JP2012178749A - Ring shaped network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure that occurrence of communication failures such as broadcast storms are surely avoided even when bypass devices are used in a ring shaped network using a ring control protocol for loop avoidance.SOLUTION: If one port 2 in nodes N1-N4 is a blocking port, a blocking notification packet, indicating the effect that the port is a blocking port, is transmitted in a certain cycle from the blocking port to a port of an adjacent node N3. If the adjacent node N3 receives this blocking notification packet within a prescribed period, the port of the node N3 which received the packet is placed into an auxiliary blocking state, while, if the blocking notification packet is not received within the prescribed period, the auxiliary blocking state is canceled.

Description

  The present invention relates to a ring network system in which nodes composed of a plurality of LAN switches for switching a failure path are connected in a ring shape and a ring control protocol for loop avoidance operates.

  As a communication network, a configuration in which a LAN network such as a layer 2 switch for switching a failure path is a node and a plurality of these nodes are connected in a ring shape to form a ring network has been widely adopted. Yes. In a ring network using such a LAN switch as a node, it is possible to provide path redundancy. Therefore, even if one part of the network is disconnected due to a failure, there is no mutual connection between all nodes in the remaining network. It is possible to continue communication.

  By the way, in such a ring network, if there is a so-called loop in which there is no logically blocked port at any point, a data packet circulates in the ring network and is generally called a broadcast storm. It can cause a condition.

  Conventionally, a spanning tree protocol has been widely used as a ring control protocol for eliminating the occurrence of such a broadcast storm (for example, see Non-Patent Document 1 below). By applying this spanning tree protocol, it is possible to avoid the occurrence of a broadcast storm by logically blocking one port at any node while ensuring the redundancy of the ring when a failure occurs. A port that is logically blocked (blocked) is referred to as a blocking port.

  In other words, when a part of the ring is disconnected due to a failure, the spanning tree protocol is reconfigured, and the blocking port so far is released by the cooperative operation between the LAN switches constituting each node, and the route is automatically routed. Switching is performed and data relay is resumed. As a result, communication between all nodes in the network is continued. After this, when the failure is recovered, the spanning tree protocol is reconfigured and one of the ports that have been released from blocking is again blocked, and the state returns to the state of avoiding the loop.

  By the way, as described above, even if a part of the ring is disconnected due to a failure in a ring network in which a plurality of nodes composed of LAN switches are connected in a ring shape, as long as the spanning tree protocol is used, the redundancy is maintained. It is possible to continue communication between all the nodes by the sex function. However, for example, when a plurality of nodes become inoperable at the same time due to a power failure or the like, even if nodes other than those inoperable nodes can operate in the power supply state, the entire network cannot be configured at all, Communication between nodes is interrupted.

  Therefore, in order to continue communication between multiple nodes even if they become inoperable due to a power failure or the like at the same time, in the prior art, for example, a bypass device is connected to each node, and the nodes become inoperable due to a power failure or the like. When this happens, a bypass device is activated to bypass this inoperable node so that the ports of the previous and subsequent nodes can be connected, thereby enabling communication between the nodes. (See, for example, Patent Document 1 below).

Japanese Patent Laid-Open No. 2005-12477

IEEE 802.1D, 1998 Edition

  However, in a ring network, when the above bypass device is used in combination with the ring control protocol for avoiding loops such as the spanning tree protocol, multiple nodes become inoperable due to a power failure etc. at the same time. In some cases, there is an advantage that communication between each other can be continued, but on the other hand, depending on the location of the blocking port, the packet bypasses the blocking port, and there is no blocking port on the ring. . As a result, there is a problem that the network becomes a loop and may cause a broadcast storm.

  The present invention has been made to solve the above-described problems, and in a ring network using a ring control protocol for avoiding a loop, even if a bypass device is used, communication failures such as broadcast storms can be reliably generated. The object is to further improve the fault-tolerant performance of the entire network as compared to the conventional case.

