WO2010116465A1 - Ring node device, multi-ring network system, and route switching method - Google Patents

Abstract

Provided is a ring node device functioning as a pair node of a multi-ring network system for relaying as relay data, data transmitted and received via a relay rink of one set of pair nodes between different ring networks. The ring node device includes an RPR ring interface reception unit (13) and a protection unit (14). The RPR ring interface reception unit (13) transmits relay data received from the local ring network to a relay link connected to the local device and transmits a control frame indicating a state of a relay link to the other pair node connected by the relay link. When it is judged that the relay link has failed according to the control frame received via the relay link from the other pair node, the protection unit (14) instructs the RPR ring interface reception unit (13) so as to transmit a control frame reporting the failure to the other pair node and performs a communication route switching process.

Description

Ring node device, multi-ring network system, and path switching method

The present invention relates to a ring node device and a multi-ring network system that switch communication paths when a failure occurs in a ring network.

Conventionally, in a ring network configuration method, a method of switching a route when a failure occurs is used as follows. In this method, a bidirectional double ring is configured, and each ring node advertises its physical address on the ring. Each ring node collects the advertisement information and arranges the order of nodes (topology map). Recognize (topology map creation function) and refer to the topology map when transmitting a packet on the ring, and select and transmit the ring of the system close to the physical address of the destination. In addition, each node periodically transmits failure information and constantly monitors the failure information, thereby quickly detecting the failure location on the ring and switching the route (failure bypass function and protection function when a ring failure occurs) Have An example of such a method is described in Non-Patent Document 1 below, for example.

Further, as a ring network configuration method, for example, there is another method described in Non-Patent Document 2 below. In this system, a bidirectional double ring is configured, and an Ethernet (registered trademark) ring protocol based on master-slave control in which each node operates by sharing with a master node and a slave node is used. The master node avoids a loop by setting one of the ports as a BP (Blocking Port) and discarding the BP transmission / reception traffic. Each node monitors the link failure of the adjacent node, the failure detection node sets the failure port to BP, and then the master node that receives the failure information cancels the BP setting of its own node, The communication path is switched by notifying the flash instruction (failure bypass function and protection function when a ring failure occurs). Examples of such methods include, for example, fault detection using the Ethernet (registered trademark) OAM (Operation Administration and Maintenance) mechanism described in Non-Patent Document 2 below and Ethernet described in Non-Patent Document 3 below. There is an Ethernet (registered trademark) ring that applies both ring protection switching to which (registered trademark) OAM is applied.

On the other hand, Non-Patent Documents 1 to 3 described above do not describe a communication system using a multi-ring that connects a plurality of rings. As a prior art of a communication method for multi-ring, there is STP (Spanning Tree Protocol) described in Non-Patent Document 4 below. In the STP, a redundant ring network is logically made into a tree structure, thereby eliminating a loop portion and generating one forwarding path (communication path). The forwarding path is generated in response to changes in the network configuration. The synchronization of the STP information of each bridge is guaranteed by a protocol timer. Give priority (priority) to each bridge, give cost to each link, select the bridge with the highest priority as the root bridge, and select the route with the lowest cost from the root bridge as the starting point of the tree structure And construct a tree.

However, when implementing the multi-ring method for large-scale networks, etc., the conventional multi-ring STP sets a Max Age time, and a failure occurs if the BPDU (bridge protocol data unit) does not arrive within the Max Age time. Recognize. Therefore, it is necessary to wait until the Max Age time elapses from the time when the communication path is divided due to the occurrence of a failure until the determination of another path. For this reason, there is a problem that it takes time from the occurrence of a failure to the recovery of communication.

The present invention has been made in view of the above, and an object of the present invention is to provide a ring node device, a multi-ring network system, and a path switching method that can shorten the time from failure occurrence to communication recovery in a multi-ring network. And

In order to solve the above-described problems and achieve the object, the present invention includes a plurality of ring networks, and at least one of the ring node devices constituting the ring network is a pair node. In a multi-ring network system that relays data transmitted / received via a relay link that is a link connecting a pair of pair nodes as relay data, the ring node device that functions as the pair node, and to which the own device belongs A ring interface receiving means for transmitting the relay data received from the network to the relay link to which the own device is connected, and transmitting a control frame indicating the state of the relay link to the other pair node connected by the relay link; Received from the relay link to which the Based on the control interface received from the other pair node via the relay link to which the own device is connected, and the ring interface transmitting means for transmitting the data to the other ring node device in the ring network to which the own device belongs. Monitors whether or not a failure has occurred in the relay link, and if a failure has occurred in the relay link, instructs the ring interface reception means to transmit a control frame to that effect to the other pair node And a protection means for performing a predetermined communication path switching process, wherein the ring interface receiving means transmits a control frame based on the instruction.

The ring node device, the multi-ring network system, and the path switching method according to the present invention provide a failure of a pair node in which pair nodes connected to a relay link connecting ring networks connect to the relay link and the relay link using a control frame. Since the situation is notified, there is an effect that the time from the occurrence of the failure to the communication recovery can be shortened.

FIG. 1 is a diagram illustrating a functional configuration example of a first embodiment of an RPR ring node device according to the present invention. FIG. 2 is a diagram illustrating a configuration example of the multi-ring network system according to the first embodiment. FIG. 3 is a network configuration diagram for explaining an operation example of the first embodiment at the normal time. FIG. 4 is a diagram illustrating an example of an operation when a failure occurs in a relay link in use. FIG. 5 is a diagram illustrating an example of an operation when a failure occurs in a pair node connected to a relay link in use. FIG. 6 is a diagram illustrating an example of an operation in the case where a link break has occurred in two paths that can reach a pair node in use. FIG. 7 is a diagram illustrating an example of a network configuration when there is one relay link. FIG. 8 is a diagram illustrating a functional configuration example of the ring node device according to the second embodiment. FIG. 9 is a diagram illustrating a configuration example of the multi-ring network system according to the second embodiment. FIG. 10 is a network configuration diagram for explaining an example of normal operation. FIG. 11 is a diagram illustrating an example of an operation when a failure occurs in a relay link in use. FIG. 12 is a diagram illustrating an example of an operation when a failure occurs in a pair node connected to a relay link in use. FIG. 13 is a diagram illustrating an example of an operation in a case where a link break has occurred in two paths that can reach a pair node in use.

