JPH0630009A - Master back-up system for ring-shaped lan - Google Patents

Abstract

PURPOSE:To back-up a master station that has a down and is unable to transmit a synchronizing signal or frame by making another station serve as a master station to transmit the synchronizing signal or frame. CONSTITUTION:When a station ST1 serving as a master has a down, the station ST1 is unable to transmit a synchronizing signal S. Therefore the signal S is not received by the slave stations ST2-ST6 respectively. Under such conditions, a master/slave control part 21 of a controller 2 included in each slave station sets the value obtained by multiplying the number of its own station by the prescribed time value to a timer 22 as the monitor timer value. Then the timer 22 starts the time monitoring operation. Thus a slave station that received no signal S serves as a master to transmit the signal S onto a ring-shaped transmission line L even if the timer 22 is set in a time-out state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring LAN for transmitting data between stations by using one of a plurality of stations as a master and all the remaining stations as slaves. In this case, the present invention relates to a master backup method in a ring LAN.

[0002]

2. Description of the Related Art A system in which data transmission between stations is performed in synchronization with a synchronization signal or a special frame (synchronization frame) flowing through a ring transmission line is applied to one of ring type LANs (local area networks). There is something to do. Here, the synchronization signal or the synchronization frame is
It is always transmitted by a station (master station), which is a predetermined or fixedly provided master among a plurality of stations of the ring LAN.

In this type of ring LAN, although the stations can synchronously transmit data to each other, if the master station goes down, the ring LA
In N, there is no station for transmitting the synchronization signal or the synchronization frame, which causes a problem that data transmission cannot be performed.

[0004]

As described above, a station, which is predetermined as a master or is a fixed master, transmits a synchronization signal or a synchronization frame to the ring transmission line, and the other stations. A conventional ring type L that applies a method of transmitting data in synchronization with the L type
The AN has a problem that data transmission cannot be performed when the master station goes down and the synchronization signal or the synchronization frame is not transmitted.

The present invention has been made in view of the above circumstances, and an object thereof is that even if a master station goes down and cannot transmit a synchronization signal or a synchronization frame, one of the other stations becomes a master and the synchronization signal is transmitted. Or ring type L that can send backup for synchronization frame
It is to provide a master backup method in AN.

[0006]

The present invention is a ring type L
One of the plurality of stations on the AN serves as a master (master station) that constantly transmits a synchronization signal or a synchronization frame via a ring transmission path, and all remaining stations serve as slaves (slave stations). At the same time, each slave station communicates in synchronization with the synchronization signal or synchronization frame from the master station, and when this synchronization signal or synchronization frame is no longer received, the time unique to that station is monitored. Then, if the synchronization signal or the synchronization frame cannot be received within the monitoring time, it is assumed that the master station is down and that station becomes a new master and transmits the synchronization signal or the synchronization frame. It is a feature.

[0007]

In the above structure, the master station of the plurality of stations on the ring LAN transmits the synchronization signal or the synchronization frame on the ring transmission line. Each of the other stations (slave stations) performs communication in synchronization with the synchronization signal or the synchronization frame on the ring transmission line.

In such a state, if the master station goes down and transmission of the synchronization signal or the synchronization frame cannot be performed, and each slave station cannot receive the synchronization signal or the synchronization frame, the slave station Starts time monitoring. If the synchronization signal or the synchronization frame cannot be received even after the monitoring time specific to itself has elapsed, the slave station determines that the master station is down, backs up the master station, and becomes a new master. , Starts transmitting a synchronization signal or a synchronization frame.

Then, since the monitoring time is longer than that of the newly master station, the other slave stations which are still in the monitoring state for a while, the synchronization signal or the synchronization frame from the new master station is within the monitoring time. Will be received. As a result, the other stations do not detect the down of the master station and continue the slave state.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a master / slave type ring LAN to which the present invention is applied. FIG. 1A is a system configuration diagram of the ring LAN, and FIG.
FIG. 3 is an internal configuration diagram of a station.

In FIG. 1A, ST1 to ST6 are ring LAN stations, which are interconnected by a duplicated ring transmission line L. Each station ST1 to ST6 has a unique station number N.
Has 1 to N6. Here, the station number Ni (i =
1 to 6) are smaller as the value of i is smaller.

In the ring type LAN shown in FIG. 1A, one of the stations ST1 to ST6 becomes a master station and constantly transmits, for example, a synchronization signal S on the ring transmission line L, and all the remaining stations are slaves. The station is configured to perform communication in synchronization with the synchronization signal S from the master station.

As shown in FIG. 1B, the station STi (i = 1 to 6) is provided with a repeater 1 for relaying with the ring transmission line L, and a controller 2 for controlling the station STi as a whole. There is. This repeater 1 has a dual ring transmission line L when an adjacent station goes down or a failure such as disconnection of the ring transmission line L occurs.
It has a well-known connection switching mechanism (not shown) for making a loopback connection.

The controller 2 has a master / slave management unit 21 for managing master / slave switching and a timer 22 for time monitoring. When the synchronization signal S is no longer received from the ring transmission line L, the master / slave management unit 21 uses the timer 22 to monitor the time peculiar to the own station and can receive the synchronization signal S within the monitoring time. If not, the own station is switched to the master station. Next, the operation of the ring LAN shown in FIG.
Description will be made with reference to the flowchart of FIG.

Now, in the ring type LAN shown in FIG.
It is assumed that the station ST1 is a master station and the other stations ST2 to ST6 are slave stations, and the communication between the stations is performed in synchronization with the synchronization signal S from the master station ST1.

In this state, it is assumed that the master station ST1 goes down and the synchronization signal S is no longer transmitted from the station ST1.
In this case, the slave station ST2 ~
At ST6, the synchronization signal S is not received.

