ethernet, the network becomes congested due to excessive transmission by a plurality of stations, and communication becomes impossible. In the invention of FIG. 10, since communication between applications is performed for both networks, both systems are simultaneously congested, and communication between both systems is stopped.

In the invention shown in FIG. 10, there is provided a method for distinguishing between a case where communication is performed via the duplex control means 6a and a case where direct communication is performed, depending on a method of specifying a network address.
It cannot respond to duplex communication terminal stations.

An object of the present invention is to obtain a highly reliable network system such as a plant monitoring and control system. Redundant communication service that provides a function to communicate with an appropriate route at the present time, that is, the main network of the main node side of the node duplex system by adopting a duplicate node device such as a controller or a duplicate network. Means and a highly reliable network system using the same.

[0007]

According to the present invention, there is provided a network system in which two independent networks, a plurality of node devices, and each of the plurality of node devices are connected to each of the two networks. Wherein each of the node devices comprises: a monitoring device that monitors a connection state between the determined node device and two networks; a route management device that manages a communication route between the node devices; In the communication between the devices, a route resolution device that selects one of two networks is provided.

[0008] The network system according to the present invention comprises:
In the two networks, one is a main network and the other is a standby network.
If the node device to be monitored detects a connection failure with the primary network of the two networks, the route resolution device determines whether the connection failure is due to a network single-system failure or a node device disconnection. If the connection failure is a single-system failure due to a primary network, the standby network is switched to a primary network, and the primary network is switched to a standby network,
Transmission is performed to each node device, and switching of the networks is suppressed until the connection state between the failed node device and the two networks is restored or eliminated.

[0009] The network system according to the present invention comprises:
Each node device is configured to wait or discard transmission to the corresponding node device when another node device detects a connection failure with the two networks.

[0010] The network system according to the present invention comprises:
A node device in which the state of the system is the main system, a node device of the standby system, and a duplicated node device having a switching device connected to the node device of the main system and the node device of the standby system; Each of the system node devices is configured to be connected to each of two networks, and each of the main node device and the standby node device detects a system switchover. And when the occurrence of switching is detected, an instruction is given by the switching device to switch the standby node device to the main node device.

[0011] The network system according to the present invention comprises:
The redundant node device includes a status management device that monitors the status of each other at regular intervals, and a switch notification device that notifies the network of a change in status of the node device that has been switched to the main system when the main node device has failed. Things.

[0012] The network system according to the present invention comprises:
When transmitting to the redundant node device, the node device sets the representative address designation of the communication destination as the address of the main node device, and associates the address of the main node device with the main network address.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a diagram for explaining a network system according to the present embodiment.
Specifically, it is a diagram for explaining a duplicated network device.

In FIG. 1, reference numerals 10a and 10b denote networks, respectively, and these two networks are integrated and referred to as a duplex network. In addition, network 10a is system A,
The network 10b is assumed to be a B system. The networks 10a and 10b are independent of each other. The connection topology may be any configuration such as a ring type or a bus type. 11a, 11b, 11
c,. . . 11n is a node device connected to the networks 10a and 10b, and plays the role of a network terminal.

Reference numeral 12 denotes a redundant communication service unit in each node device, which provides a communication service with another node device by the application 18. 13 is network 10
This is a monitoring device that monitors a and 10b. Reference numeral 14 denotes a route management device that manages a route to each node device connected to the network. Reference numeral 15 denotes a route resolution device that, when transmitting data to the node device of the communication destination, selects whether the communicable route is the network 10a or the network 10b, and specifies an address corresponding to the selected network. . A data communication device 16 communicates data. 17
Reference numerals a and 17b denote network interface devices that connect the networks 10a and 10b and the node device 11a.

Each node device includes a redundant communication service means 1
2. It has network interface devices 17a and 17b and a communication application 18. Redundant service communication means 12
Has a monitoring device 13, a route management device 14, a route resolution device 15, and a data communication device 16.

Next, the operation of FIG. 1 will be described. Networks 10a and 10b are independent networks,
The network interface devices 17a and 17b that connect each of the node devices 11a, 11b,..., 11n to the networks 10a and 10b have a network address for performing communication. For example, 4
Network 10a and 10b with octet IP address
Then, the sub-network address settings will be different. Inte
Except for the rnet Protocol, each has a network address defined by the protocol.

