JPH0998180A - Fault avoid control method for ring network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically generate a route table for avoiding faults in a short time without necessity to take a lot of measures when any communication fault is generated on a network. SOLUTION: Respective nodes N1-N6 send APS(communication fault point signal) data in clock-wise direction a1-a6 and counter-clock-wise direction b1-b6 according to an APS protocol for automatically relieving a main signal when a fault A is generated on the network. When the node N2 detects the interruption of the main signal from the adjacent node N3, the node N2 sends the fault point specification APS data having priority higher than usual and specifying the position of the fault in the clock-wise and counter-clock-wise directions. The node, that receives the APS data, sends the fault point specification APS data in the clock-wise and counter-clock-wise directions and based on the fault point specification data, the route table is updated so as to avoid the fault point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional line switch / ring network system, and more particularly to a method of controlling a route table so as to avoid a failure when the failure occurs.

[0002]

2. Description of the Related Art In a ring network system in which a plurality of nodes are connected in a ring shape and two-way communication is possible, a route table is provided in each node, and a received signal is rotated clockwise (CW) or by referring to this route table. It determines which route, counterclockwise (CCW), should be sent. Route table creation control is RIP
(Routing Information Prot
Ocol). If there is no big difference in transmission time between nodes, the communication time depends on the processing time in the node station.
It is desirable to reach the destination node with as few hops as possible (the number of inter-node transmission paths). Therefore, the route table of each node registers the shortest route to the other node, that is, the route with the minimum number of hops in its own route table.

In the RIP system, a route table is created by broadcasting RIP packets at predetermined time intervals. Therefore, when a node does not receive a RIP packet from a neighboring node even after a predetermined time has passed, it is determined that a failure has occurred in the communication path between them, and the own station should avoid this failure point. Update the route table. Similarly, the route table is broadcast sequentially, and the route table is updated sequentially at each node, so that the entire network uses a route that avoids a point of failure. If it occurs, if the route of the specific network communication is a route passing through the failure point, it is necessary to redetermine the route avoiding the failure point.

[0004]

However, in the conventional route table control, when a transmission line failure occurs at a certain place on the network, the route table is created when the route table information is not transmitted from the adjacent node. Since the change control is performed, there is a delay from the occurrence of the transmission path failure to the recognition of the failure.
In addition, when updating the route table, change the route table to an appropriate setting on all nodes of the network to start the route table change control of the own station after receiving the updated route table information from the adjacent node. It takes a lot of time before it is done. This route table update time increases in proportion to the number of nodes that make up the network.

Although it is possible to shorten the route table update time by shortening the time interval of RIP packet transmission, this is not a desirable solution because the processing load of the processor of each node or the monitoring system becomes large during normal operation.

An object of the present invention is to provide a communication control method capable of promptly executing search for an optimum route in a ring network.

Another object of the present invention is to provide a failure avoidance control method capable of immediately updating the route table so as to avoid the failure points in all the nodes constituting the ring network.

[0008]

According to a failure avoidance control method of the present invention, in a bidirectional line switch ring network system in which each node has a route table, each node automatically operates when a failure occurs in the network. When A node detects a main signal disconnection from an adjacent node by transmitting APS data in a clockwise direction and a counterclockwise direction in accordance with a main signal rescue protocol (APS protocol) for repairing a main signal, The failure point specifying APS data having a higher priority than the normal time and specifying the failure position is transmitted in the clockwise direction and the counterclockwise direction, and the other node receiving the failure point specifying APS data transmits the failure point specifying APS data. It transmits in the clockwise direction and the counterclockwise direction, and avoids the failure point based on the failure point identification APS data. The route table is updated so that

When a transmission path failure occurs on the network, each node automatically identifies the failure point upon reception of APS data used to rescue the main signal communication, and determines the optimum point. Determine the communication route. APS
By using the protocol, the route table can be automatically updated to the failure point avoidance setting in a short time.

[0010]

1 is a schematic block diagram showing an example of a ring network system for implementing a route table control method according to the present invention. For convenience of explanation, it is assumed that this ring network system is composed of 6 nodes. An address (target ID) used in network communication and a specific number (NODE_ID) used in the automatic main signal rescue protocol (APS protocol) are associated and given to each node. For example, the target ID of the node N1 is "NODE1", and the NODE_ID of the APS protocol is "N1". In this ring network, APS data transmitted clockwise (CW) from each node is indicated by "a", and APS data transmitted counterclockwise (CCW) is indicated by "b". For example, node N1
The data sent from the CW to CW is a1 and CCW
The data transmitted in the direction is "b1".

