JPH063907B2 - Back-up method of gateway - Google Patents

Description

The present invention relates to a network system in which a plurality of networks are interconnected by gateways, and more particularly to a backup method for a working gateway by a backup gateway when a failure occurs in the working gateway.

[Conventional technology]

The gateway is a local area network (LA
N) Used for mutual connection and mutual connection between LAN and public line. In recent years, with the development of LANs and the like, the reliability of gateways used to interconnect these networks has become very important. For this reason, it has become common to install two sets of gateways, one of which is an active machine and the other of which is a standby machine, and when a failure occurs in the active machine, the standby machine backs up the active machine.

Known documents related to the gateway include, for example, JP-A-59-62245 and JP-A-60-91.
No. 745 is cited.

[Problems to be solved by the invention]

Normally, the active machine sends a signal to the standby machine at regular time intervals to notify that it is operating normally.When the standby machine stops the signal, the active machine determines that the active machine has failed and performs a backup operation. Will be moved to. However, the current machine may be normal, but the above signal may not be detected on the standby machine side due to a network failure or an abnormality in the signal monitoring unit of the standby machine. In the prior art, when the signal from the working machine is no longer detected, the backup machine immediately shifts to the backup operation, which may cause the working machine to be mistakenly switched to the backup machine even though the working machine is normal. was there.

An object of the present invention is to prevent a backup gateway from accidentally shifting to a backup operation in a network system in which a plurality of networks are interconnected by a current / backup gateway, even if the current gateway is normal. is there.

[Means for solving problems]

According to the present invention, a working / standby gateway for interconnecting a plurality of networks is provided with means for monitoring the operation of a partner gateway through each network.

[Action]

The working gateway and the backup gateway are connected in a loop through two networks, and a signal indicating that the working gateway is operating normally arrives at the backup gateway through the respective networks. The backup gateway starts the backup operation only when it detects an abnormality in the working gateway through one network and also detects an abnormality in the working gateway through another network. As a result, it is possible to prevent the standby gateway from erroneously recognizing a normal working gateway as an abnormality and erroneously shifting to the backup operation due to an abnormality in the network system on one side.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the system configuration of an embodiment of the present invention. First
In the figure, a ring-type network 1 and a bus-type network 2 are connected by a working gateway (hereinafter, simply referred to as a working machine) 3 and a backup gateway (hereinafter, simply as a standby machine) 4. A terminal group 5 is connected to the network 1, and a terminal group 6 is connected to the network 2. The communication control method of the networks 1 and 2 may be any method.

The active device 3 and the standby device 4 have different terminal addresses in the networks 1 and 2, respectively, and the active device 3 sends the standby device 4 a frame 7 indicating "normally operating as the active gateway device". It is sent at regular intervals. This frame 7 is transmitted independently on the networks 1 and 2.

When an abnormality occurs in its own station, the active machine 3 will use the network 1
The service function as a gateway is stopped in both the first and the second, and the frame transmission to the standby device 4 is also performed in the networks 1 and 2.
Stop at both. When the standby device 4 detects a frame timeout from the active device 3 in the network 1 first, the standby device 4 also receives “normal operation” from the active device 3 in the network 2.
If you have received a frame indicating
After the self-test of the own station, the backup operation of the active machine 3 is started. If a frame indicating "normal operation" is received in the network 2, it is determined that an error has occurred on the network 1 side of the standby device 4, and if an error is displayed, the operation of the local station is stopped. Therefore, the backup operation of the active machine 3 is not started.

FIG. 2 shows a specific configuration example of the active machine 3 and the standby machine 4. In FIG. 2, A is the configuration on the network 1 side, and B is the configuration on the network 2 side.

The signal line from the left side of the network 1 is connected to one input of the selection circuit 15 and one of the contacts b of the relay circuit 21.
It is connected to the. A signal line from the right side of the network 1 is connected to the other input of the selection circuit 15, and the signal line is also connected to the output a of the relay circuit 21. Relay circuit 2
The contact c of 1 is connected to the output of the transmission circuit 16a. The input of the transmission circuit 16a is connected to the serial output of the sub CPU 11, and the output of the reception circuit 14a is connected to the serial input of the sub CPU 11. Sub CPU 11 is main C
Data is exchanged with the main CPU 11 via the bus of the PU 13. The output of the reset latch 17a is the sub CPU
11 is connected to the reset terminal and the contact switching control terminal d of the relay circuit 21, and the set terminal s of the reset latch 17a is connected to the output of the OR circuit 18a. O
The two inputs of the R circuit 18a are respectively connected to the sub CPU 11
And the latch set signal 20 from the main CPU 13.

The configuration of the network 2 side is almost the same as that of the network 1 side. The difference from the network 1 side is that the topology of the network 1 is a ring, whereas the network 2 is a bus, so that the bypass control relay circuit 21 and the selection circuit 15 are not provided. . The transmission circuit 16b on the network 2 side is in a high impedance state at the time of power-off or non-transmission and can be electrically disconnected from the network 2.

Next, the backup operation in FIG. 2 will be described.

