KR20140128863A - Method and apparatus of protection switching in rooted multipoint networks - Google Patents

Abstract

A method for operating a plurality of leaf nodes and multipoint connected root nodes are provided. A method for operating according to an embodiment of the present invention includes: a step of transmitting and receiving traffic through the leaf nodes and operation paths; a step of receiving a message which denotes occurrence of failure in a path between the leaf nodes which transmit and receive the traffic; a step of recognizing the occurrence of local failure in the path connected to the leaf node; and a step of transmitting the failure information to the leaf nodes.

Description

[0001] The present invention relates to a method and an apparatus for protection switching in a rooted multipoint connection network,

The present disclosure relates to a protection switching apparatus and method for rapid protection switching from a point-to-multipoint connection network, that is, an alternate path, to a protection path in the event of a failure of a working path in a rooted multipoint connection network.

Currently, in the packet transport network technologies such as OTN, Ethernet, and MPLS-TP, switching management and path protection switching are performed using Automatic Protection Switching (APS) messages for linear protection switching. Linear Protection (ITU-T G.873.1), Ethernet Linear Protection (ITU-T G.8031), MPLS-TP Linear Protection Switching (IETF draft draft-zulr-mpls-tp- ITU-T G.8131.1), and a method for switching status management and path protection switching using protection state control (PSC) messages (IETF RFC6378, ITU-T G.8131.2).

Protection switching is a method for ensuring that traffic is resumed using a different path as soon as a traffic failure occurs due to a network failure. The current linear protection switch sets the operation path and the protection path so as not to meet each other for the traffic flowing in both directions or unidirectional between point-to-point, and normally carries traffic to the operation path, And to carry traffic to the protected path at the time of failure or at the operator's command.

The existing linear protection switching technology uses an APS message or a PSC message for exchanging the state of each node, the selector and the bridge position information required for protection switching between nodes, and the message referred to in this disclosure It is collectively referred to as information transfer messages used for the purpose of protection switching.

In most packet transmission networks, the linear protection switching method creates a virtual connection path between management points, and uses a working path and a protection path as entities, As a protection group. If any connection path is damaged in the set protection group, it is recognized by the management end point (MEP) and protection switching is performed in the automatic protection switching processor.

FIG. 1 is a diagram illustrating an ITU-T G.8031 Ethernet linear protection switching structure without modification. The linear protection switching function is performed by a protection switching processing unit (SNC (Protection Switching Process)), (Bridge / Selector) of the route.

In a rooted multipointed network, a failure can affect multiple leaf nodes simultaneously. If several point-to-point linear protection switching methods are used, the protection recovery processing load at the root node increases as the number of leaf nodes increases, so that a satisfactory recovery time may not be obtained. Therefore, applying the method of switching the whole rooted multipoint connection network at once can avoid that the protection recovery processing load of the root node is affected by the increase of the number of leaf nodes.

According to an aspect of the present invention, there is provided a method for protecting a node from a root node to a root node, the method comprising the steps of: And more particularly to a method and apparatus for protection recovery in a rooted multipoint connection network comprising a plurality of nodes connected to a leaf node.

A method of operating a root node according to an embodiment includes receiving from a first leaf node a message indicating that a failure occurs in a path of the first leaf node among a plurality of leaf nodes transmitting and receiving traffic, Recognizing that a local failure occurs in a path connected to the leaf node, and transmitting the failure information to the plurality of leaf nodes.

In addition, the operation method of the root node may further include transmitting and receiving traffic by switching the operation path to the protection path.

Among a plurality of leaf nodes that transmit and receive traffic through the operational path,

The method of operating a root node according to an exemplary embodiment includes transmitting a first NR message to each of the plurality of leaf nodes and receiving a second NR message from each of the plurality of leaf nodes can do.

The method of operating a root node according to an exemplary embodiment of the present invention may further include transmitting a second SF message indicating failure to the operation path to the plurality of leaf nodes, Lt; RTI ID = 0.0 > leaf node < / RTI >

The method of operating a root node according to an embodiment may further include receiving a third NR message indicating that a failure is eliminated from the first leaf node.

The method of operating a root node according to an exemplary embodiment may further include determining a failure of the first leaf node and entering a Wait To Restore (WTR) state.

The method of operating a root node according to an embodiment may further include a step of switching from the protection path to the operation path, and transmitting a restoration standby message to the plurality of leaf nodes.

Wherein the step of transmitting the second SF message comprises transmitting the second SF message including information indicating that a failure at the root node is false, and the step of transmitting the restoration standby message comprises: It may transmit the restoration standby message including information indicating that it is false.

The method of operating a root node according to an exemplary embodiment of the present invention includes: transmitting the restoration standby message and initiating a restoration wait timer; and transmitting a fourth NR message to the leaf nodes when the restoration wait timer is terminated As shown in FIG.

The fourth NR message may be a message for allowing each of the plurality of leaf nodes to switch from the protection path to the operation path.

The method of operating a root node according to an exemplary embodiment may further include maintaining the traffic transmission / reception to the protection path.

The method of operating a root node according to an exemplary embodiment may further include transmitting an NR message to the plurality of leaf nodes in the absence of an additional request. In the non-restored mode operation, the root node may further include transmitting a Do Not Revert message to the plurality of leaf nodes instead of transmitting the restoration standby message.

The method of operating a root node according to an exemplary embodiment may further include receiving a request including a priority from the plurality of leaf nodes.

The method of operating a root node according to an embodiment may further comprise processing a request from the plurality of leaf nodes based on the priority.

A method of operating a leaf node according to another embodiment of the present invention includes the steps of transmitting / receiving traffic to / from a root node through a route, detecting a failure in the route, detecting a failure in the route, (SF) message, receiving a second SF message indicating failure of the operation path, and transmitting / receiving traffic by switching the operation path to a protection path can do.

According to an embodiment of the present invention, there is provided a method of operating a leaf node, comprising: detecting that a failure occurs in an operation path for transmitting and receiving traffic to and from a root node;

The method comprising: transmitting a first SF message indicating a failure to the operational path; receiving a second SF message indicating that a failure has occurred in the operational path; And transmitting and receiving traffic by switching to a protection path.

The method of operating a leaf node according to an exemplary embodiment may further include detecting that the failure is eliminated, and transmitting a third NR message to the root node indicating that the failure is eliminated.

