JP2006311416A - Data transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of a failure in an RPR IF in a certain node on the whole packet ring network even when the failure occurs. <P>SOLUTION: When the failure occurs in the RPR IF9 in the node 1e, the failure is detected in the node 1e and a path to be used is switched from a path 5 in the node to a path 6 for redundancy in the node, the path 6 directly connecting an IF 22a on the high speed side to an IF 22b on the high speed side. As a result, the IF 22a on the high speed side and the IF 22b on the high speed side are connected by the path 6 for redundancy in the node and a signal passing through the node 1e is protected. As a result, since a signal passing through the RPR IF9 maintains the same path as before the occurrence of the failure without receiving RPR switching, influence on a bypass route is suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data transmission system in which a plurality of nodes are connected by an SDH (Synchronous Digital Hierarchy) / SONET (Synchronous Optical Network) transmission line, and more particularly, an RPR (Resilient Packet Ring) ring configured on an SDH / SONET transmission line. Network or L2 switch network.

  In recent years, a technique called RPR has attracted attention as a technique for increasing the availability of a network configured by Ethernet (registered trademark). This RPR is an Ethernet network standardized by IEEE802.17, and is a technology that realizes failure avoidance time within 50 ms. By using this RPR, it is possible to construct a packet ring network having a failure avoidance function similar to SDH / SONET while maintaining the statistical multiplexing effect by packet multiplexing which is an advantage of Ethernet (registered trademark). A network that configures the RPR on the SDH / SONET transmission path is being developed.

  FIG. 8 shows a conventional RPR ring network configured on an SDH / SONET transmission line. As shown in FIG. 8, this conventional PRP ring network is configured by connecting six nodes 32a to 32f in a ring shape.

  Each of the nodes 32 a to 32 f includes a high-speed interface circuit (hereinafter abbreviated as a high-speed IF) 34 a and 34 b and an RPR interface circuit (hereinafter abbreviated as an RPR IF) 35.

  Each of the high-speed IFs 34a and 34b receives the SDH / SONET signal from the adjacent node, terminates the received SDH / SONET signal, and transmits the SDH / SONET signal to be transmitted to the adjacent node. Generate.

  The termination of the SDH / SONET signal here refers to checking the error by reading the header information of the SDH / SONET signal from the high-speed transmission path, and distributing various data stored in the SDH / SONET frame to each path. It means that. The generation of an SDH / SONET signal means that data to be transmitted to an adjacent node is stored in an SDH / SONET frame, added with header information, etc., and transmitted to a high-speed transmission path to the adjacent node. I mean.

  In the storage unit for SDH / SONET frame data transmitted between nodes, data is stored in multiple layers in a box of SDH / SONET format frames. For this reason, the high-speed IFs 34a and 34b distribute the contents of the data stored in the frame by terminating the SDH / SONET signal.

  The RPR IF 35 performs termination processing of the SDH / SONET signal on the SDH / SONET format data from the high-speed IFs 34a and 34b, and then transmits the RPR frame signal mapped to the SDH / SONET signal to each destination path. The RPR frame signal to be transmitted to adjacent nodes is mapped to the SDH / SONET signal.

  Here, consider a case where signals are transmitted and received between the node 32f and the node 32d. When no failure has occurred in any node, the signal from the node 32f is transmitted / received via the node 32e. Therefore, this signal passes through the high speed IFs 34a and 34b and the RPR IF 35 in the node 32e.

  However, in the node 32e, no failure has occurred in the high-speed IFs 34a and 34b, and even when only the RPR IF 35 becomes unusable due to the failure, the signal between the node 32f and the node 32d It becomes impossible to pass. In such a case, RPR switching is performed in the RPR IF in the nodes 32d and 32f, and a route that bypasses the node 32e is selected. As a result, signals between the node 32f and the node 32d are transmitted / received via the nodes 32a, 32b, and 32c.

  However, in such an RPR ring network, signals are transmitted and received between other nodes. For example, signals are transmitted and received between the node 32a and the node 32b. Therefore, since all signals on the same ring select a route that avoids the node 32e where the failure has occurred, traffic may concentrate on the detour and congestion 42 may occur.

  In addition, in a data transmission network configured in a ring shape, when a node failure or a transmission line failure is detected, a failure avoidance method for protecting data by returning traffic flowing through the transmission line to the original route has also been proposed. (For example, refer to Patent Document 1).

