JP2021061478A - Relay device, relay system, and relay program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a redundant function of a relay device. SOLUTION: A communication network system 1 makes a relay device redundant by using a gateway device A and a gateway device B, and also makes a communication line redundant by using WAN 6 and WAN 7. The gateway device A periodically transmits an advertisement packet to the gateway device B, and the gateway device B receives the advertisement packet to monitor the gateway device A for any failure. If there is a failure, the gateway device B becomes the master device. Further, the gateway device A periodically transmits a ping to the server 9 and patrols the response to monitor the presence or absence of a failure in the WAN 6. When there is a failure, the gateway device A lowers the priority of its own device and notifies the gateway device B. The gateway device B receives this and becomes a master device. [Selection diagram] Fig. 1

Description

The present invention relates to a relay device, a relay system, and a relay program, for example, those having a redundant function.

The router and communication gateway device are placed between the network on the side that provides the communication service (usually the WAN side line) and the network on the side that enjoys the communication service (usually the LAN side line) so that the provision of the communication service is not interrupted. In order to do so, it may have a redundant function.
As a redundant function, one device accommodates multiple WAN lines, and when a line failure is detected, the WAN line to be used is switched, so-called line redundancy function, and a group is formed by multiple devices, one of which. A so-called device that operates the unit as a master device for the communication terminal on the LAN side and operates the rest as a backup device so that if the master device fails, one of the backup devices will take the place of the master device. There is a redundant function. A representative of the latter is the VRRP (Virtual Router Redundancy Protocol) defined by the RFC 5798 of the Internet Engineering Task Force (IETF).
Such a technique includes "router device and redundancy method" of Patent Document 1. This technique efficiently synchronizes the address translation information between the master router device and the backup router device.

By the way, the conventional communication gateway device supports only the line redundancy function or the device redundancy function.
In this case, in the device having the line redundancy function, if any line fails, none of the lines can be used, and in the device having the device redundancy function, if the line of the master device fails, all the terminals on the LAN side can receive the communication service. It will disappear.

Therefore, in order to realize the line redundancy function and the device redundancy function by the conventional technology, as shown in FIG. 6, two gateway devices having the line redundancy function and two gateway devices having the device redundancy function are combined and 4 By using a book line, it is possible to receive the benefits of both redundancy.

Here, the gateway devices 101a and 101b are gateway devices having a device redundancy function, and the gateway devices 105a and 105b are gateway devices having a line redundancy function.
When a failure occurs in the gateway device 101a (master) or the gateway device 105a (master), the gateway device 101b (backup) and the gateway device 105b (backup) secure communication between the terminal 5 and the server 9.
However, in this case, there is a problem that the cost increases and the risk of failure increases as the number of gateway devices increases.

JP-A-2017-5375

An object of the present invention is to enhance the redundant function of the relay device.

