JP2001094584A - Loop transmission device capable of specifying failure position - Google Patents

Abstract

PROBLEM TO BE SOLVED: To securely specify a failure position if a fixed failure or intermittent failure occurs on a transmission line. SOLUTION: In a looped transmission system, each child node always monitor whether a frame received from the upstream side of the transmission line is normal or abnormal, saves failure information in its internal memory if a failure is detected, and integrates how many times the failures occur in its internal memory. A parent node sends a polling frame to the transmission line at constant intervals and collects failure information from all the nodes in the loop if the ratio of the return of the frame to the parent node after one round of the loop decreases to a level below predetermined. An intermittent failure on the transmission line is detected from a decrease in the rate at which the polling frame sent by the parent node does not make one round of the loop to a level below predetermined. For specifying the failure position, the most upstream node which is detecting the failure is found from the collected failure information of all the child nodes and it is judged that the node is right behind the failure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission system having a loop-type transmission line, which is capable of detecting a fault occurrence location even when a transmission fault affects a plurality of transmission devices located downstream of the fault occurrence location. It relates to an identifiable transmission device.

[0002]

2. Description of the Related Art In a network system in which a plurality of nodes distributed over a long distance are connected to a common transmission line, if a failure occurs on the transmission line, an appropriate failure is required to continue stable communication. Recovery processing is required. Generally, in a double loop transmission system in which a plurality of (five in this figure) transmission devices are connected to transmission lines in opposite directions as shown in FIG. 2, stable communication is performed when a failure occurs on the transmission line. In order to continue, as shown in FIG. 2A, two nodes (ST2 and ST3) adjacent to the fault take a loopback configuration to isolate the fault location. This loopback configuration is continued until the fault is removed from the transmission path. When recovery from the fault is detected, the nodes located at both ends of the fault cancel the loopback configuration and form a loop configuration again. The trigger for loopback by each node is the detection of an abnormality (carrier cut, reception of an abnormal transmission frame, etc.) in the upstream of the transmission line. Perform when detected. Note that a failure point can be determined by a node having a loopback configuration notifying all other nodes of the fact.

[0003] Transmission path failures are classified into those that occur fixedly due to cable disconnection or short circuit, and those that occur intermittently due to noise or poor contact of the connector.

[0004] If the fault that has occurred has the former property, transmission performed in a section including the fault always becomes abnormal, and transmission performed in other sections always becomes normal. Therefore, it is easy to detect the fault. It is possible to easily determine the recovery after removing the failure factor. However, when the fault has the latter property, the transmission performed in the section including the fault has two results, normal and abnormal, so that it is difficult to detect the fault and determine the recovery. As a result, a failure may not be detected in spite of the occurrence of a failure in the transmission path, or a failure may be erroneously determined to have been recovered even though the failure has not been completely removed. To solve such a problem, Japanese Patent Application Laid-Open No. 5-130119
No., normal and abnormal transmission paths are counted and a fault is detected if the error rate exceeds a predetermined value.If the error rate falls below a predetermined value after fault detection, fault recovery is performed. A method is disclosed in which a determination is made to avoid erroneous determination of occurrence and recovery of a failure. However, this method has a problem in that it is not possible to accurately specify a failure point in the following cases.

FIG. 2B shows an example in which an intermittent fault occurs between ST1 and ST2 on the A-system transmission line. Here, ST0 is a central controller for monitoring and controlling the transmission path, ST1, ST2, ST
3. ST4 is defined as a subordinate device, and the central control device ST0 is called a parent node, and the subordinate devices ST1, ST2, ST3, and ST4 are called child nodes. ST3 addressed to ST2 transmitted on the transmission path from the parent node, ST3
The transmission frame addressed to ST4 is
Passed between ST2 and affected by obstacles. If the probability of the transmission frame being destroyed by the intermittent failure exceeds the probability of abnormal / normal monitored by each transmission device, ST2, S
In some cases, ST4 detects an abnormality in the upstream of the transmission line before T3. As a result, ST4 erroneously recognizes that a failure has occurred immediately upstream of the A-system transmission line, takes a loopback configuration, and notifies another node that a failure has occurred upstream of ST4 on the A-system transmission line. As a result, although this transmission line has a noise source between ST1 and ST2, it is erroneously determined that a failure has occurred upstream of the A-system transmission line ST4, as shown in FIG. 2 (c). ST3
And ST4 performs a loopback configuration.