Explanation of symbols

1,1-1 to 1-8 RPR ring node device 2,3,121,122 Network 4,123 West relay link 5,124 East relay link 6,125 Inner ring 7,126 Outer ring 8-1,8-2 Terminal 11, 101 Concentration SW unit 12 RPR interface transmission unit 13 RPR interface reception unit 14, 104 Protection unit 15 Topology management unit 16, 106 Outer ring reception unit 17, 107 Outer ring drop determination unit 18, 108 Outer ring transmission unit 19, 109 Inner ring transmission unit 20, 110 Inner ring drop determination unit 21, 111 Inner ring reception unit 22, 112 Control frame determination unit 23, 113 Relay link port 24, 114 Other port 100, 100-1 to 100-8 OAM ring node Device 10 OAM interface transmission unit 103 OAM interface reception unit 105 BP setting unit 130 BP

Hereinafter, embodiments of a ring node device, a multi-ring network system, and a path switching method according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a functional configuration example of a first embodiment of an RPR ring node device according to the present invention. As shown in FIG. 1, an RPR ring node device 1 according to the present embodiment is a device that functions as an RPR ring node, and includes a line switch (SW) unit 11, an RPR interface transmission unit 12, an RPR interface reception unit 13, protection. Unit 14, topology management unit 15, outer ring receiving unit 16, outer ring drop determining unit 17, outer ring transmitting unit 18, inner ring transmitting unit 19, inner ring drop determining unit 20, inner ring receiving unit 21, control frame determining unit 22. Further, the RPR ring node device 1 includes a relay link port 23 and another port 24 that is a port other than the relay link port 23.

FIG. 2 is a diagram illustrating a configuration example of the multi-ring network system according to the present embodiment. As shown in FIG. 2, the multi-ring network system according to the present embodiment includes RPR ring nodes 1-1 to 1-8, and network 2 in which RPR ring node devices 1-1 to 1-4 are ring node networks. RPR ring node devices 1-5 to 1-8 constitute a network 3 that is a ring node network. RPR ring node apparatuses 1-1 to 1-8 each have the same configuration as the RPR ring node apparatus shown in FIG. Further, the RPR ring node device 1-2 and the RPR ring node device 1-6 are set as a West pair node, and the RPR ring node device 1-3 and the RPR ring node device 1-7 are set as an East pair node. The two ring networks 2 and 3 are connected by two links, a West relay link 4 that connects the West pair nodes and an East relay link 5 that connects the East pair nodes. In addition, the network 2 and the network 3 have two-way rings, an inner ring 6 and an outer ring 7.

Returning to FIG. 1, the function of the RPR ring node 1 will be described. The relay link port 23 is an input / output port for a frame from a relay link that connects between ring node networks, such as the West relay link 4 and the East relay link 5 in FIG. The line concentrator 11 receives a MAC frame of a MAC (Media Access Control) frame input from the relay link port 23 or the other port 24, transmits a frame output to the relay link port 23 or the other port 24, Switching.

The RPR interface transmission unit 12 generates an RPR data frame by adding an RPR header to the MAC frame received via the line concentration switch unit 11, or topology information acquired from the topology management unit 15 and the protection unit 14 for the received MAC frame. RPR control frame to which the protection information obtained from is added is generated, and it is selected whether to add to the inner ring 6 or the outer ring 7 or both based on the topology information and the protection information, and based on the selection result The generated frame is output to one or both of the outer ring transmitter 18 and the inner ring transmitter 19. Further, the RPR interface transmission unit 12 sets later-described multi-ring information acquired from the protection unit 14 in the RPR control frame, and outputs it to one or both of the outer ring transmission unit 18 and the inner ring transmission unit 19.

The RPR interface receiving unit 13 identifies whether the frame is an RPR data frame or an RPR control frame based on the RPR frame received from the inner ring 6 or the outer ring 7. Further, the RPR interface receiving unit 13 extracts predetermined information necessary for the processing of the protection unit 14 and the topology management unit 15 from the received RPR frame, and the extracted information is respectively protected by the protection unit 14 and the topology management unit 15. Notify Further, the RPR interface reception unit 13 extracts a MAC frame from the received RPR data frame, and delivers the extracted MAC frame to the line concentration switch unit 11. Further, the RPR interface reception unit 13 sets the multi-ring information acquired from the protection unit 14 in the received RPR control frame, and outputs the set RPR control frame to the relay link via the line concentration switch unit 11.

The protection unit 14 grasps the failure status on the ring in the same manner as a protection function in a general ring network described later, and notifies the topology management unit 15 and the RPR interface transmission unit 12 of the failure information as protection information. Further, the protection unit 14 receives the control frame received from the relay link port 23 from the control frame determination unit 22, monitors the relay link based on the control frame, detects a failure of the relay link, and the topology management unit 15, based on the topology information and the failure detection result acquired from 15, another pair node in the own ring network (for example, if it is an East pair node in the network 2 of FIG. 2, that is, the RPR link node device 1-3, A failure of the RPR link node device 1-2), which is the West pad in the network 2, and a route failure to the pair node are detected. Then, the RPR interface transmitter 12 and the RPR interface receiver 13 are notified of the detection results of the relay link failure and the pair node failure as multi-ring information. If a control frame does not arrive after a predetermined time from the relay link port 23, it is determined that a failure has occurred in the relay link to which the device is connected, and another usable relay link is selected. The RPR interface reception unit 13 is notified of the information included in the multi-ring information.

The topology management unit 15 stores the number of HOPs to each destination RPR ring node device on its own ring network as a table and manages it as topology information. The outer ring receiving unit 16 checks whether there is an error in the frame received from the outer ring 7, and outputs the received frame after the check to the outer ring drop determination unit 17. The inner ring reception unit 21 checks whether there is an error in the frame received from the inner ring 6 and outputs the received frame after the check to the inner ring drop determination unit 20.

The outer ring drop determination unit 17 determines whether the received frame received via the outer ring reception unit 16 is to be relayed or dropped (discarded), and outputs the received frame to the outer ring transmission unit 18 if not dropped. To do. The inner ring drop determination unit 20 determines whether to relay or drop the reception frame received via the inner ring reception unit 21, and outputs the reception frame to the inner ring transmission unit 19 when not dropping.

The outer ring transmitter 18 schedules both the traffic of the frame Add received from the RPR interface transmitter 12 and the transit of the received frame Transit, and based on the scheduling result, the received frame received from the outer ring drop determiner 17 and the RPR The frame received from the interface transmitter 12 is transmitted to the outer ring 7. The inner ring transmission unit 19 schedules both the traffic of the frame Add received from the RPR interface transmission unit 12 and the transit of the reception frame Transit, and based on the scheduling result, the received frame received from the inner ring drop determination unit 20 and the RPR The frame received from the interface transmitter 12 is transmitted to the inner ring 6.