(1) In the invention according to claim 1, a third communication network is arranged between a first communication network connected to a server and a second communication network connected to a terminal, and is connected to the server. A master mode that relays communication between the server and the terminal, which is used together with another relay device arranged between the server and the second communication network, and a backup that backs up when a failure occurs in the relay process. It is a relay device that performs relay processing redundantly by switching the operation mode of the own device to either a mode or a mode, and is a priority storage means for storing priority and a priority to be stored in the other relay device. The priority notification means for notifying the order, the priority receiving means for receiving the notification of the priority stored in the other relay device from the other relay device, and the other received priority order. When the priority of the relay device is higher than that of the relay means for setting the own device to the master mode and performing relay processing, and the stored priority is lower than the priority of the other relay device received. In addition, a standby means for setting the own device to the backup mode and waiting for relay processing, a monitoring means for monitoring the line status of the first communication network while performing relay processing in the master mode, and the monitored line. When a failure occurs in the state, the changing means for changing the stored priority to a value lower than that of the other relay device, the changing order notification means for notifying the changed priority to the other relay device, and the like. Provided is a relay device characterized in that the above is provided.
(2) The invention according to claim 2 is characterized in that, when the failure is recovered, the stored priority is changed to a value higher than that of the other relay device and the other relay device is notified. The relay device according to claim 1 is provided.
(3) In the invention according to claim 3, when operating in the master mode, the control packet for causing the other relay device to monitor the operating state of the own device is transmitted via the second communication network. A control packet transmitting means that continuously transmits to another relay device and, when operating in the backup mode, continuously receive control packets transmitted by the other relay device via the second communication network. It is provided with a control packet receiving means and a mode switching means for switching the own device to the master mode when the interruption of the received control packet satisfies a predetermined condition when operating in the backup mode. The relay device according to claim 1 or 2 is provided.
(4) In the invention according to claim 4, the change order notification means includes the changed priority in the control packet transmitted by the control packet transmitting means, so that the other relay device has the priority. The relay device according to claim 3, wherein the relay device is provided.
(5) In the invention according to claim 5, the first communication network is a first WAN, the second communication network is a LAN, and the third communication network is a second WAN. The relay device according to any one of claims 1 to 4, wherein the relay device is provided.
(6) The invention according to claim 6 is a relay system using the first relay device and the second relay device according to claim 1 of any one of claims 1 to 5. , The first relay device and the second relay device are initially set with different priorities, and the first relay device connects to the first communication network connected to the server and the terminal. The second relay device is arranged between the second communication networks, and is characterized in that the second relay device is arranged between the third communication network connected to the server and the second communication network. To provide a relay system.
(7) In the invention according to claim 7, a third communication network disposed between the first communication network connected to the server and the second communication network connected to the terminal and connected to the server. A master mode that relays communication between the server and the terminal, which is used together with another relay device arranged between the second communication network and the second communication network, and a backup that backs up when a failure occurs in the relay processing. A relay program that causes a computer to function as a relay device that redundantly performs relay processing by switching the operation mode of the own device to either mode, and has a priority storage function for storing priorities, and the other above. The priority notification function for notifying the relay device of the priority to be stored, the priority reception function for receiving the notification of the priority stored by the other relay device from the other relay device, and the stored priority are , The relay function that sets the own device to the master mode and performs relay processing when the priority is higher than the priority of the other relay device that has been received, and the stored priority is the other relay device that has been received. A standby function that sets the own device to backup mode and waits for relay processing when the priority is lower than the above, and a monitoring function that monitors the line status of the first communication network while performing relay processing in master mode. , A change function for changing the stored priority to a value lower than that of the other relay device when a failure occurs in the monitored line state, and a notification of the changed priority to the other relay device. It provides a change order notification function and a relay program that realizes on a computer.

According to the present invention, the redundant function of the relay device can be enhanced by changing the priority among the relay devices.

It is a figure which showed an example of a communication network system. It is a figure for demonstrating the hardware configuration of a gateway device. It is a figure which showed the packet format of the advertisement packet. It is a flowchart for demonstrating the line redundancy function. It is a flowchart for demonstrating the device redundancy function. It is a figure for demonstrating the prior art.

(1) Outline of the Embodiment The gateway device (FIG. 1) of the present embodiment also realizes a line redundancy function by expanding the function of VRRP, which is a redundancy protocol that realizes the device redundancy function.
The communication network system 1 makes the relay device redundant by using the gateway device A and the gateway device B, and also makes the communication line redundant by using WAN 6 connected to the gateway device A and WAN 7 connected to the gateway device B. There is.

The initial values of the gateway devices A and B are set so that the priority of the gateway device A is higher than the priority of the gateway device B.
Therefore, if no failure occurs, the gateway device A relays the communication between the terminal 5 and the server 9 as the master device, and if a failure occurs, the gateway device B becomes the master device and the terminal 5 and the server. Take over the relay of the communication of 9.

More specifically, the gateway device A periodically transmits an advertisement packet to the gateway device B via the LAN 10, and the gateway device B constantly receives the advertisement packet to monitor the gateway device A for a failure. To do. If there is a failure, the gateway device B becomes the master device.
Further, the gateway device A periodically transmits a ping to the server 9 and receives the response to monitor the presence or absence of a failure in the WAN 6. When there is a failure, the gateway device A lowers the priority of its own device to the priority of the gateway device B and notifies the gateway device B. The gateway device B receives this and becomes a master device.

