JPH03268537A - Ring type local aera network system - Google Patents

Abstract

PURPOSE:To surely recover the abnormality in token issuing by sending an idle pattern in which only one station among plural ones connected to a transmission line becomes an idle pattern output station at the time of detecting the abnormality in token issuing, then clearing the transmission line. CONSTITUTION:In a token erasing state, whether a token is issued from a taken issuing station within a prescribed monitoring time or not is decided and when the decided result is NO, only one station among plural stations which are not the token issuing station is regarded as the station detecting the abnormality in the token issuing, outputs an idle pattern and starts a processing for clearing a ring (ring type transmission line 11). Even when an irregular data pattern is generated due to the noise of the ring type transmission line during the period of token issuing and the abnormality in token issuing is generated, the idle pattern is sent to the transmission line only by one station among plural ones connected to the transmission line, so that the transmission line can surely be cleared and the abnormal state in the token issuing can easily be recovered.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) This invention relates to a ring-type LAN (Local Area Network) system that applies a token passing method, and in particular to an abnormality recovery process when a token issuance abnormality occurs. Regarding the method.

(Prior Art) In a ring-type LAN system in which multiple stations are connected by a ring-shaped transmission path (ring-type transmission path), a special frame (token frame) generally called a token is The station that secured the token acquires the transmission right and transmits it to another station, and when the transmission is finished, the token is released by returning it to the ring, so-called token passing. Communication control based on the method is applied.

In such a ring-type LAN system using a token passing method, if a token disappears from the ring, transmission cannot be performed. In this case, conventionally, the station with the largest address (station address) among the stations on the ring (maximum address station) is detected, and a token is issued by the station with the largest address or the token issuing device. However, if this maximum address station fails to issue a token, it will no longer be possible to transmit.

Now, token issuance failure occurs when (1) a data pattern outside the system specified range occurs on the transmission line due to transmission line noise, or (2) when the token issuing device breaks down. If a token issuance failure occurs due to the factor (2) above, it can be resolved by initializing the device or separating (separating) the device from the ring. On the other hand, in case (2) above, failure recovery is difficult. In addition, even if you attempt to recover from the failure due to the factor (■), each station can only know whether it is its own station, the station with the highest address, or not. A specific pattern indicating that the frame is not a frame will be output. There is a risk that the idle pattern will continue to be outputted to the ring intermittently due to the timing difference in token issuance abnormality detection at each station, and the system will not be able to escape from the abnormality recovery (distributed abnormality recovery) trial state.

(Problem to be solved by the invention) As mentioned above, conventionally, when a data pattern outside the system specifications occurs due to transmission line noise, token issuance errors are not recovered, and distributed error recovery is not performed. However, due to the timing difference in the detection of abnormality in token issuance at each station, there was a problem in that it was not possible to exit the abnormality recovery trial state.

This invention was made in view of the above circumstances, and its purpose is to correctly clear the ring (transmission path) even if an unspecified data pattern occurs during token issuance, and to reliably recover from the token issuance abnormality. Our objective is to provide a ring-type LAN system.

[Structure of the invention] (Means for solving the problem) This invention provides a ring type L that applies token passing.
In the AN system, idle pattern output station determining means determines an idle pattern output station from among a plurality of stations connected to a transmission path (ring type transmission path), and token issuing layer determining means determines a token issuing layer. , a token issuance abnormality detection means for detecting an abnormality in token issuance from the token issuance layer, and when a token issuance abnormality is detected by the token issuance abnormality detection means, an idle pattern is sent to the transmission path by an idle pattern output station. A ring clearing means for clearing the transmission line (ring) as a lever is provided, and one of the multiple stations connected to the transmission line (participating in the ring) becomes an idle pattern output station and is idle. The feature is that the transmission path is cleared by sending out a pattern. Further, in the present invention, two idle pattern output stations, a master and a slave, are determined by the idle pattern output station determining means, and basically the idle pattern output station on the master side performs idle pattern transmission, and the idle pattern output station on the master side The idle pattern is sent out by the idle pattern output station on the slave side only when the pattern output station is abnormal.