  The present invention includes a plurality of nodes including LAN switches that perform failure path switching, and at least one of the nodes is provided with a bypass device for bypassing the node. A ring network system that is connected in a ring shape to form a ring network and that operates a ring control protocol for loop avoidance employs the following configuration.

  That is, in the present invention, when one of its own ports is in a blocking state, a blocking notification packet indicating that the port is in a blocking state is transmitted from the blocking state port to an adjacent node at a constant cycle T1. When the blocking notification packet is received from the blocking port notification means and the blocking port notification means within a predetermined period T2 (> T1), the adjacent port of the node that has received the packet is placed in the auxiliary blocking state. Each node is provided with auxiliary blocking transition / cancellation means for canceling the auxiliary blocking state when the blocking notification packet is not received within the predetermined period T2.

  According to the present invention, in a ring network incorporating a bypass device, since a node having a port in a blocking state transmits a blocking notification packet to a node adjacent thereto, the node that has received this blocking notification packet It is possible to reliably grasp that the port of the adjacent node is in the blocking state. If the port of the adjacent node is in the blocking state, the node that has received the blocking notification packet sets the port that has received the packet to the auxiliary blocking state to prevent a loop from occurring. For this reason, even if a loop avoidance protocol is used in a ring network incorporating a bypass device, the occurrence of a broadcast storm can be prevented. Moreover, the network path can be bypassed by the bypass device when a node failure occurs. As a result, it is possible to further improve the fault tolerance performance of the entire network than before.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the ring network system in Embodiment 1 of this invention, and has shown the state in which each node is operating normally. It is explanatory drawing of the packet for communication which has a format based on BPDU prescribed | regulated by MAC (media access control) used by the system. FIG. 3 is a configuration diagram immediately after a bypass device is activated and a bypass path is formed because power supply to one node is stopped in the system. It is a block diagram which shows the state which fixed time passed since the bypass apparatus was started and the bypass path | route was formed because the electric power feeding to one node stopped in the same system. 4 is a flowchart for explaining a processing operation of a node that transmits a blocking notification packet in the system. 4 is a flowchart for explaining a processing operation of a node that receives a blocking notification packet in the system. In the same system, it is explanatory drawing of the packet for communication used in order to grasp | ascertain whether an adjacent node is in a blocking state, or to make the port of an own node into an auxiliary blocking state. In the same system, it is explanatory drawing of the packet for other communications used in order to grasp | ascertain whether an adjacent node is in a blocking state or to make the port of an own node into an auxiliary blocking state.

  Embodiments of a ring network system according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by these each embodiment.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a ring network system according to Embodiment 1 of the present invention.

  The ring network system according to the first embodiment includes a plurality of nodes N1 to N4 composed of LAN switches that perform failure path switching, and a bypass device 5 for bypassing the node N2 is provided at the node N2. The nodes N1 to N4 and the bypass device 5 are sequentially connected in a ring shape to form a ring network.

  Here, in order to facilitate understanding and explanation of the invention, a case where a ring network is configured with four nodes N1 to N4 is shown, but the number of nodes is only four. It is not limited to. Further, although the bypass device 5 is provided for one node N2, the present invention is not limited to this, and the case where the bypass device 5 is provided for each of the other nodes N1, N3, and N4 may be used. The case of the structure which provided the bypass apparatus 5 separately with respect to N1-N4 may be sufficient.

  Further, the ring network system of the first embodiment is defined to operate by a ring control protocol (for example, spanning tree protocol) for loop avoidance under MAC (Media Access Control). Therefore, when all of the nodes N1 to N4 are operating normally, one route from among the nodes N1 to N4 is obtained by exchanging control frames for loop avoidance called BPDU (bridge protocol data unit) as is well known. As the bridge is determined, one port of the node is blocked to form a logical loop-free tree structure. Here, as an example, it is assumed that the port 2 of the node N2 is currently blocked and becomes a blocking port.

