JP2002190818A - 1: 1 protection method for WDM optical communication system, system to which the method is applied, node to which the method is applied, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a 1:1 protection system that can protect faults on a ring. SOLUTION: A fault detection section 506 detects the occurrence of a 2nd fault, a protection control section 513 receives the detection result, transmits a notice signal to an opposite node, a protection control section of the opposite node receiving the notice signal returns a switch-back notice to the node whose fault is detected, and the protection control section 513 of the node whose fault is detected that receives the notice switches back 2:1 optical switches 509-512 of a reception section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to wavelength division multiplexing (WD).
Using M: Wavelength Division Multiplexing) technology, multiple nodes are connected by an optical transmission medium (optical fiber),
The present invention relates to a protection scheme for a wavelength division multiplexing optical communication system that transfers packets on a wavelength path. In particular, the present invention relates to a 1: 1 protection method when a plurality of faults occur on the same ring, a node and a system to which the method is applied, and a storage medium.

[0002]

2. Description of the Related Art With the spread of the Internet and the like, the speed of a backbone network is increasing. As a technique for further increasing the capacity of a network using optical fibers, there is WDM. Although the capacity of an optical fiber can be dramatically increased by the WDM technique, the effect when the optical fiber is cut becomes large. Therefore, a ring type is widely used as an efficient backbone network structure in consideration of reliability at the time of failure. As a development of such a ring network, a network in which traffic is concentrated on a central office and wavelength change is unnecessary, for example, a network in which a fiber is a ring but a wavelength path is a star is considered. FIG. 1 shows an example of the network configuration. Between the center node (hereinafter, CN) and the remote node (hereinafter, RN), a working path based on a branch wavelength unique to each RN is established in one direction as viewed from the CN. The protection path (not shown) extends in the opposite direction to the working path and at the same wavelength as the working path.

One of the ring network protection schemes is the 1: 1 scheme. This is a method in which one protection path is prepared for one working path, and has a feature that low-priority extra traffic can flow through the protection path in a normal state.

FIG. 2 shows a normal flow of traffic in the 1: 1 system between the CN and the node A. In the figure, a solid line indicates a working path, and a dotted line indicates a protection path. Here, from node A to CN
It is assumed that a fault has occurred in the fiber going to. At this time,
The working path between the CN and the node A is simultaneously switched to the protection path in both directions so as to avoid a failure point as shown in FIG. Specifically, the transmitting unit causes the same signal to flow through both the working path and the protection path, and the receiving unit selects reception from the protection path.

[0005]

However, when a second failure occurs in another span on the same ring, traffic from the CN to the node A as shown in FIG. There was a problem that it could not be reached at all. That is, it is assumed that a second failure has occurred between the node B and the node C as shown in FIG. This second failure is caused by the node B as shown in FIG.
Is detected by The node B notifies the center node CN via the node C of the occurrence of the failure. However, although the center node CN transmits a failure notification to the node A, in the node A, when the first failure occurs, the optical switch is switched so as to select reception from the protection path. Even if the failure notification is transmitted via the working path, the node A cannot receive it.

The present invention has been made in view of the above circumstances, and has as its object to simultaneously switch traffic to a protection path in both directions at the time of the occurrence of a first failure, and to provide a second path in the same ring as the ring in which the first failure has occurred. In the event of a failure, the protection path can be protected against multiple failures on the same ring by switching back to the working path in one direction after switching to the protection path. And a storage medium.

[0007]

In order to achieve the above object, a traffic topology is of a star type, and a plurality of remote nodes for inserting / branching only specific branch wavelengths, and a branch between each remote node. A two-fiber network in which a wavelength path is set up at the wavelength and a center node that is the center node of the traffic topology, and the working path is set up in one direction as seen from the center node, and the protection path is set up in the opposite direction to the working path. In a ring network, the 1: 1 protection method of the wavelength division multiplexing optical communication system according to the present invention switches traffic to the protection path simultaneously in both directions when a first failure occurs on a working path, and the same ring as the ring in which the first failure has occurred. Protection path in the event of a second failure A one-way of which was replaced Ri, characterized in that it switched back to the working path.

