JPH07143153A - Ring transmission system - Google Patents

Abstract

PURPOSE:To secure an information path quickly by transferring fault notice information in a direction opposite to a direction in which no packet comes and allowing the station transferring the information to set a transmission line in a direction without a fault to allow a central station to detect fault occurrence instantaneously. CONSTITUTION:A central station 30 is provided with a transmitter 50 and a receiver 60 sending a packet with information set toward one direction of a 2-way transmission line 40 starting from the central station 30 when the 2-way transmission line 40 is normal and receiving the information set to the packet coming from the reverse direction to the transmission direction. When a fault takes place in the two-way transmission line 40 between slave stations 32 and 33, the slave station 33 detects the occurrence of fault because no packet comes from a transmission line 46 and a generated ring alarm is sent to the central station 30 via a transmission line 48 immediately. Furthermore, the slave station 32 detects the occurrence of a fault because no test signal comes from the transmission line 45 to generate the ring alarm. Then the ring alarm is transferred immediately to the central station 30 through the transmission line 43, the slave station 31, and the transmission line 41.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention finds use in computer networks. The present invention is suitable for use in a computer network having a ring-shaped transmission line. In particular, the present invention relates to a technique for securing an information path when a transmission path fails.

[0002]

2. Description of the Related Art In a computer network having a ring-shaped transmission line, a central station controls the entire network, and a plurality of slave stations exchange information with the central station.
In the ring-shaped transmission path having such a configuration, there is known a method of securing an information path by folding back a packet to be sent to the failure transmission path and transmitting it in the reverse direction when a failure occurs in the transmission path.

At this time, the failure detection of the central station is performed by the arrival of the packet from a direction other than the direction in which the packet should be originally received, the failure occurrence information included in the header information of the packet, and the like.

The central station sets a packet transfer direction suitable for the information path at the time of failure, switches to the transfer direction at the time of failure, and continues packet transfer (see Japanese Patent Laid-Open No. 62-42638).

[0005]

SUMMARY OF THE INVENTION In such a system,
The shorter the time from the point of failure occurrence until the central station actually detects the failure occurrence, the more the occurrence of an accident such as packet loss can be prevented.

However, the transmission speed of the packet transmitted between the slave stations is the same during normal operation and when a failure occurs, and until the central station receives the packet returned by the slave station adjacent to the failure occurrence point, The occurrence of the failure cannot be detected. The failure undetected time at the central station increases as the number of slave stations increases.

The present invention has been made against such a background, and provides a ring-shaped transmission system in which the central station can instantly detect the occurrence of a failure in the ring-shaped transmission line and quickly secure an information path. The purpose is to provide.

[0008]

According to the present invention, one central station and a plurality of slave stations are connected by a ring-shaped bidirectional transmission line, and the central station and each slave station are mutually connected to this transmission line. It is a ring-shaped transmission method that includes means for transmitting and receiving packets to perform communication.

Here, a feature of the present invention is that, when the transmission line is normal, the central station carries information in packets in one direction from the central station as a starting point and transmits the packet. However, the central station and the slave stations are provided with means for receiving information carried in a packet arriving from the opposite direction of the transmission direction, and when the received packet does not arrive, the transmission path failure occurs in that direction. Means for determining that the failure has occurred, a means for generating failure notification information having an extremely small number of bits according to the result of the judgment by the judging means, and a means for transmitting the failure notification information in the opposite direction to the direction, A means for immediately transferring the fault notification information when the fault notification information arrives without making a determination,
It is provided with means for transmitting a packet to a transmission line in the direction in which there is no fault when the fault is judged at the own station. The fault notification information preferably includes 1-bit information.

[0010]

When the central station and the slave stations judge the failure of the transmission path due to the arrival of the packet which should not arrive, the central station and the slave station generate failure notification information having an extremely short information amount (for example, 1 bit). At the same time that this fault notification information is transferred in the direction opposite to the direction in which no packet arrives, this station switches and sets the transmission path in the direction in which there is no fault.

When this fault notification information reaches a station whose own station has not determined a fault, this station instantaneously determines that this information is fault notification information and immediately transfers it to the next station.
Since this fault notification information has no header information and has an extremely small number of bits, it can be easily distinguished from a normal packet.

Thus, the central station can detect the occurrence of a failure extremely fast as compared with the normal packet transmission rate. For example, if the normal packet has 80-bit information, and the failure notification information is 1-bit information, it is 8
The fault notification information can reach the central station at 0 times speed.

With this, when a failure occurs in the ring-shaped transmission path, the information path can be secured promptly, and
The transfer direction can be switched immediately when the central office fails.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of the first embodiment of the present invention. FIG. 2 is a block diagram of the transfer control devices included in the central station and the slave stations.

According to the present invention, one central station 30 and three slave stations 31 to 33 are connected in a ring shape by a bidirectional transmission line 40, and the central station 30 and each slave station 31 to 33 respectively perform the bidirectional transmission. This is a ring-shaped transmission system provided with means for transmitting and receiving packets to and from each other on the path 40.