As described above, the gateway device A is arranged between the first communication network (WAN6) connected to the server 9 and the second communication network (LAN10) connected to the terminal 5 and connects to the server 9. A master mode that relays communication between the server 9 and the terminal 5, which is used together with another relay device (gateway device B) arranged between the third communication network (WAN7) and the second communication network. It functions as a relay device that performs relay processing redundantly by switching the operation mode of the own device to either a backup mode that backs up when a failure occurs in the relay processing. Here, the gateway device A and the gateway device B may be interchanged and read.

(2) Details of the Embodiment FIG. 1 is a diagram showing an example of a communication network system 1 according to the present embodiment.
The communication network system 1 is composed of a server 9, the Internet 8, WAN6, WAN7, a gateway device A, a gateway device B, a LAN 10, a terminal 5, and the like.
The server 9 is a server device that provides various services to the terminal 5 via a communication network, and provides various services such as provision of a web page, provision of a bank service, and provision of a video service.

The Internet 8 is the so-called Internet, which is a global information and communication network. The server 9 can communicate with the server 9 via the Internet 8.
WANs 6 and 7 are WANs (wide area networks) composed of mobile carrier networks operated by different business entities.

WAN 6 provides a communication path between the gateway device A and the server 9 via the Internet 8, and WAN 7 provides a communication path between the gateway device B and the server 9 via the Internet 8.
The communication network system 1 realizes a line redundancy function by selectively using WANs 6 and 7 such as using WAN7 when a failure occurs in WAN6.

The gateway device A is a relay device that relays the communication between WAN 6 and LAN 10, and the gateway device B is a relay device that relays the communication between WAN 7 and LAN 10.
As an example, the gateway devices A and B have a size of about 145 × 100 × 28 mm, a weight of about 270 g, and a flat plate shape.
The gateway device A and the gateway device B are the same except that the initial setting values of the priorities described later are different, and each of them corresponds to VRRP.

Hereinafter, when the gateway device A and the gateway device B are not particularly distinguished, they are simply referred to as a gateway device.
The gateway device may be a device compatible with VRRP, such as a router that connects a WAN and a LAN as in this example, or a router that relays indoor communication.
Further, in the present embodiment, two relay devices are used, but three or more relay devices may be used.

The LAN 10 is a LAN (local area network) that connects the gateway device A, the gateway device B, and the terminal 5.
The terminal 5 is composed of, for example, a general-purpose machine such as a personal computer and a dedicated machine such as an ATM (automatic teller machine) or a vending machine, and is a terminal device that uses the service provided by the server 9.

Here, VRRP will be described.
In VRRP, a group of a plurality of relay devices is virtually operated as one relay device, and when a master device performing relay processing in the VRRP group fails, another relay device in the group becomes a master. It is a device redundancy protocol that realizes a mechanism for continuing relay processing as a device.

Below, VRRP will be described in more detail using gateway devices A and B.
When the gateway devices A and B are installed in the communication network system 1 and started, they generate an advertisement packet (VRRP control packet) including the group number and priority set in the own device, and direct the advertisement packet (VRRP control packet) to another relay device. And multicast. In this way, the gateway device notifies each other of the group number, priority, and the like of the own device.

In this way, the gateway device receives the priority storage means for storing the priority, the priority notification means for notifying the other relay device of the stored priority, and the other relay device. It is provided with a priority receiving means for receiving the notification of the priority stored in the device.

The group number is a number that identifies the VRRP group of the gateway device to be virtualized, and among the gateway devices belonging to the same group, the master device and the backup device are determined from each other's priorities. In the communication network system 1, the gateway devices A and B form the same VRRP group.

The priority is a value that determines the priority (priority) of becoming a master device, and the gateway device having the highest value operates as a master device, and the others operate as a backup device in standby mode.

By multicast, gateway device A and gateway device B can recognize each other's priorities, and if the priority of their own device is higher than the other, they start operating as a master device, and if they are lower, they operate as a backup device. To start.

In this way, when the priority stored by the own device is higher than the priority of the other relay device received in the advertisement packet, the gateway device sets the own device to the master mode and performs relay processing. When the priority stored by the own device is lower than the priority of the other relay device received in the advertisement packet, the own device is set to the backup mode and the standby means for waiting for the relay process is provided. ..