A method of operating a leaf node according to an embodiment includes receiving a restoration standby message from the root node, receiving a fourth NR message indicating that the failure is resolved, and transferring the protection path to the operation path As shown in FIG.

A method of operating a leaf node according to an embodiment includes receiving a non-recovered message from the root node, receiving a fourth NR message indicating that the failure is resolved, and maintaining the transmission / reception of traffic to the protection path As shown in FIG.

A method of operating a leaf node according to an exemplary embodiment of the present invention includes detecting a failure to be solved, transmitting a restoration standby message to the plurality of leaf nodes, and transmitting a message instructing switching from the protection path to the operation path, And sending a message indicating that the fault has been resolved.

According to an embodiment of the present disclosure, the present invention performs point-to-multipoint protection switching when a failure occurs in a connection node and a path for transmitting and receiving a packet in a rooted multipoint connection.

The present disclosure relates to a protection switching apparatus and method for rapid protection switching to an alternative path in the event of a failure of a transmission / reception path in a point-to-multipoint connection network, i.e., a rooted multipoint connection network.

1 shows an ITU-T G.8031 Ethernet linear protection switching structure.
FIG. 2 shows an example of a network configuration to which a protection switching is applied in a rooted multi-point connection path.
FIG. 3A shows an example in which a failure occurs in a path from a root node to a leaf node in a network to which a protection switching is applied in a rooted multi-point connection path.
3B is a block diagram of a node, such as a root node or a leaf node, according to one embodiment.
4A and 4B are diagrams illustrating a per-tree protection switching process according to an exemplary embodiment in a revertive mode of a 1: 1 mode when a failure occurs as shown in FIG. 3A.
5 is a flowchart of a switching process according to another embodiment.
6A and 6B are timing diagrams illustrating a per-tree protection switching process in a non-revertive mode of a 1: 1 scheme according to another embodiment.
7 is a flowchart of a switching process according to another embodiment.
FIGS. 8A and 8B illustrate another per-tree protection switching process according to the present disclosure in a return mode of a 1: 1 mode when a failure occurs as shown in FIG. 3A.
FIGS. 9A and 9B are diagrams illustrating another per-tree protection switching process according to the present disclosure in a non-restoring mode of a 1: 1 scheme when a failure occurs as shown in FIG. 3A.
10 is an example of a format of a protection switching message according to an embodiment.
Figures 11A-11C are embodiments utilizing a false (F) or forward (P) flag.

The present disclosure is capable of various modifications and various embodiments, and specific embodiments are illustrated and described in the drawings. It should be understood, however, that this disclosure is not intended to be limited to any particular embodiment, but is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

The terms including ordinal, such as second, first, etc., may be used to describe various elements, but the elements are not limited to these terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the second component may be referred to as a first component, and similarly, the first component may also be referred to as a second component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the disclosure. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, wherein like or corresponding elements are denoted by the same reference numerals, and redundant description thereof will be omitted.

The present disclosure relates to a protection switching apparatus and method for rapid protection switching to an alternative path in the event of a packet transmission / reception path failure in a point-to-multipoint manner.

The subject to which this disclosure is directed is a network having point-to-multipoint connections that connects a root node with a plurality of leaf nodes and performs unicast routing from the root node to one particular leaf node ) Traffic, multicast traffic from the root to a particular set of leaf nodes, broadcast traffic from the root node to all leaf nodes, and unicast traffic from the leaf node to the root load. It is a logical network created for the purpose. Networks with these characteristics are called E-Tree (MEF) or rooted multipoint connections (IEEE, ITU-T) in international standards. Meanwhile, a service composed of the above types of traffic is called an E-Tree service or a rooted multipoint connection, and is also referred to as a point-to-multipoint (p2mp) service. In this case, the network to which this disclosure applies may be referred to as a network for supporting E-Tree services or rooted multipoint connection services.

The present disclosure relates to a rooted multipoint connection protection switch, and more particularly, to a multi-point connection protection switching method for a multi- (Point-to-multipoint) networks that are applied in various types of networks such as communication links between access points.

The operational and protection paths referred to in this disclosure may be implemented in a variety of communication networks such as optical transmission networks, Ethernet networks, packet networks, packet routing networks, MPLS label networks, delivery paths, virtual tunnels, Connection is generally referred to as a path in this disclosure for the sake of brevity.

FIG. 2 shows an example of a network configuration to which a protection switching is applied in a rooted multi-point connection path. The solid line and the dotted line represent a bidirectional working tree and a protection tree path between the root node and each leaf node. The root node (Root) connects several leaf nodes (Leaf 1 to Leaf m) and a plurality of paths in the form of a tree for data transmission / reception.

More specifically, in the case of an operation tree, a root node Ro may be connected to a plurality of leaf nodes Leaf 1 through Leaf m via a first intermediate node Intermediate 1. Meanwhile, in the case of the protection tree, the root node Ro may be connected to the leaf nodes Leaf 1 through Leaf m via the second intermediate node Intermediate 2.

The point-to-multipoint path of the connected tree can be managed as a single tree path. For protection switching, two tree paths are required. One is a working tree path and the other is a protection tree path. If a failure occurs, Traffic is switched and communication is resumed.

When the operation tree path of one tree type is a point-to-multipoint connection, unicast, multicast, and broadcast communication are enabled between the root node and each leaf node. The protection tree path for protecting the protection tree is configured in the form of a tree like the operation tree path, and the intermediate node between the root node and the leaf node is divided and set so that the operation tree path and the protection tree path can be protected against any error Complete the pair protection group network tree setup for protection switching. Each node on the tree path can perform data copy for multicast and broadcast communications. As described above, the connection from the root node to the leaf node can be configured as a point-to-multipoint connection, and the connection in the opposite direction can be configured as a multipoint-to-point connection. Also, each tree path can be composed of a combination of point-to-multipoint and multiple point-to-point connections, and the combination may be adapted to the communication protocol for bi-directional communication.

In point-to-multipoint communication, traffic and management message delivery is handled in the form of multicast and broadcast traffic as well as unicast in the direction downstream from the root node to the leaf node, and from the leaf node to the root node Communication in the upstream direction is basically handled in unicast form.