As described above, in a loop transmission path in which all nodes located downstream of a failure are affected by the failure, if an intermittent failure occurs on the transmission path due to noise or the like, a plurality of nodes may fail. It is difficult to detect the failure and specify the location of the failure. In addition, intermittent failures on the transmission path have a negative effect on transmission efficiency if left unattended. Particularly in control LANs that require real-time performance, effective failure points are required to ensure the required performance of the system. Is required.

[0007]

As described above, in a transmission system having a property that a fault on a transmission line propagates downstream, means for surely specifying a fault location even when an intermittent fault occurs on the transmission line. It is to realize.

[0008]

In a loop transmission system in which one parent node and a plurality of child nodes are connected on a transmission line, each child node constantly monitors an abnormal / normal state of a frame received from the upstream of the transmission line. If a failure is detected, the failure information is saved in the internal memory, and the number of times the failure has occurred is integrated in the internal memory. In addition, the parent node transmits a polling frame on the transmission line at a fixed cycle, and when the rate at which the frame loops around the loop and returns to the parent node again becomes smaller than a predetermined value, a failure occurs from all the child nodes on the loop. Gather information. Intermittent faults on the transmission path are detected when the rate at which the parent node does not make a round of the polling frame transmitted over the transmission path falls below a predetermined value, and the fault location is detected from the collected fault information of all child nodes. This is done by determining the most upstream node that has failed and determining that the node is the node immediately below the failure.

[0009]

FIG. 1 shows an SDLC applied to the present invention.
1 shows a schematic diagram of a double loop transmission system using a GA polling method. A-system transmission line 3 whose transmission directions are opposite to each other
A plurality of transmission devices are connected to the 0 and B transmission lines 40 to form a loop network. The transmission device 11 is connected to the information control device 21 via the device interface 54, and is a functional unit that exchanges data between the information control devices. Frames received from A-system transmission line 30 are A-system transceivers
Taken into the transmission device 11 from 58A, A system reception control unit 57A
, The destination of the frame is determined, and if it is addressed to the own station, frame reception processing is performed. The acquired information is stored in the internal memory 52 once.
Is sent to the information control device 21 via the device interface 54. If the received frame is not addressed to the own station, the frame is sent to the A-system transmission control unit 56A and relayed downstream of the A-system transmission path. The transmission data from the information control device 21 to the A-system transmission line is transferred to the internal memory 52 via the device interface 54.
The data is processed into a transmission frame by the A-system transmission control unit 561 and transmitted downstream of the A-system transmission path via the A-system transceiver 58A. The configuration control unit 59 has a function for controlling the transmission path and transmission mode of the loop transmission line, and an abnormality detection unit 591 for detecting an abnormality of a frame received from upstream and a notification of a transmission mode to be adopted by each node. Mode notification section 592
And a mode setting unit 593 that determines the transmission mode of the own transmission apparatus according to the notified transmission mode instruction. When the abnormality of the transmission frame is detected, the failure information collection unit 53 records the content and the number of occurrences of the failure in the failure information area 521 of the internal memory 52. The above processing is realized by the CPU 51 connected to the internal bus 55 and software processing.

FIG. 3 shows an example of a transmission frame format in the dual loop transmission device shown in FIG. In the SDLC GA polling method applied to the present invention, one transmission device on a transmission path is defined as a parent node, and the others are defined as child nodes, and when no failure occurs on the transmission path, the parent node performs a relay operation. No primary station mode, and a secondary station mode in which each child node performs a relay operation. The mode setting unit in FIG. 1 determines which mode of the primary station or the secondary station is set.
593. Transmission frame 60 from parent node
Indicates a polling frame 601, an information frame 602, and "011111
The polling frame 601 can be further divided into a GA pattern 603 having a bit array of "11", a boundary flag 604 having a bit array of "01111110", a destination address 605, a source address 606, control information 607, and a frame validity. Are divided into a frame check sequence 608 indicating Further, the information frame 602 is further divided into a boundary flag 604, a destination address 605, a source address 606, control information 607, an information message 609 exchanged between nodes, and a frame check sequence 608.

The polling frame can be transmitted only from the node in the primary station mode, and the master transmission device instruction bit 61 in the control information 607 indicating the transmission path state.
1. The following three types are classified according to the combination of the loop fault indication bits 612.

(1) M = 1, E = 0 (POL0) The parent node indicates that there is no transmission line failure in both loops.

(2) M = 1, E = 1 (POL1) An instruction from the parent node that one of the transmission lines in both loops has a fault.