In the example shown in FIG. 1, the priority of the gateway device A is set to 250 (initial value), and the priority of the gateway device B is set to 200 (initial value). Therefore, the gateway device A having a high priority value operates as a master device, and the gateway device B having a low priority value operates as a backup device.

When the gateway device A becomes the master device, it periodically generates an advertisement packet (every second in the present embodiment) and transmits the advertisement packet to the gateway device B via the LAN 10.
When the gateway device B serves as a backup device, the gateway device B monitors that the gateway device A is operating normally by receiving advertisement packets periodically transmitted from the gateway device A.

In this way, when the gateway device (relay device) is operating in the master mode, a control packet (advertisement packet) for causing another gateway device (relay device) to monitor the operating state of its own device is second. A control packet transmitting means that continuously transmits to another relay device via the network (LAN10) and a control packet transmitted by the other relay device when operating in the backup mode are continuously transmitted via the second network. It is equipped with a control packet receiving means for receiving the packet.

The gateway device B considers that the gateway device A has failed when the transmission of the advertisement packet by the gateway device A does not satisfy the predetermined condition (in the present embodiment, the advertisement packet cannot be received for 3 seconds). The mode is switched to the master mode, and the gateway device B starts operating as the master device.

When the gateway device B starts operating as a master device, the gateway device B takes over the VIP (Virtual IP) of the virtualization group, so that the communication with the terminal 5 is taken over and continued.
As described above, when the gateway device is operating in the backup mode, the gateway device is provided with a mode switching means for switching the own device to the master mode when the interruption of the control packet received from the master device satisfies a predetermined condition. ..

When the gateway device A recovers from the failure, the gateway device A transmits an advertisement packet to the gateway device B, but the gateway device B has a priority (250) included in the advertisement packet as its own device priority (250). 200) Recognizing that it is higher, it switches to the backup mode and becomes the backup device again.

The above is the outline of the redundancy of the relay device by VRRP. As described above, the gateway devices A and B operate as one grouped VRRP virtual router by using the VIP for the communication on the LAN10 side.
Further, the gateway devices A and B of the present embodiment correspond to VRRP conforming to RFC5798, which is the latest standard at present.

In the present embodiment, the VRRP described above is extended to support the redundancy of the communication line using WANs 6 and 7. This extension will be described below.
The gateway device A, which is the master device, periodically (every second in the present embodiment) transmits a ping to the server 9 via the WAN 6 while relaying the communication. A ping is an ip packet used to confirm communication in a communication network.

Then, the gateway device A can confirm that the WAN 6 has no failure by receiving the ping response from the server 9.
Since the reason for pinging is to know the state of WAN6, it may be performed for a server other than the server 9.
Further, for example, another method may be used, such as measuring the line speed of WAN 6 to check the line state.
As described above, the gateway device includes a monitoring means for monitoring the line state of the first network while performing relay processing in the master mode.

Then, when the response of the ping does not satisfy the predetermined condition (when there is no response for 3 seconds in the present embodiment), the gateway device A may have failed in WAN6, and therefore sets the priority of its own device to the gateway. Change to a value lower than the priority of device B, for example, from 250 to 100.
In this way, the gateway device is provided with a changing means for changing the priority of the stored own device to a value lower than that of other relay devices when a failure occurs in the monitored line state.

As the priority after the change, a value lower than the priority of the gateway device B may be stored in the gateway device A in advance and used, or the priority of the gateway device B may be used when determining the master device. Since it has been obtained, a value lower than this may be automatically set.
As described above, in the conventional VRRP, a fixed value is used for the priority, but in the present embodiment, this can be dynamically changed according to the failure of the communication line.

Since the gateway device A lowers the priority to 100, the priority included in the advertisement packet transmitted by the gateway device A to the gateway device B becomes 100. As a result, the gateway device A can notify the gateway device B of the updated priority.
Upon receiving this, the gateway device B recognizes that its own device has a higher priority and starts operating as a master device.