The redundant communication service means 12 includes a network
The connection status (entry / leave) between the node devices 10a and 10b and the other node devices 11a to 11n is monitored, and the connection status of each of the node devices 11a to 11n to the networks 10a and 10b is managed in a table. When the communication application 18 of a certain node device connected to the networks 10a and 10b communicates with another node device, the transfer request is sent to the redundant communication service means 12 by designating the address of the node device as the communication destination. 12 selects which of the network 10a and the network 10b is suitable for the communication route with respect to the address of the node device that is the communication destination, and specifies the address corresponding to the selected network (select the network, The operation of designating the corresponding network address is referred to as solving). The redundant communication service means 12 transmits data from the corresponding network interface device 17a or 17b to the resolved network address.

The monitoring device 13 of the redundant communication service means 12
The configuration of the other node devices connected to the networks 10a and 10b is monitored. By monitoring the entry / exit of a node device to be monitored, which is predetermined for each node device, at regular intervals, the entry / exit of the monitored node device to / from the networks 10a and 10b is detected. Each time a node device detects entry / exit of a monitored node device, the node device broadcasts the broadcast to the networks 10a and 10b to notify other node devices.

An example of this monitoring method is disclosed in Japanese Patent Application No. 11-8439. Each of the node devices 11a, 11b,. . . 11n sets a different node device or a plurality of node devices, which are predetermined in advance, as monitoring targets, and monitors entry / exit at regular intervals. Each node device 11
a, 11b,. . . When detecting the entry / exit of the node device to be monitored, 11n broadcasts the notification to other node devices via the network. Figure 1 shows this monitoring and notification.
Of the node device to the networks 10a and 10b, and sends the route management device 14 the entry / exit of the node device to / from the networks 10a and 10b.

The route management device 14 has a duplicated network management information table (also referred to as a route management table) for managing the joining / leaving status of the network interface devices 17a and 17b of each node device. The connection status between the network interface device 17a and the network 10a and the connection status between the network interface device 17b and the network 10b corresponding to each node device are recorded in the path management table. The recorded information is updated at any time by the information from the monitoring device 13.

The route resolution device 15 is a communication application
The network address that can actually communicate is obtained from the address of the node device that is the communication destination designated by 18. The address of the node device of the communication destination is specified by the node address specified in the communication application 18, and the data communication device
Send to 16. The data communication device 16 inquires of the route resolution device 15 about the node address, and the route resolution device 15 checks the node address of the communication destination node device for a network address that can be currently communicated, and obtains this.

An example of a method for setting a network address and a node address will be described for the Internet Protocol.
Now, the addresses of the node devices connected to the network 10a are 172.1.1.1 to 172.1.1.126, and the addresses of the node devices connected to the network 10b are 172.1.1.129 to 172.1.
1.254.

The address of the network 10a itself is set to 1
72.1.1.0, and the address of the network 10b itself is 172.1.0.
1.1.128. Further, the address used when performing broadcast notification of the node device connected to the network 10a using the network 10a is 172.1.1.127, and the address used when performing broadcast notification to the node device connected to the network 10b using the network 10b is
172.1.1.255

It is assumed that the node address of the node device sets an address system that is clearly different from the IP address of the network used. For example, the above IP
The address is equivalent to a class C IP address, but this address has been replaced with a reserved address class E.
~ 252.1.1.126 as the node address of the node device,
Alternatively, the reserved 0.0.0.1 to 0.0.0.126 may be used as the node address of the node device.

Here, the class indicates the network class of the IP address. Generally, the IP address ranks higher in the network scale (how many networks to use)
This is indicated by 4 bits. The network class is classified according to the information of the upper 4 bits.

An example in which a signal is transmitted from the node device 11a to the node device 11b will be described. In this case, the node device 11a
If both the networks 10a and 10b between the network 10a and the node device 11b are normal, the one of the networks 10a and 10b that is used regularly (the normal route) or the network with the higher priority (the priority route) is used. Select and specify the network address corresponding to the node address of the node device 11b connected to this network, and transmit. For example, if the network 10a is a preferential route, the node device 1
Sent from the network interface device 17a of 1a,
The data is received by the network interface device 17a of the node device 11b.