However, in such a failure avoidance method, the traffic flowing through the transmission path is in a ring-cut state, and it cannot be denied that the traffic is concentrated and congestion may occur.
International Publication No. 98/11694 Pamphlet

  In the RPR ring network configured on the conventional SDH / SONET transmission path described above, when a failure occurs in the RPR IF of a certain node, the RPR switching is operated in another node to bypass the failed RPR IF. Since the route is selected, there is a problem that congestion occurs on the detour and the bandwidth of the entire ring network cannot be used sufficiently.

  An object of the present invention is to provide a data transmission system capable of reducing the influence of the failure on the entire packet ring network even when a failure occurs in the RPR IF in a certain node.

In order to achieve the above object, a data transmission system of the present invention is a data transmission system in which a plurality of nodes are connected in a ring shape by an SDH / SONET transmission line,
Each of the nodes
A first high-speed interface circuit that receives an SDH / SONET signal from an adjacent first node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent first node When,
Second high-speed interface circuit that receives an SDH / SONET signal from an adjacent second node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent second node When,
Terminate the SDH / SONET signal from the adjacent first node to distribute the RPR frame signal mapped to the SDH / SONET signal for each destination route, and transmit it to the adjacent first node The RPR frame signal for mapping to the SDH / SONET signal is mapped to the SDH / SONET signal by terminating the SDH / SONET signal from the adjacent second node. A second RPR signal processing unit that distributes the RPR frame signal for each destination route and maps an RPR frame signal for transmission to the adjacent second node to an SDH / SONET signal, Inserted into RPR frame signals from the first and second RPR signal processing units Branch, and RPR interface circuit for performing passing process,
With respect to the SDH / SONET signals input from the first and second high-speed interface circuits, an intra-node path connected to the first and second RPR signal processing units or the first and second facing each other An SDH / SONET layer switch that performs switching by selecting any of the intra-node redundancy paths directly connected to the high-speed side interface circuit;
A failure detection unit for detecting occurrence of a failure in the RPR interface circuit;
When the occurrence of a failure is not detected by the failure detection unit, the SDH / SONET layer switch unit is instructed to select a path within the node, and when the occurrence of a failure is detected by the failure detection unit, A switching control unit that instructs the SDH / SONET layer switch unit to select the intra-node redundancy path.

  According to the present invention, in addition to the intra-node path connecting the SDH / SONET high-speed side interface circuit and the RPR interface circuit, the intra-node redundancy path directly connecting the high-speed side IF is provided, and the RPR interface circuit is faulty. If a failure occurs, the failure detection unit detects the failure, and the switching control unit controls the SDH / SONET layer switch unit to select the intra-node redundancy path, thereby preventing the failure generated in the RPR interface circuit. Avoid by only the node that detected As a result, even if a failure occurs in the RPR interface circuit at a certain node, by avoiding this failure only at that node, the signal passing through the RPR interface circuit does not undergo RPR switching, and the same path as before the failure occurs. Since it can be maintained, it is possible to suppress the influence on the detour route.

Further, the SDH / SONET layer switch unit is
A first branching unit that branches the SDH / SONET signal from the first high-speed interface circuit and outputs one of the branched signals to the first RPR signal processing unit;
A second branching unit that branches the SDH / SONET signal from the second high-speed interface circuit and outputs one of the branched signals to the second RPR signal processing unit;
When the switching control unit is instructed to select an intra-node redundancy route, the other signal branched by the first branch unit is selected and output to the second high-speed interface circuit, A first selector that selects a signal from the second RPR signal processing unit and outputs the signal to the second high-speed interface circuit when instructed by the switching control unit to select an intra-node route;
When the switching control unit is instructed to select an intra-node redundancy path, the other signal branched by the second branch unit is selected and output to the first high-speed interface circuit, And a second selector that selects a signal from the first RPR signal processing unit and outputs the selected signal to the first high-speed interface circuit when instructed by the switching control unit to select an intra-node route. You may make it do.

  As described above, according to the present invention, when a failure occurs in the RPR IF in a certain node constituting the ring network, the failure can be avoided in the node. Therefore, the RPR IF in which the failure has occurred can be avoided. It is possible for the signal passing through to maintain the same route as before the occurrence of the failure without undergoing RPR switching. Therefore, it is possible to suppress the influence on other detour routes, and it is possible to obtain an effect that the signal is not concentrated on the detour and the band of the entire ring network can be used effectively.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 shows an RPR ring network of 6 nodes 1a to 1f configured on an SDH / SONET transmission line as a first embodiment of the present invention. In FIG. 1, in addition to the intra-node path 5 that connects the RPR IF 9 and the high-speed IFs 22a and 22b, an intra-node redundancy path 6 that directly connects the high-speed IFs 22a and 22b within the node is set in each of the nodes 1a to 1f. Has been.