A rooted multi-point connection protection switch is a function that performs protection switching while managing the state between the operation path and the protection path between the root node and one leaf node using the existing point-to-point linear protection switching method. - Per-leaf protection switching method. It manages the entire point-to-multipoint, or multi-point, multi-point connection as operating tree path and protection tree path, and performs protection switching through state management of two tree paths. Per-Tree protection switching method can be operated. These two methods can be set up and operated from the beginning, and can be changed and operated in different ways by the same criteria as simultaneous failure judgment. Here, the per-leaf protection switching method may be a method of switching the operational path to the first leaf node to the protection path when a local failure occurs in the first leaf node. In addition, the per-tree protection switching method may be a method of switching the operation route to all the leaf nodes in the tree, as well as the first leaf node, when the local failure occurs in the first leaf node.

One embodiment of the present disclosure may relate to a per-tree protection switching scheme and relates to a manner of operation of a tri-path protection switching by determining a failure of a connection path or a simultaneous failure determination.

3A shows an example in which a failure (SF) occurs in a path from a root node to a leaf node in a network to which a protection switching is applied in a rooted multi-point connection path. The solid line and the dotted line represent the unidirectional operation tree and the protection tree path between the root node and each leaf node. Because of the nature of per-tree protection switching, the message from the root node to each leaf node is delivered to all leaf nodes, allowing all leaf nodes belonging to the tree path to perform switchover according to the failure and operator command. Messages from each leaf node to the root node can inform the root node of different faults and operational commands, depending on the state of each leaf node.

In the per-tree protection switching, the root node can transfer the entire tree path when the leaf node and the root node recognize the fault occurring within the tree path and when the operation command occurs within the tree path, and the root node Depending on the number of nodes, importance, and simultaneous failure, it is also possible to prevent the entire tree path from being switched due to the recognition of the failure of some leaf node and the root node and the operation command. In one embodiment, it is assumed that the entire tree path is switched by one or more faults and operating instructions in the tree path. The bridge / selector at the root node and the selector / bridge at each leaf node are connected to an Automatic Protection Switching (APS) or Protection State Coordination (PSC) protocol to maintain the same bridge and selector locations. Message. ≪ / RTI >

When a root node first recognizes a failure and initiates a protection switching message exchange at the root node, the pertree protection switching can be switched by a single protection switching message exchange initiated at the root between the root node and all leaf nodes. However, if the leaf node recognizes the failure and the protection switching message exchange is started at a leaf node, a two-step protection switching message exchange process is required for the switching. In the case of a failure propagating in both directions, the root node and the leaf node can recognize protection switching action and message exchange first by recognizing one node at a time or instantaneously, and the failure propagating in one direction starts from either one and is completed It is possible. Hereinafter, the case where the per-tree protection procedure is started by one of the leaf nodes will be mainly described.

3B is a block diagram of a node, such as a root node or a leaf node, according to one embodiment.

As shown in FIG. 3B, the node 300 may include a control unit 310 and a communication unit 320.

The control unit 310 may control the communication unit 320 to perform communication with another node using any one of an operation path and a protection path. The controller 310 may be implemented as an IC chip, a microprocessor, a minicomputer, or the like, and may operate based on a protection switching convention such as APS or PSC protocol, including for example a bridge / selector or a selector / can do. The control unit 310 may control the switching process by analyzing the message received from the communication unit 320 and may generate a message required in the switching process. In addition, the control unit 310 may control the communication unit 320 to transmit the generated message to another node.

The communication unit 320 can perform communication with another node. For example, the communication unit 320 may transmit a message input from the control unit 310 to another node, or may output a message received from another node to the control unit 310. The communication unit 320 may include various communication modules such as an antenna, a combiner / modulator, a frequency processor, a filter unit, and a packet forwarding database. The communication unit 320 can perform communication with another node through one of the operation path and the protection path, and can perform communication with the necessary information while switching traffic between the operation path and the protection path in the protection switching process .

4A and 4B are diagrams illustrating a per-tree protection switching process according to an exemplary embodiment in a revertive mode of a 1: 1 mode when a failure occurs as shown in FIG. 3A.

Here, the 1: 1 scheme may refer to the manner in which traffic is delivered only to either the operating tree path or the protection tree path. FIG. 4A illustrates a message exchange between a leaf node and a root node that detects a failure, and FIG. 4B illustrates a procedure of exchanging messages between a leaf node and a root node, Respectively.

As an example, a message exchanged between nodes includes r / b information related to main status information and a transmitter / receiver (selector) information, and r / b is a transmitter And selector selection information to select traffic according to the protection state of each node as follows.

- r is a Requested Signal, which informs the receiving node whether traffic can be delivered through the protection path and can be selected. If the receiving node has a null signal (0) value, the transmitting node does not transmit (bridging) traffic to the protection path. If the receiving node has a normal traffic signal (1) value, it recognizes that the transmitting node transmits An appropriate Selector path can be selected.

- b is a bridged signal, which is information that indicates whether traffic is transmitted (bridge) to the protection path.

In the 1: 1 scheme, traffic is not transmitted or received through the protection path, which means that traffic is being transmitted or received through the operational path. The contents of r and b are an example of the APS protocol. In the case of other types of protection switching messages, if the value displayed in the r / b field is 0 or a null signal, In the case of a signal, the present invention can be applied by replacing with other types of information using a protection path.

The main status information used in the protection switching message is the Lockout of Protection (LO) state, which is used to transmit and receive traffic only in the operational path, the Signal Fail Protection (SF-P) state in which the fault is detected in the protection path, Forced Switch (FS) state that forcibly transmits and receives traffic to a path, Signal Fail for Working (SF) state that detects a failure in the operational path, Signal Degrade (SD) (WTR) state waiting for operating the timer for a predetermined time until recovery before return, Exercise (EXER) state for testing, response operation by test, (RR) state, a Do Not Revert (DNR) state of transmitting / receiving traffic to / from a protected path by non-restoration, and a No Request (NR) without a specific request or command. An example of the protection switching message composed of the above-mentioned information can be confirmed with reference to FIG.

4A and 4B, per-tree protection switching according to an embodiment will be described.

The root node and the leaf node can transmit and receive a no-request message (hereinafter referred to as NR message) when they are in a normal state (steps 401 and 402). Here, the steady state can refer to a state before a request or a failure occurs, and the root node and the leaf node can transmit / receive traffic through the operational path. When the root node receives the NR message from the leaf node, it can determine that no local failure has occurred in the leaf node. Here, the No Request is a state in which the current node is in the no-request state, that is, there is no valid command or request to the current node. In this case, the bridge and the selector are selecting the operation tree path.

On the other hand, a failure may occur in the operation tree path (step 403).