As described above, the gateway device includes a change order notification means for notifying another gateway device (relay device) of the changed priority, and the change order notification means is used for the control packet transmitted by the control packet transmitting means. By including the changed priority, the other relay device is notified of the priority.

In this way, when the gateway device A detects a failure in WAN 6, the priority of its own device is lowered from that of the gateway device B, so that the gateway device B is set to the gateway device B after about 1 second (because the advertisement packet is transmitted in a 1-second cycle). It can be operated as a master device.

After that, the gateway device B acts as a master device, transmits an advertisement packet to the gateway device A, and transmits a ping to the server 9 via the WAN 7 to check the line status.
With such a line redundancy function of the communication network system 1, the terminal 5 can access the server 9 via the WAN 7 even if a failure occurs in the WAN 6.

In this way, after switching the master device to the gateway device B in the VRRP group, the gateway device B may continue to be used as the master device as it is, but when the failure of WAN6 is resolved, the gateway device A becomes the master device. It can also be configured to return.

In this case, for example, it is configured as follows.
The gateway device A continues to transmit the ping to the server 9 even after the priority is lowered, and when the ping transmission is successful, that is, when it can be confirmed that the failure of WAN6 has been resolved, the priority is set to the gateway device B. The value is changed to a value higher than the priority, and the advertisement packet including the changed priority is transmitted to the gateway device B.
In this case, when the failure is recovered, the gateway device A changes the stored priority of its own device to a value higher than that of the other relay device and notifies the other relay device.

Then, since the priority of the gateway device A is higher than the priority of the own device, the gateway device B returns to the backup device and stops the transmission of the advertisement packet.
The gateway device A confirms that it does not receive the advertisement packet from the gateway device B for 3 seconds, and starts operating as the master device.

As described above, the communication network system 1 is a relay system using the first relay device (gateway device A) and the second relay device (gateway device B), and is the first relay device and the second relay device. Different priorities are initially set for the relay device, and the first relay device is located between the first communication network (WAN6) connected to the server and the second communication network (LAN10) connected to the terminal. The second relay device constitutes a relay system arranged between the third communication network (WAN7) connected to the server and the second communication network. The gateway device A and the gateway device B, and WAN6 and WAN7 may be replaced with each other.

As a result, in the normal state, the terminal 5 communicates with the server 9 via the gateway device A and WAN 6 operating as the master device, and when the gateway device A fails, the gateway device B becomes the master device. Therefore, the terminal 5 can communicate with the server 9 via the gateway device B and the WAN 7 (device redundancy function).

Furthermore, when a failure occurs in WAN6 (when there is no ping response for a certain period of time), the gateway device A detects the line failure and lowers the priority until the WAN6 failure is recovered to become a backup device, while the gateway. When the device B becomes the master device, the terminal 5 communicates with the server 9 via the gateway device B and the WAN 7 (line redundancy function).
In this way, in the communication network system 1, device redundancy and line redundancy are improved by newly using the device in the same VRRP group that has not failed and the device that has not failed in the line as the master device. Can be enhanced.

FIG. 2 is a diagram for explaining a hardware configuration of the gateway device.
The gateway device A is configured by connecting a CPU (Central Processing Unit) 21, a ROM (Read Only Memory) 22, a RAM (Random Access Memory) 23, a WAN communication unit 24, a LAN communication unit 25, and the like via a bus line. ..

The CPU 21 is a central processing unit that performs various calculations and controls each part of the gateway device A according to a relay program stored in the ROM 22.
In the present embodiment, when the relay program is executed, the CPU 21 has (1) a function of comparing the priority of each other with other gateway devices via LAN10, and (2) in the master mode when the priority of the own device is high. A function that operates in backup mode when it is low, (3) a function that relays communication between LAN10 and WAN6 when operating in master mode, and (4) a function that operates in master mode A function to periodically send an advertisement packet to another gateway device, (5) a function to periodically send a ping to the server 9 to monitor the line status of WAN6, and (6) when there is no response of the ping for a predetermined time. A function to determine that a failure has occurred in the line status of WAN6, lower the priority than other gateway devices and notify other gateway devices, (7) WAN6 that has failed has recovered and there was a ping response. In this case, increase the lowered priority (return to the original initial value or change it to a value higher than the priority of other gateway devices), and operate in master mode again, (8) operate in backup mode. A function to monitor that advertisement packets are periodically sent from the master device when the gateway is running. (9) When operating in the backup mode and there is no advertisement packet from the master device for a predetermined time, It realizes functions such as a function that switches to master mode and operates.

