JPH0683239B2 - Loop network communication control method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop network communication control method, and more particularly to a loop network communication control method in which transmission lines are duplicated in consideration of occurrence of a failure.

(Prior art) In addition to the integration of voice communication and data communication, as a communication method for realizing the integration of broadband services such as image communication, for example, "High-speed synchronization" described in 1983 IEICE Exchange Study Group material SE83-107. Loop network described in "Study on formula packet loop".

An access method of such a network will be described.
This loop network consists of one trigger station TS1 and multiple node stations NS as shown in FIG.
Each of these stations of 2, NS3, NS4, NS5, NS6 is transmission line 7
Are connected and configured in a loop. As shown in FIG. 5, the trigger station TS1 transmits a trigger signal TRG (polling signal for polling the highest priority communication) at regular intervals T to start priority polling control for each node station. That is, the trigger station TS1 transmits the trigger signal TRG to poll the communication with the highest priority, and thereafter within this period T, transmits the polling signal POL to sequentially poll the communication with the low priority. . In FIG. 5, following TRG, the highest priority signals S1 and S2 are transmitted, and following the POL, middle and low priority signals S3, S4 and S5 are transmitted.

The conditions for acquiring the transmission right of each node station in this loop network are as follows. That is, each NS acquires the transmission right when it detects the idle state of the loop immediately after passing the signal frame from the upstream. Further, the trigger station also acquires the transmission right according to the above conditions within the period T and transmits the polling signal.

Further, the transmitted signal is removed from the loop at the transmission source station after one loop. Therefore, the station that has acquired the transmission right and transmitted the signal keeps the loop disconnected until the end of the signal frame is detected after the transmission is completed.

FIG. 6 shows a frame structure of a signal transmitted by each of the trigger station TS1 and each node station NS. SD is a start delimiter indicating the start of the signal. CF is a control field that indicates whether or not this signal is a control signal for the trigger signal TRG and polling signal POL. DA and SA indicate the destination address and source address, respectively, and INFO stores the message between nodes. Indicates the information field to be set. Further, after the INFO, an end delimiter ED indicating the end of the signal is added. Explaining the transmission right acquisition control described above in detail, each station
The end delimiter ED of the signal frame shown in the figure is detected, the passage of a certain signal is known, and immediately after ED, the loop is checked for idle state. If it is idle, the transmission right is acquired, and ED To continue to send signals.

After the signal is transmitted, the loop is disconnected and the signal transmitted by itself is removed from the loop until a new end delimiter ED is detected.

(Problems of Prior Art) In a general loop network, transmission lines are duplicated and provided, and when failures occur in the transmission path and the station, these failures are bypassed by loopback control, and signals are transmitted and received.

Also in the present loop network, as shown in FIG. 7, each station is connected by two transmission lines having different transmission directions, that is, a first transmission line 7 and a second transmission line 8 and one of them is used as an active system. As the standby system. When a failure occurs, it is detected immediately and the standby system is constantly powered to recover from the failure.
Sends a control signal, that is, a trigger signal TRG and a polling signal POL to both the active system and the standby system. In a normal state, each node station transmits a signal based on polling control on the transmission path of the active system.

The transmission right acquisition control in the conventional method occurs because the transmission right acquisition control is performed for the duplicated transmission lines by using the same control signal. For example, if a failure occurs at the positions indicated by x in the transmission lines 7 and 8 in FIG. 7, the node stations NS3 and NS4 at both ends of the failure location where the failure is detected are in a loopback state as shown in the figure. Control is performed so that At this time, the control signal transmitted from TS1 to the first transmission line 7 is sent out to the second transmission line 8 at the node station NS3 in the loopback state, and
The control signal transmitted by S1 to the second transmission line 8 is sent to the first transmission line 7 at the node station NS4 in the loopback state. Since these control signals are of the same format, in TS1, the control signals returned to the local station are those received via the node station in the loopback state, or in the normal state. It cannot be judged whether it is the one that has passed around the transmission line. Therefore, TS1 interferes with the polling control cycle in which the transmission right control is performed in the first transmission path 7 and the polling control cycle in which the transmission right control is performed in the first transmission path 7 and interferes with each other normally. Transmission right control cannot be performed.