(3) M = 0 (POL2) A management frame transmitted from the child node notifies that there is a transmission path failure occurring upstream of the child node. The parent node determines that the node transmitting this frame for a certain period of time is adjacent to the failure location.

When the parent node holds the transmission data,
As shown in FIG. 3, the polling frame 601 and the GA pattern 6
An information frame 602 is added during 03 and transmitted to the transmission path. When the child node holds the transmission data, the information frame 602 is triggered by the detection of the GA pattern from the upstream transmission path.
Data transmission is performed by a method of adding transmission data of the own node between the data and the GA pattern 603. The detailed data transmission procedure performed by each node will be described with reference to FIG.

FIG. 4 is a time chart of data transmission in the transmission apparatus shown in FIG. SDLC in the present invention
In the GA polling method, when no failure occurs on the transmission path, the parent node is in the primary station mode, each child node is in the secondary station mode, and the parent node has a certain transmission cycle time 70 minutes.
A frame is transmitted every time. When the parent node holds the transmission data, the information frame 6 is added to the polling frame 601.
The frame with 02 and GA pattern 603 added is transmitted in the transmission direction on the loop. When the parent node does not hold the transmission data, a frame in which only the GA pattern 603 is added to the polling frame 601 is transmitted to the transmission path. A transmission frame 60 in FIG. 4 shows a frame format when the parent node holds transmission data. After transmitting the GA pattern 603, the parent node transmits a continuous “1” as the idle signal 613 on the loop until the next frame is transmitted. The child node 1 that has received the transmission frame 60 transmitted by the parent node refers to the destination address in the information frame 602, and if the destination address is its own address or a broadcast address, performs the data reception process. After that, the received frame is repeated to the downstream node. When the child node 1 holds the data to be transmitted, the GA pattern 603 is changed from 1 to 0 by changing the last bit of the GA pattern 603 which is the end flag of the transmission frame 60 received from the parent node. Boundary flag 6
The number is changed to 14, and the frame to which the information frame 615 and the GA pattern 616 are added is transmitted to the downstream node. Thereafter, similarly, if there is data to be transmitted, the downstream node changes the GA pattern to a boundary flag, adds the transmission data and the GA pattern, and transmits the frame downstream of the transmission path. After transmitting the GA pattern in any node, the transmission control unit 56 in FIG. 1 continues to transmit the idle signal 613 on the transmission path. In the double loop transmission device of the present invention, A
The frame transmission is performed for both the loops of the system and the system B.

Next, a failure detection method according to the present invention will be described.

FIG. 5 shows an example where the transmission path is normal in the double loop transmission system.

The parent node, child node 1, child node 2, child node 3, and child node 4 have transmission directions opposite to each other.
The two nodes are connected to two transmission lines, the system and the system B. In both systems, the parent node is in the only primary station mode on the loop, and each child node is in the secondary station mode. Since the parent node has not detected any abnormality in the transmission lines of both systems, transmission frames containing POL0 and GA patterns indicating that no failure has occurred on the transmission lines for both the A and B transmission lines Send (80, 81). The transmission frame 80 transmitted from the parent node to the A-system transmission path circulates in the order of child node 1, child node 2, child node 3, and child node 4, and returns to the parent node again. The transmission frame 81 transmitted from the parent node to the B-system transmission path circulates in the order of the child node 4, the child node 3, the child node 2, and the child node 1, and returns to the parent node again. Since the transmission frame transmitted from the parent node is transmitted at a constant and sufficient time interval in both the A and B systems, when the transmission frame 80 transmitted by the parent node to the A system returns to the parent node again, It is assumed that the node continues to transmit an idle signal to the A system.
The same applies to the B-system transmission path.
It is assumed that the parent node continues to transmit an idle signal to the B-system transmission line when the device goes around the B-system transmission line and returns to the parent node again. This means that transmission frame collision does not occur on the transmission path. The parent node counts the number of transmission frames transmitted and the number of transmission frames that return to the parent node after making a round of the loop transmission path for both the A-system and B-system transmission paths, and constantly monitors the ratio. ing. Each child node constantly monitors the transmission of frames from the upstream at a fixed time interval to both the A-system and B-system transmission lines. The parent node detects that a failure has occurred on the transmission path when the ratio falls below a predetermined value, and the child node does not receive the transmission frame received from the upstream continuously the predetermined number of times. A transmission path failure upstream is detected.

The operation of detecting a failure on a transmission line will be described in detail below.

