JPH0654914B2 - Transmission line restoration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is directed to a case where a local area network connecting stations is formed using a duplexed transmission line composed of a primary transmission line and a secondary transmission line. The present invention relates to a transmission line restoration method using a so-called loopback system in which when a failure occurs in a transmission line, the input and output of a primary transmission line and a secondary transmission line are folded back to restore the fault.

[Conventional technology]

A conventional method of repairing a transmission line of this type will be described with reference to FIG.

FIG. 3 is a block diagram of a ring type local area network. S1, S2 and S3 are stations, 1 is a primary transmission line connecting the stations, and 2 is a secondary connecting the stations S1, S2 and S3. It is a transmission line.

Further, PI is an input of the primary transmission line 1 in each station S1, S2, S3, and PO is each station S1,
The output of the primary transmission line 1 in S2, S3, SI is the input of the secondary transmission line 2 in each station S1, S2, S3, SO is each station S1, S2, S3
The output of the secondary transmission line 2 in FIG.

Here, a computer or the like is connected to each station S1, S2, S3, and these computers or the like are connected to the stations S1, S2.
It is possible to communicate with each other via S2 and S3.

In this case, the data on the transmission path flows in the direction of the arrow, and completes the ring of the local area network to return to the original state.

Normally, only the primary transmission line 1 is used, and the secondary transmission line 2 is a backup transmission line in case of failure of the primary transmission line 1.

FIG. 4 shows each field in a frame flowing through a transmission line of such a ring type local area network.

As shown in FIG. 4, the frame is divided into each field, SD is a starting delimiter indicating the start of the frame, DA is the destination station address, SA is the source station address, C is a command indicating the frame format, I is user data added as needed, F
CS is a frame check sequence for detecting a frame error, ED is an ending delimiter indicating the end of the frame, and FS is a frame status indicating a response.

Here, the transmitting station, for example, the station S2, sends a frame composed of the fields SD to ED from the output PO of the primary transmission line 1 to the primary transmission line 1,
The frame is discarded when the frame has returned from the input PI of the primary transmission line 1 to the station S2 of the own station after making a round of the primary transmission line 1.

The other stations S1 and S3 constantly monitor while relaying the frame on the primary transmission line 1. If the frame is addressed to itself, the contents of the frame are fetched, and the result of whether the fetching is normally completed is displayed in the FS field. And send it.

The transmitting station S2 can determine whether the transmission is normally completed by checking the FS field.

Although the station to be transmitted needs to acquire the transmission right according to the procedure defined by the system, this procedure is not directly related to the present invention, and therefore its explanation is omitted.

Next, a method of repairing the transmission line when a failure occurs in the primary transmission line 1 will be described with reference to FIG.

FIG. 5 shows a case where the primary transmission line 1 is disconnected between the stations S1 and S2.

When a failure occurs due to disconnection of the primary transmission line 1 between the station S1 and the station S2, the station S2 detects the carrier disconnection from the input PI of the primary transmission line 1 and the output SO of the secondary transmission line 2 and the primary transmission line. 1 input PI is connected, and at the same time, using this secondary transmission line 2, an adjacent lower station S1 is connected.
On the other hand, the special symbol for instructing to connect the output PO of the primary transmission line 1 to the input SI of the secondary transmission line 2 is continuously transmitted.

Since the station S1 receives the special symbol from the input SI of the secondary transmission line 2, the primary transmission line 1
Of the secondary transmission line 2 is connected to the output PO.

In this way, the transmission line of the ring-shaped local area network is restored and communication can be performed again.

Here, the state in which the output SO of the secondary transmission line 2 is connected to the input PI of the primary transmission line 1 is the WRAPA state, and the state in which the output PO of the primary transmission line 1 is connected to the input SI of the secondary transmission line 2 is WRAPB. Status,
The WRAPA state and the WRAPB state are combined and the state other than the folded state and the state other than the folded state, that is, the state without the folded state is called the THRU state.