(Function) According to the above configuration, if a non-standard data pattern occurs due to ring-type transmission line noise or the like during token issuance, and a token issuance error occurs, multiple stations connected to the transmission line Since one station determined by our idle pattern output station determining means sends out an idle pattern for one round of the ring to the transmission path, the transmission path is reliably cleared and the token issuing abnormality can be easily recovered. . In addition, by having two idle pattern output stations, a master and a slave, even if the master is unable to send out an idle pattern due to an error, the slave can send out an idle pattern instead. A reliable recovery is possible.

(Example) Figure 1 shows a ring type L that applies the token passing method.
FIG. 2 is a system configuration diagram showing an example of an AN. In the figure, 11 is a ring type transmission line, and 12-1 to 12-5 are stations (stations, communication devices) that are connected to the ring type transmission line 11 and perform data communication via the ring type transmission line 11. . The stations 12-1 to 12-5 are connected to terminals (not shown) that communicate with each other using the ring-type transmission line 11. In this embodiment, stations 12-1 to 12-5
The address (station address) shall be as follows.

Station 12-1...00FOh Station 12-2...0002h Station 12-3...0F12h Station 12-4...00 F 1. h Station 12-5...0710h Note that the suffix h indicates hexadecimal representation.

Now, in the system shown in FIG. 1, there is only one token for the ring (transmission path +1 of the ring type LAN). however,
When the system starts operating, there are no tokens on the ring. This state is called a token loss state. Upon entering this token loss state, station 12-i (i −1
~5) performs a token issuing layer determination process to determine the station that issues the token (token issuing layer), and the station determined as the token issuing layer performs the token issuing process. This operation will be explained with reference to the flowchart in FIG. First, the station 12-i starts time monitoring to check whether a token is issued within a predetermined time after entering the token loss state (step Sl). Next station 1
2-i uses a maximum address station detection mechanism (not shown) to detect the station with the maximum address (maximum address station) from among the stations participating in the ring (connected to the ring type transmission line 11). is detected (step S2). This is for each station 1
2-1: While transmitting a specific frame (called a claim frame) with the address of the local station added onto the ring transmission line II, compare the station address in the claim frame transmitted from upstream with the local station address. However, if the station address in the claim frame is larger, the claim address from upstream is passed downstream. Therefore, in the end, only the claim frame from the highest address station goes around the ring transmission path 11 and returns to its issuer (the highest address station), so that the highest address station detects the claim frame.

Based on the detection of the maximum address station in step S2, the station 12-1 determines whether or not its own station is the maximum address station (step S3), and if it is the maximum address station, determines its own station as the token issuing layer. (Step S4). In this case, the station 12-1 immediately proceeds to token issuing processing and issues a token on the ring type transmission line 11 (step S5). The token issuing layer 12-j then has a status indicating that it has become a token issuing layer (token issuing layer status).
(Step S6) Thereafter, an idle pattern output station determination process is started to extract two stations (a master side idle pattern output station and a slave side idle pattern output station) that output idle patterns (step S6). In the system shown in FIG. 1, among the stations 12-1 to 12-5, the address "0F12h" of the station 12-3 is the largest, so the station 12-3 becomes the token issuing layer.

On the other hand, if the station 12-1 is not the highest address station (if the complaint frame from the own station was not returned), and therefore cannot become the token issuing layer, then the station 12-j ( Here, station 12-1゜12-2.12
-4.12-5) determines whether a token has been issued by the token issuing authority within a predetermined monitoring time (step S7), and if YES, enters normal mode (normal state). On the other hand, if the determination in step S7 is No, the station 12-i, that is, the station that is not the token issuing station, assumes that a token issuing abnormality has been detected, and only one of them outputs an idle pattern and rings. Type transmission line 1
1) Enters the process to clear (ring clear process).

This ring clearing process will be explained below with reference to the flowchart of FIG.