The leaf node recognizing the failure declares a failure (step 404), and transmits a signal failure (r / b = normal traffic signal) message (hereinafter, SF message) to the root node in a signal fail (Step 405). The bridge and selector of the leaf node can select the protection tree path. SF indicates a state in which the current node recognizes the Signal Fail state, that is, the operation path failure. The SF message may be a message indicating that a failure has occurred. On the other hand, the SF message may include information requesting switching to a protection path. That is, the protection switching message may include fault information of the path, such as the r / b value of the APS protocol, and path information to transmit / receive traffic due to a fault or a request.

When the root node receives the SF (r / b = normal traffic signal) message from the failed leaf node, the remote request SF of the leaf node that recognized the failure is recognized (step 406).

The root node may transmit the SF message (1,1) to the leaf node in which the failure has not occurred (step 407). This is done to remotely request a leaf node that has recognized the failure, and to notify that the failure occurred in the tree when the root node recognized the failure. Each node recognizes the failure, which means that it grasps the local SF state.

The leaf node receives the SF message (1,1) and can grasp the SF state of the root node (step 408).

The root node sends a SF (r / b = normal traffic signal) message (SF (1,1)) to the leaf nodes by the received remote request even though the local SF is not recognized at the root node for the per- And the bridge and the selector can select the protection tree path. Here, (1,1) may be used in combination with a message or the like requesting switching to the protection path. On the other hand, existing point-to-point protection switching techniques that are not pertree protection switching may include configurations that transmit NR (r / b = normal traffic signal) messages if there is no local SF at the root node.

The protection switching process according to an embodiment is for performing per-tree protection switching by the root node, and the root node recognizes its own local SF and generates and transmits a SF (r / b = normal traffic signal) message State (virtual SF state) in which SF (r / b = normal traffic signal) message is generated and transmitted for per-tree protection switching due to the failure of the state and its local SF, It is divided and memorized. That is, for a per-tree protection switching, the per-tree protection switching operation is performed by informing the leaf nodes that the failure has not occurred as if the root node is in the SF state for the failure of any leaf node.

When the failed leaf node receives the SF (r / b = normal traffic signal) message from the root node, it verifies that the per-tree protection switching process has been performed.

In such per-tree protection, the protection switching operation is determined by the request having the highest priority in the target domain. To this end, the root node propagates the highest priority request in the domain by comparing the priority of the remote request from each leaf node to the local request and sending the highest priority request to each leaf node.

Thereafter, the obstacle of the operation path may be eliminated (step 409). The state in which the fault has been eliminated can be called a clear SF (Clear SF). Each node may declare a clear SF (step 410).

The leaf node recognizing the clear SF can maintain the bridge and the selector as the protection tree path by the previously received remote node request SF (far end request) state. The leaf node can transmit NR (r / b = normal traffic signal) message (NR (1,1), NR 1,1, no fault, mixed with a message indicating that the protection tree path is used, etc.) ). The root node may be informed that the SF of the leaf node has been cleared and may enter the WTR (wait to restore) state (step 412). When the WTR returns to the Wait to restore state (Revertive mode), it returns to the operation path from the protection path and waits for a certain period of time And a timer (WTR Timer) is operated for a predetermined period of time. In the meantime, the non-restoration mode may be a mode in which the protection path is continuously used even if the failure occurs in the operational path after the failure occurs in the operational path. When receiving the NR (r / b = normal traffic signal) message from the recognized leaf node, it recognizes that the SF of the leaf node is cleared. In this case, the local SF of the root node is not recognized, (step 413) to enter the WTR state for return from the virtual SF state in which the r / b = normal traffic signal message was transmitted.

The root node is intermixed with the WTR (r / b = normal traffic signal) message (WTR (1,1), WTR 1,1, message Y, message indicating that the fault has been restored and the WTR timer is active and the protection tree path is being used (Step 414).

If there is no additional request at the root node and the WTR timer expires (step 415), the root node goes into the NR state and sends a message of NR (r / b = null signal, mixed with a message informing the use of the operation tree path etc.) 416,419). The bridge and the selector return the path by selecting the operation tree path.

In this case, the root node can forward the NR message to the leaf node if there is no further request. When the node is operating in the non-restored mode, the root node may further include transmitting a Do Not Revert message to the plurality of leaf nodes instead of sending a restoration standby message. Upon receiving the NR (r / b = Null signal) message, the NR (r / b = null signal) message is transmitted by the return mode operation and the operation tree path is selected to return the path (steps 417 and 418). At this point, the recovery process of all tree paths is completed.

Meanwhile, the timing diagram of FIG. 4B illustrates the operation of the root node and the leaf node in which the failure has not occurred.

The root node and the leaf node can send and receive NR messages (steps 421, 422 and 423).

As described above, when the root node receives the SF (r / b = normal traffic signal) message from the failed leaf node, it recognizes the Far End Request SF status of the leaf node that recognized the failure 424). In addition, the root node may send the SF message to the leaf node that has not failed (step 425). The SF message may be a message for allowing a leaf node, which is not aware of a local failure, to perform a switching operation.

When a leaf node that has not received a failure receives a SF (r / b = normal traffic signal) message from the root node, it recognizes the remote request SF state (step 426). The bridge and the selector select the protection tree path, b = normal traffic signal) message (NR (1,1), NR 1,1, a message indicating that there is no fault or request and uses the protection tree path) (step 427). This is the time when traffic switching is performed to the protection tree path.

The root node that receives the NR (r / b = normal traffic signal) message from the leaf node that has not failed confirms that the transfer has been performed by the per-tree protection switching.

As described above, the root node may be informed that the SF of the leaf node has been cleared and may enter the WTR (wait to restore) state (step 428). In addition, the root node can drive the WTR timer.

The root node is mixed with WTR (r / b = normal traffic signal) message (WTR (1,1), WTR 1,1, message Y, message indicating that the fault has been restored and the WTR timer has been activated and the protection tree path has been used) To the leaf node where the failure has not occurred (step 429).

If there are no additional requests at the root node and the WTR timer expires (step 430), the root node goes into the NR state and sends an NR (r / b = null signal) message (steps 431, 434). The bridge and the selector return the path by selecting the operation tree path.

When the leaf nodes in the NR state receive the NR (r / b = Null signal) message, the NR (r / b = Null signal) message is transmitted by the return mode operation and the operation tree path is selected and the path is returned 432,433). At this point, the recovery process of all tree paths is completed.

