JPH0687559B2 - Bus type LAN - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus-type LAN, and more particularly to a token-passing bus-type LAN in which transmission is controlled based on a logical ring that represents the order in which tokens are sequentially delegated.

<< Summary of the Invention >> The present invention provides a bus in which a token is sequentially circulated between nodes based on a logical ring constructed by polling processing by providing a management station and a normal station in a node formed in a bus type transmission line. In a type LAN, if the succeeding station that should receive the token does not receive the token due to a failure, etc., the normal station that sends the token detects the abnormality of the succeeding station and once returns the token to the management station. The management station excludes the succeeding station from the logical ring and sends the token to a new succeeding station, thereby preventing the loss of the token.

《Prior art and its problems》 Conventionally, as a transmission control method of a bus-type LAN, only a station having an access right of a transmission line, a so-called token, transmits data, and each station connected to the transmission line has a token. There is a token passing method of patrol.

In this token passing method, when an abnormality such as a failure occurs in a normal station that should receive the token during patrol of the token, the station handing over the token to other stations to search for a new subsequent station, Processing has been performed in which frames are sequentially transmitted, a new logical ring is constructed based on the responses, normal stations in which an abnormality has occurred are excluded from the logical ring, and normal operation is restored.

However, since this method is complicated in processing, it takes a long processing time to return to a normal state, and is not suitable for a LAN that requires high speed.

Further, each normal station must be equipped with a hardware configuration for performing these processes, which causes a problem that the entire system becomes expensive.

<Object of the Invention> The present invention has been made to solve the above problems. The object of the present invention is to allow a normal station that joins a logical ring to receive a token due to a failure or the like. It is to provide a bus-type LAN capable of executing, in a short time, the process of removing the normal station from the logical ring, constructing a new logical ring, and returning to normal operation when it disappears.

<< Structure and Effect of the Invention >> In order to achieve the above object, the present invention configures a communication node with a management station and a plurality of normal stations in a bus type LAN that is transmission-controlled by a token passing system based on a logical ring. Collection means provided in the management station for collecting the logical ring joining data regarding the normal station by performing regular polling, and storage means provided in the management station and the ordinary station for storing the logical ring joining station list,
Based on the list data sent from the management station and the sending means for simultaneously broadcasting the logical ring subscriber station list data updated / stored in the storage means of the management station to other normal stations List updating means for updating the storage means provided in the normal station and the normal station, and when the token is transferred to the succeeding station, the token rejection of the succeeding station is detected from the presence or absence of the response of the succeeding station. Detecting means and normal station, when the detecting means detects the non-acceptance of the token of the succeeding station, return means for returning the token to the management station, and the management station, which is provided by the returning means, the token is returned The following stations that do not accept the token when
It is characterized by comprising a logical ring changing means for excluding it from the logical ring and a token transmitting means provided in the management station for transferring the token returned to the management station to a new succeeding station.

In the bus type LAN according to the present invention, when the succeeding station that should receive the token does not receive the token due to the occurrence of a failure, the normal station that transmits the token detects the abnormality of the succeeding station, and once By returning to the management station, the management station removed the subsequent station from the logical ring, and sent the token to the new subsequent station, it was possible to respond to the failure that occurred when the token was handed over and to return to normal operation. Since the speed is increased and the normal station is simply configured, the cost of the entire network can be reduced.

<< Description of Embodiments >> FIG. 1 is a diagram showing an overall configuration of a bus LAN according to the present invention.

In the figure, a bus-type LAN is configured by connecting a management station 1 and ordinary stations 2 to N, which form a communication node, to a transmission line 10 formed of a coaxial cable or the like. The management station 1 is a communication node in a bus type LAN, and has a polling function for other normal stations 2 to N and a management function for logical ring joining or leaving. The preliminary management station 6
Besides having a function as a normal station, it becomes a management station when the management station 1 goes down.

FIG. 2 is a block diagram showing the internal structure of the management station 1. As shown in the figure, the management station 1 has a CPU 20, ROM 21, RA
It is composed of an M22, a transmission controller 23, and an internal bus 24 connecting these. The CPU 20 controls the transmission controller 23 according to the program stored in the ROM 21 to transmit / receive various frames to / from the transmission path 10. The RAM 22 is used as a buffer for temporarily holding a network management information table 51, which will be described later, transmission / reception data, and various other data. Normal stations 2 to N
The internal structure of is also substantially the same as that of the management station 1 shown in FIG.

FIG. 3 is a diagram showing the configuration contents of the network management information table 30 provided in the RAM 22. The table 30 stores various management information about each node on the network, and the memory area address in the table 30 corresponds to the node numbers of the nodes 1 to N. The configuration of each memory area stores, for example, as shown in the memory area 30-2, a communicable bit 30a indicating whether or not the corresponding node 2 is communicable, and similarly other information regarding the node 2 is stored. It consists of area 30b. The communicable bit 30a is set to ON when the corresponding node 2 joins the logical ring when the logical ring is constructed. Thus, when building a logical ring,
All of the communicable bits 30a of are set to either ON or OFF, and a logical ring is constructed by the nodes set to ON. Based on this logical ring, tokens are sequentially transferred, and the order is the address order of the nodes assigned to the table 30. These tables 30
The network management information related to the logical ring and the like stored in (1) is updated by periodic polling of the management station 1 and then transmitted to each normal station by simultaneous broadcast notification. The logical ring subscribing station that has received this information can know the succeeding station that delegates the token from its data content.