By the way, the above description of the transmission line restoration method is an example of the case where the transmission line is completely cut off. However, such a condition that the carrier is not cut off and the information content is only destroyed (hereinafter referred to as (Transmission failure is called information transmission failure)
There is also.

In such a case, the restoration method of the transmission line has not been established yet, and it is only possible to evaluate the location of the failure.

Therefore, a conventional method for evaluating the obstacle location will be described with reference to FIG.

In the normal mode, each station S1, S2, S3 performs normal transmission / reception while monitoring the control symbol that is always generated within a certain time of the transmission line in the normal time when the transmission line has no information transmission failure. And a beacon mode in which when a failure occurs in the transmission path, a beacon frame for notifying an abnormality of the transmission path to the station of the adjacent lower station is detected while detecting the failure of the transmission path by monitoring the control symbol, When a beacon frame is input from a station of an adjacent lower station within a fixed time in the mode, the beacon mode is changed to the normal mode.

Next, the process of repairing the above information transmission failure will be described with reference to FIG.

When a failure occurs in the primary transmission line 1 connecting the station S1 and the station S2, the stations S1, S2, S3 in the normal mode cannot detect the control symbol within a fixed time, and thus the At the same time, the normal mode is transited to the beacon mode.

Each station S1, S2 that has transitioned to beacon mode
S3 transmits the beacon frame to the station of the adjacent lower station. At this time, the station S3 transmits the station S2.
Received beacon frames from station S
1 receives the beacon frame from the station S3 and transits from the beacon mode to the normal mode, but in the station S2, the information transmission failure occurs in the primary transmission line 1 connecting the station S1 and the station S3. The beacon frame cannot be received from, and the beacon mode is maintained.

In this way, in the case of information transmission failure, the system goes down, but the failure point is station S2 in beacon mode.
Can be assumed to exist between the station and the station S1 of the adjacent upper station.

In the above description, the DA field and the FS field have no meaning in the beacon frame, and the I field does not exist.

[Problems to be solved by the invention]

As described above, the conventional transmission line repair method can repair a failure in the case of a transmission path failure that causes a carrier disconnection, but can repair a failure in the case of an information transmission failure that does not result in a carrier disconnection. Instead, they could only assume the location of the obstacle.

The present invention has been made to solve the above-mentioned problems, and is not limited to the case of a transmission line failure resulting in carrier disconnection,
The purpose is to quickly and automatically recover the system even in the event of information transmission failure that does not result in carrier interruption.

[Means for solving problems]

Therefore, the stations S1, S2, S3 of the present invention are
Is a normal mode in which normal transmission / reception is performed while monitoring control symbols, and a beacon mode in which when a failure occurs in the transmission path, a beacon frame is output to notify the station of the adjacent lower station that the failure has occurred in the transmission path. And output the secondary transmission line to the input of the primary transmission line.In the return state, output a test frame that instructs the station of the adjacent lower station to return the output of the primary transmission line to the input of the secondary transmission line. By receiving the frame from the station of the adjacent lower station within a fixed time and outputting the test mode instruction frame for instructing the station of the adjacent lower station to output the test frame again, the test mode 1 and the secondary transmission line The output of the adjacent lower station is not folded back to the input of the primary transmission line. Output a test frame to the output of the primary transmission path to the input of the secondary transmission path, and receive this test frame from the station of the adjacent lower station within a certain time, thereby again Test mode for instructing the station to output a test frame Switching between four modes, test mode 2 for outputting an instruction frame, and when a failure in the transmission line is detected in normal mode, beacon mode is switched from normal mode When the beacon frame is received from the station of the other station within a certain time in the beacon mode, the beacon mode is changed to the normal mode.
When the beacon frame is not received from the station of the other station within the fixed time in the beacon mode, the mode is switched from the beacon mode to the test mode 1, and when the test frame is received in the normal mode after detecting the failure, the output of the primary transmission line Is returned to the input of the secondary transmission line, and when a test mode instruction frame is received in normal mode after detecting a failure, transition from normal mode to test mode 2 is performed, and in test mode 2, adjacent When a test frame is received from a station of the station, the output of the primary transmission line is returned to the input of the secondary transmission line and the transition from test mode 2 to normal mode is performed without returning to the adjacent lower station within a certain time. Primary transmission line when no test frame is received from another station It is characterized in that the transition by performing the folded folding the output to the input of the secondary transmission line from the test mode 2 to the normal mode.