FIG. 2 is a schematic block diagram showing the internal structure of each node. Each node has two-way communication circuits 101 and 102 for performing two-way communication of CW and CCW,
It comprises a route table memory 103, a node control unit 104 for controlling the operation of the entire node, and other circuits (memory, terminal interface, etc.) not shown.

Upon receiving the data packet from the adjacent node, the node controller 104 first checks the destination. If it is a packet addressed to its own station, the packet data is fetched and processed, and if it is a packet addressed to another station, it is passed through the bidirectional communication circuits 101 and 102.

When the APS data is received, the node control unit 104, as will be described later, has an APS byte (K1, K1).
2) is checked, and when a failure occurs in the ring network, the route table 103 is updated. When the route table 103 is updated, the default route table is saved and the copy is controlled to be updated. Therefore, although not shown, a memory area for storing the updated route table is secured in the route table memory 103. Of course, it may be stored in a separate memory. Also, the node control unit 10
When detecting a network failure due to a signal disconnection from an adjacent node, 4 generates APS data specifying the failure position and sends it out in both directions by the bidirectional communication circuits 101 and 102.

(Normal network) FIG. 3 is a schematic diagram showing the contents of the inter-node APS data when the network is normal, and FIG. 4 is a schematic diagram showing the contents of the route table of the node N1 when the network is normal. is there.

As shown in FIG. 3, during normal operation, APS data a1 to CW in the ring network shown in FIG.
a6 and CCW direction APS data b1 to b6 are transferred between the respective nodes. APS data is APS
It consists of K1 bytes and K2 bytes called bytes.
The K1 byte is composed of a "CONDITION" field indicating the request level and a "DESTINATION NODE_ID" field indicating the destination node, and the K2 byte is "S" indicating the source.
It is composed of OURCE NODE_ID. Under normal conditions, K1 byte "CONDITION" is set to "NR (No Request)". For example, in the APS data a1 transmitted from the node N1 in the CW direction, the transmission source is the node N1 and the transmission destination is the node N2. Also, the APS transmitted in the CCW direction
The source of the data b1 is also the node N1 and the destination thereof is the node N6. APS data is also sent to both nodes in both directions as shown in FIG.

In such a state that no failure has occurred, the route table memory 103 stores the default contents shown in FIG. This default route table is created based on the node chain information (information indicating the node connection order) used in the APS protocol. The route table includes fields of NODE_ID used in the APS protocol, the number of hops in the CW direction, a use flag indicating whether the route can be used in the CW direction, the number of hops in the CCW direction, and a use flag showing whether the route can be used in the CCW direction. Composed. The number of hops corresponds to the number of transmission lines from the local node to the target node when using that route. For the same target node,
The direction with the smaller number of hops indicates the shortest route. Therefore, in the normal state, the use flag in the direction having a smaller number of hops is “use (U)”, and the use flag in the opposite direction is “use prohibited (N)”. However, when the number of hops is the same, the direction to be used may be uniquely determined by a predetermined algorithm. Here, when the number of hops is the same, a route in the CW direction is adopted (see target NODE 4 in the figure).

(At the time of network failure) As shown in FIG. 1, it is assumed that a failure A occurs in the transmission line between the node N2 and the node N3. At this time, since the node N2 cannot receive the main signal from the node N3, it is determined that a failure has occurred in the transmission path on the way. Node N2 is AP
Set the K1 byte "CONDITION" field of S to SFR (Sig
nal failure ring), and further, the node N3 in the direction in which the failure has occurred is designated by the destination NODE_ID field of K2 bytes. And K1 of APS which shows this obstacle
/ K2 byte data is transmitted in the CW and CCW directions. Similarly, the node N3 also has "CONDI" of APS K1 byte.
The TION "field is set to SFR (Signal Failure Ring), and the node N2 in the direction in which the failure has occurred is specified in the destination NODE_ID field. Then, the K1 / K2 byte data of the APS indicating this failure is in the CW direction and CCW. Send in the direction.

FIG. 5 is a schematic diagram showing the contents of the inter-node APS data when a network failure occurs. Node N2
The APS K1 / K2 byte data a2 and b2 sent from the node N3 in both directions are both SFR / N3 / N2, and the APS K1 / K2 byte data a3 and b3 sent from the node N3 in both directions are both SFR /. N2 / N3. APs whose "CONDITION" field is "SFR"
Since the S data has a higher priority than the APS data of "NR", the APS data of "NR" sent by the other nodes N1, N4-N6 is ignored and the A data of "SFR" is ignored.
PS data is captured at each node of the ring network and transmitted in both directions. More specifically, at each node, the APS data received from the CW direction is C
APS sent in CW direction and received in CCW direction
Data is sent in the CW direction. For example, the APS data b2 received by the node N1 from the node N2 is sent to the node N6 as the APS data b1 as it is, and the direction is reversed and sent to the node N2 as the APS data a1. Following the same procedure, K of APS shown in FIG.
1 / K2 byte data is sent out from each node in both directions. In this way, when it is known that the K1 / K2 byte data of "SFR" causes a failure in the transmission path between the node 2 and the node 3, each node updates the route table so as to avoid the failure point A. To do. Since the main signal rescue switch time of the APS protocol is 60 msec (standard value), each node can start the route table update control much faster than the RIP method.