  Further, as a feature of the first embodiment, among the nodes N1 to N4, a node having a blocking port (node N2 in this example) is a node adjacent to the blocking port (node N3 in this example). The operation is programmed so as to transmit a blocking notification packet indicating that the port 2 of its own is in a blocking state to the destination at a constant cycle T1 (for example, 1 second cycle).

  In this case, the blocking notification packet uses, for example, a format compliant with the previous BPDU defined by MAC (Media Access Control) such as Ethernet (registered trademark) as shown in FIG. That is, this packet is composed of a total of six fields F0 to F5 including a preamble F0, a destination MAC address F1, a transmission source MAC address F2, a data type F3, communication data F4, and a bit error detection code string (FCS) F5. Yes.

  On the other hand, for the node that receives this blocking notification packet (node N3 in this example), when the packet is received, the port adjacent to blocking port 2 (port 1 in this example) is shifted to the auxiliary blocking state. As long as the blocking notification packet is constantly received within a certain period T2 (for example, 3 seconds), the auxiliary blocking state for the port that receives the blocking notification packet (port 1 in this example) is continued. When one port is in the auxiliary blocking state, normal packets other than the above-described loop avoidance control frame (BPDU) are not relayed as in the case of a normal blocking port. If a blocking notification packet is not input to a port (port 1 in this example) even after a certain period T2, the auxiliary blocking state of the port (port 1 in this example) is programmed to be released. .

  In the above configuration, when all of the nodes N1 to N4 are operating normally, as shown in FIG. 1, the port 2 of the node N2 is a blocking port, and the port 1 of the node N3 is an auxiliary blocking port. ing. For this reason, it does not become a loop and a multicast storm does not occur. Then, due to the redundancy function (path switching) of each of the nodes N1 to N4, normal packets are communicated while avoiding the blocking port and the auxiliary blocking port.

  Next, when the node N2 becomes inoperable due to, for example, a power failure from the state shown in FIG. 1 (from immediately after the operation is stopped until the period T2 elapses), the bypass device 5 is activated as shown in FIG. Thus, the port 2 of the node N1 and the port 1 of the node N3 are short-circuited via the bypass device 5. Immediately after the operation of the node N2 is stopped (from the time immediately after the operation is stopped until the period T2 elapses), since the port 1 of the node N3 is still operating as an auxiliary blocking port, it does not become a loop and a multicast storm occurs. do not do. Each of the nodes N1, N3, and N4 other than the node N2 that has stopped operating communicates normal packets while avoiding the auxiliary blocking port by its redundancy function (path switching).

  Subsequently, when a certain period of time T2 has elapsed from the state shown in FIG. 2, as shown in FIG. 4, the node N3 releases the auxiliary blocking state of the port 1, but until this auxiliary blocking state is released. During the period (from immediately after the operation is stopped until the period T2 elapses), one root bridge is determined from among the nodes N1 to N4 by exchanging control frames (BPDUs) for loop avoidance of the ring control protocol. At the same time, one port of the node is blocked to form a logical loop-free tree structure. Here, as an example, assume that port 2 of node N1 is blocked and becomes a blocking port.

  Thus, when the port 2 of the node N1 is blocked and becomes a blocking port, the node N1 sends a blocking notification packet to the adjacent node N3 via the bypass device 5 as shown in FIG. The node N3 that has received this blocking notification packet shifts the port 1 that receives the packet to the auxiliary blocking state. For this reason, it does not become a loop and a multicast storm does not occur. Each of the nodes N1, N3, and N4 other than the node N2 that has stopped operating communicates normal packets in a state where the blocking port and the auxiliary blocking port are avoided by the redundancy function (path switching).

  FIG. 5 is a flowchart for explaining the processing operation of the node that transmits the blocking notification packet. In the following, the symbol S means each processing step.

Each node determines whether or not it has a blocking port in its own device (S11). If a blocking port is formed in its own device by applying a ring control protocol for loop avoidance, Sends a blocking notification packet to the adjacent node (S12). Then, after a certain time T1 (for example, 1 second) has elapsed since the transmission of the blocking notification packet (S13), the process returns to S11. Thereby, when a node has a blocking port, a blocking notification packet is transmitted to a node adjacent to the blocking port at a fixed period T1.
Therefore, S11 to S13 in the flowchart shown in FIG. 5 correspond to the blocking port notification means in the claims.