The control frame determination unit 22 determines whether the frame received from the relay link port 23 via the line collection switch unit 11 is a control frame. Then, in the case of a control frame, the control frame determination unit 22 extracts predetermined necessary information from the frame, notifies the protection unit 14 of the extraction result, and discards the frame without sending it to the RPR interface transmission unit 12. In addition, if the frame is not a control frame, the control frame determination unit 22 sends the frame to the RPR interface transmission unit 12.

In addition, although operation | movement when the RPR ring node apparatus 1 is a pair node (for example, a West pair node, an East pair node etc.) connected to a relay link was demonstrated here, in the case of a node other than that, the above-mentioned function is demonstrated. Of these, the processing for frames transmitted and received via the relay link is not performed.

In the present embodiment, the concentrator switch unit 11 is provided. However, even if the concentrator switch unit 11 is not provided, the present embodiment can be implemented by performing a change depending on the interface type of the relay link port as necessary. A similar operation can be realized with a configuration similar to that of the first embodiment.

Here, a general RPR operation will be described.
(1) Understanding the node order Understanding the order in which nodes are connected, and constructing a topology map at each node. Each node transmits a control frame called a TP (Topology and Protection) frame to both rings (upstream direction and downstream direction) at a constant cycle, and the initial value is 255. By using Time To Alive), each node grasps the position of the TP frame transmission node (the number of relays of the node) viewed from each node and creates a topology map (topology map creation function). The TP frame is relayed by simply subtracting TTL at a node other than the transmission node, and finally terminated at the transmission node (the transmission node discards itself).

(2) Detection of a ring failure between adjacent nodes and public information When each node transmits the TP frame to both rings, the KeepAlive frame from the immediate upstream node (upstream adjacent node) and its own node reception failure Detecting a failure (link failure information) between the link from the immediately upstream node to the own node by detecting (the node cannot receive any frame other than the KeepAlive frame from the immediately upstream node) ( Ring failure detection function). Whether or not the transmission source of the KeepAlive frame is the immediate upstream node is determined based on the topology map created in (1). This link failure status information with the immediately upstream node is sent on the TP frame, and all receiving nodes including the immediately downstream node (adjacent node in the downstream direction) grasp the received link status of the TP frame source node. Map which links on the ring are in a failed state.

(3) Switching of RPR data frame transmission direction Normally, each node reaches the destination node based on the topology map created in (1) and the link failure information detected in (2). And a RPR data frame is transmitted by selecting a ring in which there are few ring faults (protection function).

In the present embodiment, the above operations (1) to (3) are applied in one ring network. Specifically, the topology management unit 15 has the above-described topology map creation function, creates a topology map, and holds it as topology information. Further, the protection unit 14 detects the link failure (2), and uses the detected information as protection information. Then, the interface transmission unit 12 performs the above selection (3).

In the present embodiment, the RPR ring node device 1 adds to the above-described operation in the normal ring network, as described below, a relay link that connects the ring networks (in the example of FIG. 2, the West relay link 4, The monitoring of the East relay link 5) and the failure notification process are performed according to the following procedures (a) to (e).

(A) Each pair node (for example, the West pair node and the East pair node in FIG. 2) transmits a control frame to the relay link to which the own device is connected to monitor the connectivity of the relay link, and also displays the monitoring result in the control frame. And send to each other.
(B) Each pair node monitors whether a failure has occurred in the pair node of its own ring network by the ring failure detection function and the protection function based on the topology map.
(C) Each pair node transmits multi-ring information (monitoring information (a) and (b)) used for determination of a relay link failure on the RPR control frame to the ring.
(D) If each node detects a relay link failure, or if it detects a failure of a relay link to which it is connected based on the RPR control frame received from the other pair node, each pair node is connected Performs failure detection based on whether control frames can be received via the relay link (failure detection based on whether control frames can be received within a predetermined time), and determines that there is a failure in the relay link to which the device is connected If the relay link is a relay link that is in use, another relay link that can be used as a candidate for the switching destination relay link is selected.
(E) Each pair node sets the selected relay link in the control frame and transmits it to the relay link to which the own device is connected. Each pair node recognizes that the relay link included in the received control frame is recognized by the own device. If it matches the available relay link information and the relay link is a link to which the local device is connected, it is assumed that the relay link is up (can be used), and the data frame To the relay link.

In the configuration example of FIG. 1, the protection unit 14 performs monitoring of the above (a), (b), and (d), the RPR interface transmission unit 12 performs (c), and the protection unit 14 and the RPR The interface receiver 13 performs (e).

Next, the operation of the present embodiment in each communication state will be described. FIG. 3 is a network configuration diagram illustrating an example of normal operation. The configuration of the network system in FIG. 3 is the same as that in FIG. 2, and a terminal 8-1 is connected to the RPR ring node device 1-5, and a terminal 8-2 is connected to the RPR ring node device 1-4. ing. In such a configuration, when the terminal 8-1 and the terminal 8-2 perform communication, it is necessary to transmit and receive data between networks using a relay link connecting the network 2 and the network 3.

In this configuration, there are two relay links, but when normal (no failure has occurred), there are a plurality of usable relay links (West relay link 4 and East relay link 5). A relay link to be used (relay link used for data frame transmission) may be used. Since any method may be used for selecting which relay link to use as a relay link in a normal state, it is not particularly described here. In FIG. 3, the relay link using the East relay link 5 is used.

Each pair node (the RPR ring node devices 1-2 and 1-6 that are the West pair nodes and the RPR ring node devices 1-3 and 1-7 that are the East pair nodes) receives the multi-ring information and the protection information grasped by itself. The control frame is transmitted to the own ring network (step S1), and the control frame including the monitoring information of the multi-ring information and the protection information relay link is mutually notified (step S2). Also, a pair node (RPR ring node devices 1-3, 1-7) having a relay link currently in use transfers data frames to an adjacent ring network (for example, network 3 for the RPR ring node device 1-3). (Step S3), the other pair node (RPR ring node device 1-2, 1-6) discards the data frame without transferring it to the relay link (Step S4).

Next, a case where a failure occurs will be described. FIG. 4 is a diagram illustrating an example of an operation when a failure occurs in a relay link in use. In the example of FIG. 4, it is assumed that a failure has occurred in the East relay link 5 in use due to disconnection or the like in the network system similar to FIG. First, the East pair node (RPR ring node devices 1-3, 1-7) detects a failure (Signal Fail) by not receiving a control frame from the relay link to which the East pair node is connected for a predetermined time or more (step S11). ).