In a point-to-point network comprising a working path and a protection path, the 1: 1 protection method of the wavelength division multiplexing optical communication system of the present invention simultaneously transmits traffic in both directions when a first failure occurs on the working path. Switching to a protection path, and when a second failure occurs on a protection path in a direction opposite to that of the first failure, one direction of the switching to the protection path is switched back to the working path.

In addition, the traffic topology is of a star type, and a plurality of remote nodes, each of which inserts / branches only at a unique branch wavelength, and a wavelength path is established between each remote node at each branch wavelength, and the center of the traffic topology is established. In a two-fiber ring network including a center node serving as a node, a working path extending in one direction as viewed from the center node, and a protection path extending in a direction opposite to the working path, the wavelength multiplexing optical communication of the present invention is performed. The system comprises: first fault detecting means for detecting a first fault on a working path; and when the first fault is detected on the working path by the first fault detecting means, traffic is simultaneously protected in both directions. Means for switching to a path and a ring in which the first fault has occurred And second failure detecting means for detecting a second failure in the same ring, by the second fault detection means, the same ring as the ring first failed second
Means for switching back to the working path when switching to the protection path when the failure is detected,
It is characterized by having.

In a point-to-point network comprising a working path and a protection path, the wavelength division multiplexing optical communication system according to the present invention comprises a first fault detecting means for detecting a first fault on the working path; Means for switching traffic to the protection path in both directions simultaneously when the first failure is detected on the working path by the first failure detection means;
Means for detecting a second fault on a protection path in a direction opposite to the first fault, and the second fault detecting means detecting a second fault on a protection path in a direction opposite to the first fault Means for switching back to the working path in one direction of switching to the protection path.

Further, only the unique branch wavelength is inserted.
A wavelength path is established between each of a plurality of branching remote nodes and each remote node at a branch wavelength. The center node is a central node of a traffic topology. In a two-fiber ring network where the protection path is extended in the opposite direction to the working path,
The node for a wavelength division multiplexing optical communication system according to the present invention includes a first OADM (Optical Add Drop Multip
lexer) and a second OADM for the protection path.
A first failure detecting unit connected to the first OADM and generating a first failure on a working path;
A first 2: 1 optical switch connected to the DM and the second
A second 2: 1 optical switch connected to the OADM, third and fourth 2: 1 optical switches connected to the output of the first fault detector, and a ring in which the first fault has occurred. A second fault detector for detecting that a second fault has occurred on the same ring, fifth and sixth 2: 1 optical switches connected to the output of the second fault detector, First and second failure detection units, and first, second, third, fourth, fifth,
When the first failure detection unit detects a first failure on a working path, the first optical switch is connected to a bridge state, and the second optical switch is connected to a second, third, and second switches. The fourth, fifth and sixth 2: 1 optical switches are switched to switch the traffic to the protection path simultaneously in both directions, and the second failure detecting means uses the second ring on the same ring as the ring where the first failure has occurred. When a failure is detected, by switching back the third, fourth, fifth, and sixth 2: 1 optical switches, a protection control unit that switches back to the working path in one direction after switching to the protection path; It is characterized by having.

In the storage medium of the present invention, the traffic topology is a star type, and a plurality of remote nodes for inserting / branching only unique branch wavelengths, and a wavelength path at each branch wavelength between each remote node. And a center node serving as a central node of the traffic topology, a working path is extended in one direction as viewed from the center node, and a protection path is extended in a direction opposite to the working path. (1) A storage medium storing a program for implementing a protection function, comprising: a procedure for simultaneously switching a traffic to a protection path in both directions when a first failure occurs on a working path; Second failure on the same ring as Sometimes, a step of switching back the way of switching to the protection path to the working path,
Is stored.

[0013] Further, the storage medium of the present invention has a Point to Poi comprising a working path and a protection path.
In an nt network, a computer has a procedure for simultaneously switching traffic to a protection path in both directions when a first failure occurs on a working path;
When a second fault occurs on the protection path in the direction opposite to the fault described above, a procedure for switching back to the working path in one direction after switching to the protection path is stored.