Now, when a failure occurs in the network interface device 17a of the node device 11b, the node device monitoring the node 11b sends the network interface device of the node device 11b to all the node devices connected to the network 10a. At 17a, a notification that a failure has occurred is provided. Each node device that has received the notification updates its route management table with information indicating that the node device 11b cannot use the network 10a.

The redundant communication service means 12 of the node device 10a
Means that when the communication application 18 transmits to the node device 11b, the network address of the network interface device 17b of the node device 11b is the current communicable network address from the path management table based on the destination node address of the node device 11b. Is checked and transmitted from the network interface device 17b of the node device 11a to the network interface device 17b of the node device 11b.

On the other hand, the failed node device 11b itself is monitored by the monitoring device 13 of the node device which monitors the node device 11b.
If a period monitoring signal is not received for a certain period of time, it is determined that the network interface device 17a of the node device 11b has failed, and the interface between the network 10a and all other node devices participating in the network system is withdrawn. To the route management device 14.
The route management device 14 of the node device 11b updates information indicating that all interfaces of the network 10a are to be disconnected in the route management table. Thereafter, all communication from the node device 11b starts to communicate via the path of the network 10b.

According to the network system of the present embodiment, the communication between the node devices is made redundant by the independent redundant networks, so that the reliability of the communication is improved. Since the node device independently checks the connection status between the monitored node device and the networks 10a and 10b, the system can be operated while constantly monitoring the connection status (entry / leave) between the node device and the network. Therefore, a highly reliable network system can be obtained.

Further, when each node device transmits data to another node device, it does not transmit data to both systems of the duplicated network. Therefore, both systems are unlikely to become congested at the same time, and the processing load of transmission and reception in each node device is reduced. In addition, the network failure due to excessive traffic does not occur in both systems of the duplex network at the same time. In addition, since each node device autonomously manages information related to route management using the information management table in the route management device 14 without concentrating the route management information on a specific server, it is necessary to consider the order of starting and stopping the network system. System can be operated without any problems.

The redundant communication service means 12 also monitors and manages the redundant configuration of the high-reliability network system. When the communication application 18 designates the destination address of the destination of the redundant configuration, the redundant communication service means 12 selects an appropriate route. The communication application 18 does not need to manage the occurrence of a failure or network switching.

Embodiment 2 The network system according to the present embodiment, when detecting a failure between one of the two network interface devices of the node device and the network (single-system failure), switches the communication path to the node device to the standby network, and Until the failure is recovered or eliminated, the network is not switched even if a connection failure of the node device is subsequently detected, thereby suppressing useless network switching. It becomes possible.

FIG. 2 is a diagram for explaining the network system according to the present embodiment, and specifically, is a diagram for explaining the operation of the route management device 14 of the node device. More specifically, FIG. FIG. 9 is a state transition diagram for explaining path management information that changes according to a connection state between a node device and a network.

When viewed from the node device that has already joined, the initial state of the other node device is the both-system leaving state and the node leaving state (500). Since network monitoring is performed independently and asynchronously on the networks 10a and 10b, network entry is detected for each system. After the node device enters / leaves the node device (510 or 520), the node device enters the dual system entry state (530). If the exit of one system is detected from the both system entry status, it cannot be determined immediately that it is a single system failure, so it transits to the node entry / exit status (510 or 520), and if the other system also detects the exit, a network failure occurs. The node is in the node detached state (500) due to the stoppage of the node device. If the other system is connected, it is determined that one node has failed (540 or 550) in the corresponding node device.

Since the entry monitoring of the node device is determined by a monitoring timeout of a certain period of time, if a certain period of time elapses during the joining or leaving of the node device and the determination is made by the monitoring timeout, a one-way failure (540 or 550) or the node withdrawal is always performed. Transition to the state (500). For unilateral disorders (540 or 550)
Network switching is performed, and switching is not performed because both systems have no effect on communication with other nodes.