The ROM 22 is a read-only memory, and is composed of, for example, an EEPROM (Electrically Erasable Program Read-Only Memory), and stores basic programs and parameters for operating the CPU 21.
In the present embodiment, EEPROM is used as ROM 22, and for example, in addition to the relay program, the initial value of the priority set for the own device is stored. The initial value of this priority and the relay program are set in the RAM 23 at startup.

The RAM 23 is a memory that the CPU 21 can read and write, and provides a working memory when the CPU 21 performs relay processing in the master mode (backup mode when a WAN 6 failure occurs).
The RAM 23 stores, for example, a priority set in the ROM 22 as an initial value, a changed priority when a failure occurs, and the like. In the example of the figure, 250 is stored as the initial value of the priority, and when a failure occurs, it is updated to the changed value of 100.

The WAN communication unit 24 connects the gateway device A to the WAN 6 and communicates with the server 9 via the Internet 8.
The connection with the WAN 6 is compatible with both wired and wireless, and therefore, the WAN communication unit 24 is provided with a wired connection port and a wireless connection antenna.
The LAN communication unit 25 connects to the LAN 10 and communicates with the terminal 5. The connection with the LAN 10 also supports both wired and wireless, and the LAN communication unit 25 also has a wired connection port and a wireless connection antenna.
The above configuration is common to the gateway devices A and B.

FIG. 3 is a diagram showing a packet format of an advertisement packet.
As shown in the figure, the advertisement packet is composed of fields such as "Version", "Type", "Vertical Tr ID", "Priority", and the like.
Of these, the "Virtual Rtr ID" is a field for storing the VRRP group number.
"Priority" is a field for storing the priority, which was conventionally a fixed value, but the gateway device dynamically changes this, for example, changing the initial value of 250 to 100. be able to.

FIG. 4 is a flowchart for explaining the line redundancy function of the communication network system 1.
The following processing is performed by the CPUs of the gateway device A, the gateway device B, and the server 9.
The gateway device A operates as a master device by default, and the gateway device B operates as a backup device.

As an example, the RAM 23a of the gateway device A stores an initial value of 250 as a priority, and the RAM 23b of the gateway device B stores an initial value of 200 as a priority.
As described above, for example, the gateway device A has a RAM 23a, the gateway device B has a RAM 23b, and the like, and the components of the gateway device A have a subscript a, and the components of the gateway device B have b. I will add a subscript to distinguish them.

The gateway device A drives the WAN communication unit 24a to relay the communication between the terminal 5 and the server 9, and transmits a ping to the server 9 every second to perform a communication confirmation process by the ping (step 5).
The gateway device A continuously performs this process while there is a normal response from the server 9, and if there is an abnormality (3 seconds have passed since the last response), there is a possibility that WAN 6 has failed. Therefore, the gateway device A changes the priority stored in the RAM 23a from the initial value of 250 to a value lower than the priority of the gateway device B, for example, 100 (step 10).

Next, the gateway device A records the changed priority in the field of the advertisement packet, drives the LAN communication unit 25a, and transmits this to the gateway device B via the LAN 10, thereby transmitting the changed priority to the gateway. Notify device B (step 15).
On the other hand, the gateway device B receives the advertisement packet of the gateway device A via the LAN communication unit 25b, and stores the priority (here, 100) recorded in the advertisement packet in the RAM 23b. Then, the gateway device B is compared with the priority (100) of the gateway device A and the priority of its own device (200 in this case) also stored in the RAM 23b (step 20).

Based on the comparison, the gateway device B recognizes that the priority (200) of its own device is higher than the priority (100) of the gateway device A, and starts the operation in the master mode (step 25).
As a result, the gateway device B connects to the WAN 7 from the WAN communication unit 24b, and takes over the relay of the communication between the terminal 5 and the server 9 from the gateway device A.