According to the present invention, the failure detector detects the occurrence of the second failure, the protection controller receives the detection, sends a notification signal to the partner node, and controls the protection of the partner node that has received the notification signal. The switch sends back the switch switchback notification to the failure detection node, and the protection processing unit of the failure detection node that received the notification switches back the 2: 1 optical switch of the receiving system. Protection can be made possible even if the error occurs.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

FIG. 1 is a diagram showing a case of a plurality of faults according to the present invention.
FIG. 2 is a configuration diagram illustrating an embodiment of a node to which one protection method is applied. As shown in the figure, an OAD that inserts / branches only the branch wavelength specific to each remote node (RN)
M (Optical Add Drop Multiplexer) (0 series) 501 and O
The ADM (system 1) 502 is connected to a working path and a protection path, respectively. In this embodiment, the system that passes the working data is called system 0, and the system that passes the protection data is called system 1. Specifically, in FIG. 9, the path indicated by the solid line is the 0-system, and the path indicated by the broken line is the 1-system.

A 2: 1 optical switch 507 of the transmission unit (0 system)
Is connected to the working path of the OADM (system 0) 501, and the 2: 1 optical switch 508 of the transmission unit (system 1)
It is connected to the protection path of DM (0 system) 501. Further, the branch wavelength 503 of the protection path is set.
Is input to the failure detection unit 505, and the branch wavelength 504 of the working path is input to the failure detection unit 506. One of the outputs from the failure detection unit 505 is connected to the 2: 1 optical switches 509 and 510 of the reception unit (0 system), and the other is connected to the protection control unit 513. One of the outputs of the failure detection unit 506 is connected to the 2: 1 optical switches 511 and 512 of the reception unit (system 1), and the other is connected to the protection control unit 513. Protection control unit 5
13 has a memory 515. This memory 515 stores topology information to be described later and a control program (protection control unit of CN) shown in the flowchart shown in FIG. 2 and a program (protection control unit of RN) shown in the flowchart shown in FIG.

2: 1 optical switches 507 to 512 in FIG.
Indicates a normal state by a solid line and a protection state by a dotted line. In a normal state, traffic transmitted to the working path is inserted from the transmitting unit (0 system) through the 2: 1 optical switch 507 by the OADM (0 system) and transmitted to the partner node. Traffic from the working path to the node is branched by OADM (system 0) (branch wavelength 5).
03), a failure detection unit 505, a 2: 1 optical switch 509,
The signal reaches the receiving unit (0 system) via 510.

In the embodiment of the present invention, the number of nodes will be described as 4 (CN, A, B, C) for convenience.
The wavelengths of the paths established between the CN and the nodes A, B, and C are λa, λb, and λc, respectively.

FIG. 2 shows a protection control unit 51 of the CN.
3 is a flowchart illustrating control of the RN, and FIG. 3 is a flowchart illustrating control of the protection control unit 513 of the RN. FIG. 4 is a sequence chart showing the operation between nodes when the first failure occurs. In FIG. 4, a solid line indicates a data flow of the node A, a broken line indicates a data flow of the node B, and a node C indicates a data flow of a dashed line. In addition, "bridge" in the figure is
This means an operation of flowing the same signal in both directions (working path and protection path). Further, “switch” means that the data from the protection side is adopted on the reception side.

Hereinafter, the 1: 1 protection method for a plurality of failures according to the present invention configured as described above will be described with reference to FIGS. In the following description, the protection control units of CN and RN will be described as a protection control unit 513 and a protection control unit 517, respectively.

Now, as shown in FIG.
It is assumed that the first failure has occurred in the working path toward N.

The CN is in an event waiting state in step S1101 of the flowchart shown in FIG. 2, and detects the occurrence of an event in this step because a failure has occurred. That is, when a failure occurs at the position shown in FIG.
Traffic going to is affected. As a result, CN
The working path side failure detecting unit 505 of λa, λb,
Detects failures at three wavelengths of λc (FIG. 1 shows a configuration for one wavelength, and in a CN, the configuration shown in FIG. ). Then, the working path failure detection unit 505
Indicates that the failure has been detected by the protection control unit 513.
Notify.

