JPH0326939B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to loop communication in which devices (called nodes) connected to a duplex transmission line configured in a loop using optical cables communicate with each other. The present invention relates to a system, and particularly to a loop communication control method that improves the reliability of a loop communication system by preventing communication between healthy nodes from being interrupted even if a failure occurs in a plurality of nodes.

(b) Prior Art and Problems FIG. 1 is a block diagram illustrating a configuration example of a duplex loop communication system using optical cables. 1 is a monitoring node, and 2 to 10 are nodes.
Signals are transmitted in the directions shown by the arrows to the optical cables that connect each node, and communication between the nodes is performed. FIG. 2 shows an example of a frame structure for transmitting communication signals. 11 is a frame header for each node 2~
10 and the monitoring node 1. 12~
Reference numeral 16 denotes a time slot in which data used for mutual communication between nodes 2 to 10 is loaded. For example, when communicating from node 2 to node 6, a frame is first sent to monitoring node 1, and a frame header 11 at the beginning of the frame notifies the monitoring node 1 that it wishes to communicate with node 6. Monitoring node 1 analyzes the contents of frame header 11 and sends nodes 2 and 6
For example, the frame header 11 instructs the frame header 11 to communicate using the time slot 12. Also, for example, when node 3 notifies monitoring node 1 that it wishes to transmit data to nodes 7 and 8, monitoring node 1 notifies nodes 3, 7, and 8 to communicate using time slot 13. In this case, communication between nodes 2 and 6 and communication between nodes 3, 7, and 8 use different time slots, so
There is no problem with mutual communication.

For example, if nodes 5 and 9 fail at the same time, or if one node fails while the other node fails, monitoring node 1 detects this failure and instructs nodes 4 and 10 to Fold back the optical cable and connect it. Communication between the remaining nodes 2, 3, 4, and 10 is then enabled. However, even if the nodes 6, 7, and 8 are healthy, they cannot communicate because signal transmission with the monitoring node 1 that controls communication is interrupted. As described above, the conventional duplex loop communication system has a drawback in that when a plurality of nodes become impaired, there will be a section where communication between healthy nodes is not possible despite the duplication.

(c) Purpose of the Invention In view of the above drawbacks, the purpose of the present invention is to provide a plurality of monitoring nodes, prioritize the monitoring nodes, and arrange them at appropriate intervals to enable healthy communication between the nodes. The purpose of the present invention is to provide a loop communication control method.

(d) Configuration of the Invention The configuration of the present invention uses a duplex loop-shaped transmission line in which signal transmission directions are mutually opposite, and the duplex loop-shaped transmission line is turned back within the node according to instructions from a monitoring node. In a loop communication system capable of transmitting data, a plurality of monitoring nodes are provided, the monitoring nodes are connected to each other through communication channels, and a priority order for controlling the nodes is given to the plurality of monitoring nodes in advance, During normal operation, all nodes are controlled by one monitoring node with a high priority, and if the monitoring node with a high priority detects that the loop line is unable to transmit at multiple locations, the monitoring node The necessary instructions are transferred to other required monitoring nodes via the communication channel, and the monitoring nodes that receive the instructions loop back the transmission paths in their respective independent sections to form individual loop-shaped transmission paths. and control so that communication can continue.

(e) Embodiment of the Invention FIG. 3 is a configuration diagram of a loop communication system showing an embodiment of the present invention. Parts with the same functions as those in FIG. 1 are represented by the same symbols. In this embodiment, the monitoring node 20
A monitoring node 21 is provided outside the network. If the monitoring nodes 20 and 21 are connected, communication between the monitoring nodes becomes possible, so that mutual communication can be further improved. For example, it is assumed that the monitoring node 20 has a higher priority in controlling each node than the monitoring node 21. In this case, when all the nodes are normal, the monitoring node 20 with a higher priority controls the monitoring node 21 through the connection between the monitoring nodes, makes it standby as a standby, and the monitoring node 20 controls all nodes. . If nodes 4 and 8 fail as described above, monitoring node 2
0 instructs nodes 3 and 9 to connect the optical cables back as shown by the dotted lines. Also, the monitoring node 21 instructs the nodes 5 and 7 to connect the optical cables back as shown by the dotted line according to the instructions from the monitoring node 20.
Therefore, healthy nodes 2, 3, 9 and 5, 6, 7 can communicate independently. In this embodiment, two monitoring nodes are installed, but depending on the number of nodes, multiple monitoring nodes can be installed and inserted between the nodes at appropriate intervals.