The main station 12-i (station other than the token issuing station) determines whether it is the own station or the master side idle pattern output station based on the status within the own station (step 5ll).
If YES, in order to clear the ring (ring type transmission line 11), an idle pattern is sent out on the ring for one round of the ring (step S2). On the other hand, step S1
If the determination is NO, the station 12-L, that is, the station that is not the master-side idle pattern output station, determines whether it is the own station or the slave-side idle pattern output station based on the status within the own station (step 513 ). If the determination in step 31B is YES, that is, if the own station is the slave side idle pattern output station, the station will take the time necessary to confirm the idle pattern output from the master side idle pattern output station, for example, the idle pattern output station. The ring is monitored for the time required to output the pattern for four rotations of the ring (step 514). If idle pattern output is not confirmed within the monitoring time due to some factor (transmission line noise, etc.) (step 515), the slave side idle pattern output station replaces the master side idle pattern output station on the ring. An idle pattern is sent out for one rotation of the ring (step 516). When the slave side idle pattern output station executes the idle pattern output, it stores a status indicating that (idle pattern output status) in its own station (step 517), and enters the idle pattern output station determination process described below. .

Now, in order to realize the ring clearing process in the event of a token issuance error as described above, all stations connected to the ring +2
Is it necessary to extract two stations from -i as idle pattern output stations? The idle pattern output station determination process for extracting this idle pattern output station will be explained with reference to the flowchart of FIG. 4. First, station 12-1 has two messages in its own station: ■ Token issuing station status indicating that the token was issued by the local station or as the token issuing station; ■ A master side or slave side idle pattern output station other than the own station has left the ring. (Idle pattern output station detachment reception status), ■Idle pattern output status indicating that the local station has executed idle pattern output as a slave side idle pattern output station. It is checked whether any status is stored (step 521). If the status of ■ or ■ above is stored (step 522), station 1
2-i changes its own station status to the master side idle pattern output station (step 823) and enters the normal mode. Next, if the status of the above ■ is stored, or if the status has been changed to the master side idle pattern output station (step 524), station 12-1 will change the status of the master side idle pattern output station to other stations. A master-side idle pattern output station determination notification indicating that the station has become a pattern output station is transmitted via the ring transmission path 11 (step 52
5). The most significant digit value other than "0" in the address of the local station is added to this decision notification. Therefore, if it is the station 12-4 that sent this decision notification, or for example the station 12-3 that became the token issuing authority and issued the token, then the address of the station 12-3 is "0F12h". , "Fh" is added to the decision notification.

The master side idle pattern output station determination notification from the station 12-i (station 12-3) described above is transmitted to each of the other stations participating in the ring. Each station (here, stations 12 to 1.
12-2.12-4.12-5) enters the slave side idle pattern output station search state upon receiving the above decision notification. In this state, first search in which digit of your own address the numerical value attached to the above decision notification exists,
If the numbers are the same, the master side idle pattern output station (12-3) is notified of its own station address. Each station (receiving station of master side idle pattern output station determination notification,
Here station 12-1.12-2.12-4.12-5)
After the above search is completed, waits for a certain period of time for a slave idle pattern output station determination notification from the master idle pattern output station, which will be described later. If the slave side idle pattern output station determination notification is not received within the time,
Each station above is the next value after the previous search value (for example, Fh
If so, Eh is calculated, and if lh, Fh) is calculated. Then, each station searches whether the calculated numerical value exists in its own station address, and if it exists, it notifies the master side idle pattern output station (+2-3) of its own station address. This operation (address search operation) ends when a slave-side idle pattern output station determination notification is received or when this operation is repeated a predetermined number of times, for example, 15 times, and the normal mode is entered.

On the other hand, the master side idle pattern output station (12-
3) monitors address notifications from other stations for a certain period of time from the time of notification of this decision. This monitoring time needs to be longer than the maximum number of times (15 times) for address searches of other stations. If there is no address notification from another station within this monitoring time, the idle pattern output station on the master side (12
-3) enters normal mode. On the other hand, if the first address notification is received after the master side idle pattern output station decision notification, the master side idle pattern output station (1
2-3) waits for the time required for one address search operation and checks whether there is any other address notification. Then, the master side idle pattern output station (12-3) determines the maximum address station from the address notification information received during this period,
That station is determined as the slave side idle pattern output station, and all stations (station 12-1.12-2.12-4.12-
5) and enters normal mode (step 526).