Then, since the gateway device B has become the master device, the priority (200) of the own device is included in the advertisement packet, and this is transmitted from the LAN communication unit 25b to the gateway device A via the LAN 10 every second. As a result, the gateway device B notifies the gateway device A of the priority of its own device (step 30).

When the gateway device A receives the advertisement packet from the gateway device B via the LAN communication unit 25a, the gateway device A stores the priority (200) recorded therein in the RAM 23a.
Then, the gateway device A compares this with the priority (100) of the own device changed in step 10 which is also stored in the RAM 23a (step 35), and the priority of the own device is higher than the priority of the gateway device B. Since it is also low, the mode is changed from the master mode to the backup mode, and the operation in the backup mode is started (step 40).
After that, the gateway device B continues to operate as the master device.

The gateway device B operates in the master mode even when the failure of WAN 6 is resolved, but the gateway device A may be configured to return to the master device when the failure of WAN 6 is resolved.
When the gateway device A returns to the master mode, for example, the following is performed.
The gateway device A periodically transmits pings to the server 9 while operating in the backup mode. That is, the gateway device A continuously transmits a ping to the server 9 even after confirming the failure of the WAN 6.

Then, when the ping response continues from the server 9, the gateway device A determines that the failure of WAN6 has been resolved, reads the initial value (250) of the priority stored in the ROM 22a, and stores it in the RAM 23a. The memorized changed priority value is updated from 100 to the initial value (250).
When the gateway device A returns to the master mode by resolving the failure of WAN6, the priority value stored in the RAM 23a is the priority recorded in the advertisement packet transmitted from the gateway device B currently operating in the master mode. It may be higher than (200). Therefore, as described above, the gateway device A sets the priority stored in the RAM 23a to a value higher than the priority 200 of the gateway device B, for example, 220, in addition to updating the priority stored in the RAM 23a to the initial value (250) of the ROM 22a. You may update it.

After updating the priority value of the RAM 23a, the gateway device A waits for receiving an advertisement packet from the gateway device B. When the priority value of the received advertisement packet is smaller than the priority value of the RAM 23a, the mode shifts to the master mode, the updated priority (250) is recorded in the advertisement packet and transmitted to the gateway device B.
Then, the gateway device B recognizes that the priority (250) of the gateway device A is higher than the priority (200) of its own device, and shifts to the backup mode.

FIG. 5 is a flowchart for explaining the device redundancy function of the communication network system 1.
This procedure is the same as that for normal VRRP.
The gateway device A operates as a master device, and the gateway device B operates as a backup device.

First, the gateway device A generates an advertisement packet in the RAM 23a and transmits it from the LAN communication unit 25a to the gateway device B every second, while the gateway device B receives this, so that the gateway device A is normal. The process of confirming that the device is operating (= master device confirmation process) is continuously performed (step 50).
When the gateway device B confirms the abnormality of the gateway device A in the master device confirmation process (when 3 seconds have passed since the gateway device B received the last advertisement packet), the gateway device B changes from the backup mode to the master mode. The operation is changed to the above, and the operation in the master mode is continued thereafter (step 55).

As described above, in the communication network system 1, the line failure detection function is linked to the device redundancy function, and when a failure is detected in the communication of the WAN line to which the relay device is connected, the same operation as when the device fails. Or, it is possible to positively perform a backup operation and urge the communication terminal on the LAN side to switch to a device in which a failure has not occurred in the WAN side line.

The following modification is also possible. The gateway device A stops transmitting the advertisement packet instead of changing the priority when the failure of WAN6 is detected.
The gateway device B detects that the advertisement packet is not transmitted and automatically becomes the master device. However, in this case, it takes 3 seconds (when the advertisement packet is transmitted in a 1-second cycle) to switch the master device. Therefore, when used in a business that requires speed and reliability, it is desirable to rewrite the priority as described in this embodiment.