The East pair node adds the relay link failure information detected in step S11 to the RPR control frame and notifies the ring network 3 of the outer or inner ring (step S12). The other pair node (the West pair node in each network) that has received the control frame including the relay link failure information selects the relay link to which the node is connected, sets the selected relay link in the control frame, It transmits to the relay link (West relay link 4) to which the own device is connected (step S13). The West pair node then matches the relay link set in the control frame received from the West relay link 4 with usable relay link information known by the own device, and the relay link is connected to the own device. If it is determined that the relay link is connected, the relay link port of the own device is regarded as open (relay link up), and data frame transfer to the relay link to which the own device is connected is started (step S14).

In this example, when a failure is detected, a control frame is transmitted in step S13 to open the relay link. Alternatively, the West pair nodes notify each other's nodes of relay link up instructions. By doing so, the relay link port may be opened.

FIG. 5 is a diagram showing an example of operation when a failure occurs in a pair node connected to a relay link in use. In the example of FIG. 5, it is assumed that a failure has occurred in the RPR ring node device 1-3 that is an East pair node connected to the East relay link 5 in use in the network system similar to FIG. Here, a partial failure of the East pair node of the network 2 is assumed, and it is assumed that the relay link disconnection of the East relay link 5 has not occurred.

First, the RPR ring node device 1-2 that is the West pair node on the network 2 side is based on the failure type and the failure detection node that are the protection information included in the RPR control frame received from the network 2, or based on the topology map. Based on the ring failure detection function, the occurrence of a failure in the RPR ring node device 1-3 is detected. Then, the RPR ring node device 1-2 adds the detection result to the control frame as relay link failure information and notifies the West pair node (RPR ring node device 1-6) on the network 3 side via the West relay link 4. Also, the relay link failure information is added to the RPR control frame and notified to the network 2 (step S21).

The West pair node on the network 3 side detects the unavailability of the East relay link 5 based on the control frame received via the West relay link 4, adds failure information to the RPR control frame, and notifies the network 3 (step S22). ). Based on the RPR control frame transmitted from the West pair node to the network 3, the East pair node on the network 3 side recognizes that the relay link (East relay link 5) connected to its own device is unusable, and the East relay node The link 5 is brought down (step S23), and then a relay link switching instruction is given to the RPR control frame and notified to the West pair node on the network 3 side (step S24). The West pair node that has received the RPR control frame including the relay link switching instruction sets the control frame to select the West relay link 4 to which the own apparatus is connected based on the instruction, and transmits to the West relay link 4 Similarly, the West pair node on the network 2 side also sets the control frame to select the West relay link 4 and transmits it to the West relay link 4 to exchange the information. When the link information matches the relay information and the relay link is connected to the own node, the relay link port is regarded as open, and the data frame is transferred to the adjacent ring network to the relay link (step S25).

FIG. 6 is a diagram illustrating an example of an operation in the case where a link break has occurred in two routes that can reach a pair node in use. In the example of FIG. 5, in the network system similar to that of FIG. 3, a path failure has occurred at two locations leading to the East pair node on the network 2 side connected to the east relay link 5 in use (the relay link disconnection has occurred). Not)

First, the East pair node (RPR ring node device 1-3) on the network 2 side detects the failure of both ports of its own device, and thereby determines whether the East relay link 5 is unusable. In addition, the West pair node (RPR ring node device 1-2) on the network 2 side detects the failure of the East relay link 5 based on the failure detection based on the RPR protection information or the ring failure detection function based on the topology map. To do. As a result of the above detection, the RPR ring node device 1-3 and the RPR ring node device 1-2 on the network 2 side add relay link failure information indicating that the East relay link 5 is unusable to the RPR control frame to the network 2. In addition, the relay link failure information is added to the control frame, and the corresponding pair node on the network 3 side is notified via the relay link to which the own apparatus is connected (steps S31 and S32).

The RPR ring node device 1-3 recognizes that the East relay link 5 connected to its own node is unusable, and then brings down the East relay link 5 to the West pair node (RPR ring node device 1- 1 in the network 2). Toward 2), an RPR control frame including a relay link switching instruction is transmitted (step S33). The RPR ring node device 1-2 sets the control frame to select the West relay link 4 to which the RPR ring node device 1 is connected and transmits it to the West relay link 4. The RPR ring node device 1-6 also performs similar control. The frame is transmitted to the West relay link 4. Each West pair node determines that the relay link set in the received control frame matches the usable relay link information and that the relay link is a relay link to which the own device is connected. The relay link port is regarded as open, and the data frame is transferred to the adjacent ring network to the relay link (step S34).

In addition, although this embodiment demonstrated the case where there were two relay links, it is not restricted to this, Operation | movement of this Embodiment is applicable when there are one or more relay links. FIG. 7 is a diagram illustrating an example of a network configuration when there is one relay link. For example, as shown in FIG. 7, even when there is one relay link, the pair node monitors the state of the relay link and includes the multilink information in the control frame in the same manner as the above-mentioned West pair node and East pair node. And send it to your network. In this case, since there is only one relay link, it is not possible to select another relay link in the event of a relay link failure. Therefore, in the event of a relay link failure, some other measures will be taken. The operation is the same as in this embodiment. In addition, when there are three or more relay links, the same operation as in this embodiment is performed, and each pair node connected to the relay link can connect another relay link when a relay link in use fails. At the time of selection, there are a plurality of candidate relay links. In this case, switching the relay links can be performed in the same manner as in the present embodiment by setting the priority order in advance.

As described above, in this embodiment, the pair nodes connected to the relay link connecting the ring networks notify each other of the failure status of the pair node connected to the relay link and the relay link using the control frame, and The RPR function is used to monitor the failure in the own ring network, and when a failure occurs in the relay link, the failure information is notified to the own ring network. When each pair node receives a control frame indicating that a failure has occurred in the relay link, if it is a failure of the relay link to which the own device is connected, the pair node drops the relay link of the own device, Another relay link in which no occurrence has occurred is selected, and a control frame including the selected relay link is transmitted through the relay link to which the own apparatus is connected. Each pair node, if the relay link set in the control frame is a relay link for which it is understood that no failure has occurred and is a relay link to which its own device is connected, The data frame was transferred to the link.

