JPH07336272A - Active standby changeover system - Google Patents

Abstract

PURPOSE:To obtain an active standby changeover system in which the effect due to the fault in the communication network having an active system and a standby system is minimized by avoiding the execution of a switch back under a specific condition. CONSTITUTION:In the communication network in which a master set 10 and plural slave sets 201-20n are connected, when a fault takes place in transmission lines 301, 302 being common parts between the master set 10 and the plural slave sets 201-20n, active standby changeover is executed quickly. A fault takes place individual parts of the master set 10 and plural slave sets 201--20n and a fault takes place in the common parts 301, 302 and active/standby system is switched and when the common part is not restored, the changeover device is not executed. Thus, the effect by the fault is minimized. Thus, the entire shut-down of the service is avoided.

Description

Detailed Description of the Invention

[0001]

The present invention is used in communication networks. The present invention is suitable for use in a star-shaped network. The present invention relates to a switching-back type switching system in which a working backup is switched when a failure occurs and a switching back is performed when a failure occurs in a backup system. The present invention relates to techniques for minimizing the effects of failures.

[0002]

2. Description of the Related Art In order to ensure communication when a failure occurs in a communication network, an active backup switching system having a redundant transmission line is widely used. This conventional example will be described with reference to FIG. FIG. 4 is an overall configuration diagram of a conventional example. The devices a and b respectively include two sets of active transmission / reception units 41 ₁ and 51 ₁
And standby transmission / reception units 41 ₂ and 51 ₂ . The devices a and b are connected by a working transmission line 30 ₁ and a standby transmission line 30 ₂ . The selection units 42 and 52 are the active transmission / reception units 41 ₁ , 51 ₁ or the standby transmission / reception unit 4
Select one from the two inputs of 1 ₂ and 51 ₂ . The failure detection unit 43 detects failure information of the active transmission path. The device-b switching request generation unit 44 generates a switching request for the selection unit 52 in response to a signal from the failure detection unit 43. The switching request detection unit 53
The switching request of the selection unit 52 from the device a is detected. The switching command generating unit 54 generates a switching command for the selecting unit 52 from the signal from the switching request detecting unit 53. The switching response generation unit 55 transfers the fact that the selection unit 52 has switched to the device a. Device b
The switching response detecting unit 45 detects the switching response signal of the selecting unit 52. The switching command generation unit 46 includes a switching response detection unit 45.
After confirming that the device b has been switched by receiving the signal from the device, a switching command for the device a is generated. The failure detection unit 47 is
Detects failure information of the backup transmission line. The switchback instruction generator 48 receives the signal from the failure detector 47 and generates a switchback instruction for the device a. The device b switchback request generation unit 49
The signal from the failure detection unit 47 is received and a switchback request for the device b is generated. The switchback request detection unit 56 detects the switchback request of the selection unit 52 from the device a. Switchback instruction generator 5
7 receives a signal from the switchback request detection unit 56 and generates a switchback command for the device b. Communication is performed between the device a and the device b. The failure status of the active transmission / reception unit 41 ₁ and the downstream active transmission path 30 ₁ of the device a is determined by the upstream active transmission path 30 1.
₁ is transmitted to the device a, and the active transmission / reception unit 51 _{1 of the} device b
The failure status of the upstream working system transmission line 30 ₁ is transmitted to the device b by the downstream working system transmission line 30 ₁ .

Next, the operation of the conventional example will be described with reference to FIGS. FIG. 5 is a diagram showing a switching sequence from the active system to the standby system in the conventional example. FIG. 6 is a diagram showing a switching sequence when a failure occurs in the standby system after switching from the active system to the standby system in the conventional example. As shown in FIG. 5, when an active system failure occurs in the device a and it is detected, the switching request protection time (T
After a), the switching request is transferred to the device b. In the device b, after receiving the switching request, the selection unit 52 switches the active transmission / reception unit 51 ₁ to the standby transmission / reception unit 51 ₂ and transfers the switching response to the device a. In the device a, after receiving the switching response, the selecting unit 52 switches the receiving unit to the standby system. When the device a detects the failure recovery of the active system, the recovery confirmation protection time (Tb) for judging the recovery from the failure recovery detection is counted. After the end of Tb, the notification of no switching is transferred to the device b. After receiving the notification of no switching, the device b changes the transmission path name (the active system is the standby system and the standby system is the active system) and transfers the non-switching notification to the device a. The device a changes the transmission path name after receiving the notification of no switching. Before the failure, the transmission line that was the active system was used as the standby system, and the transmission line that was the standby system was operated as the active system. That is, even if the failure is recovered, the transmission path is not switched back.