In the operation of the redundant network, the system A (that is, the network 10a) is prioritized in the communication with the node device, and the system A and the system A are always used if the system A is available with the system B (that is, the network 10b) as a spare. There is a method to use B system only when it is not possible. In this case, which route of the A system or the B system is used depends on the node device that is the communication destination.
In FIG. 3, a first method is used in the case of a crossing failure, such as a failure of the network interface device 17a (not shown) of the node device 11b and the network interface device 17b (not shown) of the node device 11c. , The node device 11a communicates using the network 10b when transmitting to the node device 11b and using the network 10a when transmitting to the node device 11c. Node device 11b
Is the network 10a only, the node device 11c is the network
Since only 10b can be selected, the node device 11b and the node device
Communication with the node device 11c is not possible, but communication with a node device that does not cause crossing failure is possible.

As a second method, each node device uses either the A system or the B system as a main system (a network which is always used if available) regardless of the node device of the communication destination;
There is a method of selecting the other as a standby system (a network used when the main system is unavailable).

In this case, the route management unit 14 detects the presence or absence of a node having a network single system failure based on the state transition diagram of FIG. 2, and performs operation management of the network dual system. As shown in FIG. 3, in the route selection by the second method, since the main system is the network 10b, the network 1
Node device 11c with an interface failure of 0b
Cannot communicate with

FIG. 4 is a diagram for explaining the network system according to the present embodiment, and specifically, is a diagram for explaining the operation of the route management device 14 of the node device. More specifically, FIG. FIG. 9 is a state transition diagram for explaining path management information that changes according to a connection state between a node device and a network, and more specifically, a diagram showing a state transition of a switching operation of a redundant network.

In the normal state, each node is connected to both of the redundant networks, and either the A system or the B system is selected as the main system (600 or 700). The description will be made by taking an example in which the system A (that is, the network 10a) connected to the node device is the main network. A main system normal status (60
0), if the node device fails in system B, network B
As a system failure, the system A enters the system B failure state with the main system remaining (620). A
In the main system B failure state (620), when the system B recovers, the state of both the main system A and the normal system becomes normal (600).

Even if an A-system failure occurs from the A-main-system B-system failure state (620), the main system is not switched, and the switching does not occur until both systems recover to normal. In other words, A main system B system failure status (620)
In this case, if an A-system failure occurs, the A-system will remain in the dual-system failure state (630). A In the both main system failure state (630), A
When the system recovers, it becomes the A main system B failure state (620). When the B system recovers, it becomes the A system failure state (610) while the A main system recovers. When both systems recover, the A system main system double system normal state (600) ). If the A-system recovers from the A-main system A failure (610), the state becomes the normal state of both A-main systems (600). How to recover both systems,
Either repair the failure interface of the single-system failure node or stop the failure node.

When a failure in the A system occurs from the normal state of both the A system and the normal system (600), the network is switched to the main system and a transition is made to the B system A system failure (720). In this case as well, network switching does not occur until both systems are recovered, and the system remains in the B main system state. In a switchable state, that is, when both systems are normal, switching can be performed by a manual switching instruction.

Next, an example in which the B system (that is, the network 10b) connected to the node device is the main network will be described. If the node device becomes the A system failure in the B main system normal state (700), the A system failure state remains as the B main system as the network A system failure (720). In the B main system A failure state (720), when the A system recovers, it becomes the B main system normal state (700).

When a failure occurs in the A system from the normal state of both the A system and the dual system (600), the network is switched to the main system, and the state changes to the B system A system failure (720). In this case as well, network switching does not occur until both systems are recovered, and the system remains in the B main system state. In a switchable state, that is, when both systems are normal, switching can be performed by a manual switching instruction.

Even if the B-system fault occurs from the B-main system A-system fault state (720), the main system is not switched, and the switching does not occur until the two systems recover to normal. In other words, B main system A system failure status (720)
In this case, if a failure occurs in the B system, the B system becomes the both system failure state (730). B In the both main system failure state (730), B
When the system recovers, the B system becomes the A system failure state (720). When the A system recovers, the B system remains in the B system failure state (710). When both systems recover, the B system main system and both systems become normal (700). ). If the B system recovers from the B main B system failure (710), the B main system will be in the normal state (700). How to recover both systems,
Either repair the failure interface of the single-system failure node or stop the failure node.

When a failure occurs in the B-system single system from the B-main system normal status (700), the network is switched to the main system and a transition is made to the A-main system B system failure (620). In this case as well, network switching does not occur until both systems are restored, and the system remains in the A main system state. In a switchable state, that is, when both systems are normal, switching can be performed by a manual switching instruction.