  FIG. 6 is a flowchart for explaining the processing operation of the node that receives the blocking notification packet.

  Each node determines whether or not a blocking notification packet has been received (S21). If the node receives the blocking notification packet, it sets an auxiliary blocking timer (for example, T2 = 3 seconds) (S22), and the blocking notification packet. Is changed to the auxiliary blocking state (S23). Then, it is determined whether or not the auxiliary blocking timer is “0” (S24). If the auxiliary blocking timer has not reached “0”, the auxiliary blocking timer is decremented (S25), and the process returns to S21. .

  As long as a node having a blocking port in its own device is operating normally, a blocking notification packet is transmitted from that node at a fixed period T1 (<T2). Therefore, S21 to S25 are repeated, and the auxiliary blocking state is set. Will continue.

  On the other hand, when a node having a blocking port in its own device stops operating due to a power failure, no blocking notification packet is input from that node (No in S21), so that the auxiliary blocking timer is set to T2 (3 Seconds), “0” is reached (S24). At this time, it is determined whether or not the port is an auxiliary blocking port (S26). If the port is an auxiliary blocking port, the auxiliary blocking state is canceled (S27), and the process returns to S21. Note that a node that is not in the position of receiving the blocking notification packet does not have its own port as an auxiliary blocking port.

Note that the auxiliary blocking state is released after a certain period T2 elapses (S27), but during the period immediately after the operation is stopped until the period T2 elapses, a new blocking is applied by applying a ring control protocol for loop avoidance. Since a port is elected, the occurrence of a broadcast storm can be reliably avoided by blocking by the auxiliary blocking port during the period up to that point.
Therefore, S21 to S27 in the flowchart shown in FIG. 6 correspond to the auxiliary blocking transition / release means in the claims.

  As described above, according to the first embodiment, in a ring network incorporating a bypass device, a node having a port in a blocking state transmits a blocking notification packet to a node adjacent thereto. The node that has received the blocking notification packet can surely grasp that the port of the adjacent node is in the blocking state. If the port of the adjacent node is in the blocking state, the node that has received the blocking notification packet sets the reception port in the auxiliary blocking state to prevent a loop from occurring. For this reason, even if a loop avoidance protocol is used in a ring network incorporating a bypass device, the occurrence of a broadcast storm can be prevented. Moreover, the network path can be bypassed by the bypass device when a node failure occurs. As a result, it is possible to further improve the fault tolerance performance of the entire network than before.

Embodiment 2. FIG.
In the first embodiment, a node having a blocking port transmits a blocking notification packet at a certain period, and the port of the node receiving the blocking notification packet is in an auxiliary blocking state during the reception period. The auxiliary blocking state was canceled if it did not reach within a certain period.

  On the other hand, in the second embodiment, adjacent nodes always inquire about whether a blocking port is formed with respect to the partner node.

  That is, each node transmits a blocking inquiry packet to an adjacent node at a constant cycle T1 (for example, 1 second cycle). If the node that received the inquiry packet is in the blocking state, the node that received the inquiry packet returns a blocking response packet to the inquiry destination node in response to this. Then, the node that has received the returned blocking response packet sets the port that has received the packet to the auxiliary blocking state.

  In the example shown in FIG. 1, when a blocking inquiry packet is transmitted from the node N3 to the node N2, the node N2 that has received this inquiry packet has its own port 2 that has received this inquiry packet in a blocking state. Then, a blocking response packet is returned to the inquired node N3. The node N3 that has received the returned blocking response packet sets the port 1 that has received the packet to the auxiliary blocking state.