In step S1102, the protection control unit 513, having received the notification from the failure detection unit 505, detects the failure at wavelengths λa, λb, and λc. Understand that there is. For example, λa can be received and λb
And λc cannot be received, it is recognized that a failure has occurred on the path from node B to node A.
Further, when only λc cannot be received, it is recognized that a failure has occurred on the path from the node B to the node C. Further, when none of λa, λb, and λc can be received, it is recognized that a failure has occurred on the path from the node A to the CN. As a result, the protection control unit 513
Are the nodes A, B,
Let C transmit a failure notification SF (Signal Fail) (working side). As a result, the SF is transmitted to each node from both directions of the working path and the protection path. This is shown in the sequence chart of FIG. In the figure, CN, A, B, and C are center nodes C, respectively.
N and remote nodes (RN) A, B and C. When the CN detects a failure (S601), the failure notification SF
To the nodes A, B and C, respectively.

On the other hand, the nodes A, B, and C receive the notification SF in step S1201 in the flowchart of FIG. Then, in step S1208, the protection control unit 517 performs bridge & switch. That is, control is performed so that the same signal is transmitted to the 0-system and 1-system transmission units, and the same signal is sent to both the working path and the protection path. This is shown by S602 in the sequence chart in FIG. In particular,
Upon receiving the notification, the protection control unit 517 sets the 2: 1 optical switch 507 of the transmission system to a bridge state (transmits the same signal to both outputs of the optical switch 507), and switches the optical switch 508 to the dotted line side. Then, all the 2: 1 optical switches 509-512 of the receiving system are switched to the dotted line side.

Then, the nodes A to C that have switched the switches receive the response signal in step S1209 in FIG.
(ack) is returned to the node CN.

On the other hand, the CN receives the response signal (ack) in step S1104 in FIG. And CN
In step S1105, the received wavelength br
Perform idge & switch. This situation is shown by S603 in the sequence chart of FIG. Specifically, the protection control unit 513 of the CN switches the optical switch 508 to the dotted line side, and sets the 2: 1 optical switch 509-51 of the receiving system.
2 are all switched to the dotted line side. Thereafter, the CN returns an acknowledgment (ack) to the nodes A to C at the wavelength.

On the other hand, each of the nodes A, B, and C receives a response (ack) from the CN in step S1210 in FIG. 3, and completes the processing.

On the other hand, the CN determines in step S1107 of FIG.
, When the responses (ack) are received from all the nodes, the process is completed. Thereby, protection against the first failure is completed.

Subsequently, it is assumed that a second failure has occurred in the same ring as the ring in which the first failure has occurred and in a different place (between nodes B and C in this embodiment).
FIG. 5 shows an operation sequence diagram between the nodes at this time.

In step S 1201 of FIG. 3, the protection path failure detection unit 506 of the node B detects a failure and notifies the protection control unit 517. Upon receiving the notification, the protection control unit 517 proceeds to step S12.
In 02, a failure notification signal SF (protection side) is transmitted from the transmission unit 0 to the CN. in this case,
At the time of the first failure described above, the 2: 1 optical switches 507, 5
08 is set to the bridge state, the notification signal S
F is transmitted from both directions (the working path direction and the protection path direction) to the CN. This situation is shown by S701 in the sequence chart of FIG.

On the other hand, the CN receives the failure notification SF from the node B in step S1101 of FIG. 2, and determines the occurrence of a failure in step S1108. That is, since the failure notification signal SF from the node B is on the protection side, the protection control unit 513 of the CN determines that the second failure is a failure on the same ring as the first failure (S702). This situation is shown by S702 in the sequence chart of FIG. Then, in step S1109 in FIG. 2, based on the topology information (information on the arrangement of the nodes on the ring) held by the node CN, the second
A and B are affected by the failure
, And sends a switch back notification (Drop sw) to the nodes A and B.

On the other hand, the nodes A and B receive the switch back instruction (Drop sw) in step S1203 in FIG. 3, and switch back the switch in step S1206. That is, the protection control units 517 of the nodes A and B are the receiving system 2: 1 optical switches 509 to 5
12 is cut back to the solid line side. However, only the 2: 1 optical switch of the receiving system switches back, and the 2: 1 optical switches 507 and 508 of the transmitting system do not switch back. This situation is indicated by S703 in the sequence chart of FIG. Then, the node A and the node B communicate with each other in step S12 of FIG.
At 07, a response (ack) is transmitted to the CN, and the process is completed. The CN receives the response (ack) from each node in S1110 in FIG. 2 and completes the process. As a result, as shown in FIG. 6, the nodes A and B can receive the traffic from the path that was originally the working path without any failure.