Here, the feature of the present invention is that the central station 30, when the bidirectional transmission line 40 is normal, sends information to the packet toward one direction of the bidirectional transmission line 40 starting from the central station 30. Equipped with a transmitter 50 and a receiver 60 as means for receiving information carried in a packet coming from a direction opposite to the transmission direction. The central station 30 and the slave stations 31 to 33 receive the received packet. As a means for determining that a failure of the bidirectional transmission path 40 has occurred in that direction when it does not occur, the main signal failure detection units 1 and 11 shown in FIG. 2 and the determination results of the main signal failure detection units 1 and 11. According to the above, a ring alarm, which is fault notification information having an extremely small number of bits, is generated, and the ring alarm generation units 2 and 12 are provided as means for transmitting the ring alarm in the direction opposite to the direction. When this ring alarm arrives when the station does not judge the fault, the separation units 3 and 13 are provided as means for immediately transferring the ring alarm, and when the station judges the fault, the station is the starting point and the direction of no fault exists. The transfer control units 6 and 16 and the direction switching units 20 and 21 are provided as means for transmitting packets to the bidirectional transmission path 40. The ring alarm is configured to include 1-bit information. The transfer control device shown in FIG. 2 includes similar devices in the central office 30 and the slave stations 31 to 33. The own station is the central station 30 in the communication mode storage units 5 and 15.
Or the slave stations 31 to 33 are stored in advance, and the central station 30 or the slave stations 31 to 31 are accordingly stored.
This is a configuration for executing the operation of 33.

In the normal state, the header information is extracted from the packet by the separating units 3 and 13. Packets are separated by 3,1
3 is input to the reception control units 7 and 17 and the transfer control units 6 and 16. The header information is input to the communication line reception transfer determination units 4 and 14 and the destination information is extracted. The address information of its own station is stored in the communication mode storage unit 5.

The packet is decoded by the communication packet decoding and transmitting units 8 and 18 via the reception control unit 7, and necessary information is extracted. When there is information to be transmitted by the own station or information addressed to another station, the communication packet decoding and transmitting units 8 and 18 add the information to the packet and the multiplexing unit 9 and
It is input to 19. The information output from the multiplexing units 9 and 19 is transferred in the direction opposite to the packet receiving direction via the direction switching units 20 and 21.

When a failure occurs, the main signal failure detection units 1 and 11
Detects a failure in the bidirectional transmission path 40, and notifies the communication line reception / transfer determination units 4 and 14 to that effect, and also notifies the ring alarm generation units 2 and 12. The communication line reception transfer determination units 4 and 14 instruct the transfer control units 6 and 16 to switch the bidirectional transmission path 40. The ring alarm generation units 2 and 12 generate ring alarms and multiplex units 9 and 1
9 and the direction switching units 20 and 21.

Next, the operation of the first embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a diagram showing the flow of information at the moment of failure occurrence. FIG. 4 is a diagram showing the flow of information after a failure has occurred. During normal operation, as shown in FIG. 1, the packets are transferred in one direction by the transmission paths 42, 44, 46 and 48. In addition, the transmission lines 41, 43, 45, 4
7 is in a rest state during normal operation, but a test signal for detecting a failure is sent between the central station 30 and the slave stations 31 to 33.

As shown in FIG. 3, when a failure occurs in the bidirectional transmission line 40 between the slave station 32 and the slave station 33, the slave station 3
No. 3 detects a failure occurrence because a packet does not arrive from the transmission path 46 and generates a ring alarm. This ring alarm is immediately transferred to the central office 30 by the transmission line 48.

Since the test signal does not arrive from the transmission line 45, the slave station 32 detects a failure occurrence and generates a ring alarm. This ring alarm is immediately transmitted to transmission line 4
3 → Slave station 31 → Transmission line 41 to the central station 30. As a result, the central station 30 can detect the occurrence of a failure. This ring alarm is 1-bit information in the first embodiment of the present invention. A normal packet is about 80 bits of information including header information and data. On the other hand, when there is no other bit in the vicinity and 1-bit information arrives, the central station 30 and the slave stations 31 to 33 identify this as a ring alarm. The transmission rate of this ring alarm is about 80 times that of a normal packet.

The slave station 32 and the slave station 33 which are adjacent to the fault occurrence point have the transmission line 4 in which the test signal does not arrive at the slave station 32.
5, the transmission path 43 in the opposite direction is switched as the information path at the time of failure, and the transmission path 4 in which the packet does not arrive at the slave station 33
The transmission path 48 in the opposite direction to 6 is switched as the information path at the time of failure. These switching is performed by the transfer control unit 6 shown in FIG.
16 and the direction switching units 20 and 21.

As shown in FIG. 4, slave station 32 and slave station 3
When the switching of the information path is completed in 3 and the central station 30 also starts bidirectional packet transmission / reception, a network at the time of failure is configured.