FIG. 4 is a diagram conceptually showing the logical ring constructed by the periodic polling process of the management station 1 in this way. In this logical ring, the tokens are transferred in the memory area address order in the table 30 to which the corresponding node is allocated. The token has gone round,
When the normal station N at the end is reached, the token returns to the management station 1 at the head.

FIG. 5 is a flowchart showing the operation in the normal station and the management station.

In the figure, the normal station that has completed the predetermined data transmission process transmits a token frame to the subsequent station based on the logical ring (step 501).

Then, it is confirmed whether or not the token is successfully sent to the succeeding station (step 502). This confirmation is performed by monitoring the transmission of the command frame or the token frame on the transmission line 10 within a predetermined time after the transmission of the token frame.

If the transmission of these signals is confirmed on the transmission line 10, it is judged that the token has passed safely (step 50).
2) Yes, the process ends.

If transmission of these signals cannot be confirmed on the transmission line 10, it is determined that the token has not passed (step 50).
(2 negative), transmission of the token frame is started again (step 503 negative, step 501). If the transmission of the token frame is completed a prescribed number of times without confirming the signal transmission (Yes at Step 503), it is determined that some failure that the subsequent station cannot receive the token has occurred, and the token return frame is sent to the management station 1. Send (Step 50
4), end the processing of the normal station.

When the management station 1 receives the token return frame from the normal station (step 505), it determines the address of the abnormal succeeding station from the source address added to the token return frame and the network management information table 30,
The communicable bit 30a of the address is changed to off (step 505).

Next, based on the changed table 30, the token frame is transmitted to the normal station which is a new succeeding station on the logical ring (step 506), and the processing of the management station 1 is ended.

The data regarding the table 30 of the management station 1 changed by these processes is transmitted to each normal station by the simultaneous broadcast notification, and the table 30 provided in the RAM 22 of each normal station is updated. Based on the new logical ring
The token is transferred.

FIG. 6 is a timing chart of the command frame transmitted on the transmission line 10.

FIGS. A and b show transmission of a command frame when the normal station 3 fails in the logical ring in FIG. 4, FIG. A showing a conventional token passing system, and FIG. B showing the system of the present invention. It is a thing.

In the conventional method, as shown in FIG. A, when the normal station 2 sends a token frame to the normal station 3 and no response is obtained, the normal station 2 sends another station to search for a subsequent station. In response, a command frame is sent. Then, a response frame is returned from the normal station 4, which is a new succeeding station,
The token is passed from the ordinary station 2 to the ordinary station 4.

According to the present invention, as shown in FIG. B, when a token frame is sent from the ordinary station 2 to the ordinary station 3 and no response is obtained, the token is immediately returned to the management station 1. Next, the management station 1 refers to the logical ring data,
The token is sent to the normal station 4, which is a new succeeding station. As a result, it is possible to shorten the time required to return to the normal processing as compared with the conventional case.

As described above, in the present invention, the normal station on the logical ring is
When a failure such as a failure in which the token cannot be received occurs, the token is returned to the management station 1 and then immediately transferred to a new succeeding station, which shortens the time required to return to normal operation.

In addition, since the normal station does not need to search for the other station to pass the token, the hardware configuration can be simplified accordingly.
The cost of the entire network can be reduced.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a bus LAN according to the present invention, and FIG.
FIG. 4 is a block diagram showing the internal structure of the management station, FIG. 3 is a block diagram of the network management information table, FIG. 4 is a diagram conceptually showing a logical ring, and FIG. The flow chart shown in FIG. 6 is a timing chart of the command frame transmitted on the transmission line 10. 1 …… Management station (node) 2 to N …… Normal station (node) 10 …… Transmission path 20 …… CPU 21 …… ROM 22 …… RAM 23 …… Transmission controller 24 …… Internal bus 30 …… Network management Information table 30a ...... Communicable bit

Claims (1)

[Claims] 1. In a bus-type LAN in which transmission is controlled by a token passing system based on a logical ring, a communication node is composed of a management station and a plurality of normal stations, and is provided in the management station to perform regular polling. Collection means for collecting logical ring joining data regarding stations, storage means provided in the management station and normal station for storing a list of logical ring joining stations, and logical ring joining station updated / stored in the storing means of the management station A list updating method that sends list data to other normal stations simultaneously and a list unit that receives the list data sent from the management station and updates the storage unit provided in the normal station based on the list data. Means, and usually provided in the station, when delegating the token to the subsequent station,
Detecting means for detecting token refusal of the succeeding station based on the presence or absence of the response of the succeeding station, and return for returning the token to the management station when the detecting means detects the refusal of the token of the succeeding station Means and a logical ring changing means provided in the management station for excluding a subsequent station that does not accept the token from the logical ring when the token is returned by the above-mentioned returning means, and provided in the management station and returned to the management station A bus-type LAN characterized by comprising a token transmitting means for delegating the generated token to a new succeeding station.