Therefore, information can be exchanged with the other pair node at high speed, and the path can be switched at high speed when a relay link failure occurs. Therefore, it is possible to shorten the time from the occurrence of a failure to communication recovery. As for failure detection, when the control frame transmission cycle is a milli-order or sub-milli-order cycle, high-speed detection of that cycle (milli-order or sub-milli order) is possible. In addition, RPR is applied to the failure monitoring of the pair node on the own ring network and the monitoring of the relay link route, and high speed detection is possible. As described above, since speeding up of failure notification and failure detection can be realized, a failure path switching time equivalent to that of a single ring network can be achieved in a multi-ring network environment.

Embodiment 2. FIG.
FIG. 8 is a diagram illustrating a functional configuration example of the second embodiment of the OAM ring node device according to the present invention. As shown in FIG. 8, an OAM ring node device 100 according to the present embodiment is a device that functions as an OAM ring node, and includes a line switch (SW) unit 101, an OAM interface transmission unit 102, an OAM interface reception unit 103, and protection. Unit 104, BP setting unit 105, outer ring receiving unit 106, outer ring drop determining unit 107, outer ring transmitting unit 108, inner ring transmitting unit 109, inner ring drop determining unit 110, inner ring receiving unit 111, control frame determining unit 112. Further, the ring node device 100 includes a relay link port 113 and another port 114 that is a port other than the relay link port 113.

FIG. 9 is a diagram illustrating a configuration example of the multi-ring network system according to the present embodiment. As shown in FIG. 9, the multi-ring network system of the present embodiment includes OAM ring nodes 100-1 to 100-8, and a network 121 in which the OAM ring node devices 100-1 to 100-4 are ring node networks. The OAM ring node devices 100-5 to 100-8 constitute a network 122 that is a ring node network. Each of the OAM ring node devices 100-1 to 100-8 has the same configuration as that of the OAM ring node device 100 shown in FIG. Also, the OAM ring node device 100-2 and the OAM ring node device 100-6 are set as a West pair node, and the OAM ring node device 100-3 and the OAM ring node device 100-7 are set as an East pair node. Further, the OAM ring node devices 100-1 and 100-8 are set as OAM master nodes, and the other OAM ring node devices are set as OAM slave nodes. In the OAM ring node devices 100-1 and 100-8, a blocked port (BP) 130 is set.

The two ring networks 121 and 122 are connected by two links, a West relay link 123 that connects the West pair nodes and an East relay link 124 that connects the East pair nodes. Further, the network 121 and the network 122 have two-way rings, an inner ring 125 and an outer ring 126.

Here, an operation when a failure occurs in a master node and a slave node of an Ethernet (registered trademark) ring protocol (hereinafter referred to as an OAM ring) by Ethernet (registered trademark) OAM will be described. The master node and slave node of the OAM ring perform route switching of the OAM ring network according to the following procedures (A) to (C).
(A) Ring configuration A block port (BP) is always set at one place in the ring so that no loop frame is generated in the OAM ring.
(B) An OAM ring node device including a port (BP setting port) set as a frame transmission / reception BP discards both a control frame and a data frame. An OAM ring node device that does not have a port set as a BP transfers both a control frame and a data frame.
(C) Fault path switching Fault detection using a CCM (Continuity Check Message) frame, fault notification using an APS (Automatic Protection Switching) frame, and address flush instruction, address re-learning at the time of fault, performing fault path detouring and sending Switch direction. At the time of failure recovery, the OAM ring node device that has detected recovery from the failure transmits a recovery notification using an APS frame, the master node performs BP setting for its own port, and then addresses all the OAM ring node devices. An APS frame for performing relearning and port blockage release notification is transmitted.

Also, in the OAM ring, there is a rule that the fault bypass time is a maximum of 50 milliseconds, and in the above processing, the operation from the fault detection to the switching of the sending direction by the address flush instruction is performed at high speed.

Next, returning to FIG. 8, the function of the OAM ring node device 100 of the present embodiment will be described. Similar to the concentrator switch unit 11 of the first embodiment, the concentrator switch (SW) unit 101 receives a MAC frame input from the relay link port 113 or the other port 114, and transmits to the relay link port 113 or the other port 114. Switching between output frame transmission and switching.

The OAM interface transmission unit 102 transfers the MAC frame received via the line concentration switch unit 101, generates an OAM control frame to which multiring information described later acquired from the protection unit 104 is added, and generates an inner ring or an outer ring. Is selected based on the failure detection information acquired from the protection unit 104, and the generated frame is selected from either the outer ring transmission unit 108 or the inner ring transmission unit 109 based on the selection result. Output to one or both. Further, the OAM interface transmission unit 102 generates an OAM control frame including an address flush instruction based on the instruction from the protection unit 104, and uses the generated frame as one of the outer ring transmission unit 108 and the inner ring transmission unit 109 or Output to both.

Based on the MAC frame received from the inner ring 125 or the outer ring 126, the OAM interface reception unit 103 identifies whether the MAC frame is a data frame or an OAM control frame. The information contained in the frame is notified to the protection unit 104, and if it is a data frame, the frame is passed to the line concentration switch unit 101. In addition, the OAM interface receiving unit 103 sets the multi-ring information acquired from the protection unit 104 in the OAM control frame, and passes the set OAM control frame to the line collection switch unit 101. Further, when the OAM interface receiving unit 103 is a master node, the OAM interface receiving unit 103 performs failure detection (failure detection by OAM control frame reception) due to failure to receive an OAM control frame within a predetermined time. This is notified to the protection unit 104, and when the failure is recovered (when the OAM control frame can be received normally), the protection unit 104 is notified of that.

Based on the information notified from the OAM interface receiving unit 103, the protection unit 104 grasps the failure status of the port of its own device, and in the event of a failure, multi-ring information is used to notify the master node. The OAM interface transmission unit 102 is notified. When the protection unit 104 receives a failure detection by receiving an OAM control frame from the OAM interface reception unit 103 when the own device is a master node, the protection unit 104 notifies the OAM interface transmission unit 102 of the failure detection information and issues an address flush instruction. The OAM interface transmission unit 102 is instructed to transmit the included OAM control frame, and then the BP setting unit 105 is notified of the BP release instruction of the own device (master node). Further, when the self-device is a master node, the protection unit 104 receives an OAM control frame reception notification from the OAM interface reception unit 103 to transmit an OAM control frame including an address flush instruction. To instruct. After that, the OAM interface transmission unit 102 is instructed to transmit an OAM control frame including a BP release instruction, and the BP setting unit 105 is notified of the BP setting instruction of the own apparatus.