  Details of the redundant configuration between the high-speed IFs 22a and 22b in the nodes 1a to 1f shown in FIG. 1 will be described with reference to FIG. As shown in FIG. 2, each of the nodes 1a to 1f includes a high-speed IF 22a and 22b, an RPR IF 9, an SDH / SONET layer switch unit 21, an RPR IF 15, and a switching control unit 16. The SDH / SONET layer switch unit 21 includes branching units 11a and 11b and selectors 12a and 12b. The RPR IF 9 includes RPR signal processing units 10a and 10b.

  Each of the high-speed IF (WEST) 22a and the high-speed IF (EASTT) 22b receives the SDH / SONET signal from the adjacent node, terminates the received SDH / SONET signal, and To generate an SDH / SONET signal for transmission. The high-speed IFs 22a and 22b in this embodiment perform the same operation as the high-speed IFs 34a and 34b in the conventional example shown in FIG.

  The branching units 11a and 11b branch the signals input from the high-speed IFs 22a and 22b, respectively, and output one of the branched signals to the RPR signal processing units 10a and 10b, and the other signal to the selectors 12a and 12b. Output.

  Each of the RPR signal processing units 10a and 10b performs termination processing of SDH / SONET signals from adjacent nodes, extracts RPR frame signals mapped to the SDH / SONET signals, and distributes them for each destination route. The RPR frame signal to be transmitted to the adjacent node is mapped to the SDH / SONET signal.

  The RPR IF 9 performs insertion (add), branch (drop), and passage (through) processing on the RPR frame signals from the RPR signal processing units 10a and 10b. Specifically, in the RPR IF 9, the RPR frame signal addressed to the node is converted into an Ether signal 18 by branching (dropping) by converting the header, and the other node performs other processing (drop) processing. The Ethernet signal 18 addressed to a node is converted into an RPR frame signal and inserted into an SDH / SONET signal transmitted to another node. Further, a signal that should pass through the node is subjected to a passing (through) process in the RPR IF 9.

  The RPR IF 9 reads the header information of the RPR frame signal and determines whether the received RPR frame signal is branched at the node or transmitted to the adjacent node. The RPR frame signal from the RPR signal processing unit 10a determined to be passed through in the RPR IF 9 is stored again in the SDH / SONET format frame by the RPR signal processing unit 10b (this processing is performed at the end of the RPR frame). SDH / SONET frame generation), and is transmitted to the selector 12b. Then, the frame input to the high-speed IF 22b from the selector 12b is transmitted again to the adjacent node stored as the SDH / SONET frame.

  The RPR IF 9 mainly reads the header information of the RPR frame signal or the ether signal 18 received from the RPR signal processing units 10a and 10b and performs switching of the received frame signal. Avoidance operation (RPR switching) is also performed. Information necessary for performing this failure operation is included in the header portion of the RPR frame. The RPR IF 9 also reads this failure information at the time of switching, and determines to which of the data is distributed. When the RPR IF 9 detects a failure, the failure information is written in the RPR header.

  The RPR IF monitoring unit 15 monitors whether a failure has occurred in the RPR IF 9 by monitoring the signal notified from the RPR IF 9 and the mounting state of the RPR IF 9, and notifies the switching control unit 16 of the monitoring result. Notification is made as a signal 19. That is, the RPR IF monitoring unit 15 functions as a failure detection unit for detecting the occurrence of a failure in the RPR IF 9.

  The switching control unit 16 receives the alarm signal 19 from the RPR IF monitoring unit 15 and outputs a switching signal 20 to control the selectors 12a and 12b. Specifically, the switching control unit 16 instructs the SDH / SONET layer switch unit 21 to select the intra-node route when the occurrence of a failure is not detected by the RPR IF monitoring unit 15, and the RPR IF monitoring When the occurrence of a failure is detected by the unit 15, the SDH / SONET layer switch unit 21 is instructed to select an intra-node redundancy route.

  The SDH / SONET layer switch unit 21 receives an SDH / SONET signal input from the high-speed side interface circuits 22a and 22b, an intra-node path connected to the RPR signal processing units 10a and 10b, or an opposing high-speed side interface circuit 22a, Switching is performed by selecting one of the intra-node redundancy paths directly connected to 22b.