FIG. 4 is a detailed block diagram of nodes 2-9 in FIG. Optical signal from terminal A goes to O/E conversion circuit 2
2 and is converted into an electrical signal and sent to the switching circuit 26. The switching circuit 26 is normally a control circuit 29
This signal is sent to the E/O conversion circuit 24 under the control of , where it is converted into an optical signal and sent from terminal C to the next node. The optical signal is sent from terminal D to O/E conversion circuit 25
The signal enters the circuit, is converted into an electrical signal, and is sent to the switching circuit 26. The switching circuit 26 normally sends this signal to the E/O conversion circuit 23 under the control of the control circuit 29, converts it into an optical signal, and sends it from terminal B to the next node. At this time, the electrical signal branched from the switching circuit 26 enters the high-speed conversion circuit 27. When the control circuit 29 is notified of the transmission of data from another node by the frame header data sent from the monitoring node, it controls the high-speed conversion circuit 27 to extract the data of the necessary time slot from the frame. The data is copied, taken in, subjected to level conversion, etc., and sent from the interface circuit 28 to the terminal device via the terminal E. Further, the control circuit 29 is an interface circuit 28.
When a data transmission request is received from the terminal device via the high-speed conversion circuit 27, the signal is placed on the frame header, and is sent to the monitoring node via the switching circuit 26 and the E/O conversion circuit 23 and/or 24. do. When a time slot for carrying data is assigned from the monitoring node, the data input from the terminal device via terminal E is received via the interface circuit 28, the time slot designated by the frame monitoring node is detected, and the switching circuit Send to 26th. The switching circuit 26 is connected to the O/E conversion circuit 22 and/or the O/E conversion circuit 22 and/or the O/E conversion circuit 22.
This data is placed in a designated time slot of the frame input from the E conversion circuit 25 and sent to the E/O conversion circuit 24 and/or the E/O conversion circuit 23. When the control circuit 29 is instructed by the monitoring node to connect the optical cable back, it controls the switching circuit 26 to change the output of the O/E conversion circuit 22 to E/E.
The output of the O/E conversion circuit 25 is connected to the O conversion circuit 23 and the E/O conversion circuit 24 . Furthermore, when the control circuit 29 receives an abnormality signal from the O/E conversion circuit 22 or 25, it notifies the monitoring node that the adjacent node is abnormal by putting it on the frame header.

FIG. 5 is a detailed block diagram of the monitoring nodes 20, 21 of FIG. An optical signal from a node with which communication is desired enters the O/E conversion circuit 30 and/or the O/E conversion circuit 33 from the terminal F and/or the terminal J, is converted into an electrical signal, and is sent to the switching circuit 34. The switching circuit 34 sends this signal to the high-speed conversion circuit 35 under the control of the control circuit 37. The control circuit 37 receives and analyzes the frame header from the high-speed conversion circuit 35, checks the usage status of the time slots of the frame, places necessary instructions such as specifying the time slot to be allocated on the frame header, and sends the frame header to the switching circuit. 34, the signal is sent to the E/O conversion circuit 32 and/or the E/O conversion circuit 31, where it is converted into an optical signal and sent out from the terminal H and/or terminal G. When communication between nodes is started, the control circuit 37 switches the switching circuit 34
The output of the O/E conversion circuit 30 is sent to the E/O conversion circuit 32, and the output of the O/E conversion circuit 33 is sent to the E/O conversion circuit 32.
It is connected to the O conversion circuit 31. It then copies the frame header from the high-speed conversion circuit 35, monitors information such as communication requests from the next node and node failure notifications, and allocates time slots each time a new communication request occurs. Control rights are given and received according to priority rights. At this time, for example, if the currently used system is a system consisting of the O/E conversion circuit 30 and the E/O conversion circuit 32, the communication signal between the nodes is input from the terminal F, the O/E conversion circuit 30, the switching circuit 34, and the high-speed Enters the conversion circuit 35 and memory 36,
The signal is sent to terminal H from the E/O conversion circuit 32 via the memory 36, the high-speed conversion circuit 35, and the switching circuit 34. The memory 36 adjusts the number of frames on the transmission path so that it is an integral multiple of the number of frames on the transmission path. The control circuit 37 also communicates with other monitoring nodes via the terminal K, and as described above, depending on the failure situation, it hands over or receives control authority to the other monitoring nodes depending on the priority.

(f) Effects of the Invention As explained above, the present invention enables healthy communication between nodes in a loop communication system even if a plurality of nodes fail, thereby improving reliability.

[Brief explanation of the drawing]

Fig. 1 is a block diagram illustrating a configuration example of a duplex loop communication system using optical cables, Fig. 2 is a diagram illustrating an example of a frame configuration for transmitting communication signals, and Fig. 3 is an embodiment of the present invention. FIG. 4 is a detailed block diagram of the node in FIG. 3, and FIG. 5 is a detailed block diagram of the monitoring node in FIG. 3. 1, 20, 21 are monitoring nodes, 2, 3, 4,
5, 6, 7, 8, 9, 10 are nodes, 22, 2
5, 30, 33 are O/E conversion circuits, 23, 24,
31 and 32 are E/O conversion circuits, 26 and 34 are switching circuits, 27 and 35 are high-speed conversion circuits, 28 is an interface circuit, 29 and 37 are control circuits, and 36 is a memory.

Claims (1)

[Claims] 1. A loop that uses a duplex loop-shaped transmission path in which the signal transmission directions are mutually opposite, and that can transmit data by returning the duplex loop-shaped transmission path within the node according to instructions from a monitoring node. In the communication system, a plurality of monitoring nodes are provided, and the monitoring nodes are connected to each other by a communication channel,
Priority is given to the plurality of monitoring nodes in advance to control the nodes, and during normal operation, one monitoring node with a high priority controls all nodes, and when the loop line becomes unable to transmit at multiple locations, the priority is given to the nodes. If a monitoring node with a higher ranking detects the detection, the required instruction is transferred from the monitoring node to other required monitoring nodes via the communication channel, and the monitoring nodes that received the instruction perform independent A loop communication control method characterized by looping back transmission lines within a section to form individual loop-shaped transmission lines and controlling the lines so that communication can continue.