  In addition, even if the node N3 transmits a blocking inquiry packet to the adjacent node N2, a blocking response is received even if a certain period T2 (for example, 3 seconds) elapses from the port 2 of the counterpart node N2. If the packet is not returned, it is determined that the port 2 of the partner node N2 whose transmission of the blocking response packet has been interrupted has been eliminated, and the auxiliary blocking state of its own port 1 is released.

  Note that the blocking inquiry packet in this case uses, for example, a format conforming to the BPDU defined by the MAC (Media Access Control) shown in FIG. 2, and the destination MAC address F1 is set to broadcast. As shown in FIG. 7, a flag “1” is set on a part of the communication data F4 (for example, the least significant bit at the end) so that the other party can know that it is a blocking inquiry packet. . Further, for example, as shown in FIG. 8, the blocking response packet changes a part of the communication data f4 (for example, the least significant bit at the end of the communication data F4) from the flag “1” to the flag “0”. Thus, the other party knows that it is a blocking response packet.

  As described above, according to the second embodiment, it is possible to reliably grasp whether an adjacent node is in a blocking state by always transmitting a blocking inquiry packet to adjacent nodes. If the partner node's port is in the blocking state, the local node's port can be shifted to the auxiliary blocking state when a response packet returned from the inquired node is received. Even if a loop avoidance protocol is used in a ring network, it is possible to prevent the occurrence of a broadcast storm.

Embodiment 3 FIG.
In the above-described second embodiment, whether or not blocking ports are formed with respect to nodes adjacent to each other is periodically inquired and confirmed. However, in this third embodiment, each node always changes to an adjacent node. On the other hand, the node that received the port status packet indicating that the port is in the blocking state transmits the port status packet for identification to clearly indicate whether the port is in the blocking state or the non-blocking state. Put the port in the auxiliary blocking state.

That is, in the example shown in FIG. 1, each of the nodes N1 to N4 transmits a port status packet indicating the status of its own port to an adjacent node at a constant cycle T1 (for example, a cycle of 1 second).
In this case, since the port 2 of the node N2 is in the blocking state, the port 2 of the node N2 transmits a port state packet indicating that its own port is in the blocking state to the adjacent node N3. As the port status packet in this case, for example, as shown in FIG. 7, in order to indicate that the own port is in the blocking state, the last least significant bit portion of the communication data F4 in the packet is flagged as a blocking bit. Send it by setting “1”.
Further, since the port 2 of the other nodes N1, N3, and N4 is not in the blocking state, the port state packet in this case indicates that its own port is in the non-blocking state as shown in FIG. 8, for example. For this purpose, transmission is performed by setting a flag “0” at the last least significant bit of the communication data F4 in the packet.

  Then, the node N3 that has received the port status packet whose blocking bit included in the communication data F4 is the flag “1” determines that the port 2 of the partner node 2 is in the blocking status, and has received the port status packet. Port 1 is set to the auxiliary blocking state.

  Further, when the port state packet indicating the blocking state is not transmitted from the port 2 of the counterpart node N2, the blocking bit included in the communication data F4 is changed from the flag “1” to the flag “0” in the above example. The node N3 determines that the blocking state of the port 2 of the node N2 has been canceled, and the node N3 releases the auxiliary blocking state of its own port 1.

  As described above, according to the third embodiment, each node always transmits a port status packet indicating its own port status to the adjacent node, so that the port of the adjacent node is in the blocking state. It is possible to know for sure. If the port of the partner node is in the blocking state, the port that received the packet can be shifted to the auxiliary blocking state when the port state packet indicating that is received. Even if a loop avoidance protocol is used in a network, broadcast storms can be prevented.

Embodiment 4 FIG.
In Embodiment 3 described above, a node that constantly transmits a port status packet indicating its own port status to an adjacent node from each node and receives a port status packet indicating that it is in a blocking status, In this embodiment, each node whose own port is not in the blocking state always transmits a port state packet to the adjacent node. A node whose port is in a blocking state is configured not to transmit a port state packet.