If the first failure has not occurred in step S1108 in FIG.
Means that a failure has occurred in the direction toward and the RN has transmitted SF to the CN. In that case, step S1111
, The CN becomes a failure detection node and receives the SF
In step S1112, bridge & switch is performed, and in step S1113, a response signal (ack) is transmitted to each node.

On the other hand, in steps S1203 of FIG. 3, the nodes A, B, and C receive a response signal (ac
In the case of k), it means that the current failure is the first failure occurrence, and therefore, in step S1204,
As in the case of the CN that received the response signal, bridge & switc
h, and in step S1205, a response signal (ack)
To the CN.

The ring in which a failure occurs is not limited to the inner ring, and the number of nodes is not limited to four. The first fault occurrence location is not limited to this embodiment as long as it is on the working path.

The network form to which the present invention can be applied is not limited to the ring type. For example, Poin where two nodes are connected by a working path and a protection path
It is applicable to t toPoint type. (A) of FIG.
7 shows a normal state, FIG. 7B shows the state after the occurrence of the first failure, and FIG. 7C shows the state after the occurrence of the second failure. In this case, it is protection control between two nodes,
Since the same control as the protection control between the CN of the embodiment and the node A described above can be applied, the description of the operation is omitted.

[0038]

According to the present invention, the failure detecting unit detects the occurrence of the second failure, the protection control unit receives the detection, sends a notification signal to the other node, and transmits the notification signal to the other node. The protection control unit sends a switch-back notification back to the failure detection node, and the protection processing unit of the failure detection node that has received the notification returns to the receiving unit:
Since one optical switch is switched back, it is possible to provide a protection method capable of restoring traffic even if a plurality of failures occur on the same ring.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a node to which a 1: 1 protection method for a plurality of failures according to the present invention is applied.

FIG. 2 is a flowchart illustrating processing of a protection control unit of a center node CN.

FIG. 3 is a flowchart illustrating processing of a protection control unit of a remote node (RN).

FIG. 4 is a sequence chart showing an operation between nodes when a first failure occurs.

FIG. 5 is a sequence chart showing an operation between nodes when a second failure occurs.

FIG. 6 is a diagram showing a flow of traffic after the occurrence of a second failure.

FIG. 7 shows a point-to-point 1: 1 protection scheme according to the present invention.
It is a figure which shows the flow of the traffic at the time of applying to the network structure of Point1, (a) is a normal time,
(B) shows the state after the occurrence of the first failure, and (c) shows the state after the occurrence of the second failure.

FIG. 8 is a diagram illustrating an example of a network configuration in which a fiber has a ring configuration and a wavelength path has a star configuration.

FIG. 9 is a diagram showing a normal traffic flow.

FIG. 10 is a diagram showing a flow of traffic after the occurrence of a first failure.

FIG. 11 is a diagram showing a flow of traffic after the occurrence of a second failure according to the related art.

FIG. 12 is a sequence chart showing an operation between nodes when a second failure occurs according to the related art.

[Explanation of symbols]

 501 ... OADM (system 0) 502 ... OADM (system 1) 503 ... branch wavelength 504 ... branch wavelength 505 ... failure detection unit 506 ... failure detection units 507 to 512 ... 2: 1 optical switch 513: protection control unit of CN 515: memory 517: protection control unit of RN

Claims (7)