(Object of the Invention) An object of the present invention is to provide a communication control system in a loop network having a duplicated transmission line, which does not cause contradiction in transmission right acquisition control even when a transmission line failure occurs. is there.

(Structure of the Invention) According to the present invention, one master station and a plurality of slave stations are provided, and each of these stations transmits a signal in a direction opposite to the first transmission path and the second transmission path. In a loop network connected in a loop by a transmission line and in which the main station performs polling control, the main station first connects to the first transmission line.
The control signal added with the end delimiter of
Until the first end delimiter is detected on the first transmission line, the first transmission line is kept in the disconnected state, the control signal to which the second end delimiter is added is transmitted to the second transmission line, and Until the second end delimiter is detected on the second transmission line, the second transmission line is kept in the disconnected state, and the slave station receives the first right when the transmission right to the first transmission line is acquired. Of the second delimiter is added, and the second delimiter is transmitted.
A transmission control method for a loop network is obtained, in which a signal to which the second end delimiter is added is transmitted when the transmission right to the transmission line is acquired.

(Embodiment) In the present invention, as shown in FIG. 1, the trigger station TS1 transmits a first control signal to the first transmission line 7 and transmits a second control signal to the second transmission line 8. Send a control signal.
Here, the control signals are the trigger signal TRG transmitted at every constant period T and the polling signal POL transmitted within the period T. 2A and 2B show the frame structure of the first control signal and the frame structure of the second control signal, respectively. Two
The difference between the two frame configurations lies in the end delimiter. The first control signal is given a first end delimiter ED1 and the second control signal is given a different second end delimiter ED2.

In each NS, the transmission right to the first transmission line 7 is acquired by the first termination delimiter passing through the transmission line 7.
Only when the transmission line 7 is in the idle state immediately after detecting the ED1, the transmission right to the second transmission line 8 is similarly acquired by the second end delimiter passing through the transmission line 8. This is limited to the case where the transmission line 8 is in the idle state immediately after detecting ED2.

Further, in each NS, the signal transmitted to the first transmission line 7 has a frame structure according to FIG. 2 (a), and the signal transmitted to the second transmission line 8 has a frame structure according to FIG. 2 (b). The signal of the configuration.

Therefore, during normal operation of the loop network,
The signal flowing through the first transmission line 7 has a first end delimiter.
Since ED1 is added, the second end delimiter ED2 is added to the signal flowing through the second transmission line 8.

Also, after transmitting the first control signal to the first transmission line 7, TS1 transmits the first end delimiter ED1 via the same transmission line 7.
The transmission line 7 is kept in a disconnected state until the signal is detected, and after the second control signal is transmitted to the second transmission line 8,
The transmission line 8 is kept in the disconnected state until the second end delimiter ED2 is detected via.

Consider a case where a failure occurs in the transmission paths 7 and 8 at the position indicated by the mark X in FIG. 1, and NS3 and NS4 detect the disconnection state of the signal from the upstream and enter the loopback state. In TS1, after transmitting the control signal, NS4 is placed on the first transmission line 7.
The signal on the second transmission line 8 looped back at is received on the second transmission line 8, and the signal on the first transmission line 7 looped back at NS3 is received on the second transmission line 8. Therefore TS1 is the first
Although the second control signal is transmitted to both transmission lines, the first end delimiter ED1 is not detected on the first transmission line 7 after the transmission, and the second control signal is transmitted to the second transmission line 8 as well. End both transmission path for delimiters ED2 is not detected will remain disconnected and removed from all signal loops arriving during this time to TS1.

In other words, in this state, the loop is not configured, but the first
The polling control of the transmission line 7 and the polling control of the second transmission line 8 do not interfere with each other and the signals do not collide with each other.
While a station has acquired the right to transmit and is transmitting a signal, another signal from the upstream does not arrive.