According to the network system of the present embodiment, it is possible to judge and distinguish between the stop of the node device and the failure of the network half-way, so that an erroneous switching alarm relating to network switching is not notified. In addition, in the operation of a network system using a redundant network, meaningless network switching due to sporadic occurrence of multiple failures and communication errors due to the switching do not occur, and the connection failure with the node device is correctly recovered. There is an advantage that the influence of obstacles does not increase until then. Further, since the node device itself does not notify the other nodes that the network has been switched, there is no possibility that the switching notification is scattered when a network failure occurs and the traffic is deteriorated.

Embodiment 3 FIG. 5 is a diagram for explaining the configuration of the network system according to the present embodiment. In the figure, a node device 11a and a node device 11b have a node redundant configuration, one of which is a main node device, the other is a standby node device, and operates as a dual node device. The primary node device is a node device that transmits using this node device as long as it can be used, and the standby node device is a node that is used when the primary node device cannot be used due to a failure. Refers to the device. The primary node device has a corresponding standby node device.

Reference numeral 20 denotes a switching device for switching the system of the dual node device. The switching device 20 is connected to the main node device and the standby node device, and sends the status of each other to the main node device. When the first node device has failed, a main system activation instruction signal for making the standby node device the main node device is transmitted.
Reference numeral 21a denotes a state management device of the node device 11a, which also obtains and manages the operation state of the partner system from the system switching device. Reference numeral 21b denotes a state management device of the node device 11b, which also obtains and manages the operation state of the partner system from the system switching device.

Reference numeral 22a denotes a switching notification device which notifies other node devices connected to the networks 10a and 10b via the network interface devices 17a and 17b when the status of its own system is switched. 22b is a switching notification device, which is connected to the network when the status of its own system is switched.
The other node devices connected to 10a and 10b are notified via the network interface devices 17a and 17b.

Now, 11a is the primary node device, 11b is the standby node device, and the communication application 18 of the node device 11c designates the address of the primary node device as the representative address in the redundant node device, and It is assumed that it communicates with the node device 11a.

When a failure occurs in the main node device 11a,
When the state management device 21a detects a failure and transmits a failure stop signal to the switching device 20, the switching device 20 sends a main system instruction signal to the state management device 21b after the occurrence of a failure in the node device.
The switching notification device 22b receives the main system activation instruction signal from the status management device 21b, and performs broadcast notification to other node devices connected to the networks 10a and 10b.

The monitoring device 13 of the redundant communication service means 12 of another node device, for example, the node device 11c sends a signal notifying that the main node device has been switched from the switching notification device 22a of one of the redundant node devices 11a. Upon reception, the node devices 11a and 11a of the route management table in the route management device 14
Update the information in 1b. The communication application 18 of the node device 11c is the node device 11 configuring the redundant node device.
When communicating with a and 11b, it communicates only with the main node device. Therefore, the node address (representative node address) corresponding to the main node device is designated as the node address of the communication partner and sent to the data communication unit 16.

The data communication device 16 inquires of the route resolving device 15 which network address the representative node address corresponds to. The route resolving device 15 refers to the route management table of the route management device 14 and becomes the primary system. Obtain the network address of the current node device. Data communication device
Reference numeral 16 designates the network address of the main node device and transmits data.

In the case of a redundant network, a route resolution device
Reference numeral 15 associates the representative node address with the network address of a network interface that can be used by the main node device.

According to the network system of the present embodiment, since the node device is a redundant node device, even if a failure occurs in the main node device, the standby node device is switched to the main node device. Because you can send data,
A node device that is resistant to failure can be obtained. By managing the system status of the redundant node device with the route management table and reflecting the system switching notification from the redundant node device in the route management table, the communication application does not need to be aware of the switching of the redundant node device and the communication application Can communicate with other node devices.

Embodiment 4 FIG. If both node devices of the redundant node device become the master at the same time, the transmission source cannot resolve the route. However, when the main node device stops due to a failure, the state transition from the standby system to the main system is notified.
The status change is not transmitted from the failed main system. In the present embodiment, the switching notification device 22 of each node device of the dual system
And the monitoring device 13 constantly monitor the other party's state and exchange the state, and when the standby system notifies the master system, the other party (the failed main system) becomes non-main system and broadcasts the status of both systems. The route management unit 14 of the node device that has received the notification is configured to prevent the redundant node device from becoming the main system of both systems.