During normal operation, the active machine 3 individually transmits a frame indicating “normal operation” to the standby machine 4 on the network 1 side and the network 2 side, respectively, while servicing the interworking between the network 1 and the network 2. is doing. The frame may be an instruction command for resetting the monitoring timer of the standby device. The transmission of the frame indicating the "normal operation" is
In the active machine 3, the main CPU 13 to the sub CPU 11
And 12 are instructed separately. Based on the instruction, the sub CPUs 11 and 12 transmit a frame indicating "normal operation" to the respective networks 1 and 2, and at the same time, the receiving circuit 1
The frame is received by 4a or 14b, and a self-loop test is also performed by checking the comparison with the transmitted frame. At this time, the selection circuit 15 in the preceding stage of the reception circuit 14a on the network 1 side is instructed to select the output a of the relay circuit 21. When the self-loop test is completed, the sub CPUs 11 and 12 send the result to the main CPU.
Report to PU13. The main CPU 13 is a sub CPU
The reports from 11 and 12 are checked, and if normal, the process proceeds to the next processing operation.

In the standby unit 4, the sub CPUs 11 and 12 respectively monitor the frame from the active unit 3 by a timer to check the normality of the content of the frame.

In the active machine 3 and the standby machine 4, the main CPU 13 and the sub CPUs 11 and 12 monitor each other. Main CPU1
In addition to the frame transmission instruction indicating the "normal operation", the sub CPU 11 is provided with a sub CPU 11, a transmission instruction of data to be transmitted to the networks 1 to 2, and vice versa, and a reception instruction in each network. The result report from 12 is monitored by a timer, the report contents are checked for normality, and if there is an error, a retry is performed. If the retry is not possible, the reset latch 17a or 17b of the corresponding sub CPU
Is set to freeze the operation of the corresponding sub CPU. or,
The reset latch of the sub CPU on the opposite side is also reset, and the operation of the sub CPU on the opposite side is also frozen.

The sub CPUs 11 and 12 monitor the operation instruction from the main CPU 13 with a timer to check the normality of the contents. When an abnormality is detected, a retry is performed, and when the retry is impossible, the reset latch 17a or 17b of its own is set to freeze the operation. When the reset latches 17a and 17b are set, the transmission circuits 16a and 16b are disconnected from the network 1 or 2, so that the network is not adversely affected thereafter.

Here, in the active machine 3, after the transmission circuit 16a on the network 1 side has failed, the main CPU 13
It is assumed that the U11 and 12 issue a frame transmission instruction indicating "normal operation". The sub CPU 12 returns a normal termination report to the main CPU 13, but the sub CPU 11 reports a self-loop test abnormality. The main CPU 13 again transmits the frame indicating “in normal operation” to the sub CP.
Although instructing U11, since the sub CPU 11 cannot receive the frame by itself, it reports the abnormal end again. The main CPU 13 determines that an abnormality has occurred on the network 1 side, sets the reset latch 17a of the sub CPU 11 and the reset latch 17b of the sub CPU 12, respectively, freezes the operation of both sub CPUs, and disconnects them from the network. Anomalies are reported to the operator through the man-machine interface.

When detecting the time-out of the frame from the active machine 3, the sub CPU 11 of the standby machine 4 reports this to the main CPU 13. The main CPU 13 checks the report from the sub CPU 12, but since it is a report of normal reception, the operation of monitoring the frame from the active machine 3 is started again. In this next report, since both the sub CPUs 11 and 12 report the timer out, it is determined that an abnormality has occurred in the active machine 3, and the backup operation is started, and at the same time, the backup operation is being performed through the man-machine interface. To the effect.

In the above operation, when the standby device 4 again starts the operation of monitoring the frame from the active device 3, when the sub CPU 12 reports the normal reception and the sub CPU 11 reports the timer out, When it is judged that the sub CPU 11 is abnormal or the line on the network 1 side is abnormal, the reset latches 17 of the sub CPUs 11 and 12 in the standby unit 4 are set, and the sub CPU is frozen and its own station is disconnected from the network.

As described above, in the present embodiment, the signal cable dedicated to the active spare switching and the logic for controlling the signal are not required, and the normality of the gateway active machine is checked by the network 1 and the network 2 separately, and the spare The machine can start the backup operation.

As a media access control method of the network 2, C
When the SMA type control system is adopted, if the line usage rate becomes high, the frequency of collision between the transmission data from the active device 3 indicating the “normal operation” to the standby device 4 and the transmission data from another terminal increases. Is expected. In such a case, it is necessary to set the value of the timer of the standby device 4 in consideration of the collision, and to adopt the CSMA method with priority as the media access method.

In the present embodiment, a case has been described in which an abnormality of the active device 3 is detected by the method of transmitting a specific frame from the active device 3 to the standby device 4. In addition to this, in the token passing network, a method of detecting the validity of the backup operation start by detecting the disappearance of the token or the permanent circulation of the frame can be considered.

〔The invention's effect〕

According to the present invention, utilizing the function of the gateway itself,
Since it is possible to detect the validity of the backup operation of the gateway at a plurality of physical positions, it is possible to prevent the standby machine from erroneously shifting to the backup operation due to an abnormality in the operation monitor of the active machine, etc. It has the effect of realizing a highly reliable backup method.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing a specific configuration example of the gateway in FIG. 1, 2 ... Network, 3 ... Gateway active machine, 4 ... Gateway standby machine, 7 ... Frame, 11, 12 ... Sub CPU, 13 ... Main CPU, 15 ...
Received signal selection circuit, 17 ... Reset latch, 21 ... Relay circuit.

Claims (1)

[Claims] 1. A network system in which a plurality of networks are interconnected by gateways, wherein the networks are interconnected by a working gateway and a spare gateway, and the spare gateway monitors the operation of the working gateway by the plurality of networks, A backup method of a gateway characterized by starting a backup operation on the condition that the abnormality of the working gateway is also detected through another network when the abnormality of the working gateway is detected through.