5 is a flowchart of a transfer process according to an example of a return recovery process in a conventional linear protection transfer method.

Since the operation of steps 501 to 507 in FIG. 5 has been described with reference to FIGS. 4A and 4B, detailed description will be omitted. In the embodiment of FIG. 5, upon failure recovery, the leaf node may enter the WTR mode. More specifically, the leaf node may send a WTR message to the root node (step 508). In addition, the leaf node may transmit the NR message to the root node when the WTR timer expires (step 509). The root node may correspondingly transmit the NR message to the leaf node (step 510). The leaf node receiving the NR message can confirm that the root node has performed the switching. As described above, WTR modes such as WTR message transmission and WTR timer operation can be implemented in various embodiments, each of which is performed by a root node or a leaf node.

6A and 6B are timing diagrams illustrating a per-tree protection switching process in a non-revertive mode of a 1: 1 scheme according to another embodiment. Herein, the non-restoration mode means a mode in which the protection path is maintained even if a failure occurs in the operation path when traffic is transmitted to the protection path by protection switching.

FIG. 6A is a diagram illustrating a procedure of exchanging messages between a leaf node and a root node that detects a failure, and FIG. 6B is a flowchart illustrating a procedure of exchanging messages between a leaf node and a root node, will be.

Before the failure occurs, the root node and the leaf node are in a normal state and transmit / receive NR messages (steps 601, 602 or steps 621, 622, 623). Bridges and selectors are choosing the operating tree path.

The leaf node recognizing the failure transmits the SF (r / b = normal traffic signal) message in the SF state, and the bridge and the selector select the protection tree path (steps 604 and 605) .

A leaf node that does not recognize a fault has no change in state.

When the root node receives the SF (r / b = normal traffic signal) message from the failed leaf node, the remote request SF state for the leaf node that recognized the failure is recognized (step 606 or 624).

Even if the local SF is not recognized at the root node for per-tree protection switching, the received root request causes the root node to send a SF (r / b = normal traffic signal) message to the leaf nodes, (Step 607 or 625).

In this embodiment, the root node is responsible for performing per-tree protection switching, and the root node recognizes its own local SF and generates and transmits a SF (r / b = normal traffic signal) A state in which an SF (r / b = normal traffic signal) message is generated and transmitted (virtual SF state) for per-tree protection switching due to failure of an arbitrary leaf node although the local SF is not recognized, have. That is, for a per-tree protection switching, the per-tree protection switching operation is performed by informing the leaf nodes that the failure has not occurred as if the root node is in the SF state for the failure of any leaf node.

When the failed leaf node receives the SF (r / b = normal traffic signal) message from the root node, it confirms that the per-tree protection switching process has been performed (step 608).

When a leaf node that has not received a failure receives a SF (r / b = normal traffic signal) message from the root node, the far end request recognizes the SF state, and the bridge and the selector select the protection tree path, signal (step 626, 627). This is the time when traffic switching is performed to the protection tree path.

The root node that receives the NR (r / b = normal traffic signal) message from the leaf node that has not failed confirms that the transfer has been performed by the per-tree protection switching.

On the other hand, the obstacle in the operational path can be solved (step 609).

In the unrestored mode, the leaf node can recognize the clear SF (step 610). However, due to the remote request SF state of the previously received root node, the bridge and the selector remain in the protection tree path and notify the leaf node that the SF is cleared by transmitting the NR (r / b = normal traffic signal) message Step 611).

When the root node receives the NR (r / b = normal traffic signal) message from the leaf node recognizing the clear SF (step 612), it recognizes that the remote SF is cleared (step 612) (R / b = normal traffic signal) for the per-tree protection switching, it enters the DNR (do not revert) state for non-restoration in the virtual SF state in which the normal traffic signal is transmitted, (Steps 613, 614, 615 or 628, 629). In the non-restoration mode, the DNR is in a state where the operation path is not obstructed but the traffic transmission / reception is maintained as a protection path in the course of failure in the operational path and recovery from the failure.

On the other hand, the leaf node in which the failure has not occurred can also transmit the NR message to the root node after the protection switching (step 626) (step 627)

When the leaf nodes in the NR state receive the DNR (r / b = normal traffic signal) message, the DNR (r / b = normal traffic signal) message is transmitted (step 616, 630) And the non-restored state is maintained. At this point, the non-restore recovery process of all the tree paths is completed.

7 is a flowchart of a transfer process according to an example of a non-restoration restoration process in a conventional linear protection switching method.

The operation of steps 701 to 707 in Fig. 7 has been described with reference to Figs. 6A and 6B, and thus a detailed description thereof will be omitted. In the embodiment of FIG. 7, upon failback, the leaf node may send a DNR message (step 708). The root node may correspondingly transmit the DNR message to the leaf node (step 709). As described above, the DNR message transmission is possible to implement various embodiments in which the root node or the leaf node performs, respectively.

FIGS. 8A and 8B illustrate another per-tree protection switching process according to the present disclosure in a return mode of a 1: 1 mode when a failure occurs as shown in FIG. 3A. FIG. 8A illustrates a message exchange between a leaf node and a root node that detects a failure, and FIG. 8B illustrates a procedure of exchanging messages between a leaf node and a root node, will be.

Before the failure occurs, the root node and the leaf node are in a normal state and transmit / receive NR messages (steps 801, 802 or 821, 822, 823). Bridges and selectors are choosing the operating tree path.

The leaf node recognizing the failure transmits the SF (r / b = normal traffic signal) message in the SF state (step 804), and the bridge and the selector select the protection tree path (Step 805).

A leaf node that does not recognize a fault has no change in state.

When the root node receives the SF (r / b = normal traffic signal) message from the failed leaf node, the remote request SF state for the leaf node that recognized the failure is recognized (step 806 or 824).

Since the local SF is not recognized at the root node for the per-tree protection switching, the failure at the root node sends an SF (r / b = normal traffic signal) message containing the information of Fake to the leaf nodes (Step 807 or 825). The bridge and selector select the protection tree path.

Here, the SF message including the false information may mean that the actual SF is generated at the root node and not transmitted, but is declared as SF in the form of false information for per-tree protection switching. The leaf node received through the false information may determine that the leaf node is not an actual request but a false node (step 808). More specifically, the root node does not include information indicating that the fault is true in the actual root node. If the root node does not recognize the fault and receives a fault notification from any leaf node, And the like.