FIG. 6 is a diagram for explaining the network system of the present embodiment. In the redundant node device, the switching device, the status management devices 21a and 21b, and the switching notification device 22
It is a figure for explaining operation of 22a and 22b. In the figure,
The description of the redundant communication service means 12, the network interface devices 17a and 17b, and the communication application 18 is omitted. It is assumed that a redundant node device is configured by the node device 11a and the node device 11b. It is assumed that the network 10a as the A system is operating as the standby system, and the network 10b as the B system is operating as the main system (FIG. 6A). Since the switching notification unit 22a and the switching notification unit 22b transmit the initial state to the node that has detected each entry, each node device that joins the network obtains the operation state of the node device 11a and the node device 11b. I have. In the normal operation, the switching notification device 22a and the switching notification device 22b periodically transmit their respective states, and the monitoring device 13 of each node device receives the information and reflects it in the route management table (FIG. 6B). ).

FIG. 7 is a diagram for explaining the switching operation of the system when the network 10b as the system B has failed. In the figure, illustration of the redundant communication service means 12, the network interface devices 17a and 17b, and the communication application 18 is omitted. When the node device 11b fails, the switching device 20 detects the failure and detects the standby node device 11a.
Issue a mastering instruction to the status management device 21a (see FIG. 7).
(A)). At this time, the state management device 21a not only makes its own node device 11a the main system, but also makes the node device 11b that is the partner (failed main system) from the main system to the standby system, and The main system and the standby system of the node device 11b are notified (FIG. 7B). Further, according to the operation described in the first embodiment, the failed node device 1
1b network disconnection is detected, and broadcast notification is performed. The detection of the detachment of the node device 11b is not always the node device 11a, and the node device monitoring the node device 11b in the network 10 detects this and notifies other node devices. At this time, the network
Each node participating in 10a and 10b leaves the network using the node device 11b as a standby system (FIG. 7 (c)).

When the node device 11b in the main system state is properly stopped by the stop switch, the state management unit 21b does not send a failure signal to the switching device 20, so that system switching is not performed. The node device that monitors the entry / exit of the node device 11b to / from the networks 10a and 10b notifies the stop / exit of the node device 11b of the detection. In this case, the node device 11a
Is not used as the main system, the representative address of the duplicated node is treated as a detached state.

FIG. 8 is a diagram for explaining the network system of the present embodiment. Specifically, the node device 11
FIG. 13 is a diagram for explaining an operation when the network interface device 17 of b has failed. In the figure, redundant communication service means 12, network interface device
The description of 17a and 17b and the communication application 18 is omitted.

If there is no received signal for a certain period of time, it is determined that there is a failure in the network interface, and this is detected. At this time, the state management device 21b, in its own node device 11b,
It determines that a failure has occurred between b and b, and notifies the switching device 20. The switching device 20 outputs a main system command signal to the node device 11a. The switching notification device 21a of the node device 11a
The main system of a and the standby system of the node device 11b are connected to the network 10
Notification is made via a or 10b, and the node device connected to the networks 10a and 10b detects the switching of the system of the redundant node device (FIG. 8 (a)).

The detection of the detachment of the node device 11b is performed by a node device that monitors the node device 11b.
The notification is made via the networks 10a and 10b. Node device
If the detection of the network failure of the node 11b itself is performed before the detection of the detachment of the node device 11b, the detachment detection notification of the node device 11b is performed after the system switchover from the node device 11a is notified of the network, so that the networks 10a, 10b Each of the node devices connected to the server disconnects the node device 11b as a standby system (FIG. 8B).

If a network failure of the node device 11b is detected after the node device 11b that has been monitored by the node device 11b performs the disconnection detection, the node device 11a switches to the switching device 20 after the node device 11b withdraws. Receives a switching instruction from. However, since the state of the detached node device 11b is not changed, only the node device 11b itself becomes the main system. Since the node device 11b enters the standby state, when the network failure is recovered, the node device 11b enters the standby system (FIG. 8).
(C)).