FIG. 5 shows a case in which a failure is detected in the standby system during non-recovery of the active system. When a failure is detected, Ta is counted, the receiving section of the device a is switched back to the active system, and a request is returned to the device b. To transfer. In the device b, after receiving the switchback request, the receiving unit switches back to the active system and transfers the non-switching notification to the device a. In this case, since the failure of the active system has not been recovered, normal communication cannot be secured, but the standby system also fails and the system is switched back to the active system for operation.

[0005]

In such a conventional method, since there is no problem even if switching back is performed because it is a 1: 1 switching method, in the case of 1: N, one device is used. This problem may spread to other slave devices. An example thereof will be described with reference to FIG. FIG. 7 is a diagram showing the operation of the conventional example in the case of 1: N. As shown in FIG. 7A, after a failure occurs between the active device a and the branching / coupling unit (shared portion), the system is switched to the standby system, the failure is relieved, and the state is switched to the switching state. As shown in b), when a failure occurs between the branching / coupling device of the standby system and the device bn (individual part), the service of the device bi is completely cut off when switching back to the active system.

The present invention has been made against such a background, and it is an object of the present invention to provide an active backup switching system capable of minimizing the influence of a failure in a communication network having an active system and a standby system. To aim.

[0007]

SUMMARY OF THE INVENTION The main feature of the present invention is to prevent complete interruption of communication between a master device and a slave device by not performing failback under a specific condition. The feature is that even if a minor failure occurs in a standby system device or transmission line while the standby system is operating, the standby system continues to operate if a major failure in the active system is not recovered. .

That is, according to the present invention, two communication systems, an active system and a standby system, and means for monitoring the presence or absence of a failure in each of the two communication systems, and the monitoring means detect the failure in the active system. In this case, the working backup switching system is provided with means for switching the communication path to the protection system and means for switching back to the working system when a failure is detected in the protection system after switching to the protection system.

Here, a feature of the present invention is that, when a fault, which is smaller than the fault in the active system, occurs in the standby system after the switching to the standby system and before the failure recovery in the active system, There is a means to prohibit the switchback.

One main device and a plurality of slave devices respectively provided with the transmitting and receiving parts of the active system and the standby system, and between the main device and the plurality of slave devices, a part of which is shared by the plurality of slave devices. In the case of including a shared portion, the monitoring means includes means for separately monitoring the shared portion and the other portion of the transmission line, and the minor failure is against the failure of the shared portion. It is desirable that the other part of the obstacle.

As a result, for example, when the active system is switched to the standby system due to a failure in the transmission line shared by a plurality of slave devices, a part related to only some slave devices is switched after switching. Even if a failure occurs, it will not return to the state before the failure again unless the shared part has been restored. Therefore, it is possible to avoid the worst situation in which all slave devices are completely disconnected.

Means for holding information related to the cause of the failure until the failure recovery of the active system is notified after switching to the standby system, and further, when the failure occurs in the standby system, the cause of the failure is set. When the failure recovery of the active system is notified, the information of the active system and the standby system is displayed without switching the active system and the standby system. It is desirable to provide a means for changing.

As a result, it is possible to determine the degree of failure by comparing them. Further, the display of the active system can be replaced and the system can be used as it is without switching back.

[0014]

According to the present invention, when a failure which is minor to the failure in the active system occurs in the standby system after the failure is restored in the active system after switching to the standby system, the switchback is prohibited.

One master device and a plurality of slave devices respectively provided with the transmitting and receiving parts of the active system and the standby system, and between the master device and the plurality of slave devices, a part of which is shared by the plurality of slave devices. In the case of including a shared portion, the shared portion of the transmission line and the other portion may be monitored separately. Here, the minor fault is a fault in the other part with respect to the fault in the common part.

As a result, for example, when the active system is switched to the standby system due to a failure in a location shared by a plurality of slave devices, a failure occurs in a part related to only some slave devices after the switching. Even if the error occurs, it will not return to the state before the failure again unless the shared part is restored. Therefore, it is possible to avoid the worst situation in which all slave devices are completely disconnected.

Information about the cause of the failure is retained until the failure recovery of the working system is notified after switching to the standby system, and when the failure occurs in the standby system, the information about the cause of the failure. And the cause of the failure that occurred in the backup system should be compared. Also, when the failure recovery of the active system is notified, it is preferable to switch the display of the active system and the standby system without switching the active and standby connections.