  Next, the operation of the data transmission system of this embodiment will be described with reference to the drawings. In the following description, a case where signals are transmitted and received between the node 1f and the node 1d will be described.

  First, an outline of the operation of the data transmission system of this embodiment will be described.

  When no failure has occurred in the ring network shown in FIG. 1, as shown in FIG. 3, signals transmitted and received between the node 1f and the node 1d are routed through the route 24, the node 1e, and the route 23. Sent and received. In the node 1e, the high-speed side IF 22a, the intra-node path 5, the RPR IF 9, and the high-speed side IF 22b are routed. Here, as shown in FIG. 4, when a failure occurs in the RPR IF 9 of the node 1e and signal passing processing becomes impossible, this failure is detected in the node 1e, and the route used is within the node. The path 5 is switched to the intra-node redundancy path 6. Therefore, even if a failure occurs in the RPR IF 9, the connection between the path 24 and the path 23 is maintained by the intra-node redundancy path 6, and the signal passing through the node 1e is protected.

  Next, the detailed operation of the data transmission system of this embodiment will be described. Here, an example of switching the path of a signal that is input from the high speed IF (WEST) 22a, passes through the RPR IF 9, and is output to the high speed IF (EAST) 22b will be described.

  Referring to FIG. 5, the switching operation of the SDH / SONET layer switch unit 21 when the RPR IF 9 is normal is shown.

  The signal input from the high-speed IF (WEST) 22a is branched by the branching unit 11a and output to the selector 12b and the RPR signal processing unit 10a. A signal input to the RPR IF 9 via the RPR signal processing unit 10a is subjected to a passing process in the RPR IF 9, and is output from the RPR signal processing unit 10b to the selector 12b. Here, since no failure has occurred in the RPR IF 9, the switching signal 20 is not output from the switching control unit 16, and the selector 12b selects the signal input from the RPR signal processing unit 10b and selects the high-speed IF (EAST) Output to 22b. Similarly, a signal input from the high-speed IF (EAST) 22b is output to the high-speed IF (WEST) 22a via the branching unit 11b, the RPR signal processing unit 10b, the RPR signal processing unit 10a, and the selector 12a. .

  Next, the switching operation of the SDH / SONET layer switch unit 21 when a failure occurs in the RPR IF 9 will be described with reference to FIG.

  When a failure 39 occurs in the RPR IF 9, the occurrence of this failure is detected by the RPR IF monitoring unit 15. Then, the RPR IF monitoring unit 15 outputs an alarm signal 19 to the switching control unit 16. Then, the switching control unit 16 outputs a switching signal 20 to the selectors 12a and 12b. Upon receiving this switching signal 20, the selector 12a performs switching so as to select the signal input from the branching unit 11a and output it to the high-speed IF (EAST) 22b. Thus, the signal input from the high-speed IF (WEST) 22a can pass to the high-speed IF (EAST) 22b without passing through the RPR IF 9.

  In the above operation, the same processing is performed for a signal passing from the high speed side IF (EAST) 22b to the high speed side IF (WEST) 22b.

  In the data transmission system according to the present embodiment, in the RPR ring network on the SDH / SONET transmission path, when a failure occurs in one of the RPR interfaces (RPR IF) constituting the ring, the failure is detected and the SDH / SONET layer switch By bypassing the RPR IF in which the failure has occurred, the signal passing through the RPR IF in which the failure has occurred is protected.

  As shown in FIG. 4, according to the data transmission system of the present embodiment, in the node directly connecting the high-speed IFs 22a and 22b in addition to the intra-node path 5 connecting the SDH / SONET high-speed IFs 22a and 22b and the RPR IF9. The redundant path 6 is provided, and when a failure occurs in the RPR IF 9, this is detected and the intra-node redundant path 6 is selected. Therefore, when a failure occurs in the RPR IF 9 of a certain node, the failure can be avoided in the node where the failure has occurred. As a result, the signal passing through the failed RPR IF4 can maintain the same route as before the failure without undergoing RPR switching, and thus the influence on the detour route can be suppressed.

(Second Embodiment)
Next, a data transmission system according to a second embodiment of this invention will be described.

  The data transmission system according to the first embodiment is a case where the present invention is applied to an RPR ring network configured by nodes using an RPR interface, but the data according to the second embodiment of the present invention. The transmission system is a case where the present invention is applied to a network system configured by nodes using an interface having an L (layer) 2 switching function.