A master / slave management unit 2 provided in each controller 2 of the slave stations ST2 to ST6.
When the synchronization signal S is no longer received, the station No. 1 first receives its station number N as shown in the flowchart of FIG.
A value obtained by multiplying 2 to N6 by a predetermined time value (reference time value) common to each station is set in the timer 22 as a monitoring timer value, and the timer 22 is activated (step S1).

Next, the master / slave management unit 21 checks whether or not the synchronization signal S is received (step S
2) If not received, it is checked whether the timer 22 has timed out, that is, whether the synchronization signal S has not been received even after the monitoring time peculiar to the own station has elapsed (step S3). .

If the timer 22 has not timed out, the master / slave management unit 21 returns to step S2 again to determine whether or not the synchronization signal S has been received, that is, within the monitoring time peculiar to the own station. Check if S is received.

In this way, the slave station ST2
The master / slave management section 21 provided in each controller 2 of ST2 to ST6 starts time monitoring using the timer 22 when the synchronization signal S is no longer received, and monitors the time ( It is checked whether the synchronization signal S is received within the station number × reference time (step S2) or whether the synchronization signal S is not received after the monitoring time has passed (step S3).

If the synchronization signal S is not received even after the monitoring time peculiar to the own station has elapsed, the master / slave management unit 21 brings down the station which is currently the master station (here, station ST1). It is determined that the master station down is detected first, and the self station is switched to the master station and set (step S4).

In the present embodiment, the above-mentioned monitoring time is (station number) × (standard time for each station). Therefore, the slave stations ST2 to S
The monitoring time of the station ST2 having the smallest station number of T6 is the shortest. In this case, the master / slave management unit 21 of the station ST2 first detects the down of the master station (ST1), and switches itself to the master station.

Station ST2 (the controller 2 of)
Switch to the master station, as shown in FIG. 3, in place of the old master station ST1 that went down (back up the old master station ST1),
The synchronization signal S is transmitted on the ring transmission line L.

This new master station S
The synchronization signal S transmitted from T2 on the ring transmission line L is
Since the monitoring time is longer than that of the station ST2, it is received by the stations ST3 to ST6 which are still in the monitoring state. Then, the master / slave manager 21 (provided in the controller 2) of the stations ST2 to ST6 determines that the synchronization signal S is received in the above step S2, and stops the time monitoring using the timer 22. Then, the normal processing as the slave station is returned to.

As a result of the above, each station ST2 to ST
6 can communicate with each other in synchronization with the synchronization signal S. Obviously, in this state the station ST2
If the station goes down, the remaining stations ST3 to ST
The station ST3 having the smallest station number among the six, that is, the station ST3 having the shortest monitoring time becomes the master.

When the station ST1 goes down, the stations ST2 and ST6 adjacent to the station ST1 loop back the synchronization signal S (and the transmission frame) on the duplicated ring transmission line L by themselves. Therefore, the connection switching mechanism of the repeater 1 of itself is switched to connect the ring transmission line L in a loopback. The loopback connection of the duplicated ring transmission line L is well known in the related art, and thus detailed description thereof will be omitted.

In the present embodiment, when the system is started up,
The master is determined in the same manner as when the master station is down. Therefore, the master station when the system of the ring LAN shown in FIG. 1 is started up is the station S1 to ST6 which has the shortest monitoring time because of the smallest station number among the stations ST1 to ST6.
It is T1.

In the above-described embodiment, the stations have been described as performing communication in synchronization with the synchronization signal S from the master station. However, instead of the synchronization signal S, a synchronization frame can be used. is there.

[0029]

As described above in detail, according to the present invention,
One of a plurality of stations on the ring LAN serves as a master (master station) that constantly transmits a synchronization signal or a synchronization frame via a ring transmission path, and all remaining stations serve as slaves (slave stations). In addition, each slave station communicates in synchronization with the synchronization signal or synchronization frame from the master station, and when this synchronization signal or synchronization frame is no longer received, the time unique to that station is set. If you cannot monitor and receive the sync signal or sync frame within the monitoring time,
Assuming that the master station goes down, that station becomes a new master and transmits the synchronization signal or synchronization frame, so that each station communicates in synchronization with the synchronization signal or synchronization frame from the master station. Even if the master station goes down, one of the other stations can become the master and back up.

[Brief description of drawings]

FIG. 1 shows an embodiment of a master / slave type ring LAN to which the present invention is applied. FIG. 1A is a system configuration diagram of the ring LAN, and FIG. 1B is an internal configuration of a station. Fig.

FIG. 2 is a flowchart for explaining the operation of the slave station when the synchronization signal from the master station is not received in the embodiment.

FIG. 3 is a diagram showing a state in which the master station is down and the system is rebuilt in the embodiment.

[Explanation of symbols]

ST1 to ST6, STi ... Station, L ... Ring transmission line, S ... Sync signal, 1 ... Repeater, 2 ... Controller,
21 ... Master / slave management unit, 22 ... Timer.

Claims (1)

[Claims] 1. A ring LAN (local area network) in which data transmission between a plurality of stations is performed via a ring transmission path, wherein one of the plurality of stations is a master station and all the remaining stations are Becomes a slave station, the master station is configured to constantly transmit a synchronization signal or a synchronization frame via the ring transmission line, each slave station, the synchronization signal or synchronization frame from the master station and If communication is performed in synchronization and this synchronization signal or synchronization frame is no longer received, the time peculiar to the station is monitored and the synchronization signal or synchronization frame cannot be received within that monitoring time. If the master station goes down, It is configured that the station newly becomes the master station and transmits the synchronization signal or the synchronization frame, and the slave station that first detects the down of the master station backs up the master station. A master backup method in a ring-type LAN, which is a new master station.