In this way, by judging the degree of failure by comparing, the main system of the active system and the common part have a failure, and after switching to the standby system, a minor failure of the individual system occurs in the standby system. Even in this case, however, it is possible to prevent the slave device from being completely disconnected by continuing the operation in the standby system. Further, since the switching back process is unnecessary, the device configuration can be simplified and downsized.

If a failure occurs in the individual part and the active spare switching is executed first, and then a failure occurs in the shared part, naturally, the active spare switching is promptly executed again to share the shared part. It is needless to say that it is necessary to avoid the obstacles mentioned above.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

According to the present invention, two communication systems, an active system and a standby system, means for monitoring the presence or absence of a failure in each of the two communication systems, and a method for monitoring the failure in the active system by the monitoring means are provided. This is a working backup switching system including means for switching the communication path to the protection system and means for switching back to the working system when a failure is detected in the protection system after switching to the protection system.

Here, the feature of the present invention is that, when a failure, which is smaller than the failure in the active system, occurs in the backup system before the failure recovery of the active system after switching to the standby system, There is a means to prohibit the switchback.

In the embodiment of the present invention, one master unit 10 and a plurality of slave units 20 ₁ each having a transmitting / receiving unit 11 ₁ , 11 ₂ , 21 ₁ , 21 ₂ for the active system and the standby system, respectively.
˜20 _n , the master device 10 and a plurality of slave devices 20 ₁
Transmission line 30 provided between ~20 _{n 1,} 30 _2, 3
A part of 2 ₁ and 32 ₂ is a plurality of slave devices 20 _{1 to} 20 _n.
In the case where the transmission lines 30 ₁ and 30 ₂ are included as shared parts, the failure detection unit 1 as the monitoring means.
3, 14 are common parts (30 ₁ , 30 ₂ ) of the transmission lines 30 ₁ , 30 ₂ , 32 ₁ , 32 ₂ and other parts (3
2 ₁ and 32 ₂ ) are separately distinguished and monitored, and the minor fault is a fault of the other part with respect to a fault of the common part thereof.

Further, the failure detectors 13 and 14 have means for holding information relating to the cause of the failure until the failure recovery of the active system is notified after switching to the standby system, and the standby system. When a failure occurs, the information processing apparatus includes means for comparing the information on the cause of the failure with the cause of the failure occurring on the spare system. As a result, it is possible to compare the degree of failure and determine whether the failure is serious or minor.

The fault detecting units 13 and 14 are connected to the transmission line 30 _1.
And 30 ₂ and the transmission lines 32 ₁ and 32 ₂ are separately monitored as means for monitoring the faults of the slave devices 20 _{1 to} 20 _n all at once by the fault detection unit 13 or 14. It is judged as a failure of 30 ₁ or 30 ₂ , and in other cases, the transmission line 32 ₁ or 32 ₂
It is monitored so that it is judged as the failure of. The failure detection units 13 and 14 retain this determination result as information related to the cause of the failure, and when a failure occurs in the spare system, information related to the cause of the failure and the cause of the failure that occurred in the spare system. Determine whether the failure is serious or minor by comparing and.

Further, when the failure recovery of the active system is notified, means for exchanging the display of the active system and the standby system without switching the active and standby connections are respectively provided in the transmitting / receiving sections 11 ₁ , 11 ₂ , 21 ₁ , 21. Be prepared for ₂ .

The main device 10 has a switching request generating section 18 as means for sending a switching request to the slave devices 20 _{1 to} 20 _n.
And a switching response detecting unit 15 as means for receiving switching responses from the slave devices 20 _{1 to} 20 _{n in} response to the switching request and executing switching.

Further, a timer 16 is provided as means for executing switching when a switching response cannot be received within a predetermined time.

In addition, the switching request generator 18 receives the signals from the failure detectors 13 and 14 and outputs the slave devices 20 _{1 to} 20.
Generates a switch request signal addressed to _n . However, the failure detection unit 1
When a failure detection stop instruction is issued from 3 to the failure detection unit 14, the generation of the switching request signal is stopped. The switching command generation unit 17 generates a switching command for the selection unit 12 in response to a signal from the switching response detection unit 15 or a time-out of the timer 16.

The switching control unit 23 of each of the slave devices 20 _{1 to} 20 _n is composed of a switching response generation unit 65, a switching command generation unit 67, and a switching request detection unit 68, and the active transmission / reception unit 21 ₁ or the standby transmission / reception unit 21 ₂ Selector 22 using the control signal from
To control. The branching / combining unit 31 is a transmission line 30 ₁ or 3
The signal from 0 ₂ is directly transmitted to the n transmission lines 32 ₁ or 3
2 ₂ or the signals from n transmission lines 32 ₁ or 32 ₂ are directly combined to form one transmission line 30 ₁
Or output to 30 ₂ .

Next, the operation of the embodiment of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing the operation of the embodiment of the present invention. The failure detection unit 13 of the main device 10 detects a failure in the active system shared unit, and the timer 16 starts (S1). Switching request is forwarded from the switching request generation unit 18 with respect to slave device 20 ₁ to 20 _n at the same time (S2). In response to this, the selection units 22 of the slave devices 20 _{1 to} 20 _n respectively select and switch the active transmission / reception unit 21 ₁ to the standby transmission / reception unit 21 ₂ (S3). A switching response signal indicating the switching is generated by the switching response generation unit 65 and returned to the main device 10 (S
4). When the switching response signals from the slave devices 20 _{1 to} 20 _n are received (S5), the timer 16 is stopped (S7), and the active transmission / reception unit 11 ₁ is switched to the standby transmission / reception unit 11 ₂ (S6).

After that, if a failure occurs in the spare system individual unit, the switchback operation is not performed (S8). After that, when the main unit 10 detects the recovery of the active system (S9), the non-switching notification is transferred to the slave units 20 _{1 to} 20 _n (S1).
0). Change the slave 20 ₁ to 20 _n in the transmission path name (standby system and the working system) (S11), and transfers the switching without notification to the main unit 10 (S12). The transmission path name is changed in the main device 10 (S13). At this time, since the detection of a failure on the working individual unit of the main device 10 (formerly transmission path name change standby system individual unit) (S14), again the slave device 20 ₁ to the switch request
20 _n (S15), the selection units 22 of the slave devices 20 _{1 to} 20 _n are selected as a standby system (S16), and the switching response is transferred to the main device 10 (S17). When the switching response signals of the slave devices 20 _{1 to} 20 _n are received (S18), the timer 16 is stopped (S20), and at the same time, the selection unit 12 of the master device 10 is switched to the standby system (S19).

After that, when the active system is recovered (S21),
Notification of no switching is sent to the slave devices 20 _{1 to} 20 _n (S
22), the transmission path name is changed (S23). Slave device 20
Notification of no switching is sent from _{1 to} 20 _n to the main device 10 (S2
4), the main device 10 also changes the transmission path name (S25).

Next, other operations will be described with reference to FIG. FIG. 3 is a diagram showing another operation in the embodiment of the present invention. Here, in response to the switching request from the main device 10, the switching responses from the slave devices 20 _{1 to} 20 _n do not all arrive, and the operation is performed after the timer 16 times out. Failure detection unit 13 of main device 10
Then, the failure of the active system common part is detected, and the timer 16 is started (S31). At the same time, the switching request is transferred from the switching request generation unit 18 to the slave devices 20 _{1 to} 20 _n (S3).
2). In response to this, the selection units 22 of the slave devices 20 _{1 to} 20 _n
Selects and switches the standby transmission / reception unit 21 ₂ from the active transmission / reception unit 21 ₁ (S33). A switching response signal indicating the switching is generated by the switching response generation unit 65 and returned to the main device 10 (S34). Slave devices 20 _{1 to} 20 _n
Since all the switching response signals from (1) to (3) have not been received, the timer 16 times up as it is and ends the time measurement (S37).
The main device 10 uses the active transmission / reception unit 11 ₁ as the standby transmission / reception unit 1 1.
Switch to 1 ₂ (S36).

After that, if a failure occurs in the spare system individual unit, the switchback operation is not performed (S38). After that, when the main system 10 detects the recovery of the active system (S39),
The non-switching notification is transferred to the slave devices 20 _{1 to} 20 _n (S4).
0). The slave devices 20 _{1 to} 20 _{n change} the transmission path names (standby system and active system) (S41), and transfer the non-switching notification to the main device 10 (S42). The transmission path name is changed in the main device 10 (S43). At this time, since the detection of a failure on the working individual unit of the main device 10 (formerly transmission path name change standby system individual unit) (S44), again the slave device 20 ₁ to the switch request
Transferred to 20 _n (S45), the slave device 20 ₁ to 20 _n of the selector 22 selects the standby system (S46), and transfers the switching response to the main device 10 (S47). When the switching response signals of the slave devices 20 _{1 to} 20 _n are received (S48), the timer 16 is stopped (S50), and at the same time, the selection unit 12 of the master device 10 is switched to the standby system (S49).

After that, when the active system is restored (S51),
Notification of no switching is sent to the slave devices 20 _{1 to} 20 _n (S
52) and change the transmission path name (S53). Slave device 20
Notification of no switching is sent from _{1 to} 20 _n to the main device 10 (S5
4), the main device 10 also changes the transmission path name (S55).

In this way, in a communication network in which one master device 10 and a plurality of slave devices 20 _{1 to} 20 _n are connected, the master device 10 and a plurality of slave devices 20 _{1 to} 20 _n share a common part. When a failure occurs, the active standby switching is promptly executed, and the main device 10 and the individual slave devices 20 ₁ , 20 ₂ ,
In the case where a failure occurs in the individual parts of 20 ₃ , ..., 20 _n, and after the failure occurs in the common part and the active spare switching is performed, and the common part has not been restored yet, The impact of a failure can be minimized without performing a switch. As a result, it is possible to avoid the interruption of the service.

In the embodiment of the present invention, the failure detecting unit 13 is used as the active system and the failure detecting unit 14 is used as the standby system. However, it is needless to say that its position is reversed after the transmission line name is changed. In FIG. 1, the direction of the "stop" arrow from the failure detection unit 13 to the failure detection unit 14 is reversed as the position reverses. Similarly, in FIG. 1, the failure detection unit 1
The arrow "stop" from 4 to the switching request generator 18 is
As the position is reversed, the failure detection unit 13 moves to the switching request generation unit 18. Further, although the start input of the timer 16 is illustrated as being output from the failure detection unit 13,
This is also output from the failure detection unit 14 according to the reversal of the position.

[0039]

As described above, according to the present invention,
It is possible to realize an active backup switching method capable of minimizing the influence of a failure in a communication network having an active system and a standby system. Further, since the switching back processing unit is not required, the device configuration can be simplified and downsized.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the operation of the embodiment of the present invention.

FIG. 3 is a diagram showing another operation according to the embodiment of the present invention.

FIG. 4 is an overall configuration diagram of a conventional example.

FIG. 5 is a diagram showing a switching sequence from an active system to a standby system in a conventional example.

FIG. 6 is a diagram showing a switching sequence when a failure occurs in the standby system after switching from the active system to the standby system in the conventional example.

FIG. 7 is a diagram showing an operation of a conventional example in the case of 1: N.

[Explanation of symbols]

10 main device 11 ₁ , 21 ₁ , 41 ₁ , 51 ₁ active transmission / reception unit 11 ₂ , 21 ₂ , 41 ₂ , 51 ₂ standby transmission / reception unit 12, 22, 42, 52 selection unit 13, 14, 43, 47, 67 Failure Detection Section 15 Switching Response Detection Section 16 Timer 17 Switching Command Generation Section 18 Switching Request Generation Section 20 _{1 to} 20 _n Slave Device 23 Switching Control Section 30 ₁ , 30 ₂ , 32 ₁ , 32 ₂ Transmission Line 31 Coupling / Distribution Section 44 device b switching request generation unit 45 device b switching response detection unit 46 switching command generation unit 48, 57 switchback command generation unit 49 device b switching back request generation unit 53, 68 switching request detection unit 54, 67 switching command generation unit 55 , 65 Switching response generation unit 56 Switchback request detection unit

Claims (3)

[Claims] 1. A two communication system, an active system and a standby system, means for monitoring the presence or absence of a failure in each of the two communication systems, and a communication path when a failure in the active system is detected by the monitoring means. In the active standby switching system, and means for switching back to the active system when a failure is detected in the standby system after switching to the standby system. After the recovery of the failure of the active system, the active backup switching system is provided with means for prohibiting the failback when a minor failure occurs in the backup system before the failure of the active system. 2. A main device and a plurality of slave devices respectively provided with a transmission / reception unit of an active system and a standby system, and a part of the main device and the slave devices provided between the main device and the slave devices. In the case of including a shared portion that is shared, the means for monitoring includes means for separately monitoring the shared portion and the other portion of the transmission path, and the minor failure is a failure of the shared portion. On the other hand, the active standby switching system according to claim 1, which is a fault in a portion other than that. 3. A means for holding information relating to the cause of the failure until the failure recovery of the active system is notified after switching to the backup system, and further, when the failure occurs in the backup system, Displaying the active system and the standby system without switching the active and standby connections when the failure recovery of the active system is notified, including means for comparing the information related to the cause and the cause of the failure that has occurred in the standby system. 3. The active standby switching system according to claim 2, further comprising means for replacing