[Claims] A traffic topology is of a star type, a plurality of remote nodes for inserting / branching only unique branch wavelengths, and a wavelength path is established at each branch wavelength between each remote node, and a center of the traffic topology is provided. In a two-fiber ring network in which a working path extends in one direction as viewed from the center node and a protection path extends in a direction opposite to the working path, a first fault on the working path When a failure occurs, the traffic is simultaneously switched to the protection path in both directions, and when a second failure occurs in the same ring as the ring in which the first failure has occurred, one of the switched protection paths is switched back to the working path. Multiplexing optical communication system Tekushon way. 2. In a point-to-point network comprising a working path and a protection path, when a first failure occurs on the working path, traffic is simultaneously switched to the protection path in both directions, and the traffic is switched on the protection path in the opposite direction to the first failure. A 1: 1 protection method for a wavelength-division multiplexed optical communication system, characterized in that when a second failure occurs, one direction of the switching to the protection path is switched back to the working path. 3. A traffic topology having a star topology, wherein a plurality of remote nodes for inserting / branching only unique branch wavelengths, and a wavelength path is established between each remote node at each branch wavelength, and a center of the traffic topology is provided. In a two-fiber ring network in which a working path extends in one direction as viewed from the center node and a protection path extends in a direction opposite to the working path, a first fault on the working path First failure detecting means for detecting traffic, when the first failure detecting means detects a first failure on a working path, means for simultaneously switching traffic to a protection path in both directions; A second fault for detecting a second fault on the same ring as the ring that occurred When the second fault is detected in the same ring as the ring in which the first fault has occurred by the second fault detecting means, one direction of switching to the protection path is set to the working path. A wavelength division multiplexing optical communication system, comprising: means for switching back. 4. A point-to-point network comprising a working path and a protection path, wherein: a first fault detecting means for detecting a first fault on the working path; and Means for switching traffic to a protection path in both directions simultaneously when a first fault is detected in the first fault, means for detecting a second fault on a protection path in a direction opposite to the first fault, and detecting the second fault Means for, when a second fault is detected on a protection path in a direction opposite to that of the first fault, switching one of the protection paths to the working path and switching back to the working path. , Wavelength multiplexing optical communication system. 5. A traffic node comprising a plurality of remote nodes for inserting / branching only unique branch wavelengths, and a center node having a wavelength path between each remote node at each branch wavelength and serving as a central node of a traffic topology. In a two-fiber ring network in which the working path is extended in one direction as viewed from the center node and the protection path is extended in the opposite direction to the working path, a first OADM (Optical Add Dro
p Multiplexer), a second OADM for the protection path, and a first OADM connected to the first OADM and on a working path.
A first failure detecting unit that generates a failure of the first OADM, a first 2: 1 optical switch connected to the first OADM, a second 2: 1 optical switch connected to the second OADM, and the first Third and fourth terminals connected to the output of the fault detector
A 2: 1 optical switch, a second fault detecting unit for detecting that a second fault has occurred on the same ring as the first fault ring, and a connection to an output of the second fault detecting unit. The fifth and sixth 2: 1 optical switches, the first and second fault detectors, and the first, second, third, fourth, fifth and sixth 2: 1 switches And the first failure detection unit performs the first failure detection on the working path.
When the first optical switch is detected as a fault,
State, and the second, third, fourth, fifth and sixth
The 2: 1 optical switch is switched to switch the traffic to the protection path simultaneously in both directions. When the second failure is detected by the second failure detecting means in the same ring as the ring in which the first failure has occurred, the second failure is detected. 3, 4th, 5th
And a protection control unit for switching back to the working path by switching back to the protection path by switching back the sixth 2: 1 optical switch. node. 6. A traffic topology is of a star type, wherein a plurality of remote nodes for inserting / branching only unique branch wavelengths are provided, and a wavelength path is established between each remote node at each branch wavelength. To realize a 1: 1 protection function in a two-fiber ring network in which a working path is extended in one direction as viewed from the center node, and a protection path is extended in the opposite direction to the working path. A program for switching a traffic to a protection path in both directions at the same time when a first failure occurs on a working path, and a second procedure on the same ring as the ring in which the first failure has occurred. Protection in case of failure Computer-readable storage medium storing a program for executing the procedure for returning off direction of which is switched to the scan to the working path, the. 7. In a point-to-point network comprising a working path and a protection path, when a first failure occurs on the working path, a computer switches a traffic to a protection path in both directions at the same time; A computer-readable storage medium storing a program for executing a procedure for switching one direction of switching to the protection path to the working path when a second failure occurs on the protection path.