JP2716307B2 - Local area network system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local area network system for connecting subsystems through a plurality of transmission lines.

[0002]

2. Description of the Related Art At present, main types of local area networks are a bus type, a loop type and a composite type thereof.

[0003] In the loop type and its combined type, in order to improve reliability which is generally inferior to that of the bus type, failure countermeasures such as a loopback method are taken inside the network, and the reliability is further improved. For this reason, a loop type local area network has been duplicated.

In some bus-type local area network systems, transmission lines are duplicated because there is a great possibility that a failure in some devices will affect the entire network.

In a local area network of a bus type, a loop type and a composite type thereof, one of the transmission lines is usually used as a control means of a multiplexed transmission line, and when a failure occurs in the transmission line. An alternative path method using another transmission path is generally used.

[0006]

In the alternative path method, it is necessary to select which of the remaining paths is to be used as the alternative path in the case of one system, and the selection method is complicated depending on the degree of multiplexing. Become. When a logical path is set after a failure, a delay in message transfer becomes a problem in a system with high real-time properties.

Further, when there are various types of subsystems on the local area network, it is necessary to perform control in consideration of the number of multiplexed transmission lines, real-time performance, transmission load, and CPU load due to communication due to problems inherent to the subsystems. There is a drawback that the network system needs to be controlled uniquely for each sub-system unit, resulting in a very complicated and inconsistent network system.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a local area network system in which subsystems are multiplexly connected by a plurality of transmission lines.
A transmission message identifier prepared for each partner subsystem and used for determining the validity of the received message in the receiving subsystem, and a transmission environment for transmitting a message to another subsystem prepared for the partner subsystem is described above. A transmission message identifier for preparing a first message by adding a transmission message identifier to the message each time the message is transmitted, comprising: Means, a transmission message identifier updating means for updating the transmission message identifier according to a predetermined rule each time an acknowledgment is received, and transmitting the first message in accordance with the transmission environment defined by the multiplex transmission status. Communication means to a plurality of transmission paths to output to the transmission path of, The receiving subsystem includes an expected message identifier that is prepared for each partner subsystem and usually has the same value as the value of the transmission message identifier and is used for determining the validity of the received message. Received message determination means that receives the first message and returns the acknowledgment only when the value of the transmitted message identifier and the value of the expected message identifier in the first message are received when the first message is received, An expected message identifier updating unit that updates the expected message identifier according to the rule when the first message is received, and deletes the transmitted message identifier from the first message when the first message is received. Transmission message identifier deleting means, and deleting the transmission message identifier And having a message processing means for processing the first message.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. A message is transmitted from a subsystem A to a subsystem B between subsystems connected to a local area network having a triple transmission line. It shows the case.

First, a method of setting a multiplex transmission status 19 for determining a transmission method corresponding to a transmission path to be transmitted in transmission will be specifically described.

The multiplex transmission status includes the following statuses.

[0013]

[Table 1]

Next, a method of initializing a transmission message identifier / expected message identifier in setting a logical path and a method of managing a transmission path will be specifically described.

In FIG. 1, when setting a logical path between the subsystem A (1) and the subsystem B (2), the subsystem A (1) Establish a data link with B (2).

The subsystem (1) first initializes the transmission message identifier 15 for the subsystem B and the expected message identification (not shown) by the transmission path on which the data link is established, and the transmission path of the subsystem B Are set to the "enabled" state.

Subsystem B (2) also has subsystem A
By establishing the data link with (1), the transmission message identifier (not shown) for the subsystem A and the expected message identifier 20 are initialized, and the availability status of the transmission line on which the data link of the subsystem A is established is set to " Possible ”state. As a result, the logical path between the subsystem A (1) and the subsystem B (2) is in a connected state, and transmission and reception are possible. Similar processing is performed for re-link establishment.

It is assumed that the transmission message identifier / expected message identifier is an n-bit binary number, the initial value is 1, and the updating is incremented by one.

Next, a control flow when a message is transmitted from the subsystem A (1) to the subsystem B (2) will be described. (1) Multiple transmission First, in the subsystem A (1), the transmission message identifier 15 of the subsystem B (2) is added to the message to be transferred by the transmission message identifier assigning means 12.

Next, the communication means 14 to a plurality of transmission paths is
When multiplex simultaneous transmission is set with reference to the multiplex transmission status 19 for the subsystem B, the available status of the transmission line corresponding to the transmission transmission line is checked. Are simultaneously transmitted through the transmission lines 1, 2, and 3.

On the subsystem B (2) side, it is assumed that the message sent from the subsystem A is first sent via the transmission line 2. When the subsystem B (2) receives the message from the transmission path 2, the received message determination means 21 sends the transmission message identifier 1 added to the message.
5 matches the expected message identifier 20 of the subsystem A, so that the message is determined to be a valid message, and the expected message identifier updating means 22 updates the expected message identifier 20 of the subsystem A. Then, after deleting the received message identifier by the transmission message identifier deletion unit 23, the message processing unit 24 performs a unique process on the message.

When the transmission control acknowledgment of this message is transmitted to the subsystem A (1), the subsystem A (1) The transmission message identifier 15 is updated.

Immediately thereafter, the same message is received from the transmission lines 1 and 3. However, since the expected message identifier 20 has already been updated, the transmitted message identifier added to the received message does not match the expected message identifier. Because they are ignored, they will not be duplicated.

When a failure occurs in transmission control, the usable status is set to the "impossible" state, and the subsystem that has detected the failure removes the failure and establishes a data link again.

According to the present method, even if a failure occurs in any of the transmission lines 1, 2, and 3, it is possible to perform communication without losing the real-time property. (2) Time difference transmission First, in the subsystem A (1), the transmission message identifier 15 of the subsystem B is added to the message to be transferred by the transmission message identifier assigning means 12.