The transfer control device of the first embodiment of the present invention is shown in FIG.
Although the same block configuration is provided bidirectionally as shown in FIG. 2, the communication mode storage units 5 and 15 may be integrated and shared.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a block diagram showing the main part of the transfer control device according to the second embodiment of the present invention. FIG. 5 shows only the failure countermeasure part included in the transfer control device. The transfer control device according to the second embodiment of the present invention includes a downlink signal receiving terminal 71 to which a downlink signal arrives and a downlink signal transmitting terminal 82 to which the downlink signal is transmitted.
And an upstream signal receiving terminal 81 for receiving an upstream signal and an upstream signal transmitting terminal 72 for transmitting the upstream signal. In the second embodiment of the present invention, information is loaded from the upstream signal transmitting terminal 72 into a packet. A receiving unit 73 and a transmitting unit 76 are provided as means for transmitting and receiving the information carried in the packet coming from the upstream signal receiving terminal 81.

The transfer control device comprises a downlink signal receiving terminal 71,
The upstream signal receiving terminal 81, the upstream signal transmitting terminal 72, and the downstream signal transmitting terminal 82 are used to control the central station 30 or the slave stations 31 to 33.
Connected with. The data input to the receiving unit 73 is
The data is stored in the data memory 74 in the order of arrival, and the data memory 74 inputs the data to the transmitting unit 76 according to the instruction of the address control memory 75. The transmitter 76 sends data from the upstream signal transmission terminal 72.

A main signal failure detecting section 77 is provided as means for determining that a failure of the bidirectional transmission line 40 has occurred in that direction when a packet does not arrive from the upstream signal receiving terminal 81. A ring alarm generation unit 78 is used as means for generating a ring alarm, which is fault notification information having an extremely small number of bits, according to the determination result of 77, and transmitting this ring alarm in the direction opposite to the direction.
Then, when a ring alarm arrives when the own station has not determined a failure, the ring alarm detection unit 79 detects this and the own station immediately outputs a ring alarm from the ring alarm generation unit 78 via the upstream signal transmission terminal 72. Send to the next station. When the own station judges a failure, the direction switching unit 80 is provided as a means for transmitting a packet from the station to a transmission path in the direction in which there is no failure. Down signal receiving terminal 7
A test signal from an adjacent station is flowing in 1. This test signal is always received by the receiving unit 73, and when the test signal is disconnected, the occurrence of a failure in the bidirectional transmission line 40 in the down direction is detected. The transmitter 76 also generates and sends a test signal to the downstream bidirectional transmission line 40 of the next station. The information path configuration procedure at the time of failure is similar to that of the first embodiment of the present invention.

[0029]

As described above, according to the present invention, it is possible to instantly detect the occurrence of a failure in the ring-shaped transmission line and secure the information path.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a first embodiment of the present invention.

FIG. 2 is a block configuration diagram of a transfer control device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing the flow of information at the moment of failure occurrence.

FIG. 4 is a diagram showing a flow of information after a failure occurs.

FIG. 5 is a block diagram of a main part of a transfer control device according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 11, 77 Main signal failure detection unit 2, 12, 78 Ring alarm generation unit 3, 13 Separation unit 4, 14 Communication line reception transfer determination unit 5, 15 Communication mode storage unit 6, 16 Transfer control unit 7, 17 Reception Control unit 8, 18 Communication packet decoding transmission unit 9, 19 Multiplexing unit 10 Test signal failure detection unit 20, 21, 80 Direction switching unit 30 Central station 31-33 Slave station 40 Bidirectional transmission line 41-49 Transmission line 50 Transmitter 60 Receiver 71 Downstream signal receiving terminal 72 Upstream signal transmitting terminal 73 Receiving section 74 Data memory 75 Address control memory 76 Transmitting section 79 Ring alarm detecting section 81 Upstream signal receiving terminal 82 Downstream signal transmitting terminal

Claims (2)

[Claims] 1. A central station and a plurality of slave stations are connected to each other in a ring shape by a bidirectional transmission path, and the central station and each slave station communicate with each other by transmitting and receiving packets to and from the transmission path. In the ring-shaped transmission system including means, the central station transmits information by mounting information in a packet toward one direction of the transmission path from the central station as a starting point when the transmission path is normal. The central station and the slave stations are provided with means for receiving information carried in packets arriving from the opposite direction, and when the received packets stop arriving, it is determined that a failure has occurred in the transmission path in that direction. Means and means for generating fault notification information having an extremely small number of bits according to the determination result of this determining means and transmitting the fault notification information in the opposite direction to the direction, and the own station determines the fault. Means for immediately transmitting the failure notification information when the failure notification information arrives, and means for transmitting a packet from the station to a transmission path in the direction in which there is no failure when the failure is judged at the own station. A ring-shaped transmission system characterized by having. 2. The ring-shaped transmission system according to claim 1, wherein the fault notification information includes 1-bit information.