In the embodiment described above, the following effects can be obtained.
(1) By linking the line failure detection function with the device redundancy function, the advantages of the line redundancy function and the device redundancy function can be enjoyed by a gateway device having a minimum of two units.
(2) Since the line redundancy function and the device redundancy function can be realized by the gateway device having a minimum of two units, the cost and the installation space can be significantly reduced, and the redundant function configuration has been conventionally provided due to the cost and the installation space. Even systems that could not be adopted can be easily introduced.
(3) Since VRRP is used, it is not necessary to install special software in the LAN side communication terminal, and the conventional IP compatible device can be used as it is.

A, B Gateway device 1 Communication network system 5 Terminal 6, 7 WAN
8 Internet 9 Server 10 LAN
21 CPU
22 ROM
23 RAM
24 WAN communication unit 25 LAN communication unit 101, 105 Gateway device

Claims (7)

It is arranged between the first communication network that connects to the server and the second communication network that connects to the terminal, and is arranged between the third communication network that connects to the server and the second communication network. The operation mode of the own device is either a master mode that relays communication between the server and the terminal, which is used together with other relay devices, or a backup mode that backs up when a failure occurs in the relay process. It is a relay device that makes relay processing redundant by switching between.
Priority storage means for storing priorities and
A priority notification means for notifying the other relay device of the stored priority, and
A priority receiving means for receiving a priority notification stored in the other relay device from the other relay device, and a priority receiving means.
When the priority to be stored is higher than the priority of the other relay device that has been received, the relay means that sets the own device to the master mode and performs relay processing.
When the stored priority is lower than the priority of the other relay device that has been received, the standby means that sets the own device to the backup mode and waits for the relay process.
A monitoring means for monitoring the line status of the first communication network while performing relay processing in the master mode,
A changing means for changing the stored priority to a value lower than that of the other relay device when a failure occurs in the monitored line state.
A change order notification means for notifying the other relay device of the changed priority, and
A relay device characterized by being equipped with. The relay device according to claim 1, wherein when the failure is recovered, the stored priority is changed to a value higher than that of the other relay device and the other relay device is notified. When operating in the master mode, a control packet for continuously transmitting a control packet for causing the other relay device to monitor the operating state of the own device to the other relay device via the second communication network. Transmission means and
When operating in the backup mode, the control packet receiving means for continuously receiving the control packet transmitted by the other relay device via the second communication network, and the control packet receiving means.
When operating in the backup mode, a mode switching means for switching the own device to the master mode when the interruption of the received control packet satisfies a predetermined condition, and
The relay device according to claim 1 or 2, wherein the relay device is provided. The third aspect of the present invention is characterized in that the change order notification means notifies the other relay device of the change order by including the changed priority in the control packet transmitted by the control packet transmission means. The relay device described. The first communication network is a first WAN, the second communication network is a LAN, and the third communication network is a second WAN, according to claim 1. The relay device according to claim 1 of any one of item 4. A relay system using the first relay device and the second relay device according to any one of claims 1 to 5.
Different priorities are initially set for the first relay device and the second relay device.
The first relay device is arranged between a first communication network connected to a server and a second communication network connected to a terminal.
The second relay device is a relay system characterized in that it is arranged between a third communication network connected to the server and the second communication network. It is arranged between the first communication network that connects to the server and the second communication network that connects to the terminal, and is arranged between the third communication network that connects to the server and the second communication network. The operation mode of the own device is either a master mode that relays communication between the server and the terminal, which is used together with other relay devices, or a backup mode that backs up when a failure occurs in the relay process. It is a relay program that makes a computer function as a relay device that performs relay processing redundantly by switching between.
Priority memory function to memorize priority and
A priority notification function for notifying the other relay device of the stored priority, and
A priority reception function that receives notification of the priority stored in the other relay device from the other relay device, and a priority reception function.
A relay function that sets the own device to the master mode and performs relay processing when the priority to be stored is higher than the priority of the other relay device that has been received.
When the stored priority is lower than the priority of the other relay device that has been received, the standby function that sets the own device to the backup mode and waits for the relay process.
A monitoring function that monitors the line status of the first communication network while performing relay processing in master mode,
A change function for changing the stored priority to a value lower than that of the other relay device when a failure occurs in the monitored line state.
A change order notification function for notifying the other relay device of the changed priority, and a change order notification function.
A relay program that realizes on a computer.

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