Next, the communication means 14 for a plurality of transmission paths refers to the transmission priority status for the subsystem B when the multiplexed time difference transmission is set by referring to the multiplex transmission status 19 for the subsystem B. Availability statuses 16 to 18 corresponding to the transmission path with the highest priority
Is checked, and if it is in the “possible” state, a message to which the transmission message identifier 15 is added is transmitted through the transmission path. If the usable status is "impossible", the same process is performed for the transmission line with the next highest priority.

When transmitting to the subsystem B, the transmission is monitored by the timer value of the multiple priority transmission time interval. If there is an acknowledgment in transmission control from the subsystem B during this monitoring time, all the transmission operations on the subsystem A side are completed. If there is no acknowledgment of the reception from the subsystem B during this monitoring time, the time difference transmission is performed to the next highest priority transmission path.

On the subsystem B (2) side, it is assumed that the message sent from the subsystem A is first sent through the transmission line 2. When the subsystem B (2) receives the transmission message from the transmission path 2, the received message determination unit 21 determines that the transmission message identifier added to the message matches the expected message identifier of the subsystem A, and thus determines that the message is a valid message. Then, the expected message identifier 20 of the subsystem A is updated by the expected message identifier updating means 22. Then, after the message identifier is deleted from the message received by the transmission message identifier deletion means 23, the message processing unit 24 performs the unique processing of the message.

An acknowledgment of this message in transmission control is transmitted to the subsystem A (1). When the transmission message identifier updating means 13 completes the transmission, the subsystem A (1) The transmission message identifier 15 is updated.

If the acknowledgment in the transmission control is not notified to the subsystem A (1) within the monitoring time, the same message is subsequently received from the transmission line 1 or 3, but the expected message identifier is already updated. Therefore, the transmitted message identifier added to the received message and the expected message do not match and are ignored, so that no duplicate processing is performed.

The usable status is not updated to "impossible" even if the monitoring timer expires for each transmission.
This is because in a bus-type local area network, the number of messages increases and message collisions occur, and although this is not a failure, communication operations may be delayed to some extent.

When a failure occurs in the transmission control, the detecting subsystem sets the usable status to the "impossible" state, releases the data link, and removes the data link from the communication target path.

According to this method, even if a failure occurs in any one of the transmission lines 1, 2, and 3, communication without losing a constant real-time property becomes possible. (3) Normal Transmission First, in the subsystem A (1), the transmission message identifier of the subsystem B is added to the message to be transferred by the transmission message identifier assigning means 12.

Next, the communication means 14 for a plurality of transmission paths refers to the multiplex transmission status 19 for the subsystem B and, if the normal transmission is set, performs transmission on the designated transmission path.

On the subsystem B (2) side, it is assumed that the message sent from the subsystem A is sent via the transmission line 2. When the subsystem B (2) receives the transmission message from the transmission path 2, the received message determination unit 21 determines that the transmission message identifier added to the message matches the expected message identifier of the subsystem A, so that the message is a valid message. The expected message identifier 2 of the subsystem A
Update 0. Then, after the message identifier is deleted from the message received by the transmission message identifier deletion unit 23, the message processing unit 24 performs a unique process on the message.

An acknowledgment of this message in the transmission control is transmitted to the subsystem A (1). When the transmission message identifier updating means 13 completes the transmission, the subsystem A (1) The transmission message identifier 15 is updated.

In this embodiment, when a failure is detected upon completion of transmission, or when a failure is detected asynchronously, the usable status is updated to "impossible".

The transmission priority status is fixed in an initialized state.

[0039]

As described above, according to the present invention, multiplex synchronous transmission, multiplex time difference transmission, and normal transmission can be arbitrarily selected and implemented as transmission methods in accordance with conditions unique to each subsystem. As a result, there is an effect that a network system with easy control and uniformity can be realized.

In the case of multiplex simultaneous transmission and multiplex time difference transmission, the transmission side and reception side CP
There is an effect that the real-time property of selecting a good transmission path can be guaranteed without increasing the U load.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

[Explanation of symbols]

 1 Subsystem A 2 Subsystem B 11 Message processing unit 12 Transmission message identifier assigning means 13 Transmission message identifier updating means 14 Communication means to multiple transmission paths 15 Transmission message identifier 16 Usable status 17 Usable status 18 Usable status 19 Multiplexing Transmission status 20 Expected message identifier 21 Received message determination means 22 Expected message identifier update means 23 Transmission message identifier deletion means 24 Message processing unit

Claims (1)

(57) [Claims] In a local area network system in which subsystems are multiplexed and connected by a plurality of transmission lines, a transmitting subsystem prepares for each partner subsystem and judges the validity of a received message in a receiving subsystem. The transmission message identifier used for, and a multiplex transmission status prepared in advance for the transmission procedure of the message to the plurality of transmission paths as a transmission environment when transmitting a message to another subsystem prepared for each of the partner subsystems A transmission message identifier adding means for adding the transmission message identifier to the message each time the message is transmitted to create a first message; and a predetermined rule for setting the transmission message identifier each time an acknowledgment is received. Message identifier updating means for updating by the Communication means for outputting the first message to the plurality of transmission paths in accordance with the transmission environment defined by the communication status. Comprises an expected message identifier used to determine the validity of the received message having the same value as the value of the transmission message identifier, and when the first message is received from the plurality of transmission paths, the Received message determination means for receiving the first message and returning the acknowledgment only when the value of the transmission message identifier is equal to the value of the expected message identifier, and the expected message identifier when the first message is received Expected message identifier updating means for updating the first message according to the rule; and A transmission message identifier deleting unit for deleting the transmission message identifier from the first message, and a message processing unit for processing the first message from which the transmission message identifier has been deleted. Network system.