The above process is for performing the per-tree protection switching by the root node according to the present disclosure, and the root node recognizes its own local SF and generates and transmits a SF (r / b = normal traffic signal) (Normal SF traffic) message for the per-tree protection switching due to the failure of any leaf node although its own local SF is not recognized. . In other words, for a per-tree protection switching, a failure of any leaf node is notified to the leaf nodes where no failure has occurred as if the root node is in the SF state, .

It is confirmed that the per-tree protection switching process is performed when the failed leaf node receives a false SF (r / b = normal traffic signal) message from the root node.

The leaf node, which has not failed, recognizes a false remote request SF state (step 826) upon receipt of an SF (r / b = normal traffic signal) from the root node and a false message (step 826) Selects a protection tree path and transmits an NR (r / b = normal traffic signal) message (step 827). This is the time when traffic switching is performed to the protection tree path.

The root node receives the NR (r / b = normal traffic signal) message from the leaf node where the failure has not occurred (step 827), and verifies that the transfer has been performed by the per-tree protection switching.

On the other hand, the obstacle can be eliminated (step 809).

The leaf node recognizing the fault recognizes the clear SF (step 810). Since the leaf node knows that it is a previously received root node false remote request SF state, there is no real obstacle in the current tree path. Therefore, it enters the WTR state to return to drive the WTR timer and transmits a WTR (r / b = normal traffic signal) (Step 811).

When the root node receives the WTR (r / b = normal traffic signal) message from the leaf node, it can recognize that the failure of the leaf node has disappeared (step 812). The root node sends a false WTR (r / b = normal traffic signal) message to the leaf nodes for the per-tree protection switching (steps 813, 814, 828, 829). In this case, the false WTR message is actually caused by the WTR timer being operated for the per-tree protection switching due to the fact that the WTR timer is actually operated but not due to the failure of the own node and the failure of the leaf node is eliminated.

When the leaf nodes that have never experienced a failure receive a false WTR (r / b = normal traffic signal), the NR (r / b = normal traffic signal) message transmission state remains unchanged.

If the fault disappears and the leaf node in the WTR state has no additional request and the WTR timer expires (step 815), the NR state is entered and a NR (r / b = null signal) message is transmitted (step 816). The bridge and the selector return the path by selecting the operation tree path.

When a root node receives an NR (r / b = null signal) message, it stops transmitting a false WTR (r / b = normal traffic signal) message and transmits a NR (r / b = null signal) And the path is returned by selecting the operation tree path (steps 817, 818 or 830, 831). The leaf node receiving the NR message can also confirm that the root node has also switched to the operational path (step 819).

When the leaf nodes in the NR state receive the NR (r / b = Null signal) message, the NR (r / b = Null signal) message is transmitted by the return mode operation and the operation tree path is selected and the path is returned 832,833). At this point, the recovery process of all tree paths is completed. The root node receiving the NR message can confirm that other leaf nodes have also switched to the operational path due to the path information in the message (r / b in APS) (step 834).

FIGS. 9A and 9B are diagrams illustrating another per-tree protection switching process according to the present disclosure in a non-restoring mode of a 1: 1 scheme when a failure occurs as shown in FIG. 3A. FIG. 9A illustrates a procedure of exchanging messages between a leaf node and a root node that detects a failure, and FIG. 9B illustrates a procedure of exchanging messages between a leaf node and a root node, will be.

Before the failure occurs, the root node and the leaf node are in a normal state and transmit / receive NR messages (steps 901, 902 or 921, 922, 923). Bridges and selectors are choosing the operating tree path.

If a failure occurs in the operation tree path (step 903), the leaf node recognizing the failure transmits SF (r / b = normal traffic signal) message in the SF state, and the bridge and the selector select the protection tree path (steps 904 and 905) . A leaf node that does not recognize a fault has no change in state.

When the root node receives the SF (r / b = normal traffic signal) message from the failed leaf node, the remote request SF state for the leaf node that recognized the failure is recognized (step 906 or 924).

Even if the local SF is not recognized at the root node for the per-tree protection switching, the root node transmits the SF (r / b = normal traffic signal) message to the leaf nodes, and the bridge and the selector select the protection tree path (at step 907 Or 925).

The process described above is performed by the root node to perform per-tree protection switching according to an embodiment, and the root node recognizes its own local SF, and the root node includes information indicating that it is not Fake, (R / b = normal traffic signal) message to the leaf nodes, and the bridge and the selector select the protection tree path. That is, it is determined that an SF (r / b = normal traffic signal) message is sent and the actual root node detects the occurrence of the SF, and the leaf node receiving the SF message can determine that the local SF of the root node is detected.

This process is for performing per-tree protection switching by the root node according to the present disclosure, and the root node recognizes its own local SF and generates and transmits a SF (r / b = normal traffic signal) message. (SF) state for generating per-tree protection switching (r / b = normal traffic signal) message by the failure of an arbitrary leaf node although its own local SF is not recognized, I remember it. In other words, for per-tree protection switching, per-tree protection switching is activated by informing the leaf nodes that the failure has not occurred, such as the state of the root node in the fault state of any leaf node, do.

It is confirmed that the per-tree protection switching process is performed when the failed leaf node receives the SF (r / b = normal traffic signal) message from the root node.

When a leaf node that has not failed is recognized as SF (r / b = normal traffic signal) from the root node and a false message is received, the bridge and the selector recognize the remote requesting SF state. And transmits a NR (r / b = normal traffic signal) message (steps 926 and 927). This may be the time at which traffic switching is performed on the protection tree path.

The root node that receives the NR (r / b = normal traffic signal) message from the leaf node that has not failed confirms that the transfer has been performed by the per-tree protection switching.

On the other hand, the obstacle in the operational path can be eliminated (step 909).

In the non-revertive mode, the bridge and the selector remain in the protection tree path and the DNR () is not changed because the leaf node recognizing the clear SF knows that it is the false remote request SF state received previously. r / b = normal traffic signal) message to inform the leaf node that the SF has been cleared (step 911).

When the root node receives the DNR (r / b = normal traffic signal) message from the leaf node that recognized the clear SF, it recognizes that the far end request SF is cleared (step 912) B) normal traffic signal (DN) (r / b = normal traffic signal) message for the per-tree protection switching, (Steps 913, 914, 915, or 928, 930). The leaf node may send the DNR message to the root node (step 916).