In addition to the above configuration, another invention is that in test mode 1, when a test frame is received from a station of an adjacent lower station within a fixed time, a test mode instruction frame is output to shift from test mode 1 to normal mode, and a test is performed. In mode 1, when a test frame is not received from a station of an adjacent lower station within a fixed time, its own station is disconnected from the local area network.

[Action]

When each station S1, S2, S3 detects a failure in the transmission path, it transits from the normal mode to the beacon mode and outputs a beacon frame.

Then, the station in the beacon mode transitions from the beacon mode to the normal mode when it receives a beacon frame from the station of the adjacent lower station within a fixed time.

Further, the station in the beacon mode transits from the beacon mode to the test mode 1 when it does not receive a beacon frame from the station of the adjacent lower station within a fixed time.

When a normal mode station receives a test frame after detecting a failure, it folds back the output of the primary transmission path to the input of the secondary transmission path, and the normal mode station after detecting the failure instructs the test mode. When the frame is received, the mode is changed to the test mode 2 without returning.

When the station in the test mode 2 receives the test frame from the adjacent lower station within a fixed time after transmitting the test frame, it transmits the test mode instruction frame to the adjacent lower station and transits to the normal mode.

When the station in test mode 2 does not receive the test frame from the station of the adjacent lower station within a fixed time after transmitting the test frame, the output of the primary transmission line is looped back to the input of the secondary transmission line and transitions to the normal mode. To do.

In another invention, when a station in test mode 1 receives a test frame from a station of an adjacent lower station within a fixed time after transmitting the test frame, it transits to the normal mode while the station in test mode 1 transmits the test frame. When no test frame is received within a certain time after that, the own station is disconnected from the local area network.

Here, the failure of the transmission path is repaired, and communication can be performed again.

〔Example〕

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

FIG. 1 (A) is a block diagram of each station in the present invention. In the figure, 1A is a switching means for switching the mode state, 1B is a switching means for controlling the switching of the switching means 1A, turning back, and releasing the turning back. The control circuit 1C is a timer that measures time.

In this embodiment, each station has four modes: normal mode, beacon mode, test mode 1 and test mode 2.

The normal mode is a state in which normal transmission / reception can be performed while monitoring control symbols.

The beacon mode is a state in which a beacon frame informing that a failure has occurred in the transmission path is output to the station of the adjacent lower station.

In the test mode 1, the output PO of the primary transmission line 1 is folded back to the input SI of the secondary transmission line 2, and the output PO of the primary transmission line 1 is folded back to the input SI of the secondary transmission line 2 for the station of the adjacent lower station. A test mode instruction frame that outputs a test frame instructing to return, and instructing the station of the adjacent lower station to output the test frame again by receiving this test frame from the station of the adjacent lower station within a fixed time Is a state of outputting.

In the test mode 2, the output PO of the primary transmission line 1 is not returned to the input SI of the secondary transmission line 2 and the above test frame is output to the station of the adjacent lower station without any return, and this test frame is output for a certain time. It is a state in which a test mode instruction frame for instructing the station of the adjacent lower station to output the test frame again is received by receiving from the station of the adjacent lower station.

Here, the mode transition will be described with reference to FIG.

In the normal mode, when a control symbol timeout occurs in which a control symbol cannot be detected within a certain time, each station transits from the normal mode to the beacon mode.

When a beacon frame is received from a station of another station within a certain time in the beacon mode, the station transits from the beacon mode to the normal mode.

In beacon mode, when a beacon frame is not received from an adjacent lower station within a certain period of time, the station transits from beacon mode to test mode 1 and enters the WRAPA state and outputs a test frame to the adjacent lower station. .