Further, the protection unit 104 detects a failure of the relay link based on the control frame received from the relay link via the control frame determination unit 112, and uses the detection result as the multi-ring information as the OAM interface transmission unit 102 and the OAM interface reception unit 103. Notify

The BP setting unit 105 notifies the outer ring transmission unit 108, the inner ring transmission unit 109, the outer ring reception unit 106, and the inner ring reception unit 111 of the BP setting instruction and the BP release instruction from the protection unit 104.

The outer ring transmission unit 108 schedules both the traffic of the frame Add received from the OAM interface transmission unit 102 and the transit of the received frame Transit, and based on the scheduling result, the received frame received from the outer ring drop determination unit 107, and the OAM The frame received from the interface transmission unit 102 is transmitted to the outer ring 126. Furthermore, when the BP setting is notified from the BP setting unit 105, the outer ring transmission unit 108 discards the data frame and the OAM control frame without transmitting them, and when notified of the BP release, A data frame and an OAM control frame are transmitted.

The inner ring transmission unit 109 schedules both the traffic of the frame Add received from the OAM interface transmission unit 102 and the transit of the received frame Transit, and based on the scheduling result, the received frame received from the inner ring drop determination unit 110, and the OAM The frame received from the interface transmission unit 102 is transmitted to the inner ring 125. Further, when the BP setting is notified from the BP setting unit 105, the inner ring transmission unit 109 discards the data frame and the OAM control frame without transmitting them, and when notified of the BP release, A data frame and an OAM control frame are transmitted.

The outer ring receiving unit 106 checks whether there is an error in the frame received from the outer ring 126, and outputs the received frame after the check to the outer ring drop determining unit 107. The inner ring reception unit 111 checks whether there is an error in the frame received from the inner ring 125 and outputs the received frame after the check to the inner ring drop determination unit 110. Further, when the BP setting unit 105 is notified of the BP setting, the outer ring receiving unit 106 and the inner ring receiving unit 111 discard the received data frame and the OAM control frame, and are notified of the BP release. In this case, the data frame and the OAM control frame determined to have no problem in the error check are passed.

The outer ring drop determination unit 107 determines whether to relay or drop the reception frame received via the outer ring reception unit 106, and outputs the reception frame to the outer ring transmission unit 108 when not dropping. The inner ring drop determining unit 110 determines whether to relay or drop the received frame received via the inner ring receiving unit 111, and outputs the received frame to the inner ring transmitting unit 109 if not dropped.

The control frame determination unit 112 determines whether the frame received from the relay link port 113 via the line concentration switch unit 101 is a control frame. Then, in the case of a control frame, the control frame determination unit 112 extracts predetermined necessary information from the frame, notifies the protection unit 104 of the extraction result, and discards it without passing it to the OAM interface transmission unit 102. If it is not a control frame, it passes the frame to the OAM interface transmitter 102.

Here, the operation in the case where the OAM ring node apparatus 100 is a pair node (for example, a West pair node, an East pair node, etc.) connected to the relay link has been described. Of these, the processing for frames transmitted and received via the relay link is not performed.

In the present embodiment, the concentrator switch unit 101 is provided. However, even if the concentrator switch unit 101 is not provided, the present embodiment can be implemented by performing a change depending on the interface type of the relay link port as necessary. A similar operation can be realized with a configuration similar to that of the first embodiment.

In the present embodiment, the above operations (1) to (3) are applied in one ring network. In addition to the normal operation in the ring network, the monitoring of the relay link connecting the ring networks and the processing of the failure notification are performed in the following procedures (a ′) to (e ′) as follows.

(A ′) Control frames are transmitted to the relay link, and each pair node (for example, the West pair node and the East pair node in FIG. 9) monitors the connectivity of the relay link of its own device, and includes the monitoring result in the control frame. Send each other.
(B ′) When the OAM ring node device adjacent to each pair node detects a failure in a port on the pair node side, the failure detection is included in a VSM (Vendor Specific Message) type OAM control frame that can be freely defined by the vendor. Send immediately. Each pair node receives this OAM control frame, and monitors the presence or absence of a failure of the other pair node in its own ring network based on the frame.
(C ′) Multi-ring information (monitoring information (a ′) and (b ′)) used for determining a relay link failure is placed on the OAM control frame and transmitted to the ring.
(D ′) When each node detects a relay link failure, or when it detects a relay link failure based on an OAM control frame received from the other pair node, it passes through the relay link to which the device is connected. Perform failure detection based on whether the control frame can be received (failure detection based on whether the control frame can be received within a predetermined time), determine that there is a failure in the relay link to which the device is connected, and If the relay link is a relay link that is in use, another relay link that can be used as a candidate of the switching destination relay link is selected.
(E ′) Each pair node sets the selected relay link in the control frame and transmits it to the relay link to which the own device is connected, and each pair node recognizes the relay link included in the received control frame by the own device. If it matches the available relay link information and the relay link is a link to which the local device is connected, the relay link is considered to be up and the data frame is transferred to the relay link. To do.

In the configuration example of FIG. 8, the protection unit 104 performs monitoring of the above (a ′), (b ′), and (d ′), and the OAM interface transmission unit 102 performs (c ′). The unit 104 and the OAM interface receiving unit 103 perform (e ′).

Next, the operation of the present embodiment in each communication state will be described. FIG. 10 is a network configuration diagram illustrating an exemplary operation of a node during normal operation. The configuration of the network system in FIG. 10 is the same as that in FIG. 9, and the terminal 8-1 is connected to the OAM ring node device 100-5, and the terminal 8-2 is connected to the RPR ring node device 100-4. ing. In such a configuration, when the terminal 8-1 and the terminal 8-2 communicate, it is necessary to transmit and receive data between networks using a relay link connecting the network 121 and the network 122.

In this configuration, there are a plurality of usable relay links (West relay link 123 and East relay link 124) at normal times (no failure has occurred), and the relay link (data frame Relay link used for transmission). Since any method may be used for selecting which relay link to use as a relay link in a normal state, it is not particularly described here. In FIG. 10, the relay link using the East relay link 124 is used.

Each pair node (the OAM ring node devices 100-2 and 100-6 that are the West pair nodes and the OAM ring node devices 100-3 and 100-7 that are the East pair nodes) Is transmitted to the own ring network (step S41), and control frames including the multi-ring information and the failure information on the OAM ring are mutually notified (step S42). Also, a pair node (OAM ring node device 100-3, 100-7) having a relay link currently in use transfers a data frame to an adjacent ring network (for example, network 122 for the OAM ring node device 100-3). (Step S43), and the other pair node (OAM ring node device 100-2, 100-6) discards the data frame without transferring it to the relay link (Step S44).