In any case, since the node device 11a and the node device 11b do not simultaneously become the master, the other nodes in the network do not become unable to resolve the representative address.

In the network system according to the present embodiment, the entry / exit of the redundant node device is independently monitored, so that the node system can be used even in a single-system node state that is likely to occur during startup, shutdown, failure occurrence, maintenance, and the like. This has the advantage that communication with the device and management of the network system can be performed. Further, at the time of system switching, the new main system takes over the status change of the partner system status, so that it is possible to prevent each node of the network from having both systems of the redundant node device joining as the main system.

Embodiment 5 FIG. 9 is a diagram for explaining the network system of the present embodiment. Specifically, FIG. 9 is a diagram for explaining an example of a specific method for obtaining the representative address of the redundant node device in the route resolution device 15. It is.

When the communication destination node device is a redundant node device, the communication application 18 associates the designated representative node address with the node address of the main node device in which the redundant node device joins. If the node device at the communication destination is a single node device (not a duplicated node device), it is directly associated with the node address of the node device. Further, in the case of a duplicated network, the node address is associated with the network address of the main network. If the main node device has left, or if the node device has left the main operation network, the data communication unit 16 does not transmit because there is no communicable path.

The operation will be described using the IP protocol as an example. For example, the node addresses of the redundant node devices constituted by the node devices 11a and 11b are respectively 0.0.0.4 and 0.0.0.5.
And the representative node address is 254.0.0.4. These are not general class A, B, C, and D IP addresses, and can be easily distinguished as node addresses. here,
The class indicates the network class of the IP address. Also, the node address numbers of the redundant node devices are adjacent numbers and the last one bit is different. The representative node address is the lower 4 bits of the node address numbers of the two node devices constituting the duplicated node device, and the first 4 bits for classifying the IP address.
Was designated as Class E.

The route management table of the route management device 14 includes
It is assumed that the node device 11a has joined as a main node device and the node device 11b has joined as a standby node device. The route resolution device 15 associates 254.0.0.4 with the node address 0.0.0.5 of the node device 11a. Further, if the current main system of the network is the A-system, it is associated with the IP address 172.1.1.4 of the network interface 17a of the node device 11a, and the representative node address 25
Resolve 4.0.0.4 to 172.1.1.4. When an application 18 of a certain node device requests transmission to the redundant node device 254.0.0.4, the redundant communication service 12
Is transmitted to 172.1.1.4 via the network 10a.

Although the network address, node address and representative node address are the same 4-octet system,
Since the first four bits can be clearly distinguished, the communication application 18 can also perform communication by directly specifying a node address or a network address. In this case, the route solving device 15 solves a route of a necessary part.

As a method of setting the node address and the representative node address, an identifier other than 4 bits may be used as long as the representative address and the node address can be clearly identified.
Also, the address system need not be 4 octets, and if only 256 units are connected to the subnet, 9 bits obtained by adding 1 bit indicating the representative address to 8 bits of the node address can be sufficiently expressed.

If the communication application 18 is performing communication by designating the representative node address by the redundant communication service means 12, even if the switching of the node device and the switching of the network are performed, the communication of the primary node device is performed. Since communication is performed via the network, there is no need for the application to perform path management control for switching.

[0076]

According to the network system of the present invention, two independent networks, a plurality of node devices, and each of the plurality of node devices are connected to each of the two networks. A node device, a monitoring device that monitors a connection state between the determined node device and the two networks, a path management device that manages a communication path between the node devices, In the communication of (1), a route resolution device that selects one of the two networks is provided, so that information is not transmitted to both of the two networks, so that both are less likely to be in a congested state at the same time, and transmission / reception in each node device is not performed. The processing load is reduced, and network failure due to excessive traffic At the same time it does not even occur.

According to the network system of the present invention, in the two networks, one is a main network and the other is a standby network, and the monitoring device is configured such that a node device to be monitored is a network device of the two networks. When detecting a connection failure with the main network, the route resolution device determines whether the connection failure is due to a network single system failure or a node device disconnection, and the path failure is determined to be a single system failure due to the main network. If it is an obstacle,
The standby network is switched to the primary network and the primary network is switched to the standby network, and transmission to each node device is performed.
Even if a connection failure with one of the two networks occurs, data can be transferred.
Further, the monitoring device suppresses the switching of the network until the connection state between the node device having the failure and the two networks is restored or eliminated, so that the connection failure with the network occurs continuously. In addition, the meaningless network switching and the communication error accompanying the switching do not occur, and the influence of the failure does not increase until the connection failure with the node device is correctly recovered.