When the leaf nodes in the NR state receive the DNR (r / b = null signal) message as shown in the right drawing of FIG. 9, the DNR (r / b = normal traffic signal) message is transmitted by the non- Select the path to keep the non-restored state. At this point, the non-restoration restoration process of all the tree paths is completed (step 929).

When the above example is applied to the 1 + 1 scheme, the selection for the bridge is always selected as b = Normal traffic signal and only the selection for the selector is operated in the same manner as described above. In the 1 + 1 scheme, both the operation path and the protection path are transmitted to the transmitting side, and the receiving side selects either one.

End-to-end commands such as a lockout command, a force switch command, and a manual switch command are also transmitted from a leaf node to an End When the root node receives a far-end request message indicating that the -to-End command has been applied, it recognizes the far end request state. If the far-end request command recognized by the root node for the per-tree protection transfer is valid in priority, the root node is notified of the end-to-end command Sends a message to the leaf nodes and selects the appropriate tree path for the end-to-end command.

This process is for the per-tree protection switching to be performed by the root node according to one embodiment. That is, for the application of an end-to-end command of any leaf node for a per-tree protection transfer, the root node informs the leaf nodes as if the same end-to- - Make the tree protection switch operate.

On the other hand, the root node and each leaf node have a protection switching process. The protection switch message is exchanged between the root node and each leaf node to adjust their bridge and selector positions.

A protection switching message (which may be mixed with an APS message and an APS protocol message as an embodiment) may be transmitted between the root node and each leaf node. The protection switching message created by the root node is delivered to all leaf nodes, but the protection switching message created by each leaf node is delivered only to the root node. The protection switching message delivered from each leaf node must be identified by the root node. This can be done by assigning a different ID (VID for Ethernet) for the protection path in the direction from each leaf node to the root node. On the other hand, if all the leaf nodes use the same ID (same VID for Ethernet) for the protection path, the protection switching message includes information (e.g., node ID) that allows the root node to identify the source of the protection switching message shall.

10 is an example of a format of a protection switching message in Ethernet according to an embodiment.

DA is Ethernet MAC destination address, SA is Ethernet MAC destination address, Type / length is Ethernet frame length or Ethernet type, User Priority, Canonical Format Information, and VID is VLAN information used in IEEE 802.1Q / VLAN

Etype contains information about the types of Ethernet messages coming in the following areas.

MEL, Version, Opcode, Flags, and TLV Offset are information fields for Y.1731 Ethernet OAM. If Opcode is 39, APS message will be sent to the next area.

Request / State (protection switching request and status information generated in each node), Protection Type (protection switching type related to whether 1: 1, 1 + 1, unidirectional, bidirectional or APS message is used), Requested Signal, Bridged Signal, T (Bridge Type: Information on whether the bridge used for transmission is a selector bridge or a broadcast bridge), Reserved, and the like are areas of each field of the protection switching APS message.

The first 4 bytes of the protection switch message are the same as the APS message of ITU-T G.8031, but the IETF PSC message may be applied. In the present disclosure, an ID of a node that transmits a protection-switching message is added to identify a leaf node that has transmitted a message from the root node. The node ID may use a 6-byte leaf node MAC address as shown in FIG. 10, or may use another type of discriminator of arbitrary size. Also, the node ID information may utilize the reserved area in the existing protection switching message.

 The node ID in the protection switching message may be omitted if the protection switching message from the leaf node to the root node is transmitted through the unique channel or the transmission leaf node can be distinguished from the frame header information including the protection switching message.

(Fake, F) information indicating that the protection switching message to be transferred from the root node to the leaf node is not the state of the root node (or a high priority request among the protection switching messages received from the leaf nodes by the root node (Propagation, P) information indicating that the leaf node is being delivered in place of the leaf node) may be included in the protection switching message in the form of a flag of 1 bit, and the F or P flag may be set to a reserved area in the conventional protection switching message It can be used or displayed at arbitrary positions, and F and P can be used in both, or both can be used by using only one.

The role of the false (F) or forward (P) field according to the present disclosure is not only useful for the operation of the WTR timer described above, but also for the arbitration of a request of the same priority occurring at different leaf nodes It can also be used as information.

In the G.8031 standard, an MS under manual command means manual switching to the protection path, MS-W means manual switching to the operating path, and MS is also referred to as MS-P. MS commands and MS-W commands have the same priority and operate on the principle of "first-come, first-served". That is, if an input request is accepted first and then an operation is performed, then another request of the same priority is not accepted. If two different requests are input simultaneously, the MS-W instruction takes precedence. Here, "concurrent" means the time from when the local node receives a response to the command issued by the local node. For example, after an MS command is inputted from an operator at one node and the MS command is executed at the node, the MS command is transmitted to the counterpart node through the protection switching message, and the response (NR1,1) The MS-W command is assumed to be concurrently entered on both nodes.

In the protection switching method in the RMP network according to the present disclosure, the root node receives the MS command (MS (1,1)) from one leaf node and replaces MS (1,1) with NR To all leaf nodes. Therefore, the leaf node transmitting the MS (1,1) recognizes the MS (1,1) received from the root node as a response and judges that the MS command is accepted. However, at the same time, when the MS-W command (MS (0,0)) is dropped at another leaf node, the leaf node transfers the MS (0,0) to the root node. However, since the root node has already received the requested MS command from another leaf node, the MS-W command is ignored and the MS (1, 1), which means manual switching to the protection path, is sent to all the leaf nodes . At this time, since the leaf node receiving the MS-W command receives another request (MS (1,1)) other than the response to the MS (0,0) sent by the MS, the leaf node judges that different requests of the same priority are simultaneously issued And keeps the MS-W command. Therefore, all the leaf nodes except for the leaf node and the leaf node where the MS-W command is issued transfer the traffic to the protection path by the MS command, and only the leaf node holding the MS-W command maintains the working path, The traffic of the mobile terminal is disconnected.

Figures 11A-11C illustrate one embodiment of the present disclosure for solving the above-mentioned problems using a false (F) or forward (P) flag. 11A to 11C are diagrams illustrating an example of a manual switch to protection (MS) command and a manual switch to working (FIG. 11A) in leaf nodes 1 and 2 in an RMP network including a plurality of leaf nodes (L1 ... Ln) MS-W) command is concurrently issued. 11A to 11C, it is assumed that only the P flag is used.