Based on the slave side idle butter output station determination notification in step S26, the station that detects that its own station has become the slave side idle pattern output station stores a status to that effect within its own station. In the ring type LAN system of FIG. 1, there are two stations other than the master side idle pattern output station 12-3 that have "Fh": station 12-■ and station 12-4. Among these stations +2-1, 12-4, the address of station 12-4 is larger, so in the system of FIG. 1, station 12-4 is determined as the slave-side idle pattern output station. When the master side idle pattern output station 12-3 becomes abnormal, this station 12-4
It becomes the master instead of 2-3.

Next, an explanation will be given of the operation associated with the departure of the idle pattern output station from the ring. First, if the idle pattern output station on the master or slave side leaves the ring due to a failure or other reason, the idle pattern output station on the other side (
(slave side or master side), ring type transmission line 1
A notification to that effect (idle pattern output station ring withdrawal notification) is sent via 1. The other idle pattern output station that has received this notification stores the idle pattern output station withdrawal reception status within itself.

The operation of each station in the system shown in FIG. 1 is summarized and shown in the state transition diagram shown in FIG. In addition, in Fig. 5, the symbol A
-F indicates a transition condition, and its specific contents are as follows.

■Transition condition A: Token issued, idle pattern output by master side idle pattern output station.

■Transition condition B Token issue error detection.

■Transition condition C Idle pattern output station (master side or slave side)
Completed output of idle pattern for one rotation of the ring.

■Transition condition D A token is issued, and the idle pattern output station (master side or slave side) does not output an idle pattern.

Alternatively, a token is issued and an idle pattern is output from the idle pattern output station on the slave side.

■Transition condition E Idle pattern output station (master side or slave side)
Decided.

■Transition condition F Idle pattern output station (master side or slave side)
Separation from the ring occurred.

In the above embodiment, the case where the maximum address station is detected is explained to determine the token issuing layer and the slave side idle pattern output station, but it is also possible to detect the minimum address station or use other determination methods. An algorithm may be used.

[Effects of the Invention] As described in detail above, according to the present invention, even if a non-standard data pattern occurs due to ring-type transmission line noise during token issuance, etc., and a token issuance error occurs, the connection to the transmission line will not be interrupted. Since the idle pattern is sent to the transmission path by only one station among the plurality of stations in the system, the transmission path is reliably cleared and recovery from a token issue abnormality can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of a ring-type LAN system using a token passing method according to an embodiment of the present invention, and FIG.
The figure is a flowchart for explaining the token issuing layer determination process and the token issuing process in the same embodiment.
The figure is a flowchart for explaining ring clear processing in the same embodiment, FIG. 4 is a flowchart for explaining idle pattern output station determination processing in the same embodiment, and FIG. 5 is the operation of each station in the system of FIG. 1. It is a diagram showing the state transition of. 11... Transmission line, 12-1 to 12-5... Station.

Claims (2)

[Claims] (1) In a ring-type local area network system in which multiple stations are connected by a ring-type transmission path and a token passing method is applied, an idle pattern is selected from among the multiple stations connected to the transmission path. an idle pattern output station determining means for determining an idle pattern output station for sending out a token; a token issuing station determining means for determining a token issuing station for issuing a token when a token is lost; a token issuance abnormality detection means for detecting an abnormality in issuance; and when the token issuance abnormality detection means detects a token issuance abnormality, the idle pattern output station sends an idle pattern to the transmission path to connect the transmission path. A ring clearing means for clearing the transmission line; and the ring is configured to clear the transmission line by transmitting the idle pattern from only one station among a plurality of stations connected to the transmission line. type local area network system. (2) The idle pattern output stations determined by the idle pattern output station determining means are two stations, a master and a slave, and the idle pattern output station on the master side sends out an idle pattern, and the idle pattern on the master side 2. The ring type local area network system according to claim 1, wherein the idle pattern output station on the slave side sends out an idle pattern when the output station is abnormal.