In test mode 1, when a test frame is received from a station of an adjacent lower station within a fixed time, the station outputs a test mode instruction frame to the station of the adjacent lower station, transitions to the normal mode, and enters the WRAPA state.

Further, in the test mode 1, when the test frame is not received from the station of the adjacent lower station within a certain time, the station disconnects its station from the local area network at the time-out.

When a test frame is received from a station of another station within a certain period of time in the normal mode after detecting a failure, the station folds back and remains in the normal mode.
The RAPB state is entered.

Further, when a test mode instruction frame is received from another station within a fixed time in the normal mode after detecting a failure, the station transits from the normal mode to the test mode 2 and enters the THRU state in which the loopback is canceled.

In the test mode 2, when a test frame is received from the adjacent lower station within a fixed time, the station outputs a test mode instruction frame to the station of the adjacent lower station, and the THRU state in which the loopback is canceled is entered and the station transits to the normal mode.

In the test mode 2, if a test frame is not received from the adjacent lower station within a fixed time and the time-out occurs, the station enters the WRAPB state and transits to the normal mode.

Here, the transition of the mode state is performed by the switching unit 1A under the control of the control unit 1B, and the time-out time is measured by the timer 1C.

If a new station is inserted in the local area network or if the station leaves the local area network and is bypassed, the transmission line will be temporarily disturbed and recovery will take some time. Has been taken into consideration.

FIG. 2 shows a process of repairing the information transmission failure due to the mode transition as described above, and shows an example of the case where the information transmission failure occurs between the station S1 and the station S2.

In the process of repairing this information transmission failure, the normal mode is set to M1,
In the following description, the beacon mode M2, the test mode 1 are M31, and the test mode 2 is M32.

(1) All stations are in control symbol time-out and change from normal mode (M1) to beacon mode (M2).

(2) Only the station S2 of the adjacent lower station at the location where the information transmission failure has occurred continues the beacon mode (M2), and the other stations S1 and S3 are the stations S of the adjacent upper station.
3, it becomes the normal mode (M1) after detecting the failure by receiving the beacon frame from S2.

(3) Station S2 whose beacon has timed out
Changes from the beacon mode to the test mode 1 (M31), and in the WRAPA state, transmits a test frame to the station S3 which is the adjacent lower station.

(4) The station S3, which has received the test frame from the station S2, enters the WRAPB state in the normal mode (M1) after detecting the failure, and the WRAPB
In this state, the test frame is returned to the adjacent upper station S2.

(5) The station S2 in which the transmission of the test frame in the above (3) is normally completed by receiving the reply of the test frame from the station S3 within a certain time.
Is in the WRAPA state, and is the station S of the adjacent lower station.
The test mode instruction frame is transmitted to No. 3, and the test mode 1 (M31) changes to the normal mode (M1).

(6) The station S3, which has received the test mode instruction frame from the station S2, changes from the normal mode (M1) to the test mode 2 (M32) after detecting the failure.
Then, in the THRU state, the test frame is transmitted to the adjacent lower station S1.

(7) The station S1 which has received the test frame from the station S3 is in the WRAPB state in the normal mode (M1) after detecting the failure, and the WRAPB state is set.
In this state, the test frame is sent to the adjacent station S3.
Reply to.

(8) The station S in which the transmission of the test frame in the above (6) is normally completed by receiving the reply of the test frame from the station S1 within a certain time.
3 transmits the test mode instruction frame in the THRU state to the station S1 of the adjacent lower station, and transmits the test mode 2
The normal mode (M1) is entered from (M32).

(9) The station S1 which has received the test mode instruction frame from the station S3 changes to the test mode 2
(M32), and in the THRU state, the test frame is transmitted to the adjacent lower station S2.

(10) The test frame from this station S1 does not reach the station S2 of the adjacent lower station due to the information transmission failure, and the station S1 is in test mode 2 (M32).
Does not receive the reply of the test frame from the station S1 within a certain time, it times out and WRAPB
A state is formed to enter the normal mode (M1).