  In the present embodiment, when switching an existing Ethernet (registered trademark) frame, the L2 switch reads an Ethernet frame header and transmits the frame to which path, that is, branches at this node, or passes through this node. It is a switch for deciding whether to do.

  The configuration of the data transmission system of this embodiment is shown in FIG. In FIG. 7, there are L2 switch IFs 28a, 28b, and 28c in three nodes 25b, 25c, and 25d existing in the SDH / SONET transmission line network, which are respectively connected by the SDH / SONET transmission line. Since there is a signal passing through the L2 switch IF 28b at the node 25c, the intra-node redundancy path 30 is set.

  The operation of each node in the data transmission system of the present embodiment is the same as that in the block diagram shown in FIG. 2 in which all the RPR frame signal parts are replaced with Ethernet signals, and thus the description thereof is omitted. However, in the block diagram shown in FIG. 2, the RPR IF 9 converts the RPR frame into the Ethernet frame, but the L2 switch IF does not require this conversion process.

  The specific circuit configuration for realizing the switching between the intra-node redundant path 30 and the intra-node path 29b is the same as the configuration of the SDH / SONET layer switch unit 21 in the first embodiment shown in FIG. A similar configuration can be used. Therefore, detailed description thereof is omitted.

  Next, the operation of the data transmission system of this embodiment will be described with reference to the drawings.

  When the network is normal, a signal connecting the L2 switch IF 28a and the L2 switch IF 28c passes through the high-speed IFs 27a and 27b, the intra-node path 29b, and the L2 switch IF 28b in the node 25c. Here, when the fault 40 occurs in the L2 switch IF 28b, the above-described path switching (SDH / SONET layer switch) in the node operates, and the signal passing through the node 25c passes through the intra-node redundancy path 30. To do. As a result, it is possible to prevent all signals passing through the node 25c from being blocked. As described above, according to the data transmission system of this embodiment, a signal passing through a failed interface in a layer 2 network that does not have a redundant configuration can be protected by SDH / SONET switching.

It is a figure which shows the structure of the data transmission system of the 1st Embodiment of this invention. It is a figure for demonstrating the detail of the redundant structure in each node 1a-1f in FIG. It is a figure for demonstrating operation | movement when the failure has not generate | occur | produced in the data transmission system of the 1st Embodiment of this invention. It is a figure for demonstrating operation | movement when a failure generate | occur | produces in RPR IF9 in the node 1e in the data transmission system of the 1st Embodiment of this invention. 6 is a diagram for explaining a switching operation of the SDH / SONET layer switch unit 21 when the RPR IF 9 is normal. FIG. 7 is a diagram for explaining a switching operation of the SDH / SONET layer switch unit 21 when a failure occurs in the RPR IF 9. FIG. It is a figure which shows the structure of the data transmission system of the 2nd Embodiment of this invention. It is a figure which shows the structure of the conventional RPR ring network comprised on the SDH / SONET transmission line.

Explanation of symbols

1a to 1f node 5 intra-node path 6 intra-node redundancy path 9 RPR IF (interface)
10a RPR signal processor (WEST side)
10b RPR signal processor (EAST side)
11a, 11b Branch unit 12a, 12b Selector 15 RPR IF unit 16 Switching control unit 17a, 17b SDH / SONET signal 18 Ether signal 19 Alarm signal 20 Switching signal 21 SDH / SONET layer switch unit 22a High-speed side IF (WEST)
22b High-speed IF (EAST)
23, 24 path 25a-25d node 27a, 27b high speed side IF
28a-28c L2 switch IF
29a to 29c Intra-node path 30 Intra-node redundancy path 39, 40 Failure 42 Congestion

Claims (4)