Next, a case where a failure occurs will be described. FIG. 11 is a diagram illustrating an example of an operation when a failure occurs in a relay link in use. In the example of FIG. 11, in the network system similar to FIG. 9, it is assumed that a failure has occurred in the East relay link 124 in use due to disconnection or the like. First, the East pair node (OAM ring node device 100-3, 100-7) detects a failure (Signal Failure) by not receiving a control frame from the relay link to which the East pair node is connected for a predetermined time or more (step S51). ).

The East pair node adds the relay link failure information detected in step S51 to the OAM control frame and notifies the ring outside of the ring network 122 or the inner ring (step S52). The other pair node (West pair node in each network) that has received the OAM control frame including the relay link failure information selects the relay link to which the node is connected, and sets the selected relay link in the control frame. Then, the data is transmitted to the relay link (West relay link 123) to which the device is connected (step S53). The West pair node then matches the relay link set in the control frame received from the West relay link 123 with usable relay link information known by the own device, and the relay link is connected to the own device. If it is determined that the relay link is connected, the relay link port of the own device is regarded as open (relay link up), and data frame transfer to the relay link to which the own device is connected is started (step S54).

FIG. 12 is a diagram illustrating an example of an operation when a failure occurs in a pair node connected to a relay link in use. In the example of FIG. 12, it is assumed that a failure has occurred in the OAM ring node device 100-3 that is an East pair node connected to the used East relay link 124 in the network system similar to FIG. Here, a partial failure of the East pair node of the network 121 is assumed, and it is assumed that the relay link disconnection of the East relay link 124 has not occurred.

First, the West pair node on the network 121 side detects the unavailability of the East relay link 124 by detecting the failure of the East pair node based on the OAM loss determination. Based on this detection, the West pair node on the network 121 side adds relay link failure information indicating that the East relay link 124 is unusable to the OAM control frame and notifies the network 121, and also uses the relay link failure information in the control frame. Assigned and notified to the West pair node on the network 122 side via the West relay link 123 (step S61).

The West pair node on the network 122 side detects the unavailability of the East relay link 124 based on the control frame received from the West pair node of the network 121, adds the detected failure information to the OAM control frame, and transmits it to the network 122 ( Step S62). Based on the OAM control frame received from the West pair node on the network 122 side, the East pair node on the network 122 side recognizes that the relay link (East relay link 124) to which the own device is connected cannot be used, and The relay link is down (step S63), and a relay link switching instruction is given to the OAM control frame and notified to the West pair node of the network 122 (step S64).

Upon receiving the relay link switching instruction, the West pair node of the network 122 sets the control frame to select the relay link to which the own device is connected and transmits it to the West relay link 123. The same applies to the West pair node of the network 121. A control frame is transmitted to the West relay link 123. Each West pair node determines that the relay link set in the received control frame matches the usable relay link information and that the relay link is a relay link to which the own device is connected. The relay link port is regarded as open, and the data frame is transferred to the adjacent ring network to the relay link (step S65).

FIG. 13 is a diagram illustrating an example of an operation in the case where a link break has occurred in all of the two routes that can reach the pair node in use. In the example of FIG. 13, in the network system similar to FIG. 9, a path failure has occurred at two locations leading to the East pair node on the network 121 side connected to the used East relay link 124 (the relay link breakage has occurred). Not)

First, the East pair node (OAM ring node device 100-3) on the network 121 side detects the failure of both ports of its own device, and thereby determines whether the East relay link 124 is unusable. Further, the West pair node (OAM ring node device 100-2) on the network 121 side detects the failure of the East pair node by determining the loss of the OAM, and detects the unavailability of the East relay link 124. By the above detection, the OAM ring node device 100-3 and the OAM ring node device 100-2 on the network 121 side add relay link failure information indicating that the East relay link 124 cannot be used to the OAM control frame to the network 121. In addition, the relay link failure information is added to the control frame, and the corresponding pair node on the network 122 side is notified via the relay link to which the own apparatus is connected (steps S71 and S72).

After recognizing that the East relay link 124 connected to the OAM ring node apparatus 100-3 cannot be used, the OAM ring node apparatus 100-3 brings down the East relay link 124, and the West pair node (OAM ring node apparatus 100- Toward 2), an OAM control frame including a relay link switching instruction is transmitted (step S73). The OAM ring node apparatus 100-2 sets the control frame indicating that the West relay link 123 to which the OAM ring node apparatus is connected is transmitted to the West relay link 123, and the OAM ring node apparatus 100-6 performs similar control. The frame is transmitted to the West relay link 123. Each West pair node determines that the relay link set in the received control frame matches the usable relay link information and that the relay link is a relay link to which the own device is connected. The relay link port is regarded as open, and the data frame is transferred to the adjacent ring network to the relay link (step S74).

In addition, although this embodiment demonstrated the case where there were two relay links, it is not restricted to this, Operation | movement of this Embodiment is applicable when there are one or more relay links. In addition, when there are three or more relay links, the same operation as this embodiment can be applied.

As described above, in the present embodiment, the pair nodes connected to the relay link connecting the ring networks notify each other of the failure status of the pair node connected to the relay link and the relay link using the control frame. The OAM disappearance determination function is used to monitor a failure in the own ring network, and when a failure occurs in the relay link, the failure information is notified to the own ring network. When each pair node receives a control frame indicating that a failure has occurred in the relay link, if it is a failure of the relay link to which the own device is connected, the pair node drops the relay link of the own device, Another relay link in which no occurrence has occurred is selected, and a control frame including the selected relay link is transmitted through the relay link to which the own apparatus is connected. Each pair node, if the relay link set in the control frame is a relay link for which it is known that no failure has occurred and is a relay link to which its own device is connected, The data frame was transferred to the link. Therefore, even in a multi-ring network connecting a plurality of OAM ring networks, the same effects as in the first embodiment can be obtained.

As described above, the ring node device, the multi-ring network system, and the path switching method according to the present invention are useful for a system that switches a communication path when a failure occurs in a ring network, and particularly, from a failure occurrence to a communication recovery. Suitable for systems that need to be done in time.