In the above embodiment, stations S1 and S2
The case where an information transmission failure occurs in the transmission path between the station S1 and the station S2 has been described as an example. However, when a similar failure occurs in the receiving unit of the station S2, the station S2 transmits a test frame in the test mode 1. However, since the information is destroyed in the receiving unit of the own station, the reply of the test frame is not received from the station S2 of the adjacent lower station within a certain time and the transmission is not normally completed. Therefore, the station S2 times out in the test mode 1, and the station S2 itself leaves the local area network.

This clears the fault and restores the system.

The above embodiment has been described by taking three stations as an example for the sake of simplicity, but the principle is exactly the same even if the number of stations is increased.

In the above embodiment, each station is equipped with a switching means, a control device, and a timer to outline the concept of the present invention. However, the present invention is not limited to such a configuration, and may be processed by, for example, a program.

〔The invention's effect〕

As described above, the present invention newly adds the test mode 1 and the test mode 2 in addition to the normal mode and the beacon mode, and transitions from the normal mode to the beacon mode when the failure of the transmission path is detected in the normal mode. In beacon mode, when a beacon frame is received from a station of an adjacent lower station within a certain time, the beacon mode is changed to a normal mode, and when a beacon frame is not received from a station of an adjacent lower station within a certain time in the beacon mode. Changes from beacon mode to test mode 1 and when a test frame is received in the normal mode after detecting a failure, the output of the primary transmission path is looped back to the input of the secondary transmission path, and after detecting the failure When the test mode instruction frame is received in the normal mode, it transits to the test mode 2 and In test mode 2, when a test frame is returned from an adjacent lower station within a certain period of time, the output of the primary transmission line is returned to the input of the secondary transmission line. When the test frame is not returned within a certain time in mode 2, the output of the primary transmission line is returned to the input of the secondary transmission line and the fault of the transmission line is repaired by switching to the normal mode. In the case of information transmission failure due to a failure on the way, it becomes possible to automatically recover the system.

In another invention, when a test frame reply is received from a station of an adjacent lower station within a certain time in the test mode 1, a test mode instruction frame is output and the test mode 1 transits to the normal mode. When a test frame reply is not received from the adjacent lower station within a certain time, the own station is disconnected from the local area network. It is possible to recover the system.

[Brief description of drawings]

FIG. 1A is a block diagram of a station according to the present invention,
FIG. 1 (B) is a schematic diagram showing transition of mode states, FIG. 2 is a schematic diagram showing a process of repairing a transmission line, FIG. 3 is a configuration diagram of a conventional local area network, and FIG. 4 is transmission. 5 is a block diagram of a frame flowing through a path, FIG. 5 is a view showing a conventional method of repairing a transmission line when a failure resulting in carrier disconnection occurs, and FIG. 6 is a presumption of a failure point when an information transmission failure occurs. FIG. 7 is a diagram showing a mode transition for carrying out the above, and FIG. 7 is a diagram showing a conventional assumed system of a failure location when an information transmission failure occurs. In the figure, S1, S2, and S3 are stations, 1 is a primary transmission line, 2 is a secondary transmission line, 1A is a switching unit, B is a control unit, and 1C is a timer.

Claims (2)