A data transmission system in which a plurality of nodes are connected in a ring shape by an SDH / SONET transmission line,
Each of the nodes
A first high-speed interface circuit that receives an SDH / SONET signal from an adjacent first node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent first node When,
Second high-speed interface circuit that receives an SDH / SONET signal from an adjacent second node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent second node When,
Terminate the SDH / SONET signal from the adjacent first node to distribute the RPR frame signal mapped to the SDH / SONET signal for each destination route, and transmit it to the adjacent first node The RPR frame signal for mapping to the SDH / SONET signal is mapped to the SDH / SONET signal by terminating the SDH / SONET signal from the adjacent second node. A second RPR signal processing unit that distributes the RPR frame signal for each destination route and maps an RPR frame signal for transmission to the adjacent second node to an SDH / SONET signal, Inserted into RPR frame signals from the first and second RPR signal processing units Branch, and RPR interface circuit for performing passing process,
With respect to the SDH / SONET signals input from the first and second high-speed interface circuits, an intra-node path connected to the first and second RPR signal processing units or the first and second facing each other An SDH / SONET layer switch that performs switching by selecting any of the intra-node redundancy paths directly connected to the high-speed side interface circuit;
A failure detection unit for detecting occurrence of a failure in the RPR interface circuit;
When the occurrence of a failure is not detected by the failure detection unit, the SDH / SONET layer switch unit is instructed to select a path within the node, and when the occurrence of a failure is detected by the failure detection unit, A switching control unit that instructs the SDH / SONET layer switch unit to select the intra-node redundancy path. The SDH / SONET layer switch unit is
A first branching unit that branches the SDH / SONET signal from the first high-speed interface circuit and outputs one of the branched signals to the first RPR signal processing unit;
A second branching unit that branches the SDH / SONET signal from the second high-speed interface circuit and outputs one of the branched signals to the second RPR signal processing unit;
When the switching control unit is instructed to select an intra-node redundancy route, the other signal branched by the first branch unit is selected and output to the second high-speed interface circuit, A first selector that selects a signal from the second RPR signal processing unit and outputs the signal to the second high-speed interface circuit when instructed by the switching control unit to select an intra-node route;
When the switching control unit is instructed to select an intra-node redundancy path, the other signal branched by the second branch unit is selected and output to the first high-speed interface circuit, A second selector that selects a signal from the first RPR signal processing unit and outputs the selected signal to the first high-speed interface circuit when instructed by the switching control unit to select a path within the node;
The data transmission system according to claim 1, comprising: A data transmission system in which a plurality of nodes are connected by an SDH / SONET transmission line,
At least one of each node is
A first high-speed interface circuit that receives an SDH / SONET signal from an adjacent first node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent first node When,
Second high-speed interface circuit that receives an SDH / SONET signal from an adjacent second node, performs termination processing, and generates an SDH / SONET signal for transmission to the adjacent second node When,
Terminate the SDH / SONET signal from the adjacent first node to distribute the frame signal mapped to the SDH / SONET signal for each destination route and transmit it to the adjacent first node A first signal processing unit that maps a frame signal for the SDH / SONET signal to the SDH / SONET signal, and a frame that is mapped to the SDH / SONET signal by performing termination processing of the SDH / SONET signal from the adjacent second node A second signal processing unit that distributes a signal for each destination route, and maps a frame signal for transmission to the adjacent second node to an SDH / SONET signal, the first and second signals Layer 2 switch interface that performs insertion, branching, and passage processing on the frame signal from the processing unit And vinegar circuit,
For the SDH / SONET signal input from the first and second high-speed interface circuits, an intra-node path connected to the first and second signal processing units or the first and second high-speeds facing each other An SDH / SONET layer switch that performs switching by selecting any of the intra-node redundancy paths directly connected to the side interface circuit;
A fault detection unit for detecting the occurrence of a fault in the interface circuit;
When the occurrence of a failure is not detected by the failure detection unit, the SDH / SONET layer switch unit is instructed to select a path within the node, and when the occurrence of a failure is detected by the failure detection unit, A switching control unit that instructs the SDH / SONET layer switch unit to select the intra-node redundancy path. The SDH / SONET layer switch unit is
A first branching unit that branches the SDH / SONET signal from the first high-speed interface circuit and outputs one of the branched signals to the first signal processing unit;
A second branching unit that branches the SDH / SONET signal from the second high-speed interface circuit and outputs one of the branched signals to the second signal processing unit;
When the switching control unit is instructed to select an intra-node redundancy route, the other signal branched by the first branch unit is selected and output to the second high-speed interface circuit, A first selector that selects a signal from the second signal processing unit and outputs it to the second high-speed interface circuit when instructed by the switching control unit to select an intra-node route;
When the switching control unit is instructed to select an intra-node redundancy path, the other signal branched by the second branch unit is selected and output to the first high-speed interface circuit, A second selector that selects a signal from the first RPR signal processing unit and outputs the selected signal to the first high-speed interface circuit when instructed by the switching control unit to select a path within the node;
The data transmission system according to claim 3, comprising:

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