The root node can send and receive NR messages with the leaf node 1 (steps 1101 and 1102). In addition, the root node can send and receive NR messages to the leaf node 2 (steps 1111 and 1112). Also, the root node can send and receive NR messages to the leaf node 3 (steps 1121 and 1122).

Meanwhile, the leaf node 1 can receive the MS command (step 1103). In addition, the leaf node 2 can receive the MS-W command (step 1114). Here, the MS command may be a manual transfer request command of the protection path as described above, and the MS-W command may be a manual transfer request command to the operating path.

Leaf node 1 may switch traffic to the protection tree (step 1104) and then send the MS (1,1) request to the root load (step 1105).

On the other hand, the leaf node 2 may maintain the traffic as a working tree (step 1114), and then transmit the MS (0,0) request to the root node (step 1115).

If the MS (1,1) received from the leaf node in the root node is processed first (1106), the root node accepts the request, and the traffic is switched to the protection tree. Then, the P flag is set in the protection- And transmits the received MS (1,1) request to all the leaf nodes (steps 1107, 1117, and 1123).

If the MS (0, 0) is received from the leaf node 2 thereafter, the root node has already accepted the MS (1,1) request and can ignore the MS (0,0) request (step 1116).

When the leaf node 1 receives the MS (1,1) request with the P flag set from the root node, it regards the request as a response and maintains the current state (step 1108).

The leaf nodes 3 to n accept the MS (1,1) request, transfer the traffic to the protection tree (step 1124), and transmit the NR (1,1) in response to the root load (step 1125).

When the leaf node 2 receives the MS (1,1) request with the P flag set from the root node, it judges that the root node has accepted the request of another leaf node except for itself, The command may be withdrawn (step 1118). In addition, the leaf node 2 may transmit the NR (1,1) message to the root node (step 1118), and the root node may receive it (step 1119).

On the other hand, the root node can then send to all leaf nodes with MS (1,1) request (steps 1110, 1120, 1126)

The apparatus described above may be implemented as a hardware component, a software component, and / or a combination of hardware components and software components. For example, the apparatus and components described in the embodiments may be implemented within a computer system, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA) A programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For ease of understanding, the processing apparatus may be described as being used singly, but those skilled in the art will recognize that the processing apparatus may have a plurality of processing elements and / As shown in FIG. For example, the processing unit may comprise a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as a parallel processor.

The software may include a computer program, code, instructions, or a combination of one or more of the foregoing, and may be configured to configure the processing device to operate as desired or to process it collectively or collectively Device can be commanded. The software and / or data may be in the form of any type of machine, component, physical device, virtual equipment, computer storage media, or device , Or may be permanently or temporarily embodied in a transmitted signal wave. The software may be distributed over a networked computer system and stored or executed in a distributed manner. The software and data may be stored on one or more computer readable recording media.

The method according to an embodiment may be implemented in the form of a program command that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions to be recorded on the medium may be those specially designed and configured for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (20)

Receiving a message indicating that a failure occurs in a path of the first leaf node from a first leaf node among a plurality of leaf nodes transmitting and receiving traffic;
Recognizing that a local failure occurs in a path connected to the first leaf node; And
Transmitting the fault information to the plurality of leaf nodes
Gt; a < / RTI > root node. The method according to claim 1,
Transmitting and receiving traffic by switching the operation route to the protection route
Further comprising the step of: The method according to claim 1,
Transmitting a first NR message (No Request message) to each of the plurality of leaf nodes; And
Receiving a second NR message from each of the plurality of leaf nodes
Gt; a < / RTI > root node. The method according to claim 1,
Wherein the step of transmitting the fault information to the plurality of leaf nodes further comprises transmitting a second SF message indicating that a failure occurs in the path of the first leaf node to the plurality of leaf nodes,
Wherein the second SF message is a message for allowing each of the plurality of leaf nodes to switch from a working path to a protection path. The method according to claim 1,
Receiving a third NR message indicating failure from the first leaf node;
Further comprising the step of: 5. The method of claim 4,
Determining that the fault at the first leaf node is eliminated; And
Entering the Wait To Restore (WTR) state
Further comprising the step of: The method according to claim 6,
Switching from the protection path to the operational path
Further comprising the step of: The method according to claim 6,
Transmitting a restoration standby message to the plurality of leaf nodes
Further comprising the step of: 8. The method of claim 7,
Wherein the step of transmitting the second SF message comprises transmitting the second SF message including information indicating that a failure at the root node is false,
Wherein the step of transmitting the restoration standby message comprises transmitting the restoration standby message including information indicating that the failure of the root node is false. 8. The method of claim 7,
Transmitting the restoration standby message and initiating a restoration standby timer; And
Transmitting the fourth NR message to the plurality of leaf nodes when the restoration wait timer is terminated
Further comprising the step of: 11. The method of claim 10,
Wherein the fourth NR message is a message that causes each of the plurality of leaf nodes to switch from a protection path to a working path. The method according to claim 6,
Maintaining the traffic transmission / reception to the protection path
Further comprising the step of: 13. The method of claim 12,
Transmitting the restoration standby message and initiating a restoration standby timer; And
Transmitting a Do Not Revert message to the plurality of leaf nodes when the restoration wait timer expires;
Further comprising the step of: 14. The method of claim 13,
Wherein the non-recovery message is a message indicating failure of the first node. The method according to claim 1,
Receiving a request including a priority from the plurality of leaf nodes
Further comprising the step of: 16. The method of claim 15,
Processing a request from the plurality of leaf nodes based on the priority
Further comprising the step of: Detecting that a failure occurs in an operation path for transmitting and receiving traffic to and from the root node;
Transmitting a first SF message (Signal Fail message for working path) indicating that a failure occurs in the operation path;
Receiving a second SF message indicating a failure in the operational path; And
Transmitting and receiving traffic by switching the operation path to a protection path
Gt; a < / RTI > leaf node. 18. The method of claim 17,
Detecting that the fault has been eliminated; And
Transmitting a third NR message to the root node indicating that the failure is to be resolved
Further comprising the step of: 18. The method of claim 17,
Receiving a restoration standby message from the root node;
Receiving a fourth NR message indicating that the fault is to be solved; And
Switching the protection path to the operational path
Further comprising the step of: 18. The method of claim 17,
Receiving a non-recovery message from the root node;
Receiving a fourth NR message indicating that the fault is to be solved; And
Maintaining the traffic transmission / reception to the protection path
Further comprising the step of:

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