FIG. 6 is an explanatory diagram of the operation when a fixed failure 90 occurs between the child node 1 and the child node 2 on the A-system transmission line 30. FIG. 6A shows the state of the transmission line immediately after the occurrence of a failure. In the A-system transmission line 30, the child nodes 2, 3, and 4 located downstream of the failure are
By not receiving POL080, which is supposed to be received at a constant period from the predetermined number of times, continuously, it detects that a failure has occurred in any of the upstream. The parent node is system A transmission line 3.
In 0, the failure of any one of the A-system transmission paths 30 is detected by not receiving the round frame 80 of POL0 continuously a predetermined number of times. FIG. 6B is an explanatory diagram of an operation until a fixed fault location is specified. The parent node transmits POL1 (85, 86) to both loops in order to notify all nodes that a failure has occurred on the transmission path.
Further, the child node 1, the child node 2, and the child node 4, which have detected the transmission line failure 90 upstream of the A-system transmission line 30, change the transmission mode for the A-system transmission line from the secondary station mode to the primary station mode, Transmit POL2 (82, 83, 84) without waiting for a polling frame from the parent node. This POL2 is for monitoring whether the transmission path of the downstream station can transmit data. In the child nodes 3 and 4, the A transmission line 30
To receive POL2 transmitted by child node 2 and child node 3 from the upstream of the node, determine that the own node is not an adjacent station due to the failure
Change the A-system transmission mode from primary station mode to secondary station mode. The parent node that has detected the occurrence of a failure on the A-system transmission path 30 is the child node 2 because the node that continues to transmit POL2 82 from the A-system transmission path 30 is located upstream of the child node 2. And the fault location is specified. POL2
It is apparent from the source address of POL2 that the sending node is the child node 2. With the above procedure, the location of the failure when a fixed failure occurs on the transmission path is specified.

Next, a description will be given of a failure detection operation when an intermittent failure occurs on a transmission line.

FIG. 7 is a diagram showing the A between the child node 1 and the child node 2.
An operation when an intermittent failure 91 occurs on the system transmission line 30 will be described. FIG. 7A shows the transmission line immediately after the occurrence of the intermittent failure. In the A-system transmission line 30, the child nodes 2, 3, and 4 located downstream from the failure have the A-system transmission line 3.
From 0, it starts to detect abnormalities in the transmission frame 80 that should be transmitted at a constant period. However, child node 2, child node 3,
Since the child node 4 does not continuously detect the frame abnormality from the upstream of the transmission line, the child node 4 counts the number of occurrences of the abnormality of the transmission frame, and records the number in the failure information area 521 in the internal memory 52 in FIG. However, the transmission mode of the A-system transmission line is not changed to the primary station mode, and POL2 is not transmitted to the downstream station. FIG. 7B is an explanatory diagram of the operation until the intermittent fault location is specified. The parent node constantly monitors the rate at which the transmission frame 80 transmitted to the A-system transmission path 30 makes a round, and if the rate falls below a preset value, changes POL0 to POL1 and causes a transmission path failure to each node. Inform. At the same time, a transmission frame 87 including data indicating a failure information collection request is broadcast-transmitted to all the child nodes to the A-system transmission path 30. All the child nodes that have received the frame convert the failure information held in the internal memory into transmission data, add the transmission data to the transmission frame 87, and transmit it to the downstream station. The parent node that has collected the failure information of all the child nodes determines that a failure has occurred between the node that detected the failure and the node that does not detect the failure, and specifies the location of the failure. In the example of FIG.
Since the failure 91 is not detected by the child node 1 but detected by the child node 2, the child node 3, and the child node 4, it is concluded that the upstream of the child node 2 in the A-system transmission line is the failure occurrence point. If the failure information collection request 87 does not normally go around the transmission path, retry processing is performed.

FIGS. 8 and 9 show flowcharts of the above-described operation for specifying a fault location. FIG.
FIG. 9 shows a failure point identification process in the parent node, and FIG. 9 shows a failure point identification process in the child node.

[0025]

According to the present invention, as a transmission method of a transmission line,
In a double loop transmission device employing the SDLC GA polling method, it is possible to specify a failure occurrence location. In particular, it is possible to specify a failure location even for an intermittent failure in which it is difficult to identify the location where the failure has occurred.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmission system according to the present invention.

FIG. 2 is an explanatory diagram of a failure point detection operation of the conventional double loop transmission device.

FIG. 3 is a diagram showing a format example of transmission information according to the present invention.

FIG. 4 is a diagram showing an example of a data transmission time chart of the communication control method of the present invention.