Claims (14)

1. A plurality of ring networks are provided, and at least one of the ring node devices constituting the ring network is a pair node, and is transmitted / received between different ring networks via a relay link that is a link connecting a pair of pair nodes. In a multi-ring network system for relaying data as relay data, a ring node device that functions as the pair node,
   Ring interface reception that transmits relay data received from the ring network to which the local device belongs to the relay link to which the local device is connected, and transmits a control frame indicating the state of the relay link to the other pair node connected by the relay link Means,
   Ring interface transmission means for transmitting relay data received from a relay link to which the own device is connected to other ring node devices in the ring network to which the own device belongs,
   Based on the control frame received from the other pair node via the relay link to which the own device is connected, it is monitored whether or not a failure has occurred in the relay link. Instructing the ring interface receiving means to transmit a control frame to that effect to the other pair node, and a protection means for performing a predetermined communication path switching process;
   With
   The ring interface apparatus, wherein the ring interface receiving means transmits a control frame based on the instruction.
2. A plurality of the pair nodes are provided,
   The protection means monitors a failure of another pair node in the ring network to which the own device belongs, and if a failure is detected, generates other node failure information including information for identifying the failed node. ,
   The ring interface transmission means includes the other node failure information in a ring control frame that is a control frame used in the ring network, and transmits the ring control frame to another ring node device in the ring network to which the own device belongs. The ring node device according to claim 1, wherein:
3. The protection means instructs the ring interface transmission means to transmit failure information indicating that in a ring control frame when a failure occurs in a relay link to which the device is connected,
   3. The ring according to claim 2, wherein the ring interface transmitting means transmits a ring control frame including the failure information to another ring node device in the ring network to which the own device belongs based on the instruction. Node device.
4. At least one of the relay links is a use relay link that relays the relay data,
   The protection means includes
   When a failure occurs in the relay link to which the local device is connected, as the predetermined communication path switching process, if the relay link is a used relay link, another relay link in which no failure has occurred is switched to Instructing the ring interface receiving means to transmit control data designated as a link, instructing the relay stop of relay data by the own device,
   On the other hand, when the switching destination link specified by the control data received from the other pair node is a relay link in which no failure has occurred and is a relay link to which the own device is connected, the predetermined communication path As a switching process, the relay link is used as a use relay link, and the relay start of relay data by the own device is instructed.
   The ring node device according to claim 2, wherein:
5. At least one of the relay links is a use relay link that relays the relay data,
   The protection means includes
   When a failure occurs in the relay link to which the local device is connected, as the predetermined communication path switching process, if the relay link is a used relay link, another relay link in which no failure has occurred is switched to Instructing the ring interface receiving means to transmit control data designated as a link, instructing the relay stop of relay data by the own device,
   On the other hand, when the switching destination link specified by the control data received from the other pair node is a relay link in which no failure has occurred and is a relay link to which the own device is connected, the predetermined communication path As a switching process, the relay link is used as a use relay link, and the relay start of relay data by the own device is instructed.
   The ring node device according to claim 3.
6. The protection means instructs the ring interface transmission means to transmit failure information indicating that in a ring control frame when a failure occurs in a relay link to which the device is connected,
   2. The ring according to claim 1, wherein the ring interface transmitting unit transmits a ring control frame including the failure information to another ring node device in the ring network to which the own device belongs based on the instruction. Node device.
7. A plurality of the pair nodes are provided, and at least one of the relay links is a use relay link that relays the relay data,
   The protection means includes
   When a failure occurs in the relay link to which the local device is connected, as the predetermined communication path switching process, if the relay link is a used relay link, another relay link in which no failure has occurred is switched to Instructing the ring interface receiving means to transmit control data designated as a link, instructing the relay stop of relay data by the own device,
   On the other hand, when the switching destination link specified by the control data received from the other pair node is a relay link in which no failure has occurred and is a relay link to which the own device is connected, the predetermined communication path As a switching process, the relay link is used as a use relay link, and the relay start of relay data by the own device is instructed.
   The ring node device according to claim 6.
8. The control frame is transmitted at a predetermined cycle,
   8. The protection unit according to claim 1, wherein if the control frame cannot be received for a predetermined time longer than the period, the protection unit determines that a failure has occurred in the relay link to which the apparatus is connected. The ring node device according to claim 1.
9. The ring node device according to any one of claims 1 to 7, wherein the ring network is a ring network using RPR as a ring protocol.
10. The ring node device according to any one of claims 1 to 7, wherein the ring network is a ring network using Ethernet (registered trademark) OAM as a ring protocol.
11. The ring node device according to claim 8, wherein the ring network is a ring network using RPR as a ring protocol.
12. The ring node apparatus according to claim 8, wherein the ring network is a ring network using Ethernet (registered trademark) OAM as a ring protocol.
13. A plurality of ring networks are provided, and at least one of the ring node devices constituting the ring network is a pair node, and is transmitted / received between different ring networks via a relay link that is a link connecting a pair of pair nodes. A multi-ring network system that relays data as relay data,
    A ring node device functioning as the pair node,
    Ring interface reception that transmits relay data received from the ring network to which the local device belongs to the relay link to which the local device is connected, and transmits a control frame indicating the state of the relay link to the other pair node connected by the relay link Means,
    Ring interface transmission means for transmitting relay data received from a relay link to which the own device is connected to other ring node devices in the ring network to which the own device belongs,
    Based on the control frame received from the other pair node via the relay link to which the own device is connected, it is monitored whether or not a failure has occurred in the relay link. Instructing the ring interface receiving means to transmit a control frame to that effect to the other pair node, and a protection means for performing a predetermined communication path switching process;
    With
    The ring interface receiving means transmits a control frame based on the instruction, and a multi-ring network system.
14. A plurality of ring networks are provided, and at least one of the ring node devices constituting the ring network is a pair node, and is transmitted / received between different ring networks via a relay link that is a link connecting a pair of pair nodes. In a multi-ring network system that relays data as relay data, a path switching method in the ring node device functioning as the pair node,
    A ring reception step of transmitting relay data received from the ring network to which the own device belongs to a relay link to which the own device is connected;
    A control frame transmission step of transmitting a control frame indicating the state of the relay link to the other pair node connected by the relay link to which the own device is connected;
    A ring transmission step of transmitting relay data received from a relay link to which the own device is connected to another ring node device in the ring network to which the own device belongs;
    Based on the control frame received from the other pair node via the relay link to which the own device is connected, it is monitored whether or not a failure has occurred in the relay link. Instructing to transmit a control frame to that effect to the other pair node, and a switching step for performing a predetermined communication path switching process;
    A failure notification step of transmitting a control frame based on the instruction;
    A path switching method comprising:

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