FIG. 6 is a schematic diagram showing a change in the contents of the route table of the node N1 when a failure occurs. As described above, the direction (route) with a small number of hops is normally selected, but when a failure occurs between the node N2 and the node N3, the route is changed so as to avoid the failure point A. That is, each node has an AP indicating the failure point A.
When the K1 / K2 byte data of S is received, the location of the fault point A is specified by referring to the destination node and the source node. Then, the use flags in the CW direction and CCW direction of the route table are changed so as to avoid the failure point A.

For example, when the node N1 attempts to transmit data by using the node N3 as a target node, normally, a route in the CW direction is selected due to the number of hops and communication is performed via the node N2. However, when the fault point A exists, the route in the CW direction cannot be used. Therefore, the use flag of the target node N3 in the CW direction is changed from "U" to "F (Fail)", and this route is disconnected. However, since the CCW direction route, that is, the route passing through the nodes N6, N5, and N4 is usable, the CCW direction use flag is changed from “N” to “U”. The route table is updated in the same manner in the other nodes, and communication is performed with a new route avoiding the failure point A.

When the failure on the ring network is recovered, the APS data is returned to the normal state, so that the route table of each node is also returned to the normal state, that is, the default route table. Since the default route table is stored in the route table memory 103, it is possible to instantly switch from a failure time to a normal time.

[0022]

As described above in detail, in the route table control method according to the present invention, the time required for creating / changing the route table of all nodes is significantly shortened as compared with the conventional method. Further, since the default route table is stored, it is possible to immediately return to the normal state route table upon failure recovery.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an example of a ring network system for implementing a route table control method according to the present invention.

FIG. 2 is a schematic block diagram showing an internal configuration of each node.

FIG. 3 AP between nodes when the network is normal
It is a schematic diagram which shows the content of S data.

FIG. 4 is a schematic diagram showing contents of a route table of a node N1 when the network is normal.

FIG. 5 is a schematic diagram showing contents of inter-node APS data when a network failure occurs.

FIG. 6 is a schematic diagram showing changes in the contents of the route table of the node N1 when a failure occurs.

[Explanation of symbols]

 A transmission line fault point N1 to N6 nodes a1 to a6 clockwise APS data b1 to b6 counterclockwise APS data 101 bidirectional communication circuit 102 bidirectional communication circuit 103 route table 104 node control unit

Claims (6)

[Claims] 1. In a bidirectional line switch type ring network system in which each node has a route table, each node automatically relieves a main signal when a failure occurs on the network. According to (APS protocol), the APS data is transmitted in the clockwise direction and the counterclockwise direction, and when the first node detects the main signal disconnection from the adjacent node,
The first node sends fault point specifying APS data having a higher priority than normal time and specifying a fault position in the clockwise direction and the counterclockwise direction, and the second node receiving the fault point specifying APS data,
Transmitting the fault point specifying APS data in a clockwise direction and a counterclockwise direction, and updating the route table so as to avoid the fault point based on the fault point specifying APS data. Failure avoidance control method. 2. The APS data includes first data including a status field indicating a signal state and a transmission destination field indicating a transmission destination node, and second data including a transmission source field indicating a transmission source node. The fault avoidance control method according to claim 1, wherein 3. The fault avoidance control method according to claim 1, wherein the APS data has a priority set in advance according to the data of the status field. 4. Each of the nodes sets the route table as a usable route in either a clockwise direction or a counterclockwise direction, whichever direction has a smaller number of hops when normal, and identifies the failure point when the failure occurs. 4. The usable route that passes through a failure point specified based on APS data is changed to an unusable route, and a route around the opposite route is changed to an usable route. The fault avoidance control method described in. 5. A normal first route table is stored in a first memory, and when the failure occurs, the first route table is copied to create a second route table, based on the failure point specifying APS data. 6. The failure avoidance control method according to claim 1, further comprising: updating the second route table. 6. The fault avoidance control according to claim 5, wherein each node, when receiving normal APS data, performs route control using the first route table stored in the first memory. Method.