When both transmission lines are disconnected due to the transmission line failure as described above, TS1 performs the following control. Since TS1 cannot form a loop by itself on any of the transmission lines, TS1 suspends control of one of the polling controls on the two transmission lines, and
The two transmission lines are connected to operate as a single transmission line. Specifically, for example, the polling control for the second transmission line 8 is stopped, the transmission line 8 is set to the bypass mode, and the polling control is performed for the first transmission line 7. In this state, the signal transmitted to the first transmission line 7 is looped back once in NS3, but is looped back again in NS4 via the second transmission line 8 in the bypass mode in TS1 to It will be returned to TS1 via the transmission line 7 of. Therefore, TS1 can normally perform polling control on the first transmission line 7, and instructs each NS to perform transmission based on the polling control on the first transmission line.

Further, as shown in FIG. 3, consider a case where a failure occurs at the position indicated by X on the first transmission line 7 and NS4 detects the disconnection of the signal from the upstream and enters the loopback state.

In this state, TS1 receives the signal on the second transmission line 8 looped back by NS4 on the first transmission line 7,
The first end delimiter ED1 is not detected on the same transmission line 7. Therefore, the first transmission line 7 remains disconnected in TS1 after the TS1 transmits the control signal, and all signals arriving at TS1 during this period are removed from the loop. Meanwhile, the second
The transmission line 8 of is a loop, and TS1 is the same transmission line 8
Normal polling control can be performed for each
The NS is instructed to perform transmission based on the polling control of the second transmission line 8.

In the above embodiment, the present invention is applied to the loop network in which TS1 transmits the trigger signal TRG at every constant period T to perform polling control. In this case, if a transmission path failure occurs, TS1 cannot acquire the transmission right for transmitting the next polling signal POL because the end delimiter ED is not detected after TRG transmission, but the transmission right is inevitably acquired at the beginning of the new cycle T. It is possible to perform transmission for failure recovery.

Next, a case where the present invention is applied to a loop network in which TS1 does not necessarily start polling control at every constant period T will be described. In this case, if a transmission path failure occurs, TS1 polls the highest priority transmission as described above.
After sending, I cannot get the right to send. If the transmission right cannot be acquired for a certain period of time, TS1 considers that a transmission path failure has occurred, and performs communication for failure recovery without acquiring the transmission right based on the detection of the end delimiter ED. In this way, when a failure occurs, the failure recovery time can be shortened by allowing only TS1 to transmit without acquiring the transmission right.

[Brief description of drawings]

1 and 3 are diagrams showing a loop network showing an embodiment of the present invention, FIG. 2 is a diagram showing a configuration of a signal frame according to the present invention, FIG. 4 is a diagram showing a configuration of a loop network, and FIG. FIG. 5 is a diagram showing a signal flow on the loop, FIG. 6 is a diagram showing a configuration of a signal frame, and FIG. 7 is a diagram showing a configuration of a duplicated loop network. In the figure, 1 is a trigger station TS1, 2, 3, 4, 5, 6
Indicates a node station NS, and 7 and 8 indicate transmission lines.

Claims (1)

[Claims] 1. A master station and a plurality of slave stations, each station forming a loop by a first transmission line and a second transmission line for transmitting a signal in a direction opposite to the first transmission line. In a loop network which is connected and in which the main station performs polling control, the main station transmits a control signal with a first end delimiter added to the first transmission line, and the main station transmits the control signal to the first transmission line. The first transmission path is kept in the disconnected state until the end delimiter of 1 is detected, a control signal to which the second end delimiter is added is transmitted to the second transmission path, and the control signal is transmitted on the second transmission path. Until the second end delimiter is detected, the second transmission line is kept in the disconnected state, and the slave station is
When the transmission right to the first transmission path is acquired, the first
And a signal with the second delimiter added thereto is transmitted, and when the right to transmit to the second transmission path is acquired, the signal with the second end delimiter is transmitted. .