That is, in the example shown in FIG. 1, since the port 2 of the nodes N1, N3, and N4 is not in the blocking state, for example, as shown in FIG. 7, the flag “1” is placed at the end of the least significant bit of the communication data F4. The port status packet for identification that clearly indicates the non-blocking state is transmitted to the adjacent node at a constant cycle (for example, 1 second cycle). On the other hand, since the node N2 has its own port 2 in the blocking state, the port 2 does not transmit any port state packet to the adjacent node N3. Then, the node N3 that has received the port status packet and has not received it halfway,
It is determined that the port 2 of the adjacent node 2 is in a blocking state, and the reception port 1 of the node 2 is set in the auxiliary blocking state.
In addition, in the node N3, when the port state packet starts to be transmitted again from the port 2 of the counterpart node N2, the node N3 determines that the blocking state of the port 2 of the node N2 has been canceled, and the node N3 The auxiliary blocking state of port 1 is released.

  As described above, according to the fourth embodiment, each node whose own port is not in the blocking state always transmits the port state packet to the adjacent node, but the node whose port is in the blocking state is Since the port state packet is not transmitted, it is possible to grasp whether the port of the adjacent node is in the blocking state. If the port of the partner node is in the blocking state, the adjacent port of its own node can be shifted to the auxiliary blocking state. Therefore, even if the loop avoidance protocol is used in the ring network incorporating the bypass device, the storm Can be prevented.

Embodiment 5 FIG.
In the above first to fourth embodiments, in order to grasp whether or not the port of the adjacent node is in the blocking state, a packet for confirming the blocking state is constantly transmitted from any node at a constant cycle. I have to.

  On the other hand, in the fifth embodiment, instead of transmitting a packet for confirming the blocking state from any node at regular intervals, the port of the node transitions between the non-blocking state and the blocking state. Only when the packet is transmitted to the adjacent node.

  That is, each of the nodes N1 to N4 receives a blocking transition packet when one of its ports transitions from the non-blocking state to the blocking state, and cancels blocking when the port transitions from the blocking state to the non-blocking state. The packet is transmitted to the adjacent node. When a blocking transition packet is received, the receiving port is shifted to an auxiliary blocking state, and when a blocking release packet is received, auxiliary blocking of the receiving port is released.

  In the example illustrated in FIG. 1, when the port 2 of the node N2 transitions from the non-blocking state to the blocking state, a blocking transition packet is transmitted from the port 2 to the adjacent node N3. The node N3 that has received this blocking transition packet transitions its reception port 1 to the auxiliary blocking state.

  Further, when the port 2 of the node N2 transits from the blocking state to the non-blocking state, the blocking release packet is transmitted from the port 2 to the adjacent node N3 at that time. The node N3 that has received this blocking release packet releases the auxiliary blocking state of the reception port 1.

  As a blocking transition packet in this case, as shown in FIG. 7, a flag “1” is set on a part of the communication data F4 (for example, the least significant bit at the end), and this is the blocking transition packet. The other party can understand. As the blocking release packet, for example, as shown in FIG. 8, a part of the communication data F4 (for example, the least significant bit at the end of the communication data F4) is changed from the flag “1” to the flag “0”. Thus, the other party knows that it is a blocking release packet.

  As described above, according to the fifth embodiment, it is possible to grasp whether or not the adjacent node is in the blocking state by the above operation, and while the node is in the blocking state, the own node can be shifted to the auxiliary blocking state. Even if a loop avoidance protocol is used in a ring network incorporating a bypass device, it is possible to prevent the occurrence of a broadcast storm.

  Further, in this fifth embodiment, instead of always transmitting a packet for confirming the blocking state from one of the nodes at a fixed period, the port of the node has transitioned between the non-blocking state and the blocking state. Only when the packet is transmitted to the adjacent node, the occurrence of excessive communication traffic in the network can be reduced.

  Further, the present invention is not limited to the configuration aspects of the above-described first to fifth embodiments. For example, the configurations of the first to fifth embodiments can be combined in a timely manner without departing from the spirit of the invention. Various modifications can be made in the range.