[Claims] 1. A local area network connecting stations is formed by using a duplicated transmission line composed of a primary transmission line and a secondary transmission line, and a control symbol generated on the transmission line at regular intervals is monitored. When a failure occurs in the above transmission path, the station restores the failure by looping back the primary transmission path to the secondary transmission path, and each station performs normal transmission / reception while monitoring the control symbol. Normal mode, beacon mode that outputs a beacon frame that informs the station of the adjacent lower station that a failure has occurred in the transmission path when a failure occurs in the transmission path, and output of the secondary transmission path to the input of the primary transmission path The output of the primary transmission line to the station of the adjacent lower station is returned to the second Re-output the test frame to the input of the transmission path and receive this test frame from the station of the adjacent lower station within a certain time so that the test frame is output to the station of the adjacent lower station again. Test mode to instruct Test mode 1 to output instruction frame
And a test frame that instructs the station of the adjacent lower station to fold the output of the primary transmission line to the input of the secondary transmission line without wrapping the output of the secondary transmission line to the input of the primary transmission line. Test mode 2 which outputs a test mode instruction frame for instructing the station of the adjacent lower station to output the test frame again by receiving the frame from the station of the adjacent lower station within a fixed time. , And when a failure in the transmission path is detected in normal mode, transition from normal mode to beacon mode,
When a beacon frame is received from a station of another station within a certain time in beacon mode, the mode changes from beacon mode to normal mode, and when a beacon frame is not received from a station of another station within a certain time in beacon mode, the beacon mode is changed. When a test frame is received in the normal mode after detecting a failure, the output of the primary transmission path is looped back to the input of the secondary transmission path and tested in the normal mode after detecting the failure. When the mode instruction frame is received, the mode is changed from the normal mode to the test mode 2. When the test frame is received from the station of the adjacent lower station within the fixed time in the test mode 2, the output of the primary transmission line is input to the secondary transmission line. Return from test mode 2 to normal mode without wrapping In test mode 2, when a test frame is not received from a station of an adjacent lower station within a certain time in test mode 2, the output of the primary transmission line is returned to the input of the secondary transmission line and the test mode 2 is changed to the normal mode. A transmission line repair method characterized by repairing a fault in the transmission line. 2. A local area network connecting stations is formed by using a duplicated transmission line composed of a primary transmission line and a secondary transmission line, and control symbols generated on the transmission line at regular intervals are monitored. When a failure occurs in the above transmission path, the station restores the failure by looping back the primary transmission path to the secondary transmission path, and each station performs normal transmission / reception while monitoring the control symbol. Normal mode, beacon mode that outputs a beacon frame that informs the station of the adjacent lower station that a failure has occurred in the transmission path when a failure occurs in the transmission path, and output of the secondary transmission path to the input of the primary transmission path The output of the primary transmission line to the station of the adjacent lower station is returned to the second Re-output the test frame to the input of the transmission path and receive this test frame from the station of the adjacent lower station within a certain time so that the test frame is output to the station of the adjacent lower station again. Test mode to instruct Test mode 1 to output instruction frame
And a test frame that instructs the station of the adjacent lower station to fold the output of the primary transmission line to the input of the secondary transmission line without wrapping the output of the secondary transmission line to the input of the primary transmission line. Test mode 2 which outputs a test mode instruction frame for instructing the station of the adjacent lower station to output the test frame again by receiving the frame from the station of the adjacent lower station within a fixed time. , And when a failure in the transmission path is detected in normal mode, transition from normal mode to beacon mode,
When a beacon frame is received from a station of another station within a certain time in beacon mode, the mode changes from beacon mode to normal mode, and when a beacon frame is not received from a station of another station within a certain time in beacon mode, the beacon mode is changed. When the test mode 1 is entered and the test frame is received from the adjacent lower station within a certain time in the test mode 1, the test mode instruction frame is output and the test mode 1 is changed to the normal mode. When a test frame is not received from an adjacent lower station within a certain period of time, its own station is disconnected from the local area network, and when a test frame is received in normal mode after detecting a failure, the output of the primary transmission line is output. Wraps back to the input of the secondary transmission line. , When the test mode instruction frame is received in the normal mode after detecting the failure, the mode is changed to the test mode 2 from the normal mode, and when the test frame is received from the station of the adjacent lower station within the fixed time in the test mode 2, Test mode 2 without folding back the output of the primary transmission line to the input of the secondary transmission line
From the normal mode to the normal mode, and when the test frame is not received from the station of the adjacent lower station within the fixed time in the test mode 2, the output of the primary transmission line is returned to the input of the secondary transmission line and the test mode 2 returns to the normal mode. A transmission line repair method characterized by repairing a transmission line failure by transitioning to a mode.