According to the network system of the present invention, there are provided a node device whose system status is the main system and a standby node device, and a switching device connected to the main node device and the standby node device. A redundant node device, wherein each of the main node device and the standby node device is configured to be connected to each of two networks, and wherein the main node device and the standby node device are connected to each other. Are equipped with a state monitoring device that detects the occurrence of switching of the system, and when the occurrence of switching is detected,
Since the switching device is instructed to switch the standby node device to the main node device, a node device that is resistant to failure can be obtained.

According to the network system of the present invention, the redundant node device includes a status management device that monitors the status of each other at regular intervals, and a node device that is switched to the main system when the main node device stops due to a failure. Is provided with a switching notification device that notifies the network of a state change, thereby preventing both of the two node devices constituting the redundant node device from joining the network as the main node device.

According to the network system of the present invention, when transmitting to the redundant node device, the node device specifies the representative address of the communication destination as the address of the main node device, and sets the address of the main node device as the address. Since it is associated with the main network address, communication with the main node device is performed via the main network, so that the application does not need to perform path management control for switching.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a network system according to an embodiment.

FIG. 2 is a diagram for describing a network system according to the present embodiment.

FIG. 3 is a diagram illustrating a network system according to the present embodiment.

FIG. 4 is a diagram illustrating a network system according to the present embodiment.

FIG. 5 is a diagram illustrating a network system according to the present embodiment.

FIG. 6 is a diagram illustrating a network system according to the present embodiment.

FIG. 7 is a diagram illustrating a network system according to the present embodiment.

FIG. 8 is a diagram illustrating a network system according to the present embodiment.

FIG. 9 is a diagram illustrating a network system according to the present embodiment.

FIG. 10 is a diagram for explaining a conventional network system.

[Explanation of symbols]

 10a, 10b: Network 11a to 11n: Node device 12: Redundant communication service means 13: Network monitoring device 14: Route management device 15: Route resolution device 16: Data communication device 17a, 17: Network interface device 18: Communication application 20: Switching devices 21a, 21b: status management devices 22a, 22b: switching notification devices

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Ikuyoshi Hiroshima 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Yukio Yaguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F term (reference) in Mitsui Electric Co., Ltd.

Claims (5)

[Claims] 1. A configuration in which two mutually independent networks, a plurality of node devices, and each of the plurality of node devices are connected to each of the two networks. A monitoring device that monitors a connection state between the determined node device and the two networks; a route management device that manages a communication route between the node devices; and a communication between the node devices, A network system, comprising: a route resolution device for selecting one of them. 2. The two networks, one of which is a main network and the other is a standby network, wherein the monitoring device is configured such that the node device to be monitored is connected to the main network of the two networks. If a connection failure is detected, the path resolution device determines whether the connection failure is due to a network single-system failure or a node device disconnection, and if the connection failure is a single-system failure due to the main network, the standby system Is switched to the primary network and the primary network is switched to the standby network, and transmission to each node device is performed. The connection state between the failed node device and the two networks is recovered or eliminated. 2. The network system according to claim 1, wherein the switching of the network is suppressed until the network is switched. Temu. 3. A node system having a node device whose system status is a main system, a node device of a standby system, and a redundant node device having a switching device connected to the node device of the main system and the node device of the standby system. Each of the standby node device and the standby node device
The main node device and the standby node device each include a state monitoring device for detecting occurrence of system switching, and are configured to be connected to each of the two networks. 3. The network system according to claim 1, wherein the switching device issues an instruction to switch a standby node device to a main node device. 4. A redundant node device comprising: a status management device for mutually monitoring the status at regular intervals; and a switching device for notifying the network of a status change of the node device switched to the main system when the main node device stops due to a failure. The network system according to claim 3, further comprising a notification device. 5. The node device, when transmitting to the redundant node device, designates a representative address of a communication destination as an address of a main node device, and associates the address of the main node device with a main network address. 5. The network system according to claim 3, wherein: