JPH08195767A - Method for monitoring backup ring - Google Patents

Abstract

PURPOSE: To diagnose the presence of a fault in a backup ring without stopping the system operation of a station communicated via a main ring normally in a duplicate network comprising the main ring and the backup ring. CONSTITUTION: A diagnosis start station A switches an input port of a main ring 1 and an output port of a backup ring 2 and a station B based on a contact from the station A switches the output port of the main ring and an input port of the backup ring into a lap state respectively for each diagnostic period Ti. In this case, stations A-D use a new ring comprising a main ring and a backup ring for usual communication. On the other hand, the stations A, B send a diagnostic signal to diagnose the backup transmission line between the stations A, B each other and when any fault is in existence, it is outputted to restore the transmission line. Then the station A sends a diagnosis command packet to the station B and similar diagnosis is conducted between the stations B,C. The diagnosis is repeated in the arrangement order of the stations to diagnose the entire backup ring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for monitoring the presence / absence of an abnormality in a backup ring in a redundant ring network composed of a main ring and a backup ring used in a large-scale distributed control system. In the drawings, the same reference numerals indicate the same or corresponding parts.

[0002]

2. Description of the Related Art In a large-scale distributed control system, a ring-type network (for example, a network such as FDDI or token ring) is composed of a dual ring consisting of a main ring and a backup ring in terms of system reliability. Many. FIG. 9 shows a configuration example of a distributed control system using such a duplicated ring network. In the figure, 1 is a main ring, 2 is a backup ring network, and A, B, C, and D are stations on this duplex ring type network. And the same figure (a)
Is a normal network, the same figure (b) is the main ring 1
In the figure, the respective abnormal occurrence times are shown.

Normal data is transferred using the main ring 1. The backup ring 2 is used when an abnormality occurs in the main ring 1, and transfers data in the opposite direction to the main ring 1. When an abnormality occurs in the main ring 1 as shown in FIG. 9B, in order to detect the abnormality in the main ring 1 by the station closest to the location where the abnormality has occurred, A and B in this example, and disconnect the abnormal location. Inside, the transmission line on the main ring side and the transmission line on the backup ring side are joined in a folded manner, and in a so-called lap state, a new ring consisting of the main ring 1 and the backup ring 2 is re-formed, and when the main ring is abnormal, Also handles the communication between stations A to D.

Conventionally, in a system in which operation cannot be stopped, backup system diagnosis is not performed during operation, and in a system in which operation can be stopped, all communication is stopped. I was carrying out a backup system diagnosis.

[0005]

As described above, conventionally, only the method of diagnosing the backup system has been adopted, and the diagnosis is not performed during the system operation. Therefore, an abnormality in the backup system that occurs during operation in a system that continues to operate for a long time cannot be detected by a diagnosis immediately after the system is started up, and a communication failure state is caused when an unpredictable abnormality occurs in the main ring. For this reason, the effect of duplicating the network is small, and the reliability of the system is reduced. If the system operation is stopped and a backup system diagnosis is attempted in advance, communication will be lost during the diagnosis, resulting in operation loss.

Therefore, an object of the present invention is to provide a backup ring monitoring method capable of achieving the following two points. (1) The backup system is regularly diagnosed without stopping communication during operation, pre-maintenance of a failure that makes communication impossible is possible, and the reliability of the redundant ring is improved.

(2) In a highly reliable backup system, operation loss and load due to diagnosis are reduced, and conversely, in a less reliable network, diagnosis is strengthened to detect an abnormality in the backup system at an early stage.

[0008]

In order to solve the above-mentioned problems, a plurality of stations (A to D etc.) on a duplex ring type network consisting of a main ring (1 etc.) and a backup ring (2 etc.) Normally, communication is performed via the main ring, and when an abnormality occurs in the main ring, two stations sandwiching this abnormal point switch the two rings to the lap state, and
A network system that enables a communication between the plurality of stations by forming a new ring with a main ring and a backup ring excluding a transmission path directly connecting the stations.
In the monitoring method, the adjacent two stations among the plurality of stations switch the two rings to the lap state in the same manner as described above, and diagnose whether or not there is an abnormality in the backup transmission line directly connecting the two stations.

Further, in the monitoring method according to the second aspect, a predetermined one station (A, etc.) among the plurality of stations at a predetermined diagnostic cycle (Ti),
(Hereinafter referred to as the diagnosis start station), after switching between the two rings to the wrap state in the same manner as above with the adjacent station on the predetermined side, and diagnosing whether or not there is an abnormality in the backup ring transmission line directly connecting the two stations. , Ring switching is restored and a diagnostic command packet (3, etc.) is transmitted to the adjacent station, and the adjacent station then diagnoses a backup ring transmission line similar to the above with the next station adjacent to the own station. Then, the switching of the ring is restored and the diagnostic command packet is transmitted to the next station. Then, the same series of operations relating to the diagnosis of the backup ring transmission line as described above is sequentially repeated between the two adjacent stations to complete the entire backup ring. Try to diagnose.

According to the monitoring method of claim 3, the monitoring method of claim 2
In the monitoring method according to, each station, depending on the quality of the diagnostic result of the backup ring transmission line performed by its own station,
The next diagnostic time (Tt) of this transmission line is set to a predetermined time frame (minimum diagnostic time Ttmin, maximum diagnostic time Ttmax).
It is made to be variable to the shortening side or the expanding side (by the time increment / decrement Δt).

According to the monitoring method of claim 4, claim 3
In the monitoring method described in (1), the diagnosis start station sets the diagnosis cycle to a predetermined time frame (minimum) according to whether the total value of the diagnosis times of the backup ring transmission lines performed by all stations is longer than the previous total value. Diagnostic cycle Timin, maximum diagnostic cycle T
imax) to the shortening side or the extending side (time increase / decrease Δ
It should be variable (only t).

[0012]

[Operation] A station on a duplex ring type network switches a main ring and a backup ring to a wrap state with one adjacent station and forms a new ring by two rings except a transmission line directly connecting these two stations. In addition to enabling system operation, a backup ring transmission line that directly connects two stations is diagnosed, and then a diagnostic command packet is sent to the adjacent station to perform the same between the adjacent station and the next adjacent station. The local diagnosis of the backup ring is performed by causing each station on the ring network to sequentially perform the local diagnosis. Then, the diagnosis of the entire backup ring is periodically repeated.

Further, in order to reduce the number of instantaneous interruptions when executing the above-mentioned diagnosis, the diagnosis time and diagnosis cycle of the next backup system are changed according to the previous diagnosis result.

[0014]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 3 shows a schematic diagram of a network to which the present invention is applied. Network is main ring 1
And the backup ring 2, which connects stations A, B, C, and D. Each of the stations A to D consists of two ports (physical layer entities), and each port passes through the transmission path (input from the main ring 1 to output to the main ring 1 or input from backup ring 2 to backup ring). 2) and wrap (wrap input from main ring 1 to the output side to backup ring 2 or input from backup ring 2 to the output side to main ring 1) It has a mechanism.

The station which starts the diagnosis of the backup ring 2 is one station in the network, which is station A in this example.
This diagnosis starting station A has a diagnosis cycle Ti until the diagnosis is started.
Has a default value of. Further, all the stations A to D hold a diagnostic time Tt for diagnosing the state of the transmission line between the stations with the adjacent station as a default value. The diagnosis starting station A starts the diagnosis timer of the backup ring 2 after the main ring 1 operates normally, and starts the diagnosis of the backup transmission line with the adjacent station after the diagnosis period Ti.
The other stations B to D receive diagnostic command packets, which will be described later, from the adjacent stations that have completed the diagnostics and start diagnostics.

1 (a) and 1 (b) are explanatory views for diagnosing the backup transmission line between the stations A and B in the present invention.
FIG. 2B is an enlarged view of a dotted line square portion in FIG.
2A and 2B are explanatory views of the diagnosis of the backup transmission line between the stations B and C, and FIG. 2B is an enlarged view of the dotted line square portion of FIG. 2A. FIG. 4 is an explanatory diagram of the transmission of the diagnostic command packet.

Further, FIG. 7 and FIG. 8 following it show the backup ring which is started by the diagnosis starting station A after the diagnosis period Ti has timed up or the other stations B to D receive the diagnosis command packet and are activated in the present invention. In the flowchart showing the diagnosis procedure, S1 to S27 show the steps. As a procedure for diagnosing the backup ring, as shown in FIG. 1A, first, the diagnosis starting station A forcibly wraps the input side port of the main ring 1 (S2 in FIG. 7). However,
If station A detects that it is already in the wrap state in a part of the network, the diagnosis is canceled (FIG. 7, S1). When station A enters the lap state, station B of the adjacent station
Also becomes a wrap state by a specific signal instruction from the station A side, and a new ring is formed (FIG. 7, S3). After that, the stations A and B test the state of the transmission line between A and B at the default diagnostic time Tt (Fig. 7, S4). As shown in FIG. 1B, the diagnosis sends a specific signal pattern to the partner station,
The receiving station monitors the signal and makes a determination based on the frequency with which an abnormal signal pattern is detected. As a result of the diagnosis, if the quality of the transmission line is bad (S6, branch N in FIG. 8), or if transmission is not possible at all (S5, branch Y in FIG. 8), the abnormality of the backup system between the stations A and B is indicated by an LED. Is displayed or an alarm is sent (S7, S8 in FIG. 8). As a result, the backup system can be maintained during operation, and a failure due to the backup system can be avoided. When the diagnosis between the stations A and B is completed, the station A itself goes from the lap state to the through state (FIG. 8, S9). After the diagnosis of the station B is completed, when a signal change on the side of the station A is detected, the station B enters the through state and returns to the original data transfer by the main ring (FIG. 8, S10). When an abnormality occurs in another main ring during the diagnosis and the network configuration is changed, the station A stops the diagnosis and prevents the transmission line from returning the ring to the original state.

When the ring returns to the original state, as shown in FIG. 4, the station A sends the station B the diagnostic command packet 3 requesting the start of the diagnostic of the backup transmission line between the stations B and C ( (FIG. 8, S11). When the station B receives the diagnostic command packet 3, like the station A, it wraps the port on the side of the station A as shown in FIG. 2A, and as shown in FIG.
-The backup transmission path is diagnosed between C and C. The above operation is repeated in the same manner between stations C and D and between stations D and A. In this way, a local backup system diagnosis is performed between two adjacent stations without interrupting the operation during system operation.
The entire backup system is diagnosed by circulating local diagnosis.

In the present invention, the next diagnosis time Tt is changed according to the diagnosis result of the backup transmission line, and the diagnosis start station A changes the diagnosis cycle Ti according to the total diagnosis time. FIG. 5 shows the relationship between the transmission path diagnosis result and the processing of each station in the present invention, and FIG. 6 also shows the relationship between the total diagnosis time and the diagnosis cycle Ti. In addition, S2 in FIGS.
1 to S27 show steps related to this operation.

That is, as shown in FIG. 5, each station determines the next diagnostic time Tt according to the diagnostic status of the backup system as follows. The maximum value Tt when the transmission line is in poor condition
It is made longer than the current diagnosis time Tt within a range not exceeding max (S22 in FIG. 8), and conversely, shorter than the current diagnosis time Tt within a range not exceeding the minimum value Ttmin if the condition of the transmission line is good. (Fig. 8, S21). Further, when the station A, which is the diagnosis start station, receives the diagnosis command packet from the station D (S23, S24 in FIG. 7), it determines the next from the number of stations in the ring and the diagnosis time of the entire backup system between the stations A and D. The time until the start of diagnosis (= diagnosis cycle Ti) is determined as shown in FIG.

That is, if the overall diagnosis time is longer than the previous time (S25 in FIG. 7, branch Y), the arbitrarily determined minimum value Ti
The diagnostic cycle Ti is shortened within the range of min (Fig. 7, S2).
7). Conversely, if the overall diagnosis time is the same as the previous time or is shorter (S25, branch N in FIG. 7), the diagnosis cycle Ti is lengthened within the range not exceeding the maximum value Timax (S7 in FIG. 7).
6). In this way, the diagnostic time Tt and the diagnostic cycle Ti are determined according to the diagnostic status of the backup system, and regular backup diagnostics are performed.

[0022]

According to the present invention, since switching to the backup system and diagnosis of the backup ring are performed without stopping communication during system operation, there is no operational loss of stopping the system operation to diagnose the backup system. The backup system can be pre-maintained before an abnormality occurs in the main ring without any occurrence, and it is possible to prevent an unexpected situation in which communication cannot be performed for a long period of time.

Further, since the next diagnosis time and diagnosis period are dynamically determined based on the diagnosis result of the backup system, the instantaneous interruption time (number of times) is reduced in a highly reliable network in which the backup system has no particular problem. The system operation loss and load due to the diagnosis can be reduced, and conversely, in the unreliable network, the diagnosis can be strengthened and the abnormality of the backup system can be detected early.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a diagnostic operation of a backup system between stations A and B as an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a diagnostic operation of a backup system between stations B and C.

FIG. 3 is a schematic diagram of a network targeted by the present invention.

FIG. 4 is an explanatory diagram of transmission of a diagnostic command packet according to the present invention.

FIG. 5 is an explanatory diagram of processing of each station according to a diagnosis result as an embodiment of the present invention.

FIG. 6 is an explanatory diagram of a method of changing the diagnosis cycle according to the total diagnosis time.

FIG. 7 is a flowchart showing a diagnostic procedure of each station in the present invention.

8 is a flowchart following FIG. 7.

FIG. 9 is an explanatory diagram of conventional problems in the dual ring network.

[Explanation of symbols]

 1 main ring 2 backup ring 3 diagnostic command packet A to D station A diagnostic start station Ti diagnostic cycle Timin minimum diagnostic cycle Timax maximum diagnostic cycle Tt diagnostic time Ttmin minimum diagnostic time Ttmax maximum diagnostic time Δt time increment / decrement

Claims (4)

[Claims] 1. A plurality of stations on a duplicated ring type network consisting of a main ring and a backup ring always communicate through the main ring, and when the main ring is abnormal, two stations sandwiching this abnormal point are the two stations. In a network system in which a ring is switched to a wrap state, a new ring is formed by a main ring and a backup ring excluding a transmission line that directly connects these two stations, and communication between the plurality of stations is possible. A method for monitoring a backup ring, characterized in that two adjacent stations switch the two rings to the wrapping state in the same manner as described above to diagnose whether or not there is an abnormality in the backup transmission line directly connecting the two stations. 2. A plurality of stations on a dual ring network consisting of a main ring and a backup ring always communicate via the main ring, and when the main ring is abnormal, two stations sandwiching this abnormal point are the two stations. In a network system that switches the ring to a wrap state, forms a new ring with a main ring and a backup ring excluding the transmission line directly connecting these two stations, and enables communication between the plurality of stations, at a predetermined diagnostic cycle. A backup ring in which a predetermined one of the plurality of stations (hereinafter referred to as "diagnosis start station") switches the two rings to the lap state and directly connects the two stations with the adjacent station on the predetermined side as described above. After diagnosing whether there is an abnormality in the transmission path, the ring switching is restored and a diagnostic command packet is sent to the adjacent station. The backup ring transmission path is diagnosed with the next station in the same manner as described above, the ring switching is restored, and a diagnostic command packet is sent to the next station. A backup ring monitoring method characterized in that the entire backup ring is diagnosed by repeating a series of operations relating to the diagnosis of the backup ring transmission line. 3. The monitoring method according to claim 2, wherein each of the stations determines the next diagnostic time of the transmission line by a predetermined time frame according to the quality of the diagnosis result of the backup ring transmission line performed by the station. A method for monitoring a backup ring, wherein the backup ring is variable to the shortening side or the extending side. 4. The monitoring method according to claim 3, wherein the diagnosis start station performs the diagnosis according to whether the total value of the diagnosis times of the backup ring transmission lines performed by all stations is longer than the previous total value. A method for monitoring a backup ring, characterized in that the cycle is changed to a shortening side or an expanding side within a predetermined time frame.