FIG. 5 is a diagram showing a normal operation example of both transmission lines.

FIG. 6 is a diagram showing a failure detection operation when a fixed failure occurs in an A-system transmission line.

FIG. 7 is a diagram showing a failure detection operation when an intermittent failure occurs in an A-system transmission line.

FIG. 8 is a diagram showing an example of a failure point detection operation flow of a parent node according to the present invention.

FIG. 9 is a diagram showing an example of a failure node detection operation flow of a child node according to the present invention.

[Explanation of symbols]

11, 12, 13, 14, 15 ... Transmission equipment, 21, 22, 23, 24, 25 ...
Information control device, 30 ... A system transmission line, 40 ... B system transmission line, 51 ... CP
U, 52: Internal memory, 521: Fault information area, 53: Fault information collection unit, 54: Device interface, 55: Internal bus, 56
... Transmission control unit, 57 ... Reception control unit, 58 ... Transceiver, 59 ... Configuration control unit, 591 ... Abnormality detection unit, 592 ... Mode notification unit, 593
... Mode setting unit, 60 ... Transmission frame, 601 ... Polling frame, 602 ... Information frame, 603, 616 ... GA pattern, 604 ... Boundary flag, 605 ... Destination address, 606 ... Source address, 607 ... Control information, 608 ... frame check sequence, 609 ... information message, 610 ... polling frame identification bit, 611 ... master transmission instruction bit, 612 ...
Loop failure indication bit, 613: idle signal, 614: flag, 615: information frame from child node 1, 70: transmission cycle time, 80, 81, 83, 84, 85, 86, 87: transmission frame, 90: fixed Disability, 91 ... intermittent failure.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiro Nakano 5-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Omika Works, Hitachi, Ltd. (72) Inventor Takashi Inoue 5-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Omika Works (72) Inventor Takushi Hamada 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Omika Works (72) Inventor Mamoru Ichimura Hitachi, Ibaraki 5-2-1, Omikacho Hitachi Process Computer Engineering Co., Ltd. (72) Inventor Kazuo Kono 5-2-1 Omikamachi, Hitachi City, Ibaraki Prefecture Hitachi Process Computer Engineering Co., Ltd. F-term (reference) 5K031 AA08 AA14 BA03 CA01 CB06 DA06 DB04 DB10 EA01 EA04 EA07 EC02 5K035 AA04 AA07 BB03 CC08 DD01 EE01 FF01 FF02 JJ02 KK02 MM03 5K042 AA01 BA01 CA05 CA13 DA27 DA33 EA01 FA15 GA01 JA01 LA15

Claims (5)

[Claims] 1. A loop-type transmission line is constituted by a central control device for monitoring and controlling a transmission line by a plurality of distributed transmission devices and a slave device other than the central control device. Data is transmitted to each subordinate device by transmitting a transmission frame on the loop transmission path, and each subordinate device adds data to be transmitted to the transmission frame received from upstream to transmit data to another subordinate device or the central control device. When a fixed or intermittent transmission failure occurs in a transmission loop-type transmission system, even if the failure affects multiple transmission devices downstream of the transmission path, a function to determine the location of the failure is provided. A transmission device characterized by having. 2. The method according to claim 1, wherein when a plurality of transmission devices are affected by the transmission failure, the failure location is determined by determining the first upstream location on the loop transmission path where the failure is detected as the failure location. Transmission device. 3. The transmission control system according to claim 1, wherein the fixed and intermittent transmission failure is detected by all the transmission devices constantly monitoring the abnormality / normality of the transmission frame transmitted by the central control device at a fixed period, and the abnormality is determined in advance. If a fixed number of transmission failures occur consecutively, it is determined that a fixed transmission failure has occurred, and the central controller constantly monitors the rate at which transmission frames transmitted at a fixed period return to the central controller again, and the rate is determined in advance. A transmission device that determines that an intermittent transmission failure has occurred when the value falls below the threshold value. 4. The apparatus according to claim 3, wherein the central control unit has a function of collecting internal data held by all the subordinate devices when it is determined that an intermittent transmission failure has occurred. Transmission equipment. 5. The slave device according to claim 4, wherein each of the slave devices has a function of detecting various abnormalities of the transmission frame generated in the transmission / reception operation of the transmission frame, and, when the abnormality of the transmission frame is detected, the contents of the abnormality and the number of times of occurrence of the abnormality. And the ability to record
A transmission device having a function of transmitting the recorded contents of the abnormality and the number of occurrences as transmission data to a central control device.