  N1 to N4 nodes (LAN switches), 5 bypass devices.

Claims (5)

Provided with a plurality of nodes composed of LAN switches for switching the failure path, and at least one of the nodes is provided with a bypass device for bypassing the node, and each node and the bypass device are connected in a ring shape In a ring network system in which a ring network is configured and a ring control protocol for loop avoidance operates,
When one of its own ports is in a blocking state, blocking port notification means for transmitting a blocking notification packet indicating that the port is in a blocking state from this blocking state port to an adjacent node at a constant period T1,
When the blocking notification packet is received from the blocking port notification means within a predetermined period T2 (> T1), the adjacent port of the node that has received the packet is placed in the auxiliary blocking state, and the blocking notification packet is set to the predetermined port. An auxiliary blocking transition / cancellation means for canceling the auxiliary blocking state if not received within the period T2,
A ring network system comprising: Provided with a plurality of nodes composed of LAN switches for switching the failure path, and at least one of the nodes is provided with a bypass device for bypassing the node, and each node and the bypass device are connected in a ring shape In a ring network system in which a ring network is configured and a ring control protocol for loop avoidance operates,
Inquiry means for inquiring at regular intervals by a blocking inquiry packet whether adjacent ports of the node are in a blocking state with respect to nodes adjacent to each other;
When the port of the previous node inquired by the blocking inquiry packet by the inquiry means is in a blocking state, a reply means for returning a blocking response packet in response thereto;
When the blocking response packet returned from the reply means is received, the adjacent port of the node that has received the packet is set in an auxiliary blocking state. On the other hand, when the blocking response packet is not received, the auxiliary blocking state is set. Auxiliary blocking transition / cancellation means for releasing,
A ring network system comprising: Provided with a plurality of nodes composed of LAN switches for switching the failure path, and at least one of the nodes is provided with a bypass device for bypassing the node, and each node and the bypass device are connected in a ring shape In a ring network system in which a ring network is configured and a ring control protocol for loop avoidance operates,
Port state notification means for transmitting a port state packet for identification indicating whether one of its own ports is in a blocking state or a non-blocking state to nodes adjacent to each other;
When the port status packet received from the port status notification means indicates that the adjacent port of the source node is in a blocking state, the adjacent port of the node that has received the packet is placed in an auxiliary blocking state. An auxiliary blocking transition / cancellation means for canceling the auxiliary blocking state when the adjacent port of the source node indicates a non-blocking state;
A ring network system comprising: Provided with a plurality of nodes composed of LAN switches for switching the failure path, and at least one of the nodes is provided with a bypass device for bypassing the node, and each node and the bypass device are connected in a ring shape In a ring network system in which a ring network is configured and a ring control protocol for loop avoidance operates,
Port state notification means for transmitting a port state packet indicating a non-blocking state only when all of its own ports are in a non-blocking state to nodes adjacent to each other at a fixed period;
If there is no notification of the port status packet from the port status notification means, the adjacent port of the node that does not receive the packet is set to the auxiliary blocking state, whereas if the notification of the port status packet is received, the auxiliary blocking is set. Auxiliary blocking transition / release means for releasing the state;
A ring network system comprising: Provided with a plurality of nodes composed of LAN switches for switching the failure path, and at least one of the nodes is provided with a bypass device for bypassing the node, and each node and the bypass device are connected in a ring shape In a ring network system in which a ring network is configured and a ring control protocol for loop avoidance operates,
Only when one port of its own transits from blocking state to non-blocking state, or from non-blocking state to blocking state, an identification indicating whether its own port is blocking state or non-blocking state to adjacent nodes Port status notification means for transmitting port status packets for
When the port status packet received from the port status notification means indicates that the adjacent port of the source node is in a blocking state, the adjacent port of the node that has received the packet is placed in an auxiliary blocking state. , An auxiliary blocking transition / cancellation means for canceling the auxiliary blocking state when the source node port indicates a non-